ORGANIC EL ELEMENT AND METHOD FOR MANUFACTURING SAME
Technical Field
[0001] The present invention relates to an organic EL element (Organic
Electro-Luminescence element or organic light emitting diode) which has a high light
extraction efficiency and is capable of preventing the occurrence of a leak current
effectively, and a method for manufacturing the same.
Background Art
[0002] There has been known a nanoimprint method, in addition to a lithography method,
as a method for forming a minute or fine pattern such as a semiconductor integrated circuit.
The nanoimprint method is a technique such that a pattern of an order of nanometer can be
transferred by sandwiching a resin between a mold and a substrate. A thermal
nanoimprint method, a photonanoimprint method, and the like have been studied
depending on the employed material. Of the above methods, the photonanoimprint
method includes four steps of: i) resin coating (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 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 an organic
EL element and LED, MEMS, and a biochip, in addition to a semiconductor device.
[0003] In the organic EL element (organic light emitting diode), a hole injected from an
anode through a hole injecting layer and electron injected from a cathode through an
electron injecting layer are carried to a light emitting layer respectively, then the hole and
electron are recombined on an organic molecule in the light emitting layer to excite the
organic molecule, and thus light emission occurs. Therefore, in a case that the organic EL
element is used as a display device and/or an illumination device, the light from the light
emitting layer is required to be efficiently extracted from the surface of the organic EL
va
element. In order to meet this demand, PATENT LITERATURE 1 discloses that a
diffraction-grating substrate having a concave-convex structure is provided on a light
extraction surface of the organic EL element.
Citation List
Patent Literature
[0004] PATENT LITERATURE 1: Japanese Patent Application Laid-open No.
2006-236748
PATENT LITERATURE 2: Japanese Patent Application Laid-open No.
2011-44296
PATENT LITERATURE 3: Japanese Patent Application Laid-open No.
2011-48937
[0005] The light emitted from the light-emitting layer goes outside through an electrode,
and thus a thin film made of indium tin oxide (ITO) having a light-transmissive property is
generally used in one of a pair of electrodes. The light emitted from the light-emitting
layer goes outside through the ITO thin film and a substrate with the ITO thin film formed
thereon. The refractive index of the transparent electrode is generally higher than the
refractive index of the substrate. For example, the refractive index of the glass substrate
is about 1.5 and the refractive index of the ITO thin film is about 2.0. Such a relation
between the refractive index of the transparent electrode and the refractive index of the
substrate is more likely to cause the total reflection of the light emitted from the
light-emitting layer at an interface between the transparent electrode and the substrate.
As a result, the light emitted from the light-emitting layer is trapped in an element, which
causes a problem such that the efficiency of the extraction of the light from the substrate
deteriorates.
[0006] PATENT LITERATURE 2 discloses a method for manufacturing a substrate with
electrodes for an organic Electro-Luminescence element, wherein the substrate with
electrodes is configured such that a low refractive index layer, a functional layer, and an
electrode having a light transmissive property are stacked in this order, and wherein the
refractive index nl of the electrode, the refractive index n2 of the functional layer, and the
refractive index n3 of the low refractive index layer satisfy 0 < (nl-n2) < 0.3 and n3 < n2 <
nl. In this manufacturing method, the difference between the refractive index of the
functional layer and the refractive index of the electrode is small, and thus the total
^3
reflection at an interface between the functional layer and the electrode is inhibited and the
light emitted from a light emitting layer and coming into the electrode is efficiently
transmitted to the functional layer. Further, by forming the interface between the
functional layer and the low refractive index layer to have a concave-convex shape, the
concavities and convexities function as a microlens, which inhibits the total reflection at
the interface between the functional layer and the low refractive index layer. Accordingly,
the light coming into the functional layer from the electrode is transmitted to the low
refractive index layer efficiently. Further, the substrate has a layer structure such that a
layer closer to the outside (air) has a smaller refractive index, and thus it is possible to
reduce the difference between the refractive index of air and the refractive index of a layer
contacting with air (low refractive index layer). PATENT LITERATURE 2 further
discloses that a surface of the functional layer on the electrode side is formed to be flat.
[0007] In order to improve the light extraction efficiency and the visibility of an organic
EL light-emitting element, PATENT LITERATURE 3 discloses an organic EL
-light-emitting element 1 as follows. That is, as depicted in Fig. 11 of PATENT
LITERATURE 3, a first electrode 3, an organic layer 4, and a second electrode 5 are
stacked on a substrate 2 in this order. A minute concave-convex structure 6 of which
arrangement or array pitches are not more than incoming wavelengths is provided between
the substrate 2 and the first electrode 3 on the side of the substrate 2, and a transparent
layer 7 is provided on the side of the first electrode 3. The refractive index nl of the
substance constituting the substrate 2 is not less than the refractive index n2 of the
substance constituting the minute concave-convex structure (nl > n2), and thus the
difference between the refractive index of the substrate 2 and the refractive index of the
first electrode 3 is inclined. Then, the reflection at the interface due to the difference
between the refractive indexes is reduced, and thereby making it possible to improve the
light extraction efficiency in PATENT LITERATURE 3. Especially, by filling the
concavities and convexities of the minute concave-convex structure 6 to make the
transparent layer 7 flat, a thin film of the first electrode 3 formed on the transparent layer 7
does not have uneven film thickness, which removes the possibility of occurrence of a
short circuit in PATENT LITERATURE 3.
Summary of Invention
Technical Problem
[0008] In the structure of the organic EL light-emitting element described in each of
PATENT LITERATURE 2 and PATENT LITERATURE 3, the light extraction efficiency is
improved by providing the layer of the minute concave-convex structure on the substrate
and providing the layer for adjusting the refractive index which has a planarized or
flattened surface between the first electrode and the layer of the minute concave-convex
structure. However, the investigation and study of the applicant of the present application
showed that the technique described in the above patent literatures did not yet have
sufficient light extraction efficiency. Further, in a case that the diffraction-grating
substrate having the concave-convex structure is provided on the light extraction surface of
the organic EL element, the occurrence of a leak current due to the concave-convex
structure is required to be inhibited. Therefore, an organic EL light-emitting element,
which has a sufficient light extraction efficiency while inhibiting the occurrence of the leak
current, is expected to be developed in order that the organic EL light-emitting element is
put into practical use in many fields such as a display and lighting.
[0009] In view of the above, an object of the present invention is to provide an organic
EL light-emitting element which has a high light extraction efficiency while inhibiting the
occurrence of a leak current.
Solution to the Problem
[0010] According to a first aspect of the present invention, there is provided an organic
EL element, including: a concave-convex pattern layer having a first concave-convex
shape, a first electrode, an organic layer, and a second electrode layer formed on a substrate
in this order; and an auxiliary layer provided between the concave-convex pattern layer
and the first electrode, wherein a surface of the auxiliary layer on a side of the first
electrode has a second concave-convex shape; and a change ratio of a standard deviation of
depths of the second concave-convex shape with respect to a standard deviation of depths
of the first concave-convex shape is 70% or less.
[0011] In the organic EL element of the present invention, the concave-convex shape on
the surface of the auxiliary layer is controlled so that the change ratio of the standard
deviation of the depths of the second concave-convex shape with respect to the standard
deviation of the depths of the first concave-convex shape is 70% or less. Thus, it is
possible to improve the light extraction efficiency while preventing the occurrence of a
leak current.
* ^
[0012] In the organic EL element of the present invention, the change ratio of the
standard deviation of the depths of the second concave-convex shape with respect to the
standard deviation of the depths of the first concave-convex shape may be in a range of
20% to 70%.
[0013] In the organic EL element of the present invention, the total of optical film
thicknesses of the auxiliary layer and the first electrode may be in a range of 160 nm to 400
nm. The first electrode may be made of ITO and may have a film thickness of 80 nm or
more. The auxiliary layer may be made of TiC>2. Both the concave-convex pattern layer
and the auxiliary layer may be made of an inorganic material such as sol-gel material.
The concave-convex pattern layer may be made of silica.
[0014] In the organic EL element of the present invention, in a case that refractive
indexes of the substrate, the concave-convex pattern layer, the auxiliary layer, and the first
electrode are represented by nO, nl, n2, and n3, respectively, the following relation:
n2 > n3 > nl < 0 may be satisfied.
[0015] In the organic EL element of the present invention, the concave-convex pattern
layer may include an irregular concave-convex pattern in which orientations of concavities
and convexities have no directivity. The average pitch of concavities and convexities of
the concave-convex pattern layer may be in a range of 100 nm to 1200 nm, the average
height of the concavities and convexities may be in a range of 20 nm to 200 nm, and the
standard deviation of depths of the concave-convex shape may be in a range of 10 nm to
100 nm.
[0016] According to a second aspect of the present invention, there is provided a method
for manufacturing the organic EL element, including: forming the concave-convex pattern
layer, the auxiliary layer, the first electrode, the organic layer, and the second electrode
layer on a substrate in this order; and forming the auxiliary layer to make a surface of the
auxiliary layer on a side of the first electrode have a second concave-convex shape,
wherein a change ratio of a standard deviation of depths of the second concave-convex
shape with respect to a standard deviation of depths of the first concave-convex shape is
70% or less. The concave-convex pattern layer may be formed by coating the substrate
with a sol-gel material, pressing a film-shaped mold against the substrate, and then heating
the substrate.
Advantageous Effects of Invention
^ 6
[0017] In the organic EL element of the present invention, the auxiliary layer is provided
between the concave-convex pattern layer on the substrate and the first electrode. The
second concave-convex shape of the auxiliary layer on the first electrode side is controlled
so that the change ratio of the standard deviation of depths of the second concave-convex
shape with respect to the standard deviation of depths of the first concave-convex shape is
70% or less. Thus, it is possible to prevent the occurrence of a leak current effectively
while maintaining a superior light extraction efficiency.
Brief Description of Drawings
[0018]
Fig. 1 is a schematic cross-sectional view depicting a cross-section structure of an
organic EL element of the present invention.
Fig. 2 is a schematic cross-sectional view depicting a cross-section structure of an
organic EL element of another aspect of the present invention.
Fig. 3 is a flowchart showing a process for forming a concave-convex pattern
layer of the organic EL element of the present invention.
Fig. 4 is a conceptual view depicting a transfer step in Fig. 3.
Fig. 5 is a graph showing the standard deviation of the shape (depths) of
concavities and convexities formed on a surface of a TiC>2 film on a transparent electrode
side with respect to the thickness of the Ti02 film in the organic EL element of the present
invention.
Fig. 6 is a graph showing the shape change ratio with respect to the thickness of
an auxiliary layer (TiCh film) in the organic EL element of the present invention.
Fig. 7 is a schematic cross-sectional view depicting a cross-section structure of an
organic EL element of Comparative Example 1.
Fig. 8 is a schematic cross-sectional view depicting a cross-section structure of an
organic EL element of Comparative Example 2.
Fig. 9 is a schematic cross-sectional view depicting a cross-section structure of an
organic EL element of Comparative Example 3.
Fig. 10 is a schematic cross-sectional view depicting a cross-section structure of
an organic EL element of Comparative Example 4.
Fig. 11 is a schematic cross-sectional view depicting a cross-section structure of
an organic EL element disclosed in PATENT LITERATURE 3.
