Novel Method of Obtaining Pretilt Angle in Liquid Crystal Alignment with Polyimide Langmuir-Blodgett Films

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Abstract
A new surface modification technique to obtain pretilt angle in Liquid Crystal alignment with polyimide (PI) Langmuir-Blodgett (LB) films is proposed. We modified the surface prior to the LB film deposition by depositing a thin layer of Silicon Monoxide ( SiO x ) by oblique evaporation. Liquid Crystal Display cells prepared by this method gave no tilt disclinations upon an application of an electric field and were very stable with time. Preliminary results show that two PI-LB films are enough to align liquid crystal molecules with pretilt angles up to 9.1° along the dipping direction. It was found that the dipping direction of the LB films is very important in obtaining the observed pretilt angles.