Stock material or miscellaneous articles – Composite – Of inorganic material
Patent
1997-01-17
1999-07-06
Nold, Charles
Stock material or miscellaneous articles
Composite
Of inorganic material
428691, 428917, 313504, H05B 3300
Patent
active
059195797
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an emission device by utilizing electroluminescence of an emitting element which emits light by injection of an electric current wherein the emission device is provided with an emission layer wherein the emitting elements are formed into layers. More specifically, it relates to an organic electroluminescent device (hereinafter referred to as "organic EL device") in which the emission layer is composed of an organic compound as an emitting element.
Hithertofore, organic EL devices having various structures have been proposed. For example, a two-layer type structure wherein a thin film of a fluorescent material 2 as an emission layer and a hole transport layer 3, each comprising an organic compound and being layered on each other, are arranged between a metal cathode 1 and a transparent anode 4, as shown in FIG. 1; and a three-layer type structure wherein an electron transport layer 6 comprising an organic compound, an emission layer 2 and a hole transport layer 3 are layered between a metal cathode 1 and a transparent anode 4 are known. In the above devices, the hole transport layer 3 has the function of easily injecting positive holes from the anode and the function of blocking electrons; and the electron transport layer 6 has the function of easily injecting the electrons from the cathode and the function of blocking holes.
In these organic electroluminescent devices, ITO is mainly used for the transparent electrode 4, and a film thereof is formed on a glass substrate 5. By recombination of on electron injected from the metal cathode 1 and a hole injected into the emission layer from the anode 4, light radiated in the process of radiative decay of the produced exciton is emitted through a transparent anode and a transparent glass substrate.
Detailed explanation of organic electroluminescent devices are described, for example, in the following literature references: Display Device Research Association, Science Forum (published 1992) SPIE Proceedings Vol. 1910 (1993), E. M. Conwell and M. R. Miller
However, in the conventional organic EL devices, the stability of light-emission is not necessarily considered sufficiently satisfactory, and organic EL devices which emit light more stably are desired. Under such circumstances, the present inventors extensively studied the development of organic EL devices having excellent characteristics, and, as a result, found that an organic EL device having an improved stability can be obtained by using a specific naphthalimide derivative, and, based on this finding, completed the present invention. An object of the present invention is to provide an organic EL device which stably emits at high luminance.
The organic EL device according to the present invention is characterized in that, in the organic EL device comprising an organic compound, the emission layer comprises a naphthalimide derivative represented by the formula (1): ##STR2## wherein R.sup.1 represents a hydrogen atom, a straight chain or branched chain alkyl group having from 1 to 16 carbon atoms, an aryl group, preferably having from 4 to 10 carbon atoms, which may have one or more substituents or an aralkyl group, preferably having from 5 to 22 carbon atoms, which may have one or more substituents;
R.sup.2, R.sup.3, R.sup.4 independently of each other, represent an alkyl, alkoxy or ester group, each having from 1 to 16 carbon atoms, an aryl- or aryloxy group, having from 4 to 10 carbon atoms, which may have one or more substituents, --CN, --CF.sub.3, F or NR.sup.5 R.sup.6, wherein R.sup.5, R.sup.6 independently of each other represent an alkyl group, having from 1 to 16 carbon atoms, or an aryl group, having from 4 to 10 carbon atoms, which may have one or more substituents;
m, n, p are 0, 1, 2 or 3, preferably 0, 1 or 2, most preferably 0.
Preferably, R.sup.2 and R.sup.3 have the same meaning.
In the above-described formula (1), when R.sup.1 represents a straight chain or branched alkyl group having from 1 to 16 carbon atoms, an alkyl group having from 1 to 6 carbon atoms, for examp
REFERENCES:
Database WPI, Sec. Ch, Wk. 9252, Derwent Pub. Ltd., Class E13, AN 92-426615 & JP A 04 320 486 (Mitsubishi Kasei Corp), Nov. 11, 1992.
Database WPI, Sec. Ch, Wk. 9204, Derwent Pub. Ltd., Class E19, AN 92-028265 & JP A 03 274 695 (NEC CORP), Dec. 5, 1991.
Kang Wen-Bing
Potrawa Thomas
Tokida Akihiko
Winterfeldt Andreas
Yu Nu
Hoechst Aktiengesellschaft
Nold Charles
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