METHOD FOR MANUFACTURING PREFORM FOR PRESS MOLDING, METHOD FOR MANUFACTURING OPTICAL ELEMENT AND APPARATUS FOR FLOWING MOLTEN GLASS

摘要

PROBLEM TO BE SOLVED: To provide a method for manufacturing a high quality preform for press molding by a hot molding method, an apparatus for allowing a molten glass to flow out which can be used in the above method and a method for manufacturing an optical element from the resultant preform. SOLUTION: The method for manufacturing a preform for press molding involves a step that a molten glass block which is obtained by allowing a molten glass to flow out from a flow outlet located at a nozzle end through a glass flow path in a nozzle to flow glass is separated and a step that the separated molten glass block is molded into the preform on a molding die. The nozzle for allowing glass to flow has a molten glass guide rod which is projected from the inside of the glass flow path to the outside of the flow outlet. The molten glass is allowed to flow from the glass flow path along the molten glass guide rod and a gas is sprayed on a molten glass surface for cooling acceleration. The nozzle for the effusion of glass is heated by heating means involving an induction heating means and the molten glass is allowed to flow from the glass flow outlet along the molten glass guide rod. COPYRIGHT: (C)2006,JPO&NCIPI