Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2001-04-20
2003-09-02
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C313S504000, C313S506000
Reexamination Certificate
active
06613454
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an organic electroluminescent (EL) device, and more particularly, to a compound for use in a device of the type wherein an electric field is applied across a thin film of an organic compound to emit light.
2. Background Art
Organic electroluminescent (EL) devices include a thin film containing a luminescent organic compound interleaved between an electron injecting electrode and a hole injecting electrode. Electrons and holes are injected into the thin film where they are recombined to create excitons. Light is emitted by utilizing luminescence (phosphorescence or fluorescence) upon deactivation of excitons.
The organic EL devices are characterized by plane light emission at a high luminance of about 100 to 10,000 cd/m
2
with a voltage of about 10 volts and light emission in a spectrum from blue to red color by a simple choice of the type of fluorescent material.
Doping is one technique for producing light emission of any desired color from organic EL devices. It was reported in Jpn. J. Appl. Phys., 10, 527 (1971) to change emission color from blue to green by doping anthracene crystals with a minor level of tetracene. With respect to organic thin film EL devices having a multilayer structure, it was reported in JP-A 63-264692 to incorporate in a host material having a light emitting function a minor amount of a fluorescent dye capable of emitting light different from that of the host material in response to light emission from the host material as a dopant to form a light emitting layer, thereby changing the color of light emission from green to orange or red.
With respect to long wavelength light emission of yellow to red, known light emitting materials or dopant materials include laser dyes capable of red oscillation (EPO 281381), compounds capable of exciplex emission (JP-A 2-255788), perylene compounds (JP-A 3-791), coumarin compounds (JP-A 3-792), dicyanomethylene compounds (JP-A 3-162481), thioxanthene compounds (JP-A 3-177486), mixtures of a conjugated polymer and an electron transporting compound (JP-A 6-73374), squalirium compounds (JP-A 6-93257), oxadiazole compounds (JP-A 6-136359), oxynate derivatives (JP-A 6-145146), and pyrene compounds (JP-A 6-240246).
It is reported in J. Am. Chem. Soc., 118, 2374-2379, 1996, that benzofluoranthene derivatives have a very high fluorescent quantum yield. JP-A 10-330295 and JP-A 11-233261 disclose organic EL devices having a light emitting layer in which a variety of host materials are doped with dibenzo[f,f′]diindeno[1,2,3-cd:1′,2′,3′-lm]perylene derivatives derived from benzofluoranthene.
Other light emitting materials disclosed heretofore include condensed polycyclic aromatic compounds (JP-A 5-32966 and 5-214334). Also dopant materials proposed heretofore include various condensed polycyclic aromatic compounds (JP-A 5-258859).
However, when these materials are used as the dopant, EL devices often fail to allow dopant molecules to exert their own fluorescence due to the interaction between dopants or between the dopant and the host.
Therefore, with respect to organic EL devices of the type in which a host material is doped with a fluorescent dye, a choice of host material is an important and difficult task in order for the device to produce high efficiency light emission. Currently available organic EL devices fail to reach a practically acceptable level of emission efficiency although fluorescent dyes having a high fluorescent quantum yield are used as the dopant.
When organic EL devices are fabricated using the doping technique, the energy transfer from host molecules in the excited state to the dopant is not 100%, and often not only the dopant, but also the host material emit light. Especially in the case of red light emitting devices, the chromatic purity is often exacerbated by faint light emission of the host material since the host material emits light in a wavelength region of higher visibility than the dopant. Further improvements in properties pertaining to the luminous lifetime and durability are needed, with the target placed on practical application.
SUMMARY OF THE INVENTION
An object of the invention is to provide an organic EL device capable of light emission to a satisfactory luminance, especially in a long wavelength region, and with a chromatic purity sufficient for use in full color displays, and having a sufficient durability to sustain such improved light emission performance over a long time.
The above and other objects are achieved by the invention which is defined below.
[1] An organic EL device comprising one or more organic layers between a pair of electrodes participating in at least a light emitting function,
at least one of the organic layers containing at least one of organic compounds having basic skeletons of the following formulas (I) to (IV) and at least one organic compound having a skeleton of the following formula (V) at the same time:
wherein Q
1
to Q
8
are independently hydrogen or substituted or unsubstituted alkyl, aryl, amino, heterocyclic or alkenyl radicals,
wherein R
1
, R
2
, R
3
and R
4
are independently aryl, fluorene, carbazolyl, alkyl, alkoxy, aryloxy, amino or halogen radicals, at least one of R
1
, R
2
, R
3
and R
4
is aryl, r1, r2, r3 and r4 each are 0 or an integer of 1 to 5, with the proviso that r1, r2, r3 and r4 are not 0 at the same time, R
5
and R
6
are independently alkyl, alkoxy, amino, aryl or halogen radicals and may be the same or different, r5 and r6 each are 0 or an integer of 1 to 4,
wherein A
101
is a monophenylanthryl or diphenylanthryl radical and may be the same or different, L is hydrogen, a single bond or an n-valent linkage, and n is an integer of 1 to 4,
Q
n
−L
101
(IV)
wherein Q is a pyrazinyl radical having fused thereto a six-membered aromatic ring containing 0 to 2 nitrogen atoms and may be the same or different, n is 2 or 3, and L
101
is a single bond or n-valent radical,
wherein X
1
to X
10
, L
1
and L
2
are independently hydrogen, halogen atoms, straight, branched or cyclic alkyl radicals which may have substituents, straight, branched or cyclic alkoxy radicals which may have substituents, straight, branched or cyclic alkylthio radicals which may have substituents, straight, branched or cyclic alkenyl radicals which may have substituents, straight, branched or cyclic alkenyloxy radicals which may have substituents, straight, branched or cyclic alkenylthio radicals which may have substituents, substituted or unsubstituted aralkyl radicals, substituted or unsubstituted aralkyloxy radicals, substituted or unsubstituted aralkylthio radicals, substituted or unsubstituted aryl radicals, substituted or unsubstituted aryloxy radicals, substituted or unsubstituted arylthio radicals, substituted or unsubstituted amino radicals, cyano, hydroxyl, —COOR
1
radicals (wherein R
1
is hydrogen, a substituted or unsubstituted straight, branched or cyclic alkyl radical, a substituted or unsubstituted straight, branched or cyclic alkenyl radical, a substituted or unsubstituted aralkyl radical or a substituted or unsubstituted aryl radical), —COR
2
radicals (wherein R
2
is hydrogen, a substituted or unsubstituted straight, branched or cyclic alkyl radical, a substituted or unsubstituted straight, branched or cyclic alkenyl radical, a substituted or unsubstituted aralkyl radical, a substituted or unsubstituted aryl radical or an amino radical), or —OCOR
3
radicals (wherein R
3
is a substituted or unsubstituted straight, branched or cyclic alkyl radical, a substituted or unsubstituted straight, branched or cyclic alkenyl radical, a substituted or unsubstituted aralkyl radical, or a substituted or unsubstituted aryl radical), or at least two adjoining radicals selected from X
1
to X
10
, L
1
and L
2
may bond or fuse together to form a substituted or unsubstituted carbocyclic aliphatic ring, aromatic ring or fused aromatic ring with the carbon atoms to which they ar
Ara Kensuke
Fujita Tetsuji
Inoue Tetsushi
Garrett Dawn
Kelly Cynthia H.
TDK Corporation
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