WO2011161998A1 - Organic el element - Google Patents

Abstract

Disclosed is an organic EL element wherein light is extracted at a high efficiency and visibility is improved. The organic EL element is provided with a pair of electrodes (2, 4) and an organic layer (3) having at least one organic light-emitting layer. A fine periodic structure (5), in which the sequence period is less than or equal to the wavelength of light generated at the organic light-emitting layer, is formed on the surface of the electrode (first electrode (2)) on the light extraction side and/or the surface of a substrate (1) disposed on the light extraction side. The refractive index of a region neighboring the aforementioned electrode on the side opposing the organic layer (3) is represented by n1, the refractive index of the aforementioned electrode is represented by n2, and the refractive index of the organic layer (3) neighboring said electrode is represented by n3. When n1=n3, the relationship n1=n2=n3 or n2=n1=n3 is established, and when n3=n1, the relationship n2=n3=n1 or n3=n2=n1 is established. As a consequence, it is possible to prevent incident light having an angle less than the critical angle from being reflected, and to improve the light extraction efficiency of incident light having an angle equal to or greater than the critical angle. Moreover, it is possible to reduce outside light from being reflected.

Description

Organic EL device

The present invention relates to an organic electroluminescence element used for lighting fixtures, liquid crystal backlights, various displays, display devices, and the like.

Conventionally, an organic EL element (organic electroluminescence element) is known as a typical surface light emitter.

FIG. 5 shows an example of a conventional organic EL element. In this organic EL element, a light transmissive first electrode 2 is provided on the surface of a light transmissive substrate 1, and an organic layer 3 including an organic light emitting layer made of an organic electroluminescence material is formed on the first electrode 2. It is formed by providing a light-reflective second electrode 4 on the organic layer 3. The light emitted from the organic layer 3 by applying a voltage between the first electrode 2 and the second electrode 4 passes through the first electrode 2 and the substrate 1 and is extracted outside.

As described above, the organic EL element in the form shown in the drawing extracts light emitted from the organic layer 3 to the outside through the first electrode 2 and the substrate 1, but the light is caused by the difference in refractive index between the first electrode 2 and the substrate 1. If the light is totally reflected at the interface, the light extraction efficiency is lowered. In view of this, several proposals have conventionally been made as methods for improving the light extraction efficiency.

Patent Document 1 describes an organic EL light emitting device in which a light scattering portion made of scattering particles, a lens sheet, or the like is provided inside or outside a substrate on the light extraction side.

Patent Document 2 discloses an organic EL element in which a transparent resin layer, a transparent electrode, an organic EL layer, and a metal electrode are formed on a transparent substrate, and the transparent resin layer has a plurality of inverted dome shapes on the transparent electrode side. Are listed. The reverse dome-shaped transparent resin layer functions as a convex lens with respect to light emitted and traveling toward the transparent substrate.

Also, proposals have been made to reduce the reflection of external light and increase the visibility of the extracted light.

Patent Document 3 discloses a structure having a conversion layer in which electric power and an optical state are related, and an electrode layer related to the conversion layer, and a moth-eye structure on at least a part of the electrode layer facing the outside. A light utilization device having a light absorption region comprising: By forming a moth-eye structure outside the metal electrode where external light is reflected, the reflection is suppressed and a decrease in contrast of light from the light emitting layer is suppressed.

JP-A-8-83688 JP 2004-47383 A JP 2004-258364 A

When the light scattering part as in Patent Document 1 is formed, the amount of light below the critical angle at the interface between the electrode and the substrate or the interface between the substrate and the outside increases due to the forward scattering of the light, and the total reflection It is considered that the amount of light to be reduced. However, on the other hand, light that is within the critical angle from before being scattered by the light scattering part is also scattered, and the scattered light is partially absorbed when reflected by other electrodes, It is considered that there is a problem that the amount of extracted light does not increase dramatically.

Further, when a structure having a lens function as in Patent Document 2 is formed, the amount of light extracted can be increased by refracting light incident on the interface at a critical angle or more within the critical angle. However, a refractive index step is formed at the interface between the structure having a lens function and the layer in contact with the structure. For this reason, it is considered that there is a problem that the reflection caused only by the refractive index step that does not depend on the incident angle cannot be reduced, and a significant increase in light extraction efficiency cannot be expected.

In Patent Document 3, the moth-eye structure is used for the purpose of reducing reflection of external light. In this organic EL element, the moth-eye structure is formed on the surface of the metal electrode opposite to the light extraction side. Therefore, it is considered that this structure cannot contribute to the improvement of the light extraction efficiency.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an organic EL element that achieves both high-efficiency light extraction and improved visibility.

The organic EL device according to the first invention is an organic EL device comprising a pair of electrodes and an organic layer having at least one organic light emitting layer, and is provided on at least one surface of the light extraction side electrode or the light extraction side. A region in which a fine periodic structure having an arrangement period equal to or less than the wavelength of light generated in the organic light emitting layer is formed on at least one surface of the disposed substrate, and is adjacent to the light extraction side electrode on the side opposite to the organic layer Is n1, the refractive index of the electrode on the light extraction side is n2, and the refractive index of the organic layer adjacent to the electrode on the light extraction side is n3, n1 ≦ n2 ≦ n3 or n2 ≦ n1 ≦ n3 is established.

The organic EL device according to the second invention is an organic EL device comprising a pair of electrodes and an organic layer having at least one organic light emitting layer, and is provided on at least one surface of the light extraction side electrode or on the light extraction side. A region in which a fine periodic structure having an arrangement period equal to or less than the wavelength of light generated in the organic light emitting layer is formed on at least one surface of the disposed substrate, and is adjacent to the light extraction side electrode on the side opposite to the organic layer N2 ≦ n3 ≦ n1 or n3 ≦ n2 where n1 is the refractive index of the electrode on the light extraction side and n2 is the refractive index of the organic layer adjacent to the electrode on the light extraction side. It is characterized in that a relation of ≦ n1 is established.

In the organic EL element, it is preferable that the electrode on the light extraction side includes a light-transmitting resin and a fine conductive material. In that case, the fine conductive material preferably has a reflectance of 50% or more. Moreover, it is preferable that the said fine electroconductive substance produces anisotropic scattering. Moreover, it is preferable that the said fine electroconductive substance is silver nanowire.

In the organic EL element, the electrode on the light extraction side or the substrate disposed on the light extraction side has a single or a plurality of concave portions or convex portions on the surface, and a fine periodic structure is formed. Is preferred.

In the organic EL element, the electrode on the light extraction side or the substrate disposed on the light extraction side has a concave portion or a convex portion on the surface, and when viewed in plan, the concave portion or the convex portion is striped. It is preferable that the fine periodic structure is formed by being arranged in any one of a lattice shape, a concentric circle shape, and a honeycomb shape.

