Synthesis and Physical Properties of Novel Fluorinated Liquid Crystalline Compounds

Abstract

ABSTRACT Most twisted nematic liquid crystal displays (TN-LCD) uses liquid crystal mixtures with a positive dielectric anisotropy. In contrast, the recently introduced vertically aligned liquid crystal display (VA-LCD), which offers superior picture quality with a wide viewing angle, high contrast, and video-compatible switching times, is based on a liquid crystal mixture with negative dielectric anisotropy. We introduce here the synthetic route and physical and electro-optical properties of the liquid crystalline compounds with an ester group as linkage subsistent and with an alkyl chain as lateral subsistent. Also, we present physical and electro-optical properties of their mixture, and the LC-series for VA-LCD. Synthetic compounds exhibit broad range nematic phases up to 60 K degree and large negative dielectric anisotropies. And the viscosity of the LC-series is low in comparison with that of homologues with a lateral isothiocyanate group. The threshold voltage (Vth) was lower than that of a conventional mixture, enough so for it to be operated at a driving voltage. And the rising time of some LC-series improved to be faster than conventional LC mixtures. Our novel LC compounds are suitable materials for the improvement of the dielectric anisotropy of vertically aligned liquid crystal mixtures.