| 摘要 |
PURPOSE:To enable to obtain easily a distortionless lens, by a method wherein a gate part through which a molten molding material is entered into a molding cavity for the lens directly or through a runner from a sprue is made into a circular and flat-platelike space. CONSTITUTION:A runner R and cavity C are connected by a circular and flat- platelike space with each other. Although the circular and flat-platelike space part is called a buffer gate B, which is in about an identical thickness with the cavity C and the diameter of which is made into 0.4-0.6 times of that of the cavity C, a part through which molten resin flows out into the cavity C from the buffer gate B shows a shape like the moon at the time of a partial eclipse of the moon by overlapping a part of the buffer gate B to the cavity C and a length of a circular arc 3 to be formed by overlapping to the cavity C falls within a range varying from one tenth to one sixth of the whole circumference of the cavity C. Sudden turbulence of molecular orientation of the molten resin to be injected through the runner R is mitigated and molecular orientation at the time of injection of the molten resin into the cavity C is adjusted also, by providing the buffer gate B. |
