Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From hydrocarbon reactant
Reexamination Certificate
2001-06-19
2004-11-16
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From hydrocarbon reactant
C528S205000, C428S917000
Reexamination Certificate
active
06818733
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polymeric fluorescent substance and more specifically a polymer light-emitting device using the same (hereinafter, sometimes referred to as polymer LED).
2. Description of Related Art
Inorganic electroluminescence devices (hereinafter, sometimes referred to as inorganic EL device) using an inorganic luminescent material as a light emitting material have been used, for example, for flat 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, an organic electroluminescence device (hereinafter, sometimes referred to as organic EL device) has been fabricated 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 a photosensitive layer for electrophotography and the like (Japanese Patent Application Laid-Open (JP-A) No. 59-194393). Organic EL devices can emit a lot of colors easily with low driving voltage and high luminance, as compared with inorganic EL devices. Therefore a lot of trials have been reported 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, in addition to organic EL devices using mainly organic compounds having a lower molecular weight, polymer light emitting devices (hereinafter, sometimes referred to as polymer LEDs) using light emitting materials having a higher molecular weight have been proposed in for example WO 9013148, JP-A No. 3-244630, Appl. Phys. Lett., 58, 1982 (1991). WO 9013148 discloses in the examples thereof 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 No. 3-244630 contains examples of conjugated polymers which 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.
The polymeric fluorescent substance used in these polymer LEDs include polyfluorenes (Japanese Journal of Applied Physics, 30, L1941 (1991)), poly(p-phenylene) derivatives (Advanced Materials, 4, 36 (1992)) and the like, in addition to the above-mentioned poly(p-phenylene vinylene).
A light emitting layer can be easily produced for a polymer LED using a solvent-soluble polymeric fluorescent substance or precursor thereof, therefore, it is advantageous for increased area and decreased cost, as compared with vapor-deposition of a fluorescent substance of low molecular weight, and is also excellent in mechanical strength of the resulting film since it is a polymer.
Recently, there has been disclosed copolymers containing a polyarylenevinylene having an aryl group and a substituent on an arylene group constituting the main chain of the polyarylenevinylene, as a polymeric fluorescent substance (WO98/27136, WO99/24526).
These copolymers are excellent in light emitting property but stronger fluorescence is desired.
An object of the present invention is to provide a polymeric fluorescent substance composed of a copolymer containing an arylene or arylenevinylene having an aryl group, heterocyclic compound group or substituent on an arylene group constituting the main chain, and exibiting strong fluorescent, and to provide a high performance polymer LED which can be driven at low voltage and high efficiency using this polymeric fluorescent substance.
SUMMARY OF THE INVENTION
The above object and other objectives have been achieved by the present inventors who have intensively studied, in view of the above-mentioned conditions, and found that a polymeric fluorescent substance having the repeating units as described herein exibit particularly strong fluorescence, and that a high performance polymer LED which can be driven at low voltage and high efficiency can be obtained by using this polymeric fluorescent substance.
Namely, in accordance with the present invention there is provided a polymeric fluorescent substance exhibiting fluorescence in solid state. The substance has a polystyrene reduced number-average molecular weight of 5×10
4
to 1×10
8
, and containing one or more repeating units of the following general formula (1) and one or more repeating units of the following general formula (3), the total amount of the repeating units being 50 mol % or more based on the total amount of all repeating units, and the total amount of repeating units of the general formula (1) being 0.1 mol % to 15 mol % based on the total amount of repeating units of the general formulae (1) and (3):
wherein, Ar
1
represents an arylene group having 6 to 60 carbon atoms contained in the main chain part or a divalent heterocyclic compound group having 4 or more and 60 or less carbon atoms contained in the main chain part. Ar
2
represents an aryl group having 6 to 60 carbon atoms or a heterocyclic compound group having 4 to 60 carbon atoms. Ar
2
may further have a substituent. 1 represents an integer from 1 to 4, and m represents an integer from 1 to 4, however, l+m does not exceed the maximum possible number of substituents on Ar
1
in the formula (1), X represents an oxygen atom, sulfur atom or a group of the following general formula (2), R
3
represents a group selected from the group consisting of alkyl groups having 1 to 20 carbon atoms, aryl groups having 6 to 60 carbon atom, arylalkyl groups having 7 to 60 carbon atoms and heterocyclic compound groups having 4 to 60 carbon atoms, each of R
1
and R
2
independently represents a group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl groups having 6 to 60 carbon atoms, a heterocyclic compound groups having 4 to 60 carbon atoms and a cyano group. n is 0 or 1,
—CR
4
═CR
5
— (2)
wherein, each of R
4
and R
5
independently represents a group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 60 carbon atoms, a heterocyclic compound group having 4 to 60 carbon atoms and a cyano group,
—Ar
3
—(CR
6
═CR
7
)
k
— (3)
wherein, Ar
3
represents an arylene group having 6 to 60 carbon atoms contained in the main chain part thereof or a heterocyclic compound group having 4 to 60 carbon atoms contained in the main chain part. Ar
3
may have a substituent, however, does not simultaneously have substituents represented by —Ar
2
and —X—R
3
in the formula (1), each of R
6
and R
7
independently represents a group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 60 carbon atoms, a heterocyclic compound group having 4 to 60 carbon atoms and a cyano group, and k is 0 or 1.
The present invention also provides a polymer light emitting device comprising a pair of electrodes composed of an anode and a cathode one or both which is transparent or semitransparent, and one or more light emitting layers disposed between the electrodes, wherein the polymeric fluorescent substance described above is contained in said light emitting layer.
The present invention provides a flat light source, a segment display, and a dot matrix display all obtained by using the polymer light emitting device. The present invention also provides a liquid crystal display obtained by using the polymer light emitting device as a back-light.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The polymeric fluorescent substance of the present invention, and a polymer LED obtained by using the polymeric fluorescent substance will be described in detail below.
The polymeric fluorescent substance of the present invention is a polymeric fluorescent subs
Doi Shuji
Yamazaki Michio
Lee Rip A.
Sumitomo Chemical Company Limited
Wu David W.
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