Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-01-05
2003-08-05
Lipman, Bernard (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S286000, C526S310000, C526S312000, C526S320000, C526S334000
Reexamination Certificate
active
06602969
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polymeric fluorescent substance, a polymer light-emitting device (hereinafter, referred to as polymer LED), and a device using the same.
2. Description of the Related Art
Inorganic electroluminescence 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 organic electroluminescence 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). WO9013148 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 a 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), a polymeric light-emitting materials soluble in a solvent and a polymer LED fabricated using the same are described.
Polymer LEDs are advantageous for formation of a film having large area and reduction in cost since an organic layer can be easily formed by coating with using a polymeric fluorescent substance soluble in organic solvents, as compared with the case of vapor deposition of a material having a lower molecular weight, and the mechanical strength of the resulting film is believed to be high because of a high molecular weight thereof.
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.
In order to utilize the film-formable characteristics of a polymeric fluorescent substance by coating, there have been demanded a polymeric fluorescent substance having excellent solubility in organic solvents. To realize the practical falt panel display, there have been demanded a polymer LED having high efficiency and long.
The object of the present invention is to provide a polymeric fluorescent substance having more excellent solubility to organic solvents, a polymer LED having high performance which can be driven at high efficiency and longer lifetime using said polymeric fluorescent substance.
SUMMARY OF THE INVENTION
As a result of intensive studies, the present inventors have found that a polymeric fluorescent substance having a specific carrier drift mobility and a specific repeating unit is more excellent in solubility to organic solvents, and has higher efficiency and longer lifetime in applying as a polymer LED, and reached to the completion of the present invention.
Namely, the present invention relates to [1] a polymer fluorescent substance which emits fluorescence in solid state, has a number-average molecular weight in terms of polystyrene of 1×10
4
to 1×10
8
, has at least one repeating unit of the following general formula (1) and in which the ratio of the hole drift mobility &mgr;
H
to the electron drift mobility &mgr;
E
of said polymer fluorescent substance is from 0.1 to 10:
[in the formula, Ar
1
is an arylene group having 6 to 60 carbon atoms contained in the main chain portion or a divalent heterocyclic compound group having 3 to 60 carbon atoms contained in the main chain portion].
Moreover, the present invention relates to [2] a polymer fluorescent substance which emits fluorescence in solid state, has a number-average molecular weight in terms of polystyrene of 1×10
4
to 1×10
8
, and has each of the repeating units represented by the formulae (2), (3) and (4):
[in the formula, Ar
2
is an arylene group having 6 to 60 carbon atoms contained in the main chain portion or a divalent heterocyclic compound group having 3 to 60 carbon atoms contained in the main chain portion],
[in the formula, Ar
3
is an arylene group having 6 to 60 carbon atoms contained in the main chain portion or a heterocyclic compound group having 3 to 60 carbon atoms contained in the main chain portion.],
[in the formula, Ar
5
is an arylene group having 6 to 60 carbon atoms contained in the main chain portion or a divalent heterocyclic compound group having 3 to 60 carbon atoms contained in the main chain portion].
Moreover, the present invention relates to [3] a polymer light-emitting device comprising at least one light-emitting layer containing a polymer fluorescent substance, placed between a pair of an anode and a cathode at least one of which is transparent or semi-transparent, wherein, the light-emitting layer contains a polymer fluorescent substance of above described [1] or [2].
Further, the present invention relates to [4] a sheet light source using a polymer light-emitting device of above described [3].
Next, the present invention relates to [5] a segment display apparatus using a polymer light-emitting device of above described [3].
Next, the present invention relates to [6] a dot matrix display apparatus using a polymer light-emitting device of above described [3].
And, the present invention relates to [7] a liquid crystal display apparatus using a polymer light-emitting device of above described [3].
DETAILED DESCRIPTION OF THE INVENTION
The polymeric fluorescent substance and a polymer LED using the same will be described in detail below.
The polymeric fluorescent substance of the present invention is a polymeric fluorescent substance which emits a fluorescence in solid state and having a number-average molecular weight of 1×10
4
to 1×10
8
in terms of polystyrene, wherein the substance contains at least one repeating unit represented by the above-described formula (1). More preferably the substance contains each one or more of repeating units represented by the above-described formula (2), formula (3) or formula (4), respectively.
In the above formula (1), 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 3 to 60 carbon atoms participating in conjugation, and the arylene group and heterocyclic compound group may further have a substituent. Each of R
1
and R
2
independently represents a group selected from the group consisting of a 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 3 to 60 carbon atoms and a cyano group, and the aryl group and he
Noguchi Takanobu
Ueda Masato
Lipman Bernard
Sumitomo Chemical Company Limited
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