Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2002-06-28
2003-10-28
Truong, Duc (Department: 1711)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S691000, C428S917000, C528S086000
Reexamination Certificate
active
06638646
ABSTRACT:
There is a considerable demand in industry for large-area solid-state light sources for a number of applications, predominantly in the area of display elements, display screen technology and illumination technology. The requirements made of these light sources can currently not be met entirely satisfactorily by any of the existing technologies.
As an alternative to conventional display and illumination elements, such as incandescent lamps, gas-discharge lamps and non-self-illuminating liquid-crystal display elements, electroluminescent (EL) materials and devices, such as light-emitting diodes (LEDs), have already been in use for some time.
Besides inorganic electroluminescent materials and devices, low-molecular-weight, organic electroluminescent materials and devices have also been known for about 30 years (see, for example, U.S. Pat. No. 3,172,862). Until recently, however, the practical utility of such devices was greatly restricted.
EP 423 283 and EP 443 861 describe electroluminescent devices which contain a film of a conjugated polymer as light-emitting layer (semiconductor layer). Such devices have numerous advantages, such as the possibility of producing large-area, flexible displays simply and inexpensively. In contrast to liquid-crystal displays, electroluminescent displays are self-illuminating and therefore do not require an additional back-lighting source.
A typical device in accordance with EP 423 283 consists of a light-emitting layer in the form of a thin, dense polymer film (semiconductor layer) which contains at least one conjugated polymer. A first contact layer is in contact with a first surface, and a second contact layer is in contact with a further surface of the semiconductor layer. The polymer film of the semiconductor layer has a sufficiently low concentration of extrinsic charge carriers so that, on application of an electric field between the two contact layers, charge carriers are introduced into the semiconductor layer, where one contact layer becomes positive compared with the other, and the semiconductor layer emits radiation. The polymers used in devices of this type are referred to as conjugated. The term “conjugated polymer” is taken to mean a polymer which has a delocalized electron system along the main chain. The delocalized electron system gives the polymer semiconductor properties and enables it to transport positive and/or negative charge carriers with high mobility.
EP 423 283 and EP 443 861 describe, as polymeric material for the light-emitting layer, poly(p-phenylenevinylene), which may be modified on the aromatic ring by alkyl, alkoxy, halogen or nitro substituents in order to improve the properties. Polymers of this type have since then been investigated in a large number of studies, and bisalkoxy-substituted PPVs in particular have already been optimized a very long way toward applicational maturity (cf., for example, J. Salbeck, Ber. Bunsenges. Phys. Chem. 1996, 100, 1667).
The German patent application 196 52 261.7 with the title “Aryl-substituted poly(p-arylenevinylenes), process for their preparation, and their use in electroluminescent components”, which was not published before the priority date of the present application, proposes aryl-substituted poly(p-arylenevinylenes) which are also suitable for generating green electroluminescence.
However, the development of polymers of this type can in no way be regarded as complete, and there continues to be plenty of room for improvement. Thus, inter alia, improvements are still possible with respect to the service life and stability, in particular at elevated temperatures.
The object of the present invention was therefore to provide electroluminescent materials which, when used in illumination or display devices, are suitable for improving the property profile of these devices.
Surprisingly, it has now been found that poly(arylphenylenevinylenes) whose phenylene unit carries a further substituent in the para- or meta-position to the aryl radical are particularly suitable as electroluminescent materials.
The invention therefore relates to poly(arylenevinylenes) comprising at least 20% of recurring units of the formula (I),
where the symbols and indices have the following meanings:
Aryl: is an aryl group having 4 to 14 carbon atoms;
R′: is a substituent which is either in the labeled phenylene position 5 or 6 and is CN, F, Cl, N(R
1
R
2
) or a straight-chain, branched or cyclic alkyl, alkoxy or thioalkoxy group having 1 to 20 carbon atoms, in which, in addition, one or more H atoms may be replaced by F;
R″: are identical or different and are CN, F, Cl or a straight-chain, branched or cyclic alkyl or alkoxy group having 1 to 20 carbon atoms, where one or more non-adjacent CH
2
groups may be replaced by —O—, —S—, —CO—, —COO—, —O—CO—, —NR
1
—, —(NR
2
R
3
)
+
-A
−
or —CONR
4
—, and where one or more H atoms may be replaced by F, or an aryl group having 4 to 14 carbon atoms, which may be substituted by one or more non-aromatic radicals R′;
R
1
, R
2
, R
3
, R
4
are identical or different and are H or an aliphatic or aromatic hydrocarbon radical having 1 to 20 carbon atoms;
A
−
: is a singly charged anion or an equivalent thereof; and
n: is 0, 1, 2, 3, 4 or 5.
The polymers according to the invention are highly suitable for use as electroluminescent materials. They have, for example, the advantage of having constant brightness in long-term operation, even at elevated temperatures (for example heating for a number of hours at 85° C.).
It is thus not necessary to adjust the voltage during long-term operation in order to obtain an initial brightness. This advantage is particularly evident in the case of battery operation, since the maximum voltage economically possible is greatly restricted here.
Devices containing the polymers according to the invention also have a long service life.
Surprisingly, the polymers according to the invention have a particularly low content of defect structures.
The polymers generally contain from 10 to 10,000, preferably from 10 to 5000, particularly preferably from 100 to 500, very particularly preferably from 250 to 2000, recurring units.
Polymers according to the invention comprise at least 20%, preferably at least 30%, particularly preferably at least 40%, of recurring units of the formula (I).
Furthermore, preference is also given to copolymers consisting of recurring units of the formula (I) and recurring units containing a 2,5-dialkoxy-1,4-phenylenevinylene structure. Preference is likewise given to copolymers consisting of recurring units of the formula (I) and recurring units containing a 2-aryl-1,4-arylenevinylene structure which is not further substituted.
Preference is furthermore given to copolymers comprising 1, 2 or 3 different recurring units of the formula (I).
For the purposes of the present invention, the term “copolymers” covers random, alternating, regular and block-like structures.
Preference is also given to polymers comprising recurring units of the formula (I) in which the symbols and indices have the following meanings:
Aryl is phenyl, 1- or 2-naphthyl, 1-, 2- or 9-anthracenyl, 2-, 3- or 4-pyridinyl, 2-, 4- or 5-pyrimidinyl, 2-pyrazinyl, 3- or 4-pyridazinyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-quinolinyl, 2- or 3-thiophenyl, 2- or 3-pyrrolyl, 2- or 3-furanyl or 2-(1,3,4-oxadiazol)yl;
R′ are identical or different and are CN, F, Cl, CF
3
or a straight-chain or branched alkoxy group having 1 to 12 carbon atoms;
R″ are identical or different and are a straight-chain or branched alkyl or alkoxy group having 1 to 12 carbon atoms; and
n is 0, 1, 2 or 3, particularly preferably 0, 1 or 2.
Particular preference is given to polymers in which the aryl substituent in the formula (I) has the following meaning: phenyl, 1-naphthyl, 2-naphthyl or 9-anthracenyl.
Particular preference is furthermore given to polymers in which the aryl substituent in the formula (I) has the following substitution pattern: 2-, 3- or 4-alkyl(oxy)phenyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-dialkyl(oxy)phenyl, 2,3,4-, 2,3,5-, 2,3,6
Becker Heinrich
Kreuder Willi
Schenk Hermann
Spreitzer Hubert
Yu Nu
Connolly Bove & Lodge & Hutz LLP
Semiconductors GmbH
Truong Duc
LandOfFree
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