POLISHING COMPOSITION FOR MAGNETIC DISK SUBSTRATE

Embodiments of the subject application provide a polishing composition for a magnetic disk substrate, whereby the polishing composition contains colloidal silica, at least one of a phosphorus-containing inorganic acid and an organic acid, and water. According to at least one embodiment, the colloida...

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Format Patent
LanguageEnglish
Published 19.06.2018
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Summary:Embodiments of the subject application provide a polishing composition for a magnetic disk substrate, whereby the polishing composition contains colloidal silica, at least one of a phosphorus-containing inorganic acid and an organic acid, and water. According to at least one embodiment, the colloidal silica in the polishing composition has an average particle diameter (D50) in the range of 5 to 50 nm observed by a transmission electron microscope. In measuring a volume-based particle size distribution of the colloidal silica by dynamic light scattering, when the particle size distribution is measured by adjusting a concentration of colloidal silica particles to be 0.25 mass %, the colloidal silica contains 10 vol % or less of colloidal silica particles larger than 50 nm. According to at least one embodiment, the polishing composition has 1 to 50 mass % of the colloidal silica, and the polishing composition has the pH (25° C.) in the range of 0.1 to 4.0.