Compositions – Liquid crystal compositions
Reexamination Certificate
2002-07-24
2004-11-30
Huff, Mark F. (Department: 1756)
Compositions
Liquid crystal compositions
C349S183000, C568S074000, C568S077000, C568S775000
Reexamination Certificate
active
06824706
ABSTRACT:
FIELD OF INVENTION
The invention relates to new mono-, oligo- and poly-difluorovinyl-(hetero)arylenes, polymerisable liquid crystal materials and anisotropic polymer films, including their oxidatively or reductively doped forms. The invention further relates to methods of their preparation, their use as semiconductors or charge transport materials in optical, electrooptical or electronic devices including field effect transistors, electroluminescent, photovoltaic and sensor devices. The invention further relates to field effect transistors and semiconducting components comprising the new mono-, oligo- and poly-difluorovinyl-(hetero)arylenes. Furthermore the invention relates to a security marking or device and to a charge injection layer, planarising layer, antistatic film or conducting substrate or pattern. The invention also relates to their synthesis and to a key intermediate compound.
BACKGROUND AND PRIOR ART
Organic materials have recently shown promise as the active layer in organic based thin film transistors and organic field effect transistors (OFETs) [see reference 1]. Such devices have potential applications in smart cards, security tags and the switching element in flat panel displays. Organic materials are envisaged to have substantial cost advantages over their silicon analogues if they can be deposited from solution, as this enables a fast, large-area fabrication route.
The performance of the device is principally based upon the charge carrier mobility of the semiconducting material and the current on/off ratio, so the ideal semiconductor should have a low conductivity in the off state, combined with a high charge carrier mobility (>1×10
−3
cm
2
V
−1
s
−1
). In addition, it is important that the semiconducting material is relatively stable to oxidation, i.e., it has a high ionisation potential, as oxidation leads to reduced device performance. A known compound which has been shown to be an effective p-type semiconductor for OFETs is pentacene [see reference 2]. When deposited as a thin film by vacuum deposition, it was shown to have carrier mobilities in excess of 1 cm
2
V
−1
s
−1
with very high current on/off ratios greater than 10
6
. However, vacuum deposition is an expensive processing technique that is unsuitable for the fabrication of large-area films.
In general, poly(3-alkylthiophenes) show improved solubility and are able to be solution processed to fabricate large area films. The 3-alkyl substituents can be incorporated in a polymer chain with two different orientations: head-to-tail linkage (HT) or head-to-head (HH). A high regioregularity leads to improved packing and optimised microstructure, leading to improved charge carrier mobility [see reference 3, 4, 5]. However, poly(3-alkylthiophenes) have relatively low ionisation potentials and are susceptible to doping in air [see reference 6].
Regioregular poly(3-hexylthiophene) has been reported with charge carrier mobility between 1×10
−5
and 4.5×10
−2
cm
2
V
−1
s
−1
, but with a rather low current on/off ratio (10-10
3
) [see reference 7].
Fluorinated poly(alkylthiophenes) were studied by L. Robitaille and M. Leclerc [see reference 8]. Poly[3-(tridecafluorononyl)thiophene] was found to be soluble in octafluorotoluene. Compared to its alkyl analogues, however, it exhibited inferior electronic properties, which was attributed to lower regioregularity.
Poly(p-phenylene vinylene)s (PPV) were studied by S. Doi et al. [see reference 9] and observed to be efficient as light emitting and hole transport materials. Furthermore poly(thienyl vinylene) (PTV) was described as a conducting layer between an ITO layer and the hole transport material.
Poly(2,5-thienylene vinylene) (PTV) was characterized as a semiconductor in thin-film transistors (TFT) [see reference 10]. The polymer itself is insoluble, infusible and therefore was processed via a soluble precursor, followed by heat treatment. Because of a low ionization potential, p doping with oxygen of the air resulted automatically. But degradation of the polymer, especially thin films, by oxidation reduces the performance of the device [see reference 11]. It was found that the carrier mobility largely depends on the &pgr;-conjugation length of PTV and is comparable to that of &agr;-Si TFT.
The manufacture of a field effect transistor (FET) in which a &pgr;-conjugated polymer film serves as a semiconductor layer is described in the U.S. Pat. No. 5,892,244 [reference 12]. A polymer precursor film is formed which is soluble in a solvent. Then the precursor film is changed to the &pgr;-conjugated polymer film. The polymer is represented by one of the two general formulae:
wherein R is H, alkyl or alkoxy.
Compounds and polymers, including their with anions doped forms, having the formula:
as a recurring unit wherein R
1
, R
2
, R
3
and R
4
are electron donating substituents or hydrogen and R
5
is an electron withdrawing substituent, are disclosed in WO 96/21659 [reference 13]. For the synthesis a chemical and a electrochemical polymerisation is described. Their electrical conductivity and their use in electronic and opto-electronic devices, such as light emitting diodes (LEDs) is mentioned.
Poly(3-dodecylthienylene vinylene)s (PDDTV) were synthesized and the effect of structural regularity was studied by R. D. McCullough and R. S. Loewe [see reference 11]. Preparation by Heck polymerization led to regioirregular PDDTV and by Stille polymerization to at least 90% regioregular, head-to-tail coupled, PDDTV.
The synthesis of poly(2,5-thienylene-F-polyene)s has been described by A. B. Shtrarev and Z. Chvatal [see reference 14]. Reacting 2,5-dilithio- or 2,5-bis(bromomagnesio)thiophenes with F-1,3-butadiene and F-ethylene gave oligomers having the units:
respectively, wherein R is H or CH
3
.
The 2,5-thienylene-F-ethenylene showed the lowest solubility in ether compared to the corresponding F-butadienylenes. The disubstituted product (E,E)-2,5-bis[2-(2-thienyl)-1,2-difluoroethenyl]-thiophene exhibited a reversible nematic phase.
GB 2303633 relates to a conjugated polymer or oligomer which comprises arylene vinylene units having an aromatic ring or an E-configured vinylidene linking group which bears an electron-withdrawing substituent comprising fluorine or perfluoroalkyl. The preferred trifluoromethyl group, to which the examples refer, is described to stabilize the oligomer and polymer to degradation under illumination and to suppress oxidation, owing to its large steric bulk.
As a result, an improvement of the efficiency of LEDs by incorporating these materials as an emissive or electron-transport layer is claimed.
It is an aim of the present invention to provide new materials for use as semiconductors or charge transport materials, which are easy to synthesize, have high charge mobility, good processibility and improved oxidative stability.
A further aim of the present invention is to provide a synthesis route for the oligo- and polymers according to the invention, resulting in a high regioregularity, and to describe the intermediate compounds. Still another aim of the present invention is novel intermediates and process steps described hereinafter.
Further aims of the present inventions relate to advantageous uses of the mono-, oligo- and polymers, including their oxidatively or reductively doped forms, according to the invention.
Other aims of the invention are immediately evident to those skilled in the art from the following description.
The inventors have found that these aims can be achieved by providing new monomers, oligomers and polymers based on difluorovinyl-(hetero)arylenes.
The incorporation of the two electronegative fluorine substituents on the vinylidene linker increases the electron affinity of the conjugated system. The mono-, oligo- and polymers according to the invention generally show an increased oxidation pote
Farrand Louise
Giles Mark
Heeney Martin
McCulloch Iain
Shkunov Maxim
Huff Mark F.
Merck Patent Gesellschaft mit beschrank Haftung
Millen White Zelano & Branigan P.C.
Sadula Jennifer R
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