Terminal trifluoromethyl-alkoxy and-alkenyloxy nematic liquid crystals for LCDs with active matrix addressing

Abstract

We have synthesized a new class of compounds suitable for LCD applications, incorporating a trifluoromethyl group in the terminal alkoxy- or alkenyloxy-chain. These compounds appear to fulfil many of the requirements for use in TN-LCDs. Core units containing a cyclohexyl ring, which tend to induce a lower viscosity than that of the analogous aromatic materials, were synthesized. Systems containing several aromatic rings were also prepared with a view to producing compounds of high birefringence. Compounds containing a lateral fluorosubstituent as well as a polar substituent in a terminal position were synthesized in order to generate a high positive value of the dielectric anisotropy. Molecules incorporating a bicyclo[2.2.2]octane ring were also synthesized in order to produce a high nematic clearing point and to influence the elastic constants. Compounds with three 1,4-disubstituted rings were synthesized with a view to producing materials with a high nematic clearing point and as low a melting point as possible. A series of compounds with a carbon-carbon double bond in the terminal chain was prepared in an attempt to produce compounds with appropriate values and ratios of the elastic constants.