To provide the surface roughness of a specific range, by impregnating a fiber base material of nonwoven fabric with a polyurethane resin, and solidifying the same in wet to obtain the hardness of a specific range.
A substrate 1 is placed between a polishing pad 3 fixed to an upper surface plate made of cast iron, and a polishing pad 4 fixed to a lower surface plate with the proper pressure in a double face polishing machine, and the polishing fluid containing a polishing agent 5 is supplied between the polishing pads 3, 4 and the substrate 1, to perform the polishing by rotating and sliding the polishing pads 3, 4. On this occasion, the polishing pads 3, 4 which are prepared by impregnating the fiber base material of nonwoven fabric with a polyurethane resin, and solidifying the same in wet, and has 75-85 of hardness by a hardness test (A-type) stipulated by JIS K6301, are pasted to the upper and lower surface plates. Whereby the surface roughness of the substrate for a magnetic recording medium can be finished within a specific range constantly.
KONDO MASAO
KUSANO TATSUICHI
SAGAMI OPT KK