Glass composition for magnetic disk substrates and magnetic disk substrate
First Claim
1. A glass composition for magnetic disk substrates comprising, expressed in terms of weight percent on the oxide basis:
- from 66 to 80% SiO2,from 5 to 15% Al2 O3,from 3 to 8.5% Li2 O,from 0 to 3% Na2 O,from 0 to 3% K2 O,from 0.5 to 8% TiO2,from 3.5 to 8% ZrO2,from 0.5 to 3% P2 O5,from 0 to 2% Sb2 O3, andfrom 0 to 2% As2 O3,wherein the total of the contents of Li2 O, Na2 O and K2 O is from 3 to 10%, and having a theoretical optical basicity of 0.548 or less.
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Abstract
A glass composition for magnetic disk substrates comprising as oxides: from 66 to 80% by weight of SiO2, from 5 to 15% by weight of Al2 O3, from 3 to 8.5% by weight of Li2 O, from 0 to 3% by weight of Na2 O, from 0 to 3% by weight of K2 O, from 0.5 to 8% by weight of TiO2, from 3.5 to 8% by weight of ZrO2, from 0.5 to 3% by weight of P2 O5, from 0 to 2% by weight of Sb2 O3, and from 0 to 2% by weight of As2 O3, and having a theoretical optical basicity of 0.548 or less; a magnetic disk substrate which is prepared by forming and polishing the above glass composition, followed by chemically strengthening the polished substrate by ion exchange or by forming, heat treating, and polishing the above composition and contains Li2 O·2SiO2 and/or spodumene as the main crystalline phase. The glass composition for magnetic disk substrates can easily be formed, can easily be polished after crystallization of the glass by heat treatment or chemically strengthened by ion exchange of the glass after forming and polishing, and is used for preparing magnetic disk substrates which has excellent chemical durability, mechanical strength, heat resistance, surface flatness, and surface smoothness, and shows little degradation of magnetic film characteristics by alkali migration.
102 Citations
6 Claims
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1. A glass composition for magnetic disk substrates comprising, expressed in terms of weight percent on the oxide basis:
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from 66 to 80% SiO2, from 5 to 15% Al2 O3, from 3 to 8.5% Li2 O, from 0 to 3% Na2 O, from 0 to 3% K2 O, from 0.5 to 8% TiO2, from 3.5 to 8% ZrO2, from 0.5 to 3% P2 O5, from 0 to 2% Sb2 O3, and from 0 to 2% As2 O3, wherein the total of the contents of Li2 O, Na2 O and K2 O is from 3 to 10%, and having a theoretical optical basicity of 0.548 or less. - View Dependent Claims (4)
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2. A glass composition for magnetic disk substrates comprising, expressed in terms of weight percent on the oxide basis:
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from 66 to 75% SiO2, from 5.5 to 10% Al2 O3, from 4 to 8.5% Li2 O, from 0 to 2% Na2 O, from 0 to 2% K2 O, from 2 to 6% TiO2, from 3.8 to 6.5% ZrO2, from 1 to 2.5% P2 O5, from 0 to 2% Sb2 O3, and from 0 to 2% As2 O3, wherein the total of the contents of Li2 O, Na2 O and K2 O is from 4 to 9%, and having a theoretical optical basicity of 0.548 or less. - View Dependent Claims (5)
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3. A glass composition for magnetic disk substrates comprising, expressed in terms of weight percent on the oxide basis:
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from 66 to 75% SiO2, from 5.5 to 7.5% Al2 O3, from 5 to 8.5% Li2 O, from 0 to 2% Na2 O, from 0 to 2% K2 O, from 2 to 4% TiO2, from 4.1 to 6% ZrO2, from 1 to 2.5% P2 O5, from 0 to 1% Sb2 O3, and from 0 to 1% As2 O3, wherein the total of the contents of Li2 O, Na2 O and K2 O is from 5 to 9%, and having a theoretical optical basicity of 0.548 or less. - View Dependent Claims (6)
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Specification
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- Resources
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Current AssigneeYamamura Glass Company Limited
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Original AssigneeYamamura Glass Company Limited
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InventorsKawai, Hideki, Taguchi, Tomoyuki, Kuriyama, Ikuo, Wakabayashi, Hajimu, Ohara, Tohru
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Primary Examiner(s)GROUP, KARL E
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Application NumberUS08/773,260Time in Patent Office337 DaysField of Search501/5, 501/7, 501/63, 501/68US Class Current501/63CPC Class CodesC03C 10/0027 containing SiO2, Al2O3, Li2...C03C 21/002 to perform ion-exchange bet...C03C 3/097 containing phosphorus, niob...G11B 5/73921 Glass or ceramic substrates
