| 摘要 |
<p>PURPOSE:To obtain the title film excellent in adhesiveness, light-screening property, durability and electromagnetic transduction characteristics, containing carbon black and specified in the transmittance and average surface roughness of film and the height and number or coarse protrusions. CONSTITUTION:A polyester is mixed with 0.05-5wt% carbon black of an average particle diameter of 10-30mm 0-10,000ppm of a dispersant (e.g., polyvinylpyrrolidone) and, optionally, inert inorganic particles (e.g., TiO2) of an average particle diameter of 0.05-5mum and 0-10,000ppm of an organic lubricant (e.g., hexamethylenebisbehenamide). The obtained mixture is molded into a film, which is biaxially oriented to obtain a polyester film for magnetic recording media, which can satisfy the requirements of formulas I-IV (wherein T900 is the transmittance of film at a wavelength of 900nm, Ra is an average surface roughness, n1 is the number, per 25cm<2> film area, of protrusions of a height of 0.81-1.08mum present on the film surface, and n2 is the number, per 25cm<2> film area, of protrusions of a height >=1.08mum.</p> |
