Optical characterization of discotic liquid crystalline films

We studied the distribution of optic axis and alignment of discotic molecul es in discotic films with one free surface. The nematic structure of the fi lms was fixed by photo-polymerization of discotic monomers. The distributio n of optic axis within the films was studied using a null ellipsometry tech nique. We found that most alignment layers provide flat adhesion of the mol ecular discs yielding splay or homeotropic alignment of the optic axis with in the film depending on the anchoring energy and concentration of polymeri zation agents. Two chemically modified polyimides were Found to provide pla nar orientation of the optic axis and the molecular discs adhered with thei r edges to the substrate. The films can be used as optical compensation lay ers in liquid crystal displays.