High adhesion acrylate coatings for a photochromic ophthalmic lens
View Patent ↗A method and coating used to prepare a photochromically-enabled bifocal ophthalmic lens. The coating is a high adhesive strength acrylate-based coating that contains a small quantity of a polycarbonate-based TPU. The coating is applied to produce an intermediate imbibable bifocal surface. A photochromic solution is subsequently imbibed by contact with the bifocal surface.
1. A method for forming a photochromically-enabled bifocal ophthalmic lens by incorporating a thermoplastic polyurethane (TPU) therein, comprising the steps of:
injecting molten thermoplastic polycarbonate (PC) resin into an edge-gated cavity of an injection molding machine having a vertical equipment axis to provide a lens substrate;
applying an acrylate-based coating composition onto the lens substrate which cures to form an imbibable bifocal surface while still in the injection molding machine; and
imbibing a photochromic dye solution into the surface;
wherein the acrylate-based composition contains an adhesion enhancer comprising a TPU so that coating-to-substrate integrity is maintained following said imbibing step.
2. The method of claim 1 , wherein said injecting step comprises providing a single vision (SV) lens substrate, and said applying step comprises overmolding.
3. The method of claim 1 , wherein said injecting step comprises providing a bifocal lens substrate.
4. The method of claim 1 , wherein said applying step comprises:
depositing an unpressurized full metered charge of the composition on to the upwardly-facing convex surface of the lens substrate; and
clamping down an upper mold half to form a bifocal lens cavity.
5. The method of claim 1 , wherein the coating composition comprises at least 90% by weight of a blend of acrylate-based thermoset materials, and less than 5 phm TPU parts per hundred parts of monomer (phm).
6. The method of claim 5 , wherein the coating composition is devoid of dyes which are selected from regular dyes, photochromic dyes, dichroic dyes and a combination thereof.
7. The method of claim 5 , wherein the coating composition comprises less than about 2 TPU phm, wherein the TPU is a polycarbonate-based TPU.
8. The method of claim 5 , wherein the TPU is an aliphatic polycarbonate-based TPU.
9. The method of claim 5 , wherein the photochromically-enabled bifocal ophthalmic lens has an % T initial above about 80.
10. The method of claim 5 , wherein the photochromically-enabled bifocal ophthalmic lens has a % T dark around 20.
11. The method of claim 1 , wherein said applying step comprises:
formulating the coating composition by dissolving a metal salt and the TPU in a solvent blend comprising:
(1) a monofunctional (meth)acrylate;
(2) a multifunctional (meth)acrylate;
(3) a difunctional (meth)acrylate;
(4) an aliphatic urethane diacrylate; and
adding an initiator.
12. The method of claim 1 , wherein said applying step comprises:
formulating the coating composition by dissolving a metal salt, a dye, and the TPU in a solvent blend comprising:
(1) a monofunctional (meth)acrylate;
(2) a multifunctional (meth)acrylate;
(3) a difunctional (meth)acrylate;
(4) an aliphatic urethane diacrylate; and
adding an initiator.
13. The method of claim 12 , wherein said dye is selected from regular dye, photochromic dye, dichroic dye and a combination thereof.