According to the present invention, it is possible to suppress the reflection of incident light below the critical angle, improve the light extraction efficiency of incident light above the critical angle, further reduce the reflection of external light, and achieve high efficiency. An organic EL element that achieves both light extraction and improved visibility can be obtained.

It is a schematic sectional drawing which shows an example of embodiment of the organic EL element of this invention. It is a schematic sectional drawing which shows another example of embodiment of the organic EL element of this invention. (A)-(d) is a perspective view explaining another example of embodiment of the organic EL element of this invention. The other example of embodiment of the organic EL element of this invention is shown, (a) is a schematic sectional drawing, (b) is the partially expanded view of (a). It is a schematic sectional drawing which shows an example of the conventional organic EL element.

Hereinafter, modes for carrying out the present invention will be described.

FIG. 1 shows an example of the layer structure of the organic EL element according to the present invention. In this organic EL element, a light transmissive first electrode 2 is provided on the surface of a light transmissive substrate 1, and an organic layer 3 including an organic light emitting layer made of an organic electroluminescence material is provided on the surface of the first electrode 2. Furthermore, it is formed by providing a light-reflective second electrode 4 on the surface of the organic layer 3. The light emitted from the organic layer 3 by applying a voltage between the first electrode 2 and the second electrode 4 is extracted outside through the first electrode 2 and the substrate 1. One form is an organic EL element called a bottom emission structure in which light is extracted through the substrate 1. One of the first electrode 2 and the second electrode 4 is a positive electrode and the other is a cathode. In the illustrated embodiment, the first electrode 2 is a positive electrode and the second electrode 4 is a cathode. And in the case of the organic EL element of such a structure, in order to solve the said subject, the interface of the board | substrate 1 arrange | positioned at the light extraction side and the 1st electrode 2 which is a transparent electrode, and the board | substrate 1 and the exterior If the refractive index difference at the interface is reduced, the reflection of light can be reduced. In addition, light extraction efficiency can be improved by refracting an incident angle that is greater than or equal to the critical angle within the critical angle by including conductive particles that cause light scattering in the first electrode, which is a transparent electrode.

Therefore, in the embodiment of FIG. 1, the arrangement period is equal to or less than the wavelength of light generated in the organic light emitting layer on the surface of the first electrode 2 which is the electrode on the light extraction side, that is, the light incident on this electrode. A fine periodic structure 5 having a wavelength or shorter is formed. The fine periodic structure 5 may be provided on at least one surface of the light extraction side electrode. Therefore, it is not limited to the form shown in the figure, and is on the surface of the first electrode 2 on the substrate 1 side, that is, only on the surface of the first electrode 2 on the substrate 1 side, or on both the front and back surfaces of the first electrode 2. The fine periodic structure 5 may be formed. Among them, the fine periodic structure 5 whose arrangement period is equal to or less than the wavelength of light generated in the organic light emitting layer is formed on the surface of the first electrode 2 on the organic layer 3 side as shown in the figure. It is preferable from the viewpoint of improving visibility and improving light extraction efficiency. Furthermore, it is preferable from the viewpoint of further improving light extraction efficiency that the first electrode, which is a transparent electrode, contains conductive particles that cause light scattering.

In the illustrated example, as the fine periodic structure 5, a plurality of convex portions 6 protruding on the surface of the electrode are arranged in a plurality at a constant pitch, and a fine cycle in which a space between adjacent convex portions 6 and 6 becomes a concave portion 7 having a semicircular cross section. Structure 5 is shown schematically. In this structure, the arrangement period is the distance between the centers of the adjacent concave portions 7 and 7 (or convex portions 6 and 6).

1, the region adjacent to the first electrode 2 on the side opposite to the organic layer 3 is the substrate 1. In addition, the organic layer 3 is usually composed of a plurality of layers including an organic light emitting layer, but the layer adjacent to the first electrode 2 among the plurality of layers constituting the organic layer 3 has a fine periodic structure 5. The organic layer 3a is adjacent to the provided electrode. When the refractive index of the substrate 1 is n1, the refractive index of the first electrode 2 is n2, and the refractive index of the organic layer 3a is n3, when n1 ≦ n3, n1 ≦ n2 ≦ n3 or n2 ≦ n1 The relationship of ≦ n3 is established. Further, when the refractive index of the substrate 1 is n1, the refractive index of the first electrode 2 is n2, and the refractive index of the organic layer 3a is n3, when n3 ≦ n1, n2 ≦ n3 ≦ n1 or n3 ≦ The relationship of n2 ≦ n1 is established.

Thus, by forming the fine periodic structure 5 below the wavelength of light generated in the organic light emitting layer on at least one surface of the first electrode 2 and making the refractive index as described above, The refractive index step between the organic layer 3a adjacent to the one electrode 2 can be inclined. In addition, the fine periodic structure 5 can make it difficult to reflect external light. Therefore, the interface reflection caused by the refractive index step can be reduced, the reflection of external light can be reduced, and both high efficiency of light extraction and improvement of visibility can be achieved.

FIG. 2 shows another example of the layer structure of the organic EL element according to the present invention. In this organic EL element, a light-reflective second electrode 4 is provided on the surface of the substrate 1, and an organic layer 3 including an organic light emitting layer made of an organic electroluminescent material is provided on the surface of the second electrode 4. It is formed by providing a light transmissive first electrode 2 on the surface of the layer 3. The light emitted from the organic layer 3 by applying a voltage between the first electrode 2 and the second electrode 4 passes through the first electrode 2 and is extracted to the outside. Is an organic EL element called a top emission structure in which light is extracted from a transparent electrode on the opposite side of the substrate 1 with the organic layer 3 interposed therebetween without using the substrate 1. One of the first electrode 2 and the second electrode 4 is a positive electrode and the other is a cathode. In the illustrated embodiment, the first electrode 2 is a positive electrode and the second electrode 4 is a cathode. And in the case of the organic EL element of such a structure, in order to solve the said subject, if a refractive index difference in a transparent electrode and an external interface is reduced, reflection can be reduced. Further, by including conductive particles that cause light scattering in the first electrode, which is a transparent electrode, the light extraction efficiency can be improved if the incident angle greater than the critical angle is refracted within the critical angle.

