To provide reduction of weight, reduction of the electric power consumption of a disk drive device, improvement of durability and SN ratio and increase of adhesive power between a substrate and magnetic coated film by using a resin substrate having high rigidity and heat resistance and subjected to an oxygen plasma treatment for the substrate and using an electron radiation curing resin as a binder for the magnetic coated film. The surface of the resin substrate having high rigidity and heat resistance is subjected to a physicochemical surface treatment by the oxygen plasma generated by executing glow discharge in an oxygen atmosphere in the stage of subjecting the resin substrate having high rigidity and heat resistance to the plasma treatment in oxygen to activate the surface thereof. The coated film consisting of an epoxy acrylate or epoxy methacrylate which is the electron radiation curing resin to be used as the binder for the magnetic layer is extremely hard and has excellent polishing property as well. Ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder and hexagonal ferrite particles, etc. are used for the ferromagnetic powder. The respective components are dissolved in a solvent to prepare a magnetic coating compd. which is then coated in the substrate having the high rigidity and heat resistance. The coating is cured by the irradiation of electron rays thereon. |