Substrate for magnetic recording media, manufacturing method for the same, and magnetic recording media

Abstract

A substrate surface polishing step in the manufacturing method for a magnetic recording medium glass substrate uses a polishing solution consisting of a mixture solution of water and abrasive grains with potassium hydroxide. One embodiment of the invention uses only a mixture solution of water and potassium hydroxide to manufacture a glass substrate with very fine surface roughness. A second embodiment uses a two-step process in which the glass substrate is first polished using water, abrasive grains and potassium hydroxide, and is then again polished using water and potassium hydroxide, but omitting abrasive grains. A glass substrate, produced according to the invention, results in the manufacture of a magnetic recording medium with excellent high recording density.

What is claimed is:  
     
         1 . A manufacturing method for a glass substrate for a magnetic recording medium, comprising: 
 mixing a polishing solution of water and abrasive grains with potassium hydroxide; and    polishing a surface of said glass substrate with said polishing solution.    
     
     
         2 . A manufacturing method according to    claim 1   , wherein: 
 a concentration of potassium hydroxide in said polishing solution is from about 0.1 weight % to about 15 weight %.    
     
     
         3 . A manufacturing method according to    claim 1   , wherein said abrasive grains are cerium oxide.  
     
     
         4 . A manufacturing method according to    claim 2   , wherein said abrasive grains are cerium oxide.  
     
     
         5 . A manufacturing method for a substrate for a magnetic recording medium: 
 mixing a polishing solution containing at least water and potassium hydroxide;    polishing a surface of said magnetic recording medium by a total surface contact processing method wherein polishing is conducted by simultaneous contact of a processing member with an entire surface of said substrate surface.    
     
     
         6 . A manufacturing method for a substrate for a magnetic recording medium, comprising: 
 mixing a polishing solution containing at least water and potassium hydroxide;    surface polishing a surface of said substrate using said polishing solution;    said surface polishing is by a partial contact processing method wherein polishing is conducted by having a first section of a rotating substrate surface contact a second section of a processing member that is moving.    
     
     
         7 . A manufacturing method for a substrate for a magnetic recording medium, according to    claim 6   , wherein: 
 during surface polishing, a contact surface area of said first section is from about 2% to about 30% of a total surface area of said substrate.    
     
     
         8 . A manufacturing method for a substrate for a magnetic recording medium, comprising: 
 mixing a polishing solution containing at least water and potassium hydroxide;    surface polishing a surface of said substrate using said polishing solution;    and then chemically strengthening said glass substrate.    
     
     
         9 . A substrate for a magnetic recording medium having a surface polished using a mixture of water and at least potassium hydroxide.  
     
     
         10 . A magnetic recording medium, comprising: 
 a magnetic recording medium substrate having a polished surface polished using a mixture of water and at least potassium hydroxide;    sequential layering of at least a magnetic layer on said surface;    layering at least a protective layer on said magnetic layer.    
     
     
         11 . A manufacturing method for a glass substrate for a magnetic recording medium, comprising: 
 mixing a polishing solution of water and potassium hydroxide; and    polishing a surface of said glass substrate with said polishing solution.    
     
     
         12 . A manufacturing method for a glass substrate for a magnetic recording medium, comprising: 
 mixing a first polishing solution of water, potassium hydroxide and an abrasive;    polishing a surface of said glass substrate with said first polishing solution;    mixing a second polishing solution of water and potassium hydroxide; and    polishing said surface with said second polishing solution until a residue of said abrasive is substantially removed, and a desired surface smoothness is attained.