Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From boron-containing reactant
Reexamination Certificate
2001-04-26
2003-11-25
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From boron-containing reactant
C528S008000, C528S397000, C528S488000, C252S301160, C252S301350
Reexamination Certificate
active
06653438
ABSTRACT:
There is considerable industrial demand 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 cannot at present be completely satisfied 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, such devices were greatly limited in their practical applicability.
WO 90/13148 and EP-A-0 443 861 describe electroluminescent devices which contain a film of a conjugated polymer as light-emitting layer (semiconductor layer). Such devices offer numerous advantages, such as the possibility of manufacturing 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 illumination source at the back.
A typical device in accordance with WO 90/13148 consists of a light-emitting layer in the form of a thin, dense polymer film (semiconductor layer) containing 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, the first contact layer becoming positive compared with the other layer, and the semiconductor layer emits radiation. The polymers used in such devices are 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.
For use in EL elements as described in WO 90/13148, very many different polymers have already been proposed. Derivatives of poly(p-phenylenevinylene) (PPV) appear particularly suitable. Such polymers are described, for example, in WO 98/27136. These polymers are particularly suitable for electroluminescence in the green to red spectral region. In the blue to blue-green spectral region, the polymers proposed hitherto are principally those based on poly-p-phenylene (PPP) or polyfluorene (PF). Corresponding polymers are described, for example, in EP-A-0 707 020, WO 97/05184 and WO 97/33323. These polymers already exhibit good EL properties, although development is still not complete by far. Thus, polymers in the blue to blue-green spectral region frequently also exhibit the phenomenon of morphological instability. For example, many polyfluorenes exhibit liquid-crystalline or related behavior, which can result, in thin films, in domain formation, which is in turn unsuitable for the production of a homogeneously luminous area. These polymers also tend to form aggregates, which shifts the electroluminescence into the long-wave region in an undesired manner, and adversely affects the life of the EL elements.
The object of the present invention was therefore to provide polymers which are suitable for emission in the blue and blue-green spectral region and at the same time have improved morphological behavior.
Surprisingly, it is now been found that selection of specific substitution patterns in otherwise typical polymers principally built up from 2,7-fluorenyl units significantly improves the morphological properties without losing the very good applicational properties (emission color, quantum yield of the emission, suitability for EL applications).
The polymers according to the invention contain fluorene units whose substitution pattern makes them suitable for suppressing aggregation in the film. This is achieved in particular by the 9,9-position being substituted by two different types of aromatic radical. This result is surprising, principally in view of indications in the scientific literature (G. Klärner et al., Adv. Mater. 1998, 10, 993), according to which incorporation of diphenylfluorene units in the main chain does not give such effects. However, this also means precisely that it has proven particularly favorable to introduce two different aromatic substituents in this position.
The invention relates to conjugated polymers which contain structural units of the formula (I)
in which
R
1
and R
2
are two different substituents from the group consisting of C
2
-C
40
-heteroaryl and C
5
-C
40
-aryl, where the abovementioned aryl and/or heteroaryl radicals can be substituted by one or more substituents R
3
; for the purposes of this invention, the aryl and/or heteroaryl radicals must be of different types even if they differ through the nature or position of substituents,
R
3
and R
4
are identical or different and are C
1
-C
22
-alkyl, C
2
-C
20
-heteroaryl, C
5
-C
20
-aryl, F, Cl, CN, SO
3
R
5
or NR
5
R
6
, where the alkyl radicals can be branched or unbranched or alternatively can be cycloalkyl radicals, and individual, non-adjacent CH
2
groups of the alkyl radical can be replaced by O, S, C═O, COO, N—R
5
or simple aryl radicals, where the abovementioned aryl radicals can be substituted by one or more non-aromatic substituents R
3
,
R
5
and R
6
are identical or different and are H, C
1
-C
22
-alkyl, C
2
-C
20
-heteroaryl or C
5
-C
20
-aryl, where the alkyl radicals can be branched or unbranched or alternatively can be cycloalkyl radicals, and individual, non-adjacent CH
2
groups of the alkyl radical can be replaced by O, S, C═O, COO, N—R
5
or simple aryl radicals, where the abovementioned aryl radicals can be substituted by one or more non-aromatic substituents R
3
, and
m and n are each an integer 0, 1, 2 or 3, preferably 0 or 1.
R
1
and R
2
are preferably two different substituents from the group consisting of C
5
-C
40
-aryl and C
2
-C
40
-heteroaryl, where the above-mentioned aryl and heteroaryl radicals can be substituted by one or more substituents R
3
.
The polymer according to invention contains at least 10 mol %, preferably from 10 mol % to 100 mol %, of structural units of the formula (I) incorporated randomly, alternately, periodically or in blocks.
The polymers according to the invention are preferably copolymers consisting of one or more structural units of the formula (I). In a further embodiment of the present invention, the polymer according to the invention may also contain different structural units of the formula (I) and further structural units which are not per se according to the invention. Examples of such further monomers are 1,4-phenylenes, 4,4′-biphenyls and further 2,7-fluorenes, which, if desired, can also carry substituents, preferably branched or unbranched C
1
-C
22
-alkyl or -alkoxy groups.
The polymers according to the invention generally have from 10 to 10000, preferably from 10 to 5000, particularly preferably from 50 to 5000, very particularly preferably from 50 to 1000, recurring units.
Particular preference is given to polymers in which m and n are zero.
The polymers according to invention can be built up by a wide variety of reactions. However, preference is given to uniform C—C coupling reactions, for example the Suzuki condensation and the Stille condensation. In this context, the term “uniform C—C coupling reaction” is taken to mean that the linking to the polymer is determined by the position of the reactive groups in the corresponding monomers. This is given particularly well by the abovementioned reacti
Kreuder Willi
Spreitzer Hubert
Zum Heinrich Becker
Connolly Bove & Lodge & Hutz LLP
Covion Organic Semiconductors GmbH
Truong Duc
LandOfFree
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