Glass substrates for magnetic media and magnetic media based on such glass substrates

Abstract

Described are substrates for magnetic media which have excellent surface properties as prepared directly from a slot drawdown glass sheet forming process. The substrate blanks cut directly from the glass sheet, as drawn, require little or no surface treatment for use as substrates for magnetic media, particularly hard disk drives. Also described are methods for preparing such substrates and methods for preparing magnetic media therefrom. Further described are the substrates and magnetic media prepared by such processes.

We claim:  
     
         1 . A substrate for a magnetic medium prepared from a glass sheet drawn from a slot downdraw process.  
     
     
         2 . The substrate of  claim 1 , wherein the glass sheet has the following properties, as drawn from the slot downdraw process without any subsequent surface treatment: 
 flatness≦25 microns,    waviness less than 100 angstroms,    thickness variation±20 microns, and    surface roughness, less than 10 angstroms.    
     
     
         3 . The substrate of  claim 1 , wherein the glass sheet has the following properties, as drawn from the slot downdraw process without any subsequent surface treatment: 
 flatness≦10 microns,    waviness less than 40 angstroms,    thickness variation±15 microns, and    surface roughness, less than 5 angstroms.    
     
     
         4 . The substrate of  claim 1 , wherein the substrate surface is provided with adequate surface properties solely by touch polishing and cleaning of said glass sheet as drawn from the slot downdraw process.  
     
     
         5 . The substrate of  claim 1 , wherein the magnetic medium is a hard disk drive.  
     
     
         6 . A hard disk drive which comprises a substrate according to  claim 1  in disk shape and a magnetic layer.  
     
     
         7 . A method for preparing a glass magnetic media substrate which comprises: 
 drawing a glass sheet from a slot downdraw process, and    cutting said glass magnetic media substrate from the glass sheet.    
     
     
         8 . The method of  claim 7 , wherein the substrate has the following properties prior to any surface treatment subsequent to drawing from the slot downdraw process: 
 flatness≦25 microns,    waviness less than 100 angstroms,    thickness variation±20 microns, and    surface roughness, less than 10 angstroms.    
     
     
         9 . The method of  claim 7 , wherein the substrate has the following properties prior to any surface treatment subsequent to drawing from the slot downdraw process: 
 flatness≦10 microns,    waviness less than 40 angstroms,    thickness variation±15 microns, and    surface roughness, less than 5 angstroms.    
     
     
         10 . The method of  claim 7 , wherein the only treatment which results in removal of glass material from the substrate surface is touch polishing and cleaning.  
     
     
         11 . The method of  claim 10 , wherein the touch polishing decreases the thickness of the substrate by a maximum of 0.02 mm.  
     
     
         12 . The method of  claim 10 , wherein the touch polishing decreases the thickness of the substrate by a maximum of 0.01 mm.  
     
     
         13 . The method of  claim 7 , wherein the glass magnetic media substrate is cut from the glass sheet in the form of a disk and is a substrate for a hard disk drive.  
     
     
         14 . The method of  claim 7 , wherein a plurality of sheets of glass are arranged as a stack together with an adhesive interleaving layer in between each sheet and a plurality of substrates are cut from the stack in a single cutting step.  
     
     
         15 . The method of  claim 7 , wherein the glass magnetic media substrate has a thickness from 0.8 to 1.1 mm.  
     
     
         16 . The method of  claim 7 , wherein the glass magnetic media substrate has a thickness from 0.03 to 1.9 mm.  
     
     
         17 . A magnetic medium comprising a glass substrate prepared by the method of  claim 7  and a magnetic layer thereon.  
     
     
         18 . A magnetic medium comprising a glass substrate prepared by the method of  claim 10  and a magnetic layer thereon.  
     
     
         19 . The magnetic medium of  claim 17 , wherein the magnetic medium is a hard disk drive.  
     
     
         20 . A method for preparing a hard disk drive having a glass substrate which comprises: 
 drawing a glass sheet from a slot downdraw process,    cutting a disk from the glass sheet,    touch polishing and cleaning the disk, and    applying a magnetic layer to the disk surface.    
     
     
         21 . The method of  claim 20 , wherein the only treatment which results in removal of glass material from the disk surface after drawing of the glass sheet is touch polishing and cleaning.  
     
     
         22 . The method of  claim 17 , wherein the touch polishing decreases the thickness of the disk by a maximum of 0.02 mm.  
     
     
         23 . The method of  claim 17 , wherein the touch polishing decreases the thickness of the disk by a maximum of 0.01 mm.