Therefore, in the embodiment of FIG. 2, the arrangement period is equal to or less than the wavelength of light generated in the organic light emitting layer on the surface (external surface) opposite to the organic layer 3 of the first electrode 2 that is the light extraction side electrode, A fine periodic structure 5 having a wavelength equal to or shorter than the wavelength of light incident on the electrode is formed. The fine periodic structure 5 may be provided on at least one surface of the light extraction side electrode. Therefore, it is not limited to the form shown in the figure, and is only on the surface of the first electrode 2 on the organic layer 3 side, that is, only on the surface of the first electrode 2 on the organic layer 3 side, or on both the front and back surfaces of the first electrode 2. The fine periodic structure 5 may be formed. Among them, a fine periodic structure 5 whose arrangement period is equal to or less than the wavelength of light generated in the organic light emitting layer is formed on the surface of the first electrode 2 exposed to the outside opposite to the organic layer 3 as shown in the figure. It is preferable from the viewpoint of improving visibility and improving light extraction efficiency.

In the illustrated example, as in the case of FIG. 1, as the fine periodic structure 5, a plurality of convex portions 6 projecting on the surface of the electrode are arranged at a constant pitch, and the adjacent convex portions 6, 6 have a semicircular cross section. The fine periodic structure 5 which became the recessed part 7 is typically shown. In this structure, the arrangement period is the distance between the centers of the adjacent concave portions 7 and 7 (or convex portions 6 and 6).

In the form of FIG. 2, the area adjacent to the first electrode 2 on the side opposite to the organic layer 3 is the outside (air layer or the like). In addition, the organic layer 3 is usually composed of a plurality of layers including an organic light emitting layer, but the layer adjacent to the first electrode 2 among the plurality of layers constituting the organic layer 3 has a fine periodic structure 5. The organic layer 3a is adjacent to the provided electrode. If the refractive index of the outside (air layer or the like) is n1, the refractive index of the first electrode 2 is n2, and the refractive index of the adjacent organic layer 3a is n3, n1 ≦ n2 ≦ n3 when n1 ≦ n3. Alternatively, the relationship of n2 ≦ n1 ≦ n3 is established. Further, when the refractive index of the outside (air layer or the like) is n1, the refractive index of the first electrode 2 is n2, and the refractive index of the adjacent organic layer 3a is n3, when n3 ≦ n1, n2 ≦ n3 ≦ The relationship of n1 or n3 ≦ n2 ≦ n1 is established.

As described above, the fine periodic structure 5 having a wavelength equal to or smaller than the wavelength of light generated in the organic light emitting layer is formed on at least one surface of the first electrode 2, and the refractive index is set as described above, whereby the light is emitted from the outside. And the refractive index step between the organic layer 3a adjacent to the first electrode 2 can be inclined. Therefore, the interface reflection caused by the refractive index step can be reduced, the reflection of external light can be reduced, and both high efficiency of light extraction and improvement of visibility can be achieved.

Here, the fine periodic structure 5 is a structure in which a fine structure having a fixed shape constituted by an electrode material is periodically arranged as a unit structure. This structure may be a nanometer order structure called a moth-eye structure. That is, it has a structure in which a plurality of cones protruding or recessed are periodically arranged. The fine periodic structure 5 such as the moth-eye structure can incline the refractive index from the incident side to the outgoing side, and thus exhibits a non-reflective function. That is, if the fine periodic structure 5 is provided on the electrode and the refractive index is inclined, the light extraction efficiency can be improved by reducing the reflection at the interface. Reflection of incident light (external light) can also be reduced, the extracted light can be easily seen, and visibility can be improved.

In the fine periodic structure 5, the arrangement period is equal to or less than the wavelength of light generated in the organic light emitting layer. That is, a fine structure having a fixed shape with a pitch having a length equal to or shorter than the wavelength (incident wavelength) of light that is emitted from the organic light emitting layer and is incident on the surface on which the fine periodic structure 5 of the electrode having the fine periodic structure 5 is formed. Are arranged to form the fine periodic structure 5. Since the refractive index cannot be tilted when the arrangement period becomes larger than the incident wavelength, in the fine periodic structure 5, the arrangement period is set to be equal to or less than the incident wavelength. Moreover, it is more preferable that this arrangement period is not more than the wavelength of external light (light from the outside) such as visible light. Thereby, reflection of external light can be reliably reduced. The arrangement period is not particularly limited as long as it is equal to or less than the wavelength of light generated in the organic light emitting layer, but can be, for example, a period (pitch) of about 10 to 1000 nm.

As described above, the fine periodic structure 5 has one or a plurality of concave portions 7 or convex portions 6 on the surface of the first electrode 2 serving as an electrode on the light extraction side so as to have a concave-convex shape in a sectional view. Although formed, the concave portions 7 and the convex portions 6 may be regularly arranged in a predetermined pattern.

FIG. 3 shows an example of the pattern of the fine periodic structure 5. In the illustrated example, a state in which the fine periodic structure 5 is formed on the surface of the first electrode 2 is shown. FIG. 3A shows an example of a striped fine periodic structure 5 in which a plurality of concave portions 7 (or projecting convex portions 6) linearly recessed on the surface of the electrode are arranged in parallel at a constant pitch. FIG. 3B shows an example of the lattice-like fine periodic structure 5 formed by the concave portions 7 (or the protruding convex portions 6) that are recessed in a lattice shape on the surface of the electrode. In the illustrated embodiment, the lattice shape is a grid pattern (a shape in which the unit structure is squared with a plurality of orthogonal linear recesses 7 or projections 6), but other lattice shapes (rectangles and parallelograms). The shape may be a unit structure. FIG. 3C is an example of the concentric fine periodic structure 5 in which a plurality of concave portions 7 (or protruding convex portions 6) that are recessed in a circular shape on the surface of the electrode are arranged concentrically at a constant pitch. . In this embodiment, the diameter of the circle formed by the concave portion 7 or the convex portion 6 increases from the center of the circle toward the outside by a certain amount. The circle may be a perfect circle or an ellipse. FIG. 3 (d) shows an example of a honeycomb-shaped fine periodic structure 5 in which concave portions 7 (or protruding convex portions 6) recessed in a regular hexagonal shape are densely packed in a honeycomb shape on the surface of the electrode. As described above, since the fine periodic structure 5 has a predetermined shape, reflection of light incident on the fine periodic structure 5 can be reduced, light can be extracted more efficiently, and visibility can be improved. It is something that can be done.

FIG. 4 shows another example of the embodiment of the organic EL element. In this form, in the form of FIG. 1, a plurality of convex shapes 8 (or concave shapes 9) are formed on the first electrode 2 side of the substrate 1 in cross-sectional shape. In the illustrated form, a plurality of convex shapes 8 and concave shapes 9 that are larger than the pitch of the arrangement period of the fine periodic structure 5 are alternately arranged at a predetermined pitch. The convex shape 8 or the concave shape 9 may be singular. The convex shape 8 or the concave shape 9 may be formed in a dot shape on the surface of the substrate 1 or may be formed in a linear shape. Further, a composite shape in which the convex shape 8 and the concave shape 9 are combined may be used. Then, as shown in FIG. 4B, which is an enlarged view of the P portion, the first electrode 2 has a fine periodic structure 5 on the organic layer 3 side in which the arrangement period is equal to or less than the wavelength of light generated in the organic light emitting layer. Has been. The fine periodic structure 5 is disposed so as to be inclined with respect to the light emitting surface due to the uneven shape formed on the substrate 1. Thus, by forming the uneven shape on the surface of the substrate 1, it is possible to further reduce the reflection of light incident on the fine periodic structure 5 and achieve both high-efficiency light extraction and improved visibility. It is something that can be done.

