Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2002-08-29
2003-05-13
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S704000, C428S917000, C257S040000, C257S103000, C313S504000, C313S506000, C252S301160, C252S301350
Reexamination Certificate
active
06562485
ABSTRACT:
RELATED COPENDING APPLICATIONS AND PATENTS
Illustrated in copending applications U.S. Ser. No. 09/770,159, filed Jan. 26, 2001, the disclosure of which is totally incorporated herein by reference, is an organic light emitting device comprising in an optional sequence
(i) a substrate;
(ii) a first electrode;
(iii) a mixed region comprising a mixture of a hole transport material and an electron transport material, and wherein this mixed region includes at least one organic luminescent material;
(iv) a second electrode;
(v) a thermal protective element coated on the second electrode; wherein, one of the two said first and second electrodes is a hole injection anode, and one of the two said electrodes is an electron injection cathode, and wherein the organic light emitting device further comprises;
(vi) a hole transport region, interposed between the anode and the mixed region, wherein the hole transport region optionally includes a buffer layer; and
(vii) an electron transport region interposed between the second electrode and the mixed region; and in U.S. Ser. No. 09/770,154, filed Jan. 26, 2001, the disclosure of which is totally incorporated herein by reference, is an organic light emitting device comprising in sequence
a substrate;
a first electrode;
a light-emitting region comprising an organic luminescent material; and
a second electrode.
Illustrated in U.S. Pat. Nos. 5,942,340; 5,952,115; 5,932,363; 5,925,472, and 5,891,587, the disclosures of which are totally incorporated herein by reference, are EL devices. In U.S. Pat. No. 5,925,472, the disclosures of which are totally incorporated herein by reference, there are disclosed organic EL devices with blue luminescent materials comprised of metal chelates of oxadiazole compounds, and which devices may provide a greenish blue color.
Illustrated in U.S. Pat. No. 6,057,048, the disclosure of which is totally incorporated herein by reference, is an electroluminescent device comprised of an anode, a hole transporting layer, a light emitting layer, and a cathode, wherein said light emitting layer contains a component of the formula
wherein Ar
1
, Ar
2
, Ar
3
, and Ar
4
are each independently aryl or optionally aliphatic; R
1
and R
2
are independently selected from the group consisting of hydrogen, aliphatic, halogen, and cyano; L is a suitable linking group; and n is a number of from 0 to about 3.
The appropriate components and processes of the above patents and copending applications may be selected for the present invention in embodiments thereof.
BACKGROUND OF THE INVENTION
This invention is directed to organic electroluminescent (EL) devices, and more specifically, to organic EL devices with a number of excellent performance characteristics inclusive of the enablement of blue emitting EL devices, which devices contain luminescent components or a luminescent component with excellent high thermal stability, film forming characteristics and intense blue fluorescence. Organic EL devices are desired that are capable of providing uniform luminescence, saturated color especially in the blue regions of the visible spectrum, and low driving voltages. The organic EL devices of the present invention enable in embodiments the above characteristics and which devices contain organic luminescent materials or light emitting components comprised of fluorescent hydrocarbon compounds, and which devices can be selected for use in flat-panel emissive display technologies, including TV screens, computer screens, and the like.
PRIOR ART
A simple organic EL device can be comprised of a layer of an organic luminescent material conductively sandwiched between an anode, typically comprised of a transparent conductor, such as indium tin oxide, and a cathode, typically a low work function metal such as magnesium, calcium, aluminum, or the alloys thereof with other metals. The EL device functions on the principle that under an electric field, positive charges (holes) and negative charges (electrons) are respectively injected from the anode and cathode into the luminescent layer and undergo recombination to form excitonic states which subsequently emit light. A number of prior art organic EL devices have been prepared from a laminate of an organic luminescent material and electrodes of opposite polarity, which devices include a single crystal material, such as single crystal anthracene, as the luminescent substance as described, for example, in U.S. Pat. No. 3,530,325. However, these devices usually require excitation voltages on the order of 100 volts or greater.
In U.S. Pat. No. 4,539,507 there is disclosed an EL device formed of a conductive glass transparent anode, a hole transporting layer of 1,1-bis(4-p-tolylaminophenyl)cyclohexane, an electron transporting layer of 4,4′-bis(5,7-di-tert-pentyl-2-benzoxzolyl)stilben, and an indium cathode.
U.S. Pat. No. 4,720,432 discloses an organic EL device comprising a dual-layer hole injecting and transporting zone, one layer being comprised of porphyrinic compounds supporting hole injection and the other layer being comprised of aromatic tertiary amine compounds supporting hole transport.
U.S. Pat. No. 4,769,292 discloses an EL device employing a luminescent zone comprised of an organic host material capable of sustaining hole-electron recombination and a fluorescent dye material capable of emitting light in response to energy released by hole-electron recombination. A preferred host material is an aluminum complex of 8-hydroxyquinoline, namely tris(8-hydroxyquinolinate)aluminum.
While recent progress in organic EL research has elevated the potential of organic EL devices for widespread applications, the performance levels of a number of current available devices, especially with respect to blue emission, may still be below expectations. Further, for visual display applications, organic luminescent materials should provide a satisfactory color in the visible spectrum, normally with emission maxima at about 460, 550 and 630 nanometers for blue, green and red. These organic EL devices may comprise a light-emitting layer which is comprised of a host material doped with a guest fluorescent material that is responsible for color emission. For efficient down-shifting of EL emission wavelength in the host-guest emitting layer, it may be desirable that the host material should fluorescence in the blue or shorter wavelength region. In many conventional organic EL devices, the luminescent zone or layer is formed of a green-emitting luminophor of tris(8-hydroxyquinolinate)aluminum with certain fluorescent materials. U.S. Pat. No. 5,409,783 discloses a red-emitting organic EL device by doping the tris(8-hydroxyquinolinate)aluminum layer with a red fluorescent dye. However, up-shifting of the tris(8-hydroxyquinolinate)aluminum emission to blue region is believed to be highly inefficient. Although there have been. several disclosures describing blue-emitting organic EL devices, for example in U.S. Pat. Nos. 5,151,629 and 5,516,577, the disclosures of which are totally incorporated herein by reference, their performance characteristics still possess many disadvantages such as poor emission hue, high operation voltages, low luminance, and poor operation stability. Thus, there continues to be a need for improved luminescent compositions for organic EL devices, which may vacuum evaporable and form thin films with excellent thermal stability. There is also a need for luminescent compositions which are capable of providing uniform and satisfactory emission in the blue region of the light spectrum. In particular, there is a need for efficient blue luminescent materials for organic EL devices, which may optionally be doped with a fluorescent dye. Further, there is also a need for luminescent compositions which can enhance charge transporting characteristics, thus lowering device driving voltages. Therefore, a primary feature of the present invention is to provide luminescent materials comprised of certain fluorescent hydrocarbon compounds, which in comparison to certain EL devices comprised of the metal chelates of oxadiaz
Aziz Hany
Hu Nan-Xing
Jain Poonam
Popovic Zoran D.
Jones Deborah
Thompson Robert
Xerox Corporation
Xu Ling
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