Abstract: A method for manufacturing a glass substrate for a magnetic disk involving press-molding a heated glass material in an inside space of a molding die comprising a pair of dies, each having a predetermined processing plane, and a barrel die for slidably guiding the dies while forming an outer circumference of the glass material joined to both principal surfaces corresponding to the dies as a molding-free face, cooling the press-molded glass substrate and forming a predetermined through-hole in a central portion of the glass substrate.

Abstract: A molded glass substrate for a magnetic disk is manufactured in the following manner: press-molding a heated glass material in the inside space of a molding die including a pair of dies, each having a predetermined processing plane, and a barrel die for slidably guiding the dies while forming the outer circumference of the glass material joined to both principal surfaces corresponding to the dies as a molding-free face; cooling the press-molded glass substrate; and forming a predetermined through-hole in the central portion of the glass substrate. This method enables manufacturing that prevents generation of industrial waste, such as glass power, abrasive, and solvent, as much as possible.

Abstract: A method for making optical preforms of optical elements without residual stress or distortion is provided. In this method, an optical material is supplied between upper and lower molds. The upper mold has a plurality of recesses arranged in a predetermined pitch, and each recess corresponds to a first surface shape of the optical element. The lower mold has a plurality of recesses facing the recesses of the upper mold and each recess of the lower mold corresponds to a second surface shape of the optical element. The supplied optical material is pressed between the upper and lower molds to be a set of optical preforms. The set of optical preforms is processed by die punching or tool cutting to separate each optical preform from the set of optical preforms. Each optical preform is used for producing an optical element by further pressing. Alternatively, optical element can be formed directly by the press molding process.

Abstract: Optical material, which was already roughly molded, is deposited into a space defined by a top mold, a bottom mold and a drum mold, and is then heated, pressed and molded, thus providing an optical element. By controlling the rate of plastic deformation of the optical material so as to prevent the material from entering clearance sections between the outside diameter of the top mold or of the bottom mold and the inside diameter of the drum mold, an optical element of high precision with no burr nor strain is provided at low cost.

Abstract: A method is provided for controlling molding conditions of resin in the manufacture of articles such as optical lenses, which includes the steps of filling resin in a metal mold held at a temperature lower than a glass transition temperature of the resin, and then pressurizing the resin under comparatively high pressure so as to expedite hardening of the resin by raising its glass transition temperature, then reducing the pressurization of the resin to comparatively low pressure, and increasing, generally in association, the temperature of the mold cavity surface higher than the glass transition temperature of the resin so as to form a molten layer on a front face of the resin surface, and finally raising the pressurization of the resin to a medium pressure and lowering, generally in association, the cavity surface temperature of the metal mold so as to reduce the temperature for the withdrawal of the product.