Super twist liquid crystal display with good contrast and angle dependence and very short switching time

摘要

A supertwist liquid crystal display (LCD) has a cell with 2 plane-parallel substrate plates, with electrode layers and orientation films, filled with a nematic liquid crystal (LC) mixture with positive dielectric anisotropy. The tilt angle is 1-30 deg and the twist angle 100-600 deg . The LC mixture contains (a) 10-65 wt.% LC component A, consisting of compound(s) with a dielectric anisotropy above +1.5; (b) 20-90 wt.% LC component B, consisting compound(s) with a dielectric anisotropy between -1.5 and +1.5; (c) 0-20 wt.% LC component D, consisting of compound(s) with a dielectric anisotropy below -1.5; and (d) an optically active component C in such an amounts that the ratio between the film thickness (distance between the substrate plates) and natural pitch of the chiral nematic LC mixture is 0.2-1.3. The novelty is that component B contains 4-(trans-4-alkenylcyclohexyl) -4'-alkyl-biphenyl(s) of formula (I) and component A contains 4-cyano-3-fluorophenyl 4-alkyl- or 4-(trans-4-alkylcyclohexyl) -benzoate(s) of formula (II); in which Alkenyl = an alkenyl group with up to 7 carbon (C) atoms; R = 1-12 C alkyl, in which 1 or 2 non-adjacent methylene (-CH2-) groups may be replaced by oxygen (-O-), ethenylene (-CH=CH-), oxycarbonyl (-OCO-) or carbonyloxy (-COO-); b = 0 or 1; L<2> = hydrogen (H) or fluorine (F). Also claimed is the LC mixture used.