Patent ID: 9023421
Filing Date: 2015-05-05
Classification: C03C,G11B

Abstract:
1. A method for producing a magnetic disk, the method comprising: (a) preparing glass comprising, by mol percent: (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/cm 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 S