Patent ID: 6576353
Filing Date: 2003-06-10
Classification: C03C,G11B,Y10T

Abstract:
A glass substrate for use as an information recording medium comprising an aluminosilicate glass free of ZrO2 and containing SiO2 and Al2O3 having a difference between the molar % of SiO2 and Al2O3 of at most 59.5 molar % said glass substrate having an acid-resistant criterion in terms of an etching rate of at least 16 nm/min. upon contact with hydrofluoric acid at a temperature of 50Â° C. and a concentration of 0.1 weight % said glass substrate having a surface for receiving a magnetic film wherein said surface being first treated with a treating agent containing an acid to selectively dissolve said surface to form fine pores therein followed by treatment of said surface with a treating agent containing an alkali to enlarge said fine pores thereby providing a finely roughened surface comprising irregularities shaped and distributed isotropically and arranged substantially in succession, said irregularities including 5 to 50,000 convexities having a height of at least 3 nm and no convexities having a height of at least 15 nm within an area of 50 &mgr;mÃ—50 &mgr;m and an average surface roughness in the range of 0.3 nm&lE;Ra&lE;3.0 nm.