Gasket for molding plastic lens

A method for manufacturing a spectacle plastic lens, including the steps of

• forming a spectacle plastic lens molding mold by incorporating, in a gasket, a first mold with a lens molding surface that forms one lens surface of the spectacle plastic lens and a second mold with a lens molding surface that forms the other lens surface of the spectacle plastic lens to be spaced apart from each other at a predetermined gap, and
• filling a lens raw material into a cavity of the spectacle plastic lens molding mold, and curing the lens raw material,
• characterized in that the gasket includes a cylindrical gasket main body,
• in a portion where at least one of the first mold and the second mold is to be incorporated, an inner circumferential surface of the gasket main body has an inner diameter smaller than an outer diameter of said one mold, and a taper surface that spreads toward an opening side of the gasket main body, and
• the incorporating step comprises the steps of elastically deforming the gasket main body in the diameter-enlarging direction, holding said one mold by pressing a circumferential surface of said one mold in a diameter-reducing direction with a restoring force of elastic deformation, and
• in holding said one mold, causing the taper surface to come into strongest contact with a lens molding surface side circumferential edge of said one mold;
• and
• sealing portions in the vicinity of the lens molding surface side circumferential edge of said one mold onto the taper surface with a leakage monomer throughout the entire circumference thereof by stably gathering the leakage monomer in a gap formed between the taper surface and the lens molding surface side circumferential edge of said one mold.

A method for manufacturing a spectacle plastic lens, comprising the steps of

• forming a spectacle plastic lens molding mold by incorporating, in a gasket, a first mold with a lens molding surface that forms one lens surface of the spectacle plastic lens and a second mold with a lens molding surface that forms the other lens surface of the spectacle plastic lens to be spaced apart from each other at a predetermined gap, and
• filling a lens raw material into a cavity of the spectacle plastic lens molding mold, and curing the lens raw material,
• characterized in that the gasket includes a cylindrical gasket main body and an elastic projecting band which integrally projects on an inner circumferential wall of the gasket main body throughout an entire circumference,
• the projecting band includes a ring-like proximal end portion which projects from the inner circumferential wall of the gasket main body to extend in a direction substantially perpendicular to an axial direction of the gasket main body, a tapered distal end portion which extends to incline with respect to the axial direction of the gasket main body, and a bent portion bend-connecting the proximal end portion and the distal end portion,
• the proximal end portion flexes more than the distal end portion around the bent portion as a border when pushed from the distal end portion side [M.Y1] downward along the axial direction of the gasket main body,
• the incorporating step comprises the steps of elastically deforming the gasket main body in the diameter-enlarging direction,
• holding at least one of the first mold and the second mold by pressing a circumferential surface of said one mold in a diameter-reducing direction with a restoring force of elastic deformation, and
• when holding said one mold, bringing a vertex of the distal end portion into linear contact with the lens forming surface of said one mold while the distal end portion undergoes a smaller flexure in a direction perpendicular to the axial direction of the gasket main body than a flexure undergone by the proximal end portion in the axial direction of the gasket main body.