Generation mechanism of residual direct current voltage in a liquid crystal display and its evaluation parameters related to liquid crystal and alignment layer materials

摘要

The presence of ionic charges in a liquid crystal layer causes the generation of residual direct current (dc) voltage (V_(rdc)) in a liquid crystal cell. V_(rdc) is one of the most important factors governing the image quality of liquid crystal displays, because the existence of V_(rdc) causes the image sticking phenomenon. We studied the generation mechanism of V_(rdc) based on a model of the adsorption and desorption of the ionic charges at the interface between the liquid crystal and alignment layer. In this paper, we propose three evaluation parameters, (ⅰ) saturated residual dc voltage, (ⅱ) time to reach its saturation state, and (ⅲ) relaxation time during the open circuit state after applying the external dc voltage, for effective evaluation of liquid crystal and alignment layer materials from the viewpoint of the improvement of the image sticking.