| 摘要 |
PROBLEM TO BE SOLVED: To produce a polymer film which improves productivity and is excellent in planarity. SOLUTION: An addition agent is put into a raw material dope including an organic solvent and a cellulose acylate so as to prepare a dope for an underlying layer, a dope for a support surface layer, and a dope for an air surface layer. Among these, at least two or more kinds are made to have different viscosities. Each dope is cast together from a casting die 89 on a casting band 85 traveling to form a cast sheet 70 of three layers consisting of an underlying layer 120a, an air surface layer 121a facing open air, and a support surface layer 122a. A film thickness t1 of an underlying layer 120a, a film thickness t2 of a support surface layer 122a, and a film thickness t3 of an air surface layer 121a are made to be t2≤t3≤t1. A cast sheet 70 stripped off from a casting band 85 is gripped by a gripping means at both the ends and is dried extending in a width direction. The levelling effectiveness of an air surface layer is improved and a cast sheet is effectively dried, so that a film raising productivity and excellent in planarity is produced. COPYRIGHT: (C)2008,JPO&INPIT |
