Polishing composition, method for producing substrate, and polishing method

Abstract

Provided is a polishing composition for polishing a magnetic disk substrate that has good initial polishing performance and suppressed changes in the polishing performance over time. The polishing composition for polishing of a magnetic disk substrate is provided. The polishing composition contains silica particles as an abrasive and water. The silica particles have an average aspect ratio of 1.1 or more based on SEM image analysis, and a ratio (D99 / D90) of the cumulative 99% particle size D99 to the cumulative 90% particle size D90 of 1.4 or more, with the cumulative 90% particle size D90 being 250 nm or less, in a particle size distribution on a weight basis in accordance with a photocentrifuge method.