Patent Number: 6,332,338

Title: Method of producing glass substrate for information recording medium

Abstract: Disclosed is a process for producing a glass substrate for an information recording medium by press-shaping a molten glass which gives a glass containing 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 having 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, or by preparing a preform formed of 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 shaping the preform in the form of a disc by a re-heat pressing method. According to the above process, there can be mass-produced, with high productivity, high-quality glass substrates to be used for information recording media such as a magnetic disc, an optical disc, a magneto-optic disc, and the like.

Inventors: Hashimoto; Kazuaki (Tokyo, JP), Zou; Xuelu (Tokyo, JP)

Assignee: Hoya Corporation

International Classification: C03C 3/076 (20060101); C03C 3/087 (20060101); C03C 3/095 (20060101); C03C 3/078 (20060101); G11B 5/73 (20060101); G11B 5/84 (20060101); G11B 5/62 (20060101); C03B 011/16 ()

Expiration Date: 12/25/2018