Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-06-26
2002-11-26
Yamnitzky, Marie (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C313S504000, C313S506000
Reexamination Certificate
active
06485847
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an amine derivative used in an organic electroluminescent device and similar devices.
BACKGROUND ART
In recent years, an organic electroluminescent device (hereinafter abbreviated as “organic EL device”) has become of interest as a candidate for a flat display of high luminance which has never been attained. In accordance with this trend, organic EL devices have been the subject of active research and development efforts. An organic EL device has a structure in which a light-emitting layer is sandwiched by two electrodes. Holes injected from a positive electrode and electrons injected from a negative electrode are recombined within the light-emitting layer, to thereby emit light. Organic materials used for producing an organic EL device include high- and low-molecular-weight materials, and both types of materials are known to provide an organic EL device which can emit light of high luminance.
Organic EL devices are categorized into two types. A first type contains a charge-transporting layer which transports electrons and/or holes and to which a fluorescent dye is added, as has been described by C. W. Tang et al. (Journal of the Applied Physics, 65, 3,610 (1989)). The other type employs a fluorescent dye singly in a light-emitting layer (for example, a device described in Japanese Journal of Applied Physics, 27, L269 (1988)).
Organic EL devices employing a fluorescent dye singly in a light-emitting layer are further classified into the following three types. A first type is directed to a three-layered device in which a light-emitting layer is sandwiched by a hole-transportation layer which transports only holes, which are a form of charge, and an electron-transportation layer, which transports only electrons. A second type is directed to a two-layered device in which a hole-transportation layer and a light-emitting layer are stacked. A third type is directed to a two-layered device in which an electron-transportation layer and a light-emitting layer are stacked. An organic EL device is known to have improved light-emitting efficacy when it has a two- or three-layered structure.
However, conventional, organic EL devices do not necessarily exhibit satisfactory performance in practical application. One major reason for this may be attributed to lack of durability of the material used in the devices, particularly hole-transportation material.
In addition, hole-transportation material used for conventional devices tends to combine with light-emitting material and electron-transportation material, which materials are also used for the devices, to thereby form an exciplex which yields poor device efficacy. Therefore, the types of light-emitting materials or electron-transportation materials which can be used have been limited.
A variety of materials centering on triphenylamine derivatives have been known as hole-transportation materials used for such organic EL devices, but few materials are suitable for practical use; i.e., few are materials which impose no limit on the types of other materials simultaneously used for the devices and which provide high light-emitting efficacy and long service life.
For example, there has been reported N,N′-diphenyl-N′,N′-di(3-methylphenyl)-4,4′-diaminobiphenyl (hereafter abbreviated as TPD) (Applied Physics Letter, Vol. 57, No. 6, p. 531, 1990). This compound is thermally unstable, and is disadvantageous in terms of the service life of the resultant device. Many other triphenylamine derivatives are disclosed in U.S. Pat. Nos. 5,047,687, 4,047,948, and 4,536,457 and in Japanese Patent Application Laid-Open (kokai) Nos. 5-239455 and 8-87122. However, none of these are satisfactory in terms of well-balanced characteristics in practical application.
In addition, star-burst amine derivatives disclosed in Japanese Patent Application Laid-Open (kokai) Nos. 4-308688 and 6-1972 and “Advanced Materials” Vol. 6, p. 677 (1994); and compounds disclosed in Japanese Patent Application Laid-Open (kokai) Nos. 7-126226, 7-126615, 7-331238, 7-97355, 8-48656, and 8-100172 and, “Journal of the Chemical Society Chemical Communication” p. 2175 (1996) are unsatisfactory in terms of characteristics in practical application; i.e., they impose limitation of the types of other materials which is used simultaneously and fail to attain high light-emitting efficacy and long service life.
Incidentally, Japanese Patent Application Laid-Open (kokai) No. 7-301927 discloses that a naphthylamine derivative is applied to electrophotography, but does not disclose application of the derivative to an organic EL device.
As described above, hole-transportation materials used in conventional organic EL devices do not exhibit satisfactory performance in practical application, and thus there is need for an excellent material that can enhance the light-emitting efficacy and service life of organic EL devices.
In order to solve the above-described problems, an object of the present invention is to provide an organic EL device which has high light-emitting efficacy and long service life, and a novel hole-transportation material and light-emitting material which are used in the EL device and which are not limited by other materials used simultaneously.
DISCLOSURE OF THE INVENTION
In view of the foregoing, the present inventors have conducted extensive studies in an attempt to solve the aforementioned problems involved in conventional organic EL devices, and have found that when a specific type of amine derivative is used, a resultant organic EL device has high light-emitting efficacy and long service life. The present invention has been accomplished on the basis of this finding.
Accordingly, in a first aspect of the present invention, there is provided a specific amine compound represented by the following formula (1):
[wherein each of R
1
to R
20
represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group, and any of the substituted or unsubstituted aryl group or any of the substituted or unsubstituted heterocyclic group may form a condensed structure].
In a second aspect of the present invention, there is provided an organic electroluminescent device comprising an amine derivative represented by formula (1).
In a third aspect of the present invention, there is provided an organic electroluminescent device comprising a hole-transportation layer which contains an amine derivative represented by formula (1).
In a fourth aspect of the present invention, there is provided an organic electroluminescent device comprising a light-emitting layer which contains an amine derivative represented by formula (1).
In a fifth aspect of the present invention, there is provided an organic electroluminescent device comprising a hole-injection layer which contains an amine derivative represented by formula (1).
In a sixth aspect of the present invention, there is provided a hole-transportation material comprising an amine derivative represented by formula (1).
In a seventh aspect of the present invention, there is provided a light-emitting material comprising an amine derivative represented by formula (1).
BEST MODES FOR CARRYING OUT THE INVENTION
The present invention will next be described in detail.
As described above, the organic EL device of the present invention comprises an amine derivative represented by formula (1), and the amine derivative mainly functions as a hole-transportation material, a light-emitting material, and/or a hole-injection material. The amine derivative per se may form one or more of a hole-transportation layer, a light-emitting layer, and a hole-injection layer, or may be contained in one or more of these layers.
The organic EL device of the present invention may be realized in a variety of modes. The device has a basic structure in which a layer containing an amine derivative represented by formula (1) is sandwiched by a pair of electrod
Furukawa Kenji
Izumizawa Takenori
Uchida Manabu
Chisso Corporation
Yamnitzky Marie
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