Glass substrate for information recording medium and method for manufacturing same

A method for manufacturing a glass substrate for an information recording medium, the manufacturing method comprising:na pre-grinding first washing step for washing a surface of a polished disk-shaped glass plate with a strong acid washing liquid, wherein the strong acid washing liquid alters the glass substrate to form an altered surface layer on an inner portion of the glass plate, wherein the strong acid washing liquid decreases a chemical resistance of the altered surface layer;a pre-grinding second washing step for washing the surface with a strong alkaline washing liquid, wherein the strong alkaline washing liquid removes a part of the altered surface layer, wherein a thickness of the altered surface layer is controlled by a washing time of the surface in the strong acid washing liquid and in the strong alkaline washing liquid;subsequent to both the first washing step and the second washing step, a step for grinding the altered surface layer for a depth of 0.5 nm or more with abrasion grains so that the altered surface layer has a thickness of 3 nm or less, wherein the grinding of the altered surface layer forms a texture including projections on the surface of the glass plate;subsequent to the grinding step, a post-grinding washing step for washing the surface with an alkaline washing liquid, wherein the alkaline washing liquid removes a remaining portion of the altered surface layer from the inner portion without affecting the inner portion.

A method for manufacturing a glass substrate for an information recording medium, the manufacturing method comprising:npreparing a disk-shaped glass plate containing silicon oxide, aluminum oxide, and alkaline earth metal oxide with a uniform chemical composition;polishing the glass plate to form a smooth surface;immersing the polished glass plate in a strong acid solution to form an altered surface layer on an inner portion, wherein an ingredient ratio of at least one of aluminum oxide and alkaline earth metal oxide is decreased in the altered surface layer compared to the inner portion;subsequent to immersing the polished glass plate in the strong acid solution, immersing the polished glass plate in a strong alkaline solution, wherein the strong alkaline solution removes a part of the altered surface layer;subsequent to immersing the polished glass plate in the strong acid solution and in the strong alkaline solution, removing at least part of the altered surface layer with an abrasive to such that the altered surface layer has a thickness of 3 nm or less;uniformly etching the altered surface layer having a thickness of 3 nm or less while washing off the abrasive with an alkaline washing liquid wherein the inner portion is unaffected by the alkaline washing liquid.