In the organic EL element, when the substrate 1 is disposed on the light extraction side, the organic light emitting layer has an arrangement period on at least one surface of the substrate 1, that is, the external surface or the first electrode 2 side. The fine periodic structure 5 which is below the wavelength of the light which arises may be formed. Also in this case, the light extraction efficiency can be improved and the visibility can be improved. When the fine periodic structure 5 is formed on the substrate 1, the first electrode 2 may or may not have the fine periodic structure 5.

The shape of the fine periodic structure 5 when formed on the substrate 1 can be the same as that when formed on the first electrode 2. That is, the fine periodic structure 5 can be formed by providing one or a plurality of concave portions 7 or convex portions 6 on the surface of the substrate 1, and when the surface is viewed in plan, the concave portions 7 or the convex portions 6 are striped. The fine periodic structure 5 can be formed so as to be arranged in any one of a lattice shape, a concentric circle shape, and a honeycomb shape.

The substrate 1 is not particularly limited, and a substrate formed of an appropriate substrate material can be used. However, when light is extracted through the substrate 1, a material that transmits light is used. As the material of the substrate 1, for example, a rigid transparent glass plate such as soda glass or non-alkali glass, a flexible transparent plastic plate such as polycarbonate or polyethylene terephthalate, or the like can be used.

The surface of the substrate 1 may be flat, or as described above, a single or a plurality of convex shapes 8 or concave shapes 9 may be provided in the cross-sectional shape. Examples of the method for forming one or a plurality of convex shapes 8 or concave shapes 9 on the surface of the substrate 1 include a method of directly processing the substrate 1 using lithography using light or an electron beam, but are not limited thereto. It is not a thing.

The refractive index of the substrate 1 is preferably 1.2 to 1.8. In the form of FIG. 1, the refractive index of the substrate 1 is n1. By making the refractive index of the substrate 1 within this range, the above-described refractive index relationship can be easily established. In the form of FIG. 2, the refractive index of the outside (air layer) is n1. Usually, the refractive index of air is about 1.

The first electrode 2 that is an electrode on the light extraction side can be formed of a conductive material. Examples of conductive substances include silver, indium-tin oxide (ITO), indium-zinc oxide (IZO), tin oxide, fine particles of metal such as Au, conductive polymers, conductive organic materials, dopants ( Examples thereof include a donor or acceptor) -containing organic layer, and a mixture of a conductor and a conductive organic material (including a polymer).

The electrode on the light extraction side is preferably formed of a material containing a translucent resin and a fine conductive substance. In that case, when the electrode on the light extraction side that has the fine periodic structure 5 contains a light-transmitting resin and a fine conductive material, conductivity and scattering can be imparted. That is, the fine periodic structure 5 can reduce the interface reflection caused by the refractive index step and the reflection of the external light, and can impart the scattering property to the electrode and the organic light emitting layer of the electrode. The total reflection can be suppressed by scattering the light that is totally reflected between the surface on which the is formed and the region adjacent to the opposite surface. Thereby, it is possible to achieve both high-efficiency light extraction and improved visibility. In addition, it is possible to easily form the fine periodic structure 5 by forming the electrode with a material containing resin.

The fine conductive material preferably has a reflectance of 50% or more. That is, the reflectance of light is 50% or more at the wavelength of light incident on the fine periodic structure 5. In that case, absorption of light by the fine conductive material can be reduced, and furthermore, both high-efficiency light extraction and improved visibility can be achieved.

In addition, it is also preferable that the fine conductive material causes anisotropic scattering. That is, the light incident on the electrode having the fine periodic structure 5 is scattered with anisotropy. In that case, a more effective light extraction effect can be expected because the fine conductive material causes anisotropic scattering. That is, the fine periodic structure 5 can reduce the interface reflection caused by the refractive index step and the reflection of the external light, and can provide an anisotropic light scattering property and the organic light emission of the electrode. It is possible to more effectively suppress the light totally reflected between the side where the layer is formed and the region adjacent to the opposite side. Thereby, highly efficient light extraction and the improvement of visibility can be made compatible further. In order to cause anisotropic scattering, it is preferable that the fine conductive material has an anisotropic shape rather than a spherical shape or the like. For example, anisotropic scattering can be easily caused by using metal nanoparticles having a shape in which the difference between the major axis and the minor axis is large, or metal nanowires in which the metal is nano-sized and formed into a wire.

The fine conductive substance is composed of a conductive material, and the particle diameter is preferably 1 to 100 nm in the case of spherical particles, and 1 to 100 nm in the case of wire-like particles. The aspect ratio is preferably 1 to 100. If the particle size or aspect ratio is out of this range, the light extraction efficiency may deteriorate. The particle diameter can be measured using, for example, a dynamic light scattering photometer (DLS-8000, manufactured by Otsuka Electronics Co., Ltd.).

As the fine conductive material, conductive nanoparticles and conductive nanowires can be used, and for example, metal nanoparticles and metal nanowires are preferably used. And it is preferable to use silver with high reflectance. Among them, it is more preferable to use silver nanowires. In that case, since the fine conductive material is silver nanowire, the reflectance can be increased, anisotropic scattering can be caused, the interface reflection caused by the refractive index step is reduced, and The reflection of external light can be reduced, the absorption by the fine conductive material can be reduced, and the light reflected between the surface on which the organic light emitting layer of the electrode is formed and the region adjacent to the opposite surface can be more It can be effectively suppressed. Thereby, it is possible to further achieve both high-efficiency light extraction and improved visibility.

The fine periodic structure 5 can be formed by lithography using light or electron beam, a method using nanoimprinting, or the like. In particular, nanoimprinting is a simple method for forming a nano-order periodic structure. That is, a concavo-convex structure pattern is formed by pressing and peeling a stamper having a concavo-convex structure of several tens to several hundreds of nanometers processed by an electron beam or the like against a soft resist thin film electrode layer formed on a substrate. It is something that can be done. Dry etching may be used instead of the electron beam. Alternatively, a wet etching process may be used. The stamper is formed on a substrate such as Si or SiO _{2 so} as to have at least one concavo-convex portion by lithography, etching technique, or electron beam direct drawing technique such as FIB. When the fine periodic structure 5 is formed on the substrate 1, this stamper may be used as the substrate 1. The height (or depth) of the irregularities of the fine periodic structure 5 can be, for example, 1 to 1000 nm, or 1 to 100 nm, specifically about 10 nm or 50 nm, but is not limited thereto. It is not a thing.

