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AssigneeHoya Corporation
InventorsTakamasa Yoshikawa, Koichi Suzuki
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In a first polishing step, or in a first half of a super precision polishing, a surface of a glass substrate is polished with a first suspension. The first suspension contains particles and a dispersion agent in which the particles are dispersed. The main ingredient of the particles is silicon dioxide (SiO2), and the average size (D50) of the particles is equal to or less than 100 nm. The dispersion medium comprises an acid solution the pH of which is equal to or less than 4. In a second polishing step, or in a latter half of the super precision polishing, the surface of the glass substrate is continuously polished with a second suspension. The second suspension contains particles and a dispersion agent in which the particles are dispersed. The main ingredient of the particles is silicon dioxide (SiO2), and the average size (D50) of the particles is equal to or less than 100 nm. The dispersion medium comprises an alkaline solution the pH of which is equal to or more than 8.5.
A method for polishing a surface of a glass substrate for a data recording medium, the method including a rough polishing step, a precision polishing step, and a super precision polishing step, the super precision polishing step comprising:
A glass substrate for a data recording medium, wherein the roughness average (Ra) of a surface of the glass substrate is equal to or less than 0.4 nm, and wherein the maximum profile peak height (Rp) of the surface is equal to or less than 2 nm.
Dependencies are inferred from the claim text.