Two-layer liq. crystal cell - has compensating layer contg. liq. crystal linked 1,4-phenylene and trans-1,4-cyclohexylene rings

摘要

A liq. crystal (LC) cell contains 2 twisted nematic LC layers (A) and (B), in which at least one layer (A) is triggered, and in which the optical path differences in the 2 layers are essentially balanced. The LC used in the opt. un-triggered layer (B) is based on a dielectrically neutral component of formula: R-Phe-V-R (IA), R-Cyc-Phe-W-R (IB) or R-Phe-CC-Phe-Z3-(A)m-R (IC), and a dielectrically positive component of formula: R-X-Phe-CN (IIA), R-X-Cyc-CN (IIB) or R-X-Phe-COO-Phe-CN (IIC). Phe = 1,4-phenylene; Cyc = trans-1,4-cyclohexylene; R = 1-15C alkyl, oot. with 1 or 2 non-adjacent CH2 gps. replaced by O, CO, CH=CH and/or C(Hal)2; V = Z1-(A)n- (with Z1 = OCO or single bond); A = Phe or Cyc; W = Z1-Phe-Phe-, -Z1-Phe-Cyc-, -Z2-Cyc-Cyc- or -Z1-Phe-C2H4-Cyc- (with Z2 = CH2CH2, COO, OCO or single bond); X = -(A)-Z2-, -(2,5-pyridyl)-Z2- or -(2,5-(1,3-dioxolanyl))-Z3-(with Z3 = CH2CH2 or single bond); n = 1 or 2; m = 0 or 1. USE/ADVANTAGE - The LC components are useful in LC cells. The LC mixts. used for the compensating layer (B) have good values for dispersion, temp.-dependence of dispersion and birefringence (which can be optimised for partic. applications), together with high thermal and UV stability; the use of such LC layers (B) enables economical optimisation of the optical path difference ratio, and gives LC cells with optimum electro-optical properties. (13pp Dwg.No.0/0)