Process for producing opthalmic lenses with gradated photochromi

Details Process for producing opthalmic lenses with gradated photochromi Process for producing opthalmic lenses with gradated photochromi

1978-02-24

1979-04-17

Bashore, S. Leon

Glass manufacturing

Processes

With chemically reactive treatment of glass preform

65 33, 65111, 65115, 65119, 65DIG2, 106 52, 106DIG6, C03C 1500, C03B 3100

Patent

active

041498682

ABSTRACT:
A method of treating ophthalmic quality lenses or lens blanks that produces a reversible progressive local variation in phototropic behavior with a continuous variation in transmissivity. The lens or lens blank is composed of a potentially phototropic glass containing all the necessary ingredients including uniformly dispersed silver halide particles therein to develop a phototropic behavior during the heat treatment of the present method. The steps of the present method include mounting the lens or lens blank in carrier means, heating the lens or lens blank thus mounted in a heat treatment furnace at a temperature sufficient to develop the phototropic behavior of the potentially phototropic glass. Characteristically the required heat treatment temperature to develop this phototropic behavior is one which exceeds the strain point of the glass but not the softening point thereof. The heat treatment includes the further step of maintaining selected portions of the lens or lens blank at a temperature to substantially inhibit the development of the phototropic behavior and thus produce a progressive gradient of transmissivity. The particular improvement of the present invention includes heat sinking the selected portion of the lens to be maintained at a temperature which substantially inhibits the development of phototropic behavior by utilizing the latent heat of transformation of a material which has at least one phase transformation temperature below the temperature required for development of phototropic behavior. This heat sinking is accomplished by positioning the heat sinking material proximate to the portion of the lens or lens blank in which the temperature is to be maintained to substantially inhibit the development of phototropic behavior. This is preferably accomplished by establishing a path of heat conduction between the heat sinking material and the selected portion of the lens or lens blank.

REFERENCES:
patent: 2984943 (1961-05-01), White
patent: 4072490 (1978-02-01), Illig

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