Stable electro=optical liq. crystal system - has dielectrically neutral liq. crystal and cpd. dielectrically positive liq. crystal cpd., with high flow viscosity

摘要

An electrooptical liq. crystal system which (a) contains between 2 electrodes, opt. on substrate plates, a dielectric positive liq. crystal and another optically transparent medium, (b) has irregular orientation of the liq. crystal molecule in the switched off state, (c) has index of refraction of the liq. crystal corresp. to the index of refraction of the matrix nM and/or has a quotient of the mass of the liq. crystal and the mass of the optically transparent medium of at least 1.5, (d) in one of the 2 switched states, independent of the polarisation of the incident light, has reduced transmission w.r.t. the other state, (e) has a liq. crystal based on dielectrically positive components which are also contains 1 or more dielectrically neutral liq. crystal cpds. of formula (E) and/or 1 or more dielectrically positive liq. crystals of formula (F) Sn formula R1 = 1-15C alkyl, in which 1 or 2 non-vincinal CH2 gps. may be replaced by -O-, -CO- and/or CH2=CH, (i) or (ii) Y = single bond -COO- X = e.g. R1 Q = e.g. (ii) Z1 = single bond or -CH2CH2-, Z2, Z3, Z4 = single bond -COO-, -OCO-, or CH2CH2-, R2, R3, R4 = 1-15C alkyl, in which 1 or 2 non-vicinal CH2 gps. may be replaced by -O-, -CO- and/or CH=CH. ADVANTAGE - Inclusion of (E) and/or (F) raises the flow viscosity to at least 35 square m/sec. at 20 deg.C and gives an optical anisotropy delta-n of 0.05-0.22 and a clear point Tc above 75 deg.C. The systems are free from flicker on appln. of an alternating current, and have high stability to temp. and UV.