Patent ID: 6332338
Filing Date: 2001-12-25
Classification: C03C,G11B

Abstract:
A process for the production of a glass substrate having the form of a disc for an information recording medium by press shaping with a mold having at least an upper mold member and a lower mold member, which process comprises preparing glass materials to obtain a glass which contains 0.1 to 30 mol % of TiO.sub.2, 1 to 45 mol % of CaO, 5 to 40 mol % of total of MgO and the above CaO, 3 to 30 mol % of total of Na.sub.2 O and Li.sub.2 O, 0 to 15 mol % of Al.sub.2 O.sub.3 and 35 to 65 mol % of SiO.sub.2 and has properties of a liquidus temperature of 1,360.degree. C. or lower and a viscosity of at least 10 poise in a shaping-allowable temperature range, melting said glass materials to obtain a molten glass while temperature-controlling the molten glass to prevent devitrification, then feeding the molten glass through a feed port into said mold and directly press-shaping the molten glass with the mold.