Electroluminescence element and display device using the same

• US 20070114523A1
• Filed: 11/02/2006
• Published: 05/24/2007
• Est. Priority Date: 11/18/2005
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Oumi, Manabu, Yamamoto, Shuhei, Suda, Masayuki, Senbonmatsu, Shigeru, Suginoya, Mitsuru
• Granted Patent: US 7,952,272 B2
• Time in Patent Office: Days
• US Class Current: 257/40
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C03C 17/3628 one layer at least containing a sulfide
• CPC Class Codes: C03C 17/3649 made of metals other than silver
• CPC Class Codes: C03C 2217/45 Inorganic continuous phases
• CPC Class Codes: C03C 2217/479 Metals
• CPC Class Codes: C03C 2217/48 having a specific function
• CPC Class Codes: H10K 2102/331 Nanoparticles used in non-emissive layers, e.g. in packaging layer
• CPC Class Codes: H10K 50/854 comprising scattering means
• CPC Class Codes: H10K 59/35 comprising red-green-blue [RGB] subpixels
• CPC Class Codes: H10K 59/877 comprising scattering means

Abstract

In an EL element including a light emitting layer sandwiched between upper and lower electrodes, of light emitted therefrom, light totally reflected at a light emitting layer interface is not taken out, so there is a problem in that light emission efficiency reduces. Therefore, a light scattering layer in which metal particles are dispersed is provided between an electrode and the light emitting layer. According to such a structure, the light from the light emitting layer can be scattered by the metal particles and taken out, thereby improving the light emission efficiency. When plasmon is excited in the metal particles, light confined in the light emitting layer or each layer adjacent thereto can be used, thereby improving light use efficiency.

Claims

1. An electroluminescence element, comprising:

a first electrode layer;

a second electrode layer;

a light emitting layer provided between the first electrode layer and the second electrode layer; and

a light scattering layer, which is located between the first electrode layer and the light emitting layer, including dispersed metal particles.

2. An electroluminescence element according to claim 1, further comprising a second light scattering layer provided between the second electrode layer and the light emitting layer.

3. An electroluminescence element according to claim 1, the light scattering layer is located on the second electrode layer.

4. An electroluminescence element according to claim 1, wherein the light scattering layer comprises a film in which the metal particles, each having a particle diameter in a range of 1 nm to 300 nm, are disposed in a dielectric material.

5. An electroluminescence element according to claim 1, wherein the light scattering layer comprises a film in which the metal particles, which have different ratios of a minor axis to a major axis, are disposed in a dielectric material.

6. An electroluminescence element according to claims 1, wherein each of the metal particles has a particle diameter substantially equal to a thickness of the light scattering layer.

7. An electroluminescence element according to claim 1, wherein each of the metal particles comprises a core portion which is substantially spherical and contains a dielectric material and a metal thin film formed on a surface of the core portion.

8. An electroluminescence element according to claim 7, wherein the light scattering layer comprises multiple kinds of metal particles, in each of which the core portion and the metal thin film are different in size.

9. An electroluminescence element according to claim 1, wherein each of the metal particles comprises a cluster in which a plurality of particles are coagulated.

10. An electroluminescence element according to claim 1, wherein:

at least one of the first electrode layer and the second electrode layer comprises a plurality of electrodes separated from one another and a pixel is provided in a stack portion in which the first electrode layer and the second electrode layer overlap each other; and

the light scattering layer comprises a first light scattering region corresponding to a first pixel and a second light scattering region corresponding to a second pixel and scattered light emitted from the first light scattering region has a wavelength characteristic different from a wavelength characteristic of scattered light emitted from the second light scattering region.

11. An electroluminescence element according to claim 1, wherein:

at least one of the first electrode layer and the second electrode layer comprises a plurality of electrodes separated from one another and a pixel is provided in a stack portion in which the first electrode layer and the second electrode layer overlap each other; and

a first light scattering region corresponding to a first pixel in the light scattering layer has the metal particles different in shape from the metal particles of a second light scattering region corresponding to a second pixel.

12. An electroluminescence element according to claim 1, wherein:

at least one of the first electrode layer and the second electrode layer comprises a plurality of electrodes separated from one another and a pixel is provided in a stack portion in which the first electrode layer and the second electrode layer overlap each other;

the light scattering layer comprises a first dielectric layer and a second dielectric layer; and

the first dielectric layer including a first light scattering region corresponding to a first pixel in the light scattering layer has a permittivity different from a permittivity of the second dielectric layer including a second light scattering region corresponding to a second pixel.

13. An electroluminescence element according to claim 1, further comprising a dielectric layer provided between the light emitting layer and the light scattering layer, wherein:

at least one of the first electrode layer and the second electrode layer comprises a plurality of electrodes separated from one another and a pixel is provided in a stack portion in which the first electrode layer and the second electrode layer overlap each other;

the light scattering layer comprises a first light scattering region corresponding to a first pixel and a second light scattering region corresponding to a second pixel; and

the dielectric layer has a film thickness changed between a portion corresponding to the first light scattering region and a portion corresponding to the second light scattering region.

14. An electroluminescence element according to claim 11,

wherein an average particle diameter of metal particles included in the second light scattering region is larger than an average particle diameter of metal particles included in the first light scattering region.

15. An electroluminescence element according to claim 11, wherein when a ratio of a minor axis of each of the metal particles to a major axis thereof is expressed as a shape ratio, an average shape ratio of metal particles included in the second light scattering region is larger than an average shape ratio of metal particles included in the first light scattering region.

16. An electroluminescence element according to claim 11, wherein:

each of the metal particles includes a structure in which a metal thin film is formed on a surface of a substantially spherical core portion containing a dielectric material; and

the core portion and the metal thin film of each of the metal particles are different in size between the first light scattering region and the second light scattering region.

17. An electroluminescence element according to claim 1, wherein:

at least one of the first electrode layer and the second electrode layer is divided into parts corresponding to three primary colors and a first pixel, a second pixel, and a third pixel are provided in a stack portion in which the first electrode layer and the second electrode layer overlap each other;

the light scattering layer comprises a first light scattering region corresponding to the first pixel, a second light scattering region corresponding to the second pixel, and a third light scattering region corresponding to the third pixel; and

a size of each of metal particles dispersed in the first light scattering region is in a range of 10 nm to 50 nm, a size of each of metal particles dispersed in the second light scattering region is in a range of 50 nm to 90 nm, and a size of each of metal particles dispersed in the third light scattering region is in a range of 90 nm to 140 nm.

18. An electroluminescence element according to claim 1, wherein each of the metal particles comprises one selected from the group consisting of Au, Ag, Pt, Co, W, and an alloy thereof.

19. An electroluminescence element according to claim 1, wherein each of the metal particles comprises a particle in which plasmon is excited.

20. A display device, comprising:

an electroluminescence element including a first electrode layer, a second electrode layer, a light emitting layer provided between the first electrode layer and the second electrode layer, and a light scattering layer which is provided between the first electrode layer and the light emitting layer and contains dispersed metal particles; and

a non-self light emitting display element provided on a light emitting surface side of the electroluminescence element.