DESCRIPTION
Title of Invention
METHOD FOR PRODUCING MOLD FOR TRANSFERRING FINE PATTERN,
METHOD FOR PRODUCING SUBSTRATE HAVING UNEVEN STRUCTURE USING
SAME, AND METHOD FOR PRODUCING ORGANIC EL ELEMENT HAVING SAID
SUBSTRATE HAVING UNEVEN STRUCTURE
TECHNICAL FIELD
[0001] The present invention relates to a method for producing a mold for transfening a
minute (fine) pattern usable for nano-imprinting, etc., a method for producing a substrate
having a concave-convex structure (concavity and convexity structure, uneven or irregular
structure) using the mold, a method for producing an organic electro-luminescent (EL)
element provided with the substrate having the concave-convex structure, a mold for
transfening a fine pattern, a substrate having a concave-convex structure, and an organic
EL element which are obtained by using one of the producing methods.
BACKGROUND ART
I00021 The lithography method is known as a method for forming a fine pattern such as a
semiconductor integrated circuit. The resolution of a pattern formed by the lithography
method depends on the wavelength of a light source, the numerical aperture of an optical
system, etc., and a shorter wavelength light source is desired so as to respond to the
demand for miniaturized devices in the recent years. Any short wavelength light source is,
however, expensive and is not easily developed, and any optical material allowing such
short wavelength light passing therethrough needs to be developed, as well. Further, a
large sized optical element is required for producing a pattern with a large area by means
of the conventional lithography method, which is difficult both technically and
economically. Therefore, a new method for forming a desired pattern having a large area
has been considered.
[0003] The nano-imprinting method is known as a method for forming a fine pattern
without using any conventional lithography apparatus. The nano-imprinting method is a
2
technique capable of transferring a pattern in nanometer order by sandwiching a resin
between a mold and a substrate, and basically is composed of the following four steps of:
(i) coating with a resin layer (application of a resin layer), (ii) pressing with the mold, (iii)
transferring of the pattern and (iv) releasing of the mold (mold-releasing). Thus, the
nano-imprint method is excellent in that the nano-sized processing can be realized with
such a simple process. Further, in the nano-imprint method, devises or apparatuses used
therefor are simple, the processing can be performed for a large area as well as a high
throughput can be expected. Accordingly, the nano-imprint method is expected to be
practiced not only in the field of semiconductor device but also in many fields such as
storage media, optical members, biochips, etc.
[0004] In the nano-imprint method as described above, however, a mold for transferring a
pattern having a line width of several tens of nanometers (nm) needs to be formed basically
by exposing a resist on a silicon substrate and developing the resist to form a resist pattern
(a pattern of a resist), with a lithography apparatus. Further, an electric current seed layer
(current seed layer) made of a metal is formed on the resist pattern for performing
electroforming (electroplating) of the mold by using the obtained resist pattern. However,
in a case that the pattern fineness is not more than 100 nm, the coating performance
(coatability or coverage) of the current seed layer formed on the pattern by sputtering is
lowered, which in turn causes such a state that the film thickness (thickness) of the
obtained current seed layer is different or non-uniform among an upper portion, a side wall
portion and a bottom portion of the resist pattern (the bottom portion being a
substrate-exposure portion in which the substrate is exposed in a recessed portion in the
pattern, namely in a trench). In particular, the formation of the current seed layer is
progressed preferentially in the upper portion of the resist pattern, thereby causing such a
problem that the opening of the trench is constricted or narrowed. Consequently, in a case
that holes or trenches and ridges are formed on the substrate by using the resist layer, there
is such a problem that the metal of the current seed layer is hardly deposited in the bottom
portions of the holes or trenches, and that any overhang is generated at the upper portions
of the ridges of the resist layer. When any stacked body with such a current seed layer is
subjected to the electroforming, an electroplating film is joined at a portion above the hole
or trench due to the overhang, leaving a void inside the trench. As a result, a mold
obtained by the electroforming has low mechanical strength, which in turn causes such a
problem including defect exemplified by any deformation of the mold, deficit (chipped)
3
pattern, etc.
[0005] In order to solve the above problem, Patent Literature 1 discloses a method for
producing a mold for nano-imprint including the steps of:
forming a resist layer having a concave-convex pattern, which is composed of
concave portions and convex portions (concavities and convexities), on a substrate having
a conductive surface and causing the conductive surface to be exposed at the concave
portions of the concave-convex pattern of the resist layer;
performing electroforming on the conductive surface exposed at the concave
portions of the concave-convex pattern of the resist layer to form a electroforming film
having a thickness greater than a thickness of the resist layer; and
removing the substrate having the conductive surface and the resist layer.
Since this method is capable of growing the electroforming film in unidirectional
manner upwardly from the conductive surface at the bottom portion of the resist pattern
without using a current seed layer, it is considered that any void is not present inside the
mold for nano-imprint. Even with this method, however, the mold used in the
nano-imprint method should be made with the lithography method, same as before.
[CITATION LIST]
[PATENT LITERATURE]
[0006]
PATENT LITERATURE 1 : Japanese Patent Application Laid-open No.
2010-017865
PATENT LITERATURE 2: PCT International Publication No.
W02011/007878Al
PATENT LITERATURE 3: Japanese Patent Application Laid-open No.
2010-056256
SUMMARY OF INVENTION
Problem to be Solved by the Invention:
[0007] The inventors of the present invention disclose the following method in PATENT
LITERATURE 2. Namely, a block copolymer solution containing a block copolymer
satisfying a predetermined condition and a solvent is applied on a base member (the base
4
member is coated with the block copolymer solution), and drying is performed for the
applied block copolymer solution to form a micro phase separation structure of the block
copolymer, thereby obtaining a master block (mold) in which a fine (minute) and irregular
concave-convex pattern is formed. According to this method, it is possible to obtain the
master block usable for the nano-imprint and the like by using a self-organizing
phenomenon of the block copolymer, without using the lithography method. A mixture of
a silicone-based polymer and a curing agent is dropped onto the obtained master block and
then cured to obtain a transferred pattern. Then, a glass substrate coated with a curable
resin is pressed to (against) the transferred pattern and the curable resin is cured by
irradiation with an ultraviolet light. In this way, a diffraction grating in which the
transferred pattern is duplicated is manufactured. It has been confirmed that an organic
EL diode (organic light-emitting diode) obtained by stacking a transparent electrode, an
organic layer, and a metal electrode on the diEaction grating has sufficiently high light
emission efficiency, sufficiently high level of external extraction efficiency, as well as
sufficiently low wavelength-dependence of light emission, sufficiently low directivity of
light emission, and sufficiently high power efficiency.
[0008] In this method, however, a step is required for removing one of polymers
composing the block copolymer with the etching process, so as to obtain the
concave-convex pattern after the formation of the micro phase separation structure of the I
block copolymer. Due to this removing step, one of the polymers is removed as portions
at each of which the base member is exposed and the other of the polymers is remained to
form the convex portions. However, the remaining convex portions have small area of
contact with the surface of the base member, and thus easily drop off or detach from the
surface of the base member. Further, there is a case that any foreign matter adheres to the
base member and/or the surfaces of the convex portions accompanying with the etching
process, which in turn presents a possibility that the master block or a diffraction grating
produced from the master block via a transfer process might be contaminated. If these
cases happened in a mass production process of diffraction gratings, there is a fear that the
throughput might be lowered in the mass production process of diffraction gratings or of
organic EL elements produced by using the diffraction gratings. Therefore, there is a
demand to further advance the method for producing the diffraction grating achievable in
the preceding patent application by the inventors of the present invention (Patent Literature
2), for the purpose of providing a production method further suitable for mass production
5
of products such as organic EL elements, etc.
[0009] Patent Literature 3 disclose forming a columnar-shaped micro domain structure,
lamella-type micro domain structure, etc., by phase-separating a high polymer layer
including a block copolymer of which molecular weight is relatively low. This method,
however, removes one of the polymers by the etching, etc., for the patterning purpose.
[0010] In view of the above situation, an object of the present invention is to provide a
method for producing a mold for transfening a fine pattern suitable for mass-producing a
substrate having a concave-convex structure such as a diffraction grating usable for a
general-purpose item such as an organic EL element, a method for producing a substrate
having a concave-convex structure by using the obtained mold, and a method for
producing an organic EL element using the substrate having such concave-convex structure.
Another object of the present invention is to produce a mold for transferring a fine pattern,
a substrate having a concave-convex structure, and an organic EL element with a high
throughput by using one of these producing methods.
Solution to the Problem:
[0011] According to the present invention, there is provided a method for producing a
mold for transferring a fine pattern, the method including:
a step of coating a surface of a base member with a solution containing a block
copolymer and polyalkylene oxide, the block copolymer being composed of at least first
and second polymer segments;
a solvent phase-separation step of phase-separating the block copolymer contained
in the solution, with which the surface of the base member is coated, under a presence of
vapor of an organic solvent so as to obtain a block copolymer film of the block copolymer,
the block copolymer film having a concave-convex structure on a surface thereof and a
horizontal cylinder structure in an interior thereof;
a step of forming a seed layer on the concave-convex structure of the block
copolymer film;
a step of stacking a metal layer on the seed layer by electroforming; and
a step of releasing the base member, on which the concave-convex structure is
formed, from the metal layer.
[0012] In the method for producing the mold of the present invention, a volume ratio
between the first and second polymer segments in the block copolymer is preferably in a
6
range of 4:6 to 6:4, in view of generating the horizontal cylinder structure. Further, a
content amount of the polyalkylene oxide is preferably in a range of 5 parts by mass to 70
parts by mass relative to 100 parts by mass of the block copolymer, in view of obtaining
sufficient height (groove depth) of the concave-convex structure. Furthermore, number
average molecular weight of the block copolymer is preferably not less than 500,000.
Since a wave-like (wave-like shaped) concave-convex structure can be obtained by the
solvent phase-separation step in the producing method of the present invention, any etching
process is not necessary after the solvent phase-separation process (step).
[0013] In the method for producing the mold of the present invention, the first polymer
segment composing the block copolymer may be polystyrene; the second polymer segment
composing the block copolymer may be polymethyl methacrylate. Further, the organic
solvent may be one selected from the group consisting of chloroform, acetone,
dichloromethane, and a mixed solvent of carbon bisulfide and acetone. Further, a time for
phase-separating the block copolymer under the presence of the vapor of the organic
solvent may be in a range of 6 hours to 168 hours.
[0014] In the method for producing the mold of the present invention, even in a case that
the first or second polymer segment is formed to have a one-tiered (one-stage) structure or
a two-tiered (two-stage) structure in the horizontal cylinder structure, the concave-convex
structure appears on the surface. As the mold for the substrate having the
concave-convex structure such as a diffraction grating, it is desirable that an average value
of depth distribution of concavities and convexities of the concave-convex structure is in a
range of 20 nm to 200 nm, preferably in a range of 30 nm to 150 nm; and that standard
deviation of depth of the concavities and convexities is in a range of 10 nm to 100 nm,
more preferably in a range of 15 nm to 75 nm.
100151 In the method for producing the mold of the present invention, it is preferable that
a primer layer is formed on the surface of the base member before coating the surface of
the base member with the solution containing the block copolymer, which is composed of
at least the first and second polymer segments, and the polyalkylene oxide. Further,
molecular weight distribution (MwlMn) of the block copolymer is preferably not more
than 1.5, and difference in solubility parameter between the first and second polymer
segments is in a range of 0.1 (callcm3)'" to 10 (call~m~)"~.
100161 According to a second aspect of the present invention, there is provided a method
for producing a diffraction grating, the method including:
7
pressing a mold obtained by the above method for producing the mold onto
(against) a substrate coated with a concavity-convexity forming material and curing the
concavity-convexity forming material, and removing the mold from the substrate so as to
form a diffraction grating having a concave-convex structure on the substrate.
[0017] According to a third aspect of the present invention, there is provided a method for
producing a diffraction' grating, the method including:
pressing a mold obtained by the above method for producing the mold onto a
substrate coated with a concavity-convexity formingmaterial, curing the
concavity-convexity forming material, and removing the mold from the substrate so as to
form a structure having a concave-convex structure on the substrate; and
pressing the structure onto another substrate coated with a sol-gel material, curing
the sol-gel material, and removing the stmcture fiom the another substrate so as to form a
diffraction grating having a concave-convex structure formed of the sol-gel material.
(00181 According to a fourth aspect of the present invention, there is provided a method
for producing an organic EL element, the method including: stacking a transparent
electrode, an organic layer and a metal electrode successively on a concave-convex
structure of a diffraction grating, produced by the above method of producing the
difkaction grating, so as to form the organic EL element.
[0019] According to a fifth aspect of the present invention, there is provided a mold for
transfemng a fine pattern produced by the above method for producing the mold.
[0020] According to a sixth aspect of the present invention, there is provided a diffkaction
grating which is produced by the above method for producing the diffraction grating and
which has a concave-convex structure on a surface thereof. The diffraction grating has an
average pitch of concavities and convexities of the concave-convex structure which is
preferably in a range of 100 nm to 1,500 nm, more preferably in a range of 200 nm to
1,200 nm. Further, a cross-sectional shape of the concave-convex structure is preferably
wave-like; and that in a case of obtaining a Fourier-transformed image by performing a
two-dimensional fast Fourier-transform processing on a concavity and convexity analysis
image obtained by analyzing a planer shape of the concave-convex structure with an
atomic force microscope, the Fourier-transformed image preferably shows an annular
pattern substantially centered at an origin at which an absolute value of wavenumber is 0
pm-', and the annular pattern is present within a region where the absolute value of
wavenumber is within a range of not more than 10 pm-'. Furthermore, kurtosis of a
8
cross-sectional shape of the concave-convex structure of the diffraction grating is
preferably not less than -1.2, more preferably in a range of -1.2 to 1.2.
[0021] According to a seventh aspect of the present invention, there is provided an
organic EL element produced by the above method for producing the organic EL element.
I00221 According to an eighth aspect of the present invention, there is provided a method
for producing a substrate having a concave-convex structure, the method including:
pressing a mold obtained by the above method for producing the mold onto a substrate
coated with a concavity-convexity forming material, curing the concavity-convexity
forming material, and removing the mold from the substrate so as to form the substrate
having a concave-convex structure.
100231 According to a ninth aspect of the present invention, there is provided a method
for producing a substrate having a concave-convex structure, the method including:
pressing a mold obtained by the above method for producing the mold onto a
substrate coated with a concavity-convexity forming material, curing the
concavity-convexity forming material, and removing the mold from the substrate so as to
form a structure having a concave-convex structure on the substrate; and
pressing the structure onto another substrate coated with a sol-gel material, curing
the sol-gel material, and removing the structure from the another substrate so as to form the
a substrate having a concave-convex structure formed of the sol-gel material.
[0024] According to a tenth aspect of the present invention, there is provided a substrate
having a concave-convex structure on a surface thereof and produced by the above method
of producing the substrate. The substrate having the concave-convex structure has an
average pitch of concavities and convexities of the concave-convex structure which is
preferably in a range of 100 nm to 1,500 nm, more preferably in a range of 200 nm to
1.200 nm.
Effects of Invention:
[0025] According to the method for producing the mold of the present invention, a block
copolymer film of which surface has a smooth and wave-like concave-convex structure
and of which cross-sectional structure has a horizontal cylinder structure can be obtained
by phase-separating the solution, which contains the block copolymer, with the organic
solvent so as to cause the self-organization of the block copolymer. Thus, the etching
step which has been required for forming the concave-convex structure becomes
9
unnecessary, thereby realizing a simplified production process and lowering the possibility
that any dirt (stain, soil, dust) and/or any foreign matter might adhere to the mold through
the production process, as well. The surface property of a metal layer of the obtained
mold is such that smooth concavities and convexities are distributed substantially
uniformly, and that a resin is suppressed from remaining on a side of the mold when the
block copolymer and the base member are released (peeled off) from the mold, thereby
enhancing the releasing property (peeling property) of the mold. With this, any pattem
defect is prevented from generating. Further, even in a case that the molecular weight of
the block copolymer is as high as 500,000 or more, it is possible to form a mold having a
desired concave-convex pattem in an ensured manner. Therefore, by using a mold
obtained by the present invention, a substrate having the concave-convex structure, such as
a diffraction grating diffracting a light of the visible region without any wavelength
dependency and with low directivity, can be produced with a relatively low cost and with a
high throughput.
BRIEF DESCRIPTION OF DRAWINGS
[0026]
Fig. 1(A) to 1(F) is a view conceptually showing the steps in a mold-producing
method of the present invention.
Fig. 2(A) to 2(E) is a view conceptually showing the steps for producing a
diffraction grating using a mold obtained by the mold-producing method of the present
invention.
Fig. 3 is a flowchart showing the steps in the mold-producing method of the
present invention.
Fig. 4 is a conceptual view of a roll processing apparatus for producing a
film-shaped substrate as a mold to be used in a diffraction-grating producing method.
Fig. 5 is a flowchart showing steps for producing a concave-convex substrate,
which has concavities and convexities made of a sol-gel material, by using the film-shaped
substrate as the mold.
Fig. 6 is a conceptual view for explaining a roll processing for performing transfer
on the sol-gel material by using the film-shaped substrate as the mold.
Fig. 7 is a conceptual view showing a stacked structure of an organic EL element
by using a diffraction grating obtained by the diffraction-grating producing method of the
10
present invention.
Fig. 8A is a photograph of the cross section of a thin film, obtained by Example 1,
after solvent annealing observed by a transmission electron microscope, showing a
two-tiered (two-stage) horizontal cylinder structure.
Fig. 8B is an enlarged photograph of the photograph of Fig. 8A.
Fig. 8C is a photograph of the cross section of the thin film, obtained by Example
1 after solvent annealing, observed by the transmission electron microscope, showing a
one-tiered (one-stage) horizontal cylinder structure.
Fig. 8D is an enlarged photograph of the photograph of Fig. 8C.
Fig. 9A is a photograph showing a concavity and convexity analysis image, taken
by an atomic force microscope, of a surface of a concave-convex structure of the thin film
obtained in Example 1.
Fig. 9B is a photograph showing a concavity and convexity analysis image, taken
by the atomic force microscope, of the cross section at a portion in the vicinity of the
surface of the concave-convex structure of the thin film shown in Fig. 9A.
Fig. 9C is a photograph showing a Fourier-transformed image obtained based on
the concavity and convexity analysis images shown in Figs. 9A and 9B.
Fig. 10A is a photograph showing a concavity and convexity analysis image, taken
by an atomic force microscope, of a surface of a concave-convex structure of a thin film
obtained in Comparative Example 1.
Fig. 10B is a photograph showing a concavity and convexity analysis image, taken
by the atomic force microscope, of the cross section at a portion in the vicinity of the
surface of the concave-convex structure of the thin film shown in Fig. 10A.
Fig. 10C is a photograph showing a Fourier-transformed image obtained based on
the concavity and convexity analysis images shown in Figs. 10A and 10B.
Fig. 11 is a graph showing the change in electric current efficiency with respect to
the luminance (brightness) of an organic EL element produced in Example 7.
Fig. 12 is a graph showing the change in electric power efficiency with respect to
the luminance of the organic EL element produced in Example 7.
DESCRIPTION OF EMBODIMENTS
[0027] In the following, a preferred embodiment of the present invention will be
11
described in detail with reference to the drawings.
[0028] At first, an explanation will be given about a mold-producing method for
producing a mold suitable for producing a substrate having a concave-convex structure
such as a diffraction grating usable for an organic EL element. As shown in a flowchart
of Fig. 3, the mold-producing method mainly includes a step for preparing a solution of
block copolymer (block copolymer solution), a step of coating a base member with the
block copolymer solution (applying the block copolymer solution), a drying step, a solvent
annealing step, a step of forming a seed layer, an electroforming step and a releasing step
(peeling step). In the following, an explanation will be given about the respective steps of
the mold-producing method and steps following the mold-producing method, also referring
to the conceptual views shown in Figs. 1 and 2. Note that although the following
explanation is given about a diffraction grating substrate as an example of a substrate
having concave-convex structure, a substrate having the concave-convex structure
according to the present invention is not limited to the optical substrate such as the
diffraction grating substrate and is applicable also to a variety of substrates having various
applications, as will be described later on.
