Optical film and process for producing the same

Abstract

An optical film of high planarity that even in the use of an optical film material containing a non-resinous additive in an amount of 5 mass % or more, would exhibit inexpensive satisfactory roll cleaning effects, and that would find application in, especially, various functional films such as a retardation film and a protective film for polarization plate for use in a liquid crystal display apparatus, etc.; and a process for producing the optical film. There is disclosed a process for producing an optical film according to a melting casting film forming method, including extruding a melt of resin blend containing a resin and 5 mass % or more of non-resinous additive through a casting die into a film form, wherein a first roller () for cooling has a temperature of the melting point of the additive to the glass transition temperature (Tg) of the resin blend. Preferably, the first roller () for cooling has a peripheral speed (S) exhibiting a ratio between the same and the peripheral speed (S) of a third roller () for cooling, S/S, of 1.001 to 1.05. Preferably, a filmlike molten blend is pressed against the first roller () for cooling at a linear pressure of 0.5 to 50 N/mm by means of a second roller () for pressure application.