| abstract |
Liq. crystal medium based on a mixt. of cpds. with positive dielectric anisotropy contains at least one cpd. of formula (I). A1 and A2 = trans-1,4-cyclohexylene, 1,4-phenylene or 3-fluoro-1,4-phenylene; Z = -CH2CH2- or a bond; L and Y = H or F; X = Cl, F, CF3, OCF3 or OCHF2; and R = alkyl, hydroxyalkyl, fluoroalkyl or alkenyl, each with up to 7C. The amt. of (I) is pref. 10-50wt.%. USE/ADVANTAGE - The medium can be used in matrix-, twisted nematic-or super-twisted nematic-cells and has, compared to liq. crystal compsns., broadened nematic phase range (esp. at low temp.), switchability at low temps. (e.g., for outdoor, automobile or avionic use), increased UV resistance, improved clear pt., lower viscosity at low temps. and improved heat stability. Viscosity at -30 deg.C is 600 m.Pd.s or less and at -40 deg.C 1800 m.Pa.s or less, while anisotropy (delta-epsilon) value is 3.5 or above and clear pt. is above 65 deg.C. The nematic phase range is -30 to +70 deg.C. (27pp Dwg.No.0/0) |