Organic electroluminescent element

1. An organic electroluminescent element comprising a transparent substrate and provided thereon, at least a first electrode section with a light transmission property, an organic light emission layer section and a second electrode section in that order, the first electrode section containing at least metal nanowires, wherein an average refractive index of the first electrode section is lower than that of the organic light emission layer section;

wherein when the first electrode section is divided in a first electrode part and a second electrode part having the same thickness, the first electrode part being close to the organic light emission layer section and the second electrode part close to the transparent substrate, the following formula is satisfied:

N1s<N1el

wherein N1el represents an average refractive index of the first electrode part; and N1s represents an average refractive index of the second electrode part.

2. The organic electroluminescent element of claim 1 , wherein the first electrode section further contains at least a first transparent resin component and a second transparent resin component having a refractive index higher than that of the first transparent resin component, in which the second transparent resin component and the metal nanowires are contained in a large amount in a first portion of the first electrode section close to the organic light emission layer section and the first transparent resin component is contained in a large amount in a second portion of the first electrode section close to the transparent substrate.

3. The organic electroluminescent element of claim 2 , wherein the second transparent resin component is a transparent conductive polymer.

4. The organic electroluminescent element of claim 1 , wherein the first electrode section further contains at least a first transparent resin component and a transparent inorganic component having a refractive index higher than that of the first transparent resin component, in which the transparent inorganic component and the metal nanowires are contained in a large amount in a first portion of the first electrode section close to the organic light emission layer section and the first transparent resin component is contained in a large amount in a second portion of the first electrode section close to the transparent substrate.

5. The organic electroluminescent element of claim 4 , wherein the transparent inorganic component is a transparent conductive metal oxide.

6. The organic electroluminescent element of claim 1 , wherein the second electrode section is an electrode composed of a metal.

7. The organic electroluminescent element of claim 1 , wherein the total optical transmittance of the first electrode section is at least 60%.

8. The organic electroluminescent element of claim 1 , wherein a metal composition of the metal nanowires contains silver.

9. The organic electroluminescent element of claim 2 , wherein the second transparent resin component is a conductive polymer.

10. The organic electroluminescent element of claim 9 , wherein the conductive polymer is selected from the group consisting of derivatives of polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polyphenyl acetylene and polynaphthalene.

11. The organic electroluminescent element of claim 4 , wherein the transparent inorganic component is a transparent conductive metal oxide.

12. The organic electroluminescent element of claim 11 , wherein the transparent conductive metal oxide is selected from particles of ZrO 2 , CeO 2 , ZnO, TiO 2 , SnO 2 , Al 2 O 3 , In 2 O 3 , SiO 2 , MgO, BaO, MoO 2 and V 2 O 5 ; their composite oxide particles; composite metal oxide particles doped with different kinds of atoms; and their metal oxide sol.

13. An organic electroluminescent element comprising a transparent substrate and provided thereon, at least a first electrode section with a light transmission property, an organic light emission layer section and a second electrode section in that order, the first electrode section containing at least metal nanowires, wherein an average refractive index of the first electrode section is lower than that of the organic light emission layer section;

wherein the first electrode section further contains at least a first transparent resin component and a second transparent resin component having a refractive index higher than that of the first transparent resin component, in which the second transparent resin component and the metal nanowires are contained in a large amount in a first portion of the first electrode section close to the organic light emission layer section and the first transparent resin component is contained in a large amount in a second portion of the first electrode section close to the transparent substrate; and

wherein microparticles are incorporated in a portion where the first transparent resin component is contained.

14. An organic electroluminescent element comprising a transparent substrate and provided thereon, at least a first electrode section with a light transmission property, an organic light emission layer section and a second electrode section in that order, the first electrode section containing at least metal nanowires, wherein an average refractive index of the first electrode section is lower than that of the organic light emission layer section;

wherein the first electrode section further contains at least a first transparent resin component and a transparent inorganic component having a refractive index higher than that of the first transparent resin component, in which the transparent inorganic component and the metal nanowires are contained in a large amount in a first portion of the first electrode section close to the organic light emission layer section and the first transparent resin component is contained in a large amount in a second portion of the first electrode section close to the transparent substrate; and

wherein microparticles are contained in a portion where the first transparent resin component is contained.

15. An organic electroluminescent element comprising a transparent substrate and provided thereon, at least a first electrode section with a light transmission property, an organic light emission layer section and a second electrode section in that order, the first electrode section containing at least metal nanowires, wherein an average refractive index of the first electrode section is lower than that of the organic light emission layer section;

wherein the thickness of the first electrode section is at most 10 μm.

16. An organic electroluminescent element comprising a transparent substrate and provided thereon, at least a first electrode section with a light transmission property, an organic light emission layer section and a second electrode section in that order, the first electrode section containing at least metal nanowires, wherein an average refractive index of the first electrode section is lower than that of the organic light emission layer section;

wherein the first electrode section further contains at least a first transparent resin component and a second transparent resin component having a refractive index higher than that of the first transparent resin component, in which the second transparent resin component and the metal nanowires are contained in a large amount in a first portion of the first electrode section close to the organic light emission layer section and the first transparent resin component is contained in a large amount in a second portion of the first electrode section close to the transparent substrate;

wherein microparticles are incorporated in a portion where the first transparent resin component is contained;

wherein the microparticles are selected from the group consisting of cross-linked acryl resin microparticles, cross-linked styrene resin microparticles, silica microparticles, melamine/formaldehyde resin microparticles, and their composite microparticles.