Metal mold and stamper for injection molding of a plastic disc for a high-density information recording carrier
AssigneeDaicel Chemical Industries, Ltd.
InventorsNorio Okabayashi, Yoshio Onizawa
Life of this patent
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Abstract
A metal mold to be used for injection-molding of a flat plastic disc. The flat, annular mold cavity has a substantially continuously increasing axial thickness away from the injection gate. The gate can be in the center or on the outer periphery of the mold. A split mold type is disclosed wherein at least one of the inner opposed surfaces tapers away from an imaginary flat center plane. Alternatively, a stamper having a tapering thickness can be used in a mold having parallel opposed inner surfaces.
Claims9
In a metal mold to be used for injection-molding a flat plastic disc having uniform thickness for a high-density information recording carrier by injecting molten resin into a flat and annular mold cavity, the improvement characterized in that an axial thickness of the flat and annular injection mold cavity is substantially continuously increased away from a gate at the center of the molding cavity outwardly from the gate to the mold cavity perimeter for injecting the molten resin into the center of the mold and forming a flat resin disc having uniform thickness when molten resin is injection molded in said cavity.
In a stamper to be disposed in a metal mold for injection-molding a flat plastic disc having uniform thickness for a high-density information recording carrier by injecting molten resin into a flat annular injection molding cavity, the improvement characterized in that a thickness of said stamper is continuously decreased radially outwardly away from an injection gate at the center of said mold cavity to the mold cavity perimeter for the molten resin for injecting molding flat disc having uniform thickness.
Dependencies are inferred from the claim text.