Method for manufacturing glass substrate for magnetic recording medium

Abstract

The present invention relates to a method for manufacturing a disk-shaped glass substrate for a magnetic recording medium, having a circular hole at the center thereof, the method including: a shape-forming step of performing shape forming to a glass substrate having a sheet shape; a polishing step of polishing a main surface of the glass substrate; and a cleaning step of cleaning the glass substrate, in which the polishing step includes a finish polishing step of simultaneously polishing both main surfaces of the glass substrate using a polishing slurry containing abrasives having an average particle diameter of 100 nm or less; and the glass substrate polished in the finish polishing step has a thickness deviation among glass substrates polished in the same lot of 1.5 μm or less.

1 . A method for manufacturing a disk-shaped glass substrate for a magnetic recording medium, having a circular hole at the center thereof, said method comprising:
 a shape-forming step of performing shape forming to a glass substrate having a sheet shape; a polishing step of polishing a main surface of the glass substrate; and a cleaning step of cleaning the glass substrate,   wherein the polishing step comprises a finish polishing step of simultaneously polishing both main surfaces of the glass substrate using a polishing slurry containing abrasives having an average particle diameter of 100 nm or less; and   the glass substrate polished in the finish polishing step has a thickness deviation among glass substrates polished in the same lot of 1.5 μm or less.   
     
     
         2 . The method for manufacturing a glass substrate for a magnetic recording medium according to  claim 1 , wherein a total removal volume of the both main surfaces of the glass substrate polished in the finish polishing step is from 0.4 to 3.0 μm. 
     
     
         3 . The method for manufacturing a glass substrate for a magnetic recording medium according to  claim 1 , wherein the abrasives are colloidal silica. 
     
     
         4 . The method for manufacturing a glass substrate for a magnetic recording medium according to  claim 2 , wherein the abrasives are colloidal silica. 
     
     
         5 . The method for manufacturing a glass substrate for a magnetic recording medium according to  claim 1 , wherein an average value of micro waviness μWa having a period of from 50 μm to 1,000 μm measured using a scanning white light interferometer at an intermediate part in a recording and reading region on the both main surfaces of the glass substrate for a magnetic recording medium is 0.12 nm or less, and difference in the average value of the micro waviness μWa among glass substrates polished in the same lot is 0.05 nm or less. 
     
     
         6 . The method for manufacturing a glass substrate for a magnetic recording medium according to  claim 2 , wherein an average value of micro waviness μWa having a period of from 50 μm to 1,000 μm measured using a scanning white light interferometer at an intermediate part in a recording and reading region on the both main surfaces of the glass substrate for a magnetic recording medium is 0.12 nm or less, and difference in the average value of the micro waviness μWa among glass substrates polished in the same lot is 0.05 nm or less. 
     
     
         7 . The method for manufacturing a glass substrate for a magnetic recording medium according to  claim 3 , wherein an average value of micro waviness μWa having a period of from 50 μm to 1,000 μm measured using a scanning white light interferometer at an intermediate part in a recording and reading region on the both main surfaces of the glass substrate for a magnetic recording medium is 0.12 nm or less, and difference in the average value of the micro waviness μWa among glass substrates polished in the same lot is 0.05 nm or less. 
     
     
         8 . The method for manufacturing a glass substrate for a magnetic recording medium according to  claim 4 , wherein an average value of micro waviness μWa having a period of from 50 μm to 1,000 μm measured using a scanning white light interferometer at an intermediate part in a recording and reading region on the both main surfaces of the glass substrate for a magnetic recording medium is 0.12 nm or less, and difference in the average value of the micro waviness μWa among glass substrates polished in the same lot is 0.05 nm or less.