JP6155566B2 - Laminated substrate for organic LED element, laminated substrate with transparent electrode, and organic LED element - Google Patents

Description

  The present invention relates to a laminated substrate for an organic LED element and an organic LED element.

  The organic LED element has a transparent substrate, a transparent electrode, an organic layer, and a reflective electrode in this order. The light emitted from the organic layer passes through the transparent electrode and the transparent substrate, and is emitted to the outside from the extraction surface of the transparent substrate. Light incident from the transparent electrode to the transparent substrate having a lower refractive index than the transparent electrode at an incident angle greater than the critical angle is totally reflected at the interface between the transparent electrode and the transparent substrate. In addition, light incident from a transparent substrate into air having a refractive index lower than that of the transparent substrate at an incident angle greater than the critical angle is totally reflected at the interface between the transparent substrate and air. The light is converted into heat or emitted from the side surface of the organic LED element while reciprocating between the light extraction surface and the reflective electrode many times.

  Therefore, in order to improve the light extraction efficiency, a technique for providing an uneven layer between the transparent electrode and the transparent substrate has been proposed (see, for example, Patent Document 1). The uneven layer forms a transmission type diffraction grating. Most of the light incident on the diffraction grating from the transparent electrode is transmitted through the diffraction grating, and the rest is reflected by the diffraction grating.

  Since the light reflected by the diffraction grating is reflected at a reflection angle smaller than the incident angle due to the interference effect of the diffraction grating, most of the light is transmitted through the diffraction grating when it is reflected by the reflective electrode and reenters the diffraction grating.

  The light that passes through the diffraction grating is divided into zero-order diffracted light, first-order diffracted light, second-order diffracted light, and the like, and enters the light extraction surface of the transparent substrate. Light whose incident angle is less than the critical angle is emitted to the outside from the light extraction surface. On the other hand, most of the light whose incident angle is greater than or equal to the critical angle is totally reflected by the light extraction surface, and then passes through the diffraction grating during one or more round trips between the light extraction surface and the reflective electrode. Thus, the incident angle is changed to an incident angle less than the critical angle, and finally emitted from the light extraction surface.

Japanese Patent Laid-Open No. 11-283951

  In the conventional technique, sufficient light extraction efficiency cannot be obtained.

  This invention is made | formed in view of the said subject, Comprising: It aims at provision of the laminated substrate for organic LED elements with high light extraction efficiency.

In order to solve the above problems , a multilayer substrate for an organic LED element according to an aspect of the present invention is provided.
Comprising a transparent substrate, a concavo-convex layer provided on the transparent substrate, and a planarization layer provided on the concavo-convex surface of the concavo-convex layer, and emitting light of the organic layer through the planarization layer and the concavo-convex layer, For taking out from the surface opposite to the concavo-convex layer side in the transparent substrate,
The uneven layer, the substrate, and a light scattering material dispersed in the base material seen including, to form a diffraction grating.

  ADVANTAGE OF THE INVENTION According to this invention, the laminated substrate for organic LED elements with high light extraction efficiency is provided.

Sectional drawing which shows the organic LED element by 1st Embodiment of this invention. It is a figure for demonstrating that the total reflection of light is reduced with the transmission type diffraction grating of FIG. Rayleigh scattering concept Conceptual diagram of Mie scattering Simulation model for confirming that the light direction is aligned to the front direction by Mie scattering Diagram showing simulation results Sectional drawing which shows the organic LED element by the 1st modification of 1st Embodiment. Sectional drawing which shows the organic LED element by the 2nd modification of 1st Embodiment. Sectional drawing which shows the organic LED element by 2nd Embodiment of this invention. The figure for demonstrating that the total reflection of light is reduced by the prism of FIG. Sectional drawing which shows the organic LED element by the 1st modification of 2nd Embodiment. Sectional drawing which shows the organic LED element by the 2nd modification of 2nd Embodiment. Sectional drawing which shows the organic LED element by 3rd Embodiment of this invention. The figure for demonstrating that the total reflection of light is reduced with the lens of FIG. Sectional drawing which shows the organic LED element by the 1st modification of 3rd Embodiment. Sectional drawing which shows the organic LED element by the 2nd modification of 3rd Embodiment. Sectional drawing which shows the organic LED element by 4th Embodiment of this invention. Explanatory drawing of light transmission by the moth-eye structure of FIG. Sectional drawing which shows the organic LED element by the 1st modification of 4th Embodiment. Sectional drawing which shows the organic LED element by the 2nd modification of 4th Embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof is omitted.

[First Embodiment]
FIG. 1 is a cross-sectional view illustrating an organic LED element according to a first embodiment of the present invention. In FIG. 1, the unevenness of the uneven layer 30 is exaggerated for convenience.

  The organic LED element 10 is a bottom emission type, and includes a transparent substrate 20, an uneven layer 30, a planarization layer 40, a transparent electrode 50, an organic layer 60, and a reflective electrode 70 in this order. The laminated substrate 11 is composed of the transparent substrate 20, the uneven layer 30, and the planarizing layer 40, and the light emitting element 12 is composed of the transparent electrode 50, the organic layer 60, the reflective electrode 70, and the like. In the case of illumination, one light emitting element 12 may be formed on the planarization layer 40. In the case of image display, the light emitting element 12 is provided for each pixel, and the plurality of light emitting elements 12 are arranged on the planarization layer 40.

  The light emitted from the organic layer 60 is transmitted through the transparent electrode 50, the planarizing layer 40, the concavo-convex layer 30, and the transparent substrate 20, and is emitted to the outside from the light extraction surface 21 of the transparent substrate 20. The light extraction surface 21 is a surface on the opposite side to the uneven layer 30 side in the transparent substrate 20.

  In the present embodiment, the uneven layer 30 forms the diffraction grating 31. The diffraction grating 31 is provided on the planarization layer 40 side. In the following description, the incident angle and the reflection angle at the diffraction grating 31 mean an angle formed by a direction perpendicular to the light extraction surface 21 (hereinafter referred to as “front direction”) and the light traveling direction.

(Transparent substrate)
The transparent substrate 20 may be a glass substrate or a resin substrate, for example. The transparent substrate 20 is preferably a glass substrate with high moisture resistance. Examples of the glass of the glass substrate include alkali glass, borosilicate glass, and quartz glass. In general, alkali silicate glass such as soda lime glass is used. The refractive index of glass is, for example, 1.4 to 1.9. The refractive index of the transparent substrate 20 is preferably equal to or lower than the refractive index of the transparent electrode 50. Examples of the resin for the resin substrate include an acrylic resin and a polycarbonate resin. In order to improve the moisture resistance of the resin substrate, a moisture barrier layer may be provided on the resin substrate. The moisture resistant barrier layer is formed of a metal oxide such as silicon oxide, a metal nitride such as silicon nitride, diamond-like carbon (DLC), glass, or the like.

  In this specification, “refractive index” means a refractive index measured at 25 ° C. using a He lamp d-line (wavelength: 587.6 nm). The refractive index is measured with an Abbe refractometer.

  The thickness of the transparent substrate 20 is, for example, 0.001 mm to 2.0 mm. Preferably it is 0.001 mm-1.0 mm.

(Transparent electrode)
The transparent electrode 50 is an anode that supplies holes to the organic layer 60. The material of the transparent electrode 50 includes ITO (Indium Tin Oxide), SnO ₂ , ZnO, IZO (Indium Zinc Oxide), AZO (ZnO—Al ₂ O ₃ : zinc oxide doped with aluminum), GZO (ZnO— Ga ₂ O ₃ : zinc oxide doped with gallium), Nb-doped TiO ₂ , Ta-doped TiO _{2 and the} like. The refractive index of these materials is, for example, 1.7 to 2.2. The transparent electrode 50 may be a laminated film formed using two or more materials.

  The thickness of the transparent electrode 50 is, for example, 50 nm or more. If it is less than 50 nm, the electrical resistance becomes high.

(Organic layer)
The organic layer 60 may have a general configuration and includes at least a light emitting layer, and includes a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer as necessary. For example, the organic layer 60 includes a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer in this order from the anode side.

  The hole injection layer is formed of a material having a small difference in ionization potential from the anode. As the polymer, polyethylenedioxythiophene (PEDOT: PSS) doped with polystyrene sulfonic acid (PSS) is used. For low molecules, phthalocyanine-based copper phthalocyanine (CuPc) or the like is used.