100291
[Preparation step of block copolymer solution]
The block copolymer used for present invention includes at least a first polymer
segment made of a first homopolymer and a second polymer segment made of a second
homopolymer different from the fist homopolymer. The second homopolymer desirably
has a solubilityparameter which is higher than a solubility parameter of the first
3 112 homopolymer by 0.1 (callcm ) to 10 (callcm3 ) 112 . In a case that the difference in the
solubility parameter between the first and second homopolymers is less than 0.1
(callcm3 )1 12 , i.t i.s difficult to form a regular micro phase separation structure of the block
copolymer. In a case that the difference exceeds 10 (callcm3 )1 12 ,i .t 1. s difficult to prepare a
uniform solution of the block copolymer.
[0030] Examples of monomers serving as raw materials of homopolymers usable as the
first homopolymer and second homopolymer include styrene, methylstyrene, propylstyrene,
butylstyrene, hexylstyrene, octylstyrene, methoxystyrene, ethylene, propylene, butene,
hexene, acrylonitrile, acrylamide, methyl methacrylate, ethyl methacrylate, propyl
methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, methyl acrylate,
ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, methacrylic
12
acid, acrylic acid, hydroxyethyl methacrylate, hydroxyethyl acrylate, ethylene oxide,
propylene oxide, dimethylsiloxane, lactic acid, vinylpyridine, hydroxystyrene,
styrenesulfonate, isoprene, butadiene, E-caprolactone, isopropylacrylamide, vinyl chloride,
ethylene terephthalate, tetrafluoroethylene, and vinyl alcohol. Among these monomers,
styrene, methyl methacrylate, ethylene oxide, butadiene, isoprene, vinylpyridine, and lactic
acid are preferably used from the viewpoints that the formation of phase separation easily
occurs, and that concavities and convexities of the concave-convex structure are easily
formed by an etching.
[0031] Further, examples of a combination of the first homopolymer and the second
,
I homopolymer may include combinations of two selected from the group consisting of a
i
:. . .! styrene-based polymer (more preferably, polystyrene), polyalkyl methacrylate (more
preferably, polymethyl methacrylate), polyethylene oxide, polybutadiene, polyisoprene,
!
polyvinylpyridine, and polylactic acid. Among these combinations, a combination of the
styrene-based polymer and polyalkyl methacrylate, a combination of the styrene-based
polymer and polyethylene oxide, a combination of the styrene-based polymer and
polyisoprene, a combination of the styrene-based polymer and polybutadiene are more
preferable, and the combination of the styrene-based polymer and polymethyl methacrylate,
the combination of the styrene-based polymer and polyisoprene, the combination of the
styrene-based polymer and polybutadiene are particularly preferable. A combination of
polystyrene (PS) and polymethyl methacrylate (PMMA) is further preferable from the
viewpoint of obtaining a preferable number average molecular weight (Mn) of the block
copolymer.
[0032] The number average molecular weight (Mn) of the block copolymer is preferably
not less than 500,000, and more preferably not less than 1,000,000, and particularly
preferably in a range of 1,000,000 to 5,000,000. The domain size of the block copolymer
increases as the molecular weight thereof increases. In a case that the number average
molecular weight is less than 500,000, the average pitch of the concavities and convexities
formed by the micro phase separation structure of the block copolymer is so small that the
average pitch of the concavities and convexities of the obtained diffraction grating
becomes insufficient. Especially, in a case of the diffraction grating used for the organic
EL, the diffraction grating needs to diffract illumination light over a range of wavelength -
of the visible region, and thus the average pitch is desirably in a range of 100 mn to 1,500
nm, more desirably in a range of 200 nm to 1,200 mn. In view of this point, the number
13
average molecular weight (Mn) of the block copolymer is preferably not less than 500,000.
[0033] The molecular weight distribution (MwIMn) of the block copolymer is preferably
not more than 1.5, and is more preferably in a range of 1.0 to 1.35. In a case that the
molecular weight distribution exceeds 1.5, it is difficult to form the regular micro phase
separation structure of the block copolymer.
100341 Note that the number average molecular weight (Mn) and the weight average
molecular weight (Mw) of the block copolymer are values measured by the gel permeation
chromatography (GPC) and converted to the molecular weights of standard polystyrene.
[0035] In the block copolymer, the volume ratio between the first polymer segment and
the second polymer segment (the first polymer segment: the second polymer segment) is
desirably in a range of 4:6 to 6:4 in order to generate a horizontal cylinder structure by
self-organization or assembly (to be described later on), and is more preferably about 5:5.
In a case that the volume ratio is out of the above-described range, it is difficult to form a
concave-convex pattern (concavity and convexity pattern) owing to the horizontal cylinder
structure (to be described later on) and there is a tendency that a globular or spherical
structure or vertical cylinder structure appears.
[0036] The block copolymer solution used in the present invention is prepared by
dissolving the block copolymer in a solvent. Examples of the solvent include aliphatic
hydrocarbons such as hexane, heptane, octane, decane, and cyclohexane; aromatic
hydrocarbons such as benzene, toluene, xylene, and mesitylene; ethers such as diethyl ether,
tetrahydrofuran, and dioxane; ketones such as acetone, methyl ethyl ketone, isophorone,
and cyclohexanone; ether alcohols such as butoxyethyl ether, hexyloxyethyl alcohol,
methoxy-2-propanol, and benzyloxyethanol; glycol ethers such as ethylene glycol dimethyl
ether, diethylene glycol dimethyl ether, triglyme, propylene glycol monomethyl ether, and
propylene glycol monomethyl ether acetate; esters such as ethyl acetate, ethyl lactate, and
y-butyrolactone; phenols such as phenol and chlorophenol; amides such as
N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyn-olidone;
halogen-containing solvents such as chloroform, methylene chloride, tetrachloroethane,
monochlorobenzene, and dichlorobenzene; hetero-element containing compounds such as
carbon disulfide; and mixture solvents thereof. The percentage content of the block
copolymer in the block copolymer solution is preferably in a range of 0.1 % by mass to
15% by mass, and more preferably in a range of 0.3% by mass to 5% by mass, relative to
100% by mass of the block copolymer solution.
14
100371 In addition, the block copolymer solution further contains polyalkylene oxide as a
different homopolymer (a homopolymer other than the first homopolymer and the second
homopolymer in the block copolymer contained in the solution: for example, in a case that
the combination of the first homopolymer and the second homopolymer in the block
copolymer is the combination of polystyrene and polymethyl methacrylate, the different
homopolymer may be any kind of homopolymer other than polystyrene and polymethyl
methacrylate).
[0038] By allowing the block copolymer solution to contain polyalkylene oxide, the
depth of the concavities and convexities formed by the micro phase separation structure of
the block copolymer can be increased. As the polyalkylene oxide, polyethylene oxide or
polypropylene oxide is more preferable, and polyethylene oxide is particularly preferable.
Further, as the polyethylene oxide, one represented by the following formula is preferable:
HO-(CH2-CH2-O),-H
[in the formula, "nu represents an integer in a range of 10 to 5,000 (more preferably an
integer in a range of 50 to 1,000, and further preferably an integer in a range of 50 to 500)l.
[0039] Further, the number average molecular weight (Mn) of polyalkylene oxide is
preferably in a range of 460 to 220,000, and is more preferably in a range of 2,200 to
46,000. In a case that the number average molecular weight is less than the lower limit,
the molecular weight is so low that polyalkylene oxide is liquid at room temperature, is
easily separated out and precipitates; in another case that the number average molecular
weight exceeds the upper limit, the synthesis of such polyalkylene oxide is difficult.
/0040] The molecular weight distribution (MwJMn) of polyalkylene oxide is preferably
not more than 1.5, and more preferably in a range of 1.0 to 1.3. In a case that the
molecular weight distribution exceeds the upper limit, the uniformity of shape of the micro
phase separation is less likely to be maintained. Note that the number average molecular
weight (Mn) and the weight average molecular weight (Mw) are values measured by the
gel permeation chromatography (GPC) and converted to molecular weights of standard
polystyrene.
[0041] Further, in the present invention, it is preferable that the combination of the first
homopolymer and the second homopolymer in the block copolymer is the combination of
polystyrene and polymethyl methacrylate (polystyrene-polymethyl methacrylate). By
using a polystyrene-polymethyl methacrylate block copolymer and polyalkylene oxide
such as polyethylene oxide in combination as described above, the orientation in the
15
vertical direction is firther improved, thereby making it possible to further increase the
depths of the concavities and convexities on the surface, and to shorten the solvent
annealing process time during the production.
100421 The content of polyalkylene oxide is preferably in a range of 1 part by mass to 100
parts by mass, and particularly preferably in a range of 5 parts by mass to 100 parts by
mass, relative to 100 parts by mass of the block copolymer. The content of polyalkylene
oxide is further preferably in a range of 5 parts by mass to 70 parts by mass. In a case
that the content of polyalkylene oxide is less than 5 parts by mass, the effect obtained by
containing polyalkylene oxide becomes insufficient. On the other hand, in a case that the
content of polyalkylene oxide exceeds 100 parts by mass relative to 100 parts by mass of
the block copolymer, the concave-convex pattern formed by the phase separation of the
block copolymer easily collapses; in a case that the content of polyalkylene oxide exceeds
70 parts by mass, polyalkylene oxide precipitates in some cases.
100431 The total percentage content of polyalkylene oxide and the different homopolymer
in the block copolymer solution is preferably in a range of 0.1% by mass to 15% by mass,
and more preferably in a range of 0.3% by mass to 5% by mass, in the block copolymer
solution. In a case that the total percentage content is less than the lower limit, it is
difficult to uniformly apply the solution on a base member (coat a base member with the
solution) to attain a film of which thickness is sufficient to obtain a necessary film
thickness. On the other hand, in a case that the total percentage content exceeds the upper
limit, it is relatively difficult to prepare a solution in which polyalkylene oxide and the
different homopolymer are uniformly dissolved in the solvent.
I00441 Further, the block copolymer solution may further contain another homopolymer
different from polyalkylene oxide, a surfactant, an ionic compound, an anti-foaming agent,
a leveling agent, and the like.
100451 In a case that the block copolymer solution contains the another homopolymer, the
another homopolymer may be contained at a ratio in a range of 1 part by mass to 100 parts
by mass, relative to 100 parts by mass of the block copolymer, similarly to polyalkylene
oxide. In a case that the surfactant is used, the content of the surfactant is preferably not
more than 10 parts by mass, relative to 100 parts by mass of the block copolymer.
Further, in a case that the ionic compound is used, the content of the ionic compound is
preferably not more than 10 parts by mass, relative to 100 parts by mass of the block
copolymer.
16
[0046]
[Block copolymer solution coating step]
According to the mold-producing method of the present invention, as shown in
Fig. 1(A), the block copolymer solution prepared as described above is applied on a base
member 10 (a base member 10 is coated with the block copolymer solution) to form a thin
film 30. The base member 10 is not especially limited, and includes, for example, resin
substrates of resins such as polyimide, polyphenylene sulfide (PPS), polyphenylene oxide,
polyether ketone, polyethylene naphthalate, polyethylene terephthalate, polyarylate,
triacetyl cellulose, and polycycloolefin; inorganic substrates such as glass,
octadecyldimethyl chlorosilane (ODs) treated glass, octadecyl trichlorosilane (OTS)
treated glass, organo silicate treated glass, glass substrates treated with a silane coupling
agent, and silicon substrates; and substrates of metals such as aluminum, iron, and copper.
Further, the base member 10 may be subjected to a surface treatment such as an orientation
treatment, etc. For example, the organo silicate treated glass can be prepared by coating a
glass with a methyl isobutyl ketone (MIBK) solution of methyl trimethoxysilane (MTMS)
and 1,2-bis(trimethoxysily1) ethane (BTMSE), and then performing heating process to the
glass coated with the MIBK solution. Further, each of the octadecyldimethyl chlorosilane
treated glass and octadecyl trichlorosilane treated glass can be prepared by such a method
including immersing a glass in a heptane solution of one of the octadecyldimethyl
chlorosilane and octadecyl trichlorosilane, and washing out the unreacted portion from the
glass. In such a manner, it is allowable to perform surface treatment to a surface of the
substrate such as the glass with a primer layer of the octadecyldimethyl chlorosilane,
organo silicate, etc., or to perfom the silane coupling treatment to the substrate surface
with a general silane coupling agent, thereby making it possible to improve the adhesion
property of the block copolymer to the substrate. In a case that the adhesion property is
not sufficient, the block copolymer drops off or detaches from the substrate during the
electrofoming, which in turn adversely affect the production of a mold for transferring.
[0047] The method for applying the block copolymer solution on the base member
(coating the base member with the block copolymer) is not particularly limited; it is
allowable to employ, for example, the spin coating method, spray coating method, dip
coating method, dropping method, gravure printing method, screen printing method, relief
printing method, die coating method, curtain coating method, ink-jet method, etc., as the
method for applying the block copolymer.
17
[0048] The thickness of the thin film 30 of the block copolymer is preferably within a
range which allows the thickness of a dried coating film, as will be described later, to be in
a range of 10 nm to 3,000 nrn, and more preferably within a range which allows the
thickness of the dried coating film to be in a range of 50 nrn to 500 nm.
[0049]
[Drying step]
After the base member 10 is coated with the block copolymer solution to form the
thin film 30, the thin film 30 on the base member 10 is dried. The drying can be
performed in the ambient atmosphere. The temperature for drying the thin film 30 is not
particularly limited, provided that the solvent can be removed from the thin film 30. For
example, the drying temperature is preferably in a range of 10 degrees Celsius to 200
degrees Celsius, and more preferably in a range of 20 degrees Celsius to 100 degrees
Celsius. Note that in some cases, the drying step starts the formation of micro phase
separation structure of the block copolymer, which results in appearance of concavities and
convexities on the surface of the thin film 30 during the drying step.
[OOSO]
[Solvent annealing step]
After the drying step, the solvent annealing process (solvent phase-separation
process) is performed for the thin film 30 under atmosphere of the vapor of an organic
solvent so as to form a phase separation structure of the block copolymer inside the thin
film 30. With this solvent annealing process, the self-organization of the block
copolymer is advanced such that the block copolymer undergoes micro phase separation
into a portion corresponding to a first polymer segment 32 and a portion corresponding to a
second polymer segment 34, thereby generating a horizontal cylinder structure, as shown
in Fig. 1(B). Here, the term "horizontal cylinder structure" means a structure wherein the
first polymer segment or the second polymer segment is self-organized such that the first
or second polymer segment extends (is oriented) in a form of cylinders in a direction along
the surface, of the base member, coated with the solution of the block copolymer. On the
other hand, the term "vertical cylinder structure" means a structure wherein the first
polymer segment or the second polymer segment is self-organized such that the first or
second polymer segment extends (is oriented) in a form of cylinders in a direction
substantially vertical to the surface, of the base member, coated with the solution of the
block copolymer. These structures can be confirmed by staining the polymer with
18
ruthenium oxide or osmium oxide and by observing the cross-sectional shape of the stained
polymer with an electron microscope, etc. In addition, the small-angle X-ray scattering
(SAXS) measurement is also effective for identifying the orientation of these structures.
[0051] For example, the solvent annealing process can be practiced by providing
atmosphere of the vapor of organic solvent (organic solvent vapor) inside a tightly sealable
container such as a desiccator, and by exposing the thin film 30 as the objective under this
atmosphere. The concentration of the organic solvent vapor is preferably high for the
purpose of promoting the phase separation of the block copolymer, is preferably saturated
vapor pressure. In a case that the concentration of the organic solvent vapor is saturated
vapor pressure, the concentration of the organic solvent vapor is relatively easy to control.
For example, in a case that the organic solvent is chloroform, the saturated vapor pressure
of chloroform is known t'o be in a range of 0.4 gil to 2.5 g/l at room temperature (0 degrees
Celsius to 45 degrees Celsius). In a case that the organic solvent annealing process time
using the organic solvent such as chloroform is too long, the polyethylene oxide tends to
precipitate on the surface of the applied (coating) film andlor the phase-separated
concave-convex shape (pattern) tends to collapse (to become blunt). The process time
(process time period) of the solvent annealing process can be in a range of 6 hours to 168
hours, preferably in a range of 12 hours to 48 hours, more preferably in a range of 12 hours
to 36 hours. In a case that the process time is too long, the concave-convex shape
collapses (becomes blunt); in a case that the process time is too short, the depth of the
grooves in the concave-convex structure is shallow, and in a case that a diffraction grating
is produced by using the mold, the diffraction effect of the diffraction grating is not
sufficient.
[0052j The organic solvent to be used in the solvent annealing process is preferably an
organic solvent of which boiling point is in a range of 20 degrees Celsius to 120 degrees
Celsius; it is possible to use, for example, chloroform, dichloromethane, toluene,
tetrahydrofuran (THF), acetone, carbon disulfide, and mixture solvents thereof. Among
these solvents, chloroform, dichloromethane, acetone, a mixture solvent of acetone/carbon
disulfide. The solvent annealing may be performed at the ambient temperature in a range
of 0 degrees Celsius to 45 degrees Celsius. In a case that the ambient temperature is
higher than 45 degrees Celsius, the concave-convex structure formed in the thin film
become blunt and easily collapses. In an environment lower than 0 degrees Celsius, the
organic solvent hardly evaporates, and the phase separation of the block copolymer is hard
19
to occur.
[0053] The inventors of the present invention found out that the solvent annealing process
causes the block copolymer to undergo the phase separation into the horizontal cylinder
structure. Normally, the following is known: in a case that the mixing ratio between the
first homopolymer and the second homopolymer constructing the block copolymer is even
( 5 5 ) or approximately even, a phase separation structure of the lamella type appears by the
thermal annealing process; in a case that the mixing ratio is approximately 3:7, the cylinder
structure appears by the thermal annealing process; and in a case that the mixing ratio is
approximately 2:8, the spherical structure appears by the thermal annealing process.
However, the inventors found out that, when performing the solvent annealing process
according to the present invention, the phase separation occurs while generating a cylinder
structure in the horizontal direction even in a case that the mixing ratio of the first
homopolymer and the second homopolymer constructing the block copolymer is in a range
of 40:60 to 60:40. Although the reason for the above phenomenon is not clear, the
inventors consider that as the organic solvent permeates into one of the homopolymers and
causes one of the homopolymers to swell, which in turn creates such a situation that the
apparent volume ratio between the first and second homopolymers is different from the
actual mixing ratio between the first and second homopolymers.
[0054] In the horizontal cylinder structure, a first homopolymer 32 is present in a layer of
a second homopolymer 34, and is oriented in a form of cylinders extending in a direction
substantially parallel to the surface of the base member 10, as shown in Fig. l(B). As a
result, a surface (top) layer portion, of the second homopolymer 34, under (inside) which
the first homopolymer 32 is present, is smoothly raised to form a wave-like shape. Note
that it is allowable that the cylinder-like arrangement in which the first homopolymer 32 is
oriented in the form of cylinders extending in the direction substantially parallel to the
surface of the base member 10 is formed in a plurality of layers (plurality of tiers or stages)
in a direction (height direction) vertical to the surface of the base member 10 (see Figs. 8A
and 8B which will be described later on). The raised wave-like structure can be used as it
is as a concave-convex pattern of an optical substrate such as a difkaction grating.
Accordingly, unlike the case of phase separation by the thermal annealing, there is no need
to remove one of the homopolymers by the etching after the phase separation. Note that a
vertical cylinder structure or a spherical structure may be included in a part of the
horizontal cylinder structure.
