Liquid crystal mixt. with specified double refraction - contains 4-substd. 3,5-di:fluoro-4-(trans-4-(substd.( alk(en)yl-cyclohexyl)-bi:phenyl cpds., used for electro=optical purposes

Liquid crystal (LC) medium with a double refraction delta n of at least 0.12 is based on a mixt. of polar cpds. with positive dielectric anistropy. It contains 4-substd.-3',5'-difluoro- 4'-(trans-4-(substd.) alk(en)yl-cyclohexyl)-biphenyl cpd(s). (I) of the formula (I) (where X = F, Cl, CF3, OCF3 or OCHF2; R = alkyl, oxaalkyl, fluoroalkyl or alkenyl with up to 7C). USE/ADVANTAGE - Used for electro-optical purposes, esp. in LCDs. It is esp. suitable for matrix, TN and STN displays and combines very high specific resistance with low threshold voltage. Incorporating a relatively small amt. of (I) greatly improves the response time and gives wide nematic phases with low smectic-nematic transition temps. (I) are colourless, stable and readily miscible with other LC materials.