| 摘要 |
The invention relates to compounds of the formula <IMAGE> in which R<1> and R<2>, independently of one another, are hydrogen, halogen, cyano, or alkyl, alkenyl or alkynyl having 1 to 15 or 2 to 15 carbon atoms which is unsubstituted or monosubstituted or polysubstituted by halogen, cyano or trifluoromethyl and in which one or more non-adjacent -CH2- groups may be replaced by -O-, -S-, -CO-, -COO- and/or -OOC-; A<1>, A<2>, A<3>, B<1> and B<2>, independently of one another, are 1,4-phenylene which is unsubstituted or monosubstituted or polysubstituted by halogen, cyano and/or methyl and in which, if unsubstituted, one or more CH groups may be replaced by nitrogen, or are unsubstituted or halogen- or cyano-substituted trans-1,4-cyclohexylene or 1,4-cyclohexenylene, trans-1,3-dioxane-2,5-diyl or trans-1,3-diathiane-2,5-diyl; with the proviso that A<3> and B<1> are not simultaneously 1,4-phenylene if Q<1> and Q<2> are both a single bond: Z<1>, Z<2> and Z<3>, independently of one another, are a single bond, -CH2CH2-, -OCH2-, -CH2O-, -COO-, -OOC-, -C IDENTICAL C-, -(CH2)4-, -(CH2 )3O-, -O(CH2)3, the trans-form of -CH=CH-, -CH=CH(CH2)2-, -(CH2)2CH=CH-, -OCH2CH=CH- or -CH=CHCH2O-; Q<1> is a single bond, -CH2CH2-, -OCH2-, -CH=CH-, -CF2CF2-, -CF=CF- or -OOC-; Q<2> is a single bond, -CH2CH2-, -CH2O-, -CH=CH-, CF2CF2-, -CF=CF- or -COO-; l and m, independently of one another, are either 0 or 1; and n is 0, 1 or 2, with the proviso that l + n + m is </= 2, to liquid-crystalline mixtures containing such compounds, and to the use of such compounds and mixtures for optical and electro-optical purposes.
|
