Electroluminescent assemblies containing boron chelates

Details Electroluminescent assemblies containing boron chelates Electroluminescent assemblies containing boron chelates

1999-06-29

2001-09-11

Kelly, Cynthia H. (Department: 1774)

Stock material or miscellaneous articles

Composite

Of inorganic material

C428S691000, C428S704000, C428S917000, C313S503000, C313S504000, C313S506000, C313S507000, C313S498000

Reexamination Certificate

active

06287713

ABSTRACT:

An electroluminescent (EL) assembly is characterized in that it emits light and an electric current flows when an electric potential is applied. Such assemblies have long been known in industry under the name “light emitting diodes” (LEDs). The emission of light results from recombination of positive charges (holes) and negative charges (electrons) with emission of light.
In the development of light-emitting components for electronics or photoelectronics, use is at present made mainly 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 light emitting semiconductor diodes, electroluminescent assemblies based on vapour-deposited low molecular weight organic compounds are known (U.S. Pat. Nos. 4,539,507, 4,769,262, 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) (PPVs) 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 90/13148. Further examples of PPV in electroluminescent 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. Bässler 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 comprising 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 Covering, encapsulation.
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 assumes a plurality of functions. In the simplest case, the EL assembly comprises two electrodes between which there is located one 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 means of vapour deposition processes 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 of it can in certain cases be a difficulty.
It is an object of the present invention to provide electroluminescent assemblies having a high light flux, in which novel boron complexes or chelates having improved solubility in customary solvents are to be used as emitters and/or electron conductors. These novel boron complexes should also be able to be applied from the gas phase by means of vapour deposition processes.
It has been found that electroluminescent assemblies containing the boron complexes mentioned below meet these requirements. In the following, the term “zone” is equivalent to the term “layer”.
The present invention accordingly provides electroluminescent assemblies 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 contains one or more zones selected from the group consisting of hole injection zone, hole transport zone, electroluminescent zone, electron transport zone and electron injection zone in the order specified, where each of the zones present may also assume functions of the other zones mentioned, characterized in that the electroluminescent element contains a boron complex of 8-hydroxyquinoline derivatives.
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 1 to 5, (C
6
-C
14
)-arylene, and
n represents an integer from 2 to 10,000, preferably from 5 to 5000.
The hole conduction 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 zone or zones located between the hole injection zone and the cathode can also assume a plurality of functions, i.e. one zone can contain, 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)
where
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
)-alkoxycarbonyl-(C
1
-C
6
)-alkyl, for example 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 else phenyl or naphthyl substituted by from one to three methyl, ethyl, n-, iso-propyl, methoxy, ethoxy, n- and/or iso-propoxy radicals.
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; this patent is hereby expressly incorporated by reference into the present description. The tris-nitrophenyl compound can, for example, be converted into the tris-aminophenyl compound by 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.
The following compounds may be mentioned by way of example:
Apart from the tertiary amino compound, further hole conductors, e.g. in the form of a mixture with the tertiary amino compound, may also be used for building up the electroluminescent element. The further hole conductor or conductors can be, on the one hand, one or more compounds of the formula (II), including mixtures of isomers, or, on the other hand, mixtures of hole transport compounds with compounds of tertiary amino compounds having the general formula (II) and having various structures.
A listing of possible hole injection and hole conductor materials is given in EP-A 0 532 798.
In the case of mixtures of the aromatic amines, the compounds can be used in any ratio.
Examples which may be mentioned are:
Materials which have h

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