Determination of Ion Concentrations and Mobilities from High- and Low-Ionization-Rate Impurities in TN LCDs

Abstract

Ion concentration and mobility are two most important parameters to affect the display qualities of LCDs in terms of flickers, image-sticking, and Mura. Prior publications on the measurement of ion concentration and mobility did not distinguish ions either from high- or low-ionization-rate impurities. For the first time, we have developed experimental and analytic methods to determine both mobilities and ion concentrations of high- and low-ionization-rate impurities perpendicular to liquid crystal directors in TN LCDs aligned by rubbed polyimide films. Our methods can also be extended to measure the ion mobilities and concentrations parallel to nematic liquid crystal directors by applying a high voltage on the TN cell or preparing samples with homeotropic LC alignments.