High holding ratio electro=optical system - contg. liq. crystal mixt. with specified component and polymeric medium made from fluorine contg. precursor giving max. liq. crystal solubility

摘要

Electro-optical systems of the type in which (A) a liq. crystal (LC) mixt. and a further optically transparent polymeric medium (OTPM) are positioned between 2 electrodes, one of which is formed as an active matrix with nonlinear, image-integrated control elements and the other of which is a counter-electrode; (B) the LC mols. are in random orientation in the switched-off state; (C) one of the RIs of the LC mixt. corresponds to the RI of the OTPM and/or the ratio LC mixt. at.: OTPM wt. = 1.5 or more; and (D) incident light shows a reduced transmission in one of the two switching states; this being independent of polarisation are claimed. Specifically, (i) the LC mixt. contains one or more cpds. of formula (I); and (ii) in order to increase the solubility of the LC mixt. in the OTPM precursor, the precursor contains 0.1-95% of a component (A) which is a fluorinated-, or oligo- or per-fluorinated aliphatic monomer, oligomer and/or prepolymer, the pref. (A) contg. a structural element of formula (II). In the formulae, Z1 and Z2 = single bond, -CH2CH2-, -COO-, -OCO- or -CC-; rings A1 and A2 = trans-1,4-cyclohexylene, 1,4-phenylene, 2- or 3-fluoro-1,4-phenylene or 2,3- or 3,5-difluoro- 1,4-phenylene, with one of A1 and A2 also being pyrimidin-2,5-diyl, pyridin-2,5-diyl or trans-1,3-dioxan-2,5-diyl; X1-4 = H or F; Q = CF2, OCF2, C2F4 or OC2F4 or a single bond; Y = H, F or Cl; n = 0, 1 or 2; R = up to 12C alkyl with 1 or 2 non-neighbouring CH2 gps. opt. replaced by -O- or -CH=CH-; and Y1-5 = such that (i) up to 2 of Y1-3 = H or F; (ii) at least 1 and upto 3 of them are a single bond and/or 1-30C alkylene gps. in which 1-15 of the CH2 gps. can be replaced by -O-, -CO-, -COO-, -OCO-, -S-, -CHHal-, -C(Hal)2- or opt. substd. satd. or aromatic cyclic diyl gps., with the proviso that -O- and/or -S- are not directly connected, and (iii) up to 2 of them are 1-30C alkyl with 1-15 CH2 gps. opt. replaced as for the alkylene gps. above. USE/ADVANTAGE - Devices with thin film transistor electrodes can be provided in which the LC/OTPM network has a high holding ratio (even at high temps. and under UV radiation) combined with a favourable threshold voltage and good stability.