Electro-optical properties of conic cylindrical-cavities liquid crystal displays

Abstract

Experimental results have shown that the conic cavities in conic closed-cavity liquid crystal displays (conic CCLCDs) can give a wide viewing angle and grey levels without grey-scale inversion. The purpose of this paper is to extend investigations of conic CCLCDs. In experiments, we describe in detail the fabrication process, microscopic observations and optical measurements for conic CCLCDs. The simulation of director distribution will be based on the tensor form formulation of the free energy density. The differential equations satisfied by the steady-state director distribution are derived from this form of free energy and are solved in conjunction with Poisson's equation. The simulation of the optical propagation and the calculation of the optical transmittance will be based on the extended Jones matrix method. We show by simulation that a normal umbilical structure is the final stable state and that indeed conic CCLCDs can have a wide viewing angle and grey scale without grey-scale inversion. The theoretical results are compared with the experimental results. Transmittance, contrast ratio and viewing angle with various parameters of the LC are measured. Improved iso-contrast contours of the conic CCLCD with a c-plate compensator are also shown. Finally, we have also compared the electro-optical performance and the off axis colour-shift of the CCLCD, the 4-domain VAN device and the 4-domain twist-VAN device.