  The hole transport layer transports holes injected from the hole injection layer to the light emitting layer. Examples of the material for the hole transport layer include a triphenylamine derivative, N, N′-bis (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPD). ), N, N′-diphenyl-N, N′-bis [N-phenyl-N- (2-naphthyl) -4′-aminobiphenyl-4-yl] -1,1′-biphenyl-4,4 ′ -Diamine (NPTE), 1,1-bis [(di-4-tolylamino) phenyl] cyclohexane (HTM2) and N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1 ' -Diphenyl-4,4'-diamine (TPD) or the like is used. The thickness of the hole transport layer is preferably 10 nm to 150 nm. The thinner the thickness is, the lower the voltage can be. However, the thickness is preferably 10 nm to 150 nm from the problem of short circuit between electrodes.

  The light emitting layer emits light with energy generated by recombination of electrons and holes injected from the anode and the cathode. Doping of the luminescent dye into the host material in the luminescent layer obtains high luminous efficiency and converts the emission wavelength. Organic materials for the light emitting layer include low molecular weight materials and high molecular weight materials. Further, it is classified into a fluorescent material and a phosphorescent material according to the light emission mechanism. Examples of the organic material for the light emitting layer include tris (8-quinolinolato) aluminum complex (Alq3), bis (8-hydroxy) quinaldine aluminum phenoxide (Alq′2OPh), and bis (8-hydroxy) quinaldine aluminum-2. , 5-dimethylphenoxide (BAlq), mono (2,2,6,6-tetramethyl-3,5-heptanedionate) lithium complex (Liq), mono (8-quinolinolato) sodium complex (Naq), mono (2,2,6,6-tetramethyl-3,5-heptanedionate) lithium complex, mono (2,2,6,6-tetramethyl-3,5-heptanedionate) sodium complex and bis (8 -Quinolinolate) metal complexes of quinoline derivatives such as calcium complexes (Caq2), tetraphenylbutadiene, E D Lucina click polyhedrin (QD), anthracene, perylene and coronene, and the like. As the host material, a quinolinolate complex is preferable, and an aluminum complex having 8-quinolinol and a derivative thereof as a ligand is particularly preferable.

  The electron transport layer transports electrons injected from the electrode. Examples of the material for the electron transport layer include quinolinol aluminum complex (Alq3), oxadiazole derivatives (for example, 2,5-bis (1-naphthyl) -1,3,4-oxadiazole (BND) and 2- (4-t-butylphenyl) -5- (4-biphenyl) -1,3,4-oxadiazole (PBD) etc.), triazole derivatives, bathophenanthroline derivatives, silole derivatives and the like are used.

  The electron injection layer may be a layer obtained by doping an alkali metal such as lithium (Li) or cesium (Cs) on the cathode surface, for example.

(Reflective electrode)
The reflective electrode 70 is a cathode that supplies electrons to the organic layer 60. The reflective electrode 70 reflects the light emitted from the organic layer 60 toward the organic layer 60 side.

The reflective electrode 70 includes at least one of an alkali metal (for example, Al), an alkaline earth metal (for example, Mg), and a metal of Group 3 of the periodic table. For example, the reflective electrode 70 may be a MgAg co-deposited film, a laminated film obtained by depositing Al on a LiF or Li ₂ O thin film deposited film, or an aluminum (Al) layer on an alkaline earth metal (eg, Ca, Ba) layer. It may be a laminated film in which are laminated.

(Uneven layer)
The uneven layer 30 is formed on the transparent substrate 20 by, for example, an imprint method. In the imprint method, a layer of a molding material is sandwiched between the transparent substrate 20 and a mold, and the uneven layer 30 to which the uneven pattern of the mold is transferred is formed on the transparent substrate 20. The concavo-convex pattern of the concavo-convex layer 30 is a pattern in which the concavo-convex pattern of the mold is substantially inverted.

  When the transparent substrate 20 is a glass substrate, the glass substrate may be subjected to a surface treatment in advance in order to enhance the adhesion between the glass and the molding material. Examples of the surface treatment include primer treatment, ozone treatment, plasma etching treatment, and the like. As the primer, a silane coupling agent, silazane or the like is used.

  In the photoimprint method, the concave / convex layer 30 is formed by pressing a concave / convex pattern of a mold against the surface of a layer of a molding material containing a photocurable resin, irradiating light, and solidifying (curing) the layer of the molding material.

  Examples of the light that cures the photocurable resin include ultraviolet light, visible light, and infrared light. Examples of the ultraviolet light source include ultraviolet fluorescent lamps, ultraviolet LEDs, low-pressure mercury lamps, high-pressure mercury lamps, ultrahigh-pressure mercury lamps, xenon lamps, and carbon arc lamps. As a light source for visible light, a visible light fluorescent lamp, a visible light incandescent lamp, a visible light LED, or the like is used.

  In the optical imprint method, molding at room temperature is possible, distortion due to a difference in linear expansion coefficient between the mold and the transparent substrate 20 hardly occurs, and transfer accuracy is good. Note that the layer of the molding material may be heated to accelerate the curing reaction.

  On the other hand, in the thermal imprint method, a molding material layer containing a thermoplastic resin is softened by heating, the mold is pressed against the surface of the softened molding material layer, and the molding material layer is cooled and solidified, thereby causing unevenness. Layer 30 is formed.

  As the heating source, a light source (for example, a halogen lamp or a laser) that radiates heating light, a heater, or the like is used. The heating temperature is equal to or higher than the glass transition temperature of the thermoplastic resin.

  The layer of a molding material contains the below-mentioned light-scattering material as needed.

  In addition, although the uneven | corrugated layer 30 of this embodiment is formed by the imprint method, you may form by the photolithographic method, EB drawing method, interference exposure method, etc.

  The uneven layer 30 forms a transmission type diffraction grating 31. The diffraction grating 31 may be a two-dimensional diffraction grating. The diffraction grating 31 has a plurality of convex portions, and the bottom surfaces of the plurality of convex portions are arranged on the same plane. The plurality of convex portions are periodically arranged, for example, in a regular hexagonal lattice shape, a quasi-hexagonal lattice shape, a regular tetragonal lattice shape, or a quasi-tetragonal lattice shape. The pitch P1 between the nearest protrusions is about 1 to several times the wavelength of visible light (300 nm <P1 ≦ 5 μm), and the refractive index of the uneven layer 30, the refractive index of the planarizing layer 40, and the height of the protrusions Although it is designed appropriately according to the height H1, etc., it is 500 nm, for example. The height H1 of the convex part is 10 nm or more and 5 μm or less. When the thickness is 10 nm or more, sufficient diffraction efficiency is easily obtained. When the thickness is 5 μm or less, it is easy to produce the uneven layer. The shape of the convex portion may be various, and examples thereof include a cone shape, a truncated cone shape, a pyramid shape (for example, a quadrangular pyramid shape and a triangular pyramid shape), a truncated pyramid shape, a bell shape, a cylindrical shape, and a prism shape. . The diffraction grating 31 may be a one-dimensional diffraction grating.

  The transmissive diffraction grating 31 transmits light incident at various incident angles from the planarizing layer 40 to the concave-convex layer 30, and aligns the direction of most transmitted light in the front direction. Therefore, total reflection at the interface such as the light extraction surface 21 can be suppressed, and the light extraction efficiency can be improved.

  The transmissive diffraction grating 31 plays a role of suppressing total reflection of light when entering the concave / convex layer 30 from the planarizing layer 40.

  FIG. 2 is a diagram for explaining that the total reflection of light is reduced by the transmission type diffraction grating of FIG. 2, illustration of the light emitting element 12 and the light-scattering materials 34 and 44 is abbreviate | omitted for convenience.

  In general, when the interface between the adjacent high refractive index layer and the low refractive index layer is flat, light incident from the high refractive index layer to the low refractive index layer at an incident angle greater than the critical angle is totally reflected. End up.

  In this embodiment, the interface between the planarization layer 40 as the high refractive index layer and the uneven layer 30 as the low refractive index layer has a fine uneven structure, and the uneven layer 30 forms a transmission type diffraction grating 31. To do. Therefore, most of the light that is totally reflected when the interface is flat is divided into zero-order diffracted light R0, first-order diffracted light R1, second-order diffracted light R2, etc. as shown in FIG. And propagates in the concavo-convex portion 30. Therefore, it is possible to suppress the total reflection of light when entering the concavo-convex layer 30 from the planarizing layer 40.

  In addition, when the interface is flat, the pitch P1 and the height H1 of the convex portions of the diffraction grating 31 are optimized so that most of the light transmitted through the interface without being totally reflected at the interface is transmitted through the diffraction grating 31. May be. In addition, since the light reflected by the diffraction grating 31 is reflected at a reflection angle smaller than the incident angle due to the interference effect by the diffraction grating 31, most of the light is reflected by the reflection electrode 70 and incident on the diffraction grating 31 again. The light passes through the diffraction grating 31.

