Method of improving spin cast lenses

Details Method of improving spin cast lenses Method of improving spin cast lenses

1985-02-12

1986-05-20

Lowe, James

Plastic and nonmetallic article shaping or treating: processes

Optical article shaping or treating

Rotational molding

264311, 425218, 425426, 425460, 425808, B29D 1100

Patent

active

045900183

ABSTRACT:
Spin casting is accomplished by spinning a liquid monomer in a rotating concave mold. Centrifugal force provides the concave lens curvature. Insufficient wetting at the edge of the lens mold results in imperfect lenses. Three methods have been found to increase the wetting. (1) Time: If the rotating monomer is allowed to remain in the mold, some improvement in wetting will occur due to liquid creep. Receding contact angles are lower than advancing contact angles. Two methods have been found to provide receding contact angles. (1) A wiper forces the liquid outward to the edge of the mold. (2) High rotational speed will provide sufficient centrifugal force to move the liquid monomer outward to the edge. Reducing the rotational speed will result in a receding contact angle.

REFERENCES:
patent: 2880109 (1959-03-01), Current et al.
patent: 3408429 (1968-10-01), Wichterle
patent: 3660545 (1972-05-01), Wichterle
patent: 3699089 (1972-10-01), Wichterle
patent: 4517139 (1985-05-01), Rawlinge et al.

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