| 摘要 |
PURPOSE:To enable formation of a two-layered structure of a magnetic material and improvement in recording density by incorporating a metal or metallic compd. having high magnetic permeability into a resin which is a substrate material. CONSTITUTION:A disc substrate 1 is formed by incorporating 10-30%(mol) a high permeability metal or metallic compd. 3 such as ''Permalloy'' green compact or ''Sendust'' powder, etc. into a raw material 2 formed by dissolving pellets of a thermoplastic resin such as polyether imide or the like in a solvent and extrusion-molding the mixture into a form of sheet, then cutting the sheet in a form of disc by press blanking, etc. and finishing ultrasonically the surface. The metallic material is contained in the disc substrate and therefore the formation of an underlying film by a plating method is made possible in the case of forming the underlying film on the disc substrate 1. Since the mechanical strength and magnetic characteristic are improved, the disc substrate suitable for high density recording is obtd.
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