  By the way, in the transmission type diffraction grating 31, the intensity of the light transmitted through the diffraction grating 31 is angle-dependent due to the interference of light, and the intensity of the transmitted light is increased at a plurality of specific angles. Further, the angle at which the intensity of the transmitted light is increased is different for each wavelength of the transmitted light.

  Therefore, as shown in FIG. 1, the uneven layer 30 may include a base material 33 such as a resin and a light scattering material 34 dispersed in the base material 33. The light scattering material 34 scatters the light propagating through the concavo-convex layer 30, thereby reducing the angle dependency of the light intensity and reducing the angle dependency of the light color (wavelength).

  In order to suppress reflection at the interface between the base material 33 and the transparent substrate 20, the base material 33 is preferably made of a material having a refractive index difference from the transparent substrate 20 of 0.3 or less. In the case of optical nanoimprint, for example, a silsesquioxane resin or a polyimide resin is used as the photocurable resin that forms the base material 33. Silsesquioxane resins and polyimide resins are also excellent in heat resistance. In the case of thermal nanoimprint, for example, (meth) acrylic resin, polyester resin, polyolefin resin, cellulose resin, polyamide resin, polyepoxy resin, etc. are suitable as the thermoplastic resin forming the base material 33. . The refractive index of the base material 33 may be higher or lower than the refractive index of the transparent substrate 20, but is preferably equal to or lower than the refractive index of the transparent substrate 20.

The light scattering material 34 has a refractive index different from that of the base material 33 and is composed of air having a lower refractive index than the base material 33, a metal oxide having a higher refractive index than the base material 33, or both. Examples of the metal oxide include zirconia (ZrO ₂ ), titania (TiO ₂ ), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), tin oxide (SnO ₂ ), and the like.

  As the average particle size of the metal oxide particles, the peak value of the particle size distribution measured by the dynamic light scattering method is used. When the light scattering material 34 is air, for example, the cross section of the concavo-convex layer 30 is observed with a scanning electron microscope (SEM), 10 random light scattering materials included in the field of view are extracted, and the diameters thereof are measured. And can be obtained by averaging.

  The average sphere equivalent diameter (average particle diameter) of the light scattering material 34 is preferably 300 nm to 10 μm. When the average equivalent sphere diameter of the light scattering material 34 exceeds 10 μm, the light scattering material 34 is difficult to disperse in the base material 33 and tends to be unevenly distributed. On the other hand, if the average sphere equivalent diameter of the light scattering material 34 is less than 300 nm, it is too shorter than the wavelength of visible light, so Rayleigh scattering (see FIG. 3) becomes dominant and backscattering becomes strong. Efficiency is reduced.

  FIG. 3 is a conceptual diagram of Rayleigh scattering. FIG. 4 is a conceptual diagram of Mie scattering. 3 and 4, white circles M represent scattered particles, thick lines L1 represent incident light, thin lines L2 represent scattered light due to Rayleigh scattering, and thin lines L3 represent scattered light due to Mie scattering. The arrow directions of the thin lines L2 and L3 indicate the traveling direction of the scattered light, and the lengths of the thin lines L2 and L3 indicate the intensity of the scattered light.

  Since the average spherical equivalent diameter of the light scattering material 34 of the present embodiment is 300 nm to 10 μm, which is equal to or greater than the wavelength of visible light, Mie scattering (see FIG. 4) becomes dominant and forward scattering becomes strong. When the average sphere equivalent diameter of the light scattering material 34 is 300 nm to 10 μm, the direction of light propagating in the uneven layer 30 can be aligned in the front direction.

  FIG. 5 is a model diagram of a simulation for confirming that the light directions are aligned in the front direction by Mie scattering. FIG. 6 is a diagram showing a result of the simulation, and is a diagram showing a relationship between the light intensity and the propagation direction. In FIG. 6, a solid line N1 indicates the relationship between the intensity of light emitted forward from the light scattering layer and the propagation direction, and a broken line N2 indicates the relationship between the intensity of light incident on the light scattering layer and the propagation direction. N3 represents the relationship between the intensity of light emitted backward from the light scattering layer and the propagation direction. In FIG. 6, the distance from the origin represents the light intensity, and the angle represents the light propagation direction. The light propagation direction is represented by an angle between the front direction and 0 °.

  In the simulation, as shown in FIG. 5, a light scattering layer in which a light scattering material 34A (particle size 500 nm, refractive index 1.45) is dispersed in the base material 33A in the middle of the base material 33A (refractive index 2.0). 30A (layer thickness: 1 μm) was provided, and the angle dependency of the intensity of light emitted from the light scattering layer 30A was determined by a ray tracing method (software name: “LightTools”, manufactured by CYBERNET). The volume ratio of the light scattering material 34A in the light scattering layer 30A was 60%. Further, a boundary surface having a light absorption rate of 100% was set at the upper end in the drawing and the lower end in the drawing of the base material 33A.

  As shown in FIG. 6, the direction of light can be aligned in the front direction by Mie scattering, and the intensity of light within a range of −42 ° to 42 ° can be increased. The critical angle at the interface (light extraction surface 21) between the glass substrate (refractive index 1.5) and air (refractive index 1.0), which is the transparent substrate 20, is about 42 °.

  The direction of light is aligned in the front direction by Mie scattering. (1) The forward scattering is dominant, and (2) the distance required for the light scattering layer 30A to pass through as the direction of the incident light is inclined from the front direction. This is due to the increase in the number of light scattering times.

  Since the incident light whose direction is originally in the front direction has a small number of scatterings and the forward scattering is dominant, the direction of the incident light hardly changes while propagating in the light scattering layer 30A. On the other hand, since the incident light having the oblique direction has a large number of scattering times, the direction gradually changes to the front direction while propagating through the light scattering layer 30A. Therefore, the light direction is entirely aligned in the front direction due to Mie scattering.

  The refractive index of the base material 43, the refractive index of the light scattering material 44, the average sphere equivalent diameter, the volume ratio, and the thickness of the uneven layer 30 are appropriately designed.

(Flattening layer)
The planarization layer 40 is provided on the uneven layer 30 and absorbs the unevenness of the uneven layer 30. The transparent electrode 50, the organic layer 60, and the reflective electrode 70 provided on the flat surface of the flattening layer 40 can exhibit the performance as designed.

  The planarization layer 40 is formed on the concavo-convex surface of the concavo-convex layer 30 by, for example, a wet coat method. Before the planarization layer 40 is formed, a step of heat treating the uneven layer 30 may be performed. It is possible to improve the polymerization rate of the resin of the uneven layer 30 and to remove the birefringence of the uneven layer 30.

  In the wet coating method, the planarizing layer 40 is formed by applying a fluid resin on the uneven layer 30 and solidifying it. A light scattering material is added to the flowable resin as necessary. Examples of the wet coating method include spin coating, spray coating, roll coating, and die coating.

  The planarization layer 40 may include a 30 base material 43 such as a resin and a light scattering material 44 dispersed in the base material 43. Similar to the light scattering material 34 of the concavo-convex layer 30, the light scattering material 44 aligns the direction of light propagating in the planarization layer 40 in the front direction, and changes the direction of light incident on the diffraction grating 31 from the planarization layer 40. Align in the front direction.

  Generally, as the direction of light incident on the diffraction grating is aligned in the front direction, the direction of light transmitted through the diffraction grating is more easily aligned in the front direction.

  In the present embodiment, since the light scattering material 44 in the planarization layer 40 aligns the direction of light incident on the diffraction grating 31 from the planarization layer 40 with the front direction, the direction of the light transmitted through the diffraction grating 31 is the front direction. It is easy to align and light extraction efficiency can be improved.

  In order to suppress reflection at the interface between the base material 43 and the transparent electrode 50, the base material 43 is preferably made of a material having a refractive index difference from the transparent electrode 50 of 0.3 or less. In the case of optical nanoimprint, for example, a silsesquioxane resin or a polyimide resin is used as the photocurable resin that forms the base material 43. Silsesquioxane resins and polyimide resins are also excellent in heat resistance. In the case of thermal nanoimprinting, for example, (meth) acrylic resin, polyester resin, polyolefin resin, cellulose resin, polyamide resin, polyepoxy resin, and the like are suitable as the thermoplastic resin forming the base material 43. . The base material 43 may include inorganic nanoparticles having a size that does not scatter light in order to adjust the refractive index. The particle size of the inorganic nanoparticles is preferably 1 nm to 100 nm, more preferably 1 nm to 50 nm. When the particle size is less than 1 nm, the crystallinity becomes poor, and it becomes difficult to express particle characteristics such as refractive index. On the other hand, when the particle diameter exceeds 100 nm, the influence of Rayleigh scattering starts to appear, the backscattering component increases, and the light extraction efficiency decreases. The refractive index of the base material 43 may be higher or lower than the refractive index of the transparent electrode 50, but is preferably equal to or lower than the refractive index of the transparent electrode 50.

