METHOD FOR PRODUCING OPTICAL FILM

摘要

A method for producing an optical film of good quality having uniform thickness by which entrainment of bubbles is eliminated at a casting portion even in the case of high-speed film formation without reducing pressure excessively when a film formation rate is increased in a solution casting film forming method, and a stabilized casting dope ribbon can be formed during dope casting. Dope is allowed to flow from a casting die onto a traveling support and a film is formed while pressure at the casting portion of the casting die is reduced by a pressure reducing means installed on the rear side of the casting die in the advancing direction of the support, wherein the temperature of the support during casting is set in a range represented by expression (1). -0.01CS+0.005?P+5=T=-0.125×CS+0.04×?P+17...expression (1). T represents the temperature (°C) of the support during cast, CS represents the moving speed (m/min) of the support, and ?P represents pressure reduction value (Pa) by the pressure reducing means.