| 摘要 |
PURPOSE:To obtain a polyester film excellent in running performance, running durability at the time of repeated use, winding characteristics like a pancake and slitting characteristics and useful as a base film for a magnetic recording medium satisfying even the requirement of high image quality. CONSTITUTION:This polyester film contains spherical silica particles having 0.1-2.0mum volume average particle diameter and a relative standard deviation of >0.5 in polyester and simultaneously satisfies inequalities DELTAN<1,530-8,754XF, DELTAN>1,413-8,327XF, -20DELTAN <30 and F-5(TD) >12.5, wherein DELTAN=(NMD-NTD)X1,000, F=(NMD+NTD)/2-nz (where NMD is the refractive index of the film in the longitudinal direction, NTD is the refractive index of the film in the transverse direction and nz is the refractive index of the film in the thickness direction) and F-5(TD) is the value (F-5) in the transverse direction of the film. |