The electrode disposed on the light extraction side and having the fine periodic structure 5 can be formed by a method of producing a resist thin film to be patterned. For example, a material such as a resin containing a conductive substance can be formed by spin coating, screen printing, dip coating, die coating, casting, spray coating, or gravure coating.

As the resin used for the electrode disposed on the light extraction side and having the fine periodic structure 5, a light transmissive resin is preferably used. For example, acrylic resin, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylate, polycarbonate resin, polyurethane, polyacrylonitrile, polyvinyl acetal, polyamide, polyimide, diacrylphthalate resin, cellulosic resin, Examples thereof include polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, other thermoplastic resins, and two or more copolymers of monomers constituting these resins. Among these, PMMA (polymethyl methacrylate) and polystyrene can be suitably used. The content ratio between the resin and the fine conductive material in the electrode is a volume ratio when the electrode is formed, and can be set, for example, in a range of conductive material: resin = 1: 1 to 1:30. When the content ratio falls within this range, the fine periodic structure 5 can be more easily formed and the light extraction efficiency can be improved.

The arrangement period of the fine periodic structure 5 is less than or equal to the wavelength of light generated in the organic light emitting layer, that is, the incident wavelength or less. Can take. The film thickness of the electrode is not particularly limited, but is preferably in the range of about 0.01 to 1 μm.

Further, the refractive index (n2) of the electrode disposed on the light extraction side where the fine periodic structure 5 is formed is usually in the range of 1.3 to 2.0, but is the same as or higher than the refractive index of the substrate 1. It is preferable to set so as to be smaller. When the refractive index of this electrode is equal to or less than the refractive index of the substrate 1, when light is extracted through the substrate 1, it is possible to reduce the reflection of light incident on the substrate 1 from this electrode, The efficiency of extracting light to the outside is increased.

Examples of the organic EL material for forming the organic light emitting layer in the organic layer 3 include anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, and bisbenzo. Xazoline, bisstyryl, cyclopentadiene, quinoline metal complex, tris (8-hydroxyquinolinato) aluminum complex, tris (4-methyl-8-quinolinato) aluminum complex, tris (5-phenyl-8-quinolinato) aluminum complex, Aminoquinoline metal complex, benzoquinoline metal complex, tri- (p-terphenyl-4-yl) amine, pyran, quinacridone, rubrene, and derivatives thereof, or 1-aryl-2,5-di 2-thienyl) pyrrole derivative, distyryl benzene derivative, styryl arylene derivatives, styrylamine derivatives, and compounds or polymers such having a group consisting of luminescent compounds in a part of molecules. Further, not only compounds derived from fluorescent dyes typified by the above-mentioned compounds, but also so-called phosphorescent materials, for example, luminescent materials such as Ir complexes, Os complexes, Pt complexes, and europium complexes, or compounds or polymers having these in the molecule It can be used suitably. These materials can be appropriately selected and used as necessary.

In addition to the organic light-emitting layer, the organic layer 3 may be provided with layers such as a hole injection layer (hole injection layer), a hole transport layer (hole transport layer), an electron transport layer, and an electron injection layer, as appropriate. Good. Note that these layers as well as the electron injection layer need not be made of an organic material, but will be described as the organic layer 3 here.

Of the organic layer 3, the layer in contact with the electrode on which the fine periodic structure 5 is formed becomes the organic layer 3a. Therefore, when the organic light emitting layer is in contact with the electrode, the organic light emitting layer is the organic layer 3a, but when the layer in contact with the electrode is another layer (for example, a hole transport layer), the layer (for example, the hole transport layer). ) Becomes the organic layer 3a. The refractive index of the organic layer 3a is n3. The refractive index n3 of the organic layer 3a is preferably one greater than n1 and n2, but for example, the range of the refractive index n3 can be set to about 1.4 to 1.8. When the refractive index n3 falls within this range, the light extraction efficiency is further improved.

A second electrode 4 is provided on the side of the organic layer 3 opposite to the first electrode 2. As the material of the second electrode 4, Al or the like can be used. However, a layered structure or the like may be configured by combining Al and another electrode material. Such electrode material combinations include alkali metal and Al laminates, alkali metal and silver laminates, alkali metal halides and Al laminates, and alkali metal oxides and Al laminates. Bodies, laminates of alkaline earth metals and rare earth metals and Al, and alloys of these metal species with other metals, such as sodium, sodium-potassium alloy, lithium, magnesium, etc. For example, a laminate with Al, a magnesium-silver mixture, a magnesium-indium mixture, an aluminum-lithium alloy, a LiF / Al mixture / laminate, an Al / Al ₂ O ₃ mixture, and the like can be given as examples. The materials and forms listed above are examples, and are not limited to these. When taking out light from the 1st electrode 2 side, it is preferable to use a material with good reflectivity. In addition, you may make it take out light from both surfaces (both the 1st electrode 2 side and the 2nd electrode 4 side), and it is preferable to use the light transmissive material for the 2nd electrode 4 in that case.

The method for producing the organic EL element is not particularly limited, and can be produced by a usual method. That is, it can be formed by sequentially laminating each layer on the surface of the substrate 1 by an appropriate coating method or vapor deposition method. Finally, you may seal with a sealing cap etc.

[Production of element]
Example 1
As the substrate 1, an alkali-free glass plate (“No. 1737” manufactured by Corning) was used. The refractive index (n1) of the substrate 1 at a wavelength of 500 nm is 1.50 to 1.53. In addition, about the refractive index, it measured by FilmTek by SCI (The following refractive index measurement is also the same).

The same substrate as the above-mentioned substrate 1 was used as a stamper substrate. On the surface of this stamper substrate, a triangular shape (inverted V-shape) having a stripe shape in which a plurality of straight lines are arranged with a center-to-center pitch of about 300 nm in plan view and a cross-sectional shape of about 200 nm in width (base) and about 50 nm in height. A structure having a plurality of convex portions was formed by a wet etching process to produce a stamper.

As a solution for the first electrode 2 formed on the substrate 1, an ITO nanoparticle solution (particle diameter: about 40 nm, NanoTek (registered trademark) ITCW 15 wt% -G30 manufactured by C-I Kasei Co., Ltd.), polymethyl methacrylate (PMMA, manufactured by Aldrich) 10 wt% acetone solution in which is dispersed in a volume ratio of ITO nanoparticles: PMMA = 1: 8. PMMA is a resin having translucency. This solution was applied on the substrate 1 by spin coating so as to have a film thickness of 100 nm and heated to 100 ° C. This produced the electrode formation layer. The produced electrode forming layer (first electrode 2) had a refractive index (n2) of about 1.49 at a wavelength of 500 nm.

