| 摘要 |
PROBLEM TO BE SOLVED: To provide an injection molding method in order to laminate with high accuracy a coloring layer of prescribed layer thickness on a prescribed range on a main material layer in a peripheral wall of a preform.SOLUTION: An injection molding method includes: shortening a delay time of supply start of second resin and making supply speed of the second resin high compared to supply speed of main material resin so as to enable flow of letting the delaying second resin pierce into and further break through a central part of the preceding main material resin in a confluent passage (19) or a cavity (4) of a metallic mold (1), and laminating and forming a second resin layer comprising the second resin on the outer peripheral surface and inner peripheral surface of a peripheral wall; or moving a slide position of a tip (20p) of a shut-off pin (20) so as to be gradually changed to an opening direction or a blockade direction near a second confluent part (17b), and changing a layer thickness of the second resin layer in a gradation state in an axial direction; or periodically varying the slide position of the tip (20p) near the confluent part (17b), and periodically varying an extent of an opening state of the confluent part (17b) so as to periodically change layer thickness of the second resin layer in the axial direction. |