Fig. 12 is a table showing the film thickness of the TiCh film, the film thickness of
the transparent electrode (ITO), the total film thickness thereof, the optical film thickness
of the total film thickness, the shape change ratio, current efficiency, and the like, of the
organic EL element obtained in each of Examples and Comparative Examples (indicated as
"EX." and "COM. EX." in Fig. 12).
Description of Embodiments
[0019] An embodiment of an organic EL element of the present invention will be
explained with reference to the drawings. As depicted in Fig. 1, in the organic EL
element of the present invention, a concave-convex pattern layer 12, an auxiliary layer 14,
a first electrode layer 16, an organic layer 18, and a second electrode layer 20 are stacked
on a substrate 10 in this order.
[0020]
[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 terenaphthalate (PEN), polycarbonate (PC), cycloolefin polymer (COP),
polymethyl methacrylate (PMMA), polystyrene (PS), polyimide (PI), and polyarylate may
be used. The substrate may be transparent or opaque. A relatively hard substrate is
preferred from the perspective that the organic layer 18 is formed on this substrate via the
concave-convex pattern layer 12, which is made of sol-gel material and the like, and the
first electrode layer 16. In terms of the uses or applications of the organic EL element,
the substrate desirably has the heat resistance and the weather resistance to UV light and
the like. In these respects, substrates made of inorganic materials such as glass, silica
glass, and silicon substrates are more preferable. Especially, in a case that the substrate is
made from the inorganic materials and that the concave-convex pattern layer is made from
the inorganic materials such as a sol-gel material layer, the difference between the
refractive index of the substrate and the refractive index of the sol-gel material layer is
small and unintended refraction and/or reflection in the optical substrate can be prevented.
Thus, the substrates made of the inorganic materials are preferred. It is allowable to
perform a surface treatment or provide an easy-adhesion layer on the substrate in order to
improve an adhesion property, and to provide a gas barrier layer in order to keep out
moisture and/or gas such as oxygen.
[0021]
[Concave-convex pattern layer]
The concave-convex pattern layer 12 formed on the substrate 10 is a layer having
a minute concave-convex pattern formed on the surface thereof. The minute
concave-convex pattern acts as follows. That is, the visible light generated from the
organic layer 18 (for example, the light having a wavelength band ranging from 380 nm to
780 nm), especially the light travelling in a direction which is inclined to the surface of the
substrate 10, is diffracted toward the substrate 10, so that the diffracted light is extracted
from the substrate 10. In order to allow the concave-convex pattern layer 12 to act as the
diffraction grating, the average pitch of the concavities and convexities of the
concave-convex pattern may be, for example, in a range of 100 nm to 1500 nm, more
preferably in a range of 200 nm to 1200 nm. In a case that the average pitch of the
concavities and convexities is less than the lower limit, the pitches are so small relative to
wavelengths of the visible light that the diffraction of light by the concavities and
convexities is likely to be insufficient. In a case that the average pitch exceeds the upper
limit, a diffraction angle is so small that functions as an optical element such as the
diffracting grating are more likely to be lost. The average height of the concavities and
convexities of the concave-convex pattern is preferably in a range of 20 nm to 200 nm, and
more preferably in a range of 30 nm to 150 nm.
[0022] The average height of the concavities and convexities is obtained as follows. For
example, a concavity and convexity analysis image is obtained by use of an atomic force
microscope; distances between randomly selected concave portions and convex portions in
the depth direction are measured at 100 points or more in the concavity and convexity
analysis image; and the average of the distances can be calculated as the average height
(depth) of the concavities and convexities. In the present application, "the standard
deviation of depths of the concavities and convexities" which will be described later is
used as an index expressing the heights of the concavities and convexities (i.e., the depths
of the concavities and convexities) of the concave-convex pattern or the variation of the
heights (depths) of the concavities and convexities of the concave-convex pattern. The
respective positions of the concave-convex pattern in the height direction vary in an
up-down direction with respect to the center position of the average height of the
concavities and convexities. Therefore, the standard deviation of depths of the
concavities and convexities can also be an index expressing the depths of the concavities
and convexities. The standard deviation of depths of the concavities and convexities can
be calculated by a concavity and convexity analysis image obtained by the atomic force
microscope and the average value of depth distribution of the concavities and convexities
obtained therefrom. The standard deviation of depths of the concavities and convexities
of the concave-convex pattern is preferably in a range of 10 nm to 100 nra, and more
preferably in a range of 15 nm to 75 nm.
[0023] It is preferred that the concave-convex pattern be an irregular concave-convex
pattern in which the pitches of concavities and convexities are ununiform and the
orientations of the concavities and convexities have no directivity. Then, the light
scattered and/or diffracted by such a concave-convex pattern layer has a range of
wavelength relatively broad other than single wavelength or wavelength having a narrow
band, has no directivity, and is directed in various directions. Note that the "irregular
concave-convex pattern" includes such a quasi-periodic structure wherein a
Fourier-transformed image, which is obtained by performing a two-dimensional fast
Fourier-transform processing on a concavity and convexity analysis image obtained by
analyzing a concave-convex shape on the surface, shows a circular or annular pattern, that
is, such a quasi-periodic structure wherein the pitches of the concavities and convexities
have a particular distribution although the concavities and convexities have no particular
orientation.
[0024] It is preferred that inorganic materials be used as the materials of the
concave-convex pattern layer 12. Especially, it is possible to use silica, materials based
on Ti, materials based on indium tin oxide (ITO), and sol-gel materials such as ZnO, Z1O2,
AI2O3. Of the above materials, the silica is preferably used. The thickness of the
concave-convex pattern layer 12 is preferably in a range of 100 nm to 500 nm. In a case
that the thickness of the concave-convex pattern layer is less than 100 nm, the transfer of
the concave-convex shape by use of imprinting method is difficult. In a case that the
thickness of the concave-convex pattern layer exceeds 500 nm, any structural defect such
as a crack is more likely to occur.
[0025] In a case that the concave-convex pattern layer 12 is made of the sol-gel material,
the concave-convex pattern layer 12 can be formed on the substrate by the method
illustrated in Fig. 3. This method mainly includes a solution preparation step SI for
preparing a sol (sol solution); a coating step S2 for coating a substrate with the prepared sol
(applying the prepared sol on a substrate); a drying step S3 for drying the coating film of
\0
the sol coating the substrate; a transfer step S4 for pressing a film-shaped mold against the
dried coating film; a releasing step (peeling step) S5 for releasing (peeling off) the mold
from the coating film; and a main baking step S6 in which the coating film is subjected to
main baking. Hereinbelow, an explanation will be made about each of the steps
sequentially.
[0026] At first, there is prepared the sol used for forming a coating film to which a
pattern is transferred using a sol-gel method (step SI of Fig. 3). 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. As the silica precursor, it is possible to use 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; and dialkoxide monomers such as dimethyl dimethoxysilane, dimethyl
diethoxysilane, dimethyl dipropoxysilane, dimethyl diisopropoxysilane,
dimethyl-di-n-butoxysilane, dimethyl-di-i-butoxysilane, dimethyl-di-sec-butoxysilane,
dimethyl-di-t-butoxysilane, diethyl dimethoxysilane, diethyl diethoxysilane, diethyl
dipropoxysilane, diethyl diisopropoxysilane, diethyl-di-n-butoxysilane,
diethyl-di-i-butoxysilane, diethyl-di-sec-butoxysilane, diethyl-di-t-butoxysilane, dipropyl
dimethoxysilane, dipropyl diethoxysilane, dipropyl dipropoxysilane, dipropyl
diisopropoxysilane, dipropyl-di-n-butoxysilane, dipropyl-di-i-butoxysilane,
dipropyl-di-sec-butoxysilane, dipropyl-di-t-butoxysilane, diisopropyl dimethoxysilane,
diisopropyl diethoxysilane, diisopropyl dipropoxysilane, diisopropyl diisopropoxysilane,
diisopropyl-di-n-butoxysi lane, diisopropyl-di-i-butoxysilane,
diisopropyl-di-sec-butoxysilane, diisopropyl-di-t-butoxysilane, diphenyl dimethoxysilane,
diphenyl diethoxysilane, diphenyl dipropoxysilane, diphenyl diisopropoxysilane,
diphenyl-di-n-butoxysilane, diphenyl-di-i-butoxysilane, diphenyl-di-sec-butoxysilane,
diphenyl-di-t-butoxysilane. Further, it is possible to use alkyl trialkoxysilane or dialkyl
\ l
dialkoxysilane which has alkyl group having C4 to CI8 carbon atoms. It is possible to
use metal alkoxide such as a polymer obtained by polymerizing the above monomers in
small amounts and a composite material characterized in that functional group and/or
polymer is/are introduced into a part of the above material. Further, a part of or the entire
of the alkyl group and/or the phenyl group may be substituted by fluorine. Furthermore,
the silica precursor is exemplified, for example, by metal acetylacetonate, metal
carboxylate, oxychloride, chloride, and mixtures thereof. The silica precursor, however,
is not limited to these. Examples of metal species include, in addition to Si, Ti, Sn, Al, Zn,
Zr, In, and mixtures thereof, but are not limited to these. It is also possible to use any
appropriate mixture of precursors of the oxides of the above metals. Further, these
surfaces may be subjected to a hydrophobic treatment. Any known method may be used
as the method for hydrophobic treatment, for example, in a case that the hydrophobic
treatment is performed on the surface made of silica, any of the following methods may be
used. That is, the hydrophobic treatment can be performed by using dimethyl
dichlorosilane, trimethyl alkoxysilane, or the like; the hydrophobic treatment can be
performed by silicone oil and a trimethyl silylation agent such as hexamethyldisilazane;
and a surface treatment of metal-oxide powder by use of supercritical carbon dioxide can
be used.
[0027] 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 solution 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.
[0028] Examples of solvents of the sol include alcohols such as methanol, ethanol,
isopropyl alcohol (IPA), and butanol; aliphatic hydrocarbons such as hexane, heptane,
octane, decane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene,
and mesitylene; ethers such as diethyl ether, tetrahydrofuran, and dioxane; ketones such as
acetone, methyl ethyl ketone, isophorone, and cyclohexanone; ether alcohols such as
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.
[0029] As an additive of the sol, it is possible to use polyethylene glycol, polyethylene
oxide, hydroxypropylcellulose, and polyvinyl alcohol for viscosity adjustment;
alkanolamine such as triethanolamine, p-diketone such as acetylacetone, p-ketoester,
formamid, dimetylformamide, and dioxane, and the like, as a solution stabilizer.
[0030] The substrate is coated with the sol prepared as described above (step S2 of Fig. 3).
From a viewpoint of mass-production, it is preferred that the substrate be coated with the
sol (the sol be applied on the substrate) at a predetermined position while a plurality of
substrates are continuously transported. As the coating method, it is possible to use any
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. The die
coating method, the bar coating method, and the spin coating method are preferable,
because the substrate having a relatively large area can be coated uniformly with the sol
and the coating can be quickly completed prior to gelation of the sol.
[0031] After the coating step, the substrate is dried by being held or kept in the
atmosphere or under reduced pressure so as to evaporate the solvent in the coating film
(hereinafter also referred to as "sol-gel material layer" as appropriate) (step S3 of Fig. 3).
