Patent ID: 9070399
Filing Date: 2015-06-30
Classification: C09G,C23F,G11B,H01L

Abstract:
1. A polishing composition for a magnetic disk substrate, comprising: a copolymer that has a hydrophobic constituent unit derived from a monomer having a solubility of 2 g or less in 100 g of water at 20° C. and a constituent unit having a sulfonic acid group, and has a saturated hydrocarbon chain as the main chain thereof, or a salt of the copolymer; an abrasive; and water; wherein the total proportion of the hydrophobic constituent unit and the constituent unit having a sulfonic acid group relative to all the constituent units constituting the polymer is 90 to 100 mol %, wherein the hydrophobic constituent unit is derived from styrene, and the constituent unit having a sulfonic acid group is derived from styrenesulfonic acid or its salt, and wherein the molar ratio of the constituent unit derived from a monomer having a solubility of 2 or less 100 g of water at 20° C. to the constituent unit having a sulfonic acid group in all the constituent units constituting the copolymer is 10/90 to 60/40.