Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Patent
1992-03-09
1993-12-28
Stoll, Robert L.
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
25229967, 25229901, 2522996, 359103, C09K 1912, C09K 1920, C09K 1952, G02F 113
Patent
active
052736806
DESCRIPTION:
BRIEF SUMMARY
This invention relates to laterally fluorinated oligophenyls and their use in liquid crystal materials.
Liquid crystal materials are well known, and generally exploit the electro-optical switching properties of the nematic (N) or smectic, especially chiral smectic C (S.sub.C *) or smectic I (S.sub.I *), phases the asterisk denoted a chiral phase. They are used widely in electrooptical display devices.
Such materials are generally mixtures of compounds selected so that the mixture shows desirable properties. In particular such properties include:
(i) a broad temperature range over which a suitable liquid crystal phase, e.g. S.sub.A, S.sub.C, S.sub.C *, S.sub.I S*.sub.I * or N persists, this range preferably including room temperature (ca. 20.degree. C.)
(ii) low viscosity
(iii) ease of manufacture
(iv) good electro-optical response
(v) In the case of compounds or mixtures which show an S.sub.C phase, miscibility with one or more optically active compounds, i.e. which contain an asymmetrically substituted carbon atom, to form a helical chiral phase having a long pitch and a high spontaneous polarisation coefficient P.sub.S. It is also useful if the compound or mixture shows an S.sub.A phase at a higher temperature than its S.sub.C phase to assist in aligning the S.sub.C phase with the electrodes of a liquid crystal electrooptical device.
Fluorinated terphenyls are known for use in liquid crystal materials. For example:
EP-A-8430494.3 describes the preparation and use of monofluorinated terphenyls of general formula: ##STR1## where R.sub.1 and R.sub.2 are independently alkyl or alkoxy, in nematic liquid crystal materials. GB-A-8725928 and WO/07890 disclose the use of these monofluorinated terphenyls in S.sub.C * mixtures.
EP-A-0084194 contains a wholly speculative references to laterally difluorinated terphenyls, including a theoretical reference to the compound: ##STR2## for use in nematic mixture. PCT/EP87/00515 which at the date of this patent application was unpublished, contains a speculative general formula which would include difluorophenyls, and also refers specifically to the two compounds: ##STR3## used exclusively in nematic liquid crystal mixtures.
This invention seeks to identify other useful difluorinated terphenyls, and in particular to investigate their use in smectic liquid crystal materials.
According to the invention fluorinated derivatives of bi-, p-ter- or p-quaterphenyl are provided of the formula I ##STR4## in which a is 0 or 1, and in which the terminal substituents
R.sup.1, R.sup.2 and R.sub.3 are each independently an alkyl or alkenyl residue each with up to 15 C atoms, optionally substituted by CN or by at least one halogen atom, and wherein one or more non-adjacent CH.sub.2 groups of these residues may be replaced by --O--, --S--, --CO--, --O--CO--, --CO--O--, --O--CO--O-- or --C.tbd.C--, one of the residues R.sub.1 and R.sub.2 may also denote a group of the formula, ##STR5## any one of the following pairs of lateral substituents are both fluorine: (A, B), (C, D), (D, E), (C, E), (B, C), (D, J), (D, K), (A, C), (C, J), (C', D'), (D', E), (D', A), (C', E), (C', A), (D', J'), (D', K'), (C', J'), (B, G), (A, G),
all of the other lateral substituents being hydrogen or fluorine.
The structural preferences discussed below are inter alia on the basis of usefulness in liquid crystal mixtures, and/or ease of preparation.
Preferred overall structures for difluorinated terphenyls of formula I are those of the part formulae I, 1 to I, 6 ##STR6##
Preferred overall structures for trifluorinated terphenyls of formula I are those of part formulae I,7 to I,12: ##STR7##
Compositions exhibiting smectic C phases which contain compounds of the formula I wherein a is 0 are particularly preferred. Preferred overall structures of difluorinated biphenyls of formula I (a=0) are those of part formulae I,13 to I,19: ##STR8##
For the sake of simplicity in the following Phe denotes a 1,4-phenylen group, PheF a group of the formula ##STR9## and PheF.sub.2 a group of the formula ##STR10##
The compounds of the for
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Finkenzeller Ulrich
Geelhaar Thomas
Gray George W.
Hird Michael
Krause Joachim
Harris C.
Merck Patent Gesellschaft mit beschrankter Haftung
Stoll Robert L.
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