20
[0055] Since the etching process is not necessary in the solvent annealing process, the
patterning process for the mold can be simplified. Further, although the etching process
normally involves the following problems, the mold-producing method of the present
invention does not involve such problems. Namely, when performing the etching process;
any projecting portion is easily generated in the remaining homopolymer pattern, the value
of kurtosis (to be described later on) is small, and any cross-sectional shape having an
overhang portion is easily generated. Accordingly, in the electroforming process
performed thereafter, the plating metal is easily drawn to a projection portion andlor a
projected comer (edge) of the object, and is less likely to be drawn to a recessed portion or
a dented portion of the object. Further, a seed layer to be deposited before the
electroplating process is also less likely to adhere to a portion having such a complicated
structure. Due to the situations described above, any defect is likely to occur in the
pattern due to the etching process. Furthermore, any stain and/or debris (dust) arelis
easily generated on the mold in the etching process due to the usage of etching liquid
and/or the removal of one of the homopolymers constructing the block copolymers. By
using the solvent annealing process, however, the necessity for the etching process is
eliminated, thereby solving the above-described problems associated with the etching and
making it possible to obtain a mold which has a reliable concave-convex pattern and to
which little foreign matter adheres and to obtain an optical substrate such as a diffraction
grating produced based on the mold. Accordingly, the optical substrate such as the
diffraction grating can be produced with a high throughput and in a simple process.
100561 In the present invention, the surface shape defined by the polymer segment 34
through the solvent annealing process is constructed of a relatively smooth and sloped
(inclined) surface, as conceptually shown in Fig. 1(B), forming a wave-like shape (referred
to as "wave-like structure" in the present application, as appropriate) in a direction upward
from the base member. In such a wave-like structure 38, there is no overhang, and thus
the wave-like structure is duplicated into an inverted pattern in a metal layer accumulated
on the wave-like structure 38, thereby allowing the metal layer to be easily releasable
(peelable).
[0057] The base member 10, which has the wave-like structure 38 obtained in such a
manner, can be used as a master (mold) for transfer in a subsequent step. .The average
pitch of the concavities and convexities representing the wave-like structure 38 is
preferably in a range of 100 nm to 1,500 nm, and more preferably in a range of 200 nm to
2 1
1,200 nm. In a case that the average pitch of the concavities and convexities is less than
the lower limit, the pitch is too small relative to the wavelength of a visible light, and thus
any required diffraction of the visible light is less likely to occur in a diffraction grating
obtained by use of such a master (master block). In a case that the average pitch exceeds
the upper limit, the diffraction angle of the diffraction grating obtained by use of such a
master is too small, and thus the functions as the diffraction grating cannot be fulfilled
sufficiently. Note that the term "average pitch of the concavities and convexities" means
an average value of the pitch of concavities and convexities in a case of measuring the
pitch of the concavities and convexities (spacing distance between adjacent convex
portions or spacing distance between adjacent concave portions) on a surface of a curable
resin layer. Further, such an average value of the pitch of concavities and convexities is
obtained as follows. Namely, a concavity and convexity analysis image is obtained by
measuring the shape of the concavities and convexities on the surface by using a scanning
probe microscope (for example, a scanning probe microscope manufactured by Hitachi
High-Tech Science Corporation, under the product name of "E-sweep", or the like), then
the distances between randomly selected concave portions or convex portions adjacent to
each other are measured at not less than 100 points in the concavity and convexity analysis
image, and then the average of the distances is calculated and is determined as the average
value of the pitch of concavities and convexities.
[0058] Further, the average value of depth distribution of concavities and convexities
representing the concave-convex structure 38 is preferably in a range of 20 nm to 200 nm,
more preferably in a range of 30 nm to 150 nm. In a case that the average value of depth
distribution of the concavities and convexities is less than the lower limit, the height is not
sufficient with respect to the wavelength of the visible light, thus resulting in insufficient
difffaction; in a case that the average value exceeds the upper limit and that the obtained
diiEaction grating is used as an optical element on the light extraction port side of an
organic EL element, the organic EL element tends to be easily destructed and the life
thereof tends to be shortened due to the heat generation occurring when the electric field
distribution in the organic layer becomes non-uniform, causing the electric field to
concentrate on a certain position or area in the organic layer. The average value (m) of
the depth distribution of concavities and convexities is represented by the following
formula (I):
I00591
22
[Formula I]
[in the formula (I), "N" represents the total number of measurement points (total pixel
count), "i" represents any one of integers in a range of 1 to N, "x," represents data of depth
of concavities and convexities at an i-th measurement point, and "m" represents the
average value of depth distribution of concavities and convexities].
[0060]
[Heating step]
It is allowable to perform heating process to the concave-convex structure of the
thin film 30 obtained by the above solvent annealing process. Since the wave-like
concave-convex structure has been already formed by the solvent annealing process, the
heating process blunts the formed concave-convex structure in some case. The heating
process, however, is not necessarily indispensable. The heating process is useful, for
example, in such a case that any projection portion is formed, due to any reason, at a
portion on the surface of the concave-convex structure after the solvent annealing process
andlor such a case that the heating process is needed for adjusting the periodicity andlor
height of the concave-convex structure. The heating temperature can be, for example, not
less than the glass-transition temperatures of the first and second homopolymer segments
32, 34, such as a temperature not less than the glass-transition temperature of each of the
first and second homopolymers 32,34 and not more than a temperature that is higher than
the glass-transition temperature by 70 degrees Celsius. The heating process can be
performed in the ambient atmosphere by using an oven, etc.
[0061]
[Seed layer forming step]
As shown in Fig. 1 (C), a seed layer 40 functioning as an electroconductive layer
for a subsequent electroforming process is formed on the surface of the wave-like structure
38 of the master obtained as described above. The seed layer 40 can be formed by the
non-electrolytic plating, sputtering, or vapor deposition. The thickness of the seed layer
40 is preferably not less than 10 nm, and more preferably not less than 20 nm to uniformize
the current density during the subsequent electroforming process, thereby making the
23
thickness of the metal layer accumulated by the subsequent electroforming process to be
constant. As the material of the seed layer, it is possible to use, for example, nickel,
copper, gold, silver, platinum, titanium, cobalt, tin, zinc, chrome, gold-cobalt alloy,
gold-nickel alloy, boron-nickel alloy, solder, copper-nickel-chromium alloy, tin-nickel
alloy, nickel-palladium alloy, nickel-cobalt-phosphorus alloy, or alloy thereof.
[0062]
[Electroforming step]
Next, a metal layer 50 is accumulated on the seed layer 40 by the electroforming
(electroplating), as shown in Fig. 1 (D). The whole thickness of the metal layer 50
including the thickness of the seed layer 40 can be, for example, in a range of 10 pm to
3,000 pm. As the material of the metal layer 50 to be accumulated by the electroforming,
it is possible to use any of metal species as described above which can be used as the seed
layer 40. Nickel is preferable in view of the wear resistance and releasing property as the
mold. In this case, nickel is also preferably used for the seed layer 40. The current
density during the electroforming may be, for example, in a range of 0.03 ~ l c mt'o 10
A/cm2 for suppressing bridge to form a uniform metal layer and in view of shortening of
electroforming time (duration of electroforming time). Considering the easiness for
performing the subsequent processes such as pressing with respect to a resin layer,
releasing, and cleaning, the formed metal layer 50 desirably has appropriate hardness and
thickness. A diamond like carbon (DLC) processing or a Cr plating processing treatment
may be performed on the surface of the metal layer formed by the electroforming in order
to improve the hardness of the metal layer. Alternatively, the surface hardness of the
metal layer may be improved by further performing the heating process of the metal layer.
I00631
[Releasing step]
The metal layer 50 including the seed layer obtained as described above is
released (peeled off) kom the base member having the concave-convex structure to thereby
obtain a mold as a father die. As the releasing method (peeling method), the metal layer
50 may be released physically, or the first and second homopolymer and the remaining
block copolymer may be dissolved to be removed by using an organic solvent which
dissolves the first and second homopolymer and the remaining block copolymer, such as
toluene, tetrahydrofuran (THF), and chloroform.
[0064]
24
[Cleaning step]
In a case of releasing the mold from the base member 10 having the wave-like
structure 38 as described above, a polymer portion or portions 60 of the polymer remain(s)
on the mold in some cases, as shown in Fig. 1(E). In such a case, each of the polymer
portions 60 remaining on the mold can be removed by cleaning. As a cleaning method,
the wet cleaning or dry cleaning can be used. As the wet cleaning, the remaining polymer
portions 60 can be removed by performing the cleaning with an organic solvent such as
toluene and tetrahydrofuran, a surfactant, or an alkaline solution. In a case that the
organic solvent is used, ultrasonic cleaning may be carried out. Alternatively, the
remained polymer portions 60 may be removed by performing electrolytic cleaning. As
the dry cleaning, the remaining polymer portions 60 can be removed by ashing using
ultraviolet light and/or plasma. The wet cleaning and the dry cleaning may be used in
combination. After the cleaning as described above, a rinse process with pure water or
purified water may be performed, and then ozone irradiation may be carried out after a
drylng process. Thus, a mold 70 having a desired concave-convex structure as shown in
Fig. 1 (F) is obtained.
LO0651 Next, a method for producing a diffraction grating usable for the organic EL
element, etc., by using the obtained mold 70 will be explained with reference to Fig. 2(A)
to Fig. 2(E).
[0066]
[Mold-release treatment step]
In a case that the mold 70 is used to transfer the concave-convex structure of the
mold 70 to a resin, a mold-release treatment may be performed for the mold 70 so as to
improve the releasability of the mold from the resin. As the mold-release treatment, a
manner to decrease the surface energy is commonly used. Although the mold-release
treatment is not particularly limited, the mold-release treatment includes, for example, a
method in which a concave-convex surface 70a of the mold 70 is coated with a
mold-release agent 72 such as a fluorine-based material and a silicone resin-based
mold-release agent, as shown in Fig. 2(A), a method in which the surface is subjected to a
treatment using a fluorine-based silane coupling agent, a method in which a film of a
diamond like carbon is formed on the surface, etc.
[Step for transfening the concave-convex structure of the mold to a concave-convex
25
forming material layer]
By using the obtained mold 70, a substrate (or a master block) having a
concave-convex structure transferred thereon is produced by transfemng the
concave-convex structure (pattern) of the mold to a concave-convex forming material layer
which is formed of an organic material such as a resin or an inorganic material such as a
sol-gel material. Note that when transfemng the concave-convex structure of the mold 70,
the shape of the mold 70 may be changed suitably to the transfer. For example, in a case
of performing the transfer with a roll, the mold 70 may be wound around the outer
circumferential surface of a cylindrical body as a roll-shaped mold (transfer process using
the roll-shaped mold will be described in detail later on).
[0068] First, an explanation will be given about a case that the concave-convex forming
material to which the concave-convex structure is to be transferred is a resin layer. As the
method of the transfer process, for example, a supporting substrate 90 is coated with a
curable resin to form a resin layer 80, and then the resin layer 80 is cured while the
concave-convex structure of the mold 70 is being pressed against the resin layer 80, as
shown in Fig. 2(B). Examples of the supporting substrate 90 include a base member
made of a transparent inorganic material such as glass; a base member made of a resin such
as polyethylene terephthalate (PET), polyethylene terenaphthalate (PEN), polycarbonate
(PC), cycloolefin polymer (COP), polymethyl methacrylate (PMMA) or polystyrene (PS);
a stacked base member having a gas barrier layer made of an inorganic substance such as
SIN, Si02, Sic, SiO,N,, Ti02, or A1203 formed on the surface of a base member made of
any one of the above-described resins; and a stacked base member formed by alternately
stacking a base member made of any one of the above-described resins and a gas barrier
layer made of any one of the above-described inorganic substances. Further, the
thickness of the supporting substrate 90 may be within a range of 1 pm to 500 pm. In a
case of performing the transfer by using a roll-shaped mold as the mold 70, an elongated
(lengthy) sheet-shaped substrate having flexibility is preferably used as the supporting
substrate 90, as will be described later on. Note that although the supporting substrate 90
is desirably transparent depending on the usage, the supporting substrate 90 needs not be
transparent in a case of using the resin layer 80 having the concave-convex structure
transferred thereon is used again as the mold (master block).
[0069] Examples of the concave-convex forming material include curable resins
including a variety of kinds of UV curable resin such as epoxy resin, acrylic resin, urethane
26
resin, melamine resin, urea resin, polyester resin, phenol resin, and cross-linking type
liquid crystal resin. The thickness of the curable resin is preferably in a range of 0.5 pm
to 500 pm. In a case that the thickness is less than the lower limit, heights of the
concavities and convexities formed on the surface of the cured resin layer are more likely
to be insufficient. In a case that the thickness exceeds the upper limit, the effect of
volume change of the resin which occurs upon curing is likely to be so large that the
formation of the shape of the concavities and convexities tends to be unsatisfactory.
[0070] As a method for coating the supporting substrate 90 with the concave-convex
forming material, it is possible to adopt various coating methods such as the spin coating
method, spray coating method, dip coating method, dropping method, gravure printing
method, screen printing method, relief printing method, die coating method, curtain coating
method, ink-jet method, and sputtering method. Further, the condition for curing a
concave-convex forming material such as the curable resin varies depending on the kind of
the resin used. For example, the curing temperature is preferably in a range of the room
temperature to 250 degrees Celsius, and the curing time is preferably in a range of 0.5
minutes to 3 hours. Alternatively, a method may be employed in which the curable resin
is cured by being irradiated with energy ray such as ultraviolet light or electron beam. In
such a case, the amount of the irradiation is preferably in a range of 20 m.T/cm2 to 5 Ucm2.
[0071] Subsequently, the mold 70 is detached from the curable rein layer 80 which has
been cured. The method for detaching the mold 70 is not limited to a mechanical
releasing method, and any known method can be adopted as the detaching method. Note
that in a case of using the above-described roll-shaped mold, a releasing roll (peeling roll)
can be used in order to promote the release of the mold off from the cured resin layer 80.
Then, as shown in Fig. 2(C), it is possible to obtain a resin film structure 100 in which the
cured rein layer 80 having the concavities and convexities is formed on the supporting
substrate 90. The resin film structure 100 may be used, as it is, as the diffraction grating.
Alternatively, it is also possible to use the resin film structure 100 further as a mold to
produce a structure constructed of an organic material such as a resin or a structure
constructed of an inorganic material such as a sol-gel material, and to use either of the
structures as a diffraction grating, as will be described later on.
[0072] The mold-producing method according to the present invention can be used not
only for producing a diffraction grating provided on the light extraction port side of the
organic EL element but also for producing an optical component having a minute or fine
27
pattem usable for various devices. For example, the mold-producing method according to
the present invention can be used to produce a wire grid polarizer, an antireflection film, a
liquid crystal display, a touch panel or an optical element for providing the light
confinement effect in a solar cell by being placed on the photoelectric conversion surface
side of the solar cell.
[0073] As described above, the resin film structure 100 having a desired pattern can be
obtained. In a case that the inverted pattern of the resin film structure 100 is used as the
diffraction grating, the resin film structure 100 obtained through the transfer process of the
mold as described above is used as the master block; another transparent supporting
substrate 92 is coated with a curable resin layer 82 and the curable resin layer 82 is cured
while the resin film structure 100 is being pressed against the curable resin layer 82, as
shown in Fig. 2(D), similar to a case in which the resin film structure 100 is formed.
Subsequently, the resin film structure 100 is released from the curable resin layer 82 which
has been cured, and thus a replica 1 10 as another resin film structure as shown in Fig. 2(E)
can be obtained. Further, it is allowable to produce a replica having the inverted pattern
of the replica 11 0 by performing the above transfer step using the replica 11 0 as a master
andlor to form a sub-replica by repeating the above transfer step again using the replica
having the inverted pattem as the master block.
100741 Here, an explanation will be given about a method for effectively performing the
transfer process of the mold to the resin layer (roll-to-roll process), with reference to Fig. 4.
A roll processing apparatus 170 shown in Fig. 4 forms a concave-convex pattern on a
coating film applied (formed) on an elongated (long-length) substrate film 180 to thereby
produce a film-shaped substrate 180a. The roll processing apparatus 170 is mainly
provided with a transporting system 186 configured to transport the substrate film (base
member) 180; a die coater 182 configured to coat the substrate film 180, which is being
transported, with a concave-convex forming material; a metallic roll 190 located on the
downstream of the die coater 182 and configured to transfer a pattern; and an irradiation
light source 185 which is disposed to face the metallic roll 190 with the substrate film 180
being intervened between the irradiation light source 185 and the metallic roll 190, and
which is configured to irradiate an UV light onto the substrate film 180. The transporting
system 186 for transporting the substrate film 180 has a film feeding roll 172 configured to
feed the substrate film 180; a nip roll 174 and a releasing roll 176 arranged respectively on
the upstream and the downstream of the metallic roll 190 and configured to urge the
28
substrate film 180 toward the metallic roll 190; a take-up roll (winding roll) 187 configured
to take up (wind up) a substrate film 180a having the pattern transferred thereon; and a
plurality of transporting rolls 178 configured to transport the substrate film 180. Here, it
is possible to use, as the metallic roll 190, a roll-shaped mold obtained by winding the
mold 70 (see Fig. l(F)), which has been prepared in advance, around the outer
circumferential surface of a cylindrical body.
[0075] The roll processing apparatus 170 is used to obtain a film-shaped substrate having
a pattern of the metallic roll 190 transferred thereon, with the following process. The
substrate film 180 wound around the film feeding roll 172 in advance is fed toward the
downstream by the rotation of the film feeding roll 172, the film take-up roll 187, etc.
When the substrate film 180 passes the die coater 182, the die coater 182 coats a surface of
the substrate film 180 with a concave-convex forming material 184, thereby forming a
coating film having a predetermined thickness. Subsequently, the coating film on the
substrate film 180 is pressed against the outer circumferential surface of the metallic roll
190 by the nip roll 174, thereby the pattern on the outer circumferential surface of the
metallic roll 190 is transferred to the coating film. Concurrently with or immediately
after the pattern transfer, the coating film is irradiated with the UV light from the
irradiation light source 185, thereby the concave-convex forming material 184 is cured.
Although the wavelength of the UV light is different depending on the kind or property of
the concave-convex forming material 184, the wavelength is generally in a range of 200
nm to 450 nrn; the irradiation amount of the UV light may be in a range of 10 m3/cm2 to 5
~/cm'. The substrate film 180 coated with the concave-convex forming material having
the cured pattern is released away from the metallic roll 190 by the releasing roll 176, and
then is took up (wound up) by the take-up roll 187. In such a manner, the elongated
film-shaped substrate 180a can be obtained. The elongated film-shaped substrate 180a
can be cut appropriately to be used as diffraction gratings. Alternatively, the elongated
film-shaped substrate 180a can be used as a mold to transfer the concave-convex pattern
again on a curable resin, a sol-gel material, etc. In particular, it is advantageous to
perform the transfer onto the sol-gel material by using the elongated film-shaped substrate
180a as the mold, as will be described later on. Note that such an elongated film-shaped
substrate 180a is obtained while being wound in a roll form, and thus is suitable as the
mold used in a mass production process of an optical substrate (diffraction grating
substrate), and has a suitable form for being transported to an apparatus for
29
mass-producing the optical substrate. Further, after the film-shaped substrate is produced,
the film-shaped substrate can be stored or aged while being wound in a rolled form
temporarily.
[0076] Next, an explanation will be made about a method for producing a structure
having concavities and convexities made of a sol-gel material (hereinafter referred to as
"sol-gel structure" as appropriate) by further using the obtained resin film structure 100, as
shown in Fig. 2(C), as the master block. As shown in Fig. 5, a substrate-forming method
for forming a substrate (structure) having a concave-convex pattern using the sol-gel
material mainly includes: a solution preparation step S1 for preparing a sol; a coating step
(application step) S2 for applying the prepared sol on a substrate (coating the substrate
with the sol) to form a coating film; a drying step S3 for drying the coating film with which
the substrate is coated; a transfening step S4 for pressing a mold having a transfer pattern
formed thereon to the coating film; a releasing step S5 for releasing the mold from the
coating film; and a main baking (main calcination) step S6 for subjecting the coating film
to main baking. In the following, each of the steps will be explained sequentially.
