Compounds of the formula ##STR1## wherein Z.sup.1 denotes a single covalent bond or --CH.sub.2 Ch.sub.2 --; ring A.sup.1 represents 1,4-phenylene, pyrimidine-2,5-diyl, pyridine-2,5-diyl or, when Z.sup.1 stands for --CH.sub.2 CH.sub.2 --, also trans-1,4-cyclohexylene; X.sup.1 stands for fluorine or chlorine; X.sup.2 signifies fluorine, chlorine or hydrogen, with the proviso that X.sup.2 only signifies hydrogen when X.sup.1 is chlorine or when ring A.sup.1 signifies pyridine-2,5-diyl and Z.sup.1 signifies --CH.sub.2 CH.sub.2 --; and R.sup.1 signifies 1E-alkenyl with 2 to 12 carbon atoms, their manufacture, liquid crystalline mixtures which contain these compounds and their use for electro-optical purposes.
该公式化合物的
化学式为 ##STR1## 其中Z.sup.1表示单个共价键或--CH.sub.2 Ch.sub.2 --;环A.sup.1表示1,4-苯撑基,
嘧啶-2,5-二基,
吡啶-2,5-二基或者当Z.sup.1表示--CH.sub.2 CH.sub.2 --时,也可以是反式-1,4-环己撑基;X.sup.1表示
氟或
氯;X.sup.2表示
氟,
氯或氢,但是当X.sup.1为
氯或环A.sup.1表示
吡啶-2,5-二基且Z.sup.1表示--CH.sub.2 CH.sub.2 --时,X.sup.2只表示氢;R.sup.1表示2到12个碳原子的1E-烯基,其制造、包含这些化合物的液晶混合物以及它们用于电光目的的使用。