Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1999-06-08
2002-05-28
Truong, Duc (Department: 1711)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000
Reexamination Certificate
active
06395410
ABSTRACT:
An electroluminescent (EL) device is characterized in that it emits light when an electrical voltage is applied and current flows. Such devices have long been known in engineering as “light-emitting diodes” (LEDs). The emission of light is due to the fact that positive charges (“holes”) and negative charges (“electrons”) recombine with the emission of light.
In the development of light-emitting components for electronics or photonics, use is mainly made at present of inorganic semiconductors, such as gallium arsenide. Punctiform indicating elements can be produced on the basis of such substances. Large-area devices are not possible.
In addition to semiconductor light-emitting diodes, electroluminescent devices based on vapour-deposited low-molecular-weight organic compounds are known U.S. Pat. No. 4,539,507, U.S. Pat. No. 4,769,262, U.S. Pat. No. 5,077,142, EP-A 406 762, EP-A 278 758, EP-A 278 757).
Furthermore, polymers, such as poly(p-phenylenes) and poly(p-phenylenevinylenes) (PPV) are described as electroluminescent polymers: G. Leising et al., Adv. Mater. 4 (1992) No. 1; Friend et al., J Chem. Soc., Chem. Commun. 32 (1992); Saito et al., Polymer, 1990, Vol. 31, 1137; Friend et al., Physical Review B, Vol. 42, No. 18, 11670 or WO 90/13148. Further examples of PPV in electroluminescent indicators are described in EP-A 443 861, WO-A-9203490 and 92003491.
EP-A 0 294 061 discloses an optical modulator based on polyacetylene.
Heeger et al. have proposed soluble, conjugated PPV derivatives for producing flexible polymeric LEDs (WO 92/16023). Polymer blends of various compositions are likewise known: M. Stolka et al., Pure & Appl. Chem., Vol. 67, No. 1, pp 175-182, 1995; H. Bässler et al., Adv. Mater. 1995, 7, No. 6, 551; K. Nagai et al., Appl. Phys. Lett. 67 (16), 1995, 2281; EP-A 532 798.
As a rule, the organic EL devices contain one or more layers of organic charge transport compounds. The basic structure of the layer sequence is as follows:
1 Carrier, substrate
2 Base electrode
3 Hole-injecting layer
4 Hole-transporting layer
5 Light-emitting layer
6 Electron-transporting layer
7 Electron-injecting layer
8 Top electrode
9 Contacts
10 Packaging, encapsulation.
The layers 3 to 7 are the electroluminescent element.
This structure is the most general case and can be simplified by omitting individual layers so that one layer assumes a plurality of tasks. In the simplest case, an EL device comprises two electrodes between which an organic layer is situated which fulfils all the functions, including the emission of light. Such systems are described, for example, in Application WO 90/13148 on the basis of poly(p-phenylenevinylene).
Multilayer systems can be constructed by vapour-deposition processes in which the layers are applied successively from the gas phase or by pouring methods. Because of the higher processing speed, pouring methods are preferred. However, in certain cases, the process of partially dissolving a layer already applied may present a difficulty in depositing the next layer on top.
The object of the present invention is to provide electroluminescent devices having high luminous density, the mixture to be applied being pourable, i.e. capable of being applied from solution.
It was found that electroluminescent devices containing material A or a blend of material A with polymeric binder B, mentioned below fulfil these requirements. In the following, the term zone is also to be equated with layer.
