High holding ratio, micro-droplet or network electro=optical system - contg. specified cpd. in liq. crystal mixt. and with polymerisation of transparent medium initiated by radical photoinitiator

摘要

An electro-optical system is claimed in which (a) a liq. crystal mixt. and a further optically transparent polymeric medium are present between 2 electrode layers, one of which acts as an active matrix, non-linear, image-integrated control element and the other of which forms a counter-electrode; (b) the liq. crystal mol. shows random orientation in the switched-off condition; (c) one of the RI's of the liq. crystal mixt. corresponds to the RI of the polymer medium and/or the ratio of the mass of the liq. crystal mixt. to the mass of optically transparent medium is 1.5 or higher; and (d) one of the 2 switching states shows reduced transmission compared to the other, irrespectively of the polymerisation of the incident light. The liq. crystal mixt. contains one or more cpds. of formula (I); and the polymerisation of the optically transparent medium is initiated by a radical-forming photo-initiator. In (I), n = 0, 1 or 2; Z1 and Z2 = a bond, -CH2CH2-, -COO-, -OCO or -CC-; rings A1 and A2 = independently trans-1,4-cyclohexylene, 1,4-phenylene, 2- or 3-fluoro-1,4-phenylene or 2,3- or 3,5-difluoro-1,4-phenylene and one of A1 and A2 can also be pyrimidin-2-diyl, pyridin-2,5-diyl or trans-1,3-dioxan-2,5-diyl; X1-3 = H or F; Y = F, Cl, OCF3, OCHF2 or CR3; and R = up to 12C alkyl where one or two non-neighbouring CH2 gps. can be replaced by -O- and/or -CH=CH-. USE/ADVANTAGE - The system can be of the type with an active matrix-controlled discrete microdroplet or 3-D network structure. It has optimum characteristics and, in particular, a high Holding Ratio (HR)