Further studies of the dynamic scattering mode in nematic liquid crystals

Abstract

Evaluation of fabrication procedures and operating life have indicated that moisture can play a major role in determining the performance of nematic liquid crystal displays based on the dynamic scattering mode (DSM) in anisylidene-p-aminophenyl-acetate. There is strong evidence that the presence of moisture promotes electron injection by lowering the potential barrier between the metal electrode and the liquid crystal. This could arise from a lowering of the effective work function of the metal by adsorption and/or increasing the electron affinity of the liquid crystal by molecular attachment. In any case the injected electron is captured by a neutral molecule and transported as a negative ion. The electron is removed by an oxidation process at the anode leaving the original molecular species free to repeat the process. It was also found that a short pulse (shorter than a space charge build-up time) could be used to electrically quench dynamic scattering and appreciably reduce the relaxation time. The use of this new scheme significantly improves the brightness and contrast of matrix addressed, real time displays based on dynamic scattering. A novel laminate structure for realizing such displays is also presented.