Polishing composition

Abstract

A polishing composition of abrasive grains, a phosphorus-containing inorganic acid or salt thereof and another inorganic acid or salt thereof contained in an aqueous medium is used for the polishing of magnetic disk substrates or the like.

1 . A polishing composition comprising abrasive grains, a phosphorus-containing inorganic acid or salt thereof and another inorganic acid or salt thereof contained in an aqueous medium.  
     
     
         2 . The polishing composition according to  claim 1 , wherein the abrasive grains are at least one selected from the group consisting of alumina, titania, silica and zirconia.  
     
     
         3 . The polishing composition according to  claim 1  or  2 , wherein the mean particle size of the abrasive grains is from 0.001 to 0.5 μm.  
     
     
         4 . The polishing composition according to any of claims  1  through  3 , wherein the abrasive grains are colloidal particles.  
     
     
         5 . The polishing composition according to any of claims  1  through  4 , wherein the phosphorus-containing inorganic acid is phosphoric acid or phosphonic acid.  
     
     
         6 . The polishing composition according to any of claims  1  through  5 , wherein the other inorganic acid or salt thereof is at least one acid selected from the group consisting of nitric acid, sulfuric acid, amidosulfuric acid and boric acid.  
     
     
         7 . The polishing composition according to any of claims  1  through  6 , wherein the oxidizing agent is at least one compound selected from the group consisting of the peroxides, perborates, persulfates or nitrates.  
     
     
         8 . The polishing composition according to  claim 7 , wherein the peroxide is hydrogen peroxide.  
     
     
         9 . The polishing composition according to  claim 7 , wherein the perborate is sodium perborate.  
     
     
         10 . The polishing composition according to any of claims  1  through  9 , wherein the pH is 1 to 5.  
     
     
         11 . The polishing composition according to any of claims  1  through  10 , wherein the abrasive grain content is in the range from 3 to 30% by mass, the content of the inorganic acid or salt thereof is in the range from 0.1 to 8% by mass and the oxidizing agent content is in the range from 0.2 to 5% by mass.  
     
     
         12 . The polishing composition according to any of claims  1  through  11 , wherein the polishing composition is a composition for polishing magnetic disk substrates.  
     
     
         13 . A magnetic disk substrate polished by the composition for polishing magnetic disk substrates according to  claim 12.