In a case that the holding time of the substrate is short, the viscosity of the coating film is
too low to transfer the pattern 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 thus the transfer cannot be performed in the transfer step. In a case that the
optical substrate is mass-produced, the holding time can be controlled as a time for
transporting the substrate from the sol coating to the subsequent transfer step using the
film-shaped mold. A holding temperature of the substrate in the drying step 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
13
this range, the gelation reaction of the coating film proceeds rapidly before the transfer 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 transfer step, which
reduces the productivity and is not preferable. After the sol coating, the polymerization
reaction of the precursor proceeds as the evaporation of the solvent proceeds, and the
physical property such as the viscosity of the sol 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. For example, in a case
that the sol is the silica precursor solution, the hydrolysis and condensation polymerization
reaction of the silica precursor occur as the gelation reaction and alcohol is generated in the
sol through dealcoholization reaction. 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 step. Therefore, it is desirable that the holding time and holding
temperature be adjusted by taking the gelation reaction and the solvent used in the sol into
consideration. In the drying step, the solvent in the sol evaporates simply by holding the
substrate as it is. Thus, it is not indispensable to actively perform a drying operation such
as heating and blowing. Leaving the substrate with the coating film as it is for a
predetermined time or transporting said substrate in a predetermined time for subsequent
steps are enough for drying the substrate. That is, the drying step is not indispensable for
the substrate formation step.
[0032] After the time set as described above has elapsed, a mold having a minute
concave-convex pattern is pressed against the coating film to transfer the concave-convex
pattern of the mold to the coating film on the substrate (step S4 of Fig. 3). It is desired
that a flexible film-shaped mold be used as the mold. For example, as depicted in Fig. 4,
it is possible to transfer the concave-convex pattern of a film-shaped mold 50 to a coating
film (sol) 42 on the substrate 10 by sending the film-shaped mold 50 between a pressing
roll 122 and the substrate 10 being transported immediately below the pressing roll 122.
That is, in a case that the film-shaped mold 50 is pressed against the coating film 42 with
the pressing roll 122, the surface of the coating film 42 on the substrate 10 is coated
(covered) with the film-shaped mold 50 while the film-shaped mold 50 and the substrate
10 are synchronously transported. In this situation, by rotating the pressing roll 122 while
pressing the pressing roll 122 against the back surface (surface on the side opposite to the
14
surface in which the concave-convex pattern is formed) of the film-shaped mold 50, the
film-shaped mold 50 moves with the substrate 10 to adhere to the substrate 10. In order
to send the long film-shaped mold 50 to the pressing roll 122, it is advantageous that the
film-shaped mold 50 is fed directly from a film roll around which the long film-shaped
mold 50 is wound.
[0033] The film-shaped mold used for manufacturing an optical member of the present
invention is a film-shaped or sheet-shaped mold having a concave-convex transfer pattern
on a surface thereof. The mold is made, for example, of organic materials such as
silicone resin, polyethylene terephthalate (PET), polyethylene naphthalate (PEN),
polycarbonate (PC), cycloolefin polymer (COP), polymethyl methacrylate (PMMA),
polystyrene (PS), polyimide (PI), and polyarylate. The concave-convex pattern may be
formed directly in (on) each of the materials, or may be formed in (on) a concave-convex
forming material with which a base material (substrate sheet) formed of the
above-mentioned materials is coated. It is possible to use photo-curable resin,
thermosetting resin, and thermoplastic resin as the concave-convex forming material.
[0034] The size of the film-shape mold, in particular, the length thereof can be set
appropriately based on the size of the optical substrate to be mass-produced, the number of
optical substrates (the number of lots) continuously produced in a single manufacturing
process. For example, the film-shaped mold may be a long mold having 10 meter or
more in length, and the pattern transfer may be performed continuously on a plurality of
substrates while the film-shaped mold wound around a roll is continuously fed from the
roll. The film-shaped mold may be 50 mm to 3000 mm in width, and 1 um to 500 um in
thickness. A surface treatment or an easy-adhesion treatment may be performed to
improve an adhesion property between the substrate and the coating film. Further, a
mold-release treatment may be performed on each surface of the concave-convex pattern
as needed. The concave-convex pattern may be formed to have any profile by arbitrary
method.
[0035] The film-shaped mold has the following advantages when compared to a mold in
a roll shape made of metal and the like. That is, regarding a hard mold made of metal,
silica, and the like, in a case that any defect has been found in a concave-convex pattern of
the hard mold, it is possible to clean and/or repair the defect. Thus, any failure can be
avoided which would be otherwise caused by the transfer of the defect to a so-gel material
layer. However, in the film-shaped mold, the cleaning and the repair as described above
\0
are less likely to be performed easily. In the meanwhile, the mold made of metal, silica,
and the like is in a roll shape, and when any defect such as clogging occurs in the mold, a
transfer device is required to be immediately stopped to exchange the mold. On the other
hand, since the transfer using the film-shaped mold is performed while each of the parts of
the film-shaped mold is made to correspond to each single glass substrate, a part having the
defect such as the clogging is marked at an inspection stage, and the transport of the glass
substrate can be suspended until the defect part passes through the glass substrate.
Therefore, on the whole, the use of the film-shaped mold can reduce the occurrence of
defective product and thereby making it possible to improve the throughput. In a case
that the concave-convex pattern of the hard mold made of metal, silica, and the like is tried
to be directly transferred to the sol-gel material layer, various limitations as described
below arise and thus a desired performance cannot be given sufficiently in some cases.
For example, in a case that a hard substrate such as glass is used as the substrate on which
the sol-gel material layer is formed, the adjustment of the pressure applied to the mold is
difficult. For example, if the pressure applied to the mold is high, the substrate is
damaged, for example, to have a crack since both of the substrate and the mold are hard; or
if the pressure applied to the mold is low, the concave-convex pattern is transferred
insufficiently. Therefore, a soft material must be used for the substrate or the mold.
Even when the film-shaped mold (soft mold) is used, a material to which the
concave-convex pattern is transferred is required to have a superior film shaped
mold-releasing property, a superior adhesion property to the substrate, and a superior
transferability of the concave-convex pattern.
[0036] It is desired that the concave-convex pattern of the film-shaped mold, for example,
be an irregular concave-convex pattern in which the pitches of concavities and convexities
are ununiform and the orientations of the concavities and convexities have no directivity.
The average pitch of the concavities and convexities of the concave-convex pattern can be
within a range from 100 nm to 1500 nm, and is more preferably within a range from 200
nm to 1200 nm. The average height of the concavities and convexities of the
concave-convex pattern is preferably in a range of 20 nm to 200 nm, and more preferably
in a range of 30 nm to 150 nm. The light scattered and/or diffracted by such a
concave-convex pattern is not light having single wavelength or wavelength having a
narrow band. The light scattered and/or diffracted by such a concave-convex pattern has
a range of wavelength relatively broad, has no directivity, and is directed in various
16
directions.
[0037] A roll process using the pressing roll as depicted in Fig. 4 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 the 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 the long
film-shaped 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 releasing
force (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. Since the flexible film-shaped mold is used as the mold, when the
concave-convex pattern of the mold is transferred to the sol-gel material layer 42 formed
on the relatively hard substrate 10, the pattern of the mold can be uniformly pressed against
the sol-gel material layer formed on the entire surface of the substrate. Accordingly, the
concave-convex pattern of the mold can be faithfully transferred to the sol-gel material
layer, thereby making it possible to suppress the occurrence of transfer omission and/or
transfer failure.
[0038] In the transfer step, the film-shaped mold may be pressed against the coating film
while the coating film is heated. As the method for heating the coating film, for example,
the heating through the pressing roll may be performed, 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 preferred that a heater be included in the
pressing roll, the heater may be 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. The pressing roll is preferably a roll of which surface is coated with a resin
material with heat resistance, such as ethylene propylene diene rubber (EPDM), silicone
rubber, nitrile rubber, fluororubber, acrylic rubber, and chloroprene rubber. A supporting
roll may be provided to face the pressing roll while sandwiching the substrate
therebetween in order to resist the pressure applied by the pressing roll. Alternatively, a
support base supporting the substrate may be provided.
[0039] The heating temperature of the coating film at the time of the pressing may be in a
range of 40 degrees Celsius to 150 degrees Celsius. In a case that the heating is
performed by use of the pressing roll, the heating temperature of the pressing roll may be
also in a range of 40 degrees Celsius to 150 degrees Celsius. By heating the pressing roll
as described above, the mold can be easily released (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 degrees Celsius, the mold cannot be expected to be released (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 concave-convex pattern is not transferred sufficiently. By
performing the pressing while heating the coating film, an effect similar to that obtained in
pre-baking of the sol-gel material layer which will be described later can be expected.
[0040] After the mold is pressed against the coating film (sol-gel material layer), the
coating film may be subjected to the pre-baking. In a case that the pressing is performed
without heating of the coating film, it is preferred that the pre-baking be performed. The
pre-baking promotes the gelation of the coating film to solidify the pattern, and thus the
pattern is less likely to be collapsed during the releasing. That is, the pre-baking has two
roles of the reliable pattern formation and the improvement of releasing property (peeling
property) of the mold. In a case that the pre-baking is performed, the heating is
preferably performed at temperatures of 40 degrees Celsius to 150 degrees Celsius in the
atmosphere.
[0041] The mold is released or peeled off from the coating film (sol-gel material layer)
after the transfer step or the pre-baking step (step S5 of Fig. 3). Since the roll process is
used as described above, the releasing force (peeling force) may be smaller than that of a
plate-shaped mold used in the pressing system, and it is possible to easily release the mold
from the coating film without the coating film remaining on the mold. In particular, since
the pressing is performed while the coating film is heated, the reaction is more likely to
progress, which facilitates the releasing of the mold from the coating film immediately
after the pressing. In order to promote the releasing property (peeling property) of the
mold, it is possible to use a peeling roll (releasing roll). As depicted in Fig. 4, by
providing a peeling roll (releasing roll) 123 on the downstream side of the pressing roll 122
1$
and supporting the film-shaped mold 50 while urging the film-shaped mold 50 toward the
coating film 42 with the rotating peeling roll 123, a state in which the film-shaped mold 50
is attached to the coating film can be maintained by a distance between the pressing roll
122 and the peeling roll 123 (for a certain period of time). Then, by changing a path of
the film-shaped mold 50 such that the film-shaped mold 50 is pulled up above the peeling
roll 123 on the downstream side of the peeling roll 123, the film-shaped mold 50 is peeled
off (released) from the coating film 42 in which the concavities and convexities are formed.
The pre-baking or the heating of the coating film may be performed during a period in
which the film-shaped mold 50 is attached to the coating film. In a case that the peeling
roll 123 is used, by peeling the coating film from the mold 50 while heating the coating
film, for example, to temperatures of 40 degrees Celsius to 150 degrees Celsius, the
coating film can be peeled more easily.
[0042] After the mold is released (peeled off) from the coating film (sol-gel material
layer) 42 on the substrate 10, the coating film is subjected to the main baking (step S6 of
Fig. 3). Hydroxyl group and the like contained in the layer of sol-gel material such as
silica, which forms the coating film, is desorbed or eliminated by the main baking to
further harden (solidify) the coating film. It is preferred that the main baking 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 thus the substrate 10 with
the concave-convex pattern layer 12 which corresponds to the concave-convex pattern of
the film-shaped mold is obtained. In this situation, in a case that the sol-gel material layer
is made of the silica, depending on the baking temperature and the baking time, the silica is
amorphous, crystalline, or in a mixture state of the amorphous and the crystalline.
