Pyrimidines of the formula: ##STR1## wherein Y is nitrogen and Z is .dbd.CH--, or Z is nitrogen and Y is .dbd.CH--; R.sup.1 is alkyl and R.sup.2 is cyano, alkyl, p-alkylphenyl or trans-4-alkylcyclohexyl; where each alkyl denotes either a straight chain alkyl group of 1 to 12 carbon atoms or a branched chain alkyl group of the formula C.sub.2 H.sub.5 --CH(CH.sub.3)--(CH.sub.2).sub.n, n is 1, 2 or 3; with the proviso that the compound contains at most only one of said branched chain alkyl group and with the further proviso that the sum of the carbon atoms in all of the alkyl groups within the compound is at most 14 are described. Liquid crystalline mixtures comprising Compound I as well as their use in electro-optical devices also are disclosed.
本发明涉及式为##STR1##的
嘧啶类化合物,其中Y为氮,Z为.dbd.CH--,或Z为氮,Y为.dbd.CH--;R.sup.1为烷基,R.sup.2为
氰基,烷基,对烷基苯基或反式-4-烷基环己基;其中每个烷基表示1至12个碳原子的直链烷基或式为C.sub.2 H.sub.5 --CH(CH.sub.3)--(CH.sub.2).sub.n的支链烷基,n为1、2或3;但该化合物至多只含有一个所述的支链烷基,并且所有烷基中碳原子的总和最多为14。还公开了含有化合物I的液晶混合物以及它们在电光器件中的使用。