Then, the surface of the substrate 1 on which the electrode forming layer is formed and the surface on which the stamper pattern is formed are opposed to each other, the stamper is stacked on the substrate 1, pressed at a pressure of 5 to 10 MPa, held for 1 minute, and then the stamper is removed. It peeled. Thereby, the planar view has a fine periodic structure 5 in which a plurality of concave portions 7 having a stripe shape composed of a plurality of straight lines and a plurality of inverted triangular shapes (V-shaped) in cross section are arranged at an arrangement period of about 300 nm. A first electrode 2 was formed. The first electrode 2 becomes a positive electrode. Further, the arrangement period (300 nm) of the fine periodic structure is smaller than the wavelength of 500 nm of light generated in the organic light emitting layer described below.

The surface of the substrate 1 on which the first electrode 2 was formed was subjected to UV-O ₃ treatment for 5 minutes. Thereafter, the substrate 1 is set in a vacuum deposition apparatus, and N, N-diphenyl-N, N-bis (1-naphthyl) -1,1′-biphenyl-4,4′-diamine (NPB) is used as a hole transport layer. (Manufactured by eRay) was formed on the first electrode 2 with a film thickness of 40 nm. This hole transport layer becomes the organic layer 3a adjacent to the first electrode 2, and the refractive index (n3) at a wavelength of 500 nm of this hole transport layer is 1.7 to 1.8. Further, on this hole transport layer, aluminum-tris (8-hydroxyquinoline) (Alq) (manufactured by eRay) was formed to a thickness of 60 nm as an organic light emitting layer that also served as an electron transport layer. Further, LiF (manufactured by High Purity Chemical Co., Ltd.) was formed with a thickness of 1 nm as an electron injection layer on the organic light emitting layer. Finally, as the second electrode 4 serving as a cathode on the electron injection layer, Al (manufactured by High-Purity Chemical Co., Ltd.) having a thickness of 80 nm was formed by vacuum deposition.

After vacuum deposition, the substrate 1 on which each layer was formed was transported to a glove box in a dry nitrogen atmosphere having a dew point of −80 ° C. or less without being exposed to the air. On the other hand, a water absorbing agent (manufactured by Dynic) was attached to a glass sealing cap, and an ultraviolet curable resin sealing agent was applied to the outer periphery of the sealing cap in advance. And each layer was sealed with the sealing cap by sticking the sealing cap on the board | substrate 1 with the sealing agent so that each layer might be enclosed in a glove box, and irradiating with an ultraviolet-ray and hardening a sealing agent.

Thus, an organic EL element having a layer structure as shown in FIG. 1 and having the fine periodic structure 5 formed on the first electrode 2 and the refractive index relationship n2 <n1 <n3 was obtained.

(Example 2)
As a material for the first electrode 2, silver nanoparticles: PMMA solution in which silver nanoparticles (particle diameter of about 40 nm, reflectance 90% or more) and PMMA were dispersed in the same mass ratio and solvent as in Example 1 was used. The film thickness of the first electrode 2 was 100 nm. The refractive index (n2) of the manufactured first electrode 2 was about 1.49 at a wavelength of 500 nm. Other than that was carried out similarly to Example 1, and obtained the organic EL element of the layer structure like FIG.

(Example 3)
Silver nanowire: PMMA solution in which silver nanowire (diameter: about 50 nm, length: about 5 μm, reflectance: 90% or more) and PMMA are dispersed in the same mass ratio and solvent as the material of the first electrode 2 It was used. The silver nanowire is prepared according to a known paper “Materials Chemistry and Physics vol. 114 p333-338“ Preparation of Ag nanorods with high yield by polyolprocess ””, and has an average diameter of 50 nm and an average length of 5 μm. The film thickness of the first electrode 2 was 100 nm. The refractive index (n2) of the manufactured first electrode 2 was about 1.49 at a wavelength of 500 nm. Other than that was carried out similarly to Example 1, and obtained the organic EL element of the layer structure like FIG.

Example 4
Silver nanowires in which silver nanowires (diameter: about 50 nm, length: about 5 μm, reflectance: 90% or more) and polystyrene (PS) are dispersed in the same mass ratio and solvent as the material of the first electrode 2. : PS solution was used. The silver nanowire is prepared according to a known paper “Materials Chemistry and Physics vol. 114 p333-338“ Preparation of Ag nanorods with high yield by polyolprocess ””, and has an average diameter of 50 nm and an average length of 5 μm. Polystyrene is a translucent resin. The film thickness of the first electrode 2 was 100 nm. The refractive index (n2) of the manufactured first electrode 2 was 1.58 at a wavelength of 500 nm. Other than that was carried out similarly to Example 1, and obtained the organic EL element which is a layer structure like FIG. 1, and whose refractive index relationship is n1 <n2 <n3.

(Example 5)
Using the stamper used in Example 1 as the substrate 1 (refractive index n1 = 1.50 to 1.53), the first electrode 2 was formed directly on the fine periodic structure of the stamper in the same manner as in Example 1. Thereby, the fine periodic structure 5 was formed at the interface of the first electrode 2 on the substrate 1 side. Then, UV-O ₃ treatment was performed for 5 minutes on the surface of the substrate 1 on which the first electrode 2 was formed. Thereafter, the substrate 1 is set in a vacuum deposition apparatus, and N, N-diphenyl-N, N-bis (1-naphthyl) -1,1′-biphenyl-4,4′-diamine (NPB) is used as a hole transport layer. (Manufactured by eRay) was formed on the first electrode 2 with a film thickness of 40 nm. Otherwise, an organic EL device was obtained in the same manner as in Example 1.

(Example 6)
Using the stamper used in Example 1 as the substrate 1 (refractive index n1 = 1.50 to 1.53), the first electrode 2 was formed directly on the fine periodic structure of the stamper in the same manner as in Example 1. Then, a fine periodic structure 5 was formed on the surface of the first electrode 2 by a stamper in the same manner as in Example 1. Thereby, the fine periodic structure 5 was formed on both surfaces of the first electrode 2. Thereafter, the substrate 1 is set in a vacuum deposition apparatus, and N, N-diphenyl-N, N-bis (1-naphthyl) -1,1′-biphenyl-4,4′-diamine (NPB) is used as a hole transport layer. (Manufactured by eRay) was formed on the first electrode 2 with a film thickness of 40 nm. Otherwise, an organic EL device was obtained in the same manner as in Example 1.