[0043]
[Auxiliary layer]
The auxiliary layer 14 is formed on the concave-convex pattern layer 12. The
auxiliary layer 14 makes the concave-convex pattern on the surface of the concave-convex
pattern layer 12 smooth or gentle (shallow waves) to prevent the occurrence of a leak
current which would be otherwise caused in the first electrode layer 16 formed on the
auxiliary layer 14. The experiment performed by the inventors of the present invention
has shown that, in a case that the auxiliary layer 14 is formed to have no concave-convex
pattern on the surface on the side of the first electrode 16 (hereinafter referred to as the
surface of the auxiliary layer 14 as appropriate); in other words, in a case that the surface
of the auxiliary layer 14 is formed to be flat surface, the light extraction efficiency is
reduced instead of being improved as compared with the case in which the auxiliary layer
14 has the concave-convex pattern on the surface. The reason thereof is assumed by the
inventors as follows. That is, in a case that the surface of the auxiliary layer 14 is flat, the
first electrode 16, the organic layer 18, and the second electrode 20 are also flat. This
causes the light, which comes from the organic layer 18 to arrive at the second electrode 20,
to be absorbed by free electron of the second electrode 20, which is so-called plasmon
absorption. For this reason, the concave-convex shape on the surface of the auxiliary
layer 14 is required to be controlled to have a concave-convex shape in which the depths of
concavities and convexities are not deeper than those of the concave-convex pattern layer
12 but they are not flat. In the present invention, in order to express the concave-convex
shape on the surface of the auxiliary layer 14, i.e., the degree of concavities and
convexities (depths), there is used the change ratio of the standard deviation of depths of
concavities and convexities (hereinafter referred to as "second concave-convex depth" as
appropriate) of the concave-convex shape on the surface of the auxiliary layer 14 on the
side opposite to the substrate 10 (hereinafter referred to as "second concave-convex shape
as appropriate) with respect to the standard deviation of depths of concavities and
convexities (hereinafter referred to as "first concave-convex depth" as appropriate) of the
concave-convex shape on the surface of the concave-convex pattern layer 12 (hereinafter
referred to as "first concave-convex shape as appropriate). This change ratio is
appropriately referred as "shape change ratio" in this context. That is, the shape change
ratio W is represented by the following formula:
W = (ol - o2)/ol
in the formula, ol is the standard deviation of the first concave-convex depth and
a2 is the standard deviation of the second concave-convex depth.
[0044] In the present invention, it is desired that the shape change ratio be 70% or less,
and especially it is desired that the shape change ratio be in a range of 20% to 70%. In a
case that the auxiliary layer has the second concave-convex shape (waves), each surface of
the first electrode layer 16 and the organic layer 18 to be stacked on the auxiliary layer 14
has a concave-convex shape which follows the second concave-convex shape. Thus, the
diffraction grating effect similar to that obtained in the concave-convex pattern layer 12 is
more likely to be obtained at the boundaries between respective layers. However, in a
case that the shape change ratio is too small, the second concave-convex shape resembles
the first concave-convex shape and thus, it is assumed that a leak current is more likely to
occur due to conspicuous projections formed especially on the first electrode 16.
Therefore, it is preferred that the shape change ratio be 20% or more. On the other hand,
in a case that the shape change ratio is high, that is, in a case that the surface of the
auxiliary layer 14 is smooth or planarized, the occurrence of the leak current is easily
prevented, but the plasmon absorption on the surface of the second electrode is more likely
to occur due to the reflection from the surface of the auxiliary layer 14, and as a result, the
light extraction efficiency is reduced. Therefore, the surface shape of the auxiliary layer
14 is controlled so that the shape change ratio is 70% or less. Further, as to the
concave-convex shape on the surface of the auxiliary layer 14 itself, it is assumed that the
plasmon absorption is more likely to occur when the standard deviation of the second
concave-convex depth is less than 2.5 nm.
[0045] The film thickness of the auxiliary layer 14 has an influence also on multiple
interference caused in the stacked structure of the organic EL element. Thus, the
thickness of the auxiliary layer 14 can be adjusted appropriately to optimize or shift the
position of peak wavelength of the light extracted from the substrate.
[0046] It is preferred that the auxiliary layer 14 be made of inorganic materials such as
Ti02, ZnO, ZnS, ZrO, BaTi03, and SrTi02. Of the above materials, Ti02 is preferable in
view of film formation performance and refractive index. The auxiliary layer 14 can be
formed by any method. It is possible to use a method of coating the concave-convex
pattern layer 12 with the solution of the sol-gel material and making the solution turn into a
gel, a method of coating the concave-convex pattern layer 12 with a dispersion liquid of
inorganic fine particles and drying the coating film, a liquid phase deposition (LPD), and
the like. In a case that a Ti02 dispersion liquid is used, the sizes of Ti02 fine particles
cannot have sizes smaller than 10 nm and further Ti02 fine particles are more likely to be a
secondary aggregate, which cannot be disintegrated completely. As a result, the surface
roughness of the auxiliary layer 14 exceeds 5 nm, which causes a leak current easily.
Therefore, it is preferred that a sol-gel method be used, in which method the sol-gel
solution containing titanium alkoxide and/or an organic compound is applied by spin
coating or the like and the applied sol-gel solution is allowed to turn into a gel by being
dried and heated.
[0047]
[First electrode]
"Si
The first electrode 16 is formed on the auxiliary layer 14. The first electrode 16
has a transmissive ability or permeability to allow the light from the organic layer 18
formed on the first electrode 16 to pass toward the substrate side. Therefore, the first
electrode 16 is also referred to as a transparent electrode. As the electrode material of the
first electrode 16, 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, ITO is preferable from the viewpoint of transparency and electrical
conductivity.
[0048] As the method for forming the first electrode 16, any known method such as a
vapor deposition method, a sputtering method, a CVD method, and a spray method can be
employed as appropriate. Of these methods, the sputtering method is preferably
employed from the viewpoint of improving the adhesion property. After forming the film
of an electrode material layer by the sputter method or the like, a desired electrode pattern
can be formed by a photolithography process (photoetching method).
[0049] The first electrode 16 may have an actual film thickness ranging from 80 nm to
200 nm or an optical film thickness ranging from 160 nm to 400 nm. In the present
invention, in a case that the thickness is less than the lower limit, the electrical conductivity
is more likely to be insufficient. In a case that the thickness exceeds the upper limit, there
is possibility that the transparency is so insufficient that the emitted light (EL light) is more
likely to stationary stand in the first electrode 16 and the auxiliary layer 14, which causes
the deterioration of the light extraction efficiency. Especially, in a case that the value of
refractive index of the auxiliary layer 14 is close to the value of refractive index of the first
electrode 16 and that the total film thickness of the auxiliary layer 14 and the first electrode
16 is not less than a predetermined thickness, the emitted light is more likely to stationary
stand in the two layers. According to the results of Examples which will be described
later, etc., it is desired that the total optical film thickness (the total film thicknesses
expressed in optical path length) of the auxiliary layer and the first electrode be in a range
of 160 nm to 400 nm. Normally, a film thickness which allows the light to stationary
stand in the film is supposed to be X/4. This has a slight influence on the above range,
because the light-emission central wavelength of the organic EL element is about 600 nm.
In a case that the total optical film thickness exceeds 400 nm, the emitted light is more
likely to stationary stand in the two layers, which causes the deterioration of the light
extraction efficiency. Further, any structural defect such as a crack in any of the layers is
more likely to occur. In a case that the total optical film thickness is less than 160 nm,
foreign matters and defects such as a recess or depression generated on the
concave-convex pattern layer cannot be repaired by those layers, and thus a leak current is
more likely to occur. It is preferred that the total optical film thickness be in a range of
160 nm to 250 nm. Similar to the auxiliary layer 14, the film thickness of the first
electrode layer 16 has an influence also on the multiple interference caused in the stacked
structure of the organic EL element. Thus, in order to optimize the position of peak
wavelength of the light extracted from the substrate, the thickness of the first electrode
layer 16 may be adjusted together with or independently from the auxiliary layer 14. In
the present description, the thickness means the actual film thickness unless noted as the
optical film thickness.
[0050] In the present invention, in a case that the substrate 10 is made from glass material
and that silica-based sol-gel material is used for forming the concave-convex pattern layer
(concave-convex forming layer) 12, it is desired that the following relation between the
refractive index of the first electrode layer 16, the refractive index of the auxiliary layer 14,
the refractive index of the concave-convex forming layer 12, and the refractive index of the
substrate 10 be satisfied. Assuming that the refractive indexes of the substrate 10, the
concave-convex forming layer 12, the auxiliary layer 14, and the first electrode layer 16
are nO, nl, n2, and n3, respectively, n2 > n3 > nl < nO is satisfied. Further, in order to
prevent the total reflection at the interface between the concave-convex pattern layer and
the substrate, it is preferred that 03, a highly active alkaline earth metal such as Ca, Ba, or Cs, an
organic insulating material, or the like. Further, from the viewpoint of facilitating the
hole injection from the first electrode 16, it is allowable to provide, between the organic
layer 18 and the first electrode 16, 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.
[0054] In a case that the organic layer 18 is a stacked body formed of the hole
transporting layer, the light-emitting layer, and the electron transporting layer, the
thicknesses of the hole transporting layer, the light-emitting layer, and the electron
transporting layer are preferably in a range of 1 nm to 200 nm, in a range of 5 nm to 100
nm, and in a range of 5 nm to 200 nm, respectively. As a method for stacking the organic
layer 18, 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.
[0055]
[Second electrode]
The second electrode 20 as a metal electrode is provided on the organic layer 18.
Materials of the second electrode 20 are not particularly limited, and a substance having a
small work function can be used as appropriate. Examples of the materials of the second
electrode 20 include aluminum, MgAg, Mgln, and AlLi. The thickness of the second
electrode 20 is preferably in a range of 50 nm to 500 nm. In a case that the thickness is
less than the lower limit, the electrical conductivity is more likely to be decreased. In a
case that the thickness exceeds the upper limit, there is possibility that the repair 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 second electrode 20. Accordingly, an organic EL element 30 having the structure as
depicted in Fig. 1 can be obtained.
[0056] Since the second electrode 20 is the metal electrode, a polarizing plate may be put
on the second electrode 20 in order to take a measure against specular reflection of the
metal electrode. Further, it is allowable to seal the periphery of the organic EL element
30 with a sealing material to prevent deterioration of the organic EL element 30 due to
moisture and/or oxygen.
[0057] Fig. 2 depicts another embodiment of the organic EL element of the present
invention. An organic EL element 40 includes a lens layer 22 on the outer surface of the
substrate 10 of the organic EL element depicted in Fig. 1. By providing such a lens layer
22, the light passing through the substrate 10 is prevented from being totally reflected at
the interface between the substrate 10 (including the lens layer 22) and air, which makes it
possible to improve the light extraction efficiency. As the lens layer 22, it is possible to
adopt, for example, a hemispherical lens and a lens having corrugated structure. The lens
layer 22 is not particularly limited, provided that the lens layer 22 is usable for extraction
of the light of the organic EL element. Any optical member having a structure capable of
extracting the light to the outside of the element can be used as the lens layer 22. As the
lens layer 22, various lens members, a diffusion sheet or plate made of a transparent body
into which diffusion material is blended and the like may be used. The various lens
members include a convex lens such as the hemispherical lens, a concave lens, a prism lens,
a cylindrical lens, a lenticular lens, a microlens formed of a concave-convex layer which
can be formed by the method similar to a method for manufacturing a diffraction grating
substrate as will be described later, and the like. Of the above examples, the lens member
is preferably used because the light can be extracted efficiently. Further, a plurality of
lens members may be used as the lens layer 22. In this case, a so-called microlens (array)
may be formed by arranging or arraying fine or minute lens members. A commercially
7.b
available product may be used for the lens layer 22.
