Methylenecyclobutane derivatives

Details Methylenecyclobutane derivatives Methylenecyclobutane derivatives

1993-09-15

1995-01-24

Wu, Shean

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229901, 359103, 560123, C09K 1930, C07C 6974, G02F 113

Patent

active

053840720

DESCRIPTION:

BRIEF SUMMARY
SUMMARY OF THE INVENTION
The invention relates to methylenecyclobutane derivatives of the formula I ##STR2## in which R.sup.1 is halogen, CN, CF.sub.3, --OCF.sub.3, --OCF.sub.2 H or an alkyl or alkenyl or perfluoroalkyl radical having up to 15 carbon atoms which is unsubstituted or monosubstituted by CN, halogen or CF.sub.3, where one or more CH.sub.2 groups in these radicals may each, independently of one another, be replaced by --S--, ##STR3## --O--, --CO--, --CO--O--, --O--CO-- or --O--CO--O-- in such a way that S and/or O 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, 1,3-bicyclo(1,1,1)-pentylene, 1,4-cyclohexenylene, 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, CN or halogen, CH.sub.2 --, --C.tbd.C--, --CH.sub.2 O--, --OCH.sub.2, --CO--O--, --O--CO--, --CH.dbd.N--, --N.dbd.CH--, --CH.sub.2 S--, --SCH.sub.2 --, a single bond or an alkylene group having 3 to 6 carbon atoms in which, in addition, one CH.sub.2 group may be replaced by --O--, --CO--O--, --O--CO--, --CH halogen- or --CHCN--, COO-alkyl or alkyl having 1 to 6 carbon atoms one of the radicals X and Y is alternatively H, and Z.sup.2 is a single bond, and X and Y are not simultaneously F.
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, 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.
The invention had an object of finding novel stable liquid-crystalline or mesogenic compounds which are suitable as components of liquid-crystalline media and have, in particular, relatively low viscosity and moderate positive dielectric anisotropy.
It has now been found that compounds of the formula I are eminently suitable as components of liquid-crystalline phases. In particular, they have relatively low viscosities. They can be used to obtain stable liquid-crystalline phases having a broad mesophase range advantageous values for the optical and dielectric anisotropy, which are simultaneously distinguished by very favorable values for the specific resistance. This allows significant advantages to be achieved, in particular in the case of media for active matrix displays or supertwist displays.
Similar compounds containing a disubstituted methylenecyclobutane group are already known. However, these do not have liquid-crystalline properties.
W. R. Dolbier, et al., Tetrahedron Letters 28 (14), 1491-1492, 1987, describe, for example, the preparation of 3-phenyl-1-(difluoromethylene)cyclobutane and 3-phenyl-2,2-difluoro-1-methylenecyclobutane and the cycloaddition of difluoroalkene to styrene.
In addition, the provision of the compounds of the formula I very generally considerably broadens the range of liquid-crystalline substances which are suitable from various applicational 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 chosen substituents, these compounds can be used as base materials from which liquid-crystalline phases are predominantly composed; however, it is also possible to add compounds of the formula I to liquid-crystalline base materials from other classes of compound 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.
The compounds of the formula I according to the invention containing a chiral group of the formula ##STR4## in which X and Y are different from one another, and MG is a mesogen

REFERENCES:
Dolbier, "The effect of styrene alpha-substituents on the regiochemistry of (2+2) cycloadditions with difluoroallene", Tetrahedron Letters, vol. 28, No. 14 (1987), pp. 1491-1492.

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