LIGHT-EMITTING ELEMENT AND DISPLAY DEVICE USING SAME

• US 20120126272A1
• Filed: 01/30/2012
• Published: 05/24/2012
• Est. Priority Date: 09/29/2009
• Status: Active Grant

• Current Assignee: JDI Design and Development GK
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: KURATA, Keiko, NISHIYAMA, Seiji, ISOBE, Takashi
• Granted Patent: US 8,779,453 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H05B 33/14 characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: H10K 2102/351 Thickness
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 59/38 comprising colour filters or colour changing media [CCM]

Abstract

A light-emitting element that has an improved light-extraction efficiency and an improved color purity of an emitted light. A light-emitting element includes a reflective electrode, a transparent electrode, a light-emitting layer, a functional layer, and a color filter. An optical film thickness of the functional layer is from approximately 218 nm to approximately 238 nm for a light emitting element that emits a blue light. An optical film thickness of the functional layer is from approximately 384 nm to approximately 400 nm for a light emitting element that emits a red light.

Claims

1. A light-emitting element, comprising:

a reflective electrode that reflects incident light;

a transparent electrode that faces the reflective electrode and transmits an incident light therethrough;

a light-emitting layer, disposed between the reflective electrode and the transparent electrode, that emits a blue light;

a functional layer disposed between the reflective electrode and the light-emitting layer; and

a color filter disposed above the light-emitting layer, with the transparent electrode being interposed therebetween, wherein

a first portion of the blue light emitted from the light-emitting layer travels along a first optical path that passes through the functional layer, strikes the reflecting electrode and is reflected by the reflective electrode, and is then emitted externally after passing through the functional layer, the light-emitting layer, the transparent electrode, and the color filter,

a second portion of the blue light emitted from the light-emitting layer travels along a second optical path towards the transparent electrode, instead of towards the reflective electrode, and is emitted externally after passing through the transparent electrode and the color filter, and

an optical film thickness of the functional layer is from approximately 218 nm to approximately 238 nm.

3. The light-emitting element of claim 1, wherein

a spectral intensity of light passing through the color filter is at a maximum value in a first wavelength range in which a spectral intensity of the blue light passing through the transparent electrode is at a maximum value, and in a second wavelength range that is longer than the first wavelength range and a third wavelength range that is shorter than the first wavelength range, the spectral intensity of light passing through the color filter being less than the maximum value in the first wavelength range, and

with respect to the blue light passing through the transparent electrode, the color filter reduces a passage of light components that are in the second wavelength range, are unnecessary for achieving a target chromaticity, and have a spectral intensity less than the maximum value, the color filter allowing passage of the light components in the first wavelength range and in the third wavelength range.

6. A display device comprising an array of blue, green, and red light-emitting elements on a substrate, wherein

each of the blue light-emitting elements is the light-emitting element of claim 1.

7. The display device of claim 6, wherein

each red light emitting element of the red light-emitting elements has an optical film thickness of a functional layer of the red light emitting element that is from approximately 384 nm to approximately 400 nm.

10. The light emitting element of claim 1, wherein the functional layer comprises plural layers.

2. A light-emitting element, comprising:

a reflective electrode that reflects incident light;

a transparent electrode that faces the reflective electrode and transmits an incident light therethrough;

a light-emitting layer, disposed between the reflective electrode and the transparent electrode, that emits a blue light;

a functional layer disposed between the reflective electrode and the light-emitting layer; and

a color filter disposed above the light-emitting layer, with the transparent electrode being interposed therebetween, wherein

a first portion of the blue light emitted from the light-emitting layer travels along a first optical path that passes through the functional layer, strikes the reflective electrode and is reflected by the reflective electrode, and is then emitted externally after passing through the functional layer, the light-emitting layer, the transparent electrode, and the color filter,

a second portion of the blue light emitted from the light-emitting layer travels along a second optical path towards the transparent electrode, instead of towards the reflective electrode, and is emitted externally after passing through the transparent electrode and the color filter, and

an optical film thickness L (in nm) of the functional layer satisfies a following equation;

8. A display device comprising an array of blue, green, and red light-emitting elements on a substrate, wherein

each of the blue light-emitting elements is the light-emitting element of claim 2.

9. The display device of claim 8, wherein

each red light emitting element of the red light-emitting elements has an optical film thickness of a functional layer of the red light emitting element that is from approximately 384 nm to approximately 400 nm.

11. The light emitting element of claim 2, wherein the functional layer comprises plural layers.

4. A light-emitting element, comprising:

a reflective electrode that reflects incident light;

a transparent electrode that faces the reflective electrode and transmits an incident light therethrough;

a light-emitting layer, disposed between the reflective electrode and the transparent electrode, that emits a red light;

a functional layer disposed between the reflective electrode and the light-emitting layer; and

a color filter disposed above the light-emitting layer, with the transparent electrode being interposed therebetween, wherein

a first portion of the red light emitted from the light-emitting layer travels along a first optical path that passes through the functional layer, strikes the reflective electrode and is reflected by the reflective electrode, and is then emitted externally after passing through the functional layer, the light-emitting layer, the transparent electrode, and the color filter,

a second portion of the red light emitted from the light-emitting layer travels along a second optical path towards the transparent electrode, instead of towards the reflective electrode, and is emitted externally after passing through the transparent electrode and the color filter, and

an optical film thickness of the functional layer is from approximately 384 nm to approximately 400 nm.

12. The light emitting element of claim 4, wherein the functional layer comprises plural layers.

5. A light-emitting element, comprising:

a reflective electrode that reflects incident light;

a transparent electrode that faces the reflective electrode and transmits an incident light therethrough;

a light-emitting layer, disposed between the reflective electrode and the transparent electrode, that emits a red light;

a functional layer disposed between the reflective electrode and the light-emitting; and

a color filter disposed above the light-emitting layer, with the transparent electrode being interposed therebetween, wherein

a first portion of the red light emitted from the light-emitting layer travels along a first optical path that passes through the functional layer, strikes the reflective electrode and is reflected by the reflective electrode, and is then emitted externally after passing through the functional layer, the light-emitting layer, the transparent electrode, and the color filter,

a second portion of the red light emitted from the light-emitting layer travels along a second optical path towards the transparent electrode, instead of towards the reflective electrode, and is emitted externally after passing through the transparent electrode and the color filter, and

an optical film thickness L (in nm) of the functional layer satisfies a following equation;

13. The light emitting element of claim 5, wherein the functional layer comprises plural layers.