Nematic liquid crystals of 5-cyano-2-[4-acyloxyphenyl]-pyrimidines and mixtures containing the same

Abstract

Nematic liquid crystals are employed in electro-optical devices for the modulation of the transmittant or incident light and for the black and white or colored rendition of numerals, symbols and pictures. The object of the invention is the use of nematic liquid crystals having a high positive dielectric anisotropy, a low threshold and operating voltage and high clear points and a process for making these compounds. It was found that as liquid crystals for electro-optical devices mixtures are useful which, as an essential component, contain one or several compounds from the class of 5-cyano-2-[4-acyloxyphenyl]-pyrimidines of the formula ##STR1## wherein R.sup.1 is ##STR2## C.sub.5 H.sub.11 -- or C.sub.n H.sub.2n+1 O-- R.sup.2 is C.sub.n H.sub.2n+1 ; C.sub.n H.sub.2n+1 O; C.sub.n H.sub.2n+1 S; F; Cl; Br; CF.sub.3 ; C.sub.n H.sub.2n+1 COO; C.sub.n H.sub.2n+1 OCOO; CN; NO.sub.2 ; C.sub.n H.sub.2n+1 NH; or C.sub.n H.sub.2n+1 (CH.sub.3)N, n is 1 to 10, and R.sup.3 is C.sub.n H.sub.2n+1, n is 1 to 10.

Dependencies are inferred from the claim text.