My Three-Decade Investigation of Ions in EPDs and LCDs

Abstract

Ion concentration and its ionization activation energy and mobility are important parameters to affect flickers, image-sticking, Mura, panel assembly yield and reliabilities of TFT-LCDs. Prior publications to measure these parameters did not distinguish ions either from high (HIR) or low ionization rate (LIR) impurities. After persistent investigation for past three decades, I conclude that both ions of HIR and LIR impurities existed in EPDs, FLCDs and TN LCDs, and their ion generation and transport equations have been unified and described in our publications. For the first time, we have recently developed methods of measurement and analysis to obtain the ion concentration, mobility and activation energy of LIR impurities in a TN cell. Our recent results showed that most of ions existing in our TN cells came from ions of LIR impurities. Our experimental results on charge-trapping phenomena by uv-irradiated polyimide alignment layers seemed to indicate that the ions of LIR impurities were more likely to get trapped to produce image-sticking of LCDs.