Wiring substrate and display device

1. A display device comprising:

a first insulation layer which is disposed on a substrate with a first refractive index and has a second refractive index which differs from the first refractive index;

a second insulation layer which is disposed on the first insulation layer and has a third refractive index which differs from the second refractive index; and

a plurality of kinds of display elements generate lights of different wavelengths, and have a refractive index which is substantially equal to the second refractive index,

wherein at least one kind of display element is put in contact with the first insulation layer via an opening portion that penetrates the second insulation layer.

2. The display device according to claim 1 , wherein the display element, which is put in contact with the first insulation layer, generates light of a blue wavelength.

3. The display device according to claim 1 , wherein the second refractive index is higher than the first refractive index and the third refractive index.

4. The display device according to claim 1 , wherein the first insulation layer is formed of multiple layers including a silicon nitride film.

5. The display device according to claim 1 , wherein the display element includes a first electrode which is formed in an insular shape and has light transmissivity, a second electrode which is disposed to be opposed to the first electrode, and an optical active layer which is held between the first electrode and the second electrode.

6. The display device according to claim 1 , wherein the display device includes a plurality of thin-film transistors which are formed on the substrate.

7. A display device comprising:

a substrate having a surface layer;

an insulation layer which is disposed in contact with the surface layer of the substrate; and

a plurality of kinds of display elements which are disposed on the substrate and generate lights of different wavelengths, wherein a relationship,

| n 1 −n 3 |<|n 2 −n 3|

is established, where n 1 is a refractive index of the surface layer of the substrate, n 2 is a refractive index of the insulation layer, and n 3 is a refractive index of a layer of the display element, which is located on the substrate side, and

at least one kind of display element is disposed in contact with the surface layer of the substrate.

8. The display device according to claim 7 , wherein a first display element which generates light of a first wavelength is disposed in contact with the insulation layer, and

a second display element, which generates light of a second wavelength that is different from the first wavelength, is disposed in contact with the surface layer of the substrate without intervention of the insulation film.

9. The display device according to claim 7 , wherein a first display element, which generates light of a first wavelength, and a second display element, which generates light of a second wavelength that is different from the first wavelength, are disposed in contact with the surface layer of the substrate without intervention of the insulation film.

10. A display device comprising:

a substrate having a surface layer;

an insulation layer which is disposed in contact with the surface layer of the substrate; and

a display element which is disposed on the substrate and generates light,

wherein a relationship,

| n 1 −n 3 |<|n 2 −n 3|

is established, where n 1 is a refractive index of the surface layer of the substrate, n 2 is a refractive index of the insulation layer, and n 3 is a refractive index of a layer of the display element, which is located on the substrate side, and

the display element is disposed in contact with the surface layer of the substrate without intervention of the insulation film.