Glass substrate for information recording medium, manufacturing method thereof, and information recording medium
AssigneeNippon Sheet Glass Co., Ltd.
InventorsJunji Kurachi, Akihiro Koyama, Nobuyuki Yamamoto, Yasuhiro Saito, Kazuishi Mitani, Koichi Ataka, Yoshihiro Matsuno
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Abstract
A glass substrate for an information recording medium has an acid resistance represented by an etching rate of at most 45 nm/min. upon contact with a hydrofluoric acid having a temperature of 50° C. and a concentration of 0.1 weight %. The glass substrate has a recording surface having an average surface roughness Ra smaller than 0.3 nm.
Claims6
A manufacturing method of a glass substrate for an information recording medium comprising the steps of:
- melting components for a glass having an etching rate of at most 45 nm/min. upon contact with a hydrofluoric acid having a temperature of 50° C. and a concentration of 0.1 weight %;
- forming said melted components to a desired substrate shape;
- polishing the surface of said substrate with a polishing compound;
- removing the polishing compound which remain attached to the surface of said substrate by cleaning with an acid;
- and
- holding the surface smoothness (average surface roughness) Ra of said substrate in the range of Ra<0.3 nm by cleaning with an alkali.
A manufacturing method of a glass substrate for an information recording medium comprising the steps of:
- melting components for a glass having an etching rate of at most 30 nm/min. upon contact with a hydrofluoric acid having a temperature of 50° C. and a concentration of 6.1 weight %;
- forming said melted components to a desired substrate shape;
- polishing the surface of said substrate with a polishing compound;
- removing the polishing compound which remain attached to the surface of said substrate by cleaning with an acid;
- and
- holding the surface smoothness (average surface roughness) Ra of said substrate in the range of Ra<0.3 nm by cleaning with an alkali.
Dependencies are inferred from the claim text.