  The base material 43 has a refractive index different from that of the base material 33 of the uneven layer 30. Since the base material 43 is in contact with the transparent electrode 50 having a higher refractive index than the transparent substrate 20, it is preferable that the base material 43 has a higher refractive index than the base material 33 of the uneven layer 30 in contact with the transparent substrate 20.

The light scattering material 44 has a refractive index different from that of the base material 43 and is composed of air having a lower refractive index than the base material 43, a metal oxide having a higher refractive index than the base material 43, or both. Examples of the metal oxide include zirconia (ZrO ₂ ), titania (TiO ₂ ), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), tin oxide (SnO ₂ ), and the like.

  The average sphere equivalent diameter (average particle diameter) of the light scattering material 44 is preferably 300 nm to 10 μm. When the average sphere equivalent diameter of the light scattering material 44 exceeds 10 μm, the light scattering material 44 is difficult to disperse in the base material 43 and is likely to be unevenly distributed. If the average equivalent sphere diameter of the light scattering material 44 is less than 300 nm, it is too short than the wavelength of visible light, so Rayleigh scattering (see FIG. 3) becomes dominant and backscattering becomes strong, so that the light extraction efficiency is improved. descend.

  When the average spherical equivalent diameter of the light scattering material 44 is 300 nm to 10 μm, Mie scattering (see FIG. 4) becomes dominant and forward scattering becomes strong. When the average sphere equivalent diameter of the light scattering material 44 is 300 nm to 10 μm, the direction of light propagating through the planarizing layer 40 can be aligned in the front direction.

  Light incident on the light extraction surface 21 at an incident angle greater than the critical angle is totally reflected by the light extraction surface 21. The totally reflected light passes through the diffraction grating 31 during one or more round trips between the light extraction surface 21 and the light reflection surface (for example, the interface between the reflective electrode 70 and the organic layer 60). By being repeatedly scattered by the light scattering materials 34 and 44, the incident angle is changed to an incident angle less than the critical angle, and finally emitted from the light extraction surface 21 to the outside.

  In the present embodiment, both the concavo-convex layer 30 and the flattening layer 40 include a light scattering material, but either one may include a light scattering material.

  For example, as shown in FIG. 7, the uneven layer 30 may include the light scattering material 34, and the planarization layer 43 may not include the light scattering material 44. In the case of the example shown in FIG. 7 (first modification), the transmissive diffraction grating 31 transmits light incident from the planarizing layer 43 to the concave-convex layer 30 at various incident angles, and the direction of most transmitted light. Align in the front direction. Therefore, total reflection at the interface such as the light extraction surface 21 can be suppressed, and the light extraction efficiency can be improved. The transmissive diffraction grating 31 plays a role of suppressing total reflection of light when entering the concave / convex layer 30 from the planarizing layer 43. The light scattering material 34 in the concavo-convex layer 30 scatters light propagating through the concavo-convex layer 30, reduces the angle dependency of the light intensity by the diffraction grating 31, and the color (wavelength) of the light by the diffraction grating 31. To reduce the angle dependence. In addition, the light scattering material 34 in the concavo-convex layer 30 aligns the direction of light propagating in the concavo-convex layer 30 with the front direction, and improves light extraction efficiency.

  Further, as shown in FIG. 8, the planarization layer 40 may include the light scattering material 44, and the uneven layer 33 may not include the light scattering material 34. In the case of the example shown in FIG. 8 (second modification), the transmissive diffraction grating 31 transmits light incident at various incident angles from the planarizing layer 40 to the uneven layer 33, and the direction of most transmitted light. Align in the front direction. Therefore, total reflection at the interface such as the light extraction surface 21 can be suppressed, and the light extraction efficiency can be improved. Further, the transmission type diffraction grating 31 plays a role of suppressing total reflection of light when entering the uneven layer 33 from the planarizing layer 40. The light scattering material 44 in the planarization layer 40 aligns the direction of light propagating in the planarization layer 40 with the front direction. The direction of light incident on the diffraction grating 31 from the planarization layer 40 is aligned in the front direction, the direction of light transmitted through the diffraction grating 31 is easily aligned in the front direction, and the light extraction efficiency is further improved.

[Second Embodiment]
In the first embodiment, the concavo-convex layer 30 forms the diffraction grating 31. On the other hand, the present embodiment is different in that the uneven layer forms a plurality of prisms. Hereinafter, differences will be mainly described.

  FIG. 9 is a cross-sectional view showing an organic LED element according to the second embodiment of the present invention. In FIG. 9, the unevenness of the uneven layer 130 is exaggerated for convenience.

  The organic LED element 110 is a bottom emission type, and includes the transparent substrate 20, the uneven layer 130, the planarization layer 140, the transparent electrode 50, the organic layer 60, and the reflective electrode 70 in this order. The laminated substrate 111 is composed of the transparent substrate 20, the uneven layer 130, and the planarization layer 140, and the light emitting element 12 is composed of the transparent electrode 50, the organic layer 60, the reflective electrode 70, and the like. In the case of illumination, one light emitting element 12 may be formed on the planarization layer 140. In the case of image display, the light emitting element 12 is provided for each pixel, and the plurality of light emitting elements 12 are arranged on the planarization layer 140.

  The light emitted from the organic layer 60 passes through the transparent electrode 50, the planarization layer 140, the uneven layer 130, and the transparent substrate 20, and is emitted to the outside from the light extraction surface 21 of the transparent substrate 20. The light extraction surface 21 is a surface on the opposite side to the uneven layer 130 side in the transparent substrate 20.

  In the present embodiment, the uneven layer 130 forms a plurality of prisms 131. The prism 131 is provided on the planarization layer 140 side. In the following description, the incident angle and the reflection angle at the prism 131 mean an angle formed by a direction perpendicular to the light extraction surface 21 (hereinafter referred to as “front direction”) and the light traveling direction.

(Uneven layer)
The uneven layer 130 is formed on the transparent substrate 20 by, for example, an imprint method. In the imprint method, a layer of a molding material is sandwiched between the transparent substrate 20 and a mold, and an uneven layer 130 to which the uneven pattern of the mold is transferred is formed on the transparent substrate 20. The concavo-convex pattern of the concavo-convex layer 130 is a pattern in which the concavo-convex pattern of the mold is substantially inverted. The layer of a molding material contains the below-mentioned light-scattering material as needed.

  In addition, although the uneven | corrugated layer 130 of this embodiment is formed by the imprint method, you may form by the photolithographic method, EB drawing method, interference exposure method, etc.

  The uneven layer 130 forms a plurality of prisms 131. The bottom surfaces of the plurality of prisms 131 are arranged on the same plane. The plurality of prisms 131 are periodically arranged, for example, a regular hexagonal lattice, a quasi-hexagonal lattice, a regular tetragonal lattice, or a quasi-tetragonal lattice. The pitch P2 between the nearest prisms 131 is sufficiently larger than the wavelength of visible light (5 μm <P2 ≦ 50 μm). The height H2 of the prism is preferably 5 μm or more and 50 μm or less. The shape of the prism 131 may be various, and examples thereof include a pyramid shape (for example, a quadrangular pyramid shape and a triangular pyramid shape), a truncated pyramid shape, and the like.

  The prism 131 transmits light incident at various incident angles from the planarizing layer 140 to the uneven layer 130, and aligns the direction of most transmitted light in the front direction. Therefore, total reflection at the interface such as the light extraction surface 21 can be suppressed, and the light extraction efficiency can be improved.

  The prism 131 plays a role of suppressing total reflection of light when entering the uneven layer 130 from the planarizing layer 140.

  FIG. 10 is a diagram for explaining that the total reflection of light is reduced by the prism of FIG. 9. 10, illustration of the light emitting element 12 and the light-scattering materials 134 and 144 is abbreviate | omitted for convenience.

  In general, when the interface between the adjacent high refractive index layer and the low refractive index layer is flat, light incident from the high refractive index layer to the low refractive index layer at an incident angle greater than the critical angle is totally reflected. End up.

  In this embodiment, the interface between the planarization layer 140 as the high refractive index layer and the uneven layer 130 as the low refractive index layer has a fine uneven structure, and the uneven layer 130 forms the prism 131. Therefore, most of the light that is totally reflected when the interface is flat is transmitted through the inclined surface of the prism 131 and propagates into the uneven layer 130 as shown in FIG. The light transmitted through one inclined surface of the prism 131 is reflected by, for example, the other inclined surface of the prism 131 and propagates toward the transparent substrate 20. Therefore, it is possible to suppress the total reflection of light when entering the uneven layer 130 from the planarizing layer 140.

