Electroluminescent systems with polynulcear metal complexes

Details Electroluminescent systems with polynulcear metal complexes Electroluminescent systems with polynulcear metal complexes

2001-02-28

2003-03-18

Kelly, Cynthia H. (Department: 1774)

Stock material or miscellaneous articles

Composite

Of inorganic material

C313S504000, C313S506000, C428S704000, C428S917000

Reexamination Certificate

active

06534200

ABSTRACT:

This application is the National stage Application of PCT/E99/06124, which claims a priority from German Application 183 39 946.4 filed Sep. 2, 1988.
An electroluminescent (EL) assembly is characterized in that it emits light and current flows when an electric potential is applied. Such assemblies have long been known in industry under the name “light emitting diodes”. The emission of light results from positive charges (holes) and negative charges (electrons) recombining with emission of light.
In the development of light-emitting components for electronics or optics, use is at present mainly made of inorganic semiconductors such as gallium arsenide. Dot-shaped display elements can be produced on the basis of such substances. Large-area assemblies are not possible.
Apart from the semiconductor light emitting diodes, electroluminescent assemblies 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 0 406 762, EP-A 0 278 758, EP-A 0 278 757).
Furthermore, polymers such as poly-(p-phenylenes) and poly-(p-phenylene-vinylenes) (PPV)) have been 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-A 90/13148. Further examples of PPVs in electroluminescence displays are described in EP-A 0 443 861, WO-A 92/03490 and 92/03491.
EP-A 0 294 061 discloses an optical modulator based on polyacetylene.
To produce flexible polymer LEDs, Heeger et al. have proposed soluble conjugated PPV derivatives (WO-A 92/16023).
Polymer blends of different compositions are likewise known: M. Stolka et al., Pure & Appt. Chem., Vol. 67, No. 1, pp 175-182, 1995; H. Bassler et al., Adv. Mater. 1995, 7, No. 6, 551; K. Nagai et al., Appl. Phys. Lett. 67 (16), 1995, 2281; EP-A 0 532 798.
The organic EL assemblies generally contain one or more layers of organic charge transport compounds. The in-principle structure in the order of the layers is as follows:
1 support, substrate
2 base electrode
3 hole injection layer
4 hole transport layer
5 light-emitting layer
6 electron transport layer
7 electron injection layer
8 top electrode
9 contacts
10 sheathing, encapsulation.
The layers 3 to 7 represent the electroluminescent element.
This structure represents the most general case and can be simplified by leaving out individual layers so that one layer takes on a plurality of functions. In the simplest case, an EL assembly consists of two electrodes between which there is located an organic layer which fulfils all functions including the emission of light. Such systems are described, for example, in the Application WO-A 90/13148 on the basis of poly-(p-phenylene-vinylene).
Multilayer systems can be built up by vapour deposition methods in which the layers are applied successively from the gas phase or by means of casting processes. Owing to the higher process speeds, casting processes are preferred. However, partial dissolution of a layer which has already been applied when the next layer is applied on top can present a difficulty in certain cases.
It is an object of the present invention to provide electroluminescent assemblies having a high light flux in which novel metal complexes having improved solubility in customary solvents are used as emitters and/or electron conductors. These novel metal complexes should also be able to be applied by vapour deposition from the gas phase.
It has been found that electroluminescent assemblies containing the metal complexes specified below meet these requirements. In the following, the term zone is equivalent to the term layer.
DESCRIPTION
The present invention accordingly provides an electroluminescent assembly comprising a substrate, an anode, an electroluminescent element and a cathode, where at least one of the two electrodes is transparent in the visible spectral region and the electroluminescent element comprises one or more zones selected from the group consisting of a hole injection zone, a hole transport zone, an electroluminescent zone, an electron transport zone and an electron injection zone in the specified order, where each of the zones present may also assume functions of the other zones mentioned, characterized in that the electroluminescent element contains a multinuclear metal complex.
The hole injection zone preferably contains an uncharged or cationic polythiophene of the formula (I)
where
Q
1
and Q
2
represent, independently of one another, hydrogen, substituted or unsubstituted (C
1
-C
20
)-alkyl, CH
2
OH or (C
6
-C
14
)-aryl or
Q
1
and Q
2
together represent —(CH
2
)
m
—CH
2
— where m=0 to 12, preferably from 1 to 5, or (C
6
-C
14
)-arylene, and
n represents an integer from 2 to 10,000, preferably from 5 to 5000.
The hole conductor zone adjoining the hole injection zone preferably contains one or more aromatic tertiary amino compounds, preferably substituted or unsubstituted triphenylamine compounds, particularly preferably 1,3,5-tris(aminophenyl)benzene compounds of the formula (II).
The zones or zone located between the hole injection zone and the cathode can also assume a plurality of functions, i.e. one zone can comprise, for example, hole-injecting, hole-transporting, electroluminescent, electron-transporting and/or electron-injecting substances.
The electroluminescent element can additionally contain one or more transparent polymeric binders.
The substituted or unsubstituted 1,3,5-tris(aminophenyl)benzene compound preferably represents an aromatic tertiary amino compound of the general formula (II)
in which
R
2
represents hydrogen, substituted or unsubstituted alkyl or halogen,
R
3
and R
4
represent, independently of one another, substituted or unsubstituted (C
1
-C
10
)-alkyl, alkoxycarbonyl-substituted (C
1
-C
10
)-alkyl or substituted or unsubstituted aryl, aralkyl or cycloalkyl.
R
3
and R
4
preferably represent, independently of one another, (C
1
-C
6
)-alkyl, in particular methyl, ethyl, n- or iso-propyl, n-, iso-, sec or tert-butyl, (C
1
-C
4
)-alkoxcarbonyl-(C
1
-C
6
)-alkyl such as methoxycarbonyl-, ethoxycarbonyl-, propoxycarbonyl- or butoxycarbonyl-(C
1
-C
4
)-alkyl, or unsubstituted or (C
1
-C
4
)-alkyl- and/or (C
1
-C
4
)-alkoxy-substituted phenyl-(C
1
-C
4
)-alkyl, naphthyl-(C
1
-C
4
)-alkyl, cyclopentyl, cyclohexyl, phenyl or naphthyl.
Particularly preferably, R
3
and R
4
represent, independently of one another, unsubstituted phenyl or naphthyl or phenyl or naphthyl substituted in each case by from 1 to 3 methyl, ethyl, n-, iso-propyl, methoxy, ethoxy, n- and/or iso-propoxy groups.
R
2
preferably represents hydrogen, (C
1
-C
6
)-alkyl, for example methyl, ethyl, n- or iso-propyl, n-, iso-, sec- or tert-butyl, or chlorine.
Such compounds and their preparation are described in U.S. Pat. No. 4,923,774 for use in electrophotography, which patent is hereby expressly incorporated by reference into the present description. The tris-nitrophenyl compound can be converted into the tris-aminophenyl compound by, for example, generally known catalytic hydrogenation, for example in the presence of Raney nickel ((Houben-Weyl 4/1C, 14-102, Ullmann (4) 13, 135-148). The amino compound is reacted with substituted halogenobenzenes in a generally known manner.
As examples, mention may be made of the following compounds:
Apart from the tertiary amino compound, it is possible, if desired, to use further hole conductors, for example in the form of a mixture with the tertiary amino compound, for building up the electroluminescent element. It is possible here to use either one or more compounds of the formula (II), with mixtures of isomers also being included, or else mixtures of hole transport compounds with compounds of tertiary amino compounds having the general formula (II) and different structures.
A listing of possible hole injection materials and hole conductor materials is given in EP-A 0 532 798.
In the case of mixtures of the aromatic

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