Glass for information recording medium substrate, glass substrate for information recording medium and magnetic disk

Abstract

To provide glass for an information recording medium substrate, which is excellent in the acid resistance and weather resistance. Glass for an information recording medium substrate, which comprises, as represented by mol % based on the following oxides, from 61 to 72% of SiO2, from 3 to 12% of Al2O3, from 0 to 14.3 of Li2O, from 0 to 22% of Na2O, from 0 to 22% of K2O, from 4 to 13% of MgO, from 0 to 6% of TiO2 and from 0 to 5% of ZrO2, provided that the total content of Li2O, Na2O and K2O (R2O) is from 8 to 22%, the ratio of the content of Li2O to R2O (Li2O / R2O) is at most 0.52, the ratio of the content of Na2O to R2O (Na2O / R2O) is at least 0.35, or the ratio of the content of K2O to R2O (K2O / R2O) is at least 0.45.

Description

Technical field [0001] The present invention relates to glass used for information recording medium substrates such as magnetic disks (hard disks), glass substrates for information recording media, and magnetic disks. Background technique [0002] Glass substrates are widely used as substrates for information recording media, especially magnetic disks. There is known a commercially available glass substrate whose composition in mol% includes: 65.4% SiO 2 , 8.6% Al 2 O 3 , 12.5% ​​Li 2 O, 10.5% Na 2 O and 3.0% ZrO 2 . The glass available is chemically strengthened for use. [0003] On the other hand, Patent Document 1 proposes a magnetic disk substrate glass that has not been chemically strengthened. [0004] Patent document 1: JP-A-2002-358626 (Tables 1 to 14) [0005] A low pH acid is used in the polishing or washing process of the glass substrate for magnetic disks. Therefore, the glass substrate for magnetic disks is required to be acid-resistant in order not to c...

AI Technical Summary

Problems solved by technology

However, there are problems in that chemical strengthening treatment increases the number of manufacturing steps, leading to an increase in cost, and the surface of the substrate is easily contaminated by chemical strengthening treatment

Due to the above phenomenon, non-uniform defects such as streaks are generated, which deteriorates the quality of the glass, and there are also problems that volatilized materials are condensed on the refractories used in the glass melting furnace, so that the strength of the refractories is greatly reduced, and the volatile substances The recycling of

Therefore, surface roughness is likely to result in polishing or washing processes at low pH conditions, resulting in poor quality

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