| 摘要 |
Liquid-crystal phases containing at least one optically active compound of the formula I R<1>-CO-O-CHR<o>-CH2-O-CO-R<2> where R<1> and R<2>, independently of one another, are each a -(A<1>-Z)m-(A<2>)n-Y group, in which A<1> and A<2> are each, independently of one another, a 1,4-phenylene, pyrimidine-2,5-diyl, 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 1,3-dithiane-2,5-diyl or 1,4-bicyclo[2.2.2]octylene group, it being possible for these also to be monosubstituted or polysubstituted by F, Cl, Br, CN and/or alkyl groups having up to 12 carbon atoms, where 1 or 2 non-adjacent CH2 groups in the alkyl groups may be replaced by O atoms, Z is -CO-O-, -O-CO-, -CH2CH2-, -OCH2-, -CH2O-, -CH=N-, -N=CH-, -N=N-, -N(O)=N- or a single bond, m and n are each, independently of one another, 0, 1 or 2, and Y is a straight-chain or branched alkyl group having up to 12 carbon atoms, where 1 or 2 non-adjacent and non-terminal CH2 groups may be replaced by O atoms, or if n is 1 or 2, is alternatively F, Cl, Br or CN, and R<o> is an alkyl group having up to 5 carbon atoms, a phenyl group or a cyclohexyl group, exhibit substantially temperature-independent electro-optical characteristics.
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