Generation of the Pretilt Angles and Electro-Optical Properties of Nematic Liquid Crystal Aligned on the Rubbed Plastic-Based Films

Abstract

We have investigated the generation of pretilt angle for a nematic liquid crystal (NLC) with rubbing alignment method on polyimide (PI) surfaces using thin plastic substrates. The NLC pretilt angles generated are about 3° by the rubbing alignment method on thin plastic substrates. However, the pretilt angles are at about 1.7° lower on the glass substrate than on thin plastic substrate. We obtain that AFM (atomic force microscope) image of rubbed PI surface with polymer film has formed the micro-groove structure at the low curring temperature (120°C). However, no grooves are obtained on the glass substrate at the same temperature. The tilt angle increases with increasing baking temperature for making PI layer using glass substrate. Also, EO characteristics of the TN-LCD with a rubbed PI surface based on polymer are almost the same as that of the TN-LCD with a rubbed PI surface based on glass. However, the transmittances of the TN-LCD with a rubbed PI surface based on polymer is less than that with a rubbed PI surface based on glass.