Optical characterization of discotic liquid crystalline films

We studied the distribution of optic axis and alignment of discotic molecules in discotic films with one free surface. The nematic structure of the films was fixed by photo-polymerization of discotic monomers. The distribution of optic axis within the films was studied using a null ellipsometry technique. We found that most alignment layers provide flat adhesion of the molecular discs yielding splay or homeotropic alignment of the optic axis within the film depending on the anchoring energy and concentration of polymerization agents. Two chemically modified polyimides were Found to provide planar orientation of the optic axis and the molecular discs adhered with their edges to the substrate. The films can be used as optical compensation layers in liquid crystal displays.