| abstract |
Polyester film prepared from a polyester produced by using a germanium compound as a polymerization catalyst and having a Young's modulus in the longitudinal direction, EMD, and a Young's modulus in the transverse direction, ETD, satisfying the following conditions: EMD 350 kg/mm2, ETD 350 kg/mm2, EMD x ETD 250000 kg2/mm4; having a refractive index in the thickness direction, nZD, satisfying the following condition: 1.480 nZD 1.492 and having a maximum roughness, Rt, of at least one side surface satisfying the following condition: Rt 100 nm, is useful as a base film for a magnetic recording medium. A laminate composed of polyester layer A and polyester layer B may be prepared, which have EMD, ETD and nZD satisfying the above-described conditions, which contains fine particles in layer B, and which have an outer surface of said layer A with Rt 100 nm and an outer surface of said layer B with 30 Rt 150 nm. A thin-film ferromagnetic metal magnetic recording medium prepared from this polyester film shows good workability and less drop-out, undergoes markedly reduced marring in contact with a magnetic head, and does not damage a magnetic head. |