| 摘要 |
PROBLEM TO BE SOLVED: To produce a polyester film for a magnetic recording medium suitable for use in the production of a tape for mass data storage having a low error rate. SOLUTION: An aqueous solution containing a water-soluble polymer and fine particles having 5-50 nm average particle diameter as essential components is applied to the surface A of a polyester film melt-extruded, cooled and drawn in one direction at 3-1,000 mg/m2 solid concentration. The polyester film is drawn in a direction perpendicular to the above drawing direction after or while drying the aqueous solution and then the film is heat-treated to produce the objective polyester film for a magnetic recording medium with the surface A side as a ferromagnetic metallic thin film forming face. When the average particle diameter of the fine particles is represented by d (nm), the thickness of a solid material formed by applying the aqueous solution by t (mn) and the draw ratio in the perpendicular direction by s (times), the relation of d/2<=2t/s<d is satisfied.
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