US 4,022,855 A · Method for making a plastic optical element having a gradient index of refraction

Abstract

A centrifugal molding method is provided for making a plastic lens having a gradient index of refraction. A reusable silicone rubber mold is placed in a rotatable mold carrier and two copolymerizable monomer compositions containing monomers having different indices of refraction are combined in the mold to form a polymerization mixture which has an index of refraction varying radially outward from its axis of rotation. The first monomer composition is placed in the mold and, while the mold is rotating sufficiently to force the first monomer composition to the outside edge of the mold, a second monomer composition is introduced via hypodermic injection into the center of the mold. The speed of rotation is reduced and the two monomer compositions diffuse one into the other in a controllable manner. Ultraviolet exposure, either directly on the mold or variably through a photographic mask with varying density, modifies the diffusion by initiating polymerization and increasing the viscosity of the monomer compositions. Finally the monomer compositions in the mold are completely polymerized by heat curing in an oven.

Claims14

Dependent claims

A method of fabricating a plastic optical element having a gradient index of refraction, said method comprising:

a. providing first and second copolymerizable monomer compositions each having a different index of refraction;
b. introducing said compositions concurrently into an element cavity of a mold over a period of time and at respective introduction rates such that the proportion of said first composition introduction to said second composition introduction is less at the end of said period than at the beginning of said period;
c. rotating said mold on a central axis of its cavity at a speed sufficient to obtain centrifugal distribution of said compositions during at least a portion of said period so that the index of refraction of the composite mixture is said cavity varies gradiently, radially outwardly from the central axis;
and
d. polymerizing said mixture to produce a shaped optical element having a gradient index of refraction.

2 more elements

A method of fabricating an optical element having a gradient index of refraction, said method comprising:

a filling a mold having a mold cavity with a polymerization mixture comprising two copolymerization compositions, each composition respectively having a different index of refraction, in a manner such that the volumetric ratio of said compositions in the mixture varies during the filling step;
and rotating the mold about a central mold axis during at least a part of the filling step at a speed sufficient to obtain centrifugal distribution of said mixture thereby forming a gradient index of refraction in a polymerization mixture;
and
b. polymerizing the mixture to produce a shaped optical element having a gradient index of refraction in a direction generally radial to the axis of rotation of said mold.

1 more element

Dependencies are inferred from the claim text.

Method for making a plastic optical element having a gradient index of refraction

Life of this patent

Method for making a plastic optical element having a gradient index of refraction

Life of this patent

Abstract

Claims14