DESCRIPTION
Title of Invention
METHOD FOR PRODUCING CONCAVE-CONVEX SUBSTRATE USING SOL-GEL
METHOD, SOL SOLUTION USED IN SAME, METHOD FOR PRODUCING
ORGANIC EL ELEMENT USING SAME, AND ORGANIC EL ELEMENT OBTATNED
THEREBY
Technical Field
[0001] The present invention relates to a method for producing a substrate having a
minute or fine pattern by use of a transfer roll, a method for producing an organic EL
element (Organic Electro-Luminescence element or organic light emitting diode) using the
same, and the organic EL element obtained thereby. More specifically, the present
invention relates to a method for producing a substrate having a minute or fine pattern by
use of a transfer roll by a sol-gel method, a sol used for the producing method, a method
for producing an organic EL element using the producing method, and the organic EL
element obtained thereby.
Background Art
[0002] There has been known a lithography method as a method for forming a minute
pattern such as a semiconductor integrated circuit. The resolution of the pattern formed
by the lithography method is dependent on the wavelength of a light source and the
numerical aperture of an optical system, and the light source is expected to have shorter
wavelength in order to meet demand for miniaturized devices in recent years. However,
the light source having the short wavelength is expensive, development thereof is not easy,
and the developinent of an optical material transmitting such a short-wavelength light is
also needed. Further, manufacturing a large-area pattern by a conventional lithography
method needs a large-size optical element, and thus there are difficulties in technical and
economic aspects. Therefore, a novel method for forming a desired pattern on a large
area has been studied.
[0003] 'There has been known a nanoimprint method as a method for forming a minute
pattern without using any conventional lithography apparatus. The nanoimprint method
i4 a technique such that a pattern of an order of nanometer can be transferred by
2
sandwiching a resin between a mold and a substrate. A thermal nanoimprint method, a
photonanoimprint method, and the like have been studied depending on an employed
material. Of the above methods, the photonanoimprint method includes four steps of: i)
application of a resin layer; ii) pressing by use of the mold; iii) photo-curing; and iv)
mold-releasing. The photonanoimprint method is excellent in that processing on a
nanoscale can be achieved by the simple process as described above. Especially, since a
photo-curable resin curable by being irradiated with light is used as the resin layer, a period
of time for a pattern transfer step is short and a high throughput is promised. Thus, the
photonanoimprint method is expected to come into practical use in many fields including,
for example, an optical member such as the organic EL element and LED, MEMS, a
biochip and the like. in addition to a semiconductor device.
[0004] However, the photo-curable resin described above generally has a low heat
resistance, and decomposed andlor turns into yellow at a high temperature. Thus, there is
fear that a film having the minute pattern is decomposed in a case that a high temperature
treatment is included in subsequent steps. Further, the photo-curable resin has a low
adhesion property to a glass substrate. Furthermore, in a case that the resin layer to which
the pattern has been transferred is used for an element such as the organic EL element,
there is fear that impurities are eluted from the resin layer and cause adverse effect on the
element.
[0005] As the thermal nanoimprint method, for example, there has been known the
method as described in Patent Literature 1. That is, it is prepared a mold having a planar
transfer surface on which a concavity and convexity pattern is formed; a thermoplastic
base member (processed object) is heated and softened; the transfer surface is pressured
and pressed against the base member; the mold and the base member are cooled as they
are; the mold is peeled off from the base member; and thereby an inverted pattern is
transferred. The thermal nanoimprint method has advantages such that the nano-level
transfer can be achieved by the simple method as described above, and that there is a wide
range of choice of the transfer-target base member.
[0006] However, the thermal nanoimprint method generally needs a high pressure for
pressing, and takes time for a heating-cooling cycle. Thus, the thermal nanoimprint
method is unsuitable for a case in which high productivity is desired. Further, the thermal
nanoi~nprintm ethod has the problem of the heat resistance since the thermoplastic resin is
heated and softened to perform the transfer. For example, in a case that the transfer-target
3
object is exposed to a temperature higher than a molding temperature, there is a fear that
the pattern is deformed and thereby it can not be used.
[0007] A method for improving the heat resistance is exemplified by a nanoimprint
method using a thermosetting material. For example, there has been known the method
as described in Patent Literature 2. That is, a resist film is applied on a substrate, the
substrate is pressed with a mold having a flat plate shape, and then the resist film is cured
using a heater. Especially, a nanoimprint molded product using an inorganic sol-gel
material has a high heat resistance, and any problem is unlikely to occur even when a high
temperature treatment is performed. However, the pressing method using the sol-gel
material also has the following problem. Each thermal expansion coefficient of the
flat-plate-shaped mold, the base member, and a stage is different from one another, thus the
difference in the linear coefficients of expansion causes deviation in a transferred surface
profile of the molded product. In order to suppress the deviation, a means for absorbing
the thermal expansion and/or a long period of heating-cooling process islare required.
Further, since a solvent positioned in the center of the mold having the flat plate shape used
for the pressing is less likely to evaporate, transfer failure occurs in the center of the mold
andlor unevenness of the transfer occurs owing to the difference in a cured state of the
surface. Furthermore, in a case that gas is generated due to bumping of the solvent,
bubbles are formed in the pattern and/or a trace or mark of gas (a trace of escape of gas) is
left in some cases. The above problems become especially conspicuous when the transfer
pattern is formed in a large area. The solvent evaporates from an end portion of the
coating film, and a heating process is required for a long time at a low temperature (for
example, 120 degrees Celsius) in order to evaporate the solvent completely, which
decreases the productivity. Further, since the surface of the mold having the flat plate
shape needs to be pressed uniformly at the same time, a relatively great transfer pressure is
required. Thus, when the transfer pattern has the large area, it is difficult to press the
surface of the mold uniformly under the great pressure. Moreover, when the mold is
peeled off from the base member, a great peeling force is required to pull up the mold in a
vertical direction. Therefore, there is fear that a sol-gel material layer is broken at the
time of the peeling of the mold from the sol-gel material layer, and thereby the pattern is
collapsed. As described above, there are many problems to perform the press transfer to a
large area by use of the mold having the flat plate shape.
[OOOS] Instead of the pressing method using the flat-plat- shaped mold, there has been
4
known the roll press method, as described in Patent Literature 3, in which a pressing roll
and a cylindrical master plate for duplication having a minute concavity and convexity
pattern are used. An area of contact between a mold and a coating film is small in a roll
process as compared with the case in which the flat-plate-shaped mold is used, and thus it
is considered that some of the above problems can be solved. However, the roll press
method using the sol-gel material also has the following problem. In processing using the
sol-gel material, the processing is started from a raw material solution; after production of
sol, gel is produced by chemical reaction such as hydrolysis and condensation
polymerization; the solvent remained inside is removed by a heating process; and the glass
and ceramics is obtained by further promoting densification. However, since the
time-dependent change of evaporation of the solvent in a gelled state is rapid, if the control
is not performed precisely after the sol is applied on the substrate and before the concavity
and convexity pattern is pressed by the roll press, the failure arises such that depths of
concavities and convexities are insufficient and that the transfer pattern can not be
obtained.
Citation List
Patent Literature
[0009] PATENT LITERATURE 1: Japanese Patent Application Laid-open No.
200 1-26052
PATENT LITERATURE 2: Japanese Patent Application Laid-open No.
2008-049544
PATENT LITERATURE 3: Japanese Patent Application Laid-open No.
201 0-269480
Summary of Invention
Technical Problem
[0010] In view of the above, an object of the present invention is to provide a method for
reliably producing a substrate having a minute or fine concavity and convexity pattern by
use of a sol-gel material by a roll press method with high efficiency. Another object of
the present invention is to provide an organic EL element having excellent durability and
satisfactory light resistance. Still another object of the present invention is to provide a
sol suitable for the method for producing the substrate of the present invention.
5
Solution to the Problem
[0011] According to the first aspect of the present invention, there is provided a method
for producing a substrate having a concavity and convexity pattern, including:
a step of applying a sol, which contains a silica precursor, on a substrate to form a
coating film;
a step of drying the coating film;
a step of pressing a mold having a concavity and convexity pattern against the
dried coating film with a pressing roll so that the concavity and convexity pattern is
pressed onto the coating film;
a step of peeling off the mold from the coating film; and
a step of baking the coating film to which the concavity and convexity pattern has
been transferred,
wherein the coating film is dried in the drying step so that a ratio of weight of the
coating film to dried weight of the coating film is in a range of 1.4 to 8.8, the dried weight
being obtained by baking the coating film at a temperature of 100 degrees Celsius.
[0012] In the step of pressing the concavity and convexity pattern against the coating film
in the method of the present invention, the mold having the concavity and convexity
pattern may be pressed against the dried coating film with the pressing roll while the dried
coating film is heated. In a case that the dried coating film is heated, the coating film may
be dried in the drying step so that the ratio of the weight of the coating film to the dried
weight of the coating film is in a range of 1.4 to 4.5, the dried weight being obtained by
baking the coating film at a temperature of 100 degrees Celsius. In the case that the dried
coating film is heated, the pressing roll may include a heater. In this case, the pressing
roll may be heated to temperatures of 40 degrees Celsius to 150 degrees Celsius by the
heater.
[0013] In the method of the present invention, the sol preferably contains one kind of
inetal alkoxide or a several kinds of metal alkoxides. Further, the sol preferably contains
a mixture of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES).
[0014] 'The method of the present invention preferably includes a pre-baking step, in
which the coating film to which the concavity and convexity pattern has been pressed is
subjected to pre-baking before the mold is peeled off, so that the mold is easily peeled off
from the coating film on the side of the substrate.
6
[0015] In the peeling step, a peeling roll is preferably used to peel off the mold from the
coating film easily. Especially, the peeling roll is heated to peel off the mold from the
coating film more easily.
[0016] The average pitch of concavities and convexities on the concavity and convexity
pattern may be in a range of 100 nm to 900 nm and especially in a range of 100 nm to 600
nm. The average height of the concavities and convexities may be in a range of 20 nm to
200 nm. The mold having the concavity and convexity pattern may be a flexible mold.
In a case that the flexible mold is used, the flexible mold may be a long mold having a
length longer than that of the substrate from a viewpoint of improving the productivity.
The long mold can be pressed against the coating film with the pressing roll while being
transported by use of a feeding roll which feeds the long mold and a winding roll which
winds or rolls up the long mold thereon.
[0017] According to the second aspect of the present invention, there is provided a
method for producing an organic EL element, wherein a diffraction-grating substrate
having a concavity and convexity surface is manufactured by the method for producing the
substrate having the concavity and convexity pattern as defined in the first aspect; and a
transparent electrode, an organic layer, and a metal electrode are stacked in this order on
the concavity and convexity surface of the diffraction-grating substrate, thereby producing
the organic EI, element.