(Example 7)
The stamper used in Example 1 was used as the substrate 1 (refractive index n1 = 1.50 to 1.53), and the first electrode 2 was formed on the surface of the stamper opposite to the unevenness forming side. Thereafter, the substrate 1 is set in a vacuum deposition apparatus, and N, N-diphenyl-N, N-bis (1-naphthyl) -1,1′-biphenyl-4,4′-diamine (NPB) is used as a hole transport layer. (Manufactured by eRay) was formed on the first electrode 2 with a film thickness of 40 nm. Otherwise, an organic EL device was obtained in the same manner as in Example 1.

(Comparative Example 1)
An ITO film (100 nm) was sputtered on the surface of the glass substrate 1 used in Example 1 to form a first electrode 2. The refractive index of this ITO film at a wavelength of 500 nm was 2.0. Then, a hole transport layer, an organic light emitting layer, an electron injection layer, and an electrode (cathode) were formed on the first electrode 2 by the same material and method as in Example 1, and finally sealed with a sealing cap. . As a result, an organic EL element having a refractive index relationship of n1 <n3 <n2 was obtained.

(Comparative Example 2)
An ITO film (100 nm) was sputtered on the surface of the glass substrate 1 used in Example 1 to form the first electrode 2. Further, a fine periodic structure was formed on the surface of the first electrode 2 by the stamper used in Example 1. The refractive index (n2) of the first electrode 2 was about 2.0 at a wavelength of 500 nm. Then, a hole transport layer, an organic light emitting layer, an electron injection layer, and an electrode (cathode) were formed on the first electrode 2 by the same material and method as in Example 1. As a result, an organic EL element having a refractive index relationship of n1 <n3 <n2 was obtained.

(Example 8)
As the substrate 1, a transparent resin substrate formed of an epoxy resin was used. The refractive index (n1) of the substrate 1 at a wavelength of 500 nm is about 1.60.

Next, a first electrode 2 having a refractive index (n2) of about 1.49 is formed on the substrate 1 in the same manner as in the first embodiment, and the first periodic electrode 5 having the fine periodic structure 5 is formed by the stamper used in the first embodiment. One electrode 2 was formed. Then, after UV-O ₃ treatment was performed on the surface on which the first electrode 2 was formed, polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT-PSS) (“Clevios (registered trademark) P AI4083 manufactured by Starck Vitech) , PEDOT: PSS = 1: 6) was applied by a spin coater so as to have a film thickness of 30 nm, and baked at 100 ° C. for 10 minutes to prepare a hole injection layer. The refractive index (n3) of this hole injection layer at a wavelength of 500 nm was 1.55.

Thereafter, a hole transport layer, an organic light emitting layer, an electron injection layer, and a second electrode 4 were formed in this order on the surface of the hole injection layer in the same manner as in Example 1.

Thus, an organic EL element having a layer structure as shown in FIG. 1 and the fine periodic structure 5 formed on the first electrode 2 and the refractive index relationship n2 <n3 <n1 was obtained.

Example 9
As a material for the first electrode 2, silver nanoparticles: PMMA solution in which silver nanoparticles (particle diameter of about 40 nm, reflectance 90% or more) and PMMA were dispersed in the same mass ratio and solvent as in Example 1 was used. The film thickness of the first electrode 2 was 100 nm. The refractive index (n2) of the manufactured first electrode 2 was about 1.49 at a wavelength of 500 nm. Other than that was carried out similarly to Example 8, and obtained the organic EL element of a layer structure like FIG.

(Example 10)
Silver nanowire: PMMA solution in which silver nanowire (diameter: about 50 nm, length: about 5 μm, reflectance: 90% or more) and PMMA are dispersed in the same mass ratio and solvent as the material of the first electrode 2 It was used. The silver nanowire is prepared according to a known paper “Materials Chemistry and Physics vol. 114 p333-338“ Preparation of Ag nanorods with high yield by polyolprocess ””, and has an average diameter of 50 nm and an average length of 5 μm. The film thickness of the first electrode 2 was 100 nm. The refractive index (n2) of the manufactured first electrode 2 was about 1.49 at a wavelength of 500 nm. Other than that was carried out similarly to Example 8, and obtained the organic EL element of a layer structure like FIG.

(Example 11)
Silver nanowires in which silver nanowires (diameter: about 50 nm, length: about 5 μm, reflectance: 90% or more) and polystyrene (PS) are dispersed in the same mass ratio and solvent as the material of the first electrode 2. : PS solution was used. The silver nanowire is prepared according to a known paper “Materials Chemistry and Physics vol. 114 p333-338“ Preparation of Ag nanorods with high yield by polyolprocess ””, and has an average diameter of 50 nm and an average length of 5 μm. Polystyrene is a translucent resin. The film thickness of the first electrode 2 was 100 nm. The refractive index (n2) of the manufactured first electrode 2 was 1.58 at a wavelength of 500 nm. Other than that was carried out similarly to Example 8, and obtained the organic EL element by the layer structure like FIG. 1, and the relationship of refractive index n3 <n2 <n1.

(Example 12)
A bisphenol A + hexamethylenediamine solution was applied to the surface of the substrate 1 (resin substrate) used in Example 8 by a spin coating method so as to have a film thickness of 100 nm and heated to 80 ° C. A fine periodic structure 5 was formed on the surface of the substrate 1 by the stamper used in Example 1.

The first electrode 2 (refractive index n2 = about 1.49) was formed in the same manner as in Example 1 directly on the fine periodic structure of the substrate 1 (refractive index n1 = about 1.60). Thereby, the fine periodic structure 5 was formed at the interface of the first electrode 2 on the substrate 1 side. Then, UV-O ₃ treatment was performed for 5 minutes on the surface of the substrate 1 on which the first electrode 2 was formed. Otherwise, in the same manner as in Example 8, a hole injection layer (refractive index n3 = 1.55), a hole transport layer, an organic light emitting layer, an electron injection layer, and a second electrode are formed on the surface of the first electrode 2. 4 were formed in order. Thus, an organic EL element having a layer configuration as shown in FIG. 1 and a refractive index relationship of n2 <n3 <n1 was obtained.

(Example 13)
The first electrode 2 (refractive index n2 = about 1.49) is directly formed on the fine periodic structure of the substrate 1 (refractive index n1 = about 1.60) having the fine periodic structure 5 manufactured in the example 12. Formed in the same manner. Then, a fine periodic structure 5 was formed on the surface of the first electrode 2 by a stamper in the same manner as in Example 1. Thereby, the fine periodic structure 5 was formed on both surfaces of the first electrode 2. Otherwise, in the same manner as in Example 8, a hole injection layer (refractive index n3 = 1.55), a hole transport layer, an organic light emitting layer, an electron injection layer, and a second electrode are formed on the surface of the first electrode 2. 4 were formed in order. Thus, an organic EL element having a layer configuration as shown in FIG. 1 and a refractive index relationship of n2 <n3 <n1 was obtained.

