| 摘要 |
PURPOSE:To obtain a polyester film for a magnetic recording medium having superior electromagnetic transducing characteristics and traveling performance by adding a prescribed finely powered titanic acid compound to a specified polyester. CONSTITUTION:A film is formed by chiefly using a composition prepd. by adding 0.05-20wt% finely powdered MTiO3 of 0.03-2.5mum average particle size to polyester consisting essentially of structural units represented by the formula. In the compound, M is at least one kind of group IIA element. The film has >=350kg/mm<2> Young's modulus in the longitudinal direction and 0.5-10% coefft. of thermal shrinkage at 150 deg.C. In case where M is Sr, Ca or Mg, the electromagnetic transducing characteristics are further improved. In case where the melt viscosity of the film is 500-8,000P, especially 1,000-7,000P, the traveling performance is further improved. In case where the film has 35-70Angstrom , especially 40-60Angstrom grain size and 0.935-0.975 refractive index in the thickness direction, the electromagnetic transducing characteristics are further improved. |
