Method for producing magnetic disk, and glass substrate for information recording medium

摘要

To provide a method for producing a magnetic disk, whereby a magnetic recording layer is formed at a high temperature. A method for producing a magnetic disk, which comprises a step of forming a magnetic recording layer on a glass substrate having a temperature of at least 550° C., wherein the glass substrate comprises, as represented by mol percentage, from 62 to 74% of SiO2, from 6 to 18% of Al2O3, from 2 to 15% of B2O3 and from 8 to 21%, in total, of at least one component selected from MgO, CaO, SrO and BaO, provided that the total content of the above seven components is at least 95%, and further contains less than 1%, in total, of at least one component selected from Li2O, Na2O and K2O, or contains none of these three components.

主权项

1. A method for producing a magnetic disk, the method comprising:
(a) preparing glass comprising, by mol percent:
from 62 to 74% of SiO2;from 6 to 18% of Al2O3;from 2 to 15% of B2O3;from 8 to 21%, in total, of at least one component selected from the group consisting of MgO, CaO, SrO, and BaO; andfrom 0 to less than 1%, in total, of at least one component selected from the group consisting of Li2O, Na2O, and K2O,wherein a total content of SiO2, Al2O3, B2O3, MgO, CaO, SrO, and BaO is at least 95%, (b) forming a glass substrate from the glass, cooling the glass substrate to room temperature, and polishing the surface of the glass substrate, wherein surface roughness Ra after polishing the glass substrate is at most 0.15 nm and an acid resistance index is at most 0.1 mg/cm2, wherein a cracking rate p of the polished glass substrate is at most 10%, wherein the cracking rate p is measured after the polished glass substrate is heated at a temperature of at least 550° C. and then cooled to room temperature, (c) forming a magnetic recording layer on the polished glass substrate by adjusting a temperature of the glass substrate to be at least 550° C., which is a temperature of the magnetic recording layer upon forming, thereby forming the magnetic disk, and then cooling the magnetic disk to room temperature, wherein the formed magnetic disk has an impact resistance index S150 of at least 9.2 and S175 of at least 5.2.