Stock material or miscellaneous articles – Circular sheet or circular blank – Recording medium or carrier
Patent
1997-09-04
2000-05-16
Resan, Stevan A.
Stock material or miscellaneous articles
Circular sheet or circular blank
Recording medium or carrier
428426, 428432, 428694ST, 428900, 427129, 427130, G11B 582
Patent
active
060634707
ABSTRACT:
A material according to the invention is made of a glass whose transition temperature is 750 degrees Celsius or greater and used for a substrate for information recording media, and for example, the glass has an essential component made of any group chosen from SiO.sub.2 --Al.sub.2 O.sub.3 --MgO--CaO, SiO.sub.2 --Al.sub.2 O.sub.3 --MgO--Y.sub.2 O.sub.3, SiO.sub.2 --Al.sub.2 O.sub.3 --CaO--Y.sub.2 O.sub.3, SiO.sub.2 --Al.sub.2 O.sub.3 --MgO--CaO--Y.sub.2 O.sub.3, and SiO.sub.2 --Al.sub.2 O.sub.3 --M.sub.2 O.sub.3 (wherein M denotes a trivalent metal.). This material can form a substrate for information recording media, or more specifically, a substrate on which at least a magnetic layer is formed to constitute a magnetic disc. A manufacturing method for magnetic disc according to the invention includes a process to improve a coercive force of a magnetic layer by thermally treating the magnetic layer at a temperature at least 40 degrees Celsius below the transition temperature of the material forming the substrate for the magnetic disc, where at least the magnetic layer is formed on the substrate made of the above material. The material is suitable for a substrate for information recording media made of the glass having an excellent surface flatness and mechanical strength and property durable against a heat treatment implemented at a high temperature for improving magnetic characteristics of the magnetic layer. This material is applicable to a substrate, a magnetic recording media in use of the substrate, and a manufacturing method for such information recording media.
REFERENCES:
patent: 4820660 (1989-04-01), Mohri et al.
patent: 5391522 (1995-02-01), Goto et al.
patent: 5599754 (1997-02-01), Maeda et al.
patent: 5780371 (1998-07-01), Rifqi et al.
Toratani Hisayoshi
Zou Xuelu
Hoya Corporation
Resan Stevan A.
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