Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-09-20
2003-03-18
Yamnitzky, Marie (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C313S504000, C313S506000, C252S301160
Reexamination Certificate
active
06534199
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an organic electroluminescence device (“electroluminescence” will be referred to as EL, hereinafter) and an organic light emitting medium, and more particularly to an organic EL device which exhibits excellent heat resistance, a long life and a high efficiency and emits bluish light and an organic light emitting medium advantageously used for the organic electroluminescence device.
BACKGROUND ART
Electroluminescence devices which utilize electroluminescence show high self-distinguishability because of the self-emission and are excellent in impact resistance because they are completely solid devices. Therefore, electroluminescence devices have been attracting attention for application as light emitting devices in various types of display apparatus.
The electroluminescence devices include inorganic electroluminescence devices in which an inorganic compound is used as the light emitting material and organic electroluminescence devices in which an organic compound is used as the light emitting material. Organic electroluminescence devices have been extensively studied for practical application as a display device of the next generation because the applied voltage can be decreased to a large extent, the size of the device can be reduced easily, consumption of electric power is small, planar light emission is possible and three primary colors are easily emitted.
As for the construction of the organic electroluminescence device, the basic construction comprises an anode/an organic light emitting layer/a cathode. Constructions having a hole injecting and transporting layer or an electron injecting layer suitably added to the basic construction are known. Examples of such construction include the construction of an anode/a hole injecting and transporting layer/an organic light emitting layer/a cathode and the construction of an anode/a hole injecting and transporting layer/an organic light emitting layer/an electron injecting layer/a cathode.
In practical application of organic EL devices, driving stability and storage stability in environments at high temperatures such as outdoors and in automobiles are required. When an EL device is used outdoors or for an instrument used in an automobile, in general, storage stability at a high temperature of 75° C. is required. However, when a conventional organic EL device is stored at a high temperature of about 75° C., problems arise in that color of emitted light changes and the efficiency of light emission decreases. These problems inevitably restrict application of the organic EL devices.
Various attempts have been made to obtain a device which exhibits excellent heat resistance, a long life and a high efficiency and emits bluish light. However, it is the actual present situation that no devices having satisfactory properties are obtained.
For example, a technology in which a single monoanthracene compound is used as the organic light emitting material has been disclosed in Japanese Patent Application Laid-Open No. Heisei 11(1999)-3782. However, in accordance with this technology, for example, the luminance obtained under a current density of 165 mA/cm
2
is as small as 1650 cd/m
2
and the efficiency is as small as 1 cd/A. Therefore, the technology is not practically useful. Another technology in which a single bisanthracene compound is used as the organic light emitting material has been disclosed in Japanese Patent Application Laid-Open No. Heisei 8(1996)-12600. However, in accordance with this technology, the efficiency is as small as 1 to 3 cd/A and further improvement is desired for practical use. An organic EL device having a long life in which a distyryl compound is used as the organic light emitting material and styrylamine is additionally used has been disclosed in International Patent Application Laid-Open No. 94-6157. However, this device has a half-life of about 1000 hours and further improvement is desired.
DISCLOSURE OF THE INVENTION
Under the above circumstances, the present invention has an object of providing an organic EL device which exhibits excellent heat resistance, a long life and a high efficiency and emits bluish light and an organic light emitting medium advantageously used for the organic EL device.
As the result of extensive studies by the present inventors to achieve the above object, it was found that, when an organic light emitting medium comprises a combination of a mono-, di-, tri- or tetrastyryl derivative containing amine and a specific anthracene derivative, an organic EL device in which a layer comprising this light emitting medium is disposed between a pair of electrodes exhibits excellent heat resistance, a long life and a high efficiency and emits bluish light. The present invention has been completed based on this knowledge.
The present invention provides an organic EL device comprising a pair of electrodes and a layer of an organic light emitting medium which is disposed between the pair of electrodes and comprises (A) at least one compound selected from the group consisting of monostyryl derivatives containing amine, distyryl derivatives containing amine, tristyryl derivatives containing amine and tetrastyryl derivatives containing amine and (B) at least one compound selected from the group consisting of anthracene derivatives represented by general formula (I):
A
1
—L—A
2
(I)
wherein A
1
and A
2
each represent a substituted or unsubstituted monophenylanthryl group or a substituted or unsubstituted diphenylanthryl group and may be the same with or different from each other and L represents a single bond or a divalent linking group; and anthracene derivatives represented by general formula (II):
A
3
—An—A
4
(II)
wherein An represents a substituted or unsubstituted divalent anthracene residue group, A
3
and A
4
each represent a substituted or unsubstituted monovalent condensed aromatic ring group or a substituted or unsubstituted non-condensed ring aryl group having 12 or more carbon atoms and may be the same with or different from each other.
The present invention also provides an organic light emitting medium which comprises (A) at least one compound selected from the group consisting of monostyryl derivatives containing amine, distyryl derivatives containing amine, tristyryl derivatives containing amine and tetrastyryl derivatives containing amine and (B) at least one compound selected from the group consisting of anthracene derivatives represented by general formula (I) shown above and anthracene derivatives represented by general formula (II) shown above.
THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION
The organic EL device of the present invention has a structure comprising a pair of electrode and a layer of an organic light emitting medium disposed between the pair of electrode.
In the present invention, a combination of (A) a styryl derivative containing amine and (B) an anthracene derivative having a specific structure is used for the above layer of an organic light emitting medium.
The styryl derivative containing amine of component (A) is at least one compound selected from the group consisting of monostyryl derivatives containing amine, distyryl derivatives containing amine, tristyryl derivatives containing amine and tetrastyryl derivatives containing amine.
In the present invention, a compound having one styryl or styrylene group in the molecule is referred to as a monostyryl derivative, a compound having two styryl or styrylene groups in the molecule is referred to as a distyryl derivative, a compound having three styryl or styrylene groups in the molecule is referred to as a tristyryl derivative and a compound having four styryl or styrylene groups in the molecule is referred to as a tetrastyryl derivative. These compounds in general are referred to as styryl derivatives. The styryl group and the styrylene group mean a monovalent group and a divalent group, respectively, in which substituted or unsubstituted vinyl group is directly bonded to an aromatic ring group. The derivative containing amine mean
Fukuoka Kenichi
Higashi Hisahiro
Hosokawa Chishio
Ikeda Hidetsugu
Idemitsu Kosan Co. Ltd.
Yamnitzky Marie
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