| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyester film which is made productively, possesses only a small amount of foreign materials mainly consisting of oligomers extracted on the surface after the film is made, excels in an electromagnetic conversion property and creates only a limited amount of dropout especially when it is converted to a magnetic recording media coated with a thin metal by vacuum metallizing. SOLUTION: One of surfaces of a layer A made of a polyester of which intrinsic viscosity is equal to or larger than 0.55 is coated with a continuous membrane C containing inactive particles C of 0.5-30 wt.% of which an average diameter is 10-50 nm and a volumetric shape coefficient is 0.1-π/6. A surface roughness Wra of the surface of the membrane C side of the film is 0.1-4 nm. A number of foreign materials extracted on the surface of the membrane C side of the film is equal to or smaller than 1,000 pieces/mm2 after the film is treated at 120 deg.C for 30 minutes.
|