  In addition, when the interface is flat, the pitch P2 and the height H2 of the prism 131 may be optimized so that most of the light transmitted through the interface without being totally reflected at the interface is transmitted through the prism 131.

  By the way, the refractive index of light differs depending on the wavelength of light, and the refraction angle of light differs for each wavelength of light. Therefore, in the case of a prism that utilizes light refraction, when the angle at which the prism 131 is viewed changes, the color (wavelength) of the light transmitted through the prism 131 changes.

  Therefore, as shown in FIG. 9, the uneven layer 130 may include a base material 133 such as a resin and a light scattering material 134 dispersed in the base material 133. The light scattering material 134 scatters the light propagating through the concavo-convex layer 130 to reduce the angle dependency of the color (wavelength) of the light.

  In order to suppress reflection at the interface between the base material 133 and the transparent substrate 20, the base material 133 is made of a material having a refractive index difference from the transparent substrate 20 of 0.3 or less, as in the first embodiment. Is preferred. The refractive index of the base material 133 may be higher or lower than the refractive index of the transparent substrate 20, but is preferably equal to or lower than the refractive index of the transparent substrate 20.

The light scattering material 134 has a refractive index different from that of the base material 133 and is composed of air having a refractive index lower than that of the base material 133, a metal oxide having a refractive index higher than that of the base material 133, or both. Examples of the metal oxide include zirconia (ZrO ₂ ), titania (TiO ₂ ), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), tin oxide (SnO ₂ ), and the like.

  The average sphere equivalent diameter (average particle diameter) of the light scattering material 134 is preferably 300 nm to 10 μm. When the average equivalent sphere diameter of the light scattering material 134 exceeds 10 μm, the light scattering material 134 is difficult to disperse in the base material 133 and tends to be unevenly distributed. On the other hand, when the average equivalent sphere diameter of the light scattering material 134 is less than 300 nm, since the wavelength of visible light is too short, Rayleigh scattering (see FIG. 3) becomes dominant and backscattering becomes strong. Efficiency is reduced.

  When the average equivalent sphere diameter of the light scattering material 134 is 300 nm to 10 μm, Mie scattering (see FIG. 4) becomes dominant, forward scattering becomes strong, and the direction of light propagating in the uneven layer 130 is aligned in the front direction. be able to.

(Flattening layer)
The planarization layer 140 is provided on the uneven layer 130 and absorbs the unevenness of the uneven layer 130. The transparent electrode 50, the organic layer 60, and the reflective electrode 70 provided on the flat surface of the flattening layer 140 can exhibit the performance as designed.

  The planarization layer 140 is formed on the uneven surface of the uneven layer 130 by, for example, a wet coating method. Before the planarization layer 140 is formed, a process of heat-treating the uneven layer 130 may be performed. It is possible to improve the polymerization rate of the resin of the uneven layer 130 and to remove birefringence of the uneven layer 130.

  The planarization layer 140 may include a base material 143 such as a resin and a light scattering material 144 dispersed in the base material 143. Similar to the light scattering material 134 of the concavo-convex layer 130, the light scattering material 144 aligns the direction of light propagating in the planarization layer 140 with the front direction, and the direction of light incident on the prism 131 from the planarization layer 140 is the front direction. Align in the direction.

  In general, the more the direction of light incident on the prism is aligned in the front direction, the easier it is for the direction of light transmitted through the prism to be aligned in the front direction.

  In the present embodiment, since the direction of light incident on the prism 131 from the planarization layer 140 is aligned in the front direction, the direction of light transmitted through the prism 131 is easily easily aligned in the front direction, and light extraction efficiency is improved. To do.

  In order to suppress reflection at the interface between the base material 143 and the transparent electrode 50, the base material 143 is made of a material having a refractive index difference with the transparent electrode 50 of 0.3 or less, as in the first embodiment. Is preferred. The refractive index of the substrate 143 may be higher or lower than the refractive index of the transparent electrode 50, but is preferably equal to or lower than the refractive index of the transparent electrode 50.

  The base material 143 has a refractive index different from that of the base material 133 of the uneven layer 130. Since the base material 143 is in contact with the transparent electrode 50 having a higher refractive index than the transparent substrate 20, the base material 143 preferably has a higher refractive index than the base material 133 of the uneven layer 130 in contact with the transparent substrate 20.

The light scattering material 144 has a refractive index different from that of the base material 143 and is composed of air having a lower refractive index than the base material 143, a metal oxide having a higher refractive index than the base material 143, or both. Examples of the metal oxide include zirconia (ZrO ₂ ), titania (TiO ₂ ), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), tin oxide (SnO ₂ ), and the like.

  The average sphere equivalent diameter (average particle diameter) of the light scattering material 144 is preferably 300 nm to 10 μm. If the average equivalent sphere diameter of the light scattering material 144 exceeds 10 μm, the light scattering material 144 is difficult to disperse in the base material 143 and tends to be unevenly distributed. When the average sphere equivalent diameter of the light scattering material 144 is less than 300 nm, it is too short than the wavelength of visible light, so Rayleigh scattering (see FIG. 3) becomes dominant and backscattering becomes strong. descend.

  When the average sphere equivalent diameter of the light scattering material 144 is 300 nm to 10 μm, Mie scattering (see FIG. 4) becomes dominant and forward scattering becomes strong. When the average sphere equivalent diameter of the light scattering material 144 is 300 nm to 10 μm, the direction of light propagating in the planarization layer 140 can be aligned in the front direction.

  Light incident on the light extraction surface 21 at an incident angle greater than the critical angle is totally reflected by the light extraction surface 21. The totally reflected light passes through the prism 131 while reciprocating between the light extraction surface 21 and the light reflection surface (for example, the interface between the reflection electrode 70 and the organic layer 60) one or more times. By being repeatedly scattered by the scattering materials 134 and 144, the incident angle is changed to an incident angle less than the critical angle, and finally emitted from the light extraction surface 21 to the outside.

  In the present embodiment, both the concavo-convex layer 130 and the flattening layer 140 include a light scattering material, but either one may include a light scattering material.

  For example, as shown in FIG. 11, the uneven layer 130 may include the light scattering material 134, and the planarization layer 143 may not include the light scattering material 144. In the case of the example shown in FIG. 11 (first modification), the prism 131 transmits light incident from the planarizing layer 143 to the uneven layer 130 at various incident angles, and the direction of most transmitted light is directed to the front direction. Align. Therefore, total reflection at the interface such as the light extraction surface 21 can be suppressed, and the light extraction efficiency can be improved. In addition, the prism 131 plays a role of suppressing total reflection of light when entering the uneven layer 130 from the planarizing layer 143. The light scattering material 134 in the concavo-convex layer 130 scatters light propagating through the concavo-convex layer 130, reduces the angle dependency of the light intensity by the prism 131, and the angle of the color (wavelength) of the light by the prism 131. Reduce dependency. In addition, the light scattering material 134 in the concavo-convex layer 130 aligns the direction of light propagating in the concavo-convex layer 130 with the front direction, and improves light extraction efficiency.

  Further, as shown in FIG. 12, only the planarization layer 140 includes the light scattering material 144, and the uneven layer 133 does not need to include the light scattering material 134. In the case of the example shown in FIG. 12 (second modified example), the prism 131 transmits light incident at various incident angles from the planarizing layer 140 to the concave-convex layer 133, and most of the transmitted light is directed in the front direction. Align. Therefore, total reflection at the interface such as the light extraction surface 21 can be suppressed, and the light extraction efficiency can be improved. In addition, the prism 131 plays a role of suppressing total reflection of light when entering the uneven layer 133 from the planarizing layer 140. The light scattering material 144 in the planarization layer 140 aligns the direction of light propagating in the planarization layer 140 with the front direction. The direction of light incident on the prism 131 from the planarization layer 140 is aligned in the front direction, the direction of light transmitted through the prism 131 is easily aligned in the front direction, and the light extraction efficiency is further improved.

[Third Embodiment]
In the second embodiment, the uneven layer 130 forms the plurality of prisms 131. On the other hand, the present embodiment is different in that the uneven layer forms a plurality of lenses. Hereinafter, differences will be mainly described.

  FIG. 13 is a cross-sectional view showing an organic LED element according to the third embodiment of the present invention. In FIG. 13, the unevenness of the uneven layer 230 is exaggerated for convenience.

  The organic LED element 210 is a bottom emission type, and includes the transparent substrate 20, the uneven layer 230, the planarization layer 240, the transparent electrode 50, the organic layer 60, and the reflective electrode 70 in this order. The laminated substrate 211 is composed of the transparent substrate 20, the uneven layer 230, and the planarization layer 240, and the light emitting element 12 is composed of the transparent electrode 50, the organic layer 60, the reflective electrode 70, and the like. In the case of illumination, one light emitting element 12 may be formed on the planarization layer 240. In the case of image display, the light emitting element 12 is provided for each pixel, and the plurality of light emitting elements 12 are arranged on the planarization layer 240.

