Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2001-09-05
2003-02-04
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S307000, C564S308000, C428S690000, C428S917000, C313S504000, C313S506000
Reexamination Certificate
active
06515182
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel arylamine compound and an organic electroluminescence device and, more particularly, to an organic electroluminescence device having a high luminance, excellent heat resistance, a long life and an excellent hole transporting property and emits light at a high efficiency and a novel arylamine compound providing the advantageous properties to the organic electroluminescence device.
BACKGROUND ART
Organic electroluminescence (referred to as EL, hereinafter) devices are used for a planar light emitting member such as a flat panel display of wall televisions and a back light of displays and the development of EL devices has been widely conducted.
Light emission from an organic substance under an electric field was observed in 1963 by Pope as light emission from a single crystal of anthracene (J. Chem. Phys., 38 (1963) 2042). In 1965, Helfinch and Schneider succeeded in observing relatively strong electroluminescence of the injection type using a solution electrode system having a good efficiency of injection (Phys. Rev. Lett., 14 (1965) 229). Since then, studies on forming organic light emitting substances from conjugated organic host substances and conjugated organic activating agents having condensed benzene rings have been reported. As the examples of the organic host substance, naphthalene, anthracene, phenanthrene, tetracene, pyrene, benzopyrene, chrysene, picene, carbazole, fluorene, biphenyl, terphenyl, triphenylene oxide, dihalobiphenyls, trans-stilbene and 1,4-diphenylbutadiene were shown. As the examples of the activating agent, anthracene, tetracene and pentacene were shown. However, these organic light emitting substances existed as a single layer having a thickness exceeding 1 &mgr;m and a high electric field was required for the light emission. Therefore, studies on a thin layer device using the vacuum vapor deposition process have been conducted (for example, Thin Solid Films, 94 (1982) 171). However, a device exhibiting a sufficiently high luminance for practical application could not be obtained although the use of the thin layer was effective for decreasing the driving voltage.
Tang et al. prepared an EL device having two very thin films (a hole transporting layer and a light emitting layer) which were laminated in accordance with the vacuum vapor deposition process and disposed between the anode and the cathode and succeeded in obtaining a high luminance under a low driving voltage (Appl. Phys. Lett., 51 (1987) 913 and U.S. Pat. No. 4,356,429). Thereafter, the development of organic compounds used for the hole transporting layer and the light emitting layer was conducted for more than a dozen years and the life and the efficiency of light emission sufficient for practical application could be achieved. As the result, the practical application of the organic EL device started in the area of displays of automobile stereos and portable telephones.
However, the luminance of light emission and the durability against degradation after the use for a long time are not sufficient for practical applications and further improvements are required. In particular, when an organic El device is applied to full color displays, it is required that the luminance be as high as 300 cd/m
2
or greater and a half-life be as long as several thousand hours or longer with respect to each of R, G and B colors. It is particularly difficult that these properties are achieved with respect to blue light. For the emission of blue light, the gap of the light emitting layer must be as great as 2.8 eV or greater. The energy barrier in the hole injection between the hole transporting layer and the light emitting layer is great and the intensity of the electric field applied to the interface is great. Therefore, stable hole injection cannot be achieved by using a conventional hole transporting layer and the improvement has been desired.
When application of an organic EL device to automobiles is considered, conventional organic EL devices have a problem in storage at a high temperature such as a temperature of 100° C. or higher. Conventional hole transporting layers have low glass transition temperatures and it was found that overcoming this problem by simply raising the glass transition temperature to a temperature exceeding 100° C. was not unsuccessful. Thus, the sufficient property for storage at high temperatures has not been achieved. Moreover, a problem arises in that exciplexes are formed by the interaction between the hole transporting layer and the light emitting layer and the luminance of the device deteriorates.
DISCLOSURE OF THE INVENTION
The present invention has been made to overcome the above problems and has an object of providing an organic EL device having a high luminance, excellent heat resistance, a long life and an excellent hole transporting property and emits light at a high efficiency and a novel arylamine compound providing the advantageous properties to the organic electroluminescence device.
As the result of extensive studies by the present inventors to develop an organic EL device having the above advantageous properties, it was found that, when a novel arylamine compound having a specific structure is added to the layer of organic compounds, the luminance, the heat resistance, the life and the hole transporting property of the organic EL device are improved and a high efficiency of light emission can be achieved. The present invention has been completed based on the knowledge.
The present invention provides:
A novel arylamine compound represented by the following general formula (1):
wherein R
1
and R
2
each independently represent a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted alkoxyl group having 1 to 30 carbon atoms, a substituted or unsubstituted aryl group having 6 to 40 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 40 carbon atoms or a substituted or unsubstituted aryloxyl group having 6 to 40 carbon atom; and
Ar
1
to Ar
4
each independently represent a substituted or unsubstituted aryl group having 6 to 40 carbon atoms or a substituted or unsubstituted heterocyclic group having 5 to 40 carbon atoms and may represent a same group or different groups, with provisos that at least two of Ar
1
to Ar
4
each represent a substituted or unsubstituted m-biphenyl group or biphenyl group substituted with aryl groups and others of Ar
1
to Ar
4
each represent a substituted or unsubstituted biphenyl group and that, when at least two of Ar
1
to Ar
4
each represent biphenyl group substituted with two aryl groups, others of Ar
1
to Ar
4
each represent a substituted or unsubstituted aryl group; and
A novel arylamine compound represented by the following general formula (2):
wherein at least one of A and B represents an atom group forming a substituted or unsubstituted saturated five-membered to eight-membered ring which may comprise a spiro bond, with provisos that, when any one of A and B represents an atom group forming a saturated five-membered ring, A and B each represent a group forming a ring structure or any of A and B represents a group comprising a spiro bond and that at least one of A and B represents a group which does not comprise two or more unsaturated six-membered rings; and
Ar
5
to Ar
8
each independently represent a substituted or unsubstituted aryl group having 6 to 40 carbon atoms or a substituted or unsubstituted heterocyclic group having 5 to 40 carbon atoms and may represent a same group or different groups.
The present invention further provides an electroluminescence device comprising a pair of electrodes and a layer of organic compounds disposed between the pair of electrodes, wherein the layer of organic compounds comprises the novel arylamine compound described above.
THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION
The novel arylamine compound of the present invention is represented by general formula (1) or general formula (2) shown above.
In general formula (1), R
1
and R
2
each independen
Funahashi Masakazu
Hosokawa Chishio
Barts Samuel
Idemitsu Kosan Co. Ltd.
Parkhurst & Wendel L.L.P.
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