Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-05-10
2001-11-06
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C313S504000, C313S506000, C252S301160, C556S432000
Reexamination Certificate
active
06312839
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a blue-light emitting compound having fluorene side chains with superior emission efficiency, and a display device adopting the blue-light emitting compound as a color developing substance.
2. Description of the Related Art
Electroluminescence (EL) devices as a self-luminous type display give numerous advantages such as a broad viewing angle, a good contrast characteristic and a rapid response time. EL devices are classified into an inorganic EL device and an organic EL device depending on the material used for an emitter layer. In particular, the organic EL device has good luminance, turn-on voltage and response time characteristics and allows for full color display, compared to the inorganic EL device.
A general organic EL device includes an anode, a hole transporting layer, an emitter layer, an electron transporting layer and a cathode which are sequentially stacked on a substrate. The hole transporting layer, the emitter layer and the electron transporting layer are organic thin films formed of an organic compound.
The organic EL device having such a structure operates based on the following operational principle. As a voltage is applied between the anode and the cathode, holes injected from the anodes migrate through the hole transporting layer into the emitter layer. Meanwhile, electrons injected from the cathode migrate through the electron transporting layer into the emitter layer. In the emitter layer, excitons are generated by recombination of carriers, and transited from an excited state to ground state, so that fluorescent molecules of the emitter layer emit light, forming a picture.
An organic EL device adopting an aromatic diamine and aluminum complex having a low molecular weight has been developed by Eastman Kodak Company (Appl. Phys. Lett. 51, 913, 1987). Blue-light emitting substances, such as diphenylanthracene, tetraphenylbutadiene and distyryl benzene derivatives, have been disclosed, but their poor stability causes easy crystallization of thin films. EP 388,768 teaches diphenyldistyryl series blue-emitting materials with improved thin film stability, which hinders crystallization of thin film by adopting phenyl groups at its side chains. Also, distyrylanthracene derivatives, in which electron acceptors and electron donors coexist, have been developed by Kyushu University (Japan), which result in improved thin film stability (Pro. SPIE, 1910, 180 (1993)).
However, these blue light-emitting compounds lead to a reduction in the emission efficiency and need improvement of thin film stability, and thus a need for a novel blue-light emitting compound for blue-light emitting devices or full-color light-emitting devices, has increased.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a blue-light emitting compound with improved emission efficiency.
It is another object of the present invention to provide a display device adopting the blue-light emitting compound as a color developing substance.
The first object of the present invention is achieved by a blue light-emitting compound having fluorene side chains, the compound having the formula (1)
where a
1
and a
2
are independently selected from the group consisting of alkyl group of 1 to 20 carbon atoms, —SiR
3
, and hydrogen; b
1
and b
2
are independently selected from the group consisting of alkyl group of 1 to 20 carbon atoms, aryl group of 6 to 20 carbon atoms, and —SiR
3
; and R is alkyl group of 1 to 10 carbon atoms.
Preferably, a
1
and a
2
are independently selected from the group consisting of t-butyl group and trimethylsilyl; and b
1
and b
2
are independently selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl and phenyl groups.
The second object of the present invention is achieved by a display device adopting the light-emitting compound having fluorene side chains. An embodiment for the second object of the present invention provides an organic electroluminescence device adopting the light-emitting compound with fluorene side chains as a color developing substance.
To achieve the second object of the present invention, there is provided an organic electroluminescence device having an organic layer between a pair of electrodes, wherein the organic layer comprises the compound with fluorene side chains having the formula (1) hereinabove.
REFERENCES:
patent: 5876864 (1999-03-01), Kim et al.
Kim Dong-Hyun
Kim Yun-hi
Kwon Soon-ki
Shin Dong-cheol
Yu Han-sung
Garrett Dawn L.
Kelly Cynthia H.
Leydig , Voit & Mayer, Ltd.
Samsung Display Devices Co. Ltd.
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