Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1999-05-27
2002-10-22
Yamnitzky, Marie (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C313S504000, C313S506000
Reexamination Certificate
active
06468675
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to an organic electroluminescent device having an excellent luminescence property such as high luminance efficiency.
(b) Description of the Related Art
An organic electroluminescent device (which will hereinafter be called “organic EL device”) is a light-emitting device which makes use of the principle that when an electric field is applied, a fluorescent material emits light in response to the charge recombination of holes injected from an anode and electrons injected from a cathode. After C. W. Tang et al. of Eastman Kodak Company reported a low-voltage-driven organic EL device using a double layered structure (C. W. Tang, S. A. Vanslyke, Applied Physics Letters, Vol. 51, 913 (1987) and the like), studies on an organic EL device have been briskly carried out. Tang et al. reported an organic EL device using tris(8-hydroxyquinolinol aluminum) in a light-emitting layer and a triphenyldiamine derivative in a hole-transporting layer. This stacked structure gives such advantages as an improvement in the injection efficiency of holes into the light-emitting layer; blocking of electrons injected from a cathode, which increase the efficiency of exciton production from charge recombination; and confinement of the excitons into the light-emitting layer. A double layered structure composed of a hole-injecting and transporting layer and an electron-transporting and light-emitting layer or a triple layered structure composed of a hole-injecting and transporting layer, a light-emitting layer and an electron-injecting and transporting layer is well known as an organic EL device. In order to increase the recombination efficiency of injected holes and electrons, various improvements in the device structure or fabrication process have been introduced to such multi-layered devices.
As a hole transport material, aromatic diamine derivatives such as N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine are well known (for example, Patent Publications JP-A-8-20771, JP-A-8-40995, JP-A-8-40997, JP-A-8-53397, and JP-A-8-87122).
As an electron transporting material, oxadiazole derivatives, triazole derivatives and the like are well known.
Chelate complexes such as tris(8-quinolinolate)aluminum complex, coumarin derivatives, tetraphenylbutadiene derivatives, bisstyrylarylene derivatives, oxadiazole derivatives and the like are known as light emitting materials. Since various color light in a visible region from blue to red are obtained from these light-emitting materials, there is increased expectation for industrialization of a full color organic EL device (refer to, e.g., JP-A-8-23965, JP-A-7-138561, and JP-A-3-200889)
In recent days, organic EL devices with high brightness and long lifetime have been disclosed or reported. For example, JP-A-9-268284 describes diphenylamino arylene styryl derivatives used for a luminescent layer and aromatic tertiary amine used for a hole transport layer, but their efficiencies are not enough for most applications. We have found that the EL device having a combination of a specific one of diphenylamino arylene styryl derivatives as the luminescent material and aromatic tertiary amine as the hole transport material as described in the publication exhibited low luminescent property.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide materials for the organic EL devices having high luminance and long-term operating lifetime.
The inventors found that an organic EL device having a specific one of diphenylamino arylene styryl derivatives as a luminescent layer and a specific one of triamine compounds as a hole transport material in combination has much higher luminance and thus higher luminescent efficiency than the organic EL device having an aromatic diamine compound as a hole transport material. JP-A-8-193191, JP-A-9-95470, JP-A-9-208533, JP-A-5-239455 etc. describe the triphenyl amine derivatives used as hole transport materials; however, the described materials in these patent applications do not include diphenylamino arylene styryl derivatives, which we have found.
The inventors also found that, if a substituent group other than hydrogen exists in the beta position in a diarylamino naphthalene derivative having a diaryl amine group in the alpha position or exists in the alpha or gamma position in a diarylamino naphthalene derivative having a diaryl amine group in the beta position, the organic EL device having a luminescent layer including such a diarylamino naphthalene derivative exhibited an especially excellent blue emission. The present invention is based on these findings.
Thus, the present invention provides, in a first aspect thereof, an organic EL device having a luminescent layer and a hole transport layer and including one or more than one organic thin-film layers disposed between an anode and a cathode.
The luminescent layer includes, in the form of a mixture or a single substance, the compound expressed in a general formula [1] as follows:
wherein Ar
1
represents a substituted or non-substituted arylene group having 5-30 carbons, each of Ar
2
to Ar
5
independently represents a substituted or non-substituted aryl group having 6-20 carbons, and at least one of Ar
2
to Ar
5
has a styryl group expressed in a general formula [2] as follows:
wherein each of R
1
to R
11
independently represents hydrogen atom, halogen atom, hydroxyl group, substituted or non-substituted amino group, cyano group, nitro group, substituted or non-substituted alkyl group, substituted or non-substituted alkenyl group, substituted or non-substituted cycloalkyl group, substituted or non-substituted alkoxy group, substituted or non-substituted aromatic hydrocarbon group, substituted or non-substituted aromatic heterocyclic group, substituted or non-substituted aralkyl group, substituted or non-substituted aryloxy group, substituted or non-substituted alkoxycarbonyl group, or a carboxyl group. Ar
2
and Ar
3
and/or Ar
4
and Ar
5
may form a ring therebetween.
The hole transport layer includes, in the form of a mixture or a single substance, the compound expressed in a general formula [3] as follows
wherein each of Ar
6
to Ar
8
represents a substituted or non-substituted arylene group having 5-30 carbons, each of R
14
to R
16
independently represents hydrogen atom, halogen atom, hydroxyl group, substituted or non-substituted amino group, cyano group, nitro group, substituted or non-substituted alkyl group, substituted or non-substituted alkenyl group, substituted or non-substituted cycloalkyl group, substituted or non-substituted alkoxy group, substituted or non-substituted aromatic hydrocarbon group, substituted or non-substituted aromatic heterocyclic group, substituted or non-substituted aralkyl group, substituted or non-substituted aryloxy group, substituted or non-substituted alkoxycarbonyl group, or a carboxyl group.
In the present invention, Ar
1
in the general formula [1] may be preferably naphthylene group or anthrylene group.
In a second aspect of the present invention, an organic EL device has at least a hole transport layer between an anode and thode, wherein the hole transport layer includes, in the form of a mixture or a single substance, the compound expressed in the above general formula [3].
In the above formula [3], at least two of R14 to R16 in the general formula [3] may be a diarylamino group expressed by —NAr
9
Ar
10
wherein each of Ar
9
and Ar
10
independently represents a substituted or non-substituted aryl group.
In the above formula [3], each of R
14
to R
16
may preferably represent a substituted or non-substituted 4-(diphenylamino)styryl group.
In a third aspect of the present invention, an organic EL device includes at least a luminescence layer between an anode and a cathode, wherein the luminescent layer includes, in the form of a mixture or a single substance, the compound expressed in a gene
Ishikawa Hitoshi
Oda Atsushi
Toguchi Satoru
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