Patent ID: 7470384

Claim:
A method of producing a cellulose ester film having a front layer, an intermediate layer and a rear layer by using a dope solution, said front, intermediate, and rear layers being respectively formed of first, second and third solutions which construct said dope solution, said method comprising a step of: doping said dope solution from a die having a slit on a supporter, in said dope solution a solid content density of each of said first and third solutions being lower than that of said second solution, and satisfying a condition that A/B is under 0.9, wherein A and B are a shearing viscosity of said first solution or said third solution and a shearing viscosity of said second solution respectively, wherein when said dope solution is doped as a dope ribbon from said die, a total thickness of edges of said front layer and said rear layer is more than 5% of a total thickness of said dope ribbon; and feeding a mixture solvent from both sides of a slit of said die, said mixture solvent containing a good solution and a bad solution to solutes in said dope solution.