| 摘要 |
PURPOSE:To improve mechanical strength, improve electromagnetic conversion characteristics, stabilize running characteristic, improve head contact and further make the medium thinner for long time use by varying the Young's modulus of polyeser base substrate in the width and length directions. CONSTITUTION:Linear polyethylene terephthalate having been melted is extruded from a die slit at 270 to 315 deg.C and is cooled and hardened in a cooling drum of 60 to 80 deg.C. This is then suitably oriented in the longitudinal and width direction at 80 to 120 deg.C by the similar manner as with ordinary orienting method and is next heat set at 140 to 250 deg.C, after which it is taken up. In this way, the orienting of the polyester base substrate is so controlled that the Yound's modulus LDE in its length direction becomes 350 kg/mm<2> or over, the Yound's modulus TDE in the width direction 500 kg/mm<2> or over and its Young's modulus ratio LED/TDE 0.5 to 0.9, and further the thickness of the substrate 6 to 14mu. |
