Disc substrates for information recording discs and magnetic discs
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United States of America Patent
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-
Apr 10, 2001
Grant Date -
N/A
app pub date -
Dec 30, 1998
filing date -
Sep 4, 1996
priority date (Note) -
In Force
status (Latency Note)
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Abstract
Disclosed is disc substrate consisting of SiO.sub.2 --Al.sub.2 O.sub.3 --RO (RO=divalent metal) glasses having high specific elastic modulus of 36.times.10.sup.6 Nm/kg or more or high Young's modulus of 110 GPa or more, high transition temperature of 700.degree. C. or higher (high heat resistance), excellent surface smoothness (surface roughness Ra<5 .ANG.) and high strength. The substrates exhibiting high specific elastic modulus or high Young's modulus and high strength enables to realize thinner magnetic discs and prevent breakdown of magnetic discs. Since glass substrates being composed of the glass have excellent heat resistance and flatness, the substrates can be subjected to heat treatment for improvement of magnetic layer characteristics and realize smaller flying height of magnetic head, i.e., higher recording density.
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