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Technique to provide a molding die which can easily release a minute optical element in a state of favorable surface accuracy, while bending or rupture of a gate portion attached to the optical element is prevented. By making a first outer circumferential transfer surface 21A of a fixed die 20 and a

Technique to provide a molding die which can easily release a minute optical element in a state of favorable surface accuracy, while bending or rupture of a gate portion attached to the optical element is prevented. By making a first outer circumferential transfer surface 21A of a fixed die 20 and a first gate-forming surface 31A flush with each other, a notch shape is not formed on a portion M1 connecting an outer circumferential portion FL on the fixed die 20 side and a gate portion GP. Furthermore, by pushing out the runner portion RP at the same angle as a taper angle α of a side-surface transfer surface 23A on a second gate-forming surface 32A side, bending deformation or the like of the gate portion GP which can occur when being pushed out to a direction perpendicular to a mold mating surface PL1 can be prevented.

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1. A method for manufacturing an optical element with molding by using a molding die having a fixed die and a movable die, wherein the method comprises: providing the fixed die for forming a first optical surface of an optical element and a first outer circumferential surface extending around the fi

1. A method for manufacturing an optical element with molding by using a molding die having a fixed die and a movable die, wherein the method comprises: providing the fixed die for forming a first optical surface of an optical element and a first outer circumferential surface extending around the first optical surface;providing the movable die for forming a second optical surface of the optical element, a second outer circumferential surface extending around the second optical surface, and an outer circumferential side surface connecting the first outer circumferential surface and the second outer circumferential surface,wherein:the fixed die has a first optical transfer surface forming the first optical surface, a first outer circumferential transfer surface forming the first outer circumferential surface, a first gate-forming surface forming a gate portion, and a first flow channel-forming surface forming a flow channel portion;the movable die has a second optical transfer surface forming the second optical surface, a second outer circumferential transfer surface forming the second outer circumferential surface, a side-surface transfer surface forming the outer circumferential side surface, a second gate-forming surface forming the gate portion, and a second flow channel-forming surface forming the flow channel portion;the first and second outer circumferential transfer surfaces are a pair of surfaces parallel to mold mating surfaces of the fixed die and the movable die, and the first outer circumferential transfer surface and the first gate-forming surface are on the same plane;the fixed die and the movable die have an outer circumference-forming portion constituted by the first and second outer circumferential transfer surfaces and the side-surface transfer surface, and a gate-forming portion constituted by the first and second gate-forming surfaces;a portion connecting the outer circumference-forming portion and the gate-forming portion has an R-shape on a cross-section parallel to the mold mating surfaces;the side-surface transfer surface has a taper angle narrowing on the second outer circumferential transfer surface side;the movable die has a pushing-out mechanism for pushing out the flow channel portion of the optical element; andthe pushing-out mechanism has a pushing-out pin pushing out to the first flow channel-forming surface side of the movable die at the same angle as a taper angle of a surface in the side-surface transfer surface on the second gate-forming surface side. 2. The method for manufacturing an optical element according to claim 1, comprising pushing out the flow channel portion in the molding product at the same angle as a taper angle of the surface in the side-surface transfer surface on the gate-forming surface side by using the pushing-out mechanism. 3. The method for manufacturing an optical element according to claim 1, wherein the second outer circumferential transfer surface and the second gate-forming surface are on the same plane at least up to an extension line which is from a portion connecting the first outer circumferential transfer surface and the first gate-forming surface and is perpendicular to the mold mating surface, and a depth of the outer circumference-forming portion and a depth of at least the connecting portion in the gate-forming portion are equal to each other. 4. The method for manufacturing an optical element according to claim 1, wherein: the gate-forming portion has at least any one of a depth and a width increasing as going from the outer circumference-forming portion side to a flow channel-forming portion side constituted by the flow channel-forming surface in the movable die; anda portion connecting the gate-forming portion and the flow channel-forming portion has an R-shape on a cross-section perpendicular to the mold mating surface. 5. The method for manufacturing an optical element according to claim 1, wherein assuming that an outer diameter of the outer circumference-forming portion is d, a width of the gate-forming portion is W, and an R radius of the R-shape is r, the following conditional expression is satisfied: d≦2.0 mmW≦d/2r≦d/4. 6. The method for manufacturing an optical element according to claim 1, wherein a ridge portion of the outer circumference-forming portion on the second outer circumferential surface side has an R-shape on a cross-section perpendicular to the mold mating surface. 7. The method for manufacturing an optical element according to claim 1, wherein: the gate-forming portion has a first transfer surface extending outward from the second outer circumferential transfer surface and parallel to the mold mating surface, and a second transfer surface extending outward from the first transfer surface and inclined with respect to the first transfer surface; anda portion connecting the first transfer surface and the second transfer surface has an R-shape on a cross-section perpendicular to the mold mating surface. 8. The method for manufacturing an optical element according to claim 1, wherein assuming that the taper angle of the side-surface transfer surface is a, the following conditional expression is satisfied: 0.1°≦+≦10°.