Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2001-08-17
2004-02-10
Yamnitzky, Marie (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C313S504000, C313S506000, C257S102000, C257S103000
Reexamination Certificate
active
06689493
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to an organic electroluminescent (EL) element, and more specifically to the red organic EL element having excellent luminescent efficiency, brightness and chromaticity, and an organic EL display using the organic EL element.
(b) Description of the Related Art
In a conventional organic EL element, especially a conventional red organic EL element, an ordinarily used luminescent organic aluminum complex having a higher fluorescent quantum yield, or an aromatic amine derivative is used as a host, and the host doped with a red light emitting material is used as a luminescent layer for obtaining the brightness in a practical use.
The luminescent organic aluminum complex is designated by (Q)
3
-Al (general formula [a], wherein “Q” is a substituted or non-substituted 8-quinolinolate ligand), and the aromatic amine derivative is designated by a general formula [b] (wherein each of A1 to A4 independently designates an aryl group having a carbon number between 6 and 18, and each of tR1 to R8 independently designates a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryl group or an amino group).
For example, in the organic EL element described in “An Overview of Organic Electroluminescent Materials and Devices”, SID 96DIGEST, 14.1, pp.181-184 (1996) by C. W. Tang, a luminescent layer is prepared by doping a luminescent organic aluminum complex [tris-(8-quinolinolate) aluminum] designated by a compound [4] acting as a host, with a red luminescent material (DCJT). JP-A-10(1998)-72581 describes a luminescent layer formed by the aromatic amine derivative acting as a host, designated by the general formula [b], and doped with a red luminescent material.
From the practical standpoint, the current organic EL element requires thermal stability. Accordingly, a hole injecting layer with the resistance to higher temperature is inserted between the anode and a hole transporting layer. Although the hole injecting layer extends a period of life of the organic EL element, the hole injecting ability into the luminescent layer is deteriorated. As a result, a recombination yield in the luminescent layer is lowered and a sufficient luminescent efficiency cannot be obtained. Further, a problem arises that an electron leaks from the luminescent layer due to an applied voltage, or a carrier balance is changed so that the hole transporting layer itself emits light to change the color shade.
A conventional organic EL element will be described with reference to the annexed drawing.
As shown in
FIG. 1
, the conventional organic EL element includes a transparent anode
12
made of ITO (indium-tin oxide), a hole injecting layer
13
, a hole transporting layer
14
, a luminescent layer
15
, an electron transporting layer
16
and a cathode
17
sequentially stacked on a glass substrate
11
. The luminescent layer
15
includes, as a host, an organic metal complex having a higher fluorescent quantum yield (general formula [a]), doped with the red light emitting material. The same or another organic metal complex (general formula [a]) having the electron transporting ability may be used in the electron transporting layer
16
.
As mentioned before, the use of the hole injecting layer with the resistance to higher temperature provides the reduction of the recombination yield between the hole and the electron in the luminescent layer, accompanied by the change of the color shade. Accordingly, the organic EL device having the excellent luminescent efficiency, the higher brightness and the permanently stabilized chromaticity cannot be conventionally obtained. This is because the hole injecting ability into the luminescent layer is low, and the electron transporting ability is changed due to increase of a voltage so that the recombination normally occurring in the luminescent layer actually occurs in the hole transporting layer in place of the luminescent layer.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide an organic EL element having excellent luminescent efficiency, brightness and chromaticity.
The present invention provides an organic EL element including an anode and a cathode opposing to each other, and at least one luminescent layer, positioned therebetween, including an aromatic amine derivative designated by a general formula [1], [4], [5] or [6] and a dibenzo-{[f,f′]-4,4′,7,7′-tetraphenyl}-diindeno-[1,2,3-cd:1′,2′,3′-lm] perylene derivative designated by a general formula [2].
Wherein each of R1 to R 28 is independently selected from the group consisting of 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 aryl group and a substituted or non-substituted amino group, each of Y1 to Y4 is independently selected from the group consisting of O, S, SO
2
, CO═O, CH
2
O, CH
2
OCH
2
and a substituted or non-substituted alkylene group, and two of R1 to R4 and/or two of R5 to R8 may be bonded to form a substituted or non-substituted five-membered or six-membered ring.
Wherein each of R1 to R 28 is independently selected from the group consisting of 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 aryl group and a substituted or non-substituted amino group, each of Y1 to Y4 is independently selected from the group consisting of O, S, SO
2
, C═O, CH
2
O, CH
2
OCH
2
and a substituted or non-substituted alkylene group, and two of R1 to R4 and/or two of R5 to R8 may be bonded to form a substituted or non-substituted five-membered or six-membered ring.
Wherein each of R1 to R 28 is independently selected from the group consisting of 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 aryl group and a substituted or non-substituted amino group, each of X1 to X8 is independently selected from the group consisting of a substituted or non-substituted alkyl group having a carbon number of 1 to 20 and a substituted or non-substituted aryl group having a carbon number of 6 to 16, and two of R1 to R4 and/or two of R5 to R8 may be bonded to form a substituted or non-substituted five-membered or six-membered ring.
Wherein each of R1 to R 28 is independently selected from the group consisting of 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 aryl group and a substituted or non-substituted amino group, and two of R1 to R4 and/or two of R5 to R8 may be bonded to form a substituted or non-substituted five-membered or six-membered ring.
wherein each of X1 to X20 is independently selected from the group consisting of 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 aryl group and a substituted or non-substituted amino group, and two of X1 to X20 may be bonded to form a substituted or non-substituted five-membered or six-membered ring.
In accordance with the present invention, the aromatic amine derivative and the perylene derivative in the luminescent layer can provide an excellent hole transporting ability (electron blocking ability) to the luminescent layer. As a result, the hole injecting efficiency into the luminescent layer is improved to elevate the recombination efficiency between the hole and the electron in the luminescent layer, thereby providing the higher brightness. The luminescent layer also acts as an electron blocking layer to prevent the permeation of the electron through the luminescent layer, thereby elevating the purity of the col
Motomatsu Toshihiko
Sakaguchi Yoshikazu
Hayes & Soloway P.C.
NEC Corporation
Yamnitzky Marie
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