[0018] According to the third aspect of the present invention, there is provided an organic
EL element which is obtained by the method as defined in the second aspect to include a
transparent electrode, an organic layer, and a metal electrode on a diffraction-grating
substrate having a concavity and convexity surface, wherein the diffraction-grating
substrate is formed of a substrate having no concavity and convexity pattern and a silica
layer having a concavity and convexity pattern formed directly on the substrate having no
concavity and convexity pattern. In this case, the substrate may be a substrate made of an
inorganic material.
[0019] According to the fourth aspect of the present invention, there is provided a sol
(sol-gel solution) used for the method for producing the substrate having the concavity and
convexity pattern as defined in the first aspect.
Advantageous Effects of Invention
[0020] According to the present invention, by drying the coating film so that the ratio of
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weight of the coating film to the dried weight of the coating film is in a range of 1.4 to 8.8,
the dried weight being obtained by baking the coating film having a relatively large area at
a temperature of 100 degrees Celsius, it is possible to reliably transfer the concavity and
convexity pattern from the mold to the coating film by use of the pressing roll in a short
time after the drying step. Therefore, it is possible to produce a substrate, which has a
relatively large area, with a coating film, which has a minute concavity and convexity
pattern, at a high yield. Further, the yield can be further improved by performing the
pressing step while heating the coating film. Since the concavity and convexity pattern of
the substrate is made of silica by the sol-gel process, the substrate obtained by the method
of the present invention is a substrate which may be resistant to a high temperature process
performed when the organic EL element is produced. The organic EL element produced
by the present invention has excellent durability and satisfactory light resistance.
Brief Description of Drawings
[OOZ l]
Fig. 1 is a flowchart showing a method for producing a substrate having a
concavity and convexity pattern of the present invention.
Fig. 2 is a graph showing a relationship between the time elapsed after a sol is
applied on a glass substrate by use of a bar coater and the ratio of weight of a coating film
to dried weight of the coating film.
Fig. 3 is a conceptual view illustrating an apparatus for producing a flexible mold
by a roll process.
Fig. 4 is a flowchart showing a method for producing a substrate having a
concavity and convexity pattern by hot press.
Fig. 5 is a conceptual view illustrating an apparatus used for performing the
method of the present invention.
Fig. 6 is a conceptual view illustrating another apparatus used for performing the
method of the present invention.
Fig. 7 is a conceptual view illustrating an apparatus used for performing the
method using the hot press.
Fig. 8 is a conceptual view illustrating another apparatus used for performing the
method using the hot press.
Fig. 9 is a conceptual view illustrating still another apparatus used for performing
8
the method using the hot press.
Fig. 10 is a conceptual view illustrating yet another apparatus used for performing
the method using the hot press.
Fig. 11 is a conceptual view illustrating further apparatus used for performing the
method using the hot press.
Fig. 12 is a conceptual view illustrating still further apparatus used for performing
the method using the hot press.
Fig. 13 shows a cross-section structure of an organic EL element.
Figs. 14(a) to 14(c) schematically show a structure of a mold used in Examples,
wherein Fig. 14(a) is a plan view of the mold, Fig. 14(b) shows a planer structure of one
pattern partitioned or divided into three, and Fig. 14(c) is a cross-sectional view of a
partitioned 400 nm pitch pattern.
Fig. 15 is a graph showing a relationship between the time elapsed after a sol is
applied on a glass substrate by use of a spin coater and the ratio of weight of a coating film
to dried weight of the coating film in Example 2.
Fig. 16 is a graph showing a relationship between the time elapsed after a sol is
applied on a glass substrate by use of a spin coater and the ratio of weight of a coating film
to dried weight of the coating film in Example 5.
Description of Embodiments
[0022] Hereinbelow. an embodiment of a method for forming a substrate having a
concavity and convexity pattern of the present invention will be described with reference
to the drawings.
I00231 As shown in Fig. 1, the method for forming the substrate having the concavity and
convexity pattern of the present invention mainly includes: a solution preparation step S1
for preparing a sol (also referred to as a sol-gel solution); an application step S2 for
applying the prepared sol on a substrate; a drying step S3 for drying the coating film of the
sol applied on the substrate; a pressing step S4 for pressing a mold having a transfer
pattern; a pre-baking step S5 during which the coating film to which the mold has been
pressed is subjected to pre-baking; a peeling step S6 for peeling off the mold from the
coating film; and a main baking step S7 during which the coating film is subjected to main
baking. Hereinbelow, an explanation will be made about each of the steps sequentially.
100241
[Sol preparation step]
In the present invention, at first, a sol is prepared to form a coating film to which a
pattern is transferred by a sol-gel method. For example, in a case that silica is synthesized
on a substrate by the sol-gel method, 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 functional group andlor polymer
islare introduced into a part of the above material. Further, the silica precursor is
exemplified, for example, by metal acetylacetonate, metal carboxylate, oxychloride,
chloride, and mixtures thereof. The silica precursor, however, is not limited thereto.
Examples of metal species include, in addition to Si, Ti, Sn, Al, Zn, Zr, In, and mixtures
thereof, but are not limited thereto. It is also possible to use any appropriate mixture of
precursors of the oxides of the above metals.
[0025] 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. The sol produces amorphous silica by performing
hydrolysis and polycondensation reaction. An acid such as hydrochloric acid or an alkali
such as ammonia is added in order to adjust 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. The amount of water to be added can be 1.5 times or more with respect to
metal alkoxide species in the molar ratio.
[0026] Examples of the solvent 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
10
ethyl ketone, isophorone, and cyclohexanone; ether alcohols such as butoxyethyl 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; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and
N-methylpyrrolidone; halogen-containing 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.
[0027] As an additive, it is possible to use any additive such as polyethylene glycol,
polyethylene oxide, hydroxypropylcellulose, and polyvinyl alcohol for viscosity
adjustment; alkanolamine such as triethanolamine as a solution stabilizer; P-diketone such
as acetylacetone; P-ketoester; formamid; dimetylformamide; and dioxane.
[0028] Further, any of the following surfactants may be contained as the additive. The
surfactants include, for example, a hydrocarbon surfactant, a fluorine surfactant, and a
silicone surfactant. The hydrocarbon surfactant is exemplified, for example, by
alkylbenzene sulfonates, higher alcohol sulfuric acid ester salts, polyoxyethylene alkyl
ether sulfates, a-sulfo aliphatic acid esters. a-olefin sulfonates, monoalkyl phosphoric acid
ester salts, alkane sulfonates, alkyl trimethylammonium salts, dialkyl dimethylammonium
salts, alkyl dimethyl benzylammonium salts, amine salts, alkylamino fatty acid salts,
alkylamineoxides, polyoxyethylene alkylethers, polyoxyethylene alkylphenol ethers, alkyl
glucosides, and polyoxyethylene aliphatic acid esters.
[0029]
l'he sol prepared as described above is applied on the substrate. As the substrate,
substrates made of inorganic materials such as glass, silica glass, and silicon substrates or
substrates of resins such as polyethylene terephthalate (PET), polyethylene naphthalate
(PE.N), polycarbonate (PC), cycloolefin polymer (COP), polymethyl methacrylate
(PMMA), polystyrene (PS), polyimide (PI), and polyarylate may be used. The substrate
ma] be transparent or opaque. In a case that a substrate having a concavity and convexity
pattern, which is obtained by using this substrate, is used for production of the organic EL
11
element as will be described later, the substrate desirably has the resistance to heat,
ultraviolet (UV) light, etc. In view of this, the substrates made of the inorganic materials
such as the glass, the silica glass, and the silicon substrates are more preferable. A
surface treatment may be performed or an easy-adhesion layer may be provided on the
substrate to improve the adhesion property. And a gas barrier layer may be provided in
order to keep out moisture and/or gas such as oxygen. As a method for applying the sol,
it is possible to use any application method (coating method) such as a bar coating method,
a spin coating method, a spray coating method, a dip coating method, a die coating method,
and an ink-jet method. Among the methods as described above, the bar coating method,
the die coating method, and the spin coating method are preferable, because the sol can be
uniformly applied on the substrate having a relatively large area and the application can be
quickly completed prior to gelation of the sol. It is noted that, since a desired concavity
and convexity pattern of a sol-gel material layer is formed in subsequent steps, a surface of
the substrate (including the surface treatment or the easy-adhesion layer in case that the
surface treatment or the easy-adhesion layer is present) may be flat, and the substrate itself
does not have the desired concavity and convexity pattern.
[0030]
[Drying step]
After the application step, the substrate is held or kept in the atmosphere or under
reduced pressure to evaporate the solvent in the applied coating film (hereinafter also
referred to as "sol-gel material layer" as appropriate). In a case that the holding time of
the substrate is short, the viscosity of the coating film is too low to perform the transfer in
the subsequent transfer step. In a case that the holding time of the substrate is too long,
the polymerization reaction of the precursor proceeds too much and thereby the transfer
cannot be performed in the transfer step. A holding temperature desirably stays constant
in a range of 10 to 100 degrees Celsius, and more desirably stays constant in a range of 10
to 30 degrees Celsius. In a case that the holding temperature is higher than this range, the
gelation reaction of the coating film proceeds rapidly before the pressing step, which is not
preferable. In a case that the holding temperature is lower than this range, the gelation
reaction of the coating film proceeds slowly before the pressing step, which reduces the
productivity and is not preferable. Accordingly, since the drying state changes depending
on the holding temperature and the holding time, holding conditions in the drying step are
required to be controlled accurately. After the application of the sol, the polymerization
12
reaction of the precursor proceeds as the evaporation of the solvent evaporates, and the
physical property such as the viscosity of the sol also changes in a short time. The
amount of vaporization of the solvent depends also on the amount of the solvent
(concentration of the sol) used at the time of preparing the sol. Therefore, a criterion for
evaluating a state suitable for the transfer is desired.
[0031] Inventors of the present invention controlled the drying step to optimize the
pressing by use of the mold in the subsequent transfer step from the following viewpoints.
