Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-03-31
2003-02-18
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S691000, C428S917000, C428S704000, C313S504000, C313S506000, C528S129000, C528S153000, C528S154000, C528S230000, C528S244000, C528S247000, C528S248000, C528S266000, C528S269000, C528S373000, C528S397000
Reexamination Certificate
active
06521359
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) containing the same in an light emitting layer, 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 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, Tang et al. fabricated 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 (hereinafter, sometimes referred to as polymer LEDs) 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, 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, 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 addition to the above-described poly(p-phenylene vinylene).
As light emitting materials having other than linear or branched alkyl groups, alkoxy groups or aryl groups as a side chain, there have been reported a polythiophene derivative having a cycloalkyl group as a side chain (Nature, 372, 444 (1994)), and poly(p-phenylenevinvlene) having an alkoxy group of a cholesteric compound (WO94/20589 published specification).
PPV having a phenyethenyl group as a side chain has been reported in Macromolecules, 27, No. 19, 5239 (1994). Since this polymer is not necessarily soluble in a solvent, a PPV derivative thin film is obtained by forming a thin film of an intermediate then by conducting heat treatment, however, the light emitting property of this polymer was not known.
However, there have been required further improvements in the quantum yield of luminescence of light emitting materials, and the driving voltage and light emitting efficiency of light emitting materials when used in polymer LEDs.
The object of the present invention is to provide a polymeric fluorescent substance emitting strong fluorescence, a polymer LED and a device having high performance which can be driven at low voltage at high efficiency by using the polymeric fluorescent substance.
SUMMARY OF THE INVENTION
The present inventors have intensively studied in view of such conditions, and resultantly found that a polymeric fluorescent substance containing a repeating unit having a specific substituent emits especially strong fluorescence and a polymer LED and a device having high performance which can be driven at low voltage at high efficiency are obtained by using this polymeric fluorescent substance, completing the present invention.
Namely, the present invention relates to
[1] a polymeric fluorescent substance which emits a fluorescence in a solid state, has a number-average molecular weight of 10
3
to 10
8
in terms of polystyrene, comprises one or more repeating units of the following formula (1) and in which the total amount of the above-described repeating units is 20 mol % or more based on the total amount of all repeating units:
(wherein, Ar
1
is an arylene group of 6 to 60 carbon atoms contained in the main chain or a heterocyclic compound group of 4 to 60 carbon atoms contained in the main chain. Ar
2
is a group selected from the group consisting of aryl groups of 6 to 60 carbon atoms, heterocyclic compound groups of 4 to 60 carbon atoms and cyclic saturated hydrocarbon groups of 5 to 16 carbon atoms. X
1
represents a group selected from the group consisting of —CR
3
═CR
4
—, —C≡C—, —SiR
5
R
6
—, —NR
7
—, —CO—, —CO—O—, —O—CO— and —SO
2
—. Ar
2
has at least one substituent selected from the group consisting of alkyl groups of 5 to 20 carbon atoms, alkoxy groups of 5 to 20 carbon atoms, alkylthio groups of 5 to 20 carbon atoms, alkylsilyl groups of 5 to 60 carbon atoms, alkylamino groups of 5 to 40 carbon atoms, aryl groups of 6 to 60 carbon atoms, aryloxy groups of 6 to 60 carbon atoms, arylalkyl groups of 7 to 60 carbon atoms, arylalkoxy groups of 7 to 60 carbon atoms, arylalkenyl groups of 8 to 60 carbon atoms, arylalkynyl groups of 8 to 60 carbon atoms, arylamino groups of 6 to 60 carbon atoms, heterocyclic compound groups of 4 to 60 carbon atoms and a cyano group. Ar
2
may also have other substituent than these substituents. When Ar
2
have a plurality of substituents, they may be the same or different. m is an integer from 1 to 4. Ar
1
may also have other substituent than substituents represented by —X
1
—Ar
2
. When Ar
1
have a plurality of substituents, they may be the same or different. R
1
to R
7
each independently represents a group selected from the group consisting of a hydrogen atom, alkyl groups of 1 to 20 carbon atoms, aryl groups of 6 to 60 carbon atoms, heterocyclic compound groups of 4 to 60 carbon atoms and a cyano group. When the substituent of Ar
2
, or R
1
to R
7
include an alkyl chain, the alkyl chain may be any of linear, branched and cyclic, alternatively, and ends of a plurality of alkyl groups may bond to form a ring. One or more —CH
2
— groups contained in this alkyl chain may also be replaced with a group selected from the group consisting of —O—, —S—, —CR
8
═CR
9
—, —C≡C—, —SiR
10
R
11
—, —NR
12
—, —CO—, —CO—O—, —O—CO— and —SO
2
—. When the substituent of Ar
2
, or R
1
to R
7
include an aryl group or a heterocyclic compound group, they may also further have a substituent. Herein, R
8
to R
12
each independently represents a group selected from the group consisting of a hydrogen atom, alkyl groups of 1 to 20 carbon atoms, aryl groups of 6 to 60 carbon atoms, heterocyclic compound groups of 4 to 60 carbon atoms and a cyano group. One or more hydrogen atoms contained in the repeating unit of the formula (1) may also be replaced with halogen atoms selected from the group consisting of F, Cl and Br. And, n is 0 or 1.).
Further, the present invention relates to
[2] a polymeric fluorescent substance which emits a fluorescence in a sol
Doi Shuji
Kitano Makoto
Noguchi Takanobu
Yamaguchi Fumi
Sumitomo Chemical Company Limited
Xu Ling
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