| 摘要 |
PURPOSE:To decrease the fluctuation in output owing to a change in humidity, etc. by forming a magnetic layer on a base material for disc formed by using a polyolefin layer or a thermoplastic resin layer contg. a specific proportion of polyolefin as a core and laminating biaxially oriented polyester films on both surfaces. CONSTITUTION:A layer of a homopolymer such as PE, polybutene, polystyrene or the like or a copolymer thereof, etc. or a layer contg. a thermoplastic resin contg. >=50wt% polyolefin, more particularly, thermoplastic polyester, is used as a core layer. biaxially oriented polyester films are laminated on both surfaces of the core layer and such core layer is used as a base material for a magnetic disk. A magnetic layer is formed by a conventional method on the surface of the base material, thereby manufacturing the magnetic disk. The cefft. of expansion by moisture of the base material decreases as the hygroscopicity of the polyolefin is small. The dimensional change rate of the outside diameter owing to expansion of the disk under high humidity is decreased and the excellent disk which is suppressed in the fluctuation in output and drop-out is obtd. |