In a case of the hydrolysis/condensation polymerization reaction of the silica precursor,
dealcoholization reaction generally occurs to generate alcohol in the sol. A volatile
solvent such as the alcohol is used in the sol as the solvent. That is, the alcohol generated
in the hydrolysis process and the alcohol existing as the solvent are included in the sol, and
sol-gel reaction proceeds by removing them in the drying process. The investigation of
an elapsed time and an evaporation amount at the time of evaporating the solvent from the
coating film after applying the the sol on the glass substrate by use of the bar coater
showed that the result shown in Fig. 2. That is, the evaporation of the solvent starts
rapidly immediately after the application, the evaporation amount decreases exponentially,
and the evaporation amount hardly changes after a predetermined time. It is considered
that there is little alcohol solvent remained in the coating film when the change in weight
of the coating film ends. Therefore, a residual alcohol amount in the coating film can be
calculated by measuring the weight of the coating film in this situation. As a result, the
progress of the sol-gel reaction can be quantified. By finding a weight change b(t)/a
which enables the transfer, assuming that the weight of the coating film obtained when the
change in weight of the coating film ends is "a" and the weight of the coating film obtained
when "t" hour(s) has(have) elapsed after the application is "b(t)", the weight change b(t)/a
can be used as the criterion in the drying step. According to Examples which will be
described later, in a case that a mixture of TEOS and MTES is used as the precursor, b(t)/a
is preferably in a range of 1.4 5 b(t)/a 5 8.8 to transfer the pattern. In a case that b(t)/a is
less than 1.4, the coating film is so hard that the pattern can not be transferred. In a case
that b(t)/a exceeds 8.8, the evaporation of the solvent is insufficient and the coating film is
so soft that there is fear that the coating film is damaged at the time of peeling off the mold
or the pattern can not be transferred at all in a case that a period of time during which the
mold makes contact with the coating film is short as in the case of the subsequent transfer
step. Especially, in a case that the coating film is pressed while being heated in the
13
pressing step as will be described later, the coating film is cured in a short time including
the drying step and a period of time during which the coating film passes through the
pressing roll. Therefore, the solvent is required to evaporate sufficiently in the drying
step, and thus b(t)/a is more preferably 1.4 5 b(t)/a 5 4.5. In a case that the coating film is
too soft owing to the inadequate evaporation of the solvent included in the coating film,
and further that b(t)/a exceeds 4.0, the following situation may be caused. That is, since
the fluidity of the coating film is high, the liquid is more likely to flow outside of a transfer
section with pressure at the time of the pattern transfer, which may contaminate a
manufacturing line. Therefore, b(t)/a is further more preferably 1.4 5 b(t)/a 5 4.0.
[0032] The weight change b(t)/a of the coating film is recorded in advance by finding the
weight change of the sol at each elapsed time after the application in a preliminary
experiment. Then, a value included in the above range is selected as the weight change
b(t)la of the sol, and an elapsed time "t" corresponding to the selected value can be set as
the holding time in the drying step.
[0033]
[Pressing step]
After the elapsed time set as described above, the mold in which a predetermined
minute concavity and convexity pattern is formed is pressed against the coating film with
the pressing roll. A roll process using the pressing roll has the following advantages as
compared with a pressing system: i) the period of time during which the mold and the
coating film are brought in contact with each other in the roll process is shorter than that in
the pressing system, and thus it is possible to prevent deformation of the pattern caused by
difference among coefficients of thermal expansion of the mold, the substrate, a stage on
which the substrate is provided, and the like; ii) productivity is improved by the roll
process and the productivity is further improved by use of a long mold; iii) it is possible to
prevent generation of bubbles of gas in the pattern caused by bumping of the solvent in the
gel solution and/or it is possible to prevent a trace or mark of gas from being left; iv) it is
possible to reduce transfer pressure and peeling force because of line contact with the
substrate (coating film), and thereby making it possible to deal with a larger substrate
readily: and v) no bubble is involved during the pressing.
[0034] It is possible to use arbitrary pressing roll (transfer roll), and the pressing roll
preferably includes a surface having a film coated with a resin material such as ethylene
propylene diene rubber (EPDM), silicone rubber, nitrile rubber, fluororubber, acrylic
14
rubber, and chloroprene rubber. A support roll may be provided to face the pressing roll
while sandwiching the substrate therebetween in order to resist pressure applied by the
pressing roll. Alternatively, a support base supporting the substrate may be provided.
[0035] When the mold is pressed with the pressing roll, while the surface of the coating
film on the substrate is covered with the mold, the pressing roll can be moved and rotated
relative to the surface of the coating film. Alternatively, it is allowable to use, as the press
roll, a roll having the mold previously wound on the outer circumference thereof. When
the pressing is performed, a roll temperature can be maintained at 10 to 150 degrees
Celsius.
LO0361 When the mold is pressed against the coating film by use of the pressing roll, the
mold may be pressed against the coating film while the coating film is heated (referred to
as "hot press" as appropriate). By pressing the mold against the coating film while
heating the coating film, gas generated by the heating can escape to the outside of the
system from the side (or portion) at which the mold engages with the coating film by the
pressing roll, without remaining between the coating film and the mold (film mold), and
thereby obtaining an effect that a void is unlikely to be formed. Further, the hot press can
shorten a period of time elapsed between the pressing of the mold and the peeling of the
mold, and can perform the pre-baking step which will be described later in the pressing
step (that is, the pre-baking step may be omitted). As a method for heating the coating
film, for example, the heating may be performed through the pressing roll, or the coating
film may be heated directly or from the side of the substrate. In a case that the heating is
performed through the pressing roll, a heating means may be provided in the pressing roll
(transfer roll), and any heating means can be used. Although it is preferable that a heater
is included in the pressing roll, it is allowable that the heater is provided separately from
the pressing roll. In any case, arbitrary pressing roll may be used provided that the
coating film can be pressed while being heated.
100371 The heating temperature of the coating film at the time of the hot press may be in
a range 01-40 degrees Celsius to 150 degrees Celsius. Similarly, in a case that the heating
is performed by use of the pressing roll, the heating temperature of the pressing roll may be
in a range of 40 degrees Celsius to 150 degrees Celsius. By heating the pressing roll as
described above, the mold can be easily peeled off from the coating film against which the
mold has been pressed, and thereby making it possible to improve the productivity. In a
case that the heating temperature of the coating film or the pressing roll is less than 40
15
degrees Celsius, the mold can not be expected to be peeled off from the coating film
quickly. In a case that the heating temperature of the coating film or the pressing roll
exceeds 150 degrees Celsius, the solvent used evaporates so rapidly that there is fear that
the concavity and convexity pattern is not transferred sufficiently. The support roll (as
will be described later) provided on the lower side of the pressing roll may also be heated,
for example, to temperatures of 40 degrees Celsius to 150 degrees Celsius. As a means
for heating the coating film, not only the heating of the pressing roll but also various
specific embodiments which will be described later can be adopted.
[0038]
The mold is peeled off from the coating film (sol-gel material layer) after the
pressing step or the pre-baking step. Since the roll is used as described above, the peeling
force may be smaller than that in the case of using a plate-shaped mold, and it is possible
to easily peel off the mold from the coating film without remaining the coating film on the
mold. In order to promote the mold peeing, it is possible to use a peeling roll as will be
described later (see Fig. 5). By providing the peeling roll on the downstream side of the
pressing roll and rotating and supporting the mold while urging the mold toward the
coating film, a state in which the mold is attached to the coating film can be maintained for
a certain period of time, and the coating film can be subjected to the pre-baking during the
certain period of time. In a case that the peeling roll is used, a portion where the mold is
peeled subsequently moves to make the peeling force small. Thus, as compared with a
case in which the mold is peeled off at once, the pattern is less likely to be collapsed. In a
case that the mold is peeled off while heating the peeling roll, for example, at temperatures
of 40 degrees Celsius to 150 degrees Celsius, it is possible to peel off the mold from the
coating film more easily.
[OOSO]
[Main baking step]
After the mold is peeled off from a coating film (sol-gel material layer) 42 on a
substrate 40, the coating film is subjected to the main baking (main sintering or main
calcinating). Hydroxyl group and the like contained in silica (amorphous silica) forming
the coating film is desorbed or eliminated by the main baking to further strengthen the
coating film. The main baking may be performed at temperatures of 200 degrees Celsius
to 1200 degrees Celsius for about 5 minutes to 6 hours. Accordingly, the coating film is
cured, and thereby the substrate with the concavity and convexity pattern film which
corresponds to the concavity and convexity pattern of the mold, that is, the substrate in
which the sol-gel material layer having the concavity and convexity pattern is directly
formed on the flat substrate, is obtained. In this situation, depending on a baking
temperature and a baking time, the silica, as the sol-gel material layer, is amorphous,
crystalline, or in a mixture state of the amorphous and the crystalline.
[OOSl]
[Manufacturing apparatus]
In order to carry out the method of the present invention, it is possible to use, for
example, an apparatus 1 OOa for manufacturing the substrate having the concavity and
2 1
convexity pattern, as shown in Fig. 5. The apparatus 100a mainly includes a die coater 30
for applying the sol on the substrate 40; a transport system 20 for transporting a long mold
50; and a heater 32 for heating the coating film. The transport system 20 includes a
feeding roll 21 which feeds the mold 50; a pressing roll 22 which presses the mold 50 to
the side of the coating film 42 formed on the substrate 40; a support roll 25 which is
provided to face the pressing roll 22 to press the substrate 40 from the lower side of the
substrate and which is rotationally driven to feed the substrate to the downstream side in a
substrate transport direction; a peeling roll 23 which is provided on the downstream side of
the pressing roll 22 to peel off the mold 50 after a state, in which the mold 50 is pressed
against the coating film on the substrate, is maintained over a predetermined distance; and
a winding roll 24 which is provided on the downstream side ofthe peeling roll to wind or
roll up the mold. The heater 32 is used for the pre-baking and is positioned between the
pressing roll 22 and the peeling roll 23 in the substrate transport direction. It is possible
to use, for example, an infrared heater, hot-air heating, and a hot plate as the heater 32.
[0052] An explanation will be made about an operation for processing the substrate by
use of the apparatus 1OOa. The sol is applied on the substrate 40 by the die coater 30
while the substrate 40 sandwiched between the pressing roll 22 and the support roll 25 is
moved to the downstream side. The coating film 42 obtained by applying the sol arrives
at the pressing roll 22 after the elapse of a predetermined moving time of the substrate and
then the concavity and convexity pattern of the mold 50 fed by the feeding roll 21 is
pressed against the coating film 42. The substrate 40 is transported in a state that the .
concavity and convexity pattern of the mold 50 is pressed against the coating film 42, and
the coating film 42 is subjected to the pre-baking when passing above the heater 32. The
mold 50 is drawn or pulled upward by the winding roll 24 when passing through the
peeling roll 23, so that the mold 50 is peeled off from the coating film 42. Subsequently,
the substrate on which the pattern is formed is subjected to the main baking in an oven
provided separately from the apparatus 100a. It is allowable to provide a heater in the
manufacturing line as the oven used for the main baking.
