WHITE ORGANIC ELECTROLUMINESCENT ELEMENT AND LIGHTING DEVICE

• US 20100127246A1
• Filed: 04/04/2008
• Published: 05/27/2010
• Est. Priority Date: 04/17/2007
• Status: Active Grant

• Current Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Original Assignee: Konica Minolta Holdings Incorporated (Konica Minolta Inc.)
• Inventors: Nakayama, Tomoyuki, Nakayama, Yoriko, Kojima, Shigeru, Hiyama, Kunimasa
• Granted Patent: US 9,006,711 B2
• Time in Patent Office: Days
• US Class Current: 257/40
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: C09K 2211/1029 containing one nitrogen atom as the heteroatom
• CPC Class Codes: C09K 2211/1044 containing two nitrogen atoms as heteroatoms
• CPC Class Codes: C09K 2211/1092 containing sulfur as the only heteroatom
• CPC Class Codes: C09K 2211/185 of the platinum group, i.e. Os, Ir, Pt, Ru, Rh or Pd
• 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 2101/10 Triplet emission
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 85/342 comprising iridium
• CPC Class Codes: H10K 85/344 comprising ruthenium
• CPC Class Codes: H10K 85/346 comprising platinum
• CPC Class Codes: H10K 85/348 comprising osmium
• CPC Class Codes: H10K 85/657 Polycyclic condensed heteroaromatic hydrocarbons
• CPC Class Codes: H10K 85/6572 comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

Disclosed is a white light-emitting organic electroluminescent device, which is excellent in stability of emission chromaticity over a long operation period, while having high electrical efficiency, long life, excellent storage stability and excellent color rendering properties. Also disclosed is an illuminating device using such an organic electroluminescent device. Specifically disclosed is an organic electroluminescent device having a light-emitting layer between an anode and a cathode, which is characterized by comprising a light-emitting layer A having a maximum emission wavelength of not more than 480 nm and containing a phosphorescent dopant having a maximum emission wavelength of not more than 480 nm, and a light-emitting layer B arranged between the light-emitting layer A and the anode, which has a maximum emission wavelength of not less than 510 nm and contains a phosphorescent dopant. This organic electroluminescent device is also characterized in that the concentration of the phosphorescent dopant contained in the light-emitting layer A varies in the thickness direction of the light-emitting layer A. Also specifically disclosed is an illuminating device using such a white light-emitting organic electroluminescent device.

Claims

1. A white organic electroluminescent element comprising light emitting layers between an anode and a cathode,

wherein the light emitting layers include:

a light emitting layer A which contains a phosphorescence emitting dopant exhibiting a maximum emission wavelength of 480 nm or less; and

a light emitting layer B which contains a phosphorescence emitting dopant exhibiting a maximum emission wavelength of 510 nm or more,

provided that the light emitting layer B is located between the light emitting layer A and the anode; and

a concentration of the phosphorescence emitting dopant in the light emitting layer A changes in a thickness direction of the light emitting layer A.

2. The white organic electroluminescent element described in claim 1,

wherein the phosphorescence emitting dopant contained in the light emitting layer A has at least one of partial structures represented by Formulas (A) to (C):

wherein Ra represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group;

Rb and Rc each represent a hydrogen atom or a substituent;

A1 represents a group of atoms necessary to form an aromatic ring or an aromatic heterocyclic ring; and

M represents Ir or Pt,

wherein Ra represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group;

Rb, Rc, Rb₁ and Rc₁ each represent a hydrogen atom or a substituent;

A1 represents a group of atoms necessary to form an aromatic ring or an aromatic heterocyclic ring; and

M represents Ir or Pt,

wherein Ra represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group;

Rb and Rc each represent a hydrogen atom or a substituent;

A1 represents a group of atoms necessary to form an aromatic ring or an aromatic heterocyclic ring; and

M represents Ir or Pt.

3. The white organic electroluminescent element described in claim 1,

wherein at least one of the phosphorescence emitting dopants contained in the light emitting layer A exhibits a maximum emission wavelength of 465 nm or less.

4. The white organic electroluminescent element described in claim 1,

wherein the light emitting layer B contains at least two phosphorescence emitting dopants each exhibiting an maximum emission wavelength differing in an amount of 30 nm or more with each other.

5. The white organic electroluminescent element described in claim 1,

wherein the light emitting layer A and the light emitting layer B each contain a host compound having the same structure with each other and having a glass transition temperature of 90°

C. or more.

6. The white organic electroluminescent element described in claim 1,

wherein the concentration of at least one of the phosphorescence emitting dopants contained in the light emitting layer A is decreased from a side of the anode to a side of the cathode in a thickness direction of the light emitting layer A.

7. A lighting device comprising the white organic electroluminescent element described in claim 1.