Method of manufacturing glass substrate for use as information recording medium

Abstract

A glass substrate for use as an information recording medium has an average surface roughness (Ra) in the range of 0.3 nm≦Ra<3.0 nm and includes surface irregularities shaped and distributed isotropically and arranged substantially in succession. The surface irregularities include 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 μm×50 μm. A porous region produced by an acid treatment process in the glass substrate would be completely removed if excessively etched by an alkaline solution. However, the etching process using the alkaline solution can be stopped at a stage where the pores in the porous region are enlarged by controlling conditions for the acid and alkali treatment processes.

Dependencies are inferred from the claim text.