Abstract: Disclosed are novel molding methods for injection molding thermoplastic lens elements and particularly adapted for the manufacture of steeply curved and/or thin-centered lenses.

Abstract: Disclosed are novel molding methods for manufacturing thin thermoplastic lenses and, in particular, minus ophthalmic lenses that have thickness of about 1 mm or less at the thinnest point thereof. The molding methods disclosed provide for lenses which lack any abrasion or polishing artifacts on the surface and also lack any negative fining marks below the nominal surface.

Abstract: A lens has two or more layered sections of thermoplastic material, and a substantially homogenous formation in which at least one of the layered sections has an active photochromic material present. The article is made by: forming a mould cavity from first and second mould halves; loading the mould cavity with a first thermoplastic material; curing or partially curing that material; changing the second mould half to define a subsequent mould cavity in which the cured or partially cured material is present; loading the subsequent mould cavity with a subsequent thermoplastic material; and completing any uncompleted curing of the first and subsequent thermoplastic materials. At least one of the thermoplastic materials is loaded with an active photochromic material.

Abstract: A lens has two or more layered sections of thermosetting material, and a substantially homogenous formation in which at least one of the layered sections has an active photochromic material present. The article is made by: forming a mould cavity from first and second mould halves; loading the mould cavity with a first thermosetting material; partially curing that material; changing the second mould half to define a subsequent mould cavity in which the partially cured material is present; loading the subsequent mould cavity with a subsequent thermosetting material; and curing the first and subsequent thermosetting materials. At least one of the thermosetting materials is loaded with an active photochromic material.

Abstract: A method and apparatus for molding and casting ophthalmic lenses includes a front surface die and a back surface die slidably and removably received in the bore of a molding or casting apparatus. Molding or casting compound is introduced by conventional means between the two dies, and the dies are urged together to impress the die surfaces on the compound as the compound is cured by thermal or chemical means. At least one of the dies includes at least one gate channel formed in the edge thereof parallel to the axis of the bore and extending from the optical forming surface to a point adjacent to the opposite, external die surface. In compression molding, the gate channel comprises a vent through which excess molding compound is discharged from the molding cavity as the dies are urged together. As the gated die is fully inserted in the bore, the gate channel opening to the exterior is sealed, thus limiting the discharge effect and controlling the thickness of the molded part.

Abstract: A method and apparatus for the fabrication of optical lenses by injection/compression molding of thermoplastic includes a plurality of sleeves, each having a bore therethrough, and a plurality of mold inserts dimensioned to be received in the bore with minimal clearance for sliding fit. The mold inserts each include a precision optical surface adapted to form a front or back surface of a lens. A selected pair of mold inserts are placed in the bore of a sleeve with front and back surface forming optical surfaces in confronting relationship to define a mold cavity, and the assembly is heated to a temperature above the glass transition temperature of the thermoplastic to be molded. An injection port extends through the sleeve to the bore, and is positioned to inject thermoplastic that has been heated to a fluid state into the cavity. After injection of the thermoplastic, the mold inserts are compressed together, and excess thermoplastic is forced out of the mold cavity.