[0053] In the apparatus 100a, a peeling angle may be adjusted by controlling or
regulating the installation position of the peeling roll 23 and/or the position of the winding
roll 24 which winds or rolls up the mold via the peeling roll 23. The heater 32 may be
provided on the side of the coating film 42 relative to the substrate 40, and it is possible to
use any other driving means such as a movable table which moves while supporting the
22
substrate, instead of the support roll 25. Further, although the peeling roll 23 is used to
maintain the state, in which the concavity and convexity pattern of the mold 50 is pressed
against the coating film 42 with the pressing roll 22 while the coating film 42 is subjected
to the pre-baking by the heater 32, it is allowable to use any other support member such as
a plate-shaped member having a smooth surface and a corner with a curved surface,
instead of the peeling roll 23, in order to maintain the above state. The mold 50 is formed
as the long mold and the end portions thereof are wound on the feeding roll 21 and the
winding roll 24, respectively. The mold 50, however, may be formed to be an endless
belt like an apparatus 100b shown in Fig. 6. The mold 50 formed to be the endless belt
enables a continuous pressing operation also in a manufacturing line in which many
substrates are continuously transported for mass production.
[0054] Fig. 7 shows an exemplary apparatus used when the hot press is performed in the
pressing step. An apparatus 100c shown in Fig. 7 has basically the same structure as the
apparatus 100a shown in Fig. 5, except that the pressing roll 22 includes therein a heater
22a. Although a heater 33 shown in Fig. 5 may be provided between the pressing roll 22
and the peeling roll 23 in the substrate transport direction, since the pressing roll 22 is
provided with the heater 22a, the heater 33 can be omitted. In the apparatus 100c, the
coating film 42 obtained by applying the sol arrives at the hot press roll 22 after the elapse
of a predetermined moving time of the substrate, and then the concavity and convexity
pattern of the mold 50 fed by the feeding roll 21 is pressed against the coating film 42
while being heated.
[0055] In the apparatus 100c, a peeling angle may be adjusted by controlling or
regulating the installation position of the peeling roll 23 and/or the position of the winding
roll 24 which winds or rolls up the mold via the peeling roll 23. It is possible to use any
other driving means such as a movable table which moves while supporting the substrate,
instead of the support roll 25. Although the peeling roll 23 is used to maintain the state,
in which the concavity and convexity pattern of the mold 50 is pressed against the coating
film 42 with the pressing roll 22, it is allowable to use any other support member such as a
plate-shaped member having a smooth surface and a corner with a curved surface, instead
of the peeling roll 23, in order to maintain the above state. The mold 50 is formed as a
long mold and the end portions thereof are wound on the feeding roll 21 and the winding
roll 24, respectively. The mold 50, however, may be formed to be an endless belt like an
apparatus 100d shown in Fig. 8. The mold 50 formed to be the endless belt enables a
2 3
continuous pressing operation also in a manufacturing line in which many substrates are
continuously transported for mass production.
[0056] Fig. 9 shows an exemplary apparatus in which no peeling roll is provided. In an
apparatus 100e shown in Fig. 9, the mold 50 fed from a feeding roll 26 is pressed against
the coating film 42 with the hot press roll 22, and then the mold 50 is directly wound or
lifted with a winding roll 27 to rotate. In the present invention, since the pressing roll is
heated, the peeling of the mold from the coating film immediately after the pressing is
helped. Thus, it is possible to simplify the apparatus by omitting the peeling roll and
improve productivity of the process. It is allowable that the feeding roll and the winding
roll are not provided and the mold is wound around the hot press roll directly.
[0057] As shown in an apparatus 1OOf shown in Fig. 10, instead of providing the heater
22a in the pressing roll 22, the heater 22a may be provided in the support roll 25. In this
case, the coating film 42 is subjected to the pre-baking by heat generated from the heater
22a provided in the support roll 25. Alternatively, the heater 22a may be provided both in
the pressing roll 22 and in the support roll 25.
[0058] Fig. 11 shows another modified example of the arrangement of the heater 22a.
Instead of providing the heater 22a in the pressing roll 22, the heater 22b may be provided
immediately below the pressing roll 22 as in the case of an apparatus 100g shown in Fig.
11. In this case, the coating film 42 is subjected to the pre-baking by the heater 22b
provided immediately below the pressing roll 22. Alternatively, the heater 22a and 22b
may be provided both inside the pressing roll and at the position immediately below the
pressing roll 22.
[0059] Fig. 12 shows still another example of the arrangement of the heater 22a. As
shown in Fig. 12, instead of providing the heater 22a in the pressing roll 22, an apparatus
100h includes the heater 22b in a heat zone 35 which is arranged at the periphery of the
pressing roll 22 by being partitioned by a separation wall. Since the heater is provided in
the heat zone 35, the inside of the heat zone is maintained at a heating temperature. In
this case, the coating film 42 is subjected to the pre-baking in the heat zone 35. The
heater may be provided not only in the heat zone 35 but also in the support roll 25.
[0060] The substrate, in which the pattern made of the sol-gel material layer 42 is formed
through the roll process as described above, can be used as, for example, a
diffraction-grating substrate for organic EL element, a wire grid polarizer, an antireflection
film, and an optical element for providing an effect of a confinement of light within a solar
24
cell by being placed on the photoelectric conversion surface side of the solar cell. Or, the
pattern may be transferred to yet another resin by using the substrate having the pattern as
the mold (mother die). In this case, the transferred resin pattern is an inverted pattern of
the pattern on the substrate. Thus, it is allowable to produce a mold as a replica of the
substrate by transferring the transferred inverted pattern to yet another resin. Each of the
molds can be subjected to an electroforming process using Ni and the like to form a
metallic mold. The use of each of the molds enables efficient mass production of an
optical component such as the diffraction-grating substrate for organic EL element.
[0061]
An explanation will be made about a method for producing an organic EL element
by use of the substrate, in which the pattern made of the sol-gel material layer is formed
through the roll process as described above, while referring to Fig. 13. At first, as shown
in Fig. 13, a transparent electrode 92 is stacked on the sol-gel material layer 42 on the
substrate 40 to maintain the concave and convex structure formed on the surface of the
sol-gel material layer 42. As a material for the transparent electrode 92, for example,
indium oxide, zinc oxide, tin oxide, indium-tin oxide (ITO) which is a composite material
thereof, gold, platinum, silver, or copper can be used. Of these materials, IT0 is
preferable from the viewpoint of transparency and electrical conductivity. The thickness
of the transparent electrode 92 is preferably in a range of 20 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 emitted EL light cannot be extracted to the outside
sufficiently. As a method for stacking the transparent electrode 92, any known method
such as a vapor deposition method, a sputtering method, and a spin coating method can be
employed as appropriate. Of these methods, the sputtering method is preferably
employed from the viewpoint of improving the adhesion property.
[0062] Next, an organic layer 94 as shown in Fig. 13 is stacked on the transparent
electrode 92. The organic layer 94 is not particularly limited, provided that the organic
layer 94 is usable as an organic layer of the organic EL element. As the organic layer 94,
any known organic layer can be used as appropriate. The organic layer 94 may be a
stacked body of various organic thin films. For example, the organic layer 94 may be a
stacked body of a hole transporting layer 95, a light-emitting layer 96. and an electron
25
transporting layer 97 as shown in fig. 13. Here, examples of materials of the hole
transporting layer 95 include aromatic diamine compounds such as phthalocyanine
derivatives, naphthalocyanine derivatives, porphyrin derivatives,
N,N y-bis(3-methylphenyl)+ 1,l '-biphenyl)4,4'-diamine (TPD), and
4,4'-bis[N-(naphthyl~N-phenyl-amino]biphenyl(a-NPD); oxazole; oxadiazole; triazole;
imidazole; imidazolone; stilbene derivatives; pyrazoline derivatives; tetrahydroimidazole;
polyarylalkane; butadiene; and
4,4',4"-tris(N-(3-methylphenyl)N-phenylamino)triphenylamine (m-MTDATA). The
materials of the hole transporting layer, however, are not limited thereto. By providing
the light emitting layer 96, a hole injected from the transparent electrode 92 and electron
injected from a metal electrode 98 are recombined to occur light emission. Examples of
materials of 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. Further, it is preferable that
light-emitting materials selected from the above compounds are mixed as appropriate and
then are used. Furthermore, 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. The phosphorescence
emitting material preferably includes heavy metal such as iridium. A host material having
high carrier mobility may be doped with each of the light-emitting materials as a guest
material to generate the light emission using dipole-dipole interaction (Forster mechanism),
or electron exchange interaction (Dexter mechanism). Examples of materials 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 derivarives,
oxadiazole derivatives, and aluminum-quinolinol complex (Alq3). Further, in the
oxadiazole derivatives mentioned above, it is also possible to use, as an electron
26
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 chain of the macromolecular chain. It is noted that
the hole transporting layer 95 or the electron transporting layer 97 may also function as the
light-emitting layer 96. In this case, there are two organic layers between the transparent
electrode 92 and the metal electrode 98.
[0063] From the viewpoint of facilitating the electron injection from the metal electrode
98, it is allowable to provide, between the organic layer 94 and the metal electrode 98 as an
electron injecting layer, a layer made of a metal fluoride such as lithium fluoride (LiF), a
metal oxide such as or Li203, a highly active alkaline earth metal such as Ca, Ba, or Cs, an
organic insulating material, or the like. In addition, from the viewpoint of facilitating the
hole injection from the transparent electrode 92, it is allowable to provide, between the
organic layer 94 and the transparent electrode 92 as the hole injecting layer, a layer made
of triazole derivatives; oxadiazole derivatives; imidazole derivatives; polyarylalkane
derivatives; pyrazoline derivatives and pyrazolone derivatives; phenylenediamine
derivatives; arylamine derivatives; amino-substituted chalcone derivatives; oxazole
derivatives; styrylanthracene derivatives; fluorenon derivatives; hydrazone derivatives;
stilbene derivatives; silazane derivatives; aniline copolymer; or a conductive polymer
oligomer, in particular, thiophene oligomer, or the like.
[0064] 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 in a range of 1 to 200 nm, in a range of 5 to 100 nm,
and in a range of 5 to 200 nm, respectively. As a method for stacking the organic layer 94,
any known method such as a vapor deposition method, a sputtering method, a spin coating
method, and a die coating method can be employed as appropriate.
[0065] Subsequently, as shown in Fig. 13, the metal electrode 98 is stacked on the organic
layer 94 in the step of forming the organic EL element. 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 in a range of 50 to 500 nm. In a case
27
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 or restoration is difficult when a short circuit between electrodes occurs. Any
known method such as a vapor deposition method and a sputtering method can be adopted
to stack the metal electrode 98. Accordingly, an organic EL element 200 having a
structure as shown in Fig. 13 can be obtained.
