Polishing composition

Abstract

The present invention relates to a polishing composition containing an aqueous medium and silica particles, wherein the silica particles in the polishing composition has a zeta potential of from −15 to 40 mV; a method for manufacturing a substrate including the step of polishing a substrate to be polished with a polishing composition containing an aqueous medium and silica particles, wherein the silica particles in the polishing composition has a zeta potential of from −15 to 40 mV; and a method for reducing scratches on a substrate to be polished with a polishing composition containing an aqueous medium and silica particles, including the step of adjusting a zeta potential of silica particles in the polishing composition to −15 to 40 mV. The polishing composition can be favorably used in polishing the substrate for precision parts, including substrates for magnetic recording media such as magnetic discs, optical discs and opto-magnetic discs; photomask substrates; optical lenses; optical mirrors; optical prisms; semiconductor substrates; and the like.

1 . A polishing composition comprising an aqueous medium and silica particles, wherein the silica particles in the polishing composition has a zeta potential of from −15 to 40 mV.  
   
   
       2 . The polishing composition according to  claim 1 , wherein the silica particles have an average primary particle size of 1 nm or more and less than 40 nm.  
   
   
       3 . The polishing composition according to  claim 1 , wherein the silica is a colloidal silica.  
   
   
       4 . The polishing composition according to  claim 1 , wherein the polishing composition comprises one or more zeta potential adjusting agents selected from the group consisting of acids, bases, salts and surfactants.  
   
   
       5 . A method of polishing a glass substrate with the polishing composition as defined in  claim 1 .  
   
   
       6 . A method of polishing a memory hard disk substrate with the polishing composition as defined in  claim 1 .  
   
   
       7 . The method according to  claim 6 , wherein the memory hard disk substrate is a Ni—P plated substrate.  
   
   
       8 . A method for manufacturing a substrate comprising the step of polishing a substrate to be polished with a polishing composition comprising an aqueous medium and silica particles, wherein the silica particles in the polishing composition has a zeta potential of from −15 to 40 mV.  
   
   
       9 . The method according to  claim 8 , wherein the silica particles have an average primary particle size of 1 nm or more and less than 40 nm.  
   
   
       10 . The method according to  claim 8 , wherein the substrate is a memory hard disk substrate.  
   
   
       11 . A method for increasing a polishing rate of a substrate to be polished with a polishing composition comprising an aqueous medium and silica particles, comprising the step of adjusting a zeta potential of silica particles in the polishing composition to −15 to 40 mV.  
   
   
       12 . The method according to  claim 11 , wherein the silica particles have an average primary particle size of 1 nm or more and less than 40 nm.  
   
   
       13 . The method according to  claim 11 , wherein the substrate to polished is made of at least silicon on its surface.  
   
   
       14 . The method according to  claim 11 , wherein the substrate to be polished is a memory hard disk substrate.  
   
   
       15 . The method according to  claim 11 , further comprising the step of pressing a polishing pad against the substrate to be polished at a polishing load of 0.5 to 20 kPa.  
   
   
       16 . A method for manufacturing a substrate comprising the step of applying the method as defined in  claim 11  to a substrate to be polished.  
   
   
       17 . A method for reducing scratches on a substrate to be polished with a polishing composition comprising an aqueous medium and silica particles, comprising the step of adjusting a zeta potential of silica particles in the polishing composition to −15 to 40 mV.  
   
   
       18 . The method according to  claim 17 , wherein the silica particles have an average primary particle size of 1 nm or more and less than 40 nm.  
   
   
       19 . The method according to  claim 17 , wherein the substrate to be polished is a memory hard disk substrate.  
   
   
       20 . The method according to  claim 17 , further comprising the step of pressing a polishing pad against the substrate to be polished while feeding the polishing composition at a rate of from 0.01 to 3 mL/minute per 1 cm 2  of the substrate to be polished.