INJECTION MOLDING METHOD PREVENTING GENERATION OF SURFACE DEFECTS AND METAL MOLDS FOR INJECTION MOLDING.

摘要

A metal mold (11) formed at an inner surface thereof with a heat insulating thin film (14) which is good in adhesion to and heat insulation of a molten resin (20) is combined with another metal mold (12) to form a metal mold cavity. The molten resin (20) injected into and filled in the metal mold cavity is prevented by the heat insulating thin film (14) from being cooled through the metal mold (11), so that a skin layer (23) preferentially grows on the side of the second metal mold (12). As a result, a volumetric shrinkage generated at the time of cooling and solidification of the molten resin (20) is preferentially offset by the skin layer (23) which separates from the metal mold (12) to eliminate generation of defects such as sink on surfaces of molded products. In addition, the heat insulating thin film (14) acts to reduce weld lines. <IMAGE>