Examples
[0066]
[Example 11
2.5 g of tetraethoxysilane (TEOS) and 2.1 g of methyltriethoxysilane (MTES)
were added by drops to a mixture 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. The doctor blade was designed
so that the film thickness of the coating film was 5 pm. However, the doctor blade was
adjusted so that the film thickness of the coating film was 40 pn by sticking an imide tape
having a thickness of 35 pm to the doctor blade. The weight of the glass plate (glass
substrate) after the bar coating was weighed every time when a predetermined period of
time elapses by use of an electric weighing machine (produced by Kensei Industry Co.,
Ltd., electromagnetic weighing machine "GH-202"). Then, the weight (b(t)) of the
coating film was obtained for each elapsed time by subtracting the weight of the glass
substrate which was weighed in advance. Further, the glass substrate was subjected to a
heating process on a hot plate at a temperature of 100 degrees Celsius for 5 minutes to dry
the coating film, and the weight of the glass substrate was weighed by the electric
weighing machine. Then, the weight of the dried film (a= 8.6 mg) was obtained by
1
subtracting the weight of the glass substrate which was weighed in advance. The ratio
(e= b(t)/a) of weight of the coating film to a dried weight "a" of the coating film was
calculated for each elapsed time "t", and evaluation of the transfer of the coating film was
performed based on the weight ratio as follows. Fig. 2 shows a graph showing the
variation of the ratio (e= b(t)/a) of weight of the coating film to the dried weight of the
coating film for each elapsed time (second).
[0067] The sol was prepared under the same conditions, and then the sol was applied on a
28
soda-lime glass plate by the bar coating as those described above. After the application of
the sol, a mold having a line-and-space pattern was pressed against the coating film on the
glass plate with a pressing roll, for each elapsed time which was the same as that when the
weight of the glass substrate was obtained, in the following manner.
[0068] The mold having the line-and-space pattern was made as follows. The
line-and-space pattern was formed on a silicon substrate by electron beam lithography as a
master. The pattern of the master was transferred on a fluorine-containing photo-curable
resin layer applied on a PET film to prepare the mold. As shown in Fig. 14(a), the mold
was a sheet 70 of 300 mm x 200 mm x 0.1 (thickness) mm, and four line-and-space
patterns (each having 1 cm x 1 cm) 72,74,76,78, which had concave and convex grooves
extending in mutually different directions,and each of which was formed providing a
predetermined spacing distance therebetween, were formed in a surface of the sheet 70.
As shown in Fig. 14(b), each of the patterns was formed to be partitioned into three, and
three portions of the partitioned pattern had pitches of 400 nm, 600 nm, and 800 nm,
respectively. The concavities and convexities in each of the three portions of the
partitioned pattern had a depth of 175 nm. Fig. 14(c) is a cross-sectional view of the
partitioned pattern having a pitch of 400 nm. As the pressing roll, it was used a roll
which had an outer periphery covered with EPDM having a thickness of 3 mm; had a roll
diameter (9) of 70 mm; and had a length of 500 mm in the axial direction of the shaft.
[0069] At first, the surface, of the mold, on which the line-and-space pattern has been
formed was pressed against the coating film on the glass substrate while rotating the
pressing roll of which temperature was 23 degrees Celsius (room temperature) from one
end to the other end of the glass substrate. Immediately after the completion of the
pressing, the substrate was moved on a hot plate and then heated at a temperature of 100
degrees Celsius (pre-baking). After continuing the heating for 5 minutes, the substrate
was removed from the hot plate and the mold was manually peeled off from the substrate
from an end portion thereof. The mold was peeled off such that the angle (peel angle) of
the mold with respect to the substrate was about 30".
[0070] After peeling off the mold from the substrate, the transfer state of the
line-and-space pattern on the coating film was observed visually. When the
line-and-space pattern on the coating film could be observed, it was evaluated as
transferable. The evaluation results are shown in Table 1. Table 1 shows the time
elapsed after the application and before the pressing; the weight of the coating film; the
2 9
ratio of weight of the coating film to the dried weight of the coating film; and the
evaluation results. In a case that the line-and-space pattern was clearly transferred on the
coating film, it is expressed as "+" and in a case that no line-and-space pattern was
observed and evaluated as transfer failure, it is expressed as "-" in each column of Table 1.
[0071] (TABLE 1>
[0072] 'The results in Table 1 show that the transfer was satisfactory in a case that the
Time elapsed after
application
(second)
-- - 10 -- -
2 0
30
40
-50
60
70
80
90
ratio of weight of the coating film to the dried weight of the coating film was in a range of
Weight ratio to dried film
(* 1)
8.76
7.69
6.69
5.85
5.09
4.49
3.92
3.44
Weight of
coating film (mg)
--
75.3
66.1
57.5
50.3
43.8
38.6
33.7
29.6
1.30
1.30
1 .OO
300 I 11.2
1.4 to 8.8. That is, in terms of the time elapsed after the application, the transfer was
Evaluation
+
+
+
+
+
+
+
+
* 1 The weight of the film dried at 100 degrees Celsius for 5 minutes was defined as 1.
3 10
Drying at I00 deg C
for 5 minutes
satisfactory in a case that the elapsed time was in a range of 20 seconds to 240 seconds.
3 0
11.2
8.60
Note that in a case that the weight exceeded 4.0, the sol applied by the bar coater flowed
and leaked from the substrate, so that the sol came around behind the substrate. This
made an area around the substrate dirty.
[0073] Of the glass substrates each having the coating film to which the line-and-space
pattern was transferred, the substrate(s) to which the line-and-space pattern was clearly
transferred was(were) subjected to a main baking by heating the substrate(s) for 60 minutes
in an oven of 300 degrees Celsius.
[0074)
[Example 21
A sol was prepared in the same manner as Example 1, except that 3 1.7 g of
isopropyl alcohol (IPA) was used instead of ethanol used in the sol. A spin coating
method was used as the method for applying the sol other than the bar coating method.
The spin coating was performed at a spin speed of 500 rpm for 8 seconds, and then
performed at a spin speed of 1000 rpm for 3 seconds. The weight of the glass substrate
was weighed for each elapsed time after the spin coating in the same manner as Example 1.
Then, it was obtained the ratio of weight of the glass substrate to the weight (dried weight)
of the substrate, the dried weight being obtained by heating the substrate at a temperature
of 100 degrees Celsius for 5 minutes. Fig. 15 shows the variation of the ratio (e= b(t)/a)
of weight of the coating film to the dried weight of the coating film for each elapsed time
after the spin coating. Subsequently, the mold was pressed against the coating film of the
sol, which was obtained by performing the spin coating on the glass substrate, by use of the
pressing roll of which temperature was 23 degrees Celsius, while the pressing roll was
moved and rotated, for each elapsed time in the same manner as Example 1. After the
completion of pressing of the coating film, the mold was manually peeled off from the
substrate after the substrate was heated at a temperature of 100 degrees Celsius in the same
manner as Example 1. Then, the pattern transferred to the coating film was observed and
evaluated.
[0075] Table 2 shows the evaluation results. The following is understood from the
results. That is, even when the sol is applied by the spin coater and when isopropyl
alcohol is used as the solvent of the sol, the transfer can be performed satisfactorily
provided that the ratio "e" of weight of the coating film to the dried weight of the coating
film is not less than 1.4.
Time elapsed after
application
(second)
[0077]
[Example 31
In this Example, a mold having a concave and convex surface was produced by
using the BCP method, and then a diffraction grating and an organic EL element including
the diffraction grating were produced using the produced mold and the pressing roll used in
Example 1. At first, it was prepared a block copolymer produced by Polymer Source Inc.,
which was made of polystyrene (hereinafter referred to as "PS" in an abbreviated manner
as appropriate) and polymethyl methacrylate (hereinafter referred to as "PMMA" in an
abbreviated manner as appropriate) as described below.
Mn of PS segment= 868,000
Mn of PMMA segment= 857,000
Mn of block copolymer = 1,725,000
Volume ratio between PS segment and PMMA segment (PS:PMMA)= 53:47
Molecular weight distribution (MwNn)= 1.30
'Tg of PS segment= 96 degrees Celsius
'Tg of PMMA segment= 1 10 degrees Celsius
[0078] 'The volume ratio of the first polymer segment and second polymer segment (the
first polymer segment : the second polymer segment) in each block copolymer was
calculated on the assumption that the density of polystyrene was 1.05 g/cm3, the density of
polymethyl methacrylate was 1.19 gl cm3. The number average molecular weights (Mn)
3 2
110
120
Drying at 100 deg C
for 5 minutes
Weight of
coating film (mg)
* 1 The weight of the film dried at 100 degrees Celsius for 5 minutes was defined as 1
12.9
12.9
9.40
Weight ratio to dried film
('1)
Evaluation
1.37
1.37
1 .OO
-
-
and the weight average molecular weights (Mw) of polymer segments or polymers were
measured by using gel permeation chromatography (Model No: "GPC-8020" manufactured
by Tosoh Corporation, in which TSK-GEL SuperH1000, SuperH2000, SuperH3000, and
SuperH4000 were connected in series). The glass transition temperatures (Tg) of
polymer segments were measured by use of a differential scanning calorimeter
(manufactured by Perkin-Elmer under the product name of "DSC7"), while the temperature
was raised at a rate of temperature rise of 20 degrees Celsius/min 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).
[0079] Toluene was added to 150 mg of the block copolymer and 38 mg of
Polyethylene Glycol 4000 manufactured by Tokyo Chemical Industry Co., Ltd. (Mw=
3000, Mw/Mn= 1.10) as polyethylene oxide so that the total amount thereof was log,
followed by dissolving them. Then, the solution was filtrated or filtered through a
membrane filter having a pore diameter of 0.5 pm to obtain a block copolymer solution.
The obtained block copolymer solution was applied, on a polyphenylene sulfide film
(TORELINA manufactured by TORAY INDUSTRIRES, INC.) as a base member, in a film
thickness of 200 to 250 nm, by a spin coating. The spin coating was performed at a spin
speed of 500 rpm for 10 seconds, and then performed at a spin speed of 800 rpm for 30
seconds. The thin film applied by the spin coating was left at room temperature for 10
minutes until the thin film was dried.
[OOSO] Subsequently, the base member on which the thin film was formed was heated for
5 hours in an oven of 170 degrees Celsius (first annealing process). Concavities and
convexities were observed on a surface of the heated thin film, and it was found out that
micro phase separation of the block copolymer forming the thin film was caused.
[OOSl] The thin film heated as described above was subjected to an etching process as
described below to selectively decompose and remove PMMA on the base member. The
thin film was irradiated with UV light at an irradiation intensity of 30~/cm(w~a velength of
365 nm) by use of a high pressure mercury lamp. Then, the thin film was immersed in
acetone, and was subjected to cleaning with ion-exchanged water, followed by being dried.
As a result, there was formed, on the base member, a concavity and convexity pattern
clearly deeper than the concavities and convexities which appeared on the surface of the
thin film by the heating process.
