A composition for a polarizing plate containing a polymer having a partial structure represented by the following ring structure α or β in the molecule, a polarizing plate protective film, a cellulose acylate film, a polarizer, a polarizing plate, and a display; wherein L1 represents a single bond, —C(═O)—, —C(═S)—, an alkylene group, or an arylene group; and the symbol * designates a boning hand, or a site to which a hydrogen atom, a substituent, or a linking group binds.