  The light emitted from the organic layer 60 is transmitted through the transparent electrode 50, the planarization layer 240, the uneven layer 230, and the transparent substrate 20, and is emitted to the outside from the light extraction surface 21 of the transparent substrate 20. The light extraction surface 21 is a surface on the opposite side to the uneven layer 230 side in the transparent substrate 20.

  In the present embodiment, the uneven layer 230 forms a plurality of lenses 231. The lens 231 is provided on the planarization layer 240 side. In the following description, the incident angle and the reflection angle at the lens 231 mean an angle formed by a direction perpendicular to the light extraction surface 21 (hereinafter referred to as “front direction”) and a light traveling direction.

(Uneven layer)
The uneven layer 230 is formed on the transparent substrate 20 by, for example, an imprint method. In the imprint method, a layer of a molding material is sandwiched between the transparent substrate 20 and a mold, and an uneven layer 230 to which the uneven pattern of the mold is transferred is formed on the transparent substrate 20. The concavo-convex pattern of the concavo-convex layer 230 is a pattern in which the concavo-convex pattern of the mold is substantially inverted. The layer of a molding material contains the below-mentioned light-scattering material as needed.

  In addition, although the uneven | corrugated layer 230 of this embodiment is formed by the imprint method, you may form by the photolithographic method, EB drawing method, interference exposure method, etc.

  The uneven layer 230 forms a plurality of lenses 231. The plurality of lenses 231 are periodically arranged, for example, in a regular hexagonal lattice shape, a quasi-hexagonal lattice shape, a regular tetragonal lattice shape, or a quasi-tetragonal lattice shape. The pitch P3 between the closest lenses 231 is sufficiently larger than the wavelength of visible light (5 μm <P3 ≦ 50 μm). As shown in FIG. 13, the lens 231 may be a concave lens or a convex lens as viewed from the planarization layer 240 side.

  The lens 231 transmits light incident at various incident angles from the planarizing layer 240 to the concave-convex layer 230, and aligns the direction of most transmitted light in the front direction. Therefore, total reflection at the interface such as the light extraction surface 21 can be suppressed, and the light extraction efficiency can be improved.

  The lens 231 plays a role of suppressing total reflection of light when entering the uneven layer 230 from the planarizing layer 240.

  FIG. 14 is a diagram for explaining that the total reflection of light is reduced by the lens of FIG. In FIG. 14, illustration of the light emitting element 12 and the light scattering materials 234 and 244 is omitted for convenience.

  In general, when the interface between the adjacent high refractive index layer and the low refractive index layer is flat, light incident from the high refractive index layer to the low refractive index layer at an incident angle greater than the critical angle is totally reflected. End up.

  In this embodiment, the interface between the planarization layer 240 as the high refractive index layer and the uneven layer 230 as the low refractive index layer has a fine uneven structure, and the uneven layer 230 forms the lens 231. Therefore, most of the light that is totally reflected when the interface is flat passes through the curved surface of the lens 231 and propagates through the uneven layer 230 as shown in FIG. Therefore, it is possible to suppress the total reflection of light when entering the concavo-convex layer 230 from the planarizing layer 240.

  In addition, when the interface is flat, the pitch P3 and the height of the lens 231 may be optimized so that most of the light transmitted through the interface without being totally reflected at the interface is transmitted through the lens 231.

  By the way, in the case of a lens using refraction, the angle at which the intensity of transmitted light is increased differs for each wavelength of light transmitted through the lens.

  Therefore, as shown in FIG. 13, the uneven layer 230 may include a base material 233 such as a resin and a light scattering material 234 dispersed in the base material 233. The light scattering material 234 scatters the light propagating through the uneven layer 230, thereby reducing the angle dependency of the light intensity, and reducing the angle dependency of the color (wavelength) of the light.

  In order to suppress reflection at the interface between the base material 233 and the transparent substrate 20, the base material 233 is made of a material having a refractive index difference with the transparent substrate 20 of 0.3 or less, as in the first embodiment. Is preferred. The refractive index of the base material 233 may be higher or lower than the refractive index of the transparent substrate 20, but is preferably equal to or lower than the refractive index of the transparent substrate 20.

The light scattering material 234 has a refractive index different from that of the base material 233, and is composed of air having a lower refractive index than the base material 233, a metal oxide having a higher refractive index than the base material 233, or both. Examples of the metal oxide include zirconia (ZrO ₂ ), titania (TiO ₂ ), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), tin oxide (SnO ₂ ), and the like.

  The average sphere equivalent diameter (average particle diameter) of the light scattering material 234 is preferably 300 nm to 10 μm. If the average equivalent sphere diameter of the light scattering material 234 exceeds 10 μm, the light scattering material 234 is difficult to disperse in the base material 233 and tends to be unevenly distributed. On the other hand, when the average sphere equivalent diameter of the light scattering material 234 is less than 300 nm, since the wavelength of visible light is too short, Rayleigh scattering (see FIG. 3) becomes dominant and backscattering becomes strong. Efficiency is reduced.

  When the average equivalent sphere diameter of the light scattering material 234 is 300 nm to 10 μm, Mie scattering (see FIG. 4) becomes dominant, forward scattering becomes strong, and the direction of light propagating in the uneven layer 230 is aligned in the front direction. be able to.

(Flattening layer)
The planarization layer 240 is provided on the uneven layer 230 and absorbs the unevenness of the uneven layer 230. The transparent electrode 50, the organic layer 60, and the reflective electrode 70 provided on the flat surface of the flattening layer 240 can exhibit the performance as designed.

  The planarization layer 240 is formed on the uneven surface of the uneven layer 230 by, for example, a wet coat method. Before the planarization layer 240 is formed, a step of heat treating the uneven layer 230 may be performed. It is possible to improve the polymerization rate of the resin of the uneven layer 230 and to remove the birefringence of the uneven layer 230.

  The planarization layer 240 may include a base material 243 such as a resin and a light scattering material 244 dispersed in the base material 243. Similar to the light scattering material 234 of the concavo-convex layer 230, the light scattering material 244 aligns the direction of light propagating in the planarization layer 240 with the front direction, and the direction of light incident on the lens 231 from the planarization layer 240 is the front direction. Align in the direction.

  Generally, the more the direction of light incident on the lens is aligned in the front direction, the easier it is for the direction of light transmitted through the lens to be aligned in the front direction.

  In the present embodiment, since the direction of light incident on the lens 231 from the planarization layer 240 is aligned in the front direction, the direction of light transmitted through the lens 231 is easily aligned efficiently in the front direction, and light extraction efficiency is improved. To do.

  In order to suppress reflection at the interface between the base material 243 and the transparent electrode 50, the base material 243 is made of a material having a refractive index difference with the transparent electrode 50 of 0.3 or less, as in the first embodiment. Is preferred. The refractive index of the substrate 243 may be higher or lower than the refractive index of the transparent electrode 50, but is preferably equal to or lower than the refractive index of the transparent electrode 50.

  The base material 243 has a refractive index different from that of the base material 233 of the uneven layer 230. Since the base material 243 is in contact with the transparent electrode 50 having a higher refractive index than the transparent substrate 20, the base material 243 preferably has a higher refractive index than the base material 233 of the uneven layer 230 in contact with the transparent substrate 20.

The light scattering material 244 has a refractive index different from that of the base material 243 and is composed of air having a lower refractive index than the base material 243, a metal oxide having a higher refractive index than the base material 243, or both. Examples of the metal oxide include zirconia (ZrO ₂ ), titania (TiO ₂ ), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), tin oxide (SnO ₂ ), and the like.

  The average sphere equivalent diameter (average particle diameter) of the light scattering material 244 is preferably 300 nm to 10 μm. If the average equivalent sphere diameter of the light scattering material 244 exceeds 10 μm, the light scattering material 244 is difficult to disperse in the base material 243 and tends to be unevenly distributed. If the average equivalent sphere diameter of the light scattering material 244 is less than 300 nm, it is too short than the wavelength of visible light, so Rayleigh scattering (see FIG. 3) becomes dominant and backscattering becomes strong, so that the light extraction efficiency is improved. descend.

  When the average spherical equivalent diameter of the light scattering material 244 is 300 nm to 10 μm, Mie scattering (see FIG. 4) becomes dominant and forward scattering becomes strong. When the average sphere equivalent diameter of the light scattering material 244 is 300 nm to 10 μm, the direction of light propagating in the planarization layer 240 can be aligned in the front direction.

