| 摘要 |
PURPOSE:To prevent generation of an optical defect such as birefringence in the case where optical molded body is molded. CONSTITUTION:In an injection mold device where a bushing 16 is provided on molds 11, 12 demarcating a cavity 13, a resin passage 22 communicating the cavity 13 with a gate 17 by passing through those is formed into the bushing 16, a valve disc 23 is inserted movably within the resin passage 22 with a play and the foregoing gate 17 is opened or closed with the valve disc 23, a small- diameter part 22a whose diameter is almost the same as that of the foregoing valve disc 23 is formed at a position close to the foregoing gate 17 so that the valve disc 23 becomes slidable. The title device is constituted so that a plurality of spiral groove 30 are formed in an outer circumferential part of the valve disc 23 or a circumferential wall part of the foregoing small-diameter part 22a at almost equal intervals and a spiral passage communicating the foregoing resin passage 22 and gate 1 7 with each other by fitting the foregoing valve disc 23 into the foregoing small-diameter part 22a at the time of release of the foregoing gate 17 is formed by the foregoing spiral groove 30. |
