Glass substrate for magnetic recording medium, magnetic recording medium, and method of manufacturing the same

#This invention relates to a glass substrate for use in a magnetic recording medium, such as, a hard disk, a magnetic recording medium having the glass substrate, and a method of manufacturing the magnetic recording medium and the glass substrate.

#An interface between a magnetic head and a magnetic disk has become a key technology for improving recording capacity in a technical field for magnetically recording (writing) and reproducing (reading).

#It is necessary to excessively reduce a flying height of the magnetic head which is float over a surface of the magnetic disk to improve recording density.

#FIG. 1 is a schematic cross sectional view showing projections in a conventional glass substrate for a magnetic disk;

#FIG. 2 is a schematic cross sectional view showing projections in a glass substrate for a magnetic disk according to an embodiment of this invention; and

#FIG. 3 is a schematic view showing a magnetic disk according to an embodiment of this invention.

#As illustrated in FIG. 1, a seed layer 2, an underlying layer 3, a magnetic layer 4, a protection (protective) layer 5 and a lubricant layer 6 are successively formed on a glass substrate 1 in a magnetic disk according to this embodiment.

#The glass substrate 1 is an aluminosilicate glass which has composition of 63.5 weight % of SiO2, 14.2 weight % of Al2O3, 10.4 weight % of Na2O, 5.4 weight % of Li2O and 6.0 weight % of ZrO2 ,0.4 weight % of Sb2O3, and 0.1 weight % of As2O3, and is processed to the disk shape having outer diameter (65 mm φ),hole diameter(20 mm φ) of a central portion and a thickness of 0.635 nm.

#After the both principle surfaces, end surfaces and chamfered portions are precisely polished, are thermally processed by dipping into heated solvent (specifically, sulfuric acid), and are processed the surfaces by the use of hydrosilicofluoric acid.