Glass substrate for magnetic disk and manufacturing method thereof

Abstract

The present invention provides a glass substrate for magnetic disk in which surface irregularity of a principal surface is suppressed and a method for efficiently manufacturing a glass substrate for magnetic disk. The method includes the steps of: forming a sheet glass material by performing press forming to molten glass, a principal surface of the sheet glass material having target flatness for the glass substrate for magnetic disk, the sheet glass material having a surface shape to be ground using a grinding abrasive grain; grinding the sheet glass material using a fixed abrasive grain; and polishing the sheet glass material using a loose abrasive grain, the sheet glass material having surface irregularity of the principal surface ground using the fixed abrasive grain.

What is claimed is: 
     
         1 . A manufacturing method of glass substrate for a magnetic disk, the method comprising:
 performing press forming to molten glass to form a sheet glass material having a surface shape to be ground by using a grinding abrasive grain; and   grinding the sheet glass material by using a fixed abrasive grain.   
     
     
         2 . The manufacturing method of glass substrate for a magnetic disk according to  claim 1 , wherein
 the sheet glass material is formed thicker than a target thickness of the glass substrate for magnetic disk by 10 μm to 150 μm; and   the sheet glass material is processed to the target thickness by the grinding.   
     
     
         3 . The manufacturing method of glass substrate for a magnetic disk according to  claim 1 , wherein a pair of dies is opened immediately after the press forming is performed. 
     
     
         4 . The manufacturing method of glass substrate for a magnetic disk according to  claim 1 , wherein the grinding is performed by using a diamond sheet with diamond particles. 
     
     
         5 . The manufacturing method of glass substrate for a magnetic disk according to  claim 1 , further comprising scribing the sheet glass material between the performing the press forming and the grinding. 
     
     
         6 . The manufacturing method of glass substrate for a magnetic disk according to  claim 5 , wherein a principal surface of the sheet glass material has roughness of 0.01 μm to 1 μm. 
     
     
         7 . The manufacturing method of glass substrate for a magnetic disk according to  claim 1 , wherein a principal surface of the sheet glass material has a flatness of 4 μm or less. 
     
     
         8 . The manufacturing method of glass substrate for a magnetic disk according to  claim 1 , wherein the sheet glass material has a haze rate of 20% or more. 
     
     
         9 . A manufacturing method of glass substrate for a magnetic disk, the method comprising:
 performing press forming to molten glass to form a sheet glass material having surface roughness ranging from 0.01 μm to 10 μm and having a haze rate of 20% or more; and   grinding the sheet glass material by using a fixed abrasive grain.   
     
     
         10 . The manufacturing method of glass substrate for a magnetic disk according to  claim 9 , wherein
 the sheet glass material is formed thicker than a target thickness of the glass substrate for magnetic disk by 10 μm to 150 μm; and   the sheet glass material is processed to the target thickness by the grinding.   
     
     
         11 . The manufacturing method of glass substrate for a magnetic disk according to  claim 9 , wherein a pair of dies is opened immediately after the press forming is performed. 
     
     
         12 . The manufacturing method of glass substrate for a magnetic disk according to  claim 9 , wherein the grinding is performed by using a diamond sheet with diamond particles. 
     
     
         13 . The manufacturing method of glass substrate for a magnetic disk according to  claim 9 , further comprising scribing the sheet glass material between the performing the press forming and the grinding. 
     
     
         14 . The manufacturing method of glass substrate for a magnetic disk according to  claim 9 , wherein a principal surface of the sheet glass material has a flatness of 4 μm or less. 
     
     
         15 . A sheet glass material used for manufacturing a glass substrate for a magnetic disk, the sheet glass material comprising:
 a principal surface having roughness of 0.01 μm to 1 μm;   the sheet glass material having a haze rate of 20% or more.