| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of a high-precision and inexpensive plastic lens, without causing a sink mark in the optical surface of the lens. SOLUTION: An injection molding machine being used, a time difference is set between the first-period injection and the second-period injection. On the occasion of the first-period injection, a movable-side core 22 forming the optical surface of the lens and an ejector pin 24 in the lower part of a sprue are made to rise in gearing so that a molten resin path 14 for the second-period injection can be shielded, and a first-period injection molded part 11 of the plastic lens is formed. On the occasion of the second-period injection, a molten resin in the central part of the sprue 16 is made to flow again, with the rise canceled, and the movable-side core 22 and the ejector pin 24 in the lower part of the sprue are lowered, with the lower part of the sprue 16 broken. The molten resin path 14 being opened thereby, a space to be a second-period injection molded part 12 of the plastic lens is formed under the first-period injection molded part 11 and the second-period injection molded part 12 is integrated with the first-period injection molded part 11. |
