| abstract |
The present invention relates to a modifier for a cellulose ester resin which can lower the retardation value (Rth) in the film thickness direction, impart moisture resistance, obtain a film having little change in Rth value with respect to humidity change, a cellulose ester (1) or (2), and a protective film for a polarizing plate, (Wherein R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, n is an integer of 1 to 10, and m is an integer of 1 to 8) , A cellulose ester optical film containing the modifier and a cellulose ester resin, a resin solution obtained by dissolving the modifier and a cellulose ester resin in an organic solvent is poured on a metal support, And then the organic solvent is distilled off and dried to obtain a protective film for a polarizing plate. |