| 摘要 |
<p>PURPOSE:To obtain a polyester thin cylindrical molding of an optimum thickness as a carrier for high-density magnetic recording elements, which is excellent in physical properties and adhesion with regenerating head, by specifically designating the intrinsic viscosity of polyester, thickness, surface roughness and degree of orientation of polyester. CONSTITUTION:For polyester thin cylindrical moldings having main repeating unit of ethylene terephthalate, the intrinsic viscosity is designated to 0.5 or more for maintaining of mechanical strength and preventing vertical tear, the thickness is designated to 100mum or less from standpoint of adhesion with head for recording regeneration, and the difference between maximum thickness and minimum thickness of cross section of the molding in parallel with axis is designated to 30mum or less for preventing longitudinal tear. The surface roughness in the circumferential direction of the periphery of the molding is designated to 0.05mum or less from the standpoint of longitudinal tear prevention, and orientation degrees in axial and circumferential directions are designated to 0.03 or more from the standpoint of longitudinal tear resistance and circumferential strength. The cylindrical molding is obtained by a vacuum molding method to push a heated film 5 into the cavity 2 by a plug 1 or a blow molding method.</p> |