100771 At first, a sol is prepared to form a coating film, to which a pattern is to be
transferred, by the sol-gel method (step S1 in Fig. 5). For example, in a case that silica is
synthesized by the sol-gel method on the substrate, a sol of metal alkoxide (silica
precursor) is prepared. The silica precursor is exemplified by metal alkoxides including,
for example, tetraalkoxide monomers such as tetramethoxysilane (TMOS),
tetraethoxysilane (TEOS), tetra-i-propoxysilane, tetra-n-propoxysilane, tetra-i-butoxysilane,
tetra-n-butoxysilane, tetra-sec-butoxysilane, and tetra-t-butoxysilane; trialkoxide
monomers such as methyl trimethoxysilane, ethyl trimethoxysilane, propyl
trimethoxysilane, isopropyl trimethoxysilane, phenyl trimethoxysilane, methyl
triethoxysilane (MTES), ethyl triethoxysilane, propyl triethoxysilane, isopropyl
triethoxysilane, phenyl triethoxysilane, methyl tripropoxysilane, ethyl tripropoxysilane,
propyl tripropoxysilane, isopropyl tripropoxysilane, phenyl tripropoxysilane, methyl
triisopropoxysilane, ethyl triisopropoxysilane, propyl triisopropoxysilane, isopropyl
triisopropoxysilane, phenyl triisopropoxysilane; a polymer obtained by polymerizing the
above monomers in small amounts; and a composite material characterized in that
fimctional group and/or polymer idare introduced into a part of the material. Further,
examples of the silica precursor include metal acetylacetonate, metal carboxylate,
oxychloride, chloride, and mixtures thereof. The silica precursor, however, is not limited
30
to these. In addition to Si, the examples of the metal species include Ti, Sn, Al, Zn, Zr, In,
and mixtures thereof, hut are not limited to these. It is also possible to use any
appropriate mixture of precursors of the oxides of the above metals.
[0078] In a case that a mixture of TEOS and MTES is used, the mixture ratio thereof can
be 1: 1, for example, in a molar ratio. This sol produces amorphous silica when caused to
perform the hydrolysis and polycondensation reaction. An acid such as hydrochloric acid
or an alkali such as ammonia is added in order to adjust the pH of the sol as a synthesis
condition. The pH is preferably not more than 4 or not less than 10. Water may be
added to perform the hydrolysis. An amount of water to be added can be not less than 1.5
times, with respect to metal alkoxide species, in the molar ratio. As the sol-gel material,
it is possible to use a material different from silica, and a material such as a Ti-based
material, IT0 (indium-tin oxide)-based material, A1203, ZrOz, ZnO, etc., may be used.
[0079] Examples of the solvent of the sol include alcohols such as methanol, ethanol,
isopropyl alcohol (IPA), and butanol; aliphatic hydrocarbons such as hexane, heptane,
octane, decane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene,
and mesitylene; ethers such as diethyl ether, tetrahydrofuran, and dioxane; ketones such as
acetone, methyl ethyl ketone, isophorone, and cyclohexanone; ether alcohols such as
hutoxyethyl ether, hexyloxyethyl alcohol, methoxy-2-propanol, and benzyloxyethanol;
glycols such as ethylene glycol and propylene glycol; glycol ethers such as ethylene glycol
dimethyl ether, diethylene glycol dimethyl ether, and propylene glycol monomethyl ether
acetate; esters such as ethyl acetate, ethyl lactate, and y-butyrolactone; phenols such as
phenol and chlorophenol; arnides such as N,N-dimethylformamide,
N,N-dimethylacetamide, and N-methylpyrrolidone; halogen-based solvents such as
chloroform, methylene chloride, tetrachloroethane, monochlorobenzene, and
dichlorobenzene; hetero-element containing compounds such as carbon disulfide; water;
and mixture solvents thereof. Especially, ethanol and isopropyl alcohol are preferable.
Further, a mixture of water and ethanol and a mixture of water and isopropyl alcohol are
also preferable.
[0080] As an additive to the sol, it is possible to use, for example, polyethylene glycol,
polyethylene oxide, hydroxypropylcellulose, and polyvinyl alcohol for viscosity
adjustment; alkanolamine such as triethanolamine, P-diketone such as acetylacetone,
P-ketoester, formamid, dimetylformamide, and dioxane as a solution stabilizer.
[0081] The substrate is coated with the sol prepared as described above (step S2 in Fig. 5).
31
From the viewpoint of mass-production, the substrate is preferably coated with the sol at a
predetermined position while a plurality of substrates are being transported continuously.
As the coating method, it is possible to adopt any coating method such as the bar coating
method, spin coating method, spray coating method, dip coating method, die coating
method, ink-jet method, etc. Among these methods, the die coating method, bar coating
method and spin coating method are preferable because these methods are capable of
performing the uniform coating of a substrate, which has a relatively large area, with the
sol, and of quickly completing the coating before the sol turns into a gel.
[0082] It is allowable to use, as the substrate, substrates made of inorganic materials such
as glass, silica glass, and silicon substrates, or substrates made of resins such as
polyethylene terephthalate (PET), polyethylene terenaphthalate (PEN), polycarbonate (PC),
cycloolefin polymer (COP), polymethyl methacrylate (PMMA), polystyrene (PS),
polyimide (PI), and polyarylate. The substrate may be transparent or opaque, and a
relatively hard substrate is preferable considering that a coating film (sol-gel material
layer) is formed on the substrate and further a function layer is formed on the sol-gel
material layer when the optical substrate is incorporated into a device. Further, in a case
that concave-convex patterned substrate obtained by using this substrate is to be used for
producing an organic EL element (which will be described later on), this substrate
preferably is a substrate having the heat resistance and the weather resistance against the
UV light, etc. In view of this, the substrates made of the inorganic materials such as the
glass, silica glass and silicon substrates are more preferable. Since the sol-gel material,
with which the substrates made of the inorganic materials is to be coated, is made of the
inorganic material, the difference in the refractive index between the substrates made of
inorganic materials and the sol-gel material layer is small, and thus these substrates are
preferable also in view of the capability for preventing any unintended refraction and/or
reflection inside the optical substrate. It is allowable to perform a surface treatment for or
provide an easy-adhesion layer on the substrate in order to improve the adhesion property,
and allowable to provide a gas barrier layer in order to keep out moisture and/or gas such
as oxygen. Note that a desired concave-convex pattern is formed with the sol-gel material
layer in a subsequent or following step, and thus the surface of the substrate (including the
surface treatment or the easy-adhesion layer in case that the surface treatment has been
performed or the easy-adhesion layer has been formed) may be flat, and the substrate itself
does not have the desired concave-convex pattern. Each of the substrates coated with the
32
sol is transferred (transported) preferably as it is for the subsequent drying and transfer
steps.
I
[0083] After the coating step, the substrate is kept (held) in the atmosphere or under 1I
reduced pressure to evaporate the solvent in the coating film (hereinafter referred to also as
"sol-gel material layer" as appropriate) applied on the substrate (step S3 in Fig. 5) to dry
the coating film. In a case that the holding time during which the substrate is kept is short,
the viscosity of the coating film is so low that the pattem cannot be transferred in the
following transfer step; in a case that the holding time is too long, the polymerization
reaction of the precursor is so advanced that the pattern cannot be transferred in the
following transfer step. In case of mass-producing the optical substrate, the holding time
can be controlled by managing the transporting time during which the substrate is
transported from a position where the coating of the substrate with the sol is performed to a
position where the substrate is subjected to the following transfer step with the film-shaped
substrate (mold). The holding temperature at which the temperature of the substrate is
kept in the drying step is preferably a constant temperature in a range of 10 degrees Celsius
to 100 degrees Celsius, and more preferably in a range of 10 degrees Celsius to 30 degrees
Celsius. In a case that the holding temperature is higher than the upper limit of this range,
the gel reaction of the coating film is rapidly proceeds before the transfer step and thus is
not desired; in a case that the holding temperature is lower than the lower limit of this
range, the gel reaction of the coating film is slowly proceeds before the transfer step, which
in turn lowers the productivity and thus not desired. After the sol coating is performed,
the polymerization reaction of the precursor proceeds as the evaporation of the solvent
proceeds, and the physical property such as the viscosity of the sol changes also in a short
period of time. The evaporation amount of the solvent depends also on the amount of
solvent (concentration of the sol) used in preparation of the sol. For example, in a case
that the sol contains the silica precursor, the hydrolysis and polycondensation reaction of
the silica precursor occur as the gel reaction, thereby producing alcohol in the sol via the
dealcoholation reaction. On the other hand, a volatile solvent such as alcohol is used in
the sol as the solvent. Namely, the sol contains the alcohol produced in the hydrolysis
reaction and the alcohol present as the solvent, and the sol-gel reaction proceeds by
removing these alcohols in the drying step. Therefore, it is desirable to adjust the holding
time and/or holding temperature considering the gel reaction and the solvent used. Note
that in the drying step, the solvent in the sol evaporates just by holding the substrate as it is,
33
and thus it is not necessarily indispensable to perform any active drying operation such as
heating, air blowing, etc. It is sufficient just to hold the substrate formed with the coating
film as it is for a predetermined period of time, to transfer the substrate for a predetermined
period of time for the following step(s), etc. From this viewpoint, the drying step may be
omitted.
[0084] After the predetermined period of time set as described above has elapsed, the
film-shaped substrate 180a as the mold obtained in the roll processing apparatus 170
shown in Fig. 4 is pressed against the coating film with a pressing roll (laminating roll) so
as to transfer the concave-convex pattem on the film-shaped substrate 180a to the coating
film on the substrate (step S4 in Fig. 5). For example, the concave-convex pattem of the
film-shaped substrate 180a can be transferred to a coating film (sol) 142 on a substrate 140
by feeding the film-shaped substrate 180a between a pressing roll 122 and the substrate
140 transported immediately below the pressing roll 122, as shown in Fig. 6. Namely,
when pressing the film-shaped substrate 180a against the substrate 140 with the pressing
roll 122, the film-shaped substrate 180a is made to cover the surface of the coating film
142 of the substrate 140 while the film-shaped substrate 180a and the substrate 140 are
being transported in a synchronized manner. At this time, the pressing roll 122 is rotated
while being pressed against the back surface of the film-shaped substrate 180a (surface on
the opposite side to the other surface of the film-shaped substrate 180a having the
concave-convex pattem formed thereon), thereby causing the film-shaped substrate 180a
and the substrate 140 to tightly contact with each other while being advanced. Note that
for feeding the elongated film-shaped substrate 180a toward the pressing roll 122, it is
advantageous to feed out the elongated film-shaped substrate 180a as it is from the take-up
roll 187 (see Fig. 4) around which the elongated film-shaped substrate 180a is wound.
[0085] By using the elongated film-shaped substrate 180a as the mold, the following
advantages are obtained. Namely, with respect to a hard mold that is formed of metal,
silica glass, etc., when any defect is found in the concave-convex pattem formed in the
hard mold, it is possible to clean a defective portion of the concave-convex pattem at
which the defect is located or to repair such defective portion (defect repairing). With
this, it is possible to prevent any failure in the substrate 140 which would have been
otherwise caused due to the defect transferred to the sol-gel side (the sol-gel material layer
on the substrate 140). With respect to a film-shaped mold (soft mold), however, such
cleaning andlor repair are not easy to perform therefor. On the other hand, the mold
34
formed of the metal, silica glass, etc. is roll-shaped, and thus when any defect occurs in this
mold due to, for example, clogging, etc., the transfer apparatus should be stopped
immediately and the mold should be exchanged. In contrast, the transfer with the
film-shaped mold is performed while each of the parts of the film-shaped mold being made
to correspond to each single glass substrate. Therefore, it is possible to mark any
defective portion such as the clogging in the film-shaped mold in advance in an inspection
stage, and the transporting operation of the glass substrate can be paused until the defective
portion of the film-shaped mold pass the glass substrate. Accordingly, the occurrence of
defective product can be lowered as a whole, thereby realizing enhanced throughput.
Further, when attempting to transfer the concave-convex pattern from the hard mold made
of metal, silica glass, etc., directly to the sol-gel material layer on the substrate, various
limitations as described below occur and the desired performance cannot be fully achieved
in some cases. For example, in a case of using a hard substrate made of glass, etc. as the
substrate on which the sol-gel material layer is formed, the mold and the substrate are both
hard. Therefore, when the pressing pressure for the mold is increased, any damage such
as cracking or breakage of the substrate occurs; on the contrary, when the pressing pressure
for the mold is decreased, the transfer of the concave-convex pattern is shallow, etc., and
thus the pressing pressure is hard to adjust. Therefore, there is no choice but to use a soft ,
material for the substrate or to use a soft material for the mold. Even in a case of using a
film-shaped mold, a material having a satisfactory releasability is required for the
film-shaped mold, and a material having satisfactory adhesiveness with respect to the
substrate and satisfactory transfer property for realizing satisfactory transfer of the
concave-convex pattern of the film-shaped mold thereto is required as the material to
which the concave-convex pattern of the film-shaped mold is transferred. Thus the
selectable materials as the material to which the concave-convex pattern of the film-shaped
mold is transferred is limited. In view of this, there are provided separate two steps that
are a step of firstly preparing (producing) a film-shaped mold from a metallic mold, and
another step of using the film-shaped mold to perform the transfer to the sol-gel material
layer, while selecting suitable materials for these two steps, respectively, thereby making
it possible to use a desired material on a desired substrate in each of these steps, realizing
satisfactory transfer not only satisfying the required properties but also generating no
defective portions in the pattern and with satisfactory releasability.
[0086] Further, the roll process using the pressing roll as described above has the
35
following advantages over the pressing system. Namely, (i) since the period of time
during which the mold and the coating film are brought in contact with each other in the
roll process is short, it is possible to prevent any deformation of pattern due to the
difference in coefficient of thermal expansion among the mold, the substrate, and a stage in
which the substrate is placed, etc.; (ii) the productivity is improved owing to the roll
process, and the productivity can be further improved by using the elongated film-shaped
substrate (film-shaped mold); (iii) it is possible to prevent the generation of bubbles of gas
in the pattern due to the humping of the solvent in the sol or to prevent any trace or mark of
gas from remaining; (iv) it is possible to reduce the transfer pressure and releasing force
(peeling force) owing to the line contact with the substrate (coating film), thereby making
it possible to easily handle a substrate with larger area; and (v) no bubble is included
during the pressing. Further, the producing method of the present invention uses the
flexible, film-shaped substrate as the mold. Therefore, in a case of transferring the
concave-convex pattern of the mold onto the sol-gel material layer formed on a relatively
hard substrate, the concave-convex pattern of the mold can be pressed to the sol-gel
material layer uniformly across the entire surface of the substrate. With this, the
concave-convex pattern of the mold can be transferred faithfully to the sol-gel material
layer, thereby making it possible to suppress any occurrence of lack of transfer, or any
occurrence of defect, etc.
I00871 In this transfer step, the film-shaped substrate may be pressed against the coating
film while the coating film being heated. As the method for heating the coating film, for
example, the heating may be performed via the pressing roll, or the coating film may be
heated directly or indirectly from the side of the substrate. In a case of performing the
heating via the pressing roll, a heating mechanism may be provided inside the pressing roll
(transfer roll), and any heating mechanism may be used. Although such a heating
mechanism that includes a heater inside the pressing roll is suitable, any separate heater
different from the pressing roll may be provided. In either case, any pressing roll may be
used, provided that the coating film can he pressed while being heated. The pressing roll
is preferably a roll having a heat-resisting coating film, which is provided on a surface
thereof and which is made of resin material such as ethylene-propylene-diene rubber
(EPDM), silicone rubber, nitrile rubber, fluoro rubber, acrylic rubber, chloroprene rubber,
etc. Further, a support roll may be provided to face the pressing roll and to sandwich the
substrate between the support roll and the pressing roll, or a support stand configured to
36
support the substrate may be provided, for the purpose of resisting the pressure applied by
the pressing roll.
[0088] A heating temperature at which the coating film is heated during the transfer can
be in a range of 40 degrees Celsius to 150 degrees Celsius. In a case of performing the
heating with the pressing roll, the heating temperature of the pressing roll can be similarly
in a range of 40 degrees Celsius to 150 degrees Celsius. By heating the pressing roll in
such a manner, the mold (film-shaped substrate) can be immediately released from the
coating film for which the transfer has been performed with the mold (film-shaped
substrate), thereby realizing an increased productivity. In a case that the heating
temperature of the coating film or the pressing roll is less than 40 degrees Celsius, the mold
cannot be expected to be released quickly from the coating film; in a case that the heating
temperature exceeds 150 degrees Celsius, the solvent used evaporate rapidly, which in turn
might result in the concave-convex pattern unsatisfactorily transferred. By performing
the transfer while heating the coating film, it is possible to expect the effect similar to that
obtained by pre-baking of the sol-gel material layer, as described below.
[0089] After the film-shaped substrate as the mold is pressed against the coating film
(sol-gel material layer), the coating film may be subjected to pre-baking. It is preferred to
perform the pre-baking in a case that the transfer is performed without heating the coating
film. The pre-baking promotes the gelation of the coating film to solidify the pattern,
thereby making the pattern be less likely to be collapsed during the releasing. In a case
that the pre-baking is performed, the heating is preferably performed at a temperature in a
range of 40 degrees Celsius to 150 degrees Celsius in the atmosphere.
[0090] The film-shaped substrate is released from the coating film (sol-gel material layer)
after the pressing step or the pre-baking step (step S5 in Fig. 5). Since the roll process is
used as described above, the releasing force may be smaller than that in a case of using a
plate-shaped mold employed in the pressing system, and it is possible to easily release the
mold (film-shaped substrate) from the coating film without leaving the coating film to be
remained on the mold (film-shaped substrate). In particular, since the transfer is
performed while heating the coating film, the reaction easily proceeds, and the mold can be
easily released from the coating film immediately after the transfer. Further, a releasing
roll (peeling roll) may be used for enhancing the releasability (peelability) of the mold.
As shown in Fig. 6, a peeling roll (releasing roll) 123 is provided on the downstream of the
pressing roll 122, and the film-shaped substrate 180a is supported by the rotating peeling
37
roll 123 while being urged by the peeling roll 123 toward the coating film 142. By doing
so, it is possible to maintain a state that the film-shaped substrate 180a is adhered to the
coating film 142 by a d~stancefr om the pressing roll 122 up to the peeling roll 123 (for a
predetermined period of time). Further, by changing the course of the film-shaped
substrate 180a such that the film-shaped substrate 180a is lifted upward to a position above
the peeling roll 123 at the downstream of the peeling roll 123, the film-shaped substrate
180a is peeled off kom the coating film 142. Note that the pre-baking andlor the heating
of the coating film described above may be performed during a penod of time when the
film-shaped substrate 180a is adhered to the coating film 142. Further, in a case of using
the peeling roll 123, the peeling off of the film-shaped substrate 180a Gom the coating film
can be performed more easily by performing the peeling while the coating film is heated,
for example, at a temperature in a range of 40 degrees Celsius to 150 degrees Celsius.
[0091] After the film-shaped substrate 180a is peeled off from the coating film (sol-gel
material layer) 142 on the substrate 140, the coating film 142 is subjected to the main
baking (step S6 in Fig. 5). The hydroxyl group and the like contained in sillca, etc.
tbrming the coating film is desorbed or eliminated by the main baking to further strengthen
the coating film. The main bakingmay be performed at a temperature in a range of 200
degrees Celsius to 1200 degrees Celsius for a duration of time about in a range of 5
minutes to 6 hours. In such a manner, the coating film is cured, and a substrate provided
with a concave-convex pattern film which corresponds to the concave-convex pattem of
the film-shaped substrate 180a is obtained, namely a substrate (diffraction grating) in
which the sol-gel material layer having the concave-convex pattern is directly formed on
the flat substrate is obtained. In this situation, in a case that the sol-gel material layer is
formed of silica, the sol-gel material layer is amorphous, crystalline or in a mixture state of
the amorphous and the crystalline, depending on the baking temperature and baking time.
