Method of producing a glass substrate for a magnetic recording medium and method of producing a magnetic recording medium

Abstract

In a method of producing a glass substrate for a magnetic recording medium, including the steps of grinding a principal surface of the glass substrate of a disk-shape and polishing, after the grinding step, the principal surface of the glass substrate by an abrasive liquid including abrasive grains, the abrasive liquid includes colloidal silica abrasive grains as the abrasive grains and further includes an alkali so that a pH value of the abrasive liquid is adjusted to be greater than 10.2 and not greater than 12.

What is claimed is:  
     
         1 . A method of producing a glass substrate for a magnetic recording medium, comprising the steps of grinding a principal surface of said glass substrate of a disk-shape and polishing, after said grinding step, the principal surface of said glass substrate by an abrasive liquid including abrasive grains, wherein said abrasive grains are colloidal silica abrasive grains, said abrasive liquid comprising an alkali so that a pH value of said abrasive liquid is adjusted to be greater than 10.2 and not greater than 12.  
     
     
         2 . A method as claimed in  claim 1 , further comprising the step of carrying out, after said polishing step, alkali cleaning of the principal surface of said glass substrate.  
     
     
         3 . A method as claimed in  claim 2 , wherein the same alkali component is used as the alkali included in said abrasive liquid and an alkali used in said alkali cleaning.  
     
     
         4 . A method as claimed in  claim 1 , wherein said glass substrate is made of an aluminosilicate glass.  
     
     
         5 . A method of producing a magnetic recording medium, comprising a step of forming at least a magnetic layer on the principal surface of said glass substrate which is obtained by the method as claimed in  claim 1.