We have investigated a phase separation process induced by a photo-polymerization in the homogeneous solution which is composed of the UV-curable monomer-mixture and 5CB as liquid crystal. The phase diagram is obtained by the microscopic observation with using crossed polarizer and phase difference, It is turned out that the phase separation temperature can be distinguished from the Nematic-Isotropic transition temperature. We have confirmed the experimental results that critical points on the phase separation curve are shifted upward at right-hand side during UV-light exposure. In the phase separation process, the periodicity in the structure of the polymer/LC composite films is depended on the phase diagram. The periodicity occurred by spinodal decomposition is observed less than 75mol% due to the existence of single peak in the light scattering profiles.
