| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyester film roll for a magnetic recording medium which is suitable for manufacturing a ferromagnetic metal thin film type magnetic recording medium with a high quality and excellent productivity. SOLUTION: The polyester film roll is prepared by winding around a cylindrical core a polyester film which comprises a layer A and a layer B being two polyester layers, of which the surface on the layer A side has an arithmetic mean roughness Ra of 1-4 nm and the surface on the layer B side an arithmetic mean roughness Ra of 5-30 nm and which has a width of 600-1,000 mm and a winding length of 20,000-60,000 m. An air inclustion rate of the polyester film roll is 2-10% and a discrepancy in a roll end face is 2 mm or less. COPYRIGHT: (C)2005,JPO&NCIPI |
