Polishing slurry and polished substrate

Abstract

A polishing slurry comprising an abrasive comprising as a basic ingredient rare earth oxides containing cerium oxide, which polishing slurry further comprises an anionic surfactant and a nonionic surfactant and has a pH value of at least 11. The polishing slurry is especially suitable for polishing a glass substrate for magnetic disc, and other substrates used in electronic field.

1 . A polishing slurry comprising an abrasive comprising as a basic ingredient rare earth oxides containing cerium oxide, said polishing slurry further comprising an anionic surfactant and a nonionic surfactant and having a pH value of at least 11.  
   
   
       2 . The polishing slurry according to  claim 1 , wherein the abrasive comprises at least 90% by mass, based on the abrasive, of the rare earth oxides.  
   
   
       3 . The polishing slurry according to  claim 1 , wherein the rare earth oxides contain 50% to 90% by mass, based on the rare earth oxides, of cerium oxide.  
   
   
       4 . The polishing slurry according to  claim 1 , wherein the rare earth oxides are produced from rare earth carbonate as a starting raw material.  
   
   
       5 . The polishing slurry according to  claim 1 , wherein the abrasive is comprised of particles having a 50% cumulative average diameter (D50) in the range of 0.01 μm to 10 μm.  
   
   
       6 . The polishing slurry according to  claim 1 , wherein the abrasive is comprised of particles having a specific surface area in the range of 1 m 2 /g to 50 m 2 /g.  
   
   
       7 . The polishing slurry according to  claim 1 , wherein the anionic surfactant is at least one surfactant selected from the group consisting of low-molecular-weight compounds and high-molecular-weight compounds, which are selected from carboxylic acid salts, sulfonic acid salts, sulfuric acid ester salts and phosphoric acid ester salts.  
   
   
       8 . The polishing slurry according to  claim 1 , wherein the nonionic surfactant is at least one surfactant selected from the group consisting of polyoxyethylene alkyl phenyl ethers, polyoxyalkylene alkyl ethers and polyoxyethylene fatty acid esters.  
   
   
       9 . The polishing slurry according to  claim 1 , which further comprises at least one liquid medium selected from the group consisting of water, monohydric alcohols having 1 to 10 carbon atoms, glycols, polyhydric alcohols having 1 to 10 carbon atoms, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran and dioxane.  
   
   
       10 . The polishing slurry according to  claim 1 , which further comprises at least one ingredient selected from the group consisting of phosphoric acid esters, cellulose ethers and water-soluble high-molecular-weight compounds.  
   
   
       11 . A process for polishing a substrate, wherein the polishing of the substrate is carried out by using the polishing slurry as claimed in  claim 1 .  
   
   
       12 . A process for producing a polished substrate comprising a step of polishing a substrate by the process as claimed in  claim 11 .  
   
   
       13 . A polished substrate obtainable by the process as claimed in  claim 12 .  
   
   
       14 . The substrate according to  claim 13 , which is selected from the group consisting of a glass substrate for optical lens, a glass substrate for optical disc, a glass substrate for plasma display, a glass substrate for liquid crystal, a color filter for liquid crystal TV, a glass substrate for LSI photomask and a substrate for magnetic disc.