Compositions – Liquid crystal compositions
Patent
1993-05-18
1994-11-15
Wu, Shean
Compositions
Liquid crystal compositions
25229961, 25229963, 25229964, 25229966, C09K 1952, C09K 1934, C09K 1930
Patent
active
053645561
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with liquid crystal components having a terminal halovinyl group, liquid crystalline mixtures which contain such compounds and the use of such compounds for electro-optical purposes.
Liquid crystals are used primarily as dielectrics in indicating devices, since the optical properties of such compounds can be influenced by an applied voltage. Electro-optical devices based on liquid crystals are well-known to a person skilled in the art and can be based on various effects. Such devices are, for example, cells having dynamic scattering, DAP cells (deformation of aligned phases), guest/host cells, TN cells having a "twisted nematic" structure, STN cells ("super-twisted nematic"), SBE cells ("super-birefringence effect") and OMI cells ("optical mode interference"). The most common indicating devices are based on the Schadt-Helfrich effect and have a twisted nematic structure.
The liquid crystal materials must have a good chemical and thermal stability and a good stability towards electric fields and electromagnetic radiation. Further, at the usual operating temperatures in as broad a range as possible they should have a suitable mesophase or in mixtures should bring about or support a mesophase (for example, a nematic or a cholesteric phase for the aforementioned cells), but nevertheless should have a sufficiently low viscosity-and in the cells should permit short response times, low threshold potentials and a high contrast. Further properties such as the electrical conductivity, the dielectric anisotropy and the optical anisotropy must fulfil different requirements depending on the field of application and type of cell.
Compounds which fulfil these requirements are provided by the present invention.
The invention is concerned with compounds of the general formula ##STR2## wherein R signifies hydrogen, halogen, cyano, isothiocyanato, or alkyl, alkenyl or alkynyl with 1 to 15 carbon atoms, which is unsubstituted or substituted with at least one of halogen, cyano and/or trifluoromethyl and in which one or more non-adjacent --CH.sub.2 -- groups can be replaced by --O--, --S--, --CO--, --COO-- and/or --OOC--; substituted with at least one fluorine and in which one --CH.sub.2 -- group can be replaced by --O--, --S--, --COO-- or --OOC--, or --CH.sub.2 --, --CF.sub.2 --, --CHF-- or a single covalent bond; unsubstituted or substituted with at least one of halogen, cyano and/or methyl and in which, when it is unsubstituted, one or more --CH-- groups can be replaced by nitrogen, or unsubstituted or cyano- or fluoro-substituted trans-1,4-cyclohexylene, or 1,4-cyclohexenylene, trans-1,3-dioxane-2,5-diyl or trans-1,3-dithiane-2,5-diyl; trans-1,4-cyclohexylene, or 1,4-cyclohexenylene, trans-1,3-dioxane-2,5-diyl, trans-1,3-dithiane-2,5-diyl or, when Q is different from a single covalent bond, also 1,4-phenylene, which is unsubstituted or substituted with at least one of halogen, cyano and/or methyl and in which, when it is unsubstituted, one or more --CH-- groups can be replaced by nitrogen; --CH.sub.2 O--, --OCH.sub.2 --, --CH.sub.2 CH.sub.2 --, --COO--, --OOC--, --C.tbd.C--, --(CH.sub.2).sub.4 --, --(CH.sub.2).sub.3 O--, --O(CH.sub.2).sub.3 --, the trans form of --CH.dbd.CH--, --CH.dbd.CHCH.sub.2 O--, --OCH.sub.2 CH.dbd.CH--, --CH.dbd.CH(CH.sub.2).sub.2 -- or --(CH.sub.2).sub.2 CH.dbd.CH--;
The compounds in accordance with the invention are characterized by the presence of a vinylic halogen atom. This gives a comparatively high positive contribution to the dielectric anisotropy. In particular, the ready polarizability of the halovinyl group contributes to a surprisingly favourable influencing of the mesophases and of the electro-optical properties of the compounds in accordance with the invention. Thus, the compounds in accordance with the invention exhibit e.g. high clearing points and low threshold potentials, but without having an undesirably high electrical conductivity.
In spite of the high clearing points, the compounds in accordance with the invention have a comparatively low viscos
REFERENCES:
patent: 4267388 (1981-05-01), Drakes et al.
patent: 5013476 (1991-05-01), Boller et al.
patent: 5183587 (1993-02-01), Kitano et al.
Kitano, K., et al. Molecular Crystals and Liquid Crystals, vol. 191, pp. 205-209 (1990).
Derwent Abstract No. 91-141456/20.
Schadt Martin
Seils Frank
Gould George M.
Hoffmann-La Roche Inc.
Johnston George W.
Parise John P.
Wu Shean
LandOfFree
Halovinyl-derivatives does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Halovinyl-derivatives, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Halovinyl-derivatives will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1095000