[0082] Next, the base member was subjected to a heating process (second annealing
process) for 1 hour in an oven of 140 degrees Celsius so that the concavity and convexity
pattern formed by the etching process was deformed to have a chevron-shaped structure
(process for forming a shape of chevrons).
[0083] A thin nickel layer of about 10 nm was formed as a current seed layer by
sputtering on the surface of the thin film, for which the process for forming the shape of
chevrons had been performed. Subsequently, the base member with the thin film was
subjected to an electroforming process (maximum current density: 0.05~1cm~in )a nickel
sulfamate bath at a temperature of 50 degrees Celsius to precipitate nickel until the
thickness of nickel became 250 pm. The base member with the thin film was
mechanically peeled off from the nickel electroforming body obtained as described above.
Subsequently, the nickel electroforming body was immersed in Chemisol 2303
manufactured by The Japan Cee-Bee Chemical Co., Ltd., followed by being cleaned while
being stirred for 2 hours at 50 degrees Celsius. Thereafter, polymer component(s)
adhered to a part of the surface of the electroforming body was(were) removed by
repeating the following process three times. That is, an acrylic-based UV curable resin
was applied on the nickel electroforming body; and the applied acrylic-based W curable
resin was cured; and then the cured resin was peeled off.
[0084] Subsequently, the nickel electroforming body was immersed in OPTOOL
HD-2 100TH manufactured by Daikin Industries, Ltd. for about 1 minute and was dried,
and then stationarily placed overnight. The next day, the nickel electroforming body was
immersed in OPTOOL HD-TH manufactured by Daikin Industries, Ltd. to perform an
ultrasonic cleaning process for about 1 minute. Accordingly, a nickel mold (nickel
substrate) for which a mold-release treatment had been performed was obtained.
[0085] Subsequently, a fluorine-based UV curable resin was applied on a PET substrate
(easily-adhesion PET film manufactured by Toyobo Co., Ltd., product name:
COSMOSHlNE A-4100). Then, the fluorine-based UV curable resin was cured by
irradiation with the UV light at 600 m~lcmw~i,th the obtained nickel mold being pressed
against the PET substrate. AFter curing of the resin, the nickel mold was peeled off from
the cured resin. Accordingly, a diffraction grating mold made of the PET substrate with
the resin film to which the surface profile of the nickel mold was transferred was obtained.
[0086] After the elapse of 60 seconds from the application of sol on the glass substrate by
performing the bar coating, the diffraction grating mold was pressed against the coating
34
film of the sol, by use of the pressing roll of which temperature was 30 degrees Celsius,
while the pressing roll was moved and rotated, in the same manner as Example 1. After
the completion of pressing against the coating film, the mold was manually peeled off from
the substrate after the substrate was heated at a temperature of 100 degrees Celsius in the
same manner as Example 1. Then, the substrate was subjected to the main baking by
heating the substrate for 60 minutes in an oven of 300 degrees Celsius, and the pattern
transferred to the coating film was evaluated.
[0087] An analysis image of the shape of the concavities and convexities on the surface
of the coating film in the diffraction grating was obtained by use of an atomic force
microscope (a scanning probe microscope equipped with an environment control unit
"Nanonavi I1 StatiodE-sweep" manufactured by SII NanoTechnology Inc.). Analysis
conditions of the atomic force microscope were as follows.
Measurement mode: dynamic force mode
Cantilever: S1-DF40 (material: Si, lever width: 40 pn, diameter of tip of chip: 10 nm)
Measurement atmosphere: in air
Measurement temperature: 25 degrees Celsius
[0088]
A concavity and convexity analysis image was obtained as described above by
performing a measurement in a randomly selected measuring region of 3 pm square
(length: 3 pm, width: 3 pm) in the diffraction grating. Distances between randomly
selected concave portions and convex portions in the depth direction were measured at 100
points or more in the concavity and convexity analysis image, and the average of the
distances was calculated as the average height (depth) of the concavities and convexities.
The average height of the concavity and convexity pattern obtained by the analysis image
in this example was 56 nm.
[0089]
A concavity and convexity analysis image was obtained as described above by
performing a measurement in a randomly selected measuring region of 3 pm square
(length; 3 pm, width 3 pm) in the diffraction grating. The obtained concavity and
convexity analysis image was subjected to a flattening process including primary
inclination correction, and then subjected to two-dimensional fast Fourier transform
3 5
processing. Thus, a Fourier-transformed image was obtained. 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 the absolute value of wavenumber was in a range of 10 pm-I
or less.
[0090] The circular pattern of the Fourier-transformed image is a pattern 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 a contour looks like a
convex shape or a concave shape. The gathering of the bright spots may look like a
substantially annular shape, and this case is expressed as 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 value of wavenumber is in a
range of 10 pm-' or less (more preferably from 1.25 to 10 pm-', further preferably from
1.25 to 5 pm-I) " means that 30% or more (more preferably 50% or more, further more
preferably 80% or more, and particularly preferably 90% or more) of bright spots forming
the Fourier-transformed image are present within a region where the absolute value of
wavenumber is in a range of 10 pm-' or less (more preferably from 1.25 to 10 pm-I, and
further preferably from 1.25 to 5 pm-I). Regarding the relationship between the pattern of
the concavity and convexity structure and the Fourier-transformed image, the followings
have been appreciated. That is, in a case that the concavity and convexity structure itself
has neither the pitch distribution nor the directivity, the Fourier-transformed image appears
to have a random pattern (no pattern). In a case that the concavity and convexity
structure is entirely isotropic in an XY direction and has the pitch distribution, a circular or
annular Fourier-transformed iinage appears. In a case that the concavity and convexity
structure has a single pitch, the annular shape appeared in the Fourier-transformed image
tends to be sharp.
100911 'I'he two-dimensional fast Fourier transform processing on the concavity and
convexity analysis image can be easily performed by electronic image processing by use of
a computer equipped with software for the two-dimensional fast Fourier transform
36
processing.
[0092] As a result of the image analysis of the obtained Fourier-transformed image, the
wavenumber 2.38 pm-' was the most intensive. That is, the average pitch was 420 nm.
The average pitch could be obtained as follows. For each of points of the
Fourier-transformed image, the intensity and distance (unit: pm") from the origin of the
Fourier-transformed image were obtained. Then, the average value of the intensity was
obtained for the points each having the same distance from the origin. As described
above, a relationship between the distance from the origin of the Fourier-transformed
image and the average value of the intensity was plotted, a fitting with a spline function
was carried out, and the wavenumber of the peak intensity was regarded as the average
wavenumber (pm-I). For the average pitch, it is allowable to make a calculation by
another method, for example, a method for obtaining the average pitch of the concavities
and convexities as follows. That is, a concavity and convexity analysis image is obtained
by performing a measurement in a randomly selected measuring region of 3 pn square
(length: 3 pm, width: 3 pm) in the diffraction grating, then the distances between randomly
selected adjacent convex portions or between randomly selected adjacent concave portions
are measured at 100 points or more in the concavity and convexity analysis image, and
then an average of these distances is determined.
[0093]
The glass substrate with the pattern made of the sol-gel material layer as the
diffraction grating obtained as described above was cleaned with a brush to remove foreign
matter and the like adhered thereto, then organic matter and the like was removed by an
alkaline cleaner and an organic solvent. On the substrate cleaned as described above, a
film of IT0 having a thickness of 120 nm was formed at a temperature of 300 degrees
Celsius by a sputtering method. A photoresist was applied and an exposure was
performed with an electrode mask pattern, and then an etching was performed by a
developer. Accordingly, a transparent electrode having a predetermined pattern was
obtained. The obtained transparent electrode was cleaned with the brush, and the organic
matter and the like was removed by the alkaline cleaner and the organic solvent. Then,
the transparent electrode was subjected to a UV-ozone process. On the transparent
electrode processed as described above, a hole transporting layer (4,4',4"
tris(9-carbazole)triphenylamine, thickness: 35 nm), a light emitting layer
37
(tris(2-phenylpyridinato)iridium(III) complex-doped
4,4',4"tris(9-carbazole)triphenylamine, thickness: 15 nm;
tris(2-phenylpyridinato)iridium(III) complex-doped
1,3,5-tris(N-phenylbenzimidazole-2-y1)benzene thickness: 15 nm), an electron
transporting layer (1,3,5-tris(N-phenylbenzimidazole-2-y1)benzeneth ickness: 65 nm), and
a lithium fluoride layer (thickness: 1.5 nm) were each stacked by a vapor deposition
method, and further a metal electrode (aluminum, thickness: 50 nm) was formed by the
vapor deposition method. Accordingly, the organic EL element in which the concavity
and convexity structure was maintained was obtained as shown in Fig. 13.
[0094] In the process as described above, the substrate produced in accordance with the
method of the present invention was formed of the sol-gel material and had the superior
mechanical strength. Thus, even when the cleaning with the brush was performed for the
substrate and the surface of the concavity and convexity pattern after formation of the
transparent electrode as described above, damage, adhesion of the foreign matter,
projection on the transparent electrode and the like were less likely to occur, and thereby
any element failure therefrom could be suppressed. Therefore, the organic EL element
obtained by the method of the present invention was superior, as compared with a case in
which a curable resin substrate was used, in terms of the mechanical strength of the
substrate having the concavity and convexity pattern. Further, the substrate made of the
sol-gel material produced in accordance with the method of the present invention had a
satisfactory chemical resistance and the alkali resistance superior to the substrate formed of
a curable resin material. Therefore, the substrate had a certain corrosion resistance to
alkaline fluid and the organic solvent used for the cleaning step of the substrate and the
transparent electrode, and thus it is possible to use various cleaning liquids. Further, an
alkaline developer is used at the time of the patterning of the transparent substrate in some
cases, and the substrate in the present invention also has the corrosion resistance to such a
developer. In this respect, the substrate in the present invention has an advantage over the
curable resin substrate having a generally low resistance in the alkaline fluid. Further, the
substrate formed of the sol-gel material produced in accordance with the method of the
present invention has a superior UV resistance and a superior weather resistance as
compared with the curable resin substrate. Therefore, the substrate in the present
invention also has the resistance to the UV-ozone cleaning process after the formation of
the transparent electrode. Further, in a case that the organic EL element produced by the
3 8
method of the present invention is used outside or outdoors, it is possible to suppress the
deterioration due to sunlight as compared with the case in which the curable resin substrate
is used.