[0092] Returning to Fig. 2(E), in a case that the replica 1 10 (or sol-gel structure) is to be
duplicated using the resin film structure 100, or in a case that yet another replica is to be
duplicated using the obtained replica 110 (or sol-gel structure), a film may be stacked or
deposited, on the surface of the resin film structure 100 or the replica 110 (or sol-gel
structure) having the concave-convex pattern formed thereon, by a gas phase method such
as the vapor deposition or sputtering method. By stacking the film as described above, in
a case that transfer etc. is performed with, for example, coating the surface of the stacked
film with the resin, the adhesion between the resin (for example, a UV curable resin) and
38
resin film structure 100 (the replica 110 or the sol-gel structure) can be lowered so as to
allow the master block to be peeled off more easily. Examples of the vapor-deposited
film include metals such as aluminum, gold, silver, platinum, and nickel; and metal oxides
such as aluminum oxide. Further, the thickness of such a vapor-deposited film is
preferably in a range of 5 nm to 500 nm. In a case that the thickness is less than the lower
limit, a uniform film is difficult to obtain, and thus that the effect of sufficiently lowering
the adhesion is decreased. In a case that the thickness exceeds the upper limit, the shape
of the master block is more likely to be blunt or dull. In a case that the cured resin layer
of the resin film structure 100 or the replica 110 is made of a UV curable resin, postcure
may be conducted as appropriate by, for example, performing the irradiation with
ultraviolet light again after the resin has been cured.
100931 Furthermore, in the steps shown in Figs. 2(B) and 2(D), the curable resins 80, 82
are applied on the supporting substrates 90,92, respectively. It is allowable, however, to
use a master block obtained by applying the curable resin directly on the surface of the
mold 70 which is the original master block or on the surface of the cured resin layer 80,
curing the applied curable resin and then detaching the cured curable resin. Alternatively,
instead of coating the surface of the master block with the resin, it is allowable to press the
master block to a coating film of the resin and to cure the resin so as to obtain a
concave-convex film which has concavities and convexities and formed of the cured resin,
and to use the obtained concave-convex film of the cured resin as the master block.
I00941
[Method for producing organic EL element]
Next, an explanation will be given about a method for producing an organic EL
element by using the resin film or the sol-gel structure, which is obtained as described
above, as the diffraction grating. Here, although an explanation will be given about a
method for producing an organic EL element by using a diffraction grating having a
concave-convex pattem formed with a sol-gel material on a surface thereof, in a case of
producing the organic EL element by using a diffraction grating formed of the resin film
structure 100, a similar process as the method using the diffraction grating having the
concave-convex pattern formed of the sol-gel material can be adopted. A substrate 140,
on which a pattem made of a sol-gel material layer (coating film) 142 formed via the roll
process explained with reference to Fig. 6, is prepared. At first, the substrate 140 is
cleaned with a brush, etc., in order to remove any foreign matter adhered to the substrate
39
140, and an organic matter, etc. is removed with an alkaline cleaning agent and an organic
solvent. Next, as shown in Fig. 7, a transparent electrode 93 is stacked on the sol-gel
material layer 142 on the substrate 140 so as to maintain the concave-convex structure
formed on the surface of the sol-gel material layer (coating film) 142. Examples of those
usable as the material for the transparent electrode 93 include indium oxide, zinc oxide, tin
oxide, indium-tin oxide (ITO) which is a composite material thereof; gold; platinum,
silver; copper, etc. Among these materials, IT0 is preferable from the viewpoint of the
transparency and the electrical conductivity. The thickness of the transparent electrode 93
is preferably within a range of 20 nm to 500 nm. In a case that the thickness is less than
the lower limit, the electrical conductivity is more likely to be insufficient. In a case that
the thickness exceeds the upper limit, there is possibility that the transparency is so
insufficient that the emitted EL light cannot be extracted to the outside sufficiently. As
the method for stacking the transparent electrode 93, it is possible to appropriately use any
known method such as the vapor deposition method, sputtering method, spin coating
method, etc. Among these methods, the sputtering method is preferably employed from
the viewpoint of improving adhesion property. Afterwards, the transparent electrode 93
is coated with photoresist, followed by being exposed with an electrode mask pattem.
Then, etching is performed with a developing solution, thereby obtaining a transparent
electrode having a pattem. Note that during the sputtering, the substrate is
exposed to a high temperature of about 300 degrees Celsius. After cleaning the obtained
transparent electrode with a brush and removing any organic matter, etc., with an alkaline
cleaning agent and an organic solvent, an UV ozone treatment is preferably performed.
[0095] Next, an organic layer 94 as shown in Fig. 7 is stacked on the transparent
electrode 93. The organic layer 94 is not particularly limited, provided that the organic
layer 94 is one usable as an organic layer of the organic EL element. As the organic layer
94, any known organic layer can be used as appropriate. Further, the organic layer 94
may be a stacked body of various organic thin films, and may be, for example, a stacked
body of a hole transporting layer 95, a light emitting layer 96, and an electron transporting
layer 97 as shown in Fig. 7. Here, examples of the material of the hole transporting layer
95 include aromatic diamine compounds such as phthalocyanine derivatives,
naphthalocyanine derivatives, porphyrin derivatives,
N,N'-bis(3-methylphenyl)-(l,l'-biphenyl)-4,4'-diamine (TPD), and
4,4'-bis[N-(naphthyltN-phenyl-amino]biphenyl(a-NPD); oxazole; oxadiazole; triazole;
40
imidazole; imidazolone; stilbene derivatives; pyrazoline derivatives; tetrahydroimidazole;
polyarylalkane; butadiene; and 4,4',4"-tris(N-(3-methylpheny1)N-phenylamino)
triphenylamine (m-MTDATA). The material of the hole transporting layer 95, however,
is not limited to these.
[0096] Further, the light emitting layer 96 is provided so that a hole injected from the
transparent electrode 93 and an electron injected from a metal electrode 98 are recombined
to emit light. Examples of the material usable as the light emitting layer 96 include:
metallo-organic complex such as anthracene, naphthalene, pyrene, tetracene, coronene,
perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene,
coumarin, oxadiazole, bisbenzoxazoline, bisstyryl, cyclopentadiene, and
aluminum-quinolinol complex (Alq3); tri-(p-terphenyl-4-y1)amine; 1 -aryl-2,5-di(2-thienyl)
pyrrole derivatives; pyran; quinacridone; rubren; distyrylbenzene derivatives; distyryl
arylene derivatives; distyryl amine derivatives; and various fluorescent pigments or dyes.
Furthermore, it is preferable that light-emitting materials selected kom the above
compounds are mixed as appropriate and then are used. Moreover, it is possible to
preferably use a material system generating emission of light from a spin multiplet, such as
a phosphorescence emitting material generating emission of phosphorescence, and a
compound including, in a part of the molecules, a constituent portion formed by the above
materials. Note that the phosphorescence emitting material preferably includes heavy
metal such as iridium. A host material having high canier mobility may be doped with
each of the light-emitting materials as a guest material to generate the light emission using
the dipole-dipole interaction (Forster mechanism) or electron exchange interaction (Dexter
mechanism). Examples of the material of the electron transporting layer 97 include
heterocyclic tetracarboxylic anhydrides such as nitro-substituted fluorene derivatives,
diphenylquinone derivatives, thiopyran dioxide derivatives, and naphthaleneperylene; and
metallo-organic complex such as carbodiimide, fluorenylidene methane derivatives,
anthraquino dimethane and anthrone derivatives, oxadiazole derivatives, and
aluminum-quinolinol complex (Alq3). Further, in the above-described oxadiazole
derivatives, it is also possible to use, as an electron transporting material, thiadiazole
derivatives in which oxygen atoms of oxadiazole rings are substituted by sulfur atoms and
quinoxaline derivatives having quinoxaline rings known as electron attractive group.
Furthermore, it is also possible to use a polymeric material in which the above materials
are introduced into a macromolecular chain or the above materials are made to be a main
41
chain of the macromolecular chain. Note that the hole transporting layer 95 or the
electron transporting layer 97 may also function as the light-emitting layer 96. In this
case, the organic layer between the transparent electrode 93 and the metal electrode 98 is
double-layered.
[0097] From the viewpoint of facilitating the electron injection from the metal electrode
98, a layer made of a metal fluoride or metal oxide such as lithium fluoride (LiF) or Li203,
a highly active alkaline earth metal such as Ca, Ba, or Cs, an organic insulating material, or
the like may be provided as an electron injection layer between the organic layer 94 and the
metal electrode 98. Further, from the viewpoint of facilitating the hole injection from the
transparent electrode 93, it is allowable to provide, between the organic layer 94 and the
transparent electrode 93, a layer made of triazol derivatives, oxadiazole derivative,
imidazole derivative, polyarylalkane derivatives, pyrazoline and pyrazolone derivatives,
phenylenediamine derivative, arylamine derivatives, amino-substituted calcone derivatives,
oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone
derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, or
electroconductive high-molecular oligomar, particularly thiophene oligomer, as a hole
injection layer.
[0098] Furthermore, in a case that the organic layer 94 is a stacked body formed of the
hole transporting layer 95, the light emitting layer 96 and the electron transporting layer 97,
the thicknesses of the hole transporting layer 95, the light emitting layer 96 and the
electron transporting layer 97 are preferably within a range of 1 nm to 200 nm, a range of 5
nm to 100 nm, and a range of 5 nm to 200 nm, respectively. As the method for stacking
the organic layer 94, any known method such as the vapor deposition method, sputtering
method, spin coating method and die coating method can be employed as appropriate.
100991 In the step for forming the organic EL element, subsequently, a metal electrode 98
is stacked on the organic layer 94, as shown in Fig. 7. Materials of the metal electrode 98
are not particularly limited, and a substance having a small work function can be used as
appropriate. Examples of the materials include aluminum, MgAg, MgIn, and AlLi. The
thickness of the metal electrode 98 is preferably within a range of 50 nm to 500 nm. In a
case that the thickness is less than the lower limit, the electrical conductivity is more likely
to be decreased. In a case that the thickness exceeds the upper limit, there is possibility
that the repair might be difficult to perform when any short circuit occurs between the
electrodes. Any known method such as the vapor deposition method, sputtering method,
42
etc. can be adopted to stack the metal electrode 98. Accordingly, an organic EL element
200 having a structure as shown in Fig. 7 can be obtained.
[0100] The organic EL element produced by using a diffraction grating formed of the
sol-gel material as described above is advantageous in the following points as compared
with an organic EL element produced by using a difiaction grating of which
concave-convex pattern is formed of a curable resin. Namely, since the sol-gel material
has excellent mechanical strength, any flaw or scratch, adhesion of any foreign matter,
generation of any projected portion on the transparent electrode during the production
process of the organic EL element are less likely to occur even in a case that the cleaning
with a brush is performed for the surface formed with the concave-convex pattern after the
formation of the substrate and the transparent electrode, thereby making is possible to
suppress any failure of the element which would be otherwise caused by the flaw, foreign
matter, projected portion, etc. Therefore, the organic EL element obtained by the method
of the present invention is more superior to that obtained by using the substrate made of the
curable resin, in view of the mechanical strength of the substrate having the
concave-convex pattern. Further, the substrate formed of the sol-gel material has
excellent chemical resistance, and thus has a relatively high corrosion resistance against the
alkaline solution, the organic solvent, etc. used in the cleaning step of the substrate and the
transparent electrode, thereby making it possible to use a variety of kinds of cleaning
solutions. Further, although the alkaline developing solution is used during the patterning
of substrate in some cases as described above, the substrate formed of the sol-gel material
has also chemical resistance against such a developing solution. In this respect, the
substrate formed of the sol-gel material is advantageous as compared with the substrate
formed of the curable resin of which chemical resistance to an alkaline solution is
relatively low. Furthermore, the substrate formed of the sol-gel material has excellent
heat resistance. Therefore, the substrate formed of the sol-gel material can withstand a
high temperature environment of the sputtering step in the process of forming transparent
electrode for the organic EL element. Further, the substrate formed of the sol-gel material
has UV resistance and weather resistance superior to those of the substrate made of the
curable resin, and thus also has the resistance against the UV ozone cleaning treatment
performed after the formation of transparent electrode.
[0101] In a case that the organic EL element produced by the method of the present
invention is used outdoors, any degradation due to the sunlight can be suppressed more
43
than in a case that an organic EL element produced by using the substrate formed of the
curable resin is used. Further, in a case that the curable resin as described above is left
under a high temperature environment for a long period of time due to the heat generation
during the light emission, the curable resin might be degraded to generate any yellowing,
any gas, etc., making any long term use of the organic EL element formed with the resin
substrate to be difficult. In the contrast, such degradation is suppressed in the organic EL
element provided with the substrate made of the sol-gel material.
EXAMPLES
[0102] In the following, the present invention will be specifically explained with
examples and comparative example. However, the present invention is not limited to the
following examples and comparative example.
[0103] At first, eleven kinds of block copolymers 1 to 11 manufactured by POLYMER
SOURCE, INC. (hereinafter referred to as "BCP-1" to "BCP-1 I", as appropriate) to be
used in Examples 1 and 2 were prepared. In each of the block copolymers, polystyrene
(hereinafter abbreviated as "PS" as appropriate) was used as the first polymer segment, and
used polymethyl methacrylate (hereinafter abbreviated as "PMMA" as appropriate) was
used as the second polymer segment. TABLE 1 as follows shows, for each of the block
copolymers 1 to 11, the number average molecular weight Mn of the block copolymer, the
number average molecular weight Mn of the PS segment and the number average
molecular weight Mn of the PMMA segment as Mn (BCP), Mn (PS) and Mn(PMMA),
respectively. TABLE 1 also shows, for each of the block copolymers 1 to 11, the volume
ratio between the PS segment and the PMMA segment (PS:PMMA) and the molecular
weight distribution (MwIMn) of the block copolymer, and Tg (glass transition temperature)
of each of the PS and PMMA segments as well. The volume ratio between the first
polymer segment and second polymer segment (the first polymer segment: the second
polymer segment) in each of the block copolymers was calculated on the assumption that
the density of polystyrene was 1.05 .g/cm3 and the density of polymethyl methacrylate was
1.19 g/cm3. The number average molecular weights (Mn) and the weight average
molecular weights (Mw) ofipolymer segments or polymers were measured by using a gel
permeation chromatography (Model No: "GPC-8020" manufactured by TOSOH
CORPORATION, in which TSKgel SuperH1000, SuperH2000, SuperH3000, and
44
SuperH4000 were connected in series). The glass transition temperatures (Tg) of the
polymer segments were measured by using a differential scanning calorimeter
(manufactured by PERKIN-ELMER, INC. under the product name of "DSC7"), while the
temperature was raised at a rate of temperature rise of 20 degrees Celsiuslmin over a
temperature range of 0 degrees Celsius to 200 degrees Celsius. The solubility parameters
of polystyrene and polymethyl methacrylate were 9.0 and 9.3, respectively (see "Kagaku
Binran Ouyou Hen" (Handbook of Chemistry, Applied Chemistry), 2nd edition).
[0104]
[TABLE 11
[OlOS]
[Example 11
Toluene was added to 150 mg of the block copolymer 1 and 37.5 mg of
Polyethylene Glycol 2050 manufactured by ALDRICH (average Mn = 2050) as
polyethylene oxide so that the total amount thereof was 15 g, followed by dissolution.
The physical property of the block copolymer 1 (hereinafter abbreviated as "BCP-I " as
appropriate) is shown in TABLE 1.
[0106] Then, the solution of the block copolymer was filtered through a membrane filter
having a pore diameter of 0.5 pm to obtain a block copolymer solution. A glass substrate
was coated with a mixed solution containing 1 g of KBM-5103 manufactured by
SHTN-ETSU SILICONE (SHIN-ETSU CHEMICAL, CO., LTD.), 1 g of ion-exchanged
water, 0.1 ml of acetic acid and 19 g of isopropyl alcohol, by the spin coating (which was
performed for 10 seconds with rotation speed of 500 rpm, and then performed for 45
seconds with rotation speed of 800 rpm). Then, the heating was performed for 15 minutes
at 130 degrees Celsius, and thus a silane-coupling treated glass was obtained. The
silane-coupling treated glass as the base member was coated with the obtained block
copolymer solution by the spin coat with a film thickness in a range of 150 nm to 170 nrn.
The spin coat was performed for 10 seconds with a rotation speed of 200 rpm and then was
performed for 30 seconds at a rotation speed of 300 rpm.
[0107] Then, the base member on which the thin film was formed was stationarily placed
in a desiccator, filled in advance with chloroform vapor, at a room temperature for 24 hours
to thereby apply the solvent annealing process for the base member. Inside the desiccator
(volume: 5 L), a screw-type container charged with 100 g of chloroform was placed, and
the atmosphere inside the desiccator was filled with chloroform at the saturated vapor
pressure. Concavities and convexities were observed on the surface of the thin film after
the solvent annealing process, and it was found that the block copolymer composing the
thin film underwent the micro phase separation. The cross section of the thin film was
observed by a transmission electron microscope (TEM; model name: H-7100FA
manufactured by HITACHI, LTD.). Fig. 8A shows a photograph of the observed cross
section of the thin film and Fig. 8B shows an enlarged image of the photograph of Fig. 8A.
Since a portion of PS (PS portion) was dyed with Ru04 in advance, the PS portion was
photographed to be dark (dark gray) and a portion of PMMA (PMMA portion) was
photographed to be light (light gray), as shown in Fig. 8B. From the photos of the
observed cross section, the cross section of the PS portion, which is circular, was aligned in
two tiers (stages or rows) in a direction perpendicular to the surface of the substrate (height
direction) while the circular cross sections of the PS portion are separated from each other
in a direction parallel to the surface of the substrate. When considering together with an
analysis image obtained by an atomic force microscope (to be described later on), it is
appreciated that the PS portion is phase-separated from the PMMA portion so as to
generate a horizontal cylinder structure. This is a state in which the PS portion as the core
(island) is surrounded by the PMMA portion (sea). Although the reason for this
46
phenomenon is not clear, it is considered as follows. Namely, chloroform as the solvent is
a good solvent to both of PS and PMMA, but is better solvent to the PMMA. Therefore,
the portion of PMMA swelled to a greater extent than the portion of PS, and thus resulted
in the formation of phase separation structure in which a block copolymer has the volume
ratio deviating from 5 5 . Further, it is also apparent that the surface of the thin film has a
wave-like shape reflecting the presence of the PS portion separated with the PMMA
portion sandwiched therebetween.
[0108] In order to investigate the relationship between the concentration of the block
copolymer in the block copolymer solution and the inner structure of the thin film, the
concentration of the block copolymer 1 in the block copolymer solution was lowered until
the concentration was 0.5%, then a thin film was formed on the substrate in a similar
manner as described above, and the solvent annealing process was performed. Fig. 8C
shows the structure of the cross section of the thin film observed by the transmission
electron microscope, and Fig. 8D is an enlarged image of the cross sectional structure of
Fig. 8C. Although the horizontal cylinder structure was maintained, the horizontal
cylinder structure was aligned in one tier (row or stage) in the height direction due to the
lowered concentration of the block copolymer. Further, also in Fig. 8D, it is also
appreciated that the surface of the thin film has a wave-like shape reflecting the presence of
the PS portion separated with the PMMAportion sandwiched therebetween. Note that in
Figs. 8A to 8D, a portion seen as a deep black portion on the surface of the thin film is a
shadow of a protective film coated for the purpose of cutting the thin film, and is not a
component of the thin film itself.
