Stock material or miscellaneous articles – Composite – Of metal
Patent
1992-05-04
1994-11-22
Ryan, Patrick J.
Stock material or miscellaneous articles
Composite
Of metal
313504, 428917, 25230116, 25230135, 585 24, 585 25, 585 27, B32B 900
Patent
active
053668111
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to an organic electroluminescence device. More particularly, it relates to a styryl compound obtained by combining fluorescent compounds with a divalent group to break the conjugated system, an efficient process for production thereof, and an organic electroluminescence device using the styryl compound as a light emitting material.
2. Background Art
Recently, since an electroluminescence device (hereinafter referred to as EL device) has features in distinguishing itself easily because of its self-emission and having a high impact resistance because it is a completely solid device, the uses of said device as a luminescent device for various display apparatus have attracted attention.
Said EL devices include an inorganic EL device comprising an inorganic compound as a light emitting material, and an organic EL device comprising an organic compound as a light emitting material. Among them, an organic EL device permits greatly reduced voltage to be applied, and, therefore, investigations have actively been undertaken to put it to practical use.
The above organic EL device basically comprises anode/light emitting layer/cathode, and those which are provided with a hole-injecting and -transporting layer and an electron-injecting and -transporting layer in addition to the above, for example, the structure as anode/hole-injecting and -transporting layer/light emitting layer/cathode, anode/light emitting layer/electron-injecting and -transporting layer/cathode, and anode/hole-injecting and -transporting layer/light emitting layer/electron-injecting and -transporting layer/cathode have been known. Said hole-injecting and -transporting layer has a function of transporting holes injected from the anode to the light emitting layer, and the electron-injecting and -transporting layer has a function of transporting electrons injected from the cathode to the light emitting layer. It has been known that by sandwiching said hole-injecting and -transporting layer between the light emitting layer and the anode, more holes are injected into the light emitting layer at lower voltage, and further, when the hole-injecting layer transports no electrons, electrons injected into the light emitting layer from the cathode or the electron-injecting and -transporting layer are accumulated in the light emitting layer near the interface of the hole-injecting layer and the light emitting layer, thereby light-emitting efficiency increases (Appl. Phys. Lett., Vol. 51, p.913 (1987)).
As to the conventional organic EL device, a device cannot be prepared favorably or its light emitting efficiency is undesirably decreased because the thin film property of the light emitting material is poor. Even if the light emitting material itself has EL performance, it is not favorably processed to a device because it becomes turbid in the course of being formed into a device. That is because the EL device looks milky turbid since the crystal particle diameter of the light emitting layer is close to the wavelength of visible light. Since the film thickness of the light emitting layer is as small as several 10 mm, in the light emitting layer of which crystal particle diameter is large, pinholes probably will occur, resulting in an incomplete device. Moreover, when the device is formed and allowed to stand at room temperature in the air or in an inert atmosphere or in an atmosphere of an inert gas, it crystallizes gradually and deterioration of a device is easy to occur due to pinholes. Further, after a device is formed, when a electric current is passed through the device, crystallization of the light emitting layer, melting, enlargement of pinholes, peeling of the layer and so on proceed due to the generation of the Joule heat of the device, and the device is deteriorated.
For the above reasons, none of conventional organic EL devices shows a light emission with a high brightness and a high efficiency under present conditions.
For example, it is reported that an EL emission of approximately 80 cd/m.
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Higashi Hisahiro
Hosokawa Chishio
Tokailin Hiroshi
Idemitsu Kosan Co. Ltd.
Jewik Patrick
Ryan Patrick J.
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