Patent ID: 9539774
Date: 2017-01-10
CPC Classifications: B29C,B29D,B29K,G02B,G02F

Claim:
1. A method for producing a resin film, comprising: a casting step of casting a resin solution containing a transparent resin from a casting die onto a running support to form a cast membrane; and a releasing step of releasing the cast membrane from the support, wherein the casting die includes a manifold portion, a discharge port through which the resin solution is discharged and cast onto the support, and a slit portion between the manifold portion and the discharge port to allow the resin solution to pass from the manifold portion toward the discharge port, in the casting step, a discharge velocity at which the resin solution is discharged from longitudinally opposite ends of a discharge port of the casting die is 0.95 times to 1.5 times a discharge velocity at which the resin solution is discharged from a longitudinally central portion of the discharge port of the casting die, and the slit portion is subjected to a surface treatment which is an ultrachrome plating treatment and the treatment is only at longitudinally opposite ends of the slit portion so that each of the longitudinally opposite ends of the slit portion has a surface energy which is lower than that of a central portion of the slit portion by 10 mN/m to 30 mN/m, thereby setting the discharge velocity at the longitudinally opposite ends of the discharge port to be 0.95 to 1.5 times the discharge velocity in the longitudinally central portion of the discharge port.