Polishing composition

Abstract

A polishing composition containing an α-alumina, an intermediate alumina, an oxidizing agent and water; a method for reducing waviness of a substrate to be polished, including the step of applying the polishing composition to the substrate to be polished; and a method for manufacturing a substrate, including the step of polishing a substrate to be polished with the polishing composition. The polishing composition is suitable for polishing substrates for precision parts such as substrates for magnetic recording media for magnetic discs, optical discs, opto-magnetic discs, and the like; photomask substrates; glass for liquid crystals; optical lenses; optical mirrors; optical prisms; and semiconductor substrates.

1 . A method for reducing waviness of a substrate to be polished, comprising the step of applying a polishing composition to the substrate to be polished, wherein the polishing composition comprising an α-alumina, an intermediate alumina, an oxidizing agent and water.  
     
     
         2 . The method according to  claim 1 , wherein the polishing composition further comprises an acid.  
     
     
         3 . A method for manufacturing a substrate, comprising the step of polishing a substrate to be polished with a polishing composition, wherein the polishing composition comprising an α-alumina, an intermediate alumina, an oxidizing agent and water.  
     
     
         4 . The method of  claim 3 , wherein the polishing composition further comprises an acid.  
     
     
         5 . The method according to  claim 1  or  3 , wherein the polishing composition has a pH that is less than 7.  
     
     
         6 . The method according to  claim 1  or  3 , wherein the weight ratio of the α-alumina to the intermediate alumina (α-alumina/intermediate alumina) in the polishing composition is from 99/1 to 30/70.  
     
     
         7 . The method according to  claim 5 , wherein the weight ratio of the α-alumina to the intermediate alumina (α-alumina/intermediate alumina) in the polishing composition is from 99/1 to 30/70.  
     
     
         8 . The method according to  claim 1  or  3 , wherein the α-alumina in the polishing composition has a secondary average particle size of from 0.01 to 2 μm and a specific surface area of from 0.1 to 50 m 2 /g, and the intermediate alumina in the polishing composition has a secondary average particle size of from 0.01 to 5 μm and a specific surface area of from 30 to 300 m 2 /g.  
     
     
         9 . The method according to  claim 5 , wherein the α-alumina in the polishing composition has a secondary average particle size of from 0.01 to 2 am and a specific surface area of from 0.1 to 50 m 2 /g, and the intermediate alumina in the polishing composition has a secondary average particle size of from 0.01 to 5 μm and a specific surface area of from 30 to 300 m 2 /g.  
     
     
         10 . The method according to  claim 6 , wherein the α-alumina in the polishing composition has a secondary average particle size of from 0.01 to 2 μm and a specific surface area of from 0.1 to 50 m 2 /g, and the intermediate alumina in the polishing composition has a secondary average particle size of from 0.01 to 5 μm and a specific surface area of from 30 to 300 m 2 /g.  
     
     
         11 . The method according to  claim 2  or  4 , wherein the acid in the polishing composition is a polyvalent acid.  
     
     
         12 . The method according to  claim 5 , wherein the acid in the polishing composition is a polyvalent acid.  
     
     
         13 . The method according to  claim 6 , wherein the acid in the polishing composition is a polyvalent acid.  
     
     
         14 . The method according to  claim 8 , wherein the acid in the polishing composition is a polyvalent acid.  
     
     
         15 . The method according to  claim 2  or  4 , wherein the acid in the polishing composition comprises an acid having a pK1 of less than 2.5 and an acid having a pK1 of 2.5 or more.  
     
     
         16 . The method according to  claim 5 , wherein the acid in the polishing composition comprises an acid having a pK1 of less than 2.5 and an acid having a pK1 of 2.5 or more.  
     
     
         17 . The method according to  claim 6 , wherein the acid in the polishing composition comprises an acid having a pK1 of less than 2.5 and an acid having a pK1 of 2.5 or more.  
     
     
         18 . The method according to  claim 8 , wherein the acid in the polishing composition comprises an acid having a pK1 of less than 2.5 and an acid having a pK1 of 2.5 or more.  
     
     
         19 . The method according to  claim 11 , wherein the acid in the polishing composition comprises an acid having a pK1 of less than 2.5 and an acid having a pK1 of 2.5 or more.