Method of manufacturing a glass substrate for a magnetic disk, glass substrate for a magnetic disk, method of manufacturing a magnetic disk, and magnetic disk
AssigneesHoya Corporation, Hoya Glass Disk (Thailand) Ltd.
InventorsKenichi Nishimori, Tadashi Tomonaga
Life of this patent
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Abstract
Provided is a method of manufacturing a magnetic disk glass substrate, wherein, in a main surface polishing process, main surface polishing is applied to one of main surfaces of a glass substrate so that the one main surface has a predetermined arithmetic mean roughness, and main surface polishing is applied to the other main surface of the glass substrate so that the other main surface has a roughness which is higher than the arithmetic mean roughness (Ra) of the one main surface and which is low enough to prevent a component forming the magnetic disk glass substrate from being eluted from the other main surface.
Claims7
A method of manufacturing a magnetic disk glass substrate for use in manufacturing a magnetic disk, comprising:
- a main surface polishing step of polishing a glass substrate having a pair of main surfaces,
- wherein, the main surface polishing step comprises (1) main surface polishing one of the main surfaces of the glass substrate so that the one main surface has an arithmetic mean roughness (Ra) required for magnetic recording, and (2) main surface polishing the other main surface of the glass substrate so that the other main surface has a roughness which is higher than the arithmetic mean roughness (Ra) of the one main surface and which is low enough to prevent elution of a component forming the magnetic disk glass substrate and which is not required for the magnetic recording,
- wherein the arithmetic mean roughness (Ra) of the one main surface is 0.30 nm or less while the roughness of the other main surface falls within a range of 1.5 nm to 5 nm, and
- wherein the magnetic disk has only on the one main surface a magnetic recording layer.
A method of manufacturing a magnetic disk comprising a magnetic disk glass substrate and at least a magnetic recording layer formed on the magnetic disk glass substrate,
- wherein the magnetic disk glass substrate has a pair of polished main surfaces, one of the main surfaces has an arithmetic mean roughness (Ra) required for magnetic recording,
- the other main surface has a roughness which is higher than the arithmetic mean roughness (Ra) of the one main surface and which is low enough to prevent elution of a component forming the magnetic disk glass substrate and which is not required for the magnetic recording,
- at least the magnetic recording layer is formed only on the one of the main surfaces, and
- the arithmetic mean roughness (Ra) of the one main surface comprising the magnetic recording layer is 0.30 nm or less while the roughness of the other main surface comprising no magnetic recording layer falls within a range of 1.5 nm to 5 nm.
A method of manufacturing a magnetic disk comprising a magnetic disk glass substrate obtained through a main surface polishing step of polishing a glass substrate having a pair of main surfaces and at least a magnetic recording layer formed on the magnetic disk substrate, the method comprising:
- forming at least the magnetic recording layer on only one of the main surfaces, and
- forming, on the other main surface, a substrate forming component elution preventing layer adapted to prevent a component forming the magnetic disk glass substrate from being eluted from the other main surface,
- wherein the substrate forming component elution preventing layer has a thickness of 4 nm or more,
- an arithmetic mean roughness (Ra) of one main surface comprising the magnetic recording layer is 0.30 nm or less while the roughness of the other main surface comprising no magnetic recording layer falls within a range of 1.5 nm to 6 nm, and
- the substrate forming component elution preventing layer is made of a film of titanium alone or a titanium alloy.
Dependencies are inferred from the claim text.