Disk substrate, molding apparatus for injection-molding it and disk substrate pick-up robot

Abstract

It is possible to obtain a disk substrate in which an edge of a center hole is free of flash. The disk substrate ( 23 ) in which the center hole ( 24 ) is provided with a straight portion ( 24 a ) and a tapered portion ( 24 b ), and an edge on the side of a signal transfer surface ( 22 ) of the tapered portion ( 24 b ) is provided with an R surface or C surface ( 24 c ), a mold apparatus optimum for molding the disk substrate ( 23 ), and a disk taking-out apparatus.

1 . A disk substrate to which signals are transferred by injection molding, said disk substrate comprising a center hole, and an edge with flash reduced to zero or suppressed to equal to or less than 10 μm in height at least on the signal transfer surface side of said center hole.  
     
     
         2 . A disk substrate as set forth in  claim 1 , wherein at least said edge of said center hole is provided with a first R surface or a first C surface.  
     
     
         3 . A disk substrate as set forth in  claim 1 , comprising a straight portion with a hole diameter equal in direction with the axial direction, said straight portion provided on the side opposite to said signal transfer surface side of said center hole, and a tapered portion with a hole diameter gradually enlarged toward said signal transfer surface, said tapered portion provided between said straight portion of said center hole and said signal transfer surface.  
     
     
         4 . A mold apparatus for injection molding a disk substrate, comprising a cavity into which a molten resin is injected through a sprue and a recessed form gate, and a signal transfer stamper disposed on the fixed die side of said cavity, said mold apparatus comprising a projected portion for molding said recessed form gate provided at the tip of said sprue, a recessed portion for molding said recessed form gate provided oppositely to said projected portion at the tip of a recessed form gate cutter disposed on the movable die side, and a center hole molding portion provided at the outer circumference of said sprue.  
     
     
         5 . A mold apparatus for injection molding a disk substrate as set forth in  claim 4 , wherein said center hole molding portion comprises a first R surface molding portion or a first C surface molding portion for molding a first R surface or a first C surface at an edge on the signal transfer surface side of a center hole of said disk substrate injection molded in said cavity.  
     
     
         6 . A mold apparatus for injection molding a disk substrate as set forth in  claim 4 , wherein said center hole molding portion comprises a straight molding portion for molding a straight portion with a hole diameter equal in direction with the axial direction on the side opposite to the signal transfer surface side of said center hole of said disk substrate injection molded in said cavity, and a taper molding portion for molding a tapered portion with a hole diameter gradually enlarged toward the signal transfer surface side between said straight portion of said center hole of said disk substrate injection molded in said cavity and said signal transfer surface.  
     
     
         7 . A mold apparatus for injection molding a disk substrate as set forth in  claim 4 , wherein the advance amount of said recessed form gate cutter is not less than the thickness of said recessed form gate and is not more than the recessed form gate thickness plus 0.5 mm.  
     
     
         8 . A mold apparatus for injection molding a disk substrate as set forth in  claim 6 , wherein the position of cutting said recessed form gate by said recessed form gate cutter is set at a position equal to the hole diameter of said straight portion of said center hole.  
     
     
         9 . A mold apparatus for injection molding a disk substrate as set forth in  claim 8 , wherein said recessed form gate cutter comprises a second R surface molding portion or a second C surface molding portion for molding a second R surface or a second C surface at the edge on the side opposite to the signal transfer surface side of said center hole, at the tip of an outer circumferential portion of said recessed portion.  
     
     
         10 . A mold apparatus for injection molding a disk substrate as set forth in  claim 6 , wherein the position of cutting said recessed form gate by said recessed form gate cutter is set at a first position equal to the hole diameter of said straight portion of said center hole, and at a second position disposed on the inside of said first position and smaller in diameter than said first position.  
     
     
         11 . A mold apparatus for injection molding a disk substrate as set forth in  claim 10 , wherein said recessed form gate cutter comprises a second R surface molding portion or a second C surface molding portion for molding a second R surface or a second C surface at the edge on the side opposite to the signal transfer surface side of said center hole, at the tip of an outer circumferential surface of said recessed portion.  
     
     
         12 . A disk substrate taking-out apparatus comprising: 
 a mold apparatus comprising a cavity provided between a fixed die and a movable die, a signal transfer stamper disposed on said fixed die side of said cavity, and a recessed form gate cutter disposed on said movable die side, wherein a molten resin is injected into said cavity through a sprue and a recessed form gate to injection molding a disk substrate, and gate cutting is conducted from said movable die side by said recessed form gate cutter; and    a robot for taking out from said movable die said disk substrate released from said fixed die together with said movable die by the opening of said movable die after injection molding, said robot comprising a means for discharging a sprue and gate remaining resin to said movable die side relative to said disk substrate.    
     
     
         13 . A disk substrate taking-out apparatus as set forth in  claim 12 , wherein said discharging means is provided with an air jet nozzle.