[0109] About 20 nm of a thin nickel layer was formed as a current seed layer by
performing a sputtering on the surface of the thin film processed to have the wave-like
shaped by the solvent annealing process. Subsequently, the base member with the thin
film was immersed in a nickel sulfamate bath and subjected to an electroforming process
(maximum current density: 0.05 A/cm2) at a temperature of 50 degrees Celsius so as to
precipitate nickel until the thickness of nickel became 250 pm. The base member with
the thin film was mechanically peeled off or released from the nickel electroforming body
obtained in such a manner. Subsequently, polymer component(s) adhered to a part of the
surface of the electroforming body was (were) removed by repeating the following process
three times. Namely, the nickel electroforming body was immersed in a tetrahydrofuran
solvent for 2 hours; then the nickel electroforming body was coated with an acrylic-based
47
IJV curable resin; and the acrylic-based UV curable resin, with which the nickel
electroforming body is coated, was cured; and then the cured resin was peeled off. After
that, the nickel electroforming body was immersed in Chemisol 2303 manufactured by
THE JAPAN CEE-BEE CHEMICAL CO., LTD., and was cleaned while being stirred for 2
hours at 50 degrees Celsius. Thereafter, the UV ozone treatment was performed for the
nickel electroforming body for 10 minutes.
[0110] Subsequently, the nickel electroforming body was immersed in HD-2101TH
manufactured by DAIKIN CHEMICAL. SALES, CO., LTD. for about 1 minute and was
dried, and then stationarily placed overnight. The next day, the nickel electrofonning
body was immersed in HDTH manufactured by DAIKIN CHEMICAL SALES, CO., LTD.
and was subjected to an ultrasonic cleaning process for about 1 minute. In such a manner,
a nickel mold for which a mold-release treatment had been performed was obtained.
[Olll] Subsequently, a PET substrate (COSMOSHINE A-4100 manufactured by
TOYOBO CO., LTD.) was coated with a fluorine-based UV curable resin. Then, the
fluorine-based UV curable resin was cured by being irradiated with ultraviolet light at 600
m~lcmw~hi le the nickel mold was pressed to the PET substrate. After curing of the resin,
the nickel mold was peeled off or released from the cured resin. In such a manner, a
diffraction grating made of the PET substrate with the resin film to whlch the surface
profile (surface shape) of the nickel mold was transferred was obtained.
[0112] An analysis image of the concave-convex shape on the surface of the thin film,
which was made to have the wave-like shape by the solvent annealing process (at a stage
before the electrofonning), was observed by using an atomic force microscope (a scanning
probe microscope equipped with an environment control unit "Nanonavi I1
StatiodE-sweep" manufactured by Hitachi High Tech Science Corporation). Analysis
conditions of the atomic force microscope were as follows:
Measurement mode: dynamic force mode
Cantilever: SI-DF40P2 (material: Si, lever width: 40 pm, diameter of tip of chip:
10 nm)
Measurement atmosphere: in air
Measurement temperature: 25 degrees Celsius
[0113] Fig. 9A shows a concavity and convexity analysis image of the surface of the thin
film. Further, Fig. 9B shows a concavity and convexity analysis image of the cross
section at a portion in the vicinity of the surface of the concave-convex structure of the thin
48
film (showing the cross section along a line in Fig. 9A). From the cross-sectional
structure in Fig. 98, it is appreciated that smooth concavities and convexities are formed
on the surface. Note that the full scale of the vertical axis is 160 nm (this is similarly
applied to other concavity and convexity analysis image of the cross section). From the
concavity and convexity analysis image of the surface of the thin film shown in each of
Figs. 9A and 9B, a Fourier transformed image, the average pitch of concavities and
convexities, the average value of depth distribution of concavities and convexities, the
standard deviation of the depth of concavities and convexities, and the kurtosis of
concavities and convexities were obtained in the following manners, respectively.
[0114]
[Fourier-transformed image]
Concavity and convexity analysis images were obtained in the above-described
manner, by performing a measurement in a randomly selected measurement region of 3 pn
square (length: 3 pm, width: 3 pm) in the diffiaction grating. The obtained concavity and
convexity analysis images were subjected to a flattening process including primary
inclination correction, and then to two-dimensional fast Fourier transform processing.
Thus, a Fourier-transformed image was obtained. Fig. 9C shows the obtained
Fourier-transformed image. As is apparent from the result shown in Fig. 9C, it was
confirmed that the Fourier-transformed image showed an annular pattern substantially
centered at an origin at which an absolute value of wavenumber was 0 pm", and that the
annular pattem was present within a region where the absolute value of wavenumber was
within a range of not more than 10 pm-'.
[0115] The circular pattern of the Fourier-transformed image is a pattem observed due to
gathering of bright spots in the Fourier-transformed image. The term "circular" herein
means that the pattern of the gathering of the bright spots looks like a substantially circular
shape, and is a concept further including a case where a part of the contour looks like a
convex shape or a concave shape. The pattern formed by the gathering of bright spots
may look like a substantially annular shape in some cases, and such cases are expressed
with the term "annular". It is noted that the term "annular" is a concept further including
a case where a shape of an outer circle or inner circle of the ring looks like a substantially
circular shape and further including a case where a part of the contours of the outer circle
and/or the inner circle of the ring looks like a convex shape or a concave shape. Further,
the phrase "the circular or annular pattern is present within a region where an absolute
49
value of wavenumber is within a range of not more than 10 pm-' (more preferably in a
range of 1.25 pm-' to 10 pm-', further preferably from in a range of 1.25 pm-' to 5 pm-I)"
means that not less than 30% (more preferably not less than 50%, further more preferably
not less than SO%, and particularly preferably not less than 90%) of the bright spots
forming the Fourier-transformed image are present within a region where the absolute
value of wavenumber is within a range of not more than 10 pm-' (more preferably in a
range of 1.25 pm-' to 10 pm-I, and further preferably in a range of 1.25 pm-' to 5 pm-I).
[0116] The two-dimensional fast Fourier transform processing onthe concavity and
convexity analysis image can be easily performed by electronic image processing using a
computer equipped with software for two-dimensional fast Fourier transform processing.
[0117]
[Average pitch of concavities and convexities]
A concavity and convexity analysis image was obtained in the manner described
above by performing a measurement in a randomly selected measurement region of 3 pm
square (length: 3 pm, width: 3 pm) in the diMaction grating. Spacing distances between
randomly selected concave or convex portions which were adjacent to each other were
measured at not less than 100 points in the concavity and convexity analysis image, and the
average of the spacing distances was calculated as the average pitch of the concavities and
convexities. The average pitch of the concavity and convexity pattern obtained by the
analysis image in this example was 73.5 nm.
[Ol18]
[Average value of depth distribution of concavities and convexities]
A concavity and convexity analysis image was obtained by performing a
measurement in a randomly selected measurement region of 3 pm square (length: 3 pm,
width: 3 pm) in the thin film. When doing so, data of height of concavities and
convexities at not less than 16,384 points (vertical: 128 points x horizontal: 128 points)
was obtained within the measurement region, each in nanometer scale. By using the
E-sweep in this example, the measurement was performed at 65,536 points (vertical: 256
points x horizontal: 256 points, namely the measurement at a resolution of 256 pixels) in
the measurement region of 3 pm square. With respect to the height of concavities and
convexities (nm) measured in such a manner, at first, a measurement point P is determined,
among all the measurement points, which is the highest from the surface of the substrate.
Then, a plane which includes the measurement point P and which is parallel to the surface
50
of the substrate is determined as a reference plane (horizontal plane), and a depth value
from the reference plane (difference obtained by subtracting, from the value of height from
the substrate at the measurement point P, the height from the substrate at each of the
measurement points) was obtained as the data of depth of concavities and convexities.
Note that such a depth data of the concavities and convexities can be obtained by
performing automatic calculation with software in the E-sweep, and the value obtained by
the automatic calculation in such a manner can be utilized as the data of depth of
concavities and convexities. After obtaining the data of depth of concavity and convexity
at each of the measurement points in this manner, the average value (m) of the depth
distribution of concavities and convexities can be obtained by performing calculation with
the expression (I) described above. The average value (m) of the depth distribution of
concavities and convexities of the diffraction grating obtained in this example was 20.6
nm.
[0119]
[Standard deviation of depth of concavities and convexities]
In a similar manner to the method for measuring the average value (m) of the
depth distribution of concavities and convexities as described above, the data of depth of
concavities and convexities are obtained by performing a measurement at not less than
16,384 measurement points (vertical: 128 points x horizontal: 128 points) in a randomly
selected measurement region of 3 pm square. In this example, measurement points of
65,536 points (vertical: 256 points x horizontal: 256 points) were adopted. Then, the
average value (m) of the depth distribution of concavities and convexities and the standard
deviation (o) of depth of concavities and convexities are calculated based on the data of the
depth of concavities and convexities at each of the measurement points. Note that the
average value (m) of the depth distribution of concavities and convexities can be obtained
by performing the calculation (I) described above. On the other hand, the standard
deviation (o) of depth of concavities and convexities can be obtained by performing the
following calculation (11):
[OlZO]
[Formula 11]
[in the formula (II), "N" represents the total number of measurement points (total pixel
count), "xi" represents data of depth of concavity and convexity at an i-th measurement
point, and "m" represents the average value of depth distribution of concavities and
convexities].
The standard deviation (o) of depth of concavities and convexities of the thin film
was 18.2 nm.
go1211
[Kurtosis of concavities and convexities]
In a similar manner as described above, the data of depth of concavities and
convexities are obtained by performing a measurement in a randomly selected
measurement region of 3 pm square at not less than 16,384 measurement points (vertical:
128 points x horizontal: 128 points). In this example, measurement points of 65,536
points (vertical: 256 points x horizontal: 256 points) were adopted. Then, the average
value (m) of the depth distribution of concavities and convexities and the standard
deviation (cs) of depth of concavities and convexities are calculated based on the data of the
depth of concavity and convexity at each of the measurement points in a manner similar to
that described above. Based on the average value (m) of the depth distribution of
concavities and convexities and the value of the standard deviation (n) of depth of
concavities and convexities which have been obtained in such a manner, the kurtosis (k)
can be obtained by performing the following calculation (111):
[0122]
[Formula 1111
[in the formula (111), "N" represents the total number of measurement points (total pixel
count), "xi" represents data of depth of concavity and convexity at an i-th measurement
point, "m" represents the average value of depth distribution of concavities and convexities,
52
and (0) represents the value of the standard deviation of depth of concavities and
convexities].
[0123] In the diffraction grating of the present invention, it has been found, through the
experiments previously performed by the applicant of the present application (see, for
example, W02011/007878Al of the applicant of the present application), that the kurtosis
of the concavities and convexities formed on the surface of the thin film is preferably not
less than -1.2, more preferably in a range of -1.2 to 1.2, further more preferably in a range
of -1.2 to 1, and particularly preferably in a range of -1.1 to 0.0. In a case that the kurtosis
as described above is less than the lower limit, there is a tendency that when the diffraction
grating is used in the organic EL element, the occurrence of leak current is hard to be
suppressed sufficiently. On the other hand, in case that the kurtosis exceeds the upper
limit, there are hardly any concavities and convexities in the cross-sectional shape of the
thin film and only provides a state that projection portions or recessed portions are present
only sparsely, which in turn makes it hard to sufficiently improve the light extraction
efficiency as the characteristic of the concave-convex structure (hard to obtain any
sufficient diffraction effect). In addition, the electric field easily concentrates to the
projection portions, and the leak current tends to generated. In a case that the kurtosis (k)
is not less than -1.2, there is no extremely pointed portions in the cross-sectional shape of
the concave-convex structure, and the concavities and convexities form a smooth
wave-like shape regardless of the height and pitch of concavities and convexities of the
wave-like shape and regardless of whether the shape of the surface is regular or irregular.
In a case that this is used for the production of organic EL element and that an organic
layer is vapor-deposited on the surfaces of the concavities and convexities, it is considered
that the thickness of a portion of the organic layer can be prevented from becoming
extremely thin, and the organic layer can be stacked with a sufficiently uniform thickness.
As a result, the distance between the electrodes can be sufficiently uniform, thereby
making it possible to sufficiently prevent any concentration of the electric field. Further,
it is considered that the gradient of the electric potential distribution in the organic EL
element is smooth at an inclined portion of the wave-like shape of the concave-convex
structure, and thus the occurrence of leak current can be sufficiently suppressed. The
kurtosis of the concavities and convexities of the diffraction grating obtained in Example 1
was -0.67.
[0124]
53
[Example 21
In Example 2, observation was made as to how the concave-convex structure of
the thin film afler the solvent annealing process changed, by varying the number average
molecular weight (Mn) of the block copolymer and the ratio between the PS portion and
PMMA portion composing the block copolymer. As the block copolymer, block
copolymer 1 (BCP-1) to block copolymers 11 (BCP-11) respectively having the physical
properties as shown in TABLE 1 were used, and a silane-coupling treated glass base
member was coated with a solution of the block copolymer, followed by being dried and
subjected to the solvent annealing process in a similar manner to that in Example 1, but
Example 2 was different from Example 1 in that the blending amount of polyethylene
oxide was changed to be 30 parts by mass relative to 100 parts by mass of the block
copolymer. An analysis image of the concave-convex shape of the surface of the thin
film after having been subjected to the solvent annealing process was observed with an
atomic force microscope, under a similar analysis condition to that in Example 1. The
physical properties of the used block copolymers 1 to 11 (BCP-1 to BCP-I 1) are as shown
in TABLE 1, and the results of observation of the thin films each obtained by using one of
the block copolymers are indicated below.
(01251
[Block Copolymer 1 (BCP-I)]
Although the block copolymer 1 was similar to that used in Example 1, the block
copolymer solution in Example 2 contained polyethylene oxide in a blending amount
higher than in Example 1. From a concavity and convexity analysis image (not shown) of
the cross section at a portion in the vicinity of the surface of the thin film obtained by the
solvent annealing process, it was appreciated that the shape of concavities and convexities
was clearer than that of Example 1. This is considered due to the difference in blending
amount of polyethylene oxide. The effect of the blending amount of polyethylene oxide
on the height of concavities and convexities will be described in detail in Example 5.
According to the calculation performed for the surface of the thin film with the E-sweep
based on the concavity and convexity analysis image, the average value of the depth
distribution of concavities and convexities was 78.1 nm, the average pitch of concavities
and convexities was 305 nm, and the standard deviation of the depth of concavities and
convexities was 24.7 nm. It was confirmed that the Fourier-transformed image showed
an annular pattern substantially centered at an origin at which an absolute value of
54
wavenumber was 0 pm-I, and that the annular pattern was present within a region where an
absolute value of wavenumber was within a range of not more than 10 pm-'. The kurtosis
of concavities and convexities was -0.63.
[0126]
[Block Copolymer 2 (BCP-2)]
Although the number average molecular weight (Mn) of the block copolymer 2
exceeded 500,000, the number average molecular weights (Mn) of the PS portion and
PMMA portion composing the block copolymer 2 were 270,000 and 289,000, respectively,
which were considerably lower than those in Example 1. Further, a ratio PS:PMMA as
the ratio between the PS portion and the PMMA portion was 51 :49. From a concavity
and convexity analysis image (not shown) of the cross section at a portion in the vicinity of
the surface of the thin film obtained by the solvent annealing process, it was appreciated
that the height of concavities and convexities was considerably lower than that of Example
1. According to the calculation performed for the surface of the thin film with the
E-sweep based on the concavity and convexity analysis image, the average value of the
depth distribution of concavities and convexities was 22.5 nm, the average pitch of
concavities and convexities was 162 nm, and the standard deviation of the depth of
concavities and convexities was 10.1 nm. It was confirmed that the Fourier-transformed
image showed an annular pattern substantially centered at an origin at which an absolute
value of wavenumber was 0 pm-', and that the annular pattern was present within a region
where an absolute value of wavenumber was within a range of not more than 10 pm-I.
The kurtosis of concavities and convexities was -1.01.
[0127]
[Block Copolymer 3 (BCP-3)]
The number average molecular weight (Mn) of the block copolymer 3 was
1,010,000, wherein the number average molecular weights (Mn) of the PS portion and
PMMA portion composing the block copolymer 3 were 510,000 and 500,000, respectively.
Further, a ratio PS:PMMA as the ratio between the PS portion and the PMMA portion was
54:46 that was same as the ratio in Example 1. From a concavity and convexity analysis
image (not shown) of the cross section at a portion in the vicinity of the surface of the thin
film obtained by the solvent annealing process, it was appreciated that the concavities and
convexities on the surface was smooth similarly to that in Example 1. According to the
calculation performed for the surface of the thin film with the E-sweep based on the
55
concavity and convexity analysis image, the average value of the depth distribution of
concavities and convexities was 47.1 nm, the average pitch of concavities and convexities
was 258 nm, and the standard deviation of the depth of concavities and convexities was
18.0 nm. It was confirmed that the Fourier-transformed image showed an annular pattern
substantially centered at an origin at which an absolute value of wavenumber was 0 pnY',
and that the annular pattern was present within a region where an absolute value of
wavenumber was within a range of not more than 10 pm-'. The kurtosis of concavities
and convexities was -0.95.
[0128]
[Block Copolymer 4 (BCP-4)]
The number average molecular weight (Mn) of the block copolymer 4 was
1,160,000, wherein the number average molecular weights (Mn) of the PS portion and
PMMA portion composing the block copolymer 4 were 590,000 and 570,000, respectively.
Further, a ratio PS:PMMA as the ratio between the PS portion and the PMMA portion was
54:46 that was same as the ratio in Example 1. From a concavity and convexity analysis
image (not shown) of the cross section at a portion in the vicinity of the surface of the thin
film obtained by the solvent annealing process, it was appreciated that the concavities and
convexities on the surface was generally smooth, although there were some projection at a
portion of the concavities and convexities on the surface. According to the calculation
performed for the surface of the thin film with the E-sweep based on the concavity and
convexity analysis image, the average value of the depth distribution of concavities and
convexities was 80.1 nm, the average pitch of concavities and convexities was 278 nm, and
the standard deviation of the depth of concavities and convexities was 31.2 nm. It was
confirmed that the Fourier-transformed image showed an annular pattern substantially
centered at an origin at which an absolute value of wavenumber was 0 pm-', and that the
annular pattern was present within a region where an absolute value of wavenumber was
within a range of not more than 10 pm-'. The kurtosis of concavities and convexities was
-1.06.
[0129]
[Block Copolymer 5 (BCP-5)]
The number average molecular weight (Mn) of the block copolymer 5 was
1,600,000, wherein the number average molecular weights (Mn) of the PS portion and
PMMA portion composing the block copolymer 5 were 700,000 and 900,000, respectively.
56
Further, a ratio PS:PMMA as the ratio between the PS portion and the PMMA portion was
47:53. From a concavity and convexity analysis image (not shown) of the cross section at
a portion in the vicinity of the surface of the thin film obtained by the solvent annealing
process, it was appreciated that the concavities and convexities on the surface was smooth.
According to the calculation performed for the surface of the thin film with the E-sweep
based on the concavity and convexity analysis image, the average value of the depth
distribution of concavities and convexities was 53.7 nm, the average pitch of concavities
and convexities was 315 nm, and the standard deviation of the depth of concavities and
convexities was 18.0 nm. It was confirmed that the Fourier-transformed image showed
an annular pattern substantially centered at an origin at which an absolute value of
wavenumber was 0 pm-I, and that the annular pattem was present within a region where an
absolute value of wavenumber was within a range of not more than 10 pm-I. The kurtosis
of concavities and convexities was -0.33.
[0130]
[Block Copolymer 6 (BCP-6)]
The number average molecular weight (Mn) of the block copolymer 6 was
1,725,000, wherein the number average molecular weights (Mn) of the PS portion and
PMMA portion composing the block copolymer 6 were 868,000 and 857,000, respectively.
Further, a ratio PS:PMMA as the ratio between the PS portion and the PMMA portion was
53:47. From a concavity and convexity analysis image (not shown) of the cross section at
a portion in the vicinity of the surface of the thin film obtained by the solvent annealing
process, it was appreciated that the concavities and convexities on the surface was smooth.
According to the calculation performed for the surface of the thin film with the E-sweep
based on the concavity and convexity analysis image, the average value of the depth
distribution of concavities and convexities was 72.9 nm, the average pitch of concavities
and convexities was 356 nm, and the standard deviation of the depth of concavities and
convexities was 19.9 nm. It was confirmed that the Fourier-transformed image showed
an annular pattem substantially centered at an origin at which an absolute value of
wavenumber was 0 pm-', and that the annular pattern was present within a region where an
absolute value of wavenumber was within a range of not more than 10 pm-I. The kurtosis
of concavities and convexities was -0.09.
