# US 8,786,177 B2 · Single-photon type organic electroluminescent element

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- Number: US 8,786,177 B2
- Document ID: US8786177B2
- Status: Granted
- Kind: B2
- Application number: 13/498,430
- Filed: 2010-09-22
- Published: 2012-07-19
- Granted: 2014-07-22
- Earliest claimed: 2009-09-29
- Assignees: Sumitomo Chemical Company, Limited
- Applicants: Yoshinobu Ono
- Inventors: Yoshinobu Ono
- Web page: https://patentgrep.com/patent/US8786177B2

## CPC

- H10K 50/13: comprising stacked EL layers within one EL unit
- H10K 59/876: {comprising a resonant cavity structure, e.g. Bragg reflector pair}
- H10K 59/878: {comprising reflective means}
- H10K 50/11: characterised by the electroluminescent [EL] layers
- H10K 2101/40: Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
- H10K 2102/351: {Thickness}
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES

## Abstract

An object of the present invention is to provide an organic EL element including a plurality of light-emitting layers which each emit light having a different peak wavelength, and having excellent light-emitting performances such as light-emitting intensity with a simple structure. The present invention is a single-photon type organic electroluminescent element including a first electrode having optical transparency, a second electrode, and a plurality of light-emitting layers disposed between the first and second electrodes, wherein the plurality of light-emitting layers stacked between the first and second electrodes each emit light having a different peak wavelength, and each of the light-emitting layers is disposed separately from the second electrode at such a position that optical resonance is generated by reflected light emitted from a predetermined light-emitting layer toward the second electrode and reflected by the second electrode to return, and light emitted from the predetermined light-emitting layer toward the first electrode.

## Claims

### Claim 1

A single-photon type organic electroluminescent element comprising:
a first electrode having optical transparency;
a second electrode; and
a plurality of light-emitting layers disposed between the first and second electrodes, wherein
the plurality of light-emitting layers stacked between the first and second electrodes each emit light having a different peak wavelength, and
each of the light-emitting layers is disposed separately from the second electrode at such a position that optical resonance is generated by reflected light emitted from a predetermined light-emitting layer toward the second electrode and reflected by the second electrode to return, and light emitting from the predetermined light-emitting layer toward the first electrode,
wherein a distance between a light-emitting center portion of a k-th light-emitting layer, “k” representing a natural number, counted from a side of the first electrode among the plurality of light-emitting layers and a portion of the second electrode which reflects light falls within a range of 0.9 to 1.1 times a resonance distance dk represented by the following Equation (1):
d
k
=
m
k
.
⁢
λ
k
4
⁢
n
[
Numerical
⁢
⁢
Formula
⁢
⁢
1
]
wherein λk represents a peak wavelength of light emitted from the k-th light-emitting layer, n represents an average refractive index of a member placed between the k-th light-emitting layer and the second electrode, and mk is a positive odd number.

### Claim 2 (depends on 1)

The single-photon type organic electroluminescent element according to claim 1, wherein the plurality of light-emitting layers are formed by a coating method.

### Claim 3 (depends on 1)

A light-emitting device comprising the single-photon type organic electroluminescent element according to claim 1.

### Claim 4 (depends on 1)

A display device comprising the single-photon type organic electroluminescent element according to claim 1 and a color filter disposed at such a position that light emitted from the organic electroluminescent element passes.

### Claim 5 (depends on 1)

The single-photon type organic electroluminescent element according to claim 1, wherein any layer that is not a light-emitting layer is not provided between the light-emitting layers.

### Claim 6 (depends on 1)

The single-photon type organic electroluminescent element according to claim 1, wherein a light-emitting layer which emits light having a longer peak wavelength among the plurality of light-emitting layers is disposed at a position closer to the first electrode between the first and second electrodes.

### Claim 7 (depends on 6)

The single-photon type organic electroluminescent element according to claim 6, wherein the first electrode is an anode and the second electrode is a cathode.

### Claim 8 (depends on 1)

The single-photon type organic electroluminescent element according to claim 1, wherein the plurality of light-emitting layers comprise a light-emitting layer which emits red light, a light-emitting layer which emits green light, and a light-emitting layer which emits blue light.