Compositions – Liquid crystal compositions
Patent
1992-08-05
1995-04-04
Wu, Shean
Compositions
Liquid crystal compositions
25229961, 25229963, 25229964, 25229965, 25229966, 25229967, 544303, 568655, 568661, 568631, 359103, C09K 1952, C07D23902, C07C 4302, G02F 113
Patent
active
054035120
DESCRIPTION:
BRIEF SUMMARY
SUMMARY OF THE INVENTION
The invention relates to novel vinyl compounds of the formula I ##STR2## in which R is H, an alkyl or alkenyl radical having 1 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF.sub.3 or at least monosubstituted by halogen, it also being possible for one or more CH.sub.2 groups in these radicals to be replaced, in each case independently of one another, by --O--, --S--, ##STR3## --CO--, --CO--O--, --O--CO-- or --O--CO--O-- in such a manner that oxygen atoms are not linked directly to one another, non-adjacent CH.sub.2 groups may be replaced by --O-- and/or --S--, be replaced by N, 1,4-bicyclo(2,2,2)octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl and 1,2,3,4-tetrahydronaphthalene-2,6-diyl, --O--CO--, --CH.sub.2 O--, --OCH.sub.2 --, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.dbd.C-- or a single bond, and one of the radicals Z.sup.1 and Z.sup.2 is alternatively --(CH.sub.2).sub.4 -- or --CH.dbd.CH--CH.sub.2 CH.sub.2 --, trans-CH.dbd.CH--, --COO-- or --CH.sub.2 O--, Cl.
The invention furthermore relates to the use of these compounds as components of liquid-crystalline media, and to liquid-crystal and electro-optical display elements which contain the liquid-crystalline media according to the invention.
The compounds of the formula I can be used as components of liquid-crystalline media, in particular for displays based on the principle of the twisted cell, the guest-host effect, the effect of deformation of aligned phases or the effect of dynamic scattering.
The invention had the object of finding novel, stable liquid-crystalline or mesogenic compounds which are suitable as components of liquid-crystalline media and simultaneously have, in particular, a relatively low viscosity and relatively high dielectric anisotropy.
It has now been found that compounds of the formula I are eminently suitable as components of liquid-crystalline media. In particular, they have relatively low viscosities. They can be used to obtain stable liquid-crystalline media having a broad mesophase range and advantageous values for the optical and dielectric anisotropy. These media furthermore have good low-temperature behavior.
BACKGROUND OF THE INVENTION
Difluorostyrene derivatives and corresponding liquid-crystalline media, such as, for example, containing compounds of the formula ##STR4## have already been disclosed in EP 0 325 796 A1. However, these compounds tend to be chemically unstable due to illumination of HF.
Various compounds having liquid-crystalline properties and containing a terminal CF.sub.3 group have already been disclosed (U.S. Pat. No. 4,330,426; U.S. Pat. No. 4,684,476; J. C. Liang and S. Kumar, Mol. Cryst. Liq. Cryst. 1987; Vol. 142, pp. 77-84). However, these compounds frequently have a highly smectogenic character and are less suitable for many practical applications.
However, in view of the very wide variety of areas of application of compounds of this type having a high .DELTA..epsilon., it was desirable to have available further compounds which have properties precisely customized for the particular applications.
DETAILED DESCRIPTION OF THE INVENTION
In addition, the provision of compounds of the formula I very generally extends the range of liquid-crystalline substances which are suitable, from various application points of view, for the preparation of liquid-crystalline mixtures.
The compounds of the formula I have a broad range of applications. Depending on the choice of substituents, these compounds can be used as base materials from which liquid-crystalline media are predominantly composed; however, it is also possible to add compounds of the formula I to liquid-crystalline base materials from other classes of compounds in order, for example, to modify the dielectric and/or optical anisotropy of a dielectric of this type and/or to optimize its threshold voltage and/or its viscosity.
In particular, compounds of the formula I in which X.sup.1 =H and X.sup.2 =F are distinguished by their high clearing point at the same t
REFERENCES:
patent: 4877548 (1989-10-01), Kitano et al.
patent: 4880562 (1989-11-01), Kitano et al.
patent: 5183587 (1993-02-01), Kitano et al.
Bartmann Ekkehard
Eidenschink Rudolf
Hittich Reinhard
Junge Michael
Meyer Volker
Merck Patent Gesellschaft mit beschrankter Haftung
Wu Shean
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