Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2001-03-15
2004-04-13
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C313S504000, C313S506000, C252S301350, C427S066000, C349S069000, C528S129000, C528S230000, C528S247000, C528S266000, C528S373000, C528S397000
Reexamination Certificate
active
06720091
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polymeric fluorescent substance, a polymeric fluorescent substance solution, and a polymer light-emitting device (hereinafter, referred to as polymer LED) using the same.
2. Background Information
In polymer light-emitting devices (hereinafter, sometimes referred to as inorganic EL device) using an inorganic luminescent material as a light-emitting material are used for example for sheet light sources as back-lights and displays such as a flat panel display and the like, however, an alternating current of high voltage has been required for light emission.
Recently, there has been reported an polymer light-emitting device (hereinafter, sometimes referred to as organic EL device) having a double-layer structure in which an organic fluorescent dye as a light-emitting layer is laminated with an organic charge transport compound used in photosensitive layer for electrophotography and the like (Japanese Patent Application Laid-Open (JP-A) No. 59-194393). Since organic EL devices have characteristics that light emissions of a lot of colors are obtained easily in addition to low voltage driving and high luminance as compared with inorganic EL devices, there have been reported a lot of trials regarding device structures, organic fluorescent dyes and organic charge transport compounds of organic EL devices [Jpn. J. Appl. Phys., 27, L269 (1988), J. Appl. Phys., 65, 3610 (1989)].
Further, apart from organic EL devices using mainly organic compounds having a lower molecular weight, polymer light-emitting devices using light-emitting materials having a higher molecular weight have been proposed in such as WO 9013148 published specification, JP-A No. 3-244630, Appl. Phys. Lett., 58, 1982 (1991). WO 9013148 discloses in the Examples an EL device using a thin film of poly(p-phenylene vinylene) obtained by forming a film of a soluble precursor on the electrode and subjecting it to a heat treatment to convert the precursor into a conjugated polymer.
Further, JP-A 3-244630 has exemplified conjugated polymers having a feature that they are themselves soluble in a solvent and needs no heat treatment. Also in Appl. Phys. Lett., 58, 1982(1991), apolymeric light-emitting materials soluble in a solvent and a polymer LED fabricated using the same are described.
Conventionally, as the light-emitting materials used in these polymer LEDs, in addition to the above-described poly(p-phenylene vinylene), there have been reported polyfluorene (Jpn. J. Appl. Phys., 30, L1941 (1991)), poly p-phenylene derivative (Adv. Mater., 4, 36 (1992)) and the like.
Since polymer LED can be film formed as an organic layer easily by coating with using a soluble polymeric fluorescent substance, it is advantageous to large area formation, or cost lowering, in comparison with the case where a low molecule fluorescent substance is deposited, and as it is a polymer, mechanical strength of the film is also excellent.
However, even if polymer LED is manufactured with using the same polymeric fluorescent substance, the luminous efficiency of polymer LED may change with manufacture conditions of the polymeric fluorescent substance or the polymeric fluorescent substance solution used for coating etc. Thus a polymeric fluorescent substance or a polymeric fluorescent substance solution which can attain high luminous efficiency as polymer LED has been required.
Moreover, it is known that, in an organic electroluminescence device, a defect called dark spots by which the light is not emitted tends to generate, and the growth of dark spots deteriorates remarkably the display quality of the organic electroluminescence device. In order to solve this problem, disclosed are a method of suppressing generation of dark spots, and a method of suppressing growth of dark spots (JP-A 9-148066 official report).
About the method of suppressing generation of dark spots, JP-A 10-172768 suggests that they are generated from the defects of a transparent electrode substrate, for example, projections of a transparent electrode, cracks of glass and exterior adhesion particles, and discloses a method of reducing density of defects of a transparent electrode substrate. JP-A 6-124785 discloses a method of reducing foreign materials, projections, and holes in the high polymer film, at the interface of the high polymer film and the 1st electrode, and at the surface of the 1st electrode, in a device using an electrode on a high polymer film.
Especially when using polymeric materials for an organic electroluminescence device, for example, JP-A 8-188773, 7th page describes when forming a thin film from a hole transporting polymer solution by coating, the solution is filtrated with a 0.1 &mgr;m filter and used. JP-A-2000-48960, page 18 describes the use of the solution filtrated with a 0.45 &mgr;m filter, for coating a solution of a polythiophene derivative from as charge injection layer material, and polyvinyl carbazole as a hole transportation layer material. JP-A 9-124733 describes that, when using a vinyl type polymer as a luminescence polymer, a solution is filtrated with a 0.2 &mgr;m filter before the application.
Moreover, JP-A 9-104732 describes that a solution of a polymer in which conjugated structure is bonded by ether group is filtrated with a micro filter, and the solution is coated. However, it is not described that a device having few dark spots with using a conjugated polymer for an organic light emitting layer.
An object of the present invention is to provide a polymeric fluorescent substance or polymeric fluorescent substance solution which can attain higher luminous efficiency as a polymer LED, a polymer LED thereof, and a process for producing the same.
Another object is to provide an organic electroluminescence device using a conjugated polymer and having few dark spots for the organic light emitting layer.
As a result of extensive studies, the present inventors have found that a polymer LED produced with using a polymeric fluorescent substance having a specific content of water or poor solvent, or a polymeric fluorescent substance solution containing a specific content of water or poor solvent, has a high luminous efficiency. The present inventors also have found that a polymer LED comprising at least one light-emitting layer containing substantially no particle-like foreign material having a diameter of more than 1 &mgr;m can provide a polymer LED having few dark spots with keeping the characteristics of the polymer LED.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates to followings.
[1] A polymeric fluorescent substance which emits fluorescence in solid state, has a number-average molecular weight in terms of polystyrene of 1×10
3
to 1×10
7
, and at least one repeating unit of the following general formula (1), and the amount of water content measured by Karl-Fischer method is not more than 1000 ppm (weight):
—Ar
1
—(CR
1
═CR
2
)
k
— (1),
in the formula, Ar
1
is a divalent group forming carbon-carbon bonds with adjacent two groups respectively, the divalent group being an arylene group having 6 to 60 carbon atoms participating in conjugation or a heterocyclic compound group having 4 to 60 carbon atoms participating in conjugation, and the arylene group and heterocyclic compound group may further have a substituent; each of R1 and R2 independently represents a group selected from the group consisting of hydrogen atom, linear, branched or cyclic alkyl groups having 1 to 20 carbon atoms, aryl groups having 6 to 60 carbon atoms, heterocyclic compound groups having 4 to 60 carbon atoms and a cyano group, and the aryl group and heterocyclic compound group may further have a substituent; and the symbol k is 0 or 1.
[2] A polymeric fluorescent substance solution containing 0.1 to 5% by weight of a polymeric fluorescent substance which emits fluorescence in solid state, has a number-average molecular weight in terms of polystyrene of 1×10
3
to 1×10
7
, and has at least one repe
Noguchi Takanobu
Ohnishi Toshihiro
Sasaki Shigeru
Tsubata Yoshiaki
Ueda Masato
Garrett Dawn
Kelly Cynthia H.
Sughrue & Mion, PLLC
Sumitomo Chemical Company Limited
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