| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical film of which the retardation in the in-plane direction Re and the retardation in the thickness direction Rth are small, and of which the property of the film surface is excellent, and to provide a production method of the optical film with high productivity.SOLUTION: A production method of an optical film includes: a molding step of a molten resin film, in which a thermoplastic resin having glass transition temperature of Tg is extruded from a die 112 in a heated molten state so as continuously to mold the molten resin film; and a cooling step 200 to cool the molten resin film, in which the molten resin film is continuously guided to a rotating casting drum 130 and the molten resin film is transported along a transportation route on a peripheral surface of the casting drum 130 by rotation of the casting drum 130, in which V, Tp and Tg satisfy specified formula when the circumferential speed of the surface of the casting drum 130 is indicated with V, the surface temperature of the molten resin film at the arrival time of the molten resin film discharged from the die 112 to the surface of the casting drum 130 is indicated with Tp.SELECTED DRAWING: Figure 1 |
