Trifluoromethylcyclohexane derivatives

Details Trifluoromethylcyclohexane derivatives Trifluoromethylcyclohexane derivatives

1990-06-15

1993-05-11

Stoll, Robert L.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229961, 25229901, 25229962, 25229966, 25229968, 544298, 549369, 570129, 546339, C09K 1930, C09K 1952, C07D31906, C07C 1908

Patent

active

052098680

DESCRIPTION:

BRIEF SUMMARY
The invention relates to trifluoromethylcyclohexane derivatives of the formula I ##STR3## where
R is an alkyl or alkenyl radical having up to 18 C atoms which is unsubstituted or substituted by CN or by at least one halogen, and in which one or more non-adjacent CHz groups may be replaced by a radical selected from the group comprising --O--, --S--, --CO--, --O--CO--, --CO--O-- and --C.tbd.C--,
A.sup.1 and A.sup.2 are each, independently of one another, by N, may.be replaced by --O-- or --S--, or naphthalene-2,6-diyl radical, polysubstituted by halogen atoms or cyano and/or methyl groups, ##STR4##
Z.sup.1 and Z.sup.2 are each, independently of one another, --CO--O--, --O--CO--, --CH.sub.2 CH.sub.2 --, --CH(CN)--CH.sub.2 --, --CH.sub.2 --CN(CN)--, --CH.dbd.CH--, --OCH.sub.2 --, --CH.sub.2 O--, --CH.dbd.N--, --N.dbd.CH--, --NO.dbd.N--, --N.dbd.NO--, --N.dbd.N-- or a single bond, and
o is 0, 1 or 2.
The invention furthermore relates to the use of these compounds as components of liquid-crystalline media, and to liquid-crystal and electrooptical 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, including highly twisted variants thereof, such as, for example, STN or SBE, the guest-host effect, the effect of deformation of aligned phases or the effect of dynamic scattering in particular for matrix liquid-crystal displays (MLC displays).
The invention had the object of finding novel stable liquid-crystalline or mesogenic compounds which are suitable as components of liquid-crystalline media and in particular have comparatively low viscosity and a moderate positive dielectric anisotropy.
It has now been found that compounds of the formula I are pre-eminently suitable as components of liquid-crystalline phases. In particular, they have comparatively low viscosities. Using them, stable liquidcrystalline phases which have a broad mesophase range, advantageous values for the optical and dielectric anisotropy and are at the same time distinguished by very favourable values for the specific resistance can be obtained. This gives considerable advantages, in particular in the case of media for matrix liquid-crystal displays (MLC displays) or supertwist displays.
Similar compounds having liquid-crystalline properties have already been disclosed, for example in EP-A-0,0193,191 (sic), JP 59/078,129 or JP 58/198,427. In these, however, the trifluoromethyl group is linked to a phenyl radical and they therefore generally have comparatively disadvantageous values for the optical anisotropy and are significantly inferior to the compounds according to the invention for modern display applications.
JP 60/69,059 and JP 63/238,030 disclose similar compounds which, however, contain a ##STR5## in which X is CN, F or Cl.
Furthermore, compounds are known which contain a trifluoromethylcyclohexyl group, but do not have any mesogenic properties. Thus, for example, JP 63/51,354 describes cyclohexanecarboxylic acids which are substituted by a trifluoromethyl group, and the preparation thereof.
K. W. Baldrin, M. J. T. Robinson [Tetrahedron 33, 1663-1668 (1977)] carried out studies on various 1-trifluromethyl-3-substituted cyclohexanes.
Furthermore, DE-OS 3,022,818 mentions, in a general formula, 4,4'-disubstituted bicyclohexylenes, inter alia, as mixture components of liquid-crystalline media, it also being possible for one of the substituents to be a trifluoromethyl group.
However, there is no explicit mention therein of a compound of this type nor of the preparation thereof, neither is it possible for a person skilled in the art to deduce the excellent properties of these compounds nor a preparation procedure.
In addition, the provision of the compounds of the formula I very generally considerably extends the range of liquid-crystalline substances which are suitable, from various applicational points of view, for the preparation of liquid-crystallin

REFERENCES:
patent: 4348298 (1982-09-01), Zaschke et al.
patent: 4398803 (1983-08-01), Pohl et al.
patent: 4402849 (1983-09-01), Krause et al.
patent: 4505837 (1985-03-01), Romer et al.
patent: 4684476 (1987-08-01), Kitano et al.
patent: 4871469 (1989-10-01), Reiffenrath et al.
Finkenzeller et al., "Physical Properties of Liquid Crystals: III. Dielectric Permittivities," E. Merck, Darmstadt, Germany.

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