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 process for a substrate to be polished, comprising the step of polishing the substrate to be polished with a polishing composition for a magnetic disk, comprising alumina, water, a peroxide and an organic acid.  
   
   
       2 . The polishing process according to  claim 1 , wherein said polishing composition further comprises an inorganic acid.  
   
   
       3 . The polishing process according to  claim 1 , wherein the substrate to be polished is a substrate produced by plating an aluminum alloy with a Ni—P alloy.  
   
   
       4 . The polishing process according to  claim 2 , wherein the substrate to be polished is a substrate produced by plating an aluminum alloy with a Ni—P alloy.  
   
   
       5 . A process for manufacturing a substrate, comprising the step of polishing a substrate to be polished with a polishing composition for a magnetic disk, comprising alumina, water, a peroxide and an organic acid.  
   
   
       6 . The process according to  claim 5 , wherein said polishing composition further comprises an inorganic acid.  
   
   
       7 . The process according to  claim 5 , wherein the substrate to be polished is a substrate produced by plating an aluminum alloy with a Ni—P alloy.  
   
   
       8 . The 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 . A method for reducing waviness of a substrate to be polished, comprising the step of applying to the substrate to be polished a polishing composition comprising alumina, water, a peroxide and an organic acid.  
   
   
       10 . The method according to  claim 9 , 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.  
   
   
       11 . The method according to  claim 9 , wherein the polishing composition further comprises an inorganic acid.  
   
   
       12 . The method according to  claim 9 , wherein the polishing composition has a pH of 0.1 or more and less than 6.  
   
   
       13 . The method according to  claim 11 , wherein the polishing composition has a pH of 0.1 or more and less than 6.  
   
   
       14 . A method for reducing surface stains of a substrate to be polished, comprising the step of applying to the substrate to be polished a polishing composition comprising alumina, water, a peroxide and an organic acid.  
   
   
       15 . The method according to  claim 14 , 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.  
   
   
       16 . The method according to  claim 14 , wherein the polishing composition further comprises an inorganic acid.  
   
   
       17 . The method according to  claim 14 , wherein the polishing composition has a pH of 0.1 or more and less than 6.  
   
   
       18 . The method according to  claim 16 , wherein the polishing composition has a pH of 0.1 or more and less than 6.