Study on the structure of polyimide/polyethylene glycol blend film and their applications to liquid crystal alignment layer

Abstract

This thesis deals with the materials for liquid crystal alignment layer used in liquid crystal displays(LCDs) and can be divided into two parts. One part is about the effect of curing conditions on the structure of polyimide film which was widely used alignment layer material. The other part is about the development of static charge reducible alignment layer with a need to prevent the problems associated with the static charge created by rubbing. Chapter II and chapter III describe the effects of curing conditions on the structure of polyimide film cast on silicon wafer. In chapter II, effect of residual solvent on the degree of imidization of PMDA-ODA film was investigated. The final amount of solvent was better correlated with the eventual degree of imidization than the initial amount of solvent, which indicates that the strongly bound solvent can act as a plasticizer aiding thermal imidization and the weakly bound one readily evaporates not contributing to thermal imidization. In chapter III, effects of thermal curing method on the structure of polyimide film were investigated. The isothermal curing was found to be more effective for high degree of imidization and high degree of chain ordering compared to stepwise curing. However, the in-plane orientation was found to be higher for stepwise curing compared to isothermal curing, indicating the importance of chain immobilization rate on in-plane orientation. In chapter IV and chapter V, I studied on the PMDA-BDAF/PEG blend which could reduce the static charge on the alignment layer generated by rubbing. In chapter IV, the characteristics of the PMDA-BDAF/PEG blend film was investigated. The two components were found to be miscible irrespective to blend ratio, resulting in optical transparency. PEG crystal was disrupted in the blend indicating the molecular interaction between PEG and polyimide. Thermal stability of PEG increased when incorporated into polyimide. Degree of imidization of the polyimide in the ...