Cellulose acylate film, method for producing same, polarizer and liquid crystal display device

A method for producing a cellulose acylate film, comprising bringing a styrene/maleic anhydride copolymer into contact with an ingredient capable of ring-opening the ring-closed acid anhydride structure moiety in the styrene/maleic anhydride copolymer to obtain a solution of partially ring-opened, styrene/maleic anhydride copolymer,

• mixing the solution with a cellulose acylate resin to obtain a mixed solution comprising the cellulose acylate resin and the partially ring-opened, styrene/maleic anhydride copolymer, and
• casting the mixed solution to form a cellulose acylate film,
• wherein the partially ring-opened, styrene/maleic anhydride copolymer is represented by the following Formula (1):
• wherein m and n each indicate a natural number;
• R1 to R4, R11 to R14, R21 and R22 each independently represent a hydrogen atom or a monovalent substituent and
• wherein at least one of R21 and R22 represents a substituent derived from a polymer compound having a molecular weight of from 500 to 1000.