Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1998-03-17
2001-08-28
Yamnitzky, Marie (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S704000, C428S917000, C313S504000, C313S506000, C252S301160, C564S305000, C564S315000, C564S431000, C564S433000
Reexamination Certificate
active
06280859
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a light-emitting material for an organo-electroluminescence (“EL” hereinafter) device for use as a flat light source or display, and to a light-emitting device having a high brightness.
PRIOR ART
An EL device using an organic substance is expected to have a great promise as a solid light-emitting inexpensive large-screen, full-color display device, and developments thereof are being made in many ways. Generally, an EL device is composed of a light-emitting layer and a pair of facing electrodes sandwiching the light-emitting layer. The light emission of an EL device is the following phenomenon. When an electric field is applied between the two electrodes, the cathode injects electrons into the light-emitting layer, and the anode injects holes into the light-emitting layer. When the electrons recombine with the holes in the light-emitting layer, their energy level shifts back to a valence bond band to release energy as light.
As compared with inorganic EL devices, conventional organic EL devices require high voltage, and their light emission brightness and light emission efficiency are low. Further, conventional organic EL devices deteriorate in properties to a great extent, and no organic EL device has been put to practical use.
There has been recently proposed an organic EL device which is produced by laminating a thin film containing an organic compound having a fluorescent quantum effect of emitting light at a low voltage as low as less than 10 V, and it attracts attention (Appl. Phy. Lett., Vol. 51, page 913, 1987). The above organic EL device has a light-emitting layer containing a metal chelate complex and a hole-injecting layer containing an amine-based compound, and emits green light having a high brightness. The above organic EL device achieves nearly practically usable performance, since it accomplishes a brightness of 1,000 cd/m
2
and a maximum light emission efficiency of 1.5 lm/W at a direct current voltage of 6 or 7V.
However, conventional organic EL devices including the above organic EL device are not yet satisfactory in brightness although these organic EL devices are improved in brightness to some extent. Further, they have a serious problem that their stability is insufficient in their continuous operation for a long period of time. That is because, for example, a metal chelate complex such as a tris(8-hydroxyquinolinate)-aluminum complex, or the like, is chemically unstable when an electric field is applied for light emission, is poor in adhesion to a cathode and extremely deteriorates in a short period of emission. For the above reasons, it is desired to develop a light-emitting material having an excellent light emission capacity and durability for developing an organic EL device which has a high light emission brightness and a high light emission efficiency and can perform a light emission in its continuous operation.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an organic EL device having a high light emission brightness and having excellent stability in the continuous operation.
The present inventors have made diligent studies for achieving the above object, and have found that an organic EL device having a light-emitting layer for which the material of any one of the formulae [1], [4] and [5] is adapted has a high light emission brightness and a high light emission efficiency and has excellent stability in the continuous operation. On the basis of the above finding, the present invention has been completed.
According to the present invention, there is provided a light-emitting material of the formula [1] for an organic EL device,
wherein A is a substituted or non-substituted aromatic group, a substituted or non-substituted fused aromatic group (excluding a group of the formula [2] shown below), a substituted or non-substituted hetero-aromatic group, a substituted or non-substituted fused hetero-aromatic group or a divalent group (excluding a group of the formula [3] shown below) in which 2 to 10 identical or different groups out of the above groups are bonded to each other directly or through at least one of an oxygen atom, a nitrogen atom, a sulfur atom, a linear structural unit having 1 to 20 carbon atoms and optionally containing a hetero-atom, or a non-aromatic ring structural unit, each of Ar
1
to Ar
4
is independently a substituted or non-substituted aromatic group or a substituted or non-substituted fused aromatic group, each of X
1
to X
4
is independently —O—, —S—, >C═O, >SO
2
, —(C
x
H
2x
)—O—(C
y
H
2y
)— (in which each of x and y is an integer of 0 to 20, while x+y=0 in no case), a substituted or non-substituted alkylidene group having 2 to 20 carbon atoms, a substituted or non-substituted alkylene group having 2 to 20 carbon atoms or a substituted or non-substituted divalent alicyclic residue, and each of R
1
to R
20
is independently a hydrogen atom, a halogen atom, a substituted or non-substituted alkyl group, a substituted or non-substituted alkoxy group, a substituted or non-substituted aromatic group, a substituted or non-substituted hetero-aromatic group or a substituted or non-substituted amino group (provided that adjacent groups of R
1
to R
5
, R
6
to R
10
, R
11
to R
15
, or R
16
to R
20
may bond to each other to form a fresh ring),
wherein E is a hydrogen atom or any adjacent two E's may bond to each other to form a fresh six-membered ring.
Further, according to the present invention, there is provided a light-emitting material of the formula [4] for an organic EL device,
wherein A, X
1
to X
4
and R
1
to R
20
are as defined above.
According to the present invention, further, there is provided a light-emitting material of the formula [5] for an organic EL device,
wherein A and R
1
to R
20
are as defined above, and each of Y
1
to Y
8
is a substituted or non-substituted alkyl group having 1 to 20 carbon atoms or a substituted or non-substituted aromatic group having 6 to 16 carbon atoms (provided that groups of Y
1
and Y
2
, Y
3
and Y
4
, Y
5
and Y
6
, or Y
7
and Y
8
may form a substituted or non-substituted alicyclic group having 5 to 7 carbon atoms).
Further, according to the present invention, there is provided an organic EL device comprising a light-emitting layer or a plurality of organic compound layers including the light-emitting layer and a pair of electrodes, the light-emitting layer or a plurality of the organic compound layers being sandwiched between a pair of the electrodes, wherein the light-emitting layer contains the above light-emitting material.
DETAILED DESCRIPTION OF THE INVENTION
In the compounds of the formulae [1], [4] and [5] in the present invention, A is a substituted or non-substituted divalent aromatic group, a substituted or non-substituted divalent fused aromatic group, a substituted or non-substituted divalent hetero-aromatic group, a substituted or non-substituted divalent fused hetero-aromatic group or a divalent group in which 2 to 10 identical or different groups out of the above groups are bonded to each other directly or through an oxygen atom, a nitrogen atom, a sulfur atom, or a linear or non-aromatic structural unit containing a hetero-atom. Those sites of A which bond to nitrogen atoms have a ring structure each.
Specific examples of A include substituted or non-substituted divalent aromatic or fused aromatic group residues of benzene, toluene, xylene, ethylbenzene, naphthalene, anthracene (excluding a case where 9- and 10-positions thereof bond), phenanthrene, fluorene, pyrene, chrysene, naphthacene, perylene, azulene, fluorenone, anthraquinone, dibenzosuberenone and tetracyanoquinodimethane, and divalent hetero-aromatic or fused-hetero-aromatic residues of furan, thiophene, pyrole, pyridine, pyrone, oxazole, pyrazine, oxadiazole, triazole, thiadiazole, indole, quinoline, isoquinoline, carbazole, acridine, thioxanthone, coumarin, acridone,
Enokida Toshio
Okutsu Satoshi
Onikubo Toshikazu
Tamano Michiko
Toyo Ink Manufacturing Co. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
Yamnitzky Marie
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