Relationship between pretilt angle of nematic liquid crystal and surface structure of alignment layer

Abstract

Fabrication method of alignment layer was investigated to Verify which mechanism is dominant in generating the pretilt angle of LC. The surface energy and the geometrical surface structure were systematically controlled by combining the rubbing and Langmuir-Blodgett(LB) methods. Two layers of LB film were deposited on the top of rubbed polyimide films to remove the surface energy generated by rubbing. In a rubbed polyimide film, polymer chains array in a certain angle which increase with the rubbing strength. The rubbed film with two LB layer showed the contact angle to be the same as the LB film, while the pretilt angle of LB layer on rubbed film was reduced. Therefore it is concluded that the pretilt is more affected by the surface structure of the polyimide alignment layer than the surface energy.