Zigzag defect-free alignment of surface stabilized ferroelectric liquid crystal cells with a polyimide irradiated by polarized UV light

Zigzag defect-free surface stabilized ferroelectric liquid crystal (SSFLC) cells were prepared using a photodegradable polyimide (PI) having a cyclobu tane ring in the backbone. The PI layers were irradiated by polarized ultra violet light (PUVL) at normal incidence to the surface, and characterized b y UV and FTIR spectroscopy. The anisotropy originates from preferential cle avage of PI chains oriented parallel to the polarization direction of the i rradiating PUVL. After the polarized UV light irradiation, the PI surface w as much flatter than that after rubbing, but it induced a similar order par ameter of dye-doped nematic LC molecules to that for a rubbed cell. Alignme nt of both the FLC molecules and the layer structure is important in SSFLC. After 40 min irradiation, the FLC molecules were well aligned homogeneousl y, and the FLC cells showed a uniform texture without zigzag defects which also indicates a well aligned layer structure. Zigzag defect-free alignment may result from the flatter surface, the much smaller and more constant pr etilt angles, and the bigger cone angle than those achieved by rubbing.