Amorphous carbon substrate for magnetic discs

摘要

The surface of a blank for a textured amorphous carbon substrate is polished, and then heated at a predetermined temperature in an oxidizing atmosphere to form minute irregularities in the polished surface through a reaction expressed by C + O2 = CO2 so that the surface is textured in an appropriate surface roughness. A randomly textured amorphous carbon substrate has a randomly textured surface with a surface roughness Ra in the range of 20 to 100 ANGSTROM and the ratio Ra2/Ra1, where Ra1 is the surface roughness with respect to a circumferential direction. and Ra2 is the surface roughness with respect to a radial direction, in the range of 0.75 to 1.25 ANGSTROM . A concentrically textured amorphous carbon substrate has a concentrically textured surface with a surface roughness Ra in the range of 30 to 100 ANGSTROM or in the range of 40 to 200 ANGSTROM , and the ratio Ra2/Ra1 of 1.75 or greater.