Method for dividing brittle-material substrate

Abstract

A cutter edge is pressed against a brittle-material substrate so that a protruding portion of the cutter edge is positioned between a first edge of the brittle-material substrate and a side portion of the cutter edge and that a side portion of the cutter edge is positioned between the protruding portion of the cutter edge and a second edge of the brittle-material substrate. A scribe line is formed by a scratch between a first position closer to the first edge of the first and second edges and a second position closer to the second edge of the first and second edges. After the formation of the scribe line, a crack is extended in a thickness direction from the second position toward the first position along the scribe line, thus forming a crack line.

1 . A method for dividing a brittle-material substrate, the method comprising:
 preparing a brittle-material substrate made of grass material and including a surface and having a thickness direction perpendicular to said surface, said surface being surrounded by a perimeter including first and second edges opposite to each other;   pressing a cutter edge against said surface of said brittle-material substrate, said cutter edge including a protruding portion and a side portion extending from said protruding portion and having a convex shape;   forming by plastic deformation, a scribe line having a groove shape involving no vertical crack, said scribe line being formed between a first position closer to said first edge and a second position closer to said second edge on said surface of said brittle-material substrate by causing said cutter edge pressed in said pressing to slide on said surface of said brittle-material substrate;   after said forming a scribe line, forming a crack line by extending a crack of said brittle-material substrate in said thickness direction from said second position toward said first position along said scribe line; and   dividing said brittle-material substrate along said crack line;   
       wherein said forming a scribe line comprises causing said cutter edge to slide from said first position beyond said second edge, and
 said forming a crack line is started by said cutter edge passing through said second edge. 
 
     
     
         2 . The method for dividing a brittle-material substrate according to  claim 1 , wherein
 said cutter edge includes first to third surfaces adjacent to each other, a vertex at which said first to third surfaces meet, and a ridge formed by said second and third surfaces, and   said protruding portion of said cutter edge comprises said vertex, and said side portion of said cutter edge comprises said ridge.   
     
     
         3 . The method for dividing a brittle-material substrate according to  claim 1 , wherein
 said cutter edge has a shape of a cone including a vertex and a conical surface, and   said protruding portion of said cutter edge comprises said vertex, and said side portion of said cutter edge is formed along an imaginary line extending from said vertex on said conical surface.   
     
     
         4 . The method for dividing a brittle-material substrate according to  claim 1 , wherein said forming a scribe line comprises
 displacing said cutter edge from said first position to said second position,   increasing a load to be applied to said cutter edge at said second position, and   causing said cutter edge to which the increased load has been applied to slide beyond said second edge.   
     
     
         5 . The method for dividing a brittle-material substrate according to  claim 1 , wherein said forming a crack line comprises applying a stress between said second position and said second edge after said forming a scribe line. 
     
     
         6 . The method for dividing a brittle-material substrate according to  claim 5 , wherein said forming a scribe line is performed by forming a scribe line reaching said second edge. 
     
     
         7 . The method for dividing a brittle-material substrate according to  claim 5 , wherein said applying a stress comprises causing said cutter edge pressed on said surface of said brittle-material substrate to slide between said second position and said second edge on said surface of said brittle-material substrate. 
     
     
         8 . The method for dividing a brittle-material substrate according to  claim 5 , wherein said applying a stress comprises applying laser light between said second position and said second edge on said surface of said brittle-material substrate.