  Light incident on the light extraction surface 21 at an incident angle greater than the critical angle is totally reflected by the light extraction surface 21. The totally reflected light passes through the lens 231 during one or more round trips between the light extraction surface 21 and the light reflection surface (for example, the interface between the reflective electrode 70 and the organic layer 60), By being repeatedly scattered by the scattering materials 234 and 244, the incident angle is changed to an incident angle less than the critical angle and finally emitted from the light extraction surface 21 to the outside.

  In the present embodiment, both the concavo-convex layer 230 and the planarization layer 240 include a light scattering material, but either one may include a light scattering material.

  For example, as illustrated in FIG. 15, the uneven layer 230 may include the light scattering material 234, and the planarization layer 243 may not include the light scattering material 244. In the case of the example shown in FIG. 15 (first modification), the lens 231 transmits light incident from the planarizing layer 243 to the uneven layer 230 at various incident angles, and the direction of most of the transmitted light is directed to the front direction. Align. Therefore, total reflection at the interface such as the light extraction surface 21 can be suppressed, and the light extraction efficiency can be improved. Further, the lens 231 plays a role of suppressing total reflection of light when entering the uneven layer 230 from the planarizing layer 243. The light scattering material 234 in the concavo-convex layer 230 scatters the light propagating through the concavo-convex layer 230, reduces the angle dependency of the light intensity by the lens 231, and the angle of the color (wavelength) of the light by the lens 231. Reduce dependency. Further, the light scattering material 234 in the uneven layer 230 aligns the direction of light propagating in the uneven layer 230 with the front direction, and improves the light extraction efficiency.

  Further, as shown in FIG. 16, the planarization layer 240 may include the light scattering material 244 and the uneven layer 233 may not include the light scattering material 234. In the case of the example shown in FIG. 15 (second modification), the lens 231 transmits light incident at various incident angles from the planarizing layer 240 to the uneven layer 233, and the direction of most of the transmitted light is directed to the front direction. Align. Therefore, total reflection at the interface such as the light extraction surface 21 can be suppressed, and the light extraction efficiency can be improved. In addition, the lens 231 plays a role of suppressing total reflection of light when entering the uneven layer 233 from the planarizing layer 240. The light scattering material 244 in the planarization layer 240 aligns the direction of light propagating in the planarization layer 240 with the front direction. The direction of light incident on the lens 231 from the planarizing layer 240 is aligned in the front direction, the direction of light transmitted through the lens 231 is easily aligned in the front direction, and the light extraction efficiency is further improved.

[Fourth Embodiment]
In the first embodiment, the concavo-convex layer 30 forms the diffraction grating 31. On the other hand, the present embodiment is different in that the uneven layer has a moth-eye structure. Hereinafter, differences will be mainly described.

  FIG. 17 is a sectional view showing an organic LED element according to the fourth embodiment of the present invention. In FIG. 17, the unevenness of the moth-eye structure 331 is exaggerated for convenience.

  The organic LED element 310 is a bottom emission type, and includes the transparent substrate 20, the uneven layer 330, the planarization layer 340, the transparent electrode 50, the organic layer 60, and the reflective electrode 70 in this order. The laminated substrate 311 is constituted by the transparent substrate 20, the uneven layer 330, and the planarizing layer 340, and the light emitting element 12 is constituted by the transparent electrode 50, the organic layer 60, the reflective electrode 70, and the like. In the case of illumination, one light emitting element 12 may be formed on the planarization layer 340. In the case of image display, the light emitting element 12 is provided for each pixel, and the plurality of light emitting elements 12 are arranged on the planarization layer 340.

  The light emitted from the organic layer 60 is transmitted through the transparent electrode 50, the planarization layer 340, the uneven layer 330, and the transparent substrate 20, and is emitted to the outside from the light extraction surface 21 of the transparent substrate 20. The light extraction surface 21 is a surface on the opposite side to the uneven layer 330 side in the transparent substrate 20.

  In the present embodiment, the uneven layer 330 has a moth-eye structure 331. The moth-eye structure 331 is provided on the planarization layer 340 side. In the following description, the incident angle and the reflection angle in the moth-eye structure 331 mean an angle formed by a direction perpendicular to the light extraction surface 21 (hereinafter referred to as “front direction”) and the light traveling direction.

(Uneven layer)
The uneven layer 330 is formed on the transparent substrate 20 by, for example, an imprint method. In the imprint method, the concavo-convex layer 330 is formed by transferring the concavo-convex pattern of the mold onto the surface of the layer of the molding material provided on the transparent substrate 20. The uneven layer 330 has an uneven pattern in which the uneven pattern of the mold is substantially inverted. The layer of a molding material contains the below-mentioned light-scattering material as needed.

  In addition, although the uneven | corrugated layer 330 of this embodiment is formed by the imprint method, you may form by the photolithographic method, EB drawing method, interference exposure method, etc.

  A portion of the uneven layer 330 on the flattening layer 340 side constitutes a moth-eye structure 331. The moth-eye structure 331 has a plurality of protrusions, and the bottom surfaces of the plurality of protrusions are arranged on the same plane. The plurality of convex portions are periodically arranged, for example, in a regular hexagonal lattice shape, a quasi-hexagonal lattice shape, a regular tetragonal lattice shape, or a quasi-tetragonal lattice shape. The pitch P4 between the nearest convex portions is equal to or less than the wavelength of visible light (P4 ≦ 300 nm), and is typically 250 nm. The height H4 of the convex portion is typically 300 nm. Adjacent protrusions may be in contact or separated from each other, but are arranged so that the skirts overlap in order to efficiently reduce the reflectance at the interface between the uneven layer 330 and the planarization layer 340. It is preferable. The shape of the convex portion may be various, and examples thereof include a cone shape, a truncated cone shape, a pyramid shape, a truncated pyramid shape, and a bell shape.

  FIG. 18 is an explanatory diagram of light transmission by the moth-eye structure 331 of FIG. In FIG. 18, illustration of the light emitting element 12 and the light scattering materials 334 and 344 is omitted for convenience.

  In the moth-eye structure 331, since the refractive index in the direction perpendicular to the light extraction surface 21 continuously changes, the reflectance is low (1% or less) and the transmittance is high regardless of the incident angle of light and the wavelength of light. Since most of the light is transmitted as shown by the arrows in FIG. 18, the light extraction efficiency is good. In addition, the moth-eye structure 331 does not cause light diffraction or light spectroscopy as compared with a conventional multilayer-film reflectance reduction film (Anti-Reflection = AR) film, and therefore the light extraction surface 21 when the viewing angle changes. The brightness and color (wavelength) of the are difficult to change.

  The uneven layer 330 may include a base material 333 such as a resin and a light scattering material 334 dispersed in the base material 333. The light transmitted through the uneven layer 330 is scattered by the light scattering material 334 and enters the light extraction surface 21. Light having an incident angle less than the critical angle is emitted from the light extraction surface 21 to the outside. On the other hand, most of the light whose incident angle is greater than or equal to the critical angle is totally reflected by the light extraction surface 21, and then the light extraction surface 21 and the light reflection surface (for example, the interface between the reflective electrode 70 and the organic layer 60). While being reciprocated once or more, the light scattering material 334 repeatedly scatters, changes to an incident angle less than the critical angle, and is finally extracted from the light extraction surface 21.

  In order to suppress reflection at the interface between the base material 333 and the transparent substrate 20, the base material 333 is made of a material having a refractive index difference from the transparent substrate 20 of 0.3 or less, as in the first embodiment. Is preferred. The refractive index of the base material 333 may be higher or lower than the refractive index of the transparent substrate 20, but is preferably equal to or lower than the refractive index of the transparent substrate 20.

The light scattering material 334 has a refractive index different from that of the base material 333 and is composed of air having a lower refractive index than the base material 333, a metal oxide having a higher refractive index than the base material 333, or both. Examples of the metal oxide include zirconia (ZrO ₂ ), titania (TiO ₂ ), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), tin oxide (SnO ₂ ), and the like.

  The average sphere equivalent diameter (average particle diameter) of the light scattering material 334 is preferably 300 nm to 10 μm. If the average equivalent sphere diameter of the light scattering material 334 exceeds 10 μm, the light scattering material 334 is difficult to disperse in the base material 333 and tends to be unevenly distributed. On the other hand, when the average sphere equivalent diameter of the light scattering material 334 is less than 300 nm, since the wavelength of visible light is too short, Rayleigh scattering (see FIG. 3) becomes dominant and backscattering becomes strong. Efficiency is reduced.

  When the average equivalent sphere diameter of the light scattering material 334 is 300 nm to 10 μm, Mie scattering (see FIG. 4) becomes dominant, forward scattering becomes strong, and the direction of light propagating in the uneven layer 330 is aligned in the front direction. Thus, total reflection at the interface such as the light extraction surface 21 can be reduced.

