Patent ID: 6325950
Filing Date: 2001-12-04
Classification: B29C,B29D,B29K,B29L

Abstract:
A method for producing optical disc substrates having a diameter of from 80 to 120 mm and a thickness of from 0.5 to 0.7 mm, comprising charging and injection molding or injection-compression molding an acrylic resin for the substrates into the cavity of a mold at a resin filling time of not greater than 0.08 seconds, wherein a melt viscosity of the resin is within the range of from 3 to 6 Pa.multidot.s, within the period of time of from the start of a resin injection through the tip of the nozzle of the injection-molding machine to the arrival of the resin at the deepest end of the cavity of the mold, wherein the temperature of the resin charged into the cavity near/around the inner surface of the cavity is higher than the flow-stopping point of the resin, the point at which the resin being in a gum flat range changes to be within a transition range, within the period of time of from the start of resin injection through the tip of the nozzle of the injection-molding machine to the arrival of the resin at the deepest end of the cavity.