MOLDING DIE ASSEMBLY FOR INJECTION MOLDING OF SYNTHETIC RESIN CONTAINER LID

PROBLEM TO BE SOLVED: To provide a molding die assembly which avoids damage of a thin ribbon plate part in a first molding die member as much as possible by improving the molding die assembly including: the first molding die member which has a thin ribbon plate part of a circular-arc shape or an annular shape defining a void in a container lid; and a second molding die member which has an annular tip surface and in which at least a part of the tip surface is made to oppose an extension end surface of the thin ribbon plate part in the first molding die member with a minute space.SOLUTION: At least a part of a region, where the extension end surface of the thin ribbon plate part 24 in the first molding die member 14 and a tip surface of the second molding die member 16 are arranged to face each other at a minute space, is made to be a form for preventing displacement of the extension end surface of the thin ribbon plate part 24 in the first molding die member 14 to the outside in a radius direction by cooperating with each other.