| abstract |
The purpose of the present invention is to provide an optical film having excellent dimensional stability, in particular, a protective film for a polarizer. Provided are the following: a polyester-based modifier composition for a cellulose ester resin, the modifier composition containing a polyester resin obtained by reacting a diol with a dicarboxylic acid, wherein the number average molecular weight (Mn), as measured by gel permeation chromatography (GPC), of the modifier composition is 350-2,000 and the content of polyester resins having molecular weights lower than 350 in the modifier composition is 5 mass % or lower; a cellulose ester optical film that contains the modifier composition and a cellulose ester resin; and a protective film for a polarizing plate, which is obtained by flow casting on a metal support a resin solution which is obtained by dissolving the modifier composition for a cellulose ester resin and a cellulose ester resin in an organic solvent, and then distilling and drying the organic solvent. |