Patent ID: 7238384
Filing Date: 2007-07-03
Classification: G11B

Abstract:
1. A method for producing a substrate for a perpendicular magnetic recording hard disk medium, comprising steps of: a) carrying out under-plating to form an under-plated layer comprising one or more metals selected from a group consisting of Ni, Cu and Ag on an Si single crystal substrate having a diameter of 65 mm or less, a thickness of 1 mm or less and an average surface roughness (Rms) of 1 nm or more and 1000 nm or less; b) forming a plated soft magnetic layer having coercivity of 20 Oe(oersteds) or less and a saturation magnetization of 1T or more on said under-plated layer; and c) polishing said plated soft magnetic layer so as to have an average surface roughness (Rms) of 0.1 nm or more and 5 nm or less, wherein said under-plated layer of step a) and said soft magnetic layer of step b) are formed by a wet process, and wherein either step a) for carrying out the under-plating or step b) for forming said plated, soft magnetic layer comprises electroless plating.