The present invention therefore relates to electroluminescent devices containing, as electroluminescent material A, at least one oligomer of substituted p-divinylbenzene having the general formula (I)
in which
R
1
and R
2
independently represent hydrogen, or linear alkyl or alkoxy containing 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, or branched alkyl or alkoxy containing 3 to 12, preferably 3 to 8 carbon atoms, or cycloalkyl containing 4 to 10, preferably 5 or 6 carbon atoms, with the proviso that
R
1
and R
2
may not both by hydrogen,
R
3
and R
4
are identical or different and represent hydrogen, C
1
-C
6
-alkyl (preferably methyl or ethyl), CN or halogen (preferably fluorine, chlorine or bromine),
R
5
, R
6
R
7
and R
8
are identical or different and may be any desired radicals, inter alia, radicals suitable for coupling oligomers to other oligomers/polymers,
n is an integer from 2 to 20, preferably 2 to 15 and particularly preferably 2 to 10,
R
5
and R
7
represent independently of one another, preferably hydrogen or alkyl, in particular C
1
-C
4
-alkyl, very particularly preferably methyl,
R
6
and R
8
represent, independently of one another, preferably alkyl or aryl radical, in particular C
1
-C
6
-alkyl or phenyl. The alkyl and phenyl radicals may contain one or more functional groups, such as, for example, —OH, —CN, —CHO or Br.
With suitable substitution, the oligomers of substituted divinylbenzene may also be incorporated, for example, in polymers as discussed below, by means of functional groups. In this connection, it is possible to produce both main-chain and side-chain polymers containing low-molecular-weight compounds.
The oligomers may be coupled to polymers containing double bonds, for example unsaturated polymers, such as polybutadiene and polyoctamer by metathetic incorporation (cross-metathesis reaction of the oligomers and an unsaturated polymer).
The electroluminescent device is made up of an anode, an electroluminescent element and a cathode, at least one of the two electrodes being transparent or semi transparent in the visible spectral range. The electroluminescent element contains:
A hole-injecting zone, a hole-transporting zone, an electroluminescent zone, an electron-transporting zone and/or an electron-injecting zone, characterized in that the electroluminescent element optionally contains a functionalized compound from the group comprising the hole-transporting materials, a luminescent material A and, optionally, electron-transporting materials, at least one zone being present, individual zones being omitted and the joined zone(s) taking over a multiplicity of tasks.
A zone can take over a multiplicity of tasks, i.e., a zone may contain, for example, hole-injecting, hole-transporting, electroluminescent, electron-injecting and/or electron-transporting substances.
The electroluminescent element may furthermore contain one or more transparent polymeric binders B.
An additional embodiment of the invention relates to the device comprising the product of reaction of the oligomer of formula (I) and a polymeric resin containing double bonds, for example unsaturated polymers, such as polybutadiene or polyoctamer.
The oligomers of substituted p-divinylbenzene may be produced by known methods, for example by metathesis reactions, which are described in Macromol. Rapid Commun., 16 (1995), 149 (cf. also Examples).
The products are soluble in common solvents. They can be processed to form transparent films which, depending on the value of n and/or the choice of substituents on the phenyl ring, exhibit different photoluminescents. By varying n and/or the choice of the substituents, the wavelength (color) of the emitted light can therefore be systematically adjusted.
The binder B represents polymers and/or copolymers, such as, for example, polycarbonates, polyester carbonates, copolymers of styrenes, such as SAN or styrene acrylates, polysulfones, polymers based on vinyl-group-containing monomers, such as, for example, poly(meth)acrylates, polyvinylpyrrolidone, polyvinylcarbazole, vinyl-acetate and vinyl-alcohol polymers and copolymers, polyolefins, cyclic olefin copolymers, phenoxy resins, etc. Mixtures of different polymers can also be used. The polymeric binders B have molecular weights of from 10,000 to 200,000 g/mol., are soluble and film-forming and are transparent in the visible spectral range. They are described, for example, in Encyclopedia of Polymer Science and Engineering, 2nd ed., A. Wiley-Interscience Publication. The electroluminescent material A may be dispersed in the transparent binders B. The concentration ratios are vari
Elschner Andreas
Thorn-Csanyi Emma
Wehrmann Rolf
Bayer Aktiengesellschaft
Gil Joseph C.
Preis Aron
Truong Duc
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