Surface casting onto a polycarbonate photochromic substrate
View Patent ↗A system and method for providing photochromic segmented multifocal optical lenses. A latex primer formulation is provided for effectuating adhesion of a surface casting composition onto a lens having a photochromic coating. The method provides efficient, cost effective production of durable photochromic segmented lenses, via secure adhesion of a surface casting layer onto a photochromic substrate while maintaining desirable optical characteristics. A composite optical lens is advantageously formed having a photochromic base lens, a primer composition bonded to a convex surface of said base lens, and a cured casting composition bonded to said primer composition layer. The cured casting formulation includes a segment region to impart multifocal qualities onto the resultant composite optical lens.
1. A method for producing a photochromic multifocal optical lens comprising the steps of:
providing a polycarbonate lens having a photochromic coating on an SV front surface of said lens and applying a primer formulation to the photochromic coating of the lens and drying same to produce a primer coated photochromic lens;
providing a mold assembly including a segment region and applying a surface casting monomer solution into the mold to form a casting layer and wetting out the segment region, wherein the monomer solution includes about 75 weight % of bisphenyl A (meth)diacrylate with the balance comprising a mixture of benzyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate and 2-phenoxyethy (meth)acrylate; and about 1 part per hundred monomer (phm) of 1-hydroxy cyclohexyl phenyl ketone;
placing the primer coated photochromic lens into the mold, such that the front surface of the primer-coated lens contacts the casting layer; and
curing the casting layer to produce a segmented photochromic optical lens wherein the primer provides secure adhesion of the casting layer to the photochromic coating.
2. The method of claim 1 , wherein the step of curing includes ensuring that an even gap exists between a mold surface and the front surface of the lens.
3. The method of claim 1 , wherein the primer formulation is comprised of:
about 35 parts by weight of polyurethane latex;
about 15 parts by weight of 2-butoxy ethanol;
about 50 parts by weight of deionized water; and
about 5 parts by weight of a coupling agent.
4. The method of claim 3 , wherein the coupling agent comprises a precondensed solution of:
about 10 parts by weight of glycidoxypropyltrimethoxysilane;
about 10 parts by weight of acryloxypropyltrimethoxysilane;
about 0.5 parts by weight of 0.1N HCL;
about 0.5 parts by weight of aluminum acetylacetonate; and
about 1.0 parts by weight of diacetone alcohol.
5. The method of claim 1 , wherein the monomer solution is comprised of:
about 8 weight % of benzyl (meth)acrylate;
about 9 weight % of tetrahydrofurfuryl (meth)acrylate; and
about 8 weight % of 2-phenoxyethy (meth)acrylate.
6. The method of claim 1 , wherein the mold comprises an ultraviolet light transparent mold assembly.
7. The method of claim 6 , wherein the step of curing further comprises:
exposing the mold assembly to at least one ultraviolet light for about 10 to 30 seconds, with or without heat.
8. The method of claim 7 , further comprising the step of thermally curing the assembly after at least one UV exposure.
9. The method of claim 1 , wherein primer is applied to the photochromic coating of the lens by spin coating.