| 摘要 |
PURPOSE:To accurately mold a thick lens having a large central thickness-to-peripheral thickness ratio with a simple constitution by a method wherein an annular core is provided in the molding chamber of a mold and material, the refractive index of which is the same as that of the core, is filled in the molding chamber. CONSTITUTION:Under the condition that a lower mold 4 and a lower mold sleeve 7 are lowered, an annular core 10 is placed on the stepped part 9 of the lower mold sleeve 7. In this case, the core 10 is arranged so as to bring its notched part 11 in line with the direction of a molding material inlet. In succession, the lower mold 4 together with the lower mold sleeve 7 is shifted to the molding surfaces of an upper mold 2 and of an upper mold sleeve 5 so as to be brought into close contact with each other in order to constitute a molding chamber 8. Plastic material 12, the refractive index of which is the same as that of the core 10, is injected from the molding mateiral inlet 6 in the molding chamber 8. The injected plastic material 12 is cooled through its portion in contact with the core 10 and its portion in contact with the lower mold 4. After a certain period of time, the lower mold 4 and the lower mold sleeve 7 are lowered in order to take a molded item out of the molding chamber 8. |
