Abstract: A method of fabricating an optical film is provided. The method includes nipping a film composed of a molten polycarbonate resin extruded in a film-forming manner from a die attached to an extruder, between a temperature-preset molding roll having an engraving pattern on the surface thereof and a temperature-preset elastic roll, and thereby transferring the engraving pattern onto the film; and allowing the film having the engraving pattern transferred thereon to travel around the molding roll, and then separating the film from the molding roll. In the method, a preset value of a surface temperature of the molding roll is adjusted within a range of Tg+20° C. or above and Tg+45° C. or below, where Tg is a glass transition temperature of the film, and a preset value of a surface temperature of the elastic roll is adjusted to Tg or below.

Abstract: An improved method for forming a disc substrate having a bottomed centering hole for rotating and driving the disc. The method includes injecting synthetic resin into a mold cavity formed by a first and second metal molds to form the substrate, and punching at least part of the centering hole by a movable member protruded into the mold cavity to form a through-hole. A stamper containing digital information is held in place inside the mold cavity by its inner circumference by means of a vacuum or a magnet.

Abstract: A metal mold device for molding a disc substrate formed by molding a synthetic resin material and having a raised portion on the inner surface of the disc substrate, includes a fixed metal mold and a movable metal mold for defining together a mold cavity for molding the disc substrate. A mold releasing resistance in the form of suitably sized projections or recesses, is provided at a portion of the fixed metal mold or the movable metal mold mating with the outer rim of the disc substrate being molded or at the outer peripheral surface of the raised portion to permit an as-molded disc substrate to be released easily and reliably from a stamper bearing a pattern of pits and lands or pre-grooves and to prevent molding distortions from being produced in the disc substrate being molded.

Abstract: A metal mold device for molding a substrate includes a fixed metal mold, a movable metal mold mounted facing the fixed metal mold for being moved towards and away from the fixed metal mold and for defining a mold cavity between it and the fixed metal mold, a stamper mounted on at least one of the fixed metal mold or the movable metal mold and arranged within the mold cavity, a positioning unit provided on the metal mold on which the stamper is mounted for positioning the loading position of the stamper, and a stamper supporting unit provided on the metal mold on which the stamper is mounted for supporting the stamper by suction. The stamper is positioned by the positioning member and held under suction by the stamper suction unit so that it may be mounted in position on the fixed metal mold or the movable metal mold to permit a disc substrate to be molded highly accurately.

Abstract: A method for molding a substrate for optical information record carrier is disclosed which results in small double refraction with superior transfer characteristics of a surface of a stamper. The method comprises the steps of injecting molten resin into a cavity formed by a stationary mold and movable mold under application of mold clamp pressure between said molds, releasing the mold clamp pressure at predetermined timing after injection of said molten resin is completed and the molten resin is partially solidified, holding said resin in the molds under the released mold clamp pressure condition until the resin is solidified, and taking out the molded substrate from the molds.

Abstract: An optical information record medium is disclosed in which an optical information record layer is formed on a substrate made of a polycarbonate resin. The polycarbonate resin is purified to remove the residual chlorine in the resin enough to form the substrate containing no more than 1.0 ppm of chlorine ion. By reducing the residual chlorine ion in the polycarbonate substrate, anticorrosion characteristics of the optical information record medium are greatly improved.