Polishing composition for magnetic disk

Abstract

A polishing composition for a magnetic disk, comprising alumina, water, a peroxide and an organic acid; a polishing process for a substrate to be polished, comprising the step of polishing the substrate to be polished with the polishing composition; and a process for manufacturing a substrate, comprising the step of polishing a substrate to be polished with the polishing composition. The polishing composition can be suitably used for the manufacture of a magnetic disk substrate for high-quality hard disks and the like.

1 . A polishing composition for a magnetic disk, comprising alumina, water, a peroxide and an organic acid.  
     
     
         2 . The polishing composition according to  claim 1 , wherein the organic acid is one or more members selected from the group consisting of sulfur-containing organic acids, carboxylic acids, and phosphorus-containing organic acids.  
     
     
         3 . The polishing composition according to  claim 1  or  2 , further comprising an inorganic acid.  
     
     
         4 . The polishing composition according to  claim 1 , wherein the composition has a pH of 0.1 or more and less than 6.  
     
     
         5 . The polishing composition according to  claim 3 , wherein the composition has a pH of 0.1 or more and less than 6.  
     
     
         6 . A polishing process for a substrate to be polished, comprising the step of polishing the substrate to be polished with the polishing composition of  claim 1 .  
     
     
         7 . A polishing process for a substrate to be polished, comprising the step of polishing the substrate to be polished with the polishing composition of  claim 3 .  
     
     
         8 . The polishing process according to  claim 6 , wherein the substrate to be polished is a substrate produced by plating an aluminum alloy with a Ni—P alloy.  
     
     
         9 . The polishing process according to  claim 7 , wherein the substrate to be polished is a substrate produced by plating an aluminum alloy with a Ni—P alloy.  
     
     
         10 . A process for manufacturing a substrate, comprising the step of polishing a substrate to be polished with the polishing composition of  claim 1 .  
     
     
         11 . A process for manufacturing a substrate, comprising the step of polishing a substrate to be polished with the polishing composition of  claim 3 .  
     
     
         12 . The process according to  claim 10 , wherein the substrate to be polished is a substrate produced by plating an aluminum alloy with a Ni—P alloy.  
     
     
         13 . The process according to  claim 11 , wherein the substrate to be polished is a substrate produced by plating an aluminum alloy with a Ni—P alloy.