| 摘要 |
PURPOSE:To obtain a magnetic disk having high resolving power and satisfactory overwriting characteristics by forming magnetic layers whose coercive force is increased toward the center of a disk. CONSTITUTION:An Al disk as a disk substrate is degreased, pickled, zincated, and plated with an Ni-P alloy to 20mum thickness, and it is lapped and immersed in a plating bath. The plating bath is prepd. by adjusting an aqueous soln. contg. CoSO4, NiSO4, sodium hypophosphite, sodium malate, sodium tartrate, (NH4)2SO4 and boric acid to 9.0pH with an NaOH soln. The substrate is rotated at 150r.p.m. in the plating bath at 70 deg.C with a plating jig having 5-200r.p.m. variable speed, and the substrate is plated to obtain a magnetic disk having magnetic films each having 580Angstrom thickness and 750Oe coercive force at the inner part and 750Angstrom thickness and 650Oe coercive force at the outer part by making use of a change in plating speed due to the difference in relative speed between the plating soln. and the substrate to be plated. The change in plating speed is characteristic of electroless magnetic plating. The resulting magnetic disk has high resolving power, satisfactory overwriting characteristics and uniform output characteristics at the inner and outer parts. |