(Example 14)
A first electrode 2 (refractive index n2 = about 1.49) was formed on the surface opposite to the unevenness forming side of the substrate 1 (refractive index n1 = about 1.60) having the fine periodic structure 5 manufactured in Example 12. . Otherwise, in the same manner as in Example 8, a hole injection layer (refractive index n3 = 1.55), a hole transport layer, an organic light emitting layer, an electron injection layer, and a second electrode are formed on the surface of the first electrode 2. 4 were formed in order. Thus, an organic EL element having a layer configuration as shown in FIG. 1 and a refractive index relationship of n2 <n3 <n1 was obtained. Otherwise, an organic EL device was obtained in the same manner as in Example 1.

(Comparative Example 3)
An ITO film (100 nm) was sputtered on the surface of the resin substrate 1 used in Example 8 to form the first electrode 2. The refractive index of this ITO film at a wavelength of 500 nm was 2.0. Then, a hole injection layer, a hole transport layer, an organic light emitting layer, an electron injection layer, and a second electrode 4 are sequentially formed on the first electrode 2 by the same material and method as in Example 8. Finally, Sealed with a sealing cap. As a result, an organic EL element having a refractive index relationship of n3 <n1 <n2 was obtained.

(Comparative Example 4)
An ITO film (100 nm) was sputtered on the surface of the resin substrate 1 used in Example 8 to form the first electrode 2. Further, a fine periodic structure was formed on the surface of the first electrode 2 by the stamper used in Example 1. The refractive index (n2) of the first electrode 2 was about 2.0 at a wavelength of 500 nm. Then, a hole injection layer, a hole transport layer, an organic light emitting layer, an electron injection layer, and a second electrode 4 were sequentially formed on the first electrode 2 by the same material and method as in Example 8. As a result, an organic EL element having a refractive index relationship of n3 <n1 <n2 was obtained.

[Measurement]
A voltage was applied to each organic EL element, and quantum efficiency (light extraction efficiency) was measured by a conventional method. In Examples 1 to 7, the quantum efficiency ratio was calculated when the quantum efficiency of Comparative Example 1 was used as the reference (1.0). In Examples 8 to 14, the quantum efficiency ratio was calculated when the quantum efficiency of Comparative Example 3 was used as the reference (1.0).

[result]
The results are shown in Tables 1 and 2.

As can be seen from Table 1, the elements of Examples 1 to 7 are of Comparative Example 1 in which electrodes having conductive fine particles and having a fine periodic structure 5 are not formed, and the relationship between the refractive indexes is n1 <n3 <n2. It was confirmed that the light extraction efficiency was improved with respect to Comparative Example 2 as described above. In the devices of Examples 1 to 7, reflection of external light was suppressed, and light emission was easily visible. Further, it was confirmed that the light extraction efficiency of the elements of Examples 2 to 3 using silver having high reflectivity as the conductive material was improved as compared with Example 1. Furthermore, it was confirmed that the device of Example 3 using silver nanowires as the conductive material had improved light extraction efficiency compared to Example 2. Further, in Example 6 having the fine periodic structure 5 at both interfaces of the first electrode 2, reflection of external light is further suppressed and light emission is visually recognized as compared with Examples 1 and 5 in which only one interface is provided. It was easy.

Further, as can be seen from Table 2, the elements of Examples 8 to 14 are those in which Comparative Example 3 in which an electrode having conductive fine particles and having a fine periodic structure 5 is not formed, and the refractive index relationship is n3 <n1. It was confirmed that the light extraction efficiency was improved with respect to Comparative Example 4 where <n2. In the devices of Examples 8 to 14, reflection of external light was suppressed, and light emission was easily visible. In addition, it was confirmed that the light extraction efficiency of the elements of Examples 9 to 10 using silver having high reflectivity as the conductive material was improved as compared with Example 8. Furthermore, it was confirmed that the device of Example 10 using silver nanowires as the conductive material had improved light extraction efficiency compared to Example 9. Further, in Example 13 having the fine periodic structure 5 at both interfaces of the first electrode 2, reflection of external light is further suppressed and light emission is easy to visually recognize as compared with Example 8 having only one interface. Met.

 

 

 

 

DESCRIPTION OF SYMBOLS 1 Substrate 2 1st electrode 3 Organic layer 4 2nd electrode 5 Fine periodic structure 6 Convex part 7 Concave part 8 Convex form 9 Concave form

Claims (8)

An organic EL element including a pair of electrodes and an organic layer having at least one organic light emitting layer, on at least one surface of an electrode on the light extraction side or at least one surface of a substrate disposed on the light extraction side A fine periodic structure having an arrangement period equal to or less than a wavelength of light generated in the organic light emitting layer is formed, and a refractive index of a region adjacent to the light extraction side electrode on the side opposite to the organic layer is n1, and the light extraction is performed When the refractive index of the side electrode is n2 and the refractive index of the organic layer adjacent to the light extraction side electrode is n3, the relationship of n1 ≦ n2 ≦ n3 or n2 ≦ n1 ≦ n3 is established. Organic EL element to be used. An organic EL element including a pair of electrodes and an organic layer having at least one organic light emitting layer, on at least one surface of an electrode on the light extraction side or at least one surface of a substrate disposed on the light extraction side A fine periodic structure having an arrangement period equal to or less than a wavelength of light generated in the organic light emitting layer is formed, and a refractive index of a region adjacent to the light extraction side electrode on the side opposite to the organic layer is n1, and the light extraction is performed When the refractive index of the side electrode is n2 and the refractive index of the organic layer adjacent to the light extraction side electrode is n3, the relationship of n2 ≦ n3 ≦ n1 or n3 ≦ n2 ≦ n1 is established. Organic EL element to be used. 3. The organic EL element according to claim 1, wherein the light extraction side electrode includes a light-transmitting resin and a fine conductive material. 4. The organic EL device according to claim 3, wherein the fine conductive material has a reflectance of 50% or more. The organic EL device according to claim 3 or 4, wherein the fine conductive substance causes anisotropic scattering. 6. The organic EL device according to claim 3, wherein the fine conductive material is a silver nanowire. The fine electrode structure is characterized in that the electrode on the light extraction side or the substrate disposed on the light extraction side has a single or a plurality of concave portions or convex portions on the surface to form a fine periodic structure. Organic EL element of any one of these. The light extraction side electrode or the substrate disposed on the light extraction side has a concave portion or a convex portion on the surface, and when viewed in plan, the concave portion or the convex portion is a stripe shape, a lattice shape, a concentric circle shape, and The organic EL element according to any one of claims 1 to 7, wherein a fine periodic structure is formed by being arranged in any shape of a honeycomb.

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