[0095]
The light emission efficiency of the organic EL element obtained in this example
was measured by the following method. That is, a voltage was applied to the obtained
organic EL element, and then the applied voltage V and a current I flowing through the
organic EL element were measured with a source measurement instrument (manufactured
by ADC CORPORATION, R6244), and a total luminous flux amount L was measured with
a total flux measurement apparatus manufactured by Spectra Co-op. From the thus
obtained measured value of the applied voltage V, the current I, and the total luminous flux
amount L, a luminance value L' was calculated. Here, for the current efficiency, the
following calculation formula (Fl) was used:
Current efficiency = (L'II) x S (Fl)
and, for the power efficiency, the following calculation formula (F2) was used:
Power efficiency = (L'IIIV) x S (F2)
Accordingly, the current efficiency and the power efficiency of the organic EL element
were calculated. In the above formulae, S is a light-emitting or luminescent area of the
element. Noted that the value of the luminance L' was calculated on the assumption that
light distribution characteristic of the organic EL element followed Lambert's law, and the
following calculation formula (F3) was used:
L' = L/x/S (F3
100961 The current efficiency of the organic EL element of this example at a luminance of
1000 cd/m2 was about 1.4 times that of the organic EL element having no concavities and
convexities on the glass substrate. Further, the power efficiency of the organic EL
element of this example at a luminance of 1000 cd/m2 was about 1.6 times that of the
organic El, element having no concavities and convexities on the glass substrate.
Therefore, the organic EL element of the present invention had a sufficient external
extraction efficiency.
[0097]
The directivity of light emission of the organic EL element obtained in this
39
example was evaluated by the following method. That is, the organic EL element in a
luminescent state was visually observed in all the directions (directions of all around 360").
Neither particularly bright sites nor particularly dark sites were observed when the organic
EL, element obtained in Example 3 was observed in any of the directions of all around 360°,
and the brightness was uniform in all the directions. In this way, it was shown that the
directivity of light emission of the organic EL element of the present invention was
sufficiently low.
[0098]
[Example 41
Example 4 was performed in the same manner as Example 1, except that a roll,
which was provided with a heater therein and had the outer periphery covered with
heat-resistant silicone of a thickness of 4 mm (roll diameter (cp): 50 mm, length in an axial
direction of the shaft: 350 mm), was used as the pressing roll and that the pressing roll was
heated to a temperature of 80 degrees Celsius. That is, the sol was prepared and applied
on the soda-lime glass plate by the bar coating. The mold having the line-and-space
pattern was pressed against the coating film on the glass plate by use of the heated pressing
roll for each elapsed time after the application of the sol. Then, the mold was peeled off
from the coating film.
[0099] After peeling off the mold, the transfer state of the line-and-space pattern on the
coating film was observed visually. When the line-and-space pattern on the coating film
could be observed, it was evaluated as transferable. The evaluation results are shown in
Table 3. Table 3 shows the time elapsed after the application and before the pressing; the
weight of the coating film; the ratio of weight of the coating film to the dried weight; and
the evaluation results. In a case that the line-and-space pattern was clearly transferred on
the coating film, it is expressed as "+" and in a case that no line-and-space pattern was
observed and evaluated as transfer failure, it is expressed as "-" in each column of Table 3.
[Ol 001 (TABLE 3>
[0101] The results in Table 3 show that the transfer was satisfactory in a case that the
ratio of weight of the coating film to the dried weight was in a range of 1.4 to 4.5. That is,
in terms of the time elapsed after the application, the transfer was satisfactory in a case that
the elapsed time was in a range of 70 seconds to 240 seconds. Note that in a case that the
weight exceeded 4.0, the sol applied by the bar coater flowed and leaked from the substrate,
so that the sol came around behind the substrate. This made an area around the substrate
dirty.
[0102] Of the glass substrates each having the coating film to which the line-and-space
Evaluation
-
-
-
-
+
+
+
+
Time elapsed after
application
(second)
10
20
3 0
40
50
60
70
80
90
100
300
310
Drying at 100 deg C
for 5 minutes
Weight of
coating film (mg)
75.3
66.1
57.5
50.3
43.8
38.6
33.7
29.6
26.0
'he weight of the film dried at 100 degrees Celsius for 5 minutes was defined as 1
1 1.2
1 1.2
8.60
Weight ratio to dried film
(*I)
8.76
7.69
6.69
5.85
5.09
4.49
3.92
3.44
3.02
1.30
1.30
1 .OO
-
-
pattern was transferred, the substrate(s) to which the line-and-space pattern was clearly
transferred was(were) subjected to a main baking by heating the substrate(s) for 60 minutes
in an oven of 300 degrees Celsius.
[0 1031
[Example 51
Example 5 was performed in the same manner as Example 4, except that the sol
was applied by the spin coating method instead of the bat coating method. The spin
coating was performed at a spin speed of 500 rpm for 8 seconds, and then performed at a
spin speed of 1000 rpm for 3 seconds. The weight of the glass substrate was weighed for
each elapsed time after the spin coating in the same manner as Example 4. Then, it was
obtained the ratio of weight of the glass substrate to the weight (dried weight) of the
substrate, which was obtained by heating the substrate at a temperature of 100 degrees
Celsius for 5 minutes. Fig. 16 shows the variation of the ratio (e= b(t)/a) of weight of the
coating film to the dried weight of the coating film for each elapsed time after the spin
coating. Subsequently, the mold was pressed against the coating film of the sol which
was obtained by performing the spin coating on the glass substrate, by use of the pressing
roll which was provided with the heater therein and of which temperature was 80 degrees
Celsius, while the pressing roll was moved and rotated, for each elapsed time in the same
manner as Example 4. After the completion of pressing against the coating film, the mold
was manually peeled off from the substrate in the same manner as Example 4. Then, the
pattern transferred to the coating film was observed and evaluated.
[0104] Table 4 shows the evaluation results. The following is understood from the
results. That is, even when the sol is applied by using the spin coater, the transfer can be
performed satisfactorily provided that the ratio "e" of weight of the coating film to the
dried weight of the coating film is not less than 1.4.
* 1 The weight of the film dried at 100 degrees Celsius for 5 minutes was defined as 1.
qable 4 (Continued)>
110
120
Drying at 100 deg
C for 5 minutes
* i The weight of the film dried at 100 degrees Celsius for 5 minutes was defined as 1.
1.32
1.31
1.00
14.6
14.5
11.1
[0 1061
[Example 61
Example 6 was performed in the same manner as Example 5, excepted that 3 1.7 g
of isopropyl alcohol (IPA) was used instead of ethanol used in the sol. That is, the sol
was prepared and applied on the glass substrate by the spin coating, and the mold having
-
-
- 110
120
Drying at 100 deg
C for 5 minutes
12.9
12.9
9.40
1.37
I .37
1 .OO
the line-and-space pattern was pressed against the coating film on the glass substrate using
the heated pressing roll every time when a predetermined period of time elapses. The
variation of the ratio (e= b(t)/a) of weight of the coating film to the dried weight of the
coating film for each elapsed time after the application was the same as that shown in the
graph of Fig. 15. The evaluation results are shown in Table 4. The following is
understood from the results. That is, even when the isopropyl alcohol is used as the
solvent of the sol, the transfer can be performed satisfactorily provided that the ratio of
weight of the coating film to the dried weight of the coating film is not less than 1.4.
[0107]
[Example 71
The diffraction grating mold made of the PET substrate with the resin film to
which the surface profile of the nickel mold was transferred was obtained in the same
manner as Example 3. After the elapse of 60 seconds from the application of sol on the
glass substrate by performing the bar coating on the glass substrate, the diffraction grating
mold was pressed against the coating film of the sol, by use of the pressing roll which was
heated to 80 degrees Celsius, while the pressing roll was moved and rotated, in the same
manner as Example 4. After the completion of pressing against the coating film, the mold
was manually peeled off from the substrate in the same manner as Example 4. Then, the
substrate was subjected to the main baking by heating the substrate for 60 minutes in an
oven of 300 degrees Celsius, and the pattern of the diffraction grating transferred to the
coating film was evaluated. An analysis image of the shape of the concavities and
convexities on the surface ofthe coating film in the diffraction grating was obtained by
using the atomic force microscope (the scanning probe microscope equipped with the
environment control unit "Nanonavi I1 Station/E-sweep" manufactured by SII
Nano'I'echnology Inc.) in the same manner as Example 3. Analysis conditions of the
atomic force microscope were the same as those in Example 3.
[0 1081
A concavity and convexity analysis image was obtained in the same manner as
Example 3 by performing a measurement in a randomly selected measuring region of 3 pm
square (length: 3 pm, width: 3 pm) in the diffraction grating. The average height ofthe
concavity and convexity pattern obtained by the analysis image in this example was 56 nin.
[0109]
A concavity and convexity analysis image was obtained in the same manner as
Example 3 by performing a measurement in a randomly selected measuring region of 3 pm
square (length: 3 pm, width: 3 pm) in the diffraction grating. The obtained concavity and
convexity analysis image was subjected to the process which was the same as that in
Example 3 to obtain a Fourier-transformed image. 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 pn", and that the circular pattern was
present within a region where the absolute value of wavenumber was in a range of 10 pm-I
or less. As a result of the image analysis of the obtained Fourier-transformed image, the
wavenumber 2.38 pm'l was the most intensive. That is, the average pitch was 420 nm.
[O 11 O]
The organic EL element in which the concavity and convexity structure was
maintained as shown in Fig. 13 was manufactured by the same process as Example 3 by
use of the glass substrate with the pattern made of the sol-gel material layer as the
diffraction grating obtained as described above.
[Olll]
'The light emission efficiency of the organic EL element obtained in this example
was measured in the same manner as Example 3. It was found that the current efficiency
of the organic EL element of this example at a luminance of 1000 cd/m2 was about 1.7
times that of the organic EL element having no concavities and convexities on the glass
substrate. Further, it was found that the power efficiency of the organic EL element of
this example at a luminance of 1000 cd/m2 was about 2.1 times that of the organic EL
element having no concavities and convexities on the glass substrate. Therefore, the
organic EL, element of the present invention had an external extraction efficiency
sufficiently.
[0112]
The directivity of light emission of the organic EL element obtained in this
example was evaluated by the same method as Example 3. Neither particularly bright
sites nor particularly dark sites were observed when the organic EL element obtained in
4 5
this example was observed in any of the directions of all around 360°, and the brightness
was uniform in all the directions. In this way, it was shown that the directivity of light
emission of the organic EL element of the present invention was sufficiently low.
