Polishing composition

Abstract

The present invention relates to a polishing composition containing a colloidal silica prepared from a silicate, the colloidal silica having an average particle size of primary particles of 1 nm or more and less than 40 nm, and water, wherein a density of silanol group on the surface of the colloidal silica is from 0.06 to 0.3 mmol per 1 g of the colloidal silica; a process for preparing the above polishing composition; a method for reducing nano scratches of a substrate and a method for manufacturing a substrate, each including the step of polishing a substrate to be polished with a polishing composition comprising a colloidal silica prepared from a silicate, the colloidal silica having an average particle size of primary particles of 1 nm or more and less than 40 nm, and water, wherein a density of silanol group on the surface of the colloidal silica is adjusted to a range from 0.06 to 0.3 mmol per 1 g of the colloidal silica. The polishing composition is suitable for polishing substrates for precision parts including, for instance, substrates for magnetic recording media, such as magnetic disks, optical disks, and opto-magnetic disks, photomask substrates, optical lenses, optical mirrors, optical prisms and semiconductor substrates, and the like.

1 . A polishing composition comprising a colloidal silica prepared from a silicate, the colloidal silica having an average particle size of primary particles of 1 nm or more and less than 40 nm, and water, wherein a density of silanol group on the surface of the colloidal silica is from 0.06 to 0.3 mmol per 1 g of the colloidal silica.  
   
   
       2 . The polishing composition according to  claim 1 , wherein a metal element is contained in an amount of from 0.001 to 2% by weight of the polishing composition.  
   
   
       3 . The polishing composition according to  claim 1 , wherein the metal element content derived from the colloidal silica is contained in an amount of from 0.001 to 0.2% by weight of the polishing composition.  
   
   
       4 . The polishing composition according to  claim 2 , wherein the metal element content derived from the colloidal silica is contained in an amount of from 0.001 to 0.2% by weight of the polishing composition.  
   
   
       5 . A process for preparing the polishing composition as defined in  claim 1 , comprising the steps of: 
 step (1): adjusting a pH of a silica dispersion comprising the colloidal silica having an average particle size of primary particles of 1 nm or more and less than 40 nm to a range of from 10 to 14; and    step (2): re-adjusting a pH of the silica dispersion obtained in the step (1) to a range of from 1 to 6.    
   
   
       6 . A process for preparing the polishing composition as defined in  claim 2 , comprising the steps of: 
 step (1): adjusting a pH of a silica dispersion comprising the colloidal silica having an average particle size of primary particles of 1 nm or more and less than 40 nm to a range of from 10 to 14; and    step (2): re-adjusting a pH of the silica dispersion obtained in the step (1) to a range of from 1 to 6.    
   
   
       7 . A process for preparing the polishing composition as defined in  claim 3 , comprising the steps of: 
 step (1): adjusting a pH of a silica dispersion comprising the colloidal silica having an average particle size of primary particles of 1 nm or more and less than 40 nm to a range of from 10 to 14; and    step (2): re-adjusting a pH of the silica dispersion obtained in the step (1) to a range of from 1 to 6.    
   
   
       8 . A process for preparing the polishing composition as defined in  claim 4 , comprising the steps of: 
 step (1): adjusting a pH of a silica dispersion comprising the colloidal silica having an average particle size of primary particles of 1 nm or more and less than 40 nm to a range of from 10 to 14; and    step (2): re-adjusting a pH of the silica dispersion obtained in the step (1) to a range of from 1 to 6.    
   
   
       9 . A method for reducing nano scratches of a substrate, comprising the step of polishing a substrate to be polished with a polishing composition comprising a colloidal silica prepared from a silicate, the colloidal silica having an average particle size of primary particles of 1 nm or more and less than 40 nm, and water, wherein a density of silanol group on the surface of the colloidal silica is adjusted to a range from 0.06 to 0.3 mmol per 1 g of the colloidal silica.  
   
   
       10 . A method for manufacturing a substrate, comprising the step of polishing a substrate to be polished with a polishing composition comprising a colloidal silica prepared from a silicate, the colloidal silica having an average particle size of primary particles of 1 nm or more and less than 40 nm, and water, wherein a density of silanol group on the surface of the colloidal silica is adjusted to a range from 0.06 to 0.3 mmol per 1 g of the colloidal silica.  
   
   
       11 . The method according to  claim 10 , wherein the substrate is a magnetic disk substrate.