(Flattening layer)
The planarization layer 340 is provided on the uneven layer 330 and absorbs the unevenness of the uneven layer 330. The transparent electrode 50, the organic layer 60, and the reflective electrode 70 provided on the flat surface of the flattening layer 340 can exhibit the performance as designed.

  The planarization layer 340 is formed on the uneven surface of the uneven layer 330 by, for example, a wet coat method. Before the planarization layer 340 is formed, a step (for example, a heat treatment step) for proceeding with a crosslinking reaction of the resin of the uneven layer 330 may be performed.

  The planarization layer 340 may include a base material 343 such as a resin and a light scattering material 344 dispersed in the base material 343. The light transmitted through the planarization layer 340 is scattered by the light scattering material 344 and enters the light extraction surface 21. Light having an incident angle less than the critical angle is emitted from the light extraction surface 21 to the outside. On the other hand, most of the light whose incident angle is greater than or equal to the critical angle is totally reflected by the light extraction surface 21, and then the light extraction surface 21 and the light reflection surface (for example, the interface between the reflective electrode 70 and the organic layer 60). While being reciprocated once or more, the light scattering material 344 repeatedly scatters, changes to an incident angle less than the critical angle, and finally is extracted from the light extraction surface 21.

  In order to suppress reflection at the interface between the base material 343 and the transparent electrode 50, the base material 343 is made of a material having a refractive index difference from the transparent electrode 50 of 0.3 or less, as in the first embodiment. Is preferred. The refractive index of the base material 343 may be higher or lower than the refractive index of the transparent electrode 50, but is preferably equal to or lower than the refractive index of the transparent electrode 50.

  The base material 343 has a refractive index different from that of the base material 333 of the uneven layer 330. Since the base material 343 is in contact with the transparent electrode 50 having a higher refractive index than the transparent substrate 20, the base material 343 preferably has a higher refractive index than the base material 333 of the uneven layer 330 in contact with the transparent substrate 20.

The light scattering material 344 has a refractive index different from that of the base material 343, and is formed of air having a lower refractive index than the base material 343, a metal oxide having a higher refractive index than the base material 343, or both. Examples of the metal oxide include zirconia (ZrO ₂ ), titania (TiO ₂ ), silica (SiO ₂ ), alumina (Al ₂ O ₃ ), tin oxide (SnO ₂ ), and the like.

  The average sphere equivalent diameter (average particle diameter) of the light scattering material 344 is preferably 300 nm to 10 μm. If the average equivalent sphere diameter of the light scattering material 344 exceeds 10 μm, the light scattering material 344 is difficult to disperse in the base material 343 and tends to be unevenly distributed. If the average equivalent sphere diameter of the light scattering material 344 is less than 300 nm, it is too shorter than the wavelength of visible light, so Rayleigh scattering (see FIG. 3) becomes dominant and backscattering becomes strong. descend.

  When the average equivalent sphere diameter of the light scattering material 344 is 300 nm to 10 μm, Mie scattering (see FIG. 4) becomes dominant, forward scattering becomes strong, and the direction of light propagating in the uneven layer 340 is aligned in the front direction. Thus, total reflection at the interface such as the light extraction surface 21 can be reduced.

  In the present embodiment, both the concavo-convex layer 330 and the planarization layer 340 include a light scattering material, but either one may include a light scattering material.

  For example, as illustrated in FIG. 19, the uneven layer 330 may include the light scattering material 334, and the planarization layer 343 may not include the light scattering material 344. In the case of the example shown in FIG. 19 (first modified example), the moth-eye structure 331 has low reflectance (1% or less), high transmittance, and good light extraction efficiency regardless of the incident angle of light and the wavelength of light. . Also, most of the light incident on the light extraction surface 21 at an incident angle greater than the critical angle is totally reflected by the light extraction surface 21, and then the light extraction surface 21 and the light reflection surface (for example, the reflective electrode 70 and the organic layer). The light scattering material 334 in the concavo-convex layer 330 repeatedly scatters and changes to an incident angle less than the critical angle, and finally is extracted from the light extraction surface 21. . In addition, the scattering material 334 in the uneven layer 330 aligns the direction of light propagating in the uneven layer 330 with the front direction, suppresses total reflection at the interface such as the light extraction surface 21, and improves light extraction efficiency.

  In addition, as illustrated in FIG. 20, the planarization layer 340 may include the light scattering material 344 and the uneven layer 333 may not include the light scattering material 334. In the case of the example shown in FIG. 20 (second modified example), the moth-eye structure 331 has low reflectance (1% or less), high transmittance, and good light extraction efficiency regardless of the incident angle of light and the wavelength of light. . Also, most of the light incident on the light extraction surface 21 at an incident angle greater than the critical angle is totally reflected by the light extraction surface 21, and then the light extraction surface 21 and the light reflection surface (for example, the reflective electrode 70 and the organic layer). 60), the light scattering material 344 in the planarization layer 340 is repeatedly scattered by the light scattering material 344, changes to an incident angle less than the critical angle, and finally is extracted from the light extraction surface 21. It is. In addition, the scattering material 344 in the planarization layer 340 aligns the direction of light propagating in the planarization layer 340 with the front direction, suppresses total reflection at the interface such as the light extraction surface 21, and improves light extraction efficiency. .

  As mentioned above, although 1st-4th embodiment etc. were demonstrated about the laminated substrate for organic LED elements, this invention is not restrict | limited to the said embodiment. Various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

DESCRIPTION OF SYMBOLS 10 Organic LED element 11 Laminated substrate 12 for organic LED elements Light emitting element 20 Transparent substrate 30 Concavity and convexity layer 31 Diffraction grating 33 Base material 34 Light scattering material 40 Planarization layer 43 Base material 44 Light scattering material 50 Transparent electrode 60 Organic layer 70 Reflection Electrode 130 Concavity and convexity layer 131 Prism 230 Concavity and convexity layer 231 Lens 330 Concavity and convexity layer 331 Mosaic structure

Claims (9)

Comprising a transparent substrate, a concavo-convex layer provided on the transparent substrate, and a planarization layer provided on the concavo-convex surface of the concavo-convex layer, and emitting light of the organic layer through the planarization layer and the concavo-convex layer, For taking out from the surface opposite to the concavo-convex layer side in the transparent substrate,
The uneven layer, the substrate, and a light scattering material dispersed in the base material seen including, forming a diffraction grating, laminated substrate for an organic LED element. Comprising a transparent substrate, a concavo-convex layer provided on the transparent substrate, and a planarization layer provided on the concavo-convex surface of the concavo-convex layer, and emitting light of the organic layer through the planarization layer and the concavo-convex layer, For taking out from the surface opposite to the concavo-convex layer side in the transparent substrate,
The uneven layer includes a substrate, and a light scattering material dispersed in the base material to form a plurality of prisms that are periodically arranged, laminated substrate for an organic LED element. A transparent substrate, a concavo-convex layer provided on the transparent substrate, and a flattening layer provided on the concavo-convex surface of the concavo-convex layer, and emitting light of the organic layer through the flattening layer and the concavo-convex layer, For taking out from the surface opposite to the concavo-convex layer side in the transparent substrate,
The uneven layer includes a substrate, and a light scattering material dispersed in the base material to form a plurality of lenses that are periodically arranged, laminated substrate for an organic LED element. Comprising a transparent substrate, a concavo-convex layer provided on the transparent substrate, and a planarization layer provided on the concavo-convex surface of the concavo-convex layer, and emitting light of the organic layer through the planarization layer and the concavo-convex layer, For taking out from the surface opposite to the concavo-convex layer side in the transparent substrate,
The uneven layer, the substrate, and includes a light scattering material dispersed in the base material, has a moth-eye structure in which a plurality of convex portions are periodically arranged, laminated substrate for an organic LED element. The multilayer substrate for an organic LED element according to any one of claims 1 to 4, wherein the light scattering material in the concavo-convex layer is a metal oxide particle, and the average particle size of the particle is 300 nm to 10 µm. . The said planarization layer is a laminated substrate for organic LED elements as described in any one of Claims 1-5 containing the base material and the light-scattering material disperse | distributed in this base material. The light-scattering material in the said planarization layer is a particle | grain of metal oxide, Comprising: The average particle diameter of this particle | grain is 300 nm-10 micrometers, The laminated substrate for organic LED elements of Claim 6 . Transparent electrode laminated substrate comprising a laminated substrate, and the transparent electrode provided on the planarization layer of the laminated substrate according to any one of claims 1-7. The laminated substrate according to any one of claims 1 to 7 and an organic LED element including a light emitting element provided in the laminate the planarization layer on the substrate.

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