Our findings indicate that the frost‐formation phenomenon common to many photoconductor‐thermoplastic devices can be attributed to spinodal decomposition processes. This decomposition is induced by the inherent electrical field of about 106V/cm in the plasticized and polydispersed thermoplastic melts. By using monocomponent polystyrene of sharply defined molecular weight distribution for the thermoplastic layer the frost formation is suppressed, so that holograms having high signal‐to‐noise ratio can be readily recorded.