Apparatus for polishing edge surface of glass substrate for magnetic recording media, and process for producing glass substrate

Abstract

To provide an apparatus for polishing an edge surface of a glass substrate for magnetic recording media and a process for producing a glass substrate for magnetic recording media, whereby with respect to a glass substrate to be used as a substrate for a hard disk, the quality and productivity can be improved without requiring extra effort. In a process for practically producing a hard disk by using a glass substrate 2, the arithmetic average roughness (Ra) required for the outer edge surface of the glass substrate is at most 100 nm. With the roughness of this level, highly productive mechanical polishing by a grindstone is possible. Further, since such mechanical polishing is possible, the productivity can be increased by adopting sheet treatment. Further, by stabilizing the processing margin by employing a grindstone 4 made of resin, variations in the dimensional precision in the individual glass substrates can be minimized. The grindstone 4 made of resin is a formed grindstone having a groove 4 A formed to simultaneously polish the outer edge surface 2 A of the glass substrate 2 and chamfers 2 B and 2 C on both sides thereof. By employing such a formed grindstone as the grindstone 4 of the resin, it is possible to simultaneously polish the outer edge surface 2 A of the glass substrate 2 and the chamfers 2 B and 2 C on both sides thereof, whereby the productivity and quality can be further improved.

1 . An apparatus for polishing an edge surface of a glass substrate for magnetic recording media, characterized in that an outer edge surface and/or an inner edge surface of a glass substrate for magnetic recording media is polished by pressing said outer edge surface and/or said inner edge surface against a grindstone made of resin, prepared by mixing abrasive grains to a resin, so that the arithmetic average roughness (Ra) of said outer edge surface and/or said inner edge surface would be at most 100 nm.  
   
   
       2 . An apparatus for polishing an edge surface of a glass substrate for magnetic recording media, which comprises a first station to carry out mounting and dismounting of the glass substrate, a second station to carry out grinding of an outer edge surface and/or an inner edge surface of the glass substrate, a third station to carry out polishing of the outer edge surface and/or the inner edge surface of the glass substrate, and a transfer mechanism to transfer the glass substrate mounted at the first station sequentially via the second station and the third station to the first station, wherein at the third station, the outer edge surface and/or the inner edge surface of the glass substrate is polished by pressing said outer edge surface and/or said inner edge surface against a grindstone made of resin, prepared by mixing abrasive grains to a resin, so that the arithmetic average roughness (Ra) of said outer edge surface and/or said inner edge surface would be at most 100 nm.  
   
   
       3 . The apparatus for polishing an edge surface of a glass substrate for magnetic recording media according to  claim 1 , wherein the grindstone made of resin is a formed grindstone to simultaneously polish said outer edge surface and/or said inner edge surface, and chamfers.  
   
   
       4 . The apparatus for polishing an edge surface of a glass substrate for magnetic recording media according to  claim 2 , wherein the grindstone made of resin is a formed grindstone to simultaneously polish said outer edge surface and/or said inner edge surface, and chamfers.  
   
   
       5 . A process for producing a glass substrate for magnetic recording media, which comprises polishing an outer edge surface and/or an inner edge surface of a glass substrate for magnetic recording media by pressing said outer edge surface and/or said inner edge surface against a grindstone made of resin, prepared by mixing abrasive grains to a resin, to finish so that the arithmetic average roughness (Ra) of said outer edge surface and/or said inner edge surface would be at most 100 nm.