Twisted and supertwisted nematic liquid crystal displays for multiplex systems having very short switch times comprise nematic mixture containing compound with terminal cyanoethynyl group and compound with terminal alkenyl group

摘要

Twisted nematic (TN) and supertwisted nematic (STN) liquid crystal displays contain a nematic liquid crystal mixture containing 2 or more compounds, one of which has a terminal -C equivalent to C-CN group and is optionally F-substituted and another of which has a terminal alkenyl group. Twisted nematic (TN) and supertwisted nematic (STN) liquid crystal displays contain a nematic liquid crystal mixture containing a terminal -C equivalent to C-CN group containing compound of formula (I) and one or more alkenyl compounds of formula (II). The display is of the type with 2 plates enclosing a nematic positively dielectric anisotropic liquid crystal mixture, and there being electrodes with orientation layers on the insides of the plates such that the angle between the longitudinal molecular axis and the plates is 0-30 deg and the twist angle of the liquid crystal mixture from orientation layer to orientation layer is 22.5-600 deg . The liquid crystal mixture contains (by wt.): (a) one or more compounds of dielectric anisotropy above +1.5 (15-80%); (b) one or more compounds of dielectric anisotropy between -1.5 and +1.5 (20-85%); (c) one or more compounds of dielectric anisotropy below -1.5 (0-20%); and (d) optionally sufficient optically-active compound to give a ratio between the layer thickness (inter-plate distance) and the natural helix pitch of the chiral liquid crystal mixture of ca. 0.2-1.3. R1 and R4 = 1-12C alkyl, alkoxy or alkenyl with 1 or 2 non-adjacent -CH2- groups replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- such that the O atoms are not directly linked; R3 = 2-7C alkenyl; L = H or F; and a = 0 or 1.