New low viscosity liquid crystal compounds containing the 2,3,4-trifluorophenyl moiety for active matrix displays

Abstract

The synthetic route and physical properties for new three-ring derivatives, trans-4- ⁿ -alkyl-4′-(2,3,4-trifluorophenyl)bicyclohexanes ( ⁿ CCHB3F) with alkyl chain length ⁿ from 2 to 5 are presented. They exhibit broad range nematic phases exceeding 40 K, and low viscosity with a low activation enthalpy; they also show low dielectric anisotropies and high birefringence. Their dielectric properties are compared with those of their three-ring homologues with a lateral -NCS group. The Maier-Meier theory is used to evaluate the temperature dependence of the value of ‘dielectric anisotropy divided by order parameter (j k / S)’. The temperature dependence of j k / S in several phenylbicyclohexane homologues is explained. Furthermore, the viscosity of nematic liquid crystal mixtures containing these materials is significantly reduced. These mixtures are suitable for the improvement of the switching time of liquid crystal displays using TFT Twisted Nematic (TN) modes.

Keywords:

• 10.1080/0267829021000018086