High adhesion acrylate coatings for a photochromic ophthalmic lens

Abstract

A method used to prepare a photochromically-enabled bifocal ophthalmic lens. A lens substrate is injection molded and then a coating is applied to the substrate to form a bifocal surface. The coating is a high adhesive strength acrylate-based coating that contains a small quantity of a polycarbonate-based TPU. The thermoset coating produces an intermediate imbibable bifocal surface. A photochromic solution is subsequently imbibed by contact with the bifocal surface. The TPU acts as an adhesion enhancer so that the coating to substrate integrity is maintained following the imbibing step.

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; and   imbibing a photochromic dye solution into