Polishing composition

Abstract

A polishing composition containing an abrasive and water, wherein the polishing composition has a pH of from 0.1 to 7, and satisfies the following conditions: (1) that the number of polishing particles having sizes of 0.56 μm or more and less than 1 μm is 500,000 or less per 1 cm 3 of the polishing composition; and (2) that the ratio of polishing particles having sizes of 1 μm or more is 0.001% by weight or less to the entire polishing particles in the polishing composition. The polishing composition is suitable for polishing substrates for precision parts including, for example, recording disk substrates, 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 an abrasive and water, wherein the polishing composition has a pH of from 0.1 to 7, and satisfies the following conditions: 
 (1) that the number of polishing particles having sizes of 0.56 μm or more and less than 1 μm is 500,000 or less per 1 cm 3  of the polishing composition; and    (2) that the ratio of polishing particles having sizes of 1 μm or more is 0.001% by weight or less to the entire polishing particles in the polishing composition.    
   
   
       2 . The polishing composition according to  claim 1 , wherein the polishing composition further satisfies the following condition: 
 (3) that the ratio of polishing particles having sizes of 3 μm or more is 0.0008% by weight or less to the entire polishing particles in the polishing composition.    
   
   
       3 . The polishing composition according to  claim 1 , wherein the abrasive has an average particle size of primary particles of from 1 to 50 nm.  
   
   
       4 . The polishing composition according to  claim 1 , wherein the abrasive is contained in the polishing composition in an amount of from 0.5 to 20% by weight.  
   
   
       5 . The polishing composition according to  claim 1 , wherein the abrasive is colloidal silica.  
   
   
       6 . The polishing composition according to  claim 1 , wherein the polishing composition is used for a magnetic disk substrate.  
   
   
       7 . The polishing composition according to  claim 1 , wherein the number of nano scratches of a polished substrate is 1.5 or less per 1 cm 2  according to a standard test.  
   
   
       8 . A polishing particle preparation comprising an abrasive and water, satisfying the following conditions: 
 (i) that the number of polishing particles having sizes of 0.56 μm or more and less than 1 μm is 500,000 or less per 1 cm 3  of the polishing particle preparation; and    (ii) that the ratio of polishing particles having sizes of 1 μm or more is 0.001% by weight or less to the entire polishing particles in the polishing particle preparation,    wherein the polishing particle preparation is used in the preparation of the polishing composition as defined in  claim 1 .    
   
   
       9 . A process for producing the polishing composition as defined in  claim 1 , comprising the following purification steps of: 
 (I) filtering a pre-purification polishing composition with a depth-type filter, to give an intermediate filtrate; and    (II) filtering the intermediate filtrate with a pleated type filter, to give the polishing composition,    wherein the fluctuation range of the pressure at an inlet of the depth-type filter in the step (I) is 50 kPa or less.    
   
   
       10 . The process according to  claim 9 , wherein the number of polishing particles having sizes of 0.56 μm or more and less than 1 μm is 1,000,000 or less per 1 cm 3  of the intermediate filtrate obtained after the step (I).  
   
   
       11 . The process according to  claim 9 , wherein the number of polishing particles having sizes of 0.56 μm or more and less than 1 μm is 1,000,000 or less per 1 cm 3  of the intermediate filtrate to be supplied for the step (II).  
   
   
       12 . A process for producing the polishing particle preparation as defined in  claim 8 , comprising the following purification steps of: 
 (I′) filtering a pre-purification polishing particle preparation with a depth-type filter, to give an intermediate filtrate; and    (II′) filtering the intermediate filtrate with a pleated type filter, to give the polishing particle preparation,    wherein the fluctuation range of the pressure at an inlet of the depth-type filter in the step (I′) is 50 kPa or less.    
   
   
       13 . The process according to  claim 12 , wherein the number of polishing particles having sizes of 0.56 μm or more and less than 1 μm is 1,000,000 or less per 1 cm 3  of the intermediate filtrate obtained after the step (I′).  
   
   
       14 . The process according to  claim 12 , wherein the number of polishing particles having sizes of 0.56 μm or more and less than 1 μm is 1,000,000 or less per 1 cm 3  of the intermediate filtrate to be supplied for the step (II′).  
   
   
       15 . A method for manufacturing a substrate, comprising the step of polishing a substrate with a polishing machine using the polishing composition as defined in  claim 1 .  
   
   
       16 . The method according to  claim 15 , wherein the substrate is a magnetic disk substrate.  
   
   
       17 . The method according to  claim 16 , wherein the magnetic disk substrate is a Ni—P plated aluminum alloy substrate.  
   
   
       18 . The method according to  claim 15 , wherein the method comprising the step of polishing a substrate to be polished while feeding the polishing composition to the polishing machine comprising a platen at a flow rate of 0.06 cm 3 /minute or more per 1 cm 2  of an area to be polished of the substrate.  
   
   
       19 . The method according to  claim 15 , wherein the platen pressure of the polishing machine is from 3 to 50 kPa.  
   
   
       20 . The method according to  claim 15 , wherein the method comprises plural polishing steps, wherein the polishing composition is used for a finish polishing.  
   
   
       21 . The method according to  claim 15 , wherein a difference between a pH of the polishing composition before polishing and a pH of a waste liquid after polishing is 2 or less.