Generation of Pretilt Angles on Polyimides with a Single Linearly Polarized UV Exposure

We designed polyimide (PI) films containing fluorine atoms for liquid crystal (LC) alignment using linearly polarized UV exposure. Using a single oblique polarized UV exposure we obtained unidirectional LC alignment with any desired pretilt angles from 0 ° up to 90 °. Pretilt angles depend on the concentration of fluorine atoms in PI and the UV exposure time and angle. Dichroic ratio and capacitance measurements of the LC cells suggest that oblique polarized UV exposure breaks the surface order degeneracy of the LC molecules, generating uniform pretilt angle along the optic axis of PI film.