| 摘要 |
<p>There is provided a polyester film useful for production of a magnetic recording medium excellent in runnability, electromagnetic conversion characteristics and storage stability. In the polyester film, a continuous thin film which contains a resin as a matrix and acts as a primer layer for a magnetic layer is coated on one surface of a support film composed of a polyester. According to one embodiment thereof, the surface of the continuous thin film has (A) small protuberances each containing particles with an average particle size of less than 0.06 micrometer as a nucleus and having a height of 13 nm or less, (B) large protuberances each containing particles with an average particle size of 0.06 micrometer or more as a nucleus and having a height of 30 nm or less, and (C) micro-protuberances composed of a matrix resin alone, the numbers, per mm<2> of the film, of these protuberances satisfying the formulas, An = 1.0 x 10<4> - 1.0 x 10<8>/mm<2>, Bn = 0 - 4 x 10<4>/mm<2>, and Cn </= 4.0 x 10<6>/mm<2> wherein An is the number of the small protuberances, Bn is the number of the large protuberances, and Cn is the number of the micro-protuberances, the fine surface roughness Ra<s> of the continuous thin film portion composed of the matrix resin alone being 1.10 nm or less, and the surface roughness Ra of the overall continuous thin film being 1 to 10 nm.</p> |
