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AssigneeHoya Corporation
InventorsShinji Eda, Hideki Isono, Takashi Maeda, Hiroshi Tsuchiya, Yoshinori Marumo
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Provided are a magnetic disk substrate and a method of manufacturing the same, wherein the magnetic disk substrate has very few defects present on its surface with an arithmetic mean roughness (Ra) at a level in the vicinity of 0.1 nm and thus is suitable as a substrate for a magnetic disk with high recording density. The magnetic disk glass substrate is such that the arithmetic mean roughness (Ra) of the main surface of the glass substrate measured using an atomic force microscope with a resolution of 256×256 pixels in a 2 μm×2 μm square is 0.12 nm or less and the number of defects detected to have a size of 0.1 μm to 0.6 μm in plan view and a depth of 0.5 nm to 2 nm is less than 10 per 24 cm2, wherein the defects are each detected using a shift in wavelength between incident light and reflected light upon irradiating and scanning helium neon laser light with a wavelength of 632 nm on the main surface of the glass substrate.
A magnetic disk glass substrate, wherein an arithmetic mean roughness (Ra) of a polished main surface of the glass substrate measured using an atomic force microscope with a resolution of 256×256 pixels in a 2 μm×2 μm square is 0.12 nm or less and, among defects detected to have a size of 0.1 μm or more and 0.3 μm or less upon irradiating light with a wavelength of 405 nm onto the glass substrate with a spot size of 5 μm and detecting scattered light from the glass substrate, the number of the defects fixed to the glass substrate, whose position on the glass substrate is not changed before and after the glass substrate is immersed for 200 seconds in the dilute sulfuric acid solution adjusted to pH4, is 1 or less per 24 cm2,
A magnetic disk glass substrate, wherein an arithmetic mean roughness (Ra) of a polished main surface of the glass substrate measured using an atomic force microscope with a resolution of 256×256 pixels in a 2 μm×2 μm square is 0.12 nm or less and the number of concave defects detected to have a size of 0.1 μm or more and 0.6 μm or less in plan view and a depth of 0.5 nm or more and 2 nm or less is less than 10 per 24 cm2, the defects each being detected using a shift in wavelength between incident light and reflected light upon irradiating and scanning helium neon laser light with a wavelength of 632 nm on the main surface of the glass substrate,
Dependencies are inferred from the claim text.