[0131]
[Block Copolymer 7 (BCP-7)]
The number average molecular weight (Mn) of the block copolymer 7 was
1,120,000, wherein the number average molecular weights (Mn) of the PS portion and
PMMA portion composing the block copolymer 7 were 700,000 and 420,000, respectively.
Further, a ratio PS:PMMA as the ratio between the PS portion and the PMMA portion was
65:35. From a concavity and convexity analysis image (not shown) of the cross section at
a portion in the vicinity of the surface of the thin film obtained by the solvent annealing
process, it was appreciated that the concavities and convexities on the surface hardly
appeared. According to the calculation performed for the surface of the thin film with the
E-sweep based on the concavity and convexity analysis image, the average value of the
depth distribution of concavities and convexities was 5.0 nm, which was extremely low,
and the standard deviation of the depth of concavities and convexities was 1.4 nm. The
average pitch of concavities and convexities could not be measured. It was confirmed
that the Fourier-transformed image showed a circular pattern substantially centered at an
origin at which an absolute value of wavenumber was 0 pf', and that the circular pattern
was present within a region where an absolute value of wavenumber was within a range of
not more than 10 pfl. The kurtosis of concavities and convexities was -0.33.
[0132]
[Block Copolymer 8 (BCP-8)]
The number average molecular weight (Mn) of the block copolymer 8 was
1,350,000, wherein the number average molecular weights (Mn) of the PS portion and
PMMA portion composing the block copolymer 8 were 1,200,000 and 150,000,
respectively. Further, a ratio PS:PMMA as the ratio between the PS portion and the
PMMA portion was 90:lO. From a concavity and convexity analysis image (not shown)
of the cross section at a portion in the vicinity of the surface of the thin film obtained by
the solvent annealing process, it was appreciated that the concavities and convexities
slightly appeared on the surface of the thin film. According to the calculation performed
for the surface of the thin film with the E-sweep based on the concavity and convexity
analysis image, the average value of the depth distribution of concavities and convexities
was 36.9 nm, and the standard deviation of the depth of concavities and convexities was
5.6 nm. The average pitch of concavities and convexities could not be measured. It was
confirmed that the Fourier-transformed image showed a circular pattern substantially
centered at an origin at which an absolute value of wavenumber was 0 pm-', and that the
circular pattern was present within a region where an absolute value of wavenumber was
58
within a range of not more than 10 pm-'. The kurtosis of concavities and convexities was
2.29.
[0133]
[Block Copolymer 9 (BCP-9)]
The number average molecular weight (Mn) of the block copolymer 9 was
1,756,000, wherein the number average molecular weights (Mn) of the PS portion and
PMMA portion composing the block copolymer 9 were 556,000 and 1,200,000,
respectively. Further, a ratio PS:PMMA as the ratio between the PS portion and the
PMMA portion was 34:66. From a concavity and convexity analysis image (not shown)
of the cross section at a portion in the vicinity of the surface of the thin film obtained by
the solvent annealing process, the concavities and convexities slightly appeared on the
surface of the thin film. According to the calculation performed for the surface of the thin
film with the E-sweep based on the concavity and convexity analysis image, the average
value of the depth distribution of concavities and convexities was 35.7 nm, and the
standard deviation of the depth of concavities and convexities was 14.5 nm. The average
pitch of concavities and convexities could not be measured. It was confirmed that the
Fourier-transformed image showed a circular pattern substantially centered at an origin at
which an absolute value of wavenumber was 0 pm-', and that the circular pattern was
present within a region where an absolute value of wavenumber was within a range of not
more than 10 pm-'. The kurtosis of concavities and convexities was 0.03.
[0134]
[Block Copolymer 10 (BCP-lo)]
The number average molecular weight (Mn) of the block copolymer 10 was
995,000, wherein the number average molecular weights (Mn) of the PS portion and
PMMA portion composing the block copolymer 10 were 3 15,000 and 680,000,
respectively. Further, a ratio PS:PMMA that is a ratio between the PS portion and the
PMMA portion was 34:66. From a concavity and convexity analysis image (not shown)
of the cross section at a portion in the vicinity of the surface of the thin film obtained by
the solvent annealing process, the concavities and convexities slightly appeared on the
surface of the thin film. According to the calculation performed for the surface of the thin
film with the E-sweep based on the concavity and convexity analysis image, the average
value of the depth distribution of concavities and convexities was 3 1.3 nm, and the
standard deviation of the depth of concavities and convexities was 8.5 nm. The average
59
pitch of concavities and convexities could not be measured. It was confirmed that the
Fourier-transformed image showed a circular pattem substantially centered at an origin at
which an absolute value of wavenumber was 0 pm-', and that the circular pattern was
present within a region where an absolute value of wavenumber was within a range of not
more than 10 pm-I. The kurtosis of concavities and convexities was -0.13.
[0135]
[Block Copolymer 11 (BCP-I I)]
The number average molecular weight (Mn) of the block copolymer 1 1 was
263,000, wherein the number average molecular weights (Mn) of the PS portion and
PMMA portion composing the block copolymer 1 l were 133,000 and 130,000,
respectively. Further, a ratio PS:PMMA as the ratio between the PS portion and the
PMMA portion was 54:46. From a concavity and convexity analysis image (not shown)
of the cross section at a portion in the vicinity of the surface of the thin film obtained by
the solvent annealing process, it was appreciated that the concavities and convexities on
the surface were small. According to the calculation performed for the surface of the thin
film with the E-sweep based on the concavity and convexity analysis image, the average
value of the depth distribution of concavities and convexities was 17.7 nm, the average
pitch of concavities and convexities was 87 nm, and the standard deviation of the depth of
concavities and convexities was 4.8 nrn. It was confirmed that the Fourier-transformed
image showed an annular pattern substantially centered at an origin at which an absolute
value of wavenumber was 0 pY', and that the annular pattern was present within a region
where an absolute value of wavenumber was within a range of not more than 15 pm-'.
The kurtosis of concavities and convexities was 1.4.
101361 According to the concavity and convexity analysis images, the average values of
depth distribution of concavities and convexities and the standard deviation values of the
depth of concavities and convexities on the surface of the thin film regarding the block
copolymers 1 to 11, it is appreciated that when the number average molecular weight of the
block copolymer is less than 500,000, the concave-convex surface hardly appears, that the
number average molecular weight of the block copolymer is preferably at least not less
than 500,000, and is particularly preferably not less than 1,000,000 in view of the height of
concavities and convexities. Further, it is appreciated that when a ratio PS:PMMA as the
ratio between the PS portion and the PMMA portion is outside the range of 40:60 to 60:40
as in the block copolymers 7 to 10, the height of concavities and convexities becomes low.
60
[0137]
[Example 31
In Example 3, observation was made as to how the concave-convex structure of
the thin film changed, by varying the time (time period) during which the solvent annealing
process was performed. As the block copolymer, the block copolymer 1 (BCP-I) which
was used in Example 1, was used, and a silane-coupling treated glass base member was
coated with a solution of the block copolymer, followed by being dried and subjected to the
solvent annealing process with chloroform in a similar manner to that in Example 1, but
Example 3 was different from Example 1 in that the solvent annealing processing time was
changed to be 1 hour, 3 hours, 6 hours, 12 hours, 48 hours and 168 hours. An analysis
image of the concave-convex shape of the surface of the thin film after having been
subjected to the solvent annealing process was observed with an atomic force microscope
for each of the processing time periods, under a similar analysis condition to that in
Example 1. TABLE 2 as follows shows the average values of the depth distribution of
concavities and convexities (average of concavities and convexities) on the surface of the
thin film, the standard deviation values of the depth of concavities and convexities and the
kurtosis values of the concavities and convexities which were calculated with the E-sweep
based on these analysis images. It was confirmed that the Fourier-transformed image
showed an annular pattern substantially centered at an origin at which an absolute value of
wavenumber was 0 pm-', and that the annular pattern was present within a region where an
absolute value of wavenumber was within a range of not more than 10 pm-' with respect to
the film formed with each of these processing time periods. Note that the processing time
is preferably in a range of 6 hours to 168 hours, in view of the average value of the depth
distribution of concavities and convexities.
[0138]
[TABLE 21
concavities and
Kurtosis -0.13 0.76 0.12 -0.47 -0.67 -0.81 -0.14
[0139] From the results shown in TABLE 2, it is appreciated that as the solvent annealing
time with chloroform was longer, the average value of the depth distribution of concavities
and convexities and the standard deviation of the depth of concavities and convexities were
increased. As the solvent annealing process with chloroform, a time period of about 3
hours was required until clear concavities and convexities appeared. Note that it was
observed that polyethylene oxide precipitated when the solvent annealing time period
exceeded 240 hours.
[0140]
[Exurrlple 41
In Example 4, observation was made as to how the concave-convex structure of
the thin film changed, by varying the kind of solvent used for the solvent annealing process.
A silane-coupling treated glass base member was coated with a solution of the block
copolymer (block copolymer BCP-I), followed by being dried and subjected to the solvent
annealing process in a similar manner to that in Example 1, but Example 4 was different
from Example 1 in that a mixed solvent of carbon bisulfide and acetone (75:25) was used
as the solvent, rather than using chloroform. An analysis image of the concave-convex
shape of the surface of the thin film after having been subjected to the solvent annealing
process was observed with an atomic force microscope, under a similar analysis condition
to that in Example I. According to the calculation performed for the surface of the thin
film with the E-sweep based on the concavity and convexity analysis image, the average
value of the depth distribution of concavities and convexities was 50.5 nm, and the
standard deviation of the depth of concavities and convexities was 20.0 nm. It was
confirmed that the Fourier-transformed image showed an annular pattern substantially
centered at an origin at which an absolute value of wavenumber was 0 and that the
annular pattern was present within a region where an absolute value of wavenumher was
within a range of not more than 10 prn". The kurtosis of concavities and convexities was
-0.27.
[0141] Next, similarly as described above, a silane-coupling treated glass base member
was coated with a solution of the block copolymer @lock copolymer BCP-I), followed by
being dried and subjected to the solvent annealing process, except that the mixture ratio of
carbon bisulfide and acetone was changed to 50:50 that was used as the solvent instead of
using chloroform. According to the calculation performed for the surface of the thin film
with the E-sweep based on the concavity and convexity analysis image of the surface of the
thin film and the concavity and convexity analysis image of the cross section at a portion in
the vicinity of the surface of the thin film, the average value of the depth distribution of
concavities and convexities was 23.6 nm, and the standard deviation of the depth of
concavities and convexities was 10.3 nm. It is appreciated that as the mixture ratio of
acetone was greater, the height of concavities and convexities became lower. It was
confirmed that the Fourier-transformed image showed an annular pattern substantially
centered at an origin at which an absolute value of wavenumher was 0 pm-l, and that the
annular pattern was present within a region where an absolute value of wavenumber was
within a range of not more than 10 pm-I. The kurtosis of concavities and convexities was
-0.98.
[0142] Next, similarly as described above, a silane-coupling treated glass base member
with a solution of the block copolymer (block copolymer BCP-I), followed by being dried
and subjected to the solvent annealing process, except that dichloromethane was singly
used as the solvent. According to the calculation performed for the surface of the thin
film with the E-sweep based on the concavity and convexity analysis image of the surface
of the thin film and the concavity and convexity analysis image of the cross section at a
portion in the vicinity of the surface of the thin film, the average value of the depth
distribution of concavities and convexities was 45.0 nm, and the standard deviation of the
depth of concavities and convexities was 15.0 nm. It was confirmed that the
63
Fourier-transformed image showed an annular pattern substantially centered at an origin at
which an absolute value of wavenumber was 0 pm-', and that the annular pattern was
present within a region where an absolute value of wavenumber was within a range of not
more than 10 w-'. The kurtosis of concavities and convexities was -0.51.
[0143] Next, similarly as described above, a silane-coupling treated glass base member
was coated with a solution of the block copolymer (block copolymer BCP-I), followed by
being dried and subjected to the solvent annealing process, except that toluene was used as
the solvent. From the concavity and convexity analysis image (not shown) of the surface
of the thin film and the concavity and convexity analysis image (not shown) of the cross
section at a portion in the vicinity of the surface of the thin film, the concavities and
convexities appeared not to be very clear, and the pitch of concavities and convexities also
appeared to be widen. According to the calculation performed for the surface of the thin
film with the E-sweep based on the concavity and convexity analysis images, the average
value of the depth distribution of concavities and convexities was 33.0 nm, and the
standard deviation of the depth of concavities and convexities was 10.3 nm. It was
confirmed that the Fourier-transformed image showed a circular pattern substantially
centered at an origin at which an absolute value of wavenumber was 0 pm-', and that the
circular pattern was present within a region where an absolute value of wavenumber was
within a range of not more than 10 pn-'. The kurtosis of concavities and convexities was
-0.17.
[0144] Next, similarly as described above, a silane-coupling treated glass base member
was coated with a solution of the block copolymer (%lock copolymer BCP-I), followed by
being dried and subjected to the solvent annealing process, except that acetone was singly
used as the solvent. According to the calculation performed for the surface of the thin
film with the E-sweep based on the concavity and convexity analysis image of the surface
of the thin film and the concavity and convexity analysis image of the cross section at a
portion in the vicinity of the surface of the thin film, the average value of the depth
distribution of concavities and convexities was 52.1 nm, and the standard deviation of the
depth of concavities and convexities was 16.3 nm. It was confirmed that the
Fourier-transformed image showed an annular pattern substantially centered at an origin at
which an absolute value of wavenumber was 0 pm-', and that the annular pattern was
present within a region where an absolute value of wavenumber was within a range of not
more than 10 pm-I. The kurtosis of concavities and convexities was -0.6.
64
[0145] From the above results, it is preferable to use the mixed solvent of carbon
bisulfide and acetone, and to use dichloromethane or acetone singly, as the .. - solvent used
for the solvent annealing process of the block copolymer composed of PS and PMMA.
[0146]
[Example 51
In Example 5, observation was made as to how the concave-convex shape after
the solvent annealing process changed, by varying the blending amount of polyethylene
oxide (PEO) added to the block copolymer solution. A silane-coupling treated glass base
member was coated with a solution of the block copolymer (block copolymer BCP-I),
followed by being dried and subjected to the solvent annealing process in a manner similar
to that in Example I, but Example 5 was different from Example 1 in that the parts by mass
of polyethylene oxide (expressed in %) relative to 100 parts by mass of the block
copolymer was changed to be 0%, 5%, 15%, 25%, 30%, 35% and 70%. Analysis images
of the concave-convex shape of the surface of the thin film after having been subjected to
I the solvent annealing process were observed with an atomic force microscope for the
respective blending amounts, under a similar analysis condition to that in Example 1.
Then, based on these analysis images of concavities and convexities, the average values of
the depth distribution of concavities and convexities on the surface of the thin film (and the
standard deviation values of the depth of concavities and convexities as well) were
I
calculated with the E-sweep. The results are shown in TABLE 3 as follows, together with
[0147]
[TABLE 31
[0148] It was confirmed that the Fourier-transformed image showed an annular pattem
substantially centered at an origin at which an absolute value of wavenumber was 0 pm-',
and that the annular pattem was present within a region where an absolute value of
wavenumber was within a range of not more than 10 pm-' with respect to each of the thin
films which were different in the blending amount of PEO. From the results shown in
TABLE 3, the concavity and convexity analysis image of the surface of the thin film and
the concavity and convexity analysis image of the cross section at a portion in the vicinity
of the surface of the thin film, it is appreciated that when polyethylene oxide was not
present in the block copolymer solution, the concavities and convexities hardly appeared in
the thin film subjected to the solvent annealing process; however, as the blending amount
of polyethylene oxide was greater, the height of concavities and convexities of the thin film
became greater. Note that in additional experiments, it was observed that when the
blending amount of polyethylene oxide exceeded 70% relative to the block copolymer,
polyethylene oxide precipitated. From this result, a suitable blending amount of
polyethylene oxide relative to the block copolymer is considered in a range of 5% to 70%.
[0149]
[Example 61
In Example 6, observation was made as to how the concave-convex shape
changed, depending on the presence or absence of heating treatment (heating annealing)
after the solvent annealing process and depending on the heating temperature. As the
block copolymer, the block copolymer I (BCP-I) was used, and a silane-coupling treated
glass base member was coated with a solution of the block copolymer, followed by being
dried and subjected to the solvent annealing process in a manner similar to that in Example
1, but Example 6 was different from Example 1 in that the blending amount of
polyethylene oxide relative to (100 parts by mass of) the block copolymer was changed to
be 30% (30 parts by mass). After the solvent annealingprocess, there were prepared a
sample which was not heated, a sample which was heated for 1 hour at 40 degrees Celsius,
a sample which was heated for 1 hour at 50 degrees Celsius, and a sample which was
heated for 1 hour at 60 degrees Celsius. With respect to each of these samples, analysis
images of the concave-convex shape of the surface of the thin film were observed with an
atomic force microscope, under a similar analysis condition to that in Example 1. TABLE
4 as follows shows the average values of the depth distribution of concavities and
convexities on the surface of the thin film, the standard deviation values of the depth of
concavities and convexities and the kurtosis values of the concavities and convexities
which were calculated with the E-sweep based on the analysis images taken for the
respective samples.
[0150]
[TABLE 41
Heating
temperature
I concavities and 1 71.3 1 55.8 1 40.4 / 27.1 1
Heating Time
period
Average of
convexities (nm) J
No heating
-
/ Kurtosis 1 -0.75 1 -0.88 1 -0.11 1 -0.19 1
40 degrees
Celsius
Standard deviation
(nm)
I hour
50 degrees
Celsius
24.6
60 degrees
Celsius
1 hour 1 hour
20.0 17.1 11.9
[0151] In a case that there was no heating process after the solvent annealing process, the
average value of depth distribution of concavities and convexities was 71.3 nrn, whereas
the heating performed at 40 degrees Celsius for one hour resulted in lowering the average
value of depth distribution of concavities and convexities to 55.8 nm. Raising the heating
temperature up to 50 degrees Celsius resulted in further lowering the average value of
depth distribution of concavities and convexities to 40.4 nm. Moreover, raising the
heating temperature fUrther up to 60 degrees Celsius resulted in lowering the average value
of depth distribution of concavities and convexities further to 27.1 nm. In view of these
results, consequently, the heating process after the solvent annealing process works as
thermal annealing (thermal blunting) to cause the pattern to be blunt, lowering the height of
concavities and convexities. Note that, as appreciated from the result of Example 1, the
method of the present invention realizes the sufficient height of concavities and convexities
as well as the kurtosis of -0.75 only with the solvent annealing process, thus obtaining a
smooth wave-like shape of the concavities and convexities. Accordingly, it is appreciated
that the temperature annealing after the patterning (solvent annealing) is basically
unnecessary, except for any special case wherein the height of concavities and convexities
needs to be adjusted.
[0152]
[Comparative Example 11
Similarly to Example 1, toluene was added to 150 mg of the block copolymer 1
and 37.5 mg of Polyethylene Glycol 2050 manufactured by ALDRICH (average Mn =
2050) as the polyethylene oxide so that the total amount thereof was 15 g, followed by
being dissolved. Then, the solution of the block copolymer was filtered in a similar
manner as in Example 1 so as to obtain a block copolymer solution. A silane-coupling
treated glass (base member), which was prepared in a same manner as in Example 1, was
coated with the obtained block copolymer solution by the spin coat, under a similar
condition as in Example 1.
[0153] Then, the base member was heated for 3 hours in an oven at a temperature of 160
degrees Celsius (annealing process). A thin film on the surface of the base member after
the heating was formed with concavities and convexities, and it was observed that the
block copolymer underwent the micro phase separation.
[0154] The heated thin film was subjected to etching in the following manner: the thin
film was irradiated with ultraviolet light by using a high-pressure mercury lamp at
68
irradiation intensity of 30 ~ l c mt~he,n the thin film was immersed in acetone, followed by
being cleaned with an ion-exchanged water and then dried. By this etching process, the
PMMA on the substrate (base member) was selectively removed, and thus a thin film
having a fine concave-convex pattern formed thereon was obtained.
