| 摘要 |
PURPOSE:To extend the period of magnetic recording and to decrease the distortion and output fluctuation of recording so that recording and reproducing are satisfactorily executed by using a base material film which has the specific relation between the refractive index in the thickness direction and the Young's modulus in the vertical direction and has the surface roughness in a prescribed range. CONSTITUTION:A biaxially oriented polyethylene-2.6-naphthalane dicarboxylate film formed to have, for example 3-7mum film thickness, >=800kg/mm<2> Young's modulus in the vertical direction and to have the relation expressed by formula I between the refrative index etaz in the thickness direction and the Young's modulus YMD in the vertical direction is sued as the base material film. The film is so formed that the surface roughness Ra is in, for example, a 0.012-0.040mum range. The elongation, contraction and deformation of a tape by the tension fluctuation in the start-stop stage are thereby decreased and the distortion and output fluctuation of recording are decreased. The tape run ning property and audio characteristic are improved. The recording and reproduc ing are thus made satisfactorily executable for 120-180min. |
