FLAT AND READILY SLIPPERY POLYESTER FILM AND PRODUCTION THEREOF

摘要

PURPOSE:A polyester film, obtained by forming a coating film, consisting of a specific composition, e.g. polyurethane, etc., and having many small protrusions on at least one surface of a polyester film, having improved flattness and slipperiness and suitable as a material for magnetic tapes, etc. CONSTITUTION:At least one surface of a polyester film before completing crystal orientation is coated with an aqueous dispersion of a composition containing (A) a polyurethane containing 0.5-15wt% one or more of carboxylate groups, sulfonate groups, etc., (B) an acrylic resin consisting of (B1) 40-80mol% methyl methacrylate component and (B2) 20-60mol% another copolymerizable vinyl monomer, (C) a low-molecular weight polyethylene wax, e.g. polyethylene wax having 1,000-10,000 average molecular weight, and (D) a surface roughening material having =0.5mum average particle diameter at 98/2-40/60 weight ratio of the total of the components (A), (B) and (C) to the component (D), 98/2-40/60 weight ratio of the total of the components (A) and (B) to the component (C) and 90/10-10/90 weight ratio of the components (A) to (B) and dried. The film is then drawn and heat-treated to form a coating film having 0.002-0.01Xm center line average height.