[0155] Fig. 10A shows a concavity and convexity analysis image of the surface of the
obtained thin film. Fig. 10B shows a concavity and convexity analysis image of the cross
section at a portion in the vicinity of the surface of the thin film. In view of the
cross-sectional structure shown in Fig. 10B, it is considered that PS and PMMA have the
lamella orientation because a vertical cross-sectional structure was present. From the
concavity and convexity analysis images each regarding the surface of the thin film shown
in Figs. IOA and 10B, a Fourier-transformed image, the average pitch of concavities and
convexities, the average value of the depth distribution of concavities and convexities and
the standard deviation of depth of concavities and convexities were obtained in a similar
manner as in Example 1; the average value of the depth distribution of concavities and
convexities was 75.8 nm, the standard deviation of depth of concavities and convexities
was 47.2 nm, and the kurtosis was -1.63. It was confirmed that the Fourier-transformed
image showed a circular pattern substantially centered at an origin, and that the circular
pattern was present within a region where an absolute value of wavenumber was within a
range of not more than 10 pm-'., as shown in Fig. 1 OC. From these results, it is
appreciated that even using the block copolymer having the same composition as that in
Example 1, the micro phase separation structure generated by the self-organization of the
block copolymer is different due to the difference in the annealing method, and that the
horizontal cylinder structure can be generated only by the solvent phase separation (solvent
annealing) according to the present invention. Further, it is appreciated that the solvent
phase separation according to the present invention can realize a concave-convex structure
having a wave-like shape with a smooth surface.
[0156]
[Example 71
In Example 7, a mold was produced in accordance with the method of the present
invention, a diffraction grating was produced by using the mold, and an organic EL
element was produced by using the obtained diffraction grating.
101571
[Production of mold and diffraction grating]
69
As the block copolymer, block copolymer 1 (BCP-1) was used, and a solution of
the block copolymer was prepared and then a silane-coupling treated glass base member
was coated with the prepared solution of the block copolymer, followed by being dried and
subjected to the solvent annealing process in a manner similar to that in Example 1, but
Example 7 was different from Example 1 in that the blending amount of polyethylene
oxide was changed to be 30 parts by mass relative to 100 parts by mass of the block
copolymer.
[0158] By the solvent annealing, concavities and convexities having a wave-like shape
was generated on a surface of the thin film. Next, a thin nickel layer having a thickness
of about 20 nm was formed on the surface of the thin film as the electric current seed layer
by the sputtering. Subsequently, the base member with the thin film was immersed in a
nickel sulfamate bath and was subjected to an electroforming process (maximum current
density: 0.05 .4/cm2) at a temperature of 50 degrees Celsius so as to precipitate nickel until
the thickness of nickel became 250 pm. The base member with the thin film was
mechanically peeled off or released from the nickel electroforming body obtained in such a
manner. Subsequently, polymer component(s) adhered to a part of the surface of the
nickel electroforming body was (were) removed by repeating the following process three
times. Namely, the nickel electroforming body was immersed in a tetrahydrofuran
solvent for 2 hours; then the nickel electroforming body was coated with an acrylic-based
UV curable resin; the acrylic-based UV curable resin, with which the nickel electroforming
body was coated, was cured; and then the cured resin was peeled off. After that, the
nickel electroforming body was immersed in Chemisol2303 manufactured by THE
JAPAN CEE-BEE CHEMICAL CO., LTD., and cleaned while being stirred for 2 hours at
50 degrees Celsius. Thereafter, the UV ozone treatment was performed for the nickel
electroforming body for 10 minutes.
[0159] The shape of the concavities and convexities on the surface of the nickel
electroforming body was analyzed with the atomic force microscope used in Example 1,
and an analysis image was obtained. The analysis image was observed with the atomic
force microscope under an analysis condition similar to that in Example 1. According to
the calculation performed for the surface of the nickel electroforming body with the
E-sweep based on the analysis image, the average height of concavities and convexities
(the average value of the depth distribution of concavities and convexities) was 45.7 nm,
and the standard deviation of the depth of concavities and convexities was 22.4 nm.
70
[0160] Subsequently, a resin substrate provided with a concave-convex pattern was
produced by using the nickel electroforming body as the mold, in the following manner.
Namely, a PET substrate (adhesive PET film COSMOSHINE A-4100 manufactured by
TOYOBO CO., LTD.) was coated with a fluorine-based UV curable resin. Then, the
fluorine-based UV curable resin was cured by irradiation with ultraviolet light at 600
m.I/cm2 while the mold was pressed to the PET substrate. After curing of the resin, the
mold was peeled off from the cured resin. Accordingly, a resin substrate with the
concave-convex pattern to which the surface profile (surface shape) of the mold was
transferred was obtained. The resin substrate with the concave-convex pattern can be
used as it is as a diffraction grating. In Example 7, however, this resin substrate with the
concave-convex pattern was used again as a mold (diffraction grating-mold) to thereby
produce a diffraction grating in the following manner.
[0161] 2.5 g of tetraethoxysilane (TEOS) and 2.1 g of methyltriethoxysilane (MTES)
were added by drops to a mixture solution of 24.3 g of ethanol, 2.16 g of water, and 0.0094
g of concentrated hydrochloric acid, followed by being stirred for 2 hours at a temperature
of 23 degrees Celsius and humidity of 45 % to obtain a sol. The sol was applied on a
soda-lime glass plate of 15 x 15 x 0.1 1 cm by a bar coating. Doctor Blade (manufactured
by YOSHIMITSU SEIKI CO., LTD.) was used as a bar coater in the bar coating. The
doctor blade was designed to form a coating film having a thickness of 5 pm. However,
the doctor blade was adjusted to form the coating film having a thickness of 40 pm by
sticking an imide tape having the thickness of 35 pm to the doctor blade. When 60
seconds elapsed after the application of the sol, the diffraction grating-mold was pressed
against the coating film on the glass plate by a pressing roll using a method described
below.
[0162] At first, the surface, of the diffraction grating-mold, formed with the pattern was
pressed against the coating film on the glass substrate while the pressing roll of which
temperature was 23 degrees Celsius was rotated from one end to the other end of the glass
substrate. Immediately after the completion of pressing, the substrate was moved on a hot
plate and then heated at a temperature of 100 degrees Celsius @re-baking). After the
heating continued for 5 minutes, the substrate was removed from the hot plate and the
diffraction grating-mold was manually peeled off from the substrate from the edge such
that an angle (peel angle) of the diffraction grating-mold with respect to the substrate was
about 30 degrees. Subsequently, main baking was performed by heatmg the substrate for
7 1
60 minutes in an oven at 300 degrees Celsius. Thus, a diffraction grating formed with the
concave-convex pattern made of the sol-gel material was obtained.
(01631
[Production of organic EL element]
For the glass substrate formed with the pattern made of the sol-gel matenal thus
obtained as the diffraction grating, cleaning was performed with a brush so as to remove
any foreign matter, etc., adhered to the glass substrate. After the cleaning, any organic
matter, etc., was removed with an alkaline cleaning agent and an organic solvent. On the
substrate cleaned in such a manner, IT0 was deposited to form an IT0 film having a
thickness of 120 nm by the sputtering method at 300 degrees Celsius. Then the IT0 film
was coated with photoresist, and the photoresist was exposed with an electrode mask
pattern (mask pattern for electrode), and the etching was performed with an developing
solution, thereby obtaining a transparent electrode having a predetermined pattern. The
obtained transparent electrode was cleaned with a brush, any organic matter, etc. was
removed with an alkaline cleaning agent and an organic solvent, and then the UV ozone
treatment was performed for the transparent electrode. On the transparent electrode
treated in such a manner, a hole transporting layer (4,4',4"-tris(9-carbazole)
triphenylamine; thickness: 35 nm), a light emitting layer (4,4',4"-tris(9-carbazole)
triphenylamine doped with tris(2-phenyl pyidinato) indium (111) complex; thickness: 15
nm, l,3,5-tris(N-phenylbenzimidazol-2-y1)benzene doped with tris(2-phenyl pyridinato)
iridium (111) complex; thickness: 15 nm), an electron transporting layer
(1,3,5-tris(N-phenylbenzimidazol-2-y1)benzene; thickness: 65 nm), and a lithium fluoride
layer (thickness: 1.5 nm) were stacked by means of the vapor deposition method, and
further a metal electrode (aluminum; thickness: 50 nm) was formed thereon by means of
the vapor deposition method. Thus, an organic EL element 200 having a coating film
(sol-gel material layer) 142, a transparent electrode 93, an organic layer 94 (hole
transporting layer 95, light emittinglayer 96, and electron transporting layer 97), and a
metal electrode 98 provided in this order on a substrate 140 as shown in Fig. 7 was
obtained.
[0164]
[Evaluation of light emission efficiency of organic EL element]
The light emission efficiency of the organic EL element obtained in Example 7
was measured in the following method. Namely, voltage V was applied to the obtained
72
organic EL element, and the applied voltage V and electric current I flowing through the
organic EL element were measured with a voltage application current measurement
apparatus (manufactured by ADC CORPORATION, model name: R6244) and a total light
flux amount L was measured with a total light flux measuring apparatus manufactured by
SPECTRA CO-OP. A luminance value L' was calculated from the measured values of the
applied voltage V, the electric current I and the total light flux amount L thus obtained, and
the electric current efficiency and the electric power efficiency of the organic EL element
were calculated by using the following formulae (Fl) and (F2), respectively:
Electric current efficiency = (L'II) x S ... (Fl);
Electric power efficiency = (L'IIN) x S ... (F2),
wherein in the above formulae (Fl) and (F2), "S" represents a light-emitting area of the
organic EL element. Note that, on the assumption that the light distribution
characteristics of the organic EL element obeyed the Lambert-Beer law, the total light flux
amount L was converted into the luminance value L' in accordance with the following
formula (F3):
L' = LIdS ... (F3).
[0165] Fig. 11 shows the change in electric current efficiency of the organic EL element
with respect to the luminance of the organic EL element. Fig. 12 shows the change in
electric power efficiency of the organic EL element with respect to the luminance of the
organic EL element. Note that for purpose of comparison, an organic EL element was
produced by using a glass substrate not having any concavity and convexity (flat substrate)
by a method similar to the method described above, and the electric current efficiency and
electric power efficiency of this organic EL element with respect to the luminance of the
organic EL element were also indicated in Fig. 11 and Fig. 12, respectively. The organic
EL element of Example 7 exhibited the electric current efficiency at the luminance of 1000
cd/m2 that was approximately 1.5 times the electric current efficiency of the organic EL
element having no concavity and convexity on the glass substrate. Further, the organic
EL element of Example 7 exhibited the electric power efficiency at the luminance of 1000
cd/m2 that was approximately 1.7 times the electric power efficiency of the organic EL
element having no concavity and convexity on the glass substrate. Thus, the organic EL
element of the present invention had sufficient light extraction efficiency.
[0165]
[Evaluation of light emission directionality of organic EL element]
73
The light emission directionality of the organic EL element obtained in Example 7
was evaluated with the following method. Namely, the organic EL element made to emit
light was visually observed from all the direction (all-surrounding direction of 360
degrees). There were no particularly bright or dark spots even observing in any direction
of all-surrounding 360 degrees, and the organic EL element exhibited uniform brightness
in all the direction. Accordingly, the organic EL element of the present invention was
confirmed to have a sufficiently low light emission directionality.
[0167] As described above, it is appreciated that an organic El element, which is obtained
by using a mold and a diffraction grating obtained by using the substrate having the
concave-convex pattern formed thereon, which is obtained by the solvent annealing
process, have a sufficient light extraction efficiency. Further, since the concave-convex
pattem of the diffraction grating produced in Example 7 is formed of the sol-gel material
and thus has excellent mechanical strength, chemical resistance and weather resistance, the
concave-convex pattem of the diffraction grating is capable of sufficiently withstanding the
atmosphere, chemical agent, etc. in each of the steps in the production process for
producing the transparent electrode of the organic EL element. For a reason similar to
above, an organic EL element as a device produced by the method of the present invention
has excellent weather resistance, heat resistance and corrosion resistance, and thus have a
long service life.
101681 Although the present invention has been explained as above with the examples,
the mold-producing method, diffraction grating-producing method and organic EL
element-producing method of the present invention are not limited to the above-described
examples, and may be appropriately modified or changed appropriately within the range of
the technical ideas described in the following claims.
[0169] Further, although the "substrate having a concave-convex pattern" has been
explained with an example of a diffraction grating substrate (optical substrate), the
"substrate having a concave-convex pattern" is not limited to this; the present invention is
applicable to substrates having a variety of applications or usages. The present invention
is applicable, for example, to substrates for producing: optical elements such as micro lens
arrays, nano prism arrays and optical waveguides; optical parts or components such as
lenses; solar cells; anti-reflection films; semiconductor chips; patterned media; data
storage; electronic paper; LSI; etc., and to substrates used in applications in the field of the
paper production, food production, biotechnology such as immunity analysis chips, cell
74
culture sheets, etc.
INDUSTRIAL APPLICABILITY
(01701 According to the present invention, the concave-convex pattern can be formed via
the self-organization of the block copolymer by the solvent annealing process, and there is
no need to perform the etching. Therefore, the present invention is capable of producing
a substrate having the concave-convex pattern exemplified by the diffraction grating, and
useful devices such as an organic EL element using such a substrate, etc., with a simple
process and high throughput. Thus, the method of the present invention has excellent
mass productivity, thereby greatly contributing to the development of the optical device
industry in our country.
We claim:
1. A method for producing a mold for transferring a fine pattern,
comprising:
a step of coating a surface of a base member with a solution containing a block
copolymer and polyalkylene oxide, the block copolymer being composed of at least first
and second polymer segments;
a solvent phase-separation step of phase-separating the block copolymer contained
in the solution, with which the surface of the base member is coated, under a presence of
vapor of an organic solvent so as to obtain a block copolymer film of the block copolymer,
the block copolymer film having a concave-convex structure on a surface thereof and a
horizontal cylinder structure in an interior thereof;
a step of forming a seed layer on the concave-convex structure of the block
copolymer film;
a step of stacking a metal layer on the seed layer by electroforming; and
a step of releasing the base member, on which the concave-convex structure is
formed, from the metal layer.
2. The method for producing the mold according to claim 1, wherein a
volume ratio between the first and second polymer segments in the block copolymer is in a
range of 4:6 to 6:4.
3. The method for producing the mold according to claim 1, wherein a
content amount of the polyalkylene oxide is in a range of 5 parts by mass to 70 parts by
mass relative to 100 parts by mass of the block copolymer.
4. The method for producing the mold according to any one of claims 1 to 3,
wherein number average molecular weight of the block copolymer is not less than 500,000.
5. The method for producing the mold according to any one of claims 1 to 4, '
wherein no etching process is performed after the solvent phase-separation step.
6. The method for producing the mold according to any one of claims 1 to 5,
76
wherein the first polymer segment composing the block copolymer is polystyrene, and the
second polymer segment composing the block copolymer is polymethyl methacrylate.
7. The method for producing the mold according to any one of claims 1 to 6,
wherein the organic solvent is one selected from the group consisting of chloroform,
acetone, dichloromethane, and a mixed solvent of carbon bisulfide and acetone.
8. The method for producing the mold according to any one of claims 1 to 7,
wherein a time for phase-separating the block copolymer under the presence of the vapor
of the organic solvent is in a range of 6 hours to 168 hours.
9. The method for producing the mold according to any one of claims 1 to 8,
wherein the first or second polymer segment is formed to have a one-tiered structure or a
two-tiered structure in the horizontal cylinder structure.
10. The method for producing the mold according to any one of claims 1 to 9,
wherein an average value of depth distribution of concavities and convexities of the
concave-convex structure is in a range of 30 nm to 150 nm, and standard deviation of depth
of the concavities and convexities is in a range of 10 nm to 50 nm.
11. The method for producing the mold according to any one of claims 1 to
10, wherein a primer layer is formed on the surface of the base member before coating the
surface of the base member with the solution containing the block copolymer, which is
composed of at least the first and second polymer segments, and the polyalkylene oxide.
12. The method for producing the mold according to any one of claims 1 to
1 1, wherein molecular weight distribution (MwIMn) of the block copolymer is not more
than 1.5.
13. The method for producing the mold according to any one of claims 1 to
12, wherein difference in solubility parameter between the first and second polymer
segments is in a range of 0.1 (callcm3 ) 112 to 10 (~allcm~)"~.
14. A method for producing a diffraction grating, the method comprising:
pressing a mold obtained by the method for producing the mold as defined in
claim 1 onto a substrate coated with a concavity-convexity forming material and curing the
concavity-convexity forming material, and removing the mold from the substrate so as to
form a diffraction grating having a concave-convex structure on the substrate.
15. A method for producing a diffraction grating, the method comprising:
pressing a mold obtained by the method for producing the mold as defined in
claim 1 onto a substrate coated with a concavity-convexity forming material, curing the
concavity-convexity forming material, and removing the mold from the substrate so as to
form a structure having a concave-convex structure on the substrate; and
pressing the shucture onto another substrate coated with a sol-gel material, curing
the sol-gel material, and removing the structure from the another substrate so as to form a
diffraction grating having a concave-convex structure formed of the sol-gel material.
16. A method for producing an organic EL element, the method comprising
stacking a transparent electrode, an organic layer and a metal electrode successively on a
concave-convex structure of a diffraction grating, produced by the method of producing the
diffraction grating as defined in claim 14 or 15, so as to form the organic EL element.
17. A mold for transferring a fine pattern produced by the method for
producing the mold as defined in claim 1.
18. A diffraction grating which is produced by the method for producing the
diffraction grating as defined in claim 14 or 15 and which has a concave-convex structure
on a surface thereof.
19. The diffraction grating according to claim 18, wherein an average pitch
of concavities and convexities of the concave-convex structure is in a range of 100 nm to
1,500 nm.
20. The diffraction grating according to claim 18 or 19, wherein a
cross-sectional shape of the concave-convex structure is wave-like; and
78
in a case of obtaining a Fourier-transformed image by performing a
two-dimensional fast Fourier-transform processing on a concavity and convexity analysis
image obtained by analyzing a planer shape of the concave-convex structure with an
atomic force microscope, the Fourier-transformed image shows an annular pattem
substantially centered at an origin at which an absolute value of wavenumber is 0 pm-', and
the annular pattem is present within a region where the absolute value of wavenumber is
within a range of not more than 10 pm-'.
21. The diffraction grating according to any one of claims 18 to 20, wherein
kurtosis of a cross-sectional shape of the concave-convex structure is not less than -1.2.
22. The diffraction grating according to claim 21, wherein the kurtosis of the
cross-sectional shape of the concave-convex structure is in a range of -1.2 to 1.2.
23. An organic EL element produced by the method as defined in claim 16.
24. A method for producing a substrate having a concave-convex structure,
the method comprising:
pressing a mold obtained by the method for producing the mold as defined in
claim 1 onto a substrate coated with a concavity-convexity forming material, curing the
concavity-convexity forming material, and removing the mold from the substrate so as to
form the substrate having a concave-convex structure.
25. A method for producing a substrate having a concave-convex structure,
the method comprising:
pressing a mold obtained by the method for producing the mold as defined in
claim 1 onto a substrate coated with a concavity-convexity forming material, curing the
concavity-convexity forming material, and removing the mold from the substrate so as to
form a structure having a concave-convex structure on the substrate;
pressing the structure onto another substrate coated with a sol-gel material, curing
the sol-gel material, and removing the structure from the another substrate so as to form the
substrate having a concave-convex structure formed of the sol-gel material.
26. A substrate having a concave-convex structure on a surface thereof and
produced by the method as defined in claim 24 or 25.
27. The substrate having the concave-convex structure according to claim 26,
wherein an average pitch of concavities and convexities of the concave-convex structure is
in a range of 100 nm to 1,500 nm.