Clamping jig for glass substrate, buffer sheet, method for processing glass substrate, and glass substrate

Abstract

The present invention provides a method which can simultaneously grind inner peripheral edges and outer peripheral edges of a multiplicity of glass substrates used for magnetic storage media or the like. In order to chamfer the outer edges of the glass substrates g, a multiplicity of annular glass substrates g are firstly stacked with buffer sheets 5 interposed between the glass substrates to make a glass substrate block G. Then, a first plates 1, 1 of the above described clamping jig are applied to both sides of the glass substrate block G, and a first fastening tool 3 is inserted through center holes of the first plates 1, 1 and the glass substrate block G. Next, the glass substrate block G is clamped from an inside thereof for chamfering the outer edges with a grindstone 6.

What is claimed is:  
     
         1 . A clamping jig for holding a multiplicity of annular glass substrates with the annular glass substrates being stacked, comprising: 
 a first pair of plates, each plate of which is pressed against each side of a glass substrate block fabricated by stacking the multiplicity of glass substrates and each plate of which is provided with a fastening tool insertion hole at a center of the each plate;    a first fastening tool which is inserted through an inner hole of said glass substrate block, end portions of the first fastening tool being attached to the fastening tool insertion holes of said first plates;    a second pair of plates, each plate of which is disposed outside said first plate and each plate of which has an inner diameter smaller than an outer diameter of the first plate; and    a second fastening tool for fastening the second pair of plates at a portion outside said glass substrate block.    
     
     
         2 . A buffer sheet which is interposed between annular glass substrates, wherein the buffer sheet is made of a flexible material whose Rockwell hardness is 40 or less.  
     
     
         3 . A buffer sheet which is interposed between annular glass substrates, wherein the buffer sheet comprises a two-layered structure including a flexible layer and a hard layer.  
     
     
         4 . A buffer sheet which is interposed between annular glass substrates, wherein the buffer sheet comprises a three-layered structure in which a hard layer is sandwiched between flexible layers.  
     
     
         5 . The buffer sheet according to  claim 3  or  4 , wherein said hard layer has a compressive elasticity modulus of 100 MPa or more.  
     
     
         6 . The buffer sheet according to  claims 2  to  5 , wherein a thickness of the buffer sheet is 0.2 mm or less.  
     
     
         7 . The buffer sheet according to  claims 2  to  6 , wherein the buffer sheet is shaped such that an inner diameter of the buffer sheet is larger than an inner diameter of the glass substrate and an outer diameter of the buffer sheet is smaller than an outer diameter of the glass substrate.  
     
     
         8 . A method for processing a glass substrate, wherein 
 a multiplicity of annular glass substrates are stacked alternately with the buffer sheets according to  claims 2  to  7 ,    said glass substrates are clamped at an outer or inner peripheral side of the glass substrates, and    said outer or inner peripheral side which is not clamped is ground.    
     
     
         9 . A method for processing a glass substrate, wherein 
 a stack of a multiplicity of annular glass substrates is clamped at an outer side or an inner side thereof while buffer sheets are respectively interposed between the annular glass substrates such that the buffer sheets do not protrude from inner peripheral edges and outer peripheral edges of the glass substrates,    the outer peripheral edges of the multiplicity of glass substrates are simultaneously ground with the stack being clamped at the inner side thereof,    the inner peripheral edges of the multiplicity of glass substrates are simultaneously ground with the stack being clamped at the outer side thereof, and further,    the clamping situation of the glass substrates is maintained even at a time of switching between an operation for grinding said inner peripheral edges and an operation for grinding said outer peripheral edges.    
     
     
         10 . The method for processing a glass substrate according to  claim 9 , wherein the grinding of said outer peripheral edges and said inner peripheral edges is chamfering which is conducted by allowing a grindstone to come into rotationally contact with the outer peripheral edges and the inner peripheral edges, the grindstone being made by bonding diamond abrasive grains to an alloy.  
     
     
         11 . The method for processing a glass substrate according to  claim 9 , wherein the grinding of said outer peripheral edges and said inner peripheral edges is polishing which is conducted by allowing a polishing brush or a polishing pad to come into rotationally contact with the outer peripheral edges and the inner peripheral edges while supplying a polishing agent thereto.  
     
     
         12 . The method for processing a glass substrate, wherein the outer peripheral edges and the inner peripheral edges are polished by allowing the polishing brush or the polishing pad to come into rotationally contact with the outer peripheral edges and the inner peripheral edges while supplying the polishing agent thereto, with the clamping situation of the glass substrates being continuously maintained without releasing respective glass substrates from the clamping situation, after the grinding according to  claim 9 .  
     
     
         13 . The method for processing a glass substrate according to  claims 9  to  12 , wherein said buffer sheet to be used is a buffer sheet defined in  claims 2  to  7 .  
     
     
         14 . The method for processing a glass substrate according to  claims 9  to  12 , wherein 
 said buffer sheet to be used has a convex portion at an inner periphery or an outer periphery of the buffer sheet,  
 the buffer sheet and the glass substrate are stacked such that the convex portion reaches to the inner peripheral edge or the outer peripheral edge of the glass substrate, and are subjected to the grinding, and  
 a portion of the inner periphery or the outer periphery of the glass substrate, corresponding to said convex portion, is left as an insufficiently ground portion.  
 
     
     
         15 . A glass substrate, wherein the glass substrate is obtained by the processing methods according to  claims 8  to  12 .  
     
     
         16 . A glass substrate, wherein the glass substrate is obtained by the method for processing the glass substrate according to claims  13 .  
     
     
         17 . A glass substrate, wherein the glass substrate is obtained by the method for processing the glass substrate according to  claim 14  and wherein a mark is formed at an inner peripheral edge and/or an outer peripheral edge of the glass substrate by insufficiently grinding the glass substrate.