[0113] As described above, the temperature at the time of forming the film of the
transparent electrode (ITO) of the organic EL element in each of Examples 3 and 7 was
300 degrees Celsius. Although it is allowable that the temperature at the time of forming
the film of the transparent electrode is lower than 300 degrees Celsius, the transparent
electrode is desired to have a low resistivity, and the film formation is preferably
performed at a high temperature to increase crystallinity. In a case that the temperature
during the film formation is low, which is about 100 degrees Celsius, the IT0 film formed
on the substrate is relatively amorphous and has an inferior specific resistance, and an
adhesion property between the substrate and the IT0 thin film is inferior. Although the
concavity and convexity pattern formed of a general UV curable resin and the like had
difficulty in withstanding a film formation step at a high temperature, the concavity and
convexity pattern can be applied even in the film formation step at a high temperature by
using the sol-gel material which is an example of ceramic. Therefore, the method of the
present invention is also suitable for producing the substrate (diffraction grating) for the
organic EL element. Further, in a case that the curable resin as described above is kept
for a long period under a high temperature because of, for example, the generation of heat
at the time of emitting light, there is fear that the curable resin deteriorates to cause yellow
discoloration andor generate gas. Thus, it is difficult to use the organic EL element using
the resin substrate for a long period of time. In contrast, the organic EL element provided
with the substrate made of the sol-gel material is less likely to deteriorate.
[0114]
[Example 81
Example 8 was performed in the same manner as Example 7, except that the
pressing roll, which was heated to 40 degrees Celsius, was used. As a result, the pattern
could be transferred similarly to Example 7, and it was confirmed that the average height
of the concavity and convexity pattern was 56 nm and the average pitch was 420 nm. The
organic EL element was manufactured and the light emission efficiency of the organic EL
element was measured in the same manner as Example 7. It was found that the current
efficiency of the organic EL element of this example at a luminance of 1000 cd/m2 was
about 1.7 times that of the organic EL element having no concavities and convexities on
46
the glass substrate. Further, it was found that the power efficiency of the organic EL
element of this example at a luminance of 1000 cd/m2 was about 2.1 times that of the
organic EL element having no concavities and convexities on the glass substrate.
Therefore, the organic EL element of the present invention had an external extraction
efficiency sufficiently.
[0115]
[Example 91
Example 9 was performed in the same manner as Example 7, except that the
pressing roll, which was heated to 150 degrees Celsius, was used. As a result, the pattern
could be transferred similarly to Example 7, and it was confirmed that the average height
of the concavity and convexity pattern was 56 nm and the average pitch was 420 nm.
[0116] The organic EL element was manufactured and the light emission efficiency of the
organic EL element was measured in the same manner as Example 7. It was found that
the current efficiency of the organic EL element of this example at a luminance of 1000
cd/m2 was about 1.7 times that of the organic EL element having no concavities and
convexities on the glass substrate. Further, it was found that the power efficiency of the
organic EL element of this example at a luminance of 1000 cd/m2 was about 2.1 times that
of the organic EL element having no concavities and convexities on the glass substrate.
Therefore, the organic EL element of the present invention had an external extraction
efficiency sufficiently.
[0117]
[Example 101
The diffraction grating was manufactured in the same manner as Example 7,
except that the pressing roll, which was heated to 25 degrees Celsius, was used. As a
result, the pattern could be transferred similarly to Example 7, and the average height of
the concavity and convexity pattern was 56 nm and the average pitch was 420 nm.
However, the peeling of the mold from the coating film took a longer time than that of
Example 7.
[Ollg]
[Comparative Example 11
Comparative Example 1 was performed in the same manner as Example 3, except
that the time elapsed after the application and before the pressing was set to 250 seconds.
As a result, no pattern was transferred.
[0119] The organic EL element was manufactured and the light emission efficiency of the
organic EL element was measured in the same manner as Example 3. It was found that
the current efficiency of the organic EL element of this comparative example at a
luminance of 1000 cd/m2 was about 1.0 times that of the organic EL element having no
concavities and convexities on the glass substrate. Further, it was found that the power
efficiency of the organic EL element of this comparative example at a luminance of 1000
cd/m2 was about 1.0 times that of the organic EL element having no concavities and
convexities on the glass substrate.
[0120]
[Comparative Example 21
Comparative Example 2 was performed in the same manner as Example 7, except
that the time elapsed after the application and before the pressing was set to 250 seconds.
As a result, no pattern was transferred. The organic EL element was manufactured and
the light emission efficiency of the organic EL element was measured in the same manner
as Example 7. It was found that the current efficiency of the organic EL element of this
comparative example at a luminance of 1000 cd/m2 was about 1.0 times that of the organic
EL element having no concavities and convexities on the glass substrate. Further, it was
found that the power efficiency of the organic EL element of this comparative example at a
luminance of 1000 cd/m2 was about 1.0 times that of the organic EL element having no
concavities and convexities on the glass substrate.
[0121] In the above description, the present invention was explained by using Examples.
The method of the present invention, however, is not limited to the methods described in
Examples. and can be appropriately modified within technical idea described in the claims.
For example, the pattern was transferred by using the mold and the pressing roll, each of
which had a specific material, a specific size, and a specific structure in the above
Examples. 'The present invention, however, is not limited thereto, and it is possible to use
a mold and a pressing roll, each of which adopts any material, any size, and any structure.
Further, the film of the organic layer was formed by the vapor deposition method when the
organic EL element was manufactured in the above description. However, either the
vapor deposition method or any known application method such as a spin coating can be
employed as a method for stacking the organic layer. Furthermore, the sol (sol-gel
solution) having a specific composition was used when the film of the sol-gel material was
formed in the above description. However, the sol can be prepared to have any
4 8
composition, and any additive can be added without departing from the scope of the
present invention.
Industrial Applicability
[0122] According to the present invention, it is possible to reliably produce a substrate
having a relatively large area, in which a concavity and convexity pattern is formed, with
high production efficiency. Therefore, the present invention is suitable for producing
various types of optical elements including a diffraction-grating substrate for an organic EL
element, a wire grid polarizer, an antireflection film, an optical element for a solar cell, etc.,
in particular, a large-size optical element. Further, the concavity and convexity pattern in
the substrate was made of silica by a sol-gel process and thus the concavity and convexity
pattern has the resistance to a relatively high temperature. Therefore, it is possible to
produce an organic EL element having high performance at a high yield.
Reference Signs List:
[0123]
20: transport system, 21: feeding roll, 22: pressing roll, 22a: heater, 23: peeling roll, 24:
winding roll, 25: support roll, 30: die coater, 32: heater, 40: substrate, 42: coating film
(sol-gel material layer), 50: mold, 70: mold manufacturing apparatus, 72: film feeding roll,
74: nip roll, 76: peeling roll, 78: film winding roll, 80: substrate film, 82: die coater, 85:
radiation light source, 87: mold, 90: metal roll, 92: transparent electrode, 94: organic layer,
95: hole transporting layer, 96: light-emitting layer, 97: electron transporting layer, 98:
metal electrode, 100a to 100h: manufacturing apparatuses, 200: organic EL element
We claim:
1. A method for producing a substrate having a concavity and convexity
pattern, comprising:
a step of applying a sol, which contains a silica precursor, on a substrate to form a
coating film;
a step of drying the coating film;
a step of pressing a mold having a concavity and convexity pattern against the
dried coating film with a pressing roll so that the concavity and convexity pattern is
pressed onto the coating film;
a step of peeling off the mold from the coating film; and
a step of baking the coating film to which the concavity and convexity pattern has
been transferred,
wherein the coating film is dried in the drying step so that a ratio of weight of the
coating film to dried weight of the coating film is in a range of 1.4 to 8.8, the dried weight
being obtained by baking the coating film at a temperature of 100 degrees Celsius.
2. The method for producing the substrate having the concavity and
convexity pattern according to claim 1, wherein, in the step of pressing the concavity and
convexity pattern against the coating film, the mold having the concavity and convexity
pattern is pressed against the dried coating film with the pressing roll while the dried
coating film is heated.
3. The method for producing the substrate having the concavity and
convexity pattern according to claim 2, wherein the coating film is dried in the drying step
so that the ratio of the weight of the coating film to the dried weight of the coating film is
in a range of 1.4 to 4.5, the dried weight being obtained by baking the coating film at the
temperature of 100 degrees Celsius.
4. The method for producing the substrate having the concavity and
convexity pattern according to any one of claims 1 to 3, wherein the pressing roll includes
a heater.
5. The method for producing the substrate having the concavity and
convexity pattern according to claim 4, wherein the pressing roll is heated to temperatures
of 40 degrees Celsius to 150 degrees Celsius by the heater.
6. The method for producing the substrate having the concavity and
convexity pattern according to any one of claims 1 to 5, wherein the sol contains one kind
of metal alkoxide or a several kinds of metal alkoxides.
7. The method for producing the substrate having the concavity and
convexity pattern according to claim 6, wherein the sol contains a mixture of
tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES).
8. The method for producing the substrate having the concavity and
convexity pattern according to any one of claims 1 to 7, further comprising a step for
pre-baking the coating film after the concavity and convexity pattern is pressed against the
coating film and before the mold is peeled off from the coating film.
9. The method for producing the substrate having the concavity and
convexity pattern according to any one of claims 1 to 8, wherein a peeling roll is used to
peel off the mold from the coating film.
10. The method for producing the substrate having the concavity and
convexity pattern according to claim 9, wherein the mold is peeled off from the coating
film while the peeling roll is heated.
11. The method for producing the substrate having the concavity and
convexity pattern according to any one of claims 1 to 10, wherein an average pitch of
concavities and convexities on the concavity and convexity pattern is in a range of 100 nm
to 900 nin and an average height of the concavities and convexities is in a range of 20 nm
to 200 nm.
12. The method for producing the substrate having the concavity and
convexity pattern according to any one of claims 1 to 11, wherein the mold having the
5 1
concavity and convexity pattern is a flexible mold.
13. The method for producing the substrate having the concavity and
convexity pattern according to claim 12, wherein the flexible mold is a long mold having a
length longer than that of the substrate, and the long mold is pressed against the coating
film with the pressing roll while the long mold is transported by using a feeding roll which
feeds the long mold and a winding roll which rolls up the long mold thereon.
14. A sol used for the method for producing the substrate having the
concavity and convexity pattern as defined in any one of claims 1 to 13.
15. A method for producing an organic EL element, wherein a
diffraction-grating substrate having a concavity and convexity surface is manufactured by
the method for producing the substrate having the concavity and convexity pattern as
defined in any one of claims 1 to 13; and
a transparent electrode, an organic layer, and a metal electrode are stacked in this
order on the concavity and convexity surface of the diffraction-grating substrate, thereby
producing the organic EL element.
16. An organic EL element which is obtained by the method as defined in
claim 15 to include a transparent electrode, an organic layer, and a metal electrode on a
diffraction-grating substrate having a concavity and convexity surface, wherein the
diffraction-grating substrate has a substrate having no concavity and convexity pattern and
a silica layer having a concavity and convexity pattern formed directly on the substrate
having no concavity and convexity pattern.
17. The organic EL element according to claim 16, wherein the substrate is a
substrate made of an inorganic material.