Liq. crystalline medium - contg. fluoro di:fluoro-methoxy benzene cpd. with cyclohexyl-cyclohexyl substit., used in electro=optical display

摘要

Liquid crystalline (LC) medium based on a mixt. of polar cpds. with positive dielectric anisotropy contains 4-(4-(trans-cyclohexyl) -trans-cyclohexyl)-2-fluoro- or 2,6-difluoro-1-difluoromethoxybenzene cpd(s) of formula (I), where R = 1-7C alk(en)yl, oxaalkyl or fluoroalkyl; L = H or F. (I) and other cpds. used in the medium are either known cpds. or can be prepd. by methods analogous to those used for known cpds. (Int. Patent Application PCT/EO 90 01 471). The medium pref. also contains 4-(trans-cyclohexyl)- or 4-(4-trans-cyclohexyl)-trans -cyclohexyl)-benzene cpd(s). (II), 4-(trans-cyclohexyl-ethyl)- or 4-(4-(trans-cyclohexyl) -trans-cyclohexyl-ethyl)-benzene cpd(s). (III) and/or 4-(4-trans-cyclohexyl-ethyl) -trans-cyclohexyl)-benzene cpd(s). (IV) etc.. In the formulae, X = F, Cl, CF3, OCF3 or OCHF2; Y = H or F; r = 0 or 1. The mixt. contains at least 50 (wt.) of (I)-(IV), pref. 10-50% (I) and 30-70% (II)-(IV). USE/ADVANTAGE - The medium is claimed for use for electrooptical purposes, esp. displays. It is esp. useful in matrix LCDs, TN and STN displays, giving very high specific resistance, low threshold voltage and short switching times. The nematic phase range is unusually wide and the elastic constants very high, whilst the viscosity is also very favourable.