Fluoro-isothiocyanated liquid crystal materials with high dielectric anisotropy and voltage holding ratio

As liquid crystal (LC) materials for TFT-TN display, two-ring and three-ring homologues with 2-fluoroisothiocyanatophenyl and 2,6-difluoroisothiocyanatophenyl with high dielectric anisotropy and birefringence are prepared. In spite of the existence of a high polar -NCS group, the voltage holding ratio (VHR) of NLC mixtures contained in them is sufficiently high for application of active matrix addressing. In this paper, we will explain the voltage holding property of three types of liquid crystal materials included the terminal -NCS group considering their molecular parameters such as the Huckel charge, polarizability and dipole moment and the temperature and frequency dependence of voltage holding ratios are examined.