Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2001-11-27
2004-10-12
Yamnitzky, Marie (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C313S504000, C313S506000, C257S040000, C257S102000, C257S103000
Reexamination Certificate
active
06803121
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an organic electroluminescence device (hereinafter, “electroluminescence” will be referred to as EL) and, more particularly, to an organic EL device exhibiting suppressed crystallization in driving for a long time or in environments at high temperatures, having improved durability and advantageously used in practical applications.
BACKGROUND ART
EL devices which utilize light emission under application of an electric field show high self-distinguishability due to the self-emission and exhibit excellent impact resistance because they are completely solid devices. Therefore, EL devices have been attracting attention for application as light emitting devices in various types of display apparatus.
The EL devices include inorganic EL devices in which an inorganic compound is used as the light emitting material and organic EL devices in which an organic compound is used as the light emitting material. Organic EL devices have been extensively studied for practical application as a light emitting device of the next generation because the applied voltage can be decreased to a great 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 EL 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 constructions 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, stability in driving for a long time and driving stability and storage stability in environments at high temperatures such as outdoors and in automobiles are required. A great problem under such circumstances is in that materials constituting a device crystallize under the above environment and uniformity of light emission of the device is adversely affected. When a device is driven for a long time, the materials constituting the device is subjected to a great thermal change due to the elevation of the temperature caused by the heat generated by the device itself and the change in the environment at the outside. It is known that organic compounds are crystallized due to the thermal change. The crystallization causes short circuits and formation of defects and gives rise not only to deterioration in the uniformity of the light emitting surface but also to failure in the light emission, occasionally. Therefore, studies on technology to suppress the crystallization have been made.
As the method for suppressing crystallization, for example, improvement in heat resistance of materials constituting a device, specifically, by elevation of the glass transition temperature has been attempted (Japanese Patent Application Laid-Open No. Heisei 10(1998)-110163). However, the above method has drawbacks in that synthesis of the material becomes very difficult and cost of the material increases and that, when the improvement in heat resistance is emphasized, the material has difficulty in purification since the material is not easily soluble in solvents due to an increased molecular weight of the compound and the performance of the EL device deteriorates.
A device having an improved storage property at high temperatures by adding a substance for suppressing crystallization to the light emitting material is disclosed in Japanese Patent Application Laid-Open No. 2000-208264. The durability of this device in driving at a temperature higher than 85° C. has to be improved although crystallization can be suppressed when the device is kept at 85° C. or lower.
DISCLOSURE OF THE INVENTION
Under the above circumstances, the present has an object of providing an organic EL device exhibiting suppressed crystallization in driving for a long time or in environments at high temperatures, has improved durability and is advantageously used in practical applications.
As the result of extensive studies by the present inventors to achieve the above object, it was found that crystallization was suppressed in driving the device for a long time or in environments at higher temperatures and a device having improved durability could be obtained when, in an organic electroluminescence device which comprises a pair of electrodes comprising an anode and a cathode and a layer of organic compounds comprising at least an organic light emitting layer and disposed between the pair of electrodes, the layer of organic compounds comprised a light emitting material and a bis-condensed aromatic cyclic compound. The present invention has been completed based on the above knowledge.
The present invention provides an organic electroluminescence device which comprises a pair of electrodes comprising an anode and a cathode and a layer of organic compounds comprising at least an organic light emitting layer and disposed between the pair of electrodes, wherein the layer of organic compounds comprises a light emitting material and a bis-condensed aromatic cyclic compound.
THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION
The organic electroluminescence device of the present invention comprises a pair of electrodes comprising an anode and a cathode and a layer of organic compounds comprising at least an organic light emitting layer and disposed between the pair of electrodes, wherein the layer of organic compounds comprises a light emitting material and a bis-condensed aromatic cyclic compound.
It is preferable that the light emitting material is a compound represented by following general formula (1):
wherein X and Y each independently represent a substituted or unsubstituted aryl group having 6 to 50 carbon atoms or a substituted or unsubstituted monovalent heterocyclic group having 3 to 50 carbon atoms and may represent the same group or different groups and Ar represents an arylene group having 6 to 80 carbon atoms, a polyarylene group, a divalent triphenylamine residue group, a divalent heterocyclic group having 3 to 80 carbon atoms or a divalent group formed by bonding these groups to each other.
Examples of the substituent in the groups represented by X and Y in above general formula (1) include halogen atoms, cyano group, nitro group, alkyl groups, alkoxyl groups, aryloxyl groups, alkylthio group, arylthio groups, arylalkyl groups, monocyclic groups, condensed polycyclic groups, arylsilyl groups, heterocyclic groups and alkenyl groups.
The compound represented by general formula (1) may be used singly or in combination of two or more.
The bis-condensed aromatic cyclic compound described above is a material which suppresses crystallization in the light emitting layer without adverse effects on the light emitting property of the device and improves the properties in driving at high temperatures and the storage property by mixing the material into the light emitting layer. The bis-condensed aromatic cyclic compound is suitable as the material for this purpose.
The above bis-condensed aromatic cyclic compound is a compound formed by linking at least two condensed aromatic rings to each other through a linking group or a single bond. As the condensed aromatic ring, cyclic structures of naphthalene, anthracene, fluorene, perylene, pyrene, phenanthrene, chrysene, tetracene, rubrene, pentacene, triphenylene, rubicene, pycene, coronene and fluoranthene are preferable and cyclic structures of anthracene, fluorene, perylene, pyrene, phenanthrene and fluoranthene are more preferable. As the linking group, hydrocarbon groups and heterocyclic groups are preferable. As the hydrocarbon group, arylene groups are preferable. In particular, bisanthracene compound is preferable as the bis-condensed aromatic cyclic compound used in the present inv
Fukuoka Kenichi
Hosokawa Chishio
Sakai Toshio
Tokairin Hiroshi
Idemitsu Kosan Co. Ltd.
Parkhurst & Wendel L.L.P.
Yamnitzky Marie
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