Shaped plastic lenses and method for making the same
There is described a method for forming lenses having substantially no optical power. The method includes forming, via in situ polymerization, a layer of non-uniform thickness of an optically clear, high scratch-resistant polymeric material on the convex surface of the lens. The lenses provided by the method are characterized by having maximum thickness in the central region of the lens and gradually diminishing thickness radially towards the periphery of the lens.
1. A shaped plastic lens convex on one side and concave on the other side and having substantially no optical power comprising a first substantially uniformly thick layer of thermoplastic polymeric material, a second substantially uniformly thick layer of thermoplastic polymeric material and a third thermoplastic layer of non-uniform thickness and having high scratch resistance, said third layer having maximum thickness in the central region thereof and diminishing gradually in thickness radially toward the periphery thereof, wherein said second substantially uniformly thick layer forms said concave side of the lens and said third layer forms said convex side of the lens.
2. The shaped plastic lens as defined in claim 1 and further including a layer of a light-polarizing material positioned in said first layer of said lens.
3. The shaped plastic lens as defined in claim 2 wherein said first layer of thermoplastic material comprises cellulose triacetate or cellulose acetate butyrate and said second layer of thermoplastic material comprises polycarbonate, said light-polarizing layer being positioned between said cellulose triacetate or cellulose acetate butyrate layer and said polycarbonate layer and said polycarbonate layer forming said concave side of said lens.
4. The shaped plastic lens as defined in claim 3 wherein said polycarbonate layer of said lens comprises a colored layer of polycarbonate and a clear layer of polycarbonate having an outer surface of a high scratch-resistant material, said high scratch-resistant material forming said concave surface of said lens.
5. The shaped plastic lens as defined in claim 4 wherein said lightpolarizing layer is positioned closer to said convex side of said lens than to said concave side of said lens.
6. The shaped plastic lens as defined in claim 1 wherein said third layer comprises a polymer of a tetraethylene glycol methacrylate monomer and a dipentaerythritol pentacrylate monomer.
7. The shaped plastic lens as defined in claim 2 wherein said third layer comprises a polymer of a tetraethylene glycol methacrylate monomer and a dipentaerythritol pentacrylate monomer.
8. The shaped plastic lens as defined in claim 7 wherein said lightpolarizing layer is positioned closer to said convex side of said lens than to said concave side of said lens.
9. The shaped plastic lens as defined in claim 8 wherein said first layer of thermoplastic material comprises cellulose triacetate or cellulose acetate butyrate and said second layer of thermoplastic material comprises polycarbonate, said lightpolarizing layer being positioned between said cellulose triacetate or cellulose acetate butyrate layer and said polycarbonate layer.