Method of molding optical element and optical element molding die

A method of obtaining an optical element by molding, the method comprising:

• preparing a die set including an upper die having an upper molding surface, a lower die having a lower molding surface, a side die in which a through hole serving as a side molding surface is formed, and a sleeve configured to accommodate the upper die, the lower die, and the side die;
• disposing a mold material on the lower molding surface after inserting the lower die into the through hole of the side die such that the lower molding surface is positioned in the through hole of the side die;
• heating the mold material disposed in the through hole of the side die;
• molding the optical element by press molding the mold material with the upper die and the lower die by pushing the side die upward using the lower die to integrally move the side die and the lower die with respect to the upper die and the sleeve in a state where a position of the lower molding surface in the through hole of the side die is maintained at a predetermined position;
• and
• pushing the optical element upward by raising the lower die with respect to the side die and the sleeve to move the lower molding surface in the through hole of the side die to a position which is higher than the predetermined position and at which a part of the optical element after molding protrudes from an upper surface of the side die,
• wherein:
• the lower die has a first surface having a first stepped shape, the side die has a second surface facing the first surface of the lower die, and the second surface has a second stepped shape which can be fitted into the first stepped shape of the first surface of the lower die,
• the pushing upward of the optical element includes switching an orientation of the second stepped shape of the side die with respect to an orientation of the first stepped shape of the lower die to an orientation in which the first stepped shape and the second stepped shape become fitted into each other, to move the lower molding surface in the through hole of the side die,
• one of the first surface and the second surface includes a protrusion portion, and the other of the first surface and the second surface includes a recess portion having a shape corresponding to a shape of the protrusion portion and a portion in which the recess portion is not formed,
• the press molding of the mold material is performed in a state where the portion in which the recess portion is not formed is in contact with the protrusion portion, and
• the pushing upward of the optical element includes rotating one of the lower die and the side die to bring the recess portion into contact with the protrusion portion to move the lower molding surface in the through hole of the side die.