JP2960975B

Chiral dopes of the formula in which n is the number 0 or 1, R is a group of the formula or A , A and A , independently of one another, are 1,4-phenylene which is unsubstituted or substituted by halogen, cyano and/or methyl and in which 1 or 2 CH groups have optionally been replaced by nitrogen, 4,4'-biphenylene, trans-1,4-cyclohexylene, trans-1,3-dioxane-2,5-diyl or naphthalene-2,6-diyl, Z and Z , independently of one another, are a single covalent bond or -CH2CH2-, Z and Z , independently of one another, are a single covalent bond, -CH2CH2-, -COO-, -OOC-, -CH2O-, -OCH2-, -C IDENTICAL C-, -(CH2)4-, -(CH2)3O-, -O(CH2)3- or the trans-form of -CH=CH-CH2CH2-, -CH2CH2-CH=CH-, -CH=CH-CH2O- or -OCH2-CH=CH-, with the proviso that, if R is a group of the formula II, at least one of the groups Z and Z is -(CH2)4-, -(CH2)3-O-, -O-(CH2)3- or the trans-form of -CH=CH-CH2-CH2-, -CH2-CH2-CH=CH-, -CH=CH-CH2-O- or -O-CH2-CH=CH-, R , R and R are hydrogen, alkyl, phenyl or alkoxycarbonyl, R is alkyl, phenyl or alkoxycarbonyl, R is hydrogen, halogen, cyano, trifluoromethyl, trifluoromethoxy or alkyl in which one &rdurule& CH-CH &ldurule& has optionally been replaced by &rdurule& C=C &ldurule& and/or one or two non-adjacent methylene groups have optionally been replaced by -O-, -COO- and/or -OOC- and/or one methylene group has optionally been replaced by -CHX-, X is halogen, cyano or methyl, and the dioxolane ring shown in the formula I is in optically active form, liquid-crystalline mixtures which contain dopes of this type, and their use for optical and electro-optical purposes.