Patent ID: 6159393
Filing Date: 2000-12-12
Classification: C07C,C09K

Abstract:
A liquid-crystalline medium based on a mixture of polar compounds having positive dielectric anisotropy, characterized in that it contains one or more compounds of the general formula I ##STR106## 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 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--, ##STR107## --CO, --CO--O--, --O--CO-- or --O--CO--O-- in such a way that O atoms are not linked directly to one another,A.sup.1 and A.sup.2 are each, independently of one another, a trans-1,4-cyclohexylene radical in which, in addition, one or more non-adjacent CH.sub.2 groups may be replaced by --O--, --S--, or both, or a 1,4-cyclohexenylene radical,Z.sup.1 and Z.sup.2 are each, independently of one another, --CO--o--, --O--CO--, --CH.sub.2 O--, --OCH.sub.2 --, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.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 --,Y is F, Cl, halogenated alkyl, alkenyl or alkoxy having 1 to 6 carbon atoms,L.sup.1 is H or F, andm is 0or 1,and one or more compounds selected from the group consisting of the general formulae II, III, IV, V and VI: ##STR108## in which the individual radicals are as defined below: R.sup.0 is n-alkyl, oxaalkyl, fluoroalkyl or alkenyl, in each case having up to 7 carbon atoms,X.sup.0 is F, Cl, halogenated alkyl, alkenyl or alkoxy having 1 to 6 carbon atoms,Y.sup.1 and Y.sup.2 are each, independently of one another, H or F,r is 0 or 1,with the provisos thata) the compounds III and IV are not identical to the compounds of the formula I,b) if L.sup.1 is X m=1, A.sup.1 and A.sup.2 are each trans-1,4cyclohexylene radicals, Z.sup.1 is a single bond and Z.sup.2 is --CH.sub.2 CH.sub.2 --, then Y is not Cl,c) if L.sup.1 H, m=0, A.sup.2 is a trans 1,4-cyclohexylene radical and Z.sup.1 is --CH.sub.2 CH.sub.2 --, then Y is not F, Cl, --CF.sub.3, --OCHF.sub.2, --CHF.sub.2 or --OCF.sub.3,e) if Y.sup.1 and Y.sup.2 on the central phenylene ring of formula IV are F, r of formula IV is 1, Z.sup.2 of formula I is a single bond, and m=0, then Y is halogenated alkyl, alkenyl or alkoxy having 2-6 carbon atoms.