[0058] In a case that the microlens formed of the concave-convex layer which can be
formed by the method similar to the method for manufacturing the diffraction grating
substrate is used as the lens layer 22, and that a Fourier-transformed image is obtained by
performing a two-dimensional fast Fourier-transform processing on an concavity and
convexity analysis image obtained by analyzing the concave-convex shape of the
concave-convex layer of the microlens with an atomic force microscope, it is preferred that
the Fourier-transformed image have a shape showing a circular or annular pattern
substantially centered at an origin at which an absolute value of wavenumber is 0 um"1.
As for the microlens formed of such a concave-convex layer, the concave-convex shape is
isotropic as viewed from various cross-sectional directions. Thus, in a case that the light
is allowed to enter from the side of one surface (surface in contact with the substrate) and
that the light is extracted from the surface in which the concave-convex shape is formed, it
is possible to sufficiently reduce the angle dependence of the extracted light (the angle
dependence of luminance) and the change in chromaticity.
[0059] Further, in the case that the microlens formed of the concave-convex layer is used
as the lens layer 22, it is preferred that the Fourier-transformed image obtained from the
concave-convex shape be present within a region where the absolute value of wavenumber
is in a range of 1 urn"1 or less. In a case that such a Fourier-transformed image satisfies
the above requirement, it is possible to sufficiently reduce the angle dependence of the
extracted light and the change in chromaticity at a higher level. Further, it is preferred
that the circular or annular pattern of the Fourier-transformed image be present within a
region where the absolute value of wavenumber is in a range of 0.05 um"1 to 1 um"1, from
the viewpoint of refracting or diffracting a light spectrum in a visible region (380 nm to
780 nm) efficiently. It is further preferred that the circular or annular pattern of the
Fourier-transformed image be present within a region where the absolute value of
wavenumber is in a range of 0.1 urn"1 to 0.5 um"1. In a case that the circular or annular
pattern is not present in the region where the absolute value of wavenumber is in the above
range, that is, in a case that the number of bright spots, of the bright spots forming the
Fourier-transformed image showing the circular or annular pattern, which are present in the
above range, is less than 30%, refraction sufficient for use as a lens for extracting the light
is less likely to be obtained. Further, it is further preferred that the pattern of the
Fourier-transformed image be the annular pattern from the viewpoint of obtaining
satisfactory effect for the light having wavelengths in the visible region (380 nm to 780
nm).
[0060] In the case that the micro lens formed of the concave-convex layer is used as the
lens layer 22, the average pitch of concavities and convexities of the microlens is
preferably in a range of 2 um to 10 um, and more preferably in a range of 2.5 um to 5 urn.
In a case that the average pitch of the concavities and convexities is less than the lower
limit, the diffraction effect as the diffraction grating is greater than the refraction effect for
extracting the light of the optical member to the outside. This reduces the light extraction
effect and increases the angle dependence of the extracted light, and as a result, enough
light extraction is less likely to be obtained depending on the measurement position. On
the other hand, in a case that the average pitch of the concavities and convexities exceeds
the upper limit, the diffraction effect is less likely to be obtained and the characteristics of
the microlens are liable to be similar to the characteristics of a normal hemispherical lens.
The average height of concavities and convexities of the microlens is preferably in a range
of 400 nm to 1000 nm, more preferably in a range of 600 nm to 1000 nm, and further
preferably in a range of 700 nm to 900 nm. In a case that the average height (depth) of
the concavities and convexities is less than the lower limit, the sufficient refraction effect
or diffraction effect is less likely to be obtained. On the other hand, in a case that the
average height (depth) of the concavities and convexities exceeds the upper limit,
mechanical strength is more likely to be reduced, which could cause a crack easily at the
time of manufacture and/or at the time of use. The microlens formed of the
concave-convex layer can be formed by adopting the method for manufacturing the
diffraction grating substrate as will be described later, appropriately changing the
conditions and the like for forming a master block, and appropriately adjusting the
characteristics (size and the like) of the concave-convex shape.
[0061] As the lens layer 22 for extracting the light to the outside, those having various
sizes and shapes can be used depending on the use, the size, the structure, and the like of
the organic EL element. From the viewpoint of preventing the reflection at the interface
between air and the surface of the lens layer 22 (the structure for extracting the light to the
outside), it is preferred that the microlens formed of the hemispherical lens and the
concave-convex layer which can be formed by the method similar to the method for
manufacturing the diffraction grating substrate as will be described later, be used. In a
case that the thickness of the organic EL element considered to be unimportant (in a case
that there is no problem with a thick organic EL element), it is preferred that the
hemispherical lens be used. In a case that the thickness of the organic EL element is
considered to be important (in a case that a thinner organic EL element is preferred), it is
preferred that the microlens formed of the concave-convex layer be used. In a case that
the microlens formed of the concave-convex layer, which can be formed by the method
similar to the method for manufacturing the diffraction grating substrate, is used, the
concave-convex shape is isotropic as viewed from various cross-sectional directions.
Thus, in a case that the light is allowed to enter from the side of one surface (surface in
contact with the substrate) and that the light is extracted from the surface in which the
concave-convex shape is formed, it is possible to sufficiently reduce the angle dependence
of the extracted light (the angle dependence of luminance) and the change in chromaticity.
[0062] The hemispherical lens suitable as the lens layer 22 is preferably a hemispherical
lens having the area of the bottom surface 1 to 10 times larger than the light emission area
of the organic EL element. That is, in the case that the hemispherical lens is used, it is
preferred that the semispherical lens having the area of the bottom surface 1 to 10 times
larger than the area of one pixel which is the light emission area of the organic EL element
be used to completely cover the one pixel which is the light emission area of the organic
EL element with the bottom surface of the hemispherical lens. In a case that the area of
the bottom surface of the hemispherical lens is less than the lower limit, the component, of
the light emitted at the organic EL element, coming into a spherical surface of the
hemispherical lens from an oblique direction is more likely to increase. On the other
hand, in a case that the area of the bottom surface of the hemispherical lens exceeds the
upper limit, the size of the organic EL element is too big and the hemispherical lens is
liable to be expensive.
[0063] The material of the lens layer 22 is not particularly limited, an optical member
made of any material can be used. It is possible to use, for example, transparent inorganic
materials such as glass and transparent resin materials made of transparent polymers and
the like, the transparent resin materials including polyester resin such as polyethylene
terephthalate and the like, cellulose resin, acetate resin, polyethersulfone resin,
polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, and acylic resin.
Further, in order to prevent the reflection at the interface between the organic EL element
and the lens layer 22, it is preferred that the lens layer 22 be stacked on the substrate 10 via
a pressure-sensitive adhesive layer and/or an adhesive layer to prevent air from being
2 * - ^
sandwiched between the organic EL element and the lens layer 22.
[0064] As for the lens layer 22, a protective layer may be stacked on the surface of the
optical member (on the surface in which the concave-convex shape is formed, when the
microlens formed of the concave-convex layer is used as the lens layer 22) from the
viewpoint of improving wear resistance and scratch resistance of the surface thereof. It is
possible to use a transparent film or a transparent inorganic deposited layer as the
protective layer. The transparent film is not particularly limited, and any transparent film
can be used. Examples of the transparent film include films made of transparent
polymers such as polyester resin including polyethylene terephthalate and the like,
cellulose resin, acetate resin, polyethersulfone resin, polycarbonate resin, polyamide resin,
polyimide resin, polyolefin resin, and acylic resin. Further, the transparent film may be
used as follows. That is, the pressure-sensitive adhesive layer or the adhesive layer is
formed on one surface of the transparent film, and the transparent film with the
pressure-sensitive adhesive layer or the adhesive layer is put on the surface of the optical
member. (Note that the transparent film may be put on the surface of the lens layer 22 so
as to leave a space formed between the adjacent convex portions in a case that the
microlens formed of the concave-convex layer is used as the lens layer 22.) As the
pressure-sensitive adhesive or the adhesive agent, it is possible to use, for example, acrylic
adhesive, polyurethane adhesive, and polyester adhesive, ethylene-vinyl acetate copolymer,
natural rubber adhesive, synthetic rubber pressure-sensitive adhesive such as
polyisobutylene, butyl rubber, styrene-butylene-styrene copolymer, and
styrene-isoprene-styrene block copolymer.
[0065] In a case that the inorganic deposited layer is stacked as the protective layer, it is
possible to appropriately use any known metallic material which can form a transparent
inorganic layer by an evaporation method. Examples of the metallic material include
oxide, nitride and sulfide of metal such as Sn, In, Te, Ti, Fe, Co, Zn, Ge, Pb, Cd, Bi, Se, Ga,
and Rb. From the viewpoint of sufficiently preventing the deterioration caused by
oxidation, it is preferred that TiCh be used as the metallic material. From the viewpoint of
obtaining high luminance at a low cost, it is preferred that ZnS be used as the metallic
material. The method for forming the inorganic deposited layer is not particularly limited,
and it is possible to manufacture the inorganic deposited layer by using any physical vapor
deposition equipment as appropriate.
[0066] In the following description, the organic EL element of the present invention will
be specifically explained with examples. The present invention, however, is not limited
to the following examples.
Examples
[0067]
[Example 1]
In this example, a diffraction grating substrate (substrate provided with a
concave-convex pattern layer) is manufactured, and then an organic EL element is
manufactured by use of the diffraction grating substrate. At first, a diffraction grating
mold having a concave-convex surface is manufactured by the BCP method in order to
manufacture the diffraction grating substrate.
[0068]

There 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 = 750,000
Mn of PMMA segment = 720,000
Mn of block copolymer = 1,470,000
Volume ratio between PS segment and PMMA segment (PS:PMMA) = 54:46
Molecular weight distribution (Mw/Mn) = 1.21
Tg of PS segment = 107 degrees Celsius
Tg of PMMA segment = 134 degrees Celsius
[0069] The volume ratio of the first polymer segment and the second polymer segment
(first polymer segment: 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 g/ cm3. The number average molecular weights (Mn)
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 SuperHlOOO, 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, revised).
[0070] Toluene was added to 150 mg of the block copolymer and 37.5 mg of
Polyethylene Glycol 2050 (average Mn = 2050) manufactured by Sigma-Aldrich Co. LLC.
as polyethylene oxide so that the total amount thereof was 15 g, followed by dissolving
them. Accordingly, a solution of the block copolymer was prepared.
[0071] The solution of the block copolymer was filtrated or filtered through a membrane
filter having a pore diameter of 0.5 um to obtain a block copolymer solution. A glass
substrate was coated with the mixed solution, which was obtained by mixing 1 g of
KBM-5103 produced by Shin-Etsu Chemical Co., Ltd., 1 g of ion-exchanged water, 0.1 ml
of acetic acid, and 19 g of isopropyl alcohol, by 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 45 seconds). The grass substrate was subjected to treatment at a temperature
of 130 degrees Celsius for 15 minutes to obtain a silane coupling treated glass. The silane
coupling treated glass as a base member was coated with the obtained block copolymer
solution by spin coating to form a thin film having a thickness of 150 nm to 170 nm. The
spin coating was performed at a spin speed of 200 rpm for 10 seconds, and then performed
at a spin speed of 300 rpm for 30 seconds.
[0072] Subsequently, the base material having the thin film formed thereon was subjected
to a solvent annealing process by being stationarily placed in a desiccator filled with
chloroform vapor at room temperature for 24 hours. In the desiccator (5 liters capacity), a
screw vial filled with 100 g of chloroform was placed and the atmosphere in the desiccator
was filled with the chloroform at a saturated vapor pressure. Concavities and convexities
were observed on the surface of the thin film after the solvent annealing process, and it was
found out that micro phase separation of the block copolymer forming the thin film was
caused. The observation of the cross-section of the thin film with the transmission
electron microscope (TEM) (produced by Hitachi, Ltd., product name: H-710FA) showed
that the circular cross-sections of PS portions were aligned to form two tiers (stages) in a
direction (height direction) perpendicular to the surface of the substrate while being
separated from each other in a direction parallel to the surface of the substrate.
•3*. tz
Considering the cross-section of the thin film together with the analysis image of the
atomic force microscope, it was found out that the phase of each PS portion was separated
from the PMMA portion to have a horizontal cylinder structure. The state of phase
separation was such that each PS portion was a core (island) surrounded by the PMMA
portion (sea).
[0073] A thin nickel layer of about 20 nm was formed as a current seed layer by
sputtering on the surface of the thin film, for which the solvent annealing process had been
performed to allow the thin film to have the wave shape. Subsequently, the base member
with the thin film was subjected to an electroforming process (maximum current density:
0.05 A/cm2) in a nickel sulfamate bath at a temperature of 50 degrees Celsius to precipitate
nickel until the thickness of nickel became 250 um. The base member with the thin film
was mechanically peeled off from the nickel electroforming body obtained as described
above. Then, the nickel electroforming body was immersed in tetrahydrofuran solvent for
2 hours. Thereafter, polymer component(s) adhering to a part of the surface of the
electroforming body was (were) removed by repeating the following process three times.
That is, the nickel electroforming body was coated with an acrylic-based UV curable resin;
and the acrylic-based UV curable resin coating the nickel electroforming body was cured;
and then the cured resin was peeled off. 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. Then,
the nickel electroforming body was subjected to a UV-ozone process for 10 minutes.
[0074] Subsequently, the nickel electroforming body was immersed in HD-2101TH
manufactured by Daikin Chemicals Sales, Co., Ltd. for about 1 minute and was dried, and
then stationarily placed overnight. The next day, the nickel electroforming body was
immersed in HDTH manufactured by Daikin Chemicals Sales, Co., Ltd. to perform an
ultrasonic cleaning process for about 1 minute. Accordingly, a nickel mold for which a
mold-release treatment had been performed was obtained.
[0075] Subsequently, a PET substrate (manufactured by Toyobo Co., Ltd., product name:
COSMOSHINE A-4100) was coated with a fluorine-based UV curable resin. Then, the
fluorine-based UV curable resin was cured by irradiation with ultraviolet rays at 600
mJ/cm2, with 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 made of the PET substrate with the resin film to which the surface
profile of the nickel mold was transferred was obtained.
[0076]

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 (refractive index n = 1.52 (A, = 550 nm)) of 15 x 15 x 0.11 cm by 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 um.
However, the doctor blade was adjusted so that the film thickness of the coating film was
40 um by sticking an imide tape having a thickness of 35 urn to the doctor blade. After
the elapse of 60 seconds from the sol coating, the diffraction grating mold manufactured as
described above was pressed against the coating film on the glass plate by use of the
pressing roll heated to 80 degrees Celsius while the pressing roll was moved and rotated.
After the completion of pressing against the coating film, the mold was manually peeled
off (released) from the coating film on the glass plate and the coating film on the glass
plate was subjected to the main baking by being heated for 60 minutes in an oven of 300
degrees Celsius. Accordingly, it was obtained the substrate having the concave-convex
pattern layer in which the pattern of the diffraction grating mold was transferred to the
sol-gel material, that is, the diffraction grating substrate. As the pressing roll, it was used
a roll which included a heater therein and had the outer periphery covered with
heat-resistant silicon of a thickness of 4 mm, the roll having a diameter (cp) of 50 mm and a
length of 350 mm in an axial direction of the shaft.
[0077] An analysis image of the shape of the concavities and convexities on the surface
of the concave-convex pattern layer of the diffraction grating substrate was obtained by use
of an atomic force microscope (a scanning probe microscope equipped with an
environment control unit "Nanonavi II Station/E-sweep" manufactured by Hitachi
High-Tech Science Corporation). Analysis conditions of the atomic force microscope
were as follows.
Measurement mode: dynamic force mode
Cantilever: SI-DF40 (material: Si, lever width: 40 um, diameter of tip of chip: 10 nm)
Measurement atmosphere: in air
Measurement temperature: 25 degrees Celsius
[0078] A concavity and convexity analysis image was obtained as described above by
performing a measurement in a randomly selected measuring region of 3 urn square
(length: 3 um, width: 3 um) in the diffraction grating substrate. 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 concave-convex pattern obtained by the analysis
image in this example was 56 nm.
[0079] A concavity and convexity analysis image was obtained as described above by
performing a measurement in a randomly selected measuring region of 3 um square
(length: 3 um, width: 3 um) in the diffraction grating substrate. 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
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 (Am'1, and that the circular pattern was
present within a region where the absolute value of wavenumber was in a range of 10 um"1
or less.
[0080] 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 pattern of 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 a case
where a part of the contour of the outer circle 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 um'1 or
less (more preferably 1.25 to 10 um"1, further preferably 1.25 to 5 um"1)" 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 urn"1 or less (more preferably 1.25 to 10 um"1, and further preferably 1.25 to 5 um"1).
Regarding the relationship between the pattern of the concave-convex structure and the
Fourier-transformed image, the followings have been appreciated. That is, in a case that
the concave-convex 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 concave-convex structure is entirely isotropic in an XY direction and has the pitch
distribution, a circular or annular Fourier-transformed image appears. In a case that the
concave-convex structure has a single pitch, the annular shape appeared in the
Fourier-transformed image tends to be sharp.
[0081] The 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
processing.
[0082]

A concavity and convexity analysis image was obtained as described above by
performing a measurement in a randomly selected measuring region of 3 um square
(length: 3 um, width: 3 um) in the diffraction grating. Distances between randomly
selected adjacent convex portions or between randomly selected adjacent concave portions
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 pitch of the concavities and
convexities. The average pitch of the concavities and convexities of the concave-convex
pattern layer calculated using the analysis image obtained in this example was 73.5 nm.
[0083]

A concavity and convexity analysis image was obtained by performing a
measurement in a randomly selected measuring region of 3 um square (length: 3 um,
width: 3 um) in the concave-convex layer. Here, data of each of the heights of the
concavities and convexities was determined at 16384 (128 columns x 128 rows) or more
measuring points in the measuring region on the nanometer scale. By using E-sweep in
this example, a measurement at 65536 points (256 columns x 256 rows) (a measurement
with a resolution of 256 pixels x 256 pixels) was conducted in a measuring region of 3 um
36
square. Regarding the thus measured heights (unit: nm) of the concavities and
convexities, first, a measuring point P which had the largest height from the surface of the
substrate among all the measuring points was determined. Then, while a plane which
included the measuring point P and was parallel to the surface of the substrate was taken as
a reference plane (horizontal plane), values of depths from the reference plane (the
differences each obtained by subtracting the height from the substrate at one of the
measuring points from the value of the height from the substrate at the measuring point P)
were determined as the data of depth of concavities and convexities. The depth data of
concavities and convexities could be determined by automatic calculation with software in
E-sweep. The values determined by automatic calculation could be used as the data of
depth of concavities and convexities. After the data of depth of concavities and
convexities was determined at each measuring point as described above, the average value
(m) of the depth distribution of the concavities and convexities could be determined by
calculation according to the following formula (I):
[0084]
[Formula I]
1 A
m -—y x i (i)
The average value (m) of depth distribution of concavities and convexities of the
concave-convex pattern layer of the diffraction grating obtained in this example was 40.3
nm.
[0085]

Similar to the method for measuring the average value (m) of the depth
distribution, the data of depth of the concavities and convexities were obtained by
performing a measurement at 16384 or more measuring points (vertical: 128 points x
horizontal: 128 points) in a measuring region of 3 um square of the concave-convex
pattern layer. In this example, a measurement was performed adopting 65536 measuring
points (vertical: 256 points x horizontal: 256 points). Thereafter, the average value (m) of
the depth distribution of the concavities and convexities and the standard deviation (a) of
depths of the concavities and convexities were calculated on the basis of the data of depth
of concavities and convexities depth data of the measuring points. Note that, the average
^7
value (m) could be determined by calculation according to the formula (I) as described
above. Meanwhile, the standard deviation (a) of depths of the concavities and
convexities could be determined by calculation according to the following formula (II):
[0086]
[Formula II]
1 N
(I I)
NtM^
In the formula (II), "N" represents the total number of measuring points (the
number of all the pixels), "x," represents data of depth of the concavities and convexities at
the i-th measuring point, and "m" represents the average value of the depth distribution of
the concavities and convexities. The standard deviation (ol) of depths of concavities and
convexities in the concave-convex pattern layer was 19.5 nm.
[0087]
Accumulation or stacking of auxiliary layer>
The glass substrate, on which the concave-convex pattern layer (sol-gel material
layer) as the diffraction grating obtained as described above was formed, was cut to have a
size of 12 mm x 20 mm, and organic matter and the like adhering to the glass substrate was
removed by performing ultrasonic cleaning by use of IPA which is an organic solvent in
order to eliminate foreign matter and the like adhering to the glass substrate.
Subsequently, the glass substrate was subjected to the UV ozone process for 3 minutes in a
state of being separated from the light source by 3 cm. Then, TiCh sol-gel solution
(produced by Kojundo Chemical Lab. Co., Ltd., product name: Ti-05-P) was diluted with
ethanol and IPA. The ethanol and IPA were used in the ratio by weight (%) of 80 to 12
(ethanol:IPA = 80:12). The diluted solution was filtrated or filtered through a filter of
0.50 umcp and the glass substrate was coated with the diluted solution by spin coating.
The glass substrate was baked for 1 hour in an oven of 300 degrees Celsius. Accordingly,
the Ti02 film as the auxiliary layer was obtained on the pattern of the concave-convex
pattern layer.
[0088] Subsequently, ITO film having a thickness of 80 nm was formed on the TiC^ film
by sputtering. Then, as the organic layer, a hole transporting layer (4,4',4"
tris(9-carbazole)triphenylamine, thickness: 35 nm), a light emitting layer
(tris(2-phenylpyridinato)iridium(III) complex-doped
4,4',4"tris(9-carbazole)triphenylamine, thickness: 15 nm;
tris(2-phenylpyridinato)iridium(III) complex-doped
l,3,5-tris(N-phenylbenzimidazole-2-yl)benzene, thickness: 15 nm), and an electron
transporting layer (l,3,5-tris(N-phenylbenzimidazole-2-yl)benzene, thickness: 65 nm),
were each stacked by a vapor deposition method. Further, a lithium fluoride layer
(thickness: 1.5 nm) and a metal electrode (aluminum, thickness: 50 nm) were formed by
the vapor deposition method. Accordingly, as depicted in Fig. 1, there was obtained the
organic EL element 30 in which the concave-convex pattern layer 12, the TiC^ film as the
auxiliary layer 14, the transparent electrode as the first electrode 16, the organic layer 18,
and the metal electrode as the second electrode 20 were formed on the substrate 10 in this
order.
[0089] As for the film thickness of the Ti02 film as the auxiliary layer 14, a measurement
was performed at 100 measuring points by use of the cross-sectional TEM image of the
organic EL element. In this situation, as depicted by the arrows in Fig. 1, the film
thicknesses were measured at randomly selected 100 points by use of the cross-sectional
TEM image of the organic EL element, and the average value thereof was calculated.
[0090] The standard deviation of depths of concavities and convexities of the TiC>2 film as
the auxiliary layer obtained as described above was determined by use of the above
formula (II) based on the analysis image by the atomic force microscope, in the same
manner as the case of the concave-convex pattern layer of the diffraction grating substrate.
The standard deviation (o2) of depths of concavities and convexities of the TiChfilm was
14.2 nm. Then, the shape change ratio (W = (o2 - ol)/al) was obtained by the standard
deviation (a2) of depths of concavities and convexities of the TiChfilm and the standard
deviation (ol) of depths of concavities and convexities of the concave-convex pattern layer
obtained in advance, and the shape change ratio was 27.2%.
[0091] The table of Fig. 12 shows the film thickness of the Ti02 film, the film thickness
of the transparent electrode (ITO), the total film thickness thereof, the optical film
thickness of the total film thickness, and the shape change ratio, of the organic EL element
obtained in this example. The refractive index nl of sol-gel material constituting the
concave-convex pattern layer 12, the refractive index n2 of TiC>2 of the auxiliary layer 14,
and the refractive index n3 of ITO of the first electrode 16 were nl = 1.44, n2 = 2.03 to
2.11, and n3 = 2.03, at a wavelength A, of 550 nm, respectively. Regarding the sol-gel
material constituting the concave-convex pattern layer 12, the reflectance ranging from 230
nm to 800 nm was measured by use of the microscopic reflectance spectral film thickness
monitor FE-3000 (28CWA) produced by OTSUKA ELECTRONICS CO., LTD., and then
the refractive index nl and the film thickness were calculated based on the obtained
spectrum, while the refractive index nl being approximated by Cauchy dispersion formula.
Regarding each of the auxiliary layer 14 and the first electrode 16, the transmittance
ranging from 300 nm to 800 nm was measured by use of the ultraviolet-visible
near-infrared spectral photometer V-570 produced by JASCO corporation, and then the
refractive index n2, the refractive index n3 and the film thickness were calculated based on
the obtained spectrum, while the refractive index n2 and refractive index n3 were each
approximated by Cauchy dispersion formula. As described above, the refractive index nO
of the glass substrate 10 was 1.52, and thus n2 > n3 > nl < nO was satisfied.
[0092] The directivity of light emission of the organic EL element obtained in this
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 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.
[0093]
[Example 2]
An organic EL element was manufactured in the similar manner and conditions as
Example 1, except that the film thickness of the Ti02 film was 41 nm. The standard
deviation of depths of concavities of convexities oftheTi02film was 11.5 nm. Then, the
shape change ratio was obtained by the value of the standard deviation of depths of
concavities and convexities of the Ti02film and the value of the standard deviation of
depths of concavities and convexities of the concave-convex pattern of the diffraction
grating substrate obtained in advance, and the shape change ratio was 41.4%. The table
of Fig. 12 shows the film thickness of the Ti02 film, the film thickness of the transparent
electrode (ITO), the total film thickness thereof, the optical film thickness of the total film
thickness, and the shape change ratio, of the organic EL element obtained in this example.
[0094]
[Example 3]
AO
An organic EL element was manufactured in the similar manner and conditions as
Example 1, except that the film thickness of the TiCh film was 53 nm. The standard
deviation of depths of concavities of convexities of the Ti02 film was 8.0 nm. Then, the
shape change ratio was obtained by the value of the standard deviation of depths of
concavities and convexities of the TiC>2 film and the value of the standard deviation of
depths of concavities and convexities of the concave-convex pattern of the diffraction
grating substrate obtained in advance, and the shape change ratio was 59.3%. The table
of Fig. 12 shows the film thickness of the TiC>2 film, the film thickness of the transparent
electrode (ITO), the total film thickness thereof, the optical film thickness of the total film
thickness, and the shape change ratio, of the organic EL element obtained in this example.
[0095]
[Example 4]
An organic EL element was manufactured in the similar manner and conditions as
Example 1, except that the film thickness of the Ti02 film was changed to 74 nm and that
the film thickness of the transparent electrode (ITO) was changed to 120 nm. The
standard deviation of depths of concavities of convexities of the Ti02 film was 7.0 nm.
Then, the shape change ratio was obtained by the value of the standard deviation of depths
of concavities and convexities of the Ti02film and the value of the standard deviation of
depths of concavities and convexities of the concave-convex pattern of the diffraction
grating substrate obtained in advance, and the shape change ratio was 64.1%. The table
of Fig. 12 shows the film thickness of the Ti02film, the film thickness of the transparent
electrode (ITO), the total film thickness thereof, the optical film thickness of the total film
thickness, and the shape change ratio, of the organic EL element obtained in this example.
[0096]
[Example 5]
An organic EL element was manufactured in the similar manner and conditions as
Example 1, except that a hemispherical lens as the lens layer 22 was provided on the
outside surface of the substrate 10 as depicted in Fig. 2. A hemispherical lens (produced
by Sakai Glass Engineering Co., Ltd.) with a diameter of 10 mm was attached to the
surface of the substrate 10 by use of refractive index liquid (produced by Shimadzu
Corporation) as adhesive. Both of the hemispherical lens and the refractive index liquid
have the refractive index of n = 1.52 (k = 550 nm). The semispherical lens was arranged
so that the center of bottom surface of the semispherical lens overlapped with the center of
a light-emitting pixel (center of the organic EL element). As shown in the table of Fig. 12,
the film thickness of the TiC)2 film, the film thickness of the transparent electrode (ITO),
the total film thickness thereof, the optical film thickness of the total film thickness, and
the shape change ratio, of the organic EL element obtained in this example, were the same
as those of the organic EL element of Example 1.
[0097]
[Example 6]
An organic EL element was manufactured in the similar manner and conditions as
Example 2, except that a hemispherical lens as the lens layer 22 was provided on the
outside surface of the substrate 10 as depicted in Fig. 2. As the hemispherical lens, the
same hemispherical lens as that used in Example 5 was attached to the substrate in the
similar manner as Example 5. As shown in the table of Fig. 12, the film thickness of the
HO2 film, the film thickness of the transparent electrode (ITO), the total film thickness
thereof, the optical film thickness of the total film thickness, and the shape change ratio, of
the organic EL element obtained in this example, were the same as those of the organic EL
element of Example 2.
[0098]
[Example 7]
An organic EL element was manufactured in the similar manner and conditions as
Example 3, except that a hemispherical lens as the lens layer 22 was provided on the
outside surface of the substrate 10 as depicted in Fig. 2. As the hemispherical lens, the
same hemispherical lens as that used in Example 5 was allowed to adhere on the substrate
in the similar manner as Example 5. As shown in the table of Fig. 12, the film thickness
of the Ti02 film, the film thickness of the transparent electrode (ITO), the total film
thickness thereof, the optical film thickness of the total film thickness, and the shape
change ratio, of the organic EL element obtained in this example, were the same as those of
the organic EL element of Example 3.
[0099]
[Comparative Example 1]
An organic EL element was manufactured in the similar manner and conditions as
Example 1, except that the concave-convex structure (concave-convex pattern layer) and
the Ti02 film, those of which constituted the diffracting grating, were not provided. Fig. 7
shows the cross-section structure of an organic EL element 60 manufactured in
Comparative Example 1. The transparent electrode as the first electrode 16 was directly
formed on a flat glass substrate 10, and thus no concave-convex shape appeared in any of
the layers. The table of Fig. 12 shows the film thickness (zero) of the TiC^film, the film
thickness of the transparent electrode (ITO), the total film thickness thereof, the optical
film thickness of the total film thickness, and the shape change ratio, of the organic EL
element obtained in this comparative example.
[0100]
[Comparative Example 2]
An organic EL element was manufactured in the similar manner and conditions as
Example 1, except that the Ti02 film as the auxiliary layer was not provided. Fig. 8
shows the cross-section structure of an organic EL element 70 manufactured in
Comparative Example 2. The concave-convex shape of the concave-convex pattern layer
12 on the diffraction grating substrate was transferred to the first electrode 16, the organic
layer 18, and the second electrode 20 as it is (without change of the shape). The table of
Fig. 12 shows the film thickness (zero) of the Ti02 film, the film thickness of the
transparent electrode (ITO), the total film thickness thereof, the optical film thickness of
the total film thickness, and the shape change ratio, of the organic EL element obtained in
this comparative example.
[0101]
[Comparative Example 3]
An organic EL element was manufactured in the similar manner and conditions as
Example 1, except that the concave-convex pattern layer was not provided. Fig. 9 shows
the cross-section structure of an organic EL element 80 manufactured in Comparative
Example 3. There was no concave-convex shape on the substrate 10, and thus all of the
auxiliary layer 14, the first electrode 16, the organic layer 18, and the second electrode 20
had flat surfaces. The table of Fig. 12 shows the film thickness of the Ti02 film, the film
thickness of the transparent electrode (ITO), the total film thickness thereof, the optical
film thickness of the total film thickness, and the shape change ratio, of the organic EL
element obtained in this comparative example.
[0102]
[Comparative Example 4]
An organic EL element was manufactured in the similar manner and conditions as
Example 1, except that the film thickness of the Ti02 film was 100 nm. The standard
^ 4 -3
deviation of depths of concavities of convexities of the TiC<2 film was 4.9 nm. Then, the
shape change ratio was obtained by the value of the standard deviation of depths of
concavities and convexities of the TCO2 film and the value of the standard deviation of
depths of concavities and convexities of the concave-convex pattern of the diffraction
grating substrate obtained in advance, and the shape change ratio was 75%. As depicted
in Fig. 10, the film thickness of the auxiliary layer 14 of an organic EL element 90
obtained in this comparative example was thicker than those obtained in examples, and
thus the surface of the auxiliary layer 14 had a nearly-flat structure. As a result, the first
electrode 16, the organic layer 18, and the second electrode 20 are considered to also have
planar or flat surfaces. The table of Fig. 12 shows the film thickness of the Ti02 film, the
film thickness of the transparent electrode (ITO), the total film thickness thereof, the
optical film thickness of the total film thickness, and the shape change ratio, of the organic
EL element obtained in this comparative example.
[0103]
[Comparative Example 5]
An organic EL element was manufactured in the similar manner and conditions as
Example 1, except that the film thickness of the Ti02 film was changed to 96 nm and that
the film thickness of the transparent electrode (ITO) was changed to 120 nm. The
standard deviation of depths of concavities of convexities of the TiC^film was 5.9 nm.
Then, the shape change ratio was obtained by the value of the standard deviation of depths
of concavities and convexities of the TiC>2 film and the value of the standard deviation of
depths of concavities and convexities of the concave-convex pattern of the diffraction
grating substrate obtained in advance, and the shape change ratio was 74%. Therefore,
the surface of the TiChfilm is considered to have the shape of concave-convex surface as
depicted in Fig. 10, similar to Comparative Example 4. The table of Fig. 12 shows the
film thickness of the Ti02 film, the film thickness of the transparent electrode (ITO), the
total film thickness thereof, the optical film thickness of the total film thickness, and the
shape change ratio, of the organic EL element obtained in this comparative example.
[0104]
[Comparative Example 6]
An organic EL element was manufactured in the similar manner and conditions as
Comparative Example 1, except that a hemispherical lens as the lens layer 22 was provided
on the outside surface of the substrate 10 as depicted in Fig. 2. As the hemispherical lens,
*%4
the same hemispherical lens as that used in Example 5 was attached to the substrate in the
similar manner as Example 5. As shown in the table of Fig. 12, the film thickness of the
Ti02 film, the film thickness of the transparent electrode (ITO), the total film thickness
thereof, the optical film thickness of the total film thickness, and the shape change ratio, of
the organic EL element obtained in this Comparative Example, were the same as those of
the organic EL element of Comparative Example 1.
[0105]
[Comparative Example 7]
An organic EL element was manufactured in the similar manner and conditions as
Comparative Example 2, except that a hemispherical lens as the lens layer 22 was provided
on the outside surface of the substrate 10 as depicted in Fig. 2. As the hemispherical lens,
the same hemispherical lens as that used in Example 5 was attached to the substrate in the
similar manner as Example 5. As shown in the table of Fig. 12, the film thickness of the
Ti02 film, the film thickness of the transparent electrode (ITO), the total film thickness
thereof, the optical film thickness of the total film thickness, and the shape change ratio, of
the organic EL element obtained in this Comparative Example, were the same as those of
the organic EL element of Comparative Example 2.
[0106]
[Relation between Ti02 film and shape change ratio]
The diffraction grating substrate obtained in Example 1 was coated with the TiCh
film having various film thicknesses. Then, the standard deviation o2 of depths of each
of the Ti02 films having one of the various film thicknesses was obtained in the similar
manner as Example 1. The graph of Fig. 5 shows the change of the standard deviationa2
of depths of the TiCh film with respect to the thickness of the TiCh film. The results
obtained in Examples 1 to 4 and Comparative Examples 1 to 5 are also included in the plot
of the graph of Fig. 5. Further, the ratio of shape change (the change ratio of the standard
deviation o2 of depths of the TiC^film with respect to the standard deviation al of depths
of the concave-convex pattern layer constituting the diffraction grating) was obtained in
the similar manner as Example 1 based on the value of film thickness of each of the Ti02
films having one of various film thicknesses. The graph of Fig. 6 shows the change in the
shape change ratio with respect to the film thickness of the TiCh film, and the following
facts are understood therefrom. That is, in a case that the film thickness of the TiC"2 film
is not more than 10 nm, the shape of the TiC"2 film follows the concave-convex shape of
the diffraction grating substrate. The shape change ratio of the Ti02 film is increased as
the film thickness of the TiC«2 film is increased, and thus the TiC«2 film is gradually
planarized or flattened.
[0107]
[Evaluation of light emission efficiency of organic EL element]
The light emission efficiency of the organic EL element obtained in each of
Examples 1 to 7 and Comparative Examples 1 to 7 was measured by the following method.
That is, 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 values of the applied
voltage V, the current I, and the total luminous flux amount L, a luminance value L' was
calculated. Here, the following calculation formula (Fl) was used to calculate the current
efficiency of the organic EL element:
Current efficiency = (LVI) x S • (F1)
In the above formula, 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 (F2) was used:
L' = L/n/S (F2)
[0108] The table of Fig 12 shows the current efficiency of the organic EL element
manufactured in each of Examples 1 to 7 and Comparative Examples 1 to 7 at a luminance
of 10000 cd/m2. The current efficiency of the organic EL element manufactured in each
of Examples 1 to 3 was not less than 70 cd/A. The current efficiency of the organic EL
element of Example 4 was lower than the current efficiency of the organic EL element
manufactured in each of Examples 1 to 3. The reason thereof is considered as follows.
That is, the film thickness of the transparent electrode of the organic EL element
manufactured in Example 4 was thicker than that of the organic EL element manufactured
in each of Examples 1 to 3, and the total film thickness of the auxiliary layer and the
transparent electrode in the organic EL element manufactured in Example 4 was thicker
than that of the organic EL element manufactured in each of Examples 1 to 3. As a result,
regarding the organic Element of Example 4, the light generated in the organic layer was
4-6
more likely to stationary stand in the two layers of the auxiliary layer and the transparent
electrode. Further, the reason why the organic EL elements manufactured in Comparative
Examples 1 and 3 both had a low current efficiency is as follows. That is, since there was
no concave-convex layer constituting the diffraction grating in the organic EL element
manufactured in each of Comparative Examples 1 and 3, the light was reflected at the
interference between the substrate and an upper layer of the substrate and the light was not
extracted from the outside surface of the substrate sufficiently. Further, the reason why
the organic EL elements manufactured in Comparative Examples 4 and 5 both had a low
current efficiency is as follows. That is, even though the organic EL element
manufactured in each of Comparative Examples 4 and 5 had the auxiliary layer and the
concave-convex structure constituting the diffraction grating, the shape change ratio
exceeded 70%, and thus the second concave-convex shape of the auxiliary layer was
planarized or flattened too much.
[0109] Regarding the organic EL element manufactured in each of Examples 5 to 7 and
Comparative Examples 6 and 7, the following fact has been found. That is, the
hemispherical lens was provided in the substrate on the light-emitting surface side, and
thus the current efficiency was improved greatly (60% or more) in each of the examples.
[0110]
[Evaluation of yield of organic EL element]
The voltage was continuously applied on the organic EL element manufactured in
each of Examples 1 to 7 and Comparative Examples 1 to 7 so that the organic EL element
was driven with a constant current in which the current density flowing through the organic
EL element was 20 mA/cm2. Then, the number of elements which leaked in 24 hours and
stopped light-emitting was counted, and yield (%) was evaluated based on the obtained
result. The light-emitting pixel of the organic EL element had 3 mm in length and 3 mm
in width. The organic EL element manufactured in each of Examples 1 to 7 and
Comparative Examples 1 to 7 was sealed with UV curable resin and cap glass in nitrogen
atmosphere, and the organic EL element was taken out of the nitrogen atmosphere and put
into the atmosphere. Then, the organic EL element was evaluated in a room at a
temperature of 25 degrees Celsius and humidity of 45%. The luminance was measured
once every 2 minutes. Each of the results is shown in the table of Fig. 12. The yield of
the organic EL element in each of Examples 1 to 7 was 90% and the yield of the organic
EL element in each of Comparative Examples 2 and 7 was 70%. It was confirmed that
many cracks occurred in the auxiliary layer (Ti02) of the organic EL element of
Comparative Example 5. The reason thereof is considered that the total film thickness of
the auxiliary layer and the transparent electrode in the organic EL element of Comparative
Example 5 exceeded 200 nm.
[0111] In the organic EL element manufactured in each of Examples, both the
concave-convex pattern layer and the auxiliary layer stacked thereon are made of the
sol-gel material, and thus the adhesion property between the auxiliary layer and the
concave-convex pattern is good. Further, heat resistance, mechanical strength, and
chemical resistance are superior in the organic EL element manufactured in each of
Examples. Therefore, in the organic EL manufacturing process, the organic EL element
manufactured in each of Examples can satisfactorily withstand a film formation step
performed under a high temperature atmosphere, UV/O3 ozone cleaning, brushing, a
cleaning step using various cleaning liquids such as acid and alkali solvents, and a
patterning step using a developer and an etching liquid.
[0112] In a case that the organic EL element manufactured in each of Examples 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. Further, in a case that the
curable resin as described above is kept for a long period under 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 and/or 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 with the concave-convex pattern layer manufactured by
use of the sol-gel material is less likely to deteriorate.
[0113] In the above description, the present invention was explained by using examples.
The present invention, however, is not limited to the above examples, and can be
appropriately modified within the range of technical ideas described in the claims.
Industrial Applicability
[0114] The organic EL element of the present invention is capable of preventing the
occurrence of leak current effectively while maintaining a good light extraction efficiency.
Thus, the organic EL element of the present invention is suitable for various uses such as a
display and an illumination device which are required to have uniform lighting, and further
the organic EL element of the present invention contributes to energy conservation.
A-2
Reference Signs List:
[0115]
10: substrate; 12: concave-convex pattern layer; 14: auxiliary layer; 16: first electrode; 18:
organic layer; 20: second electrode; 22: lens layer; 30: organic EL element; 42 coating film
(sol-gel material layer); 122: pressing roll; 123: peeling roll

We claim:
1. An organic EL element, comprising:
a concave-convex pattern layer having a first concave-convex shape, a
first electrode, an organic layer, and a second electrode layer formed on a substrate in this
order; and
an auxiliary layer provided between the concave-convex pattern layer and
the first electrode,
wherein a surface of the auxiliary tlayer on a side of the first electrode has
a second concave-convex shape; and
a change ratio of a standard deviation of depths of the second
concave-convex shape with respect to a standard deviation of depths of the first
concave-convex shape is 70% or less.
2. The organic EL element according to claim 1, wherein the change ratio of
the standard deviation of the depths of the second concave-convex shape with respect to
the standard deviation of the depths of the first concave-convex shape is in a range of 20%
to 70%.
3. The organic EL element according to claim 1 or 2, wherein a total optical
film thickness of the auxiliary layer and first electrode is in a range of 160 nm to 400 nm.
4. The organic EL element according to any one of claims 1 to 3, wherein
the first electrode is made of ITO and has a film thickness of 80 nm or more.
5. The organic EL element according to any one of claims 1 to 4, wherein
the concave-convex pattern layer and the auxiliary layer are made of an inorganic material.
6. The organic EL element according to any one of claims 1 to 5, wherein
the concave-convex pattern layer is made of silica.
7. The organic EL element according to any one of claims 1 to 6, wherein,
in a case that refractive indexes of the substrate, the concave-convex pattern layer, the
auxiliary layer, and the first electrode are represented by nO, nl, n2, and n3, respectively,
the following relation:
n2 > n3 > nl < 0 is satisfied.
8. The organic EL element according to any one of claims 1 to 7, wherein
the concave-convex pattern layer includes an irregular concave-convex pattern in which
orientations of concavities and convexities have no directivity.
9. The organic EL element according to any one of claims 1 to 8, wherein an
average pitch of concavities and convexities of the concave-convex pattern layer is in a
range of 100 nm to 1500 nm and an average height of concavities and convexities of the
concave-convex pattern layer is in a range of 20 nm to 200 nm.
10. A method for manufacturing the organic EL element as defined in any
one of claims 1 to 9, comprising:
forming the concave-convex pattern layer, the auxiliary layer, the first
electrode, the organic layer, and the second electrode layer on the substrate in this order;
and
forming the auxiliary layer to make the surface of the auxiliary layer on
the side of the first electrode have the second concave-convex shape,
wherein the change ratio of the standard deviation of depths of the second
concave-convex shape with respect to the standard deviation of depths of the first
concave-convex shape is 70% or less.
11. The method for manufacturing the organic EL element according to claim
10, wherein the concave-convex pattern layer is formed by coating the substrate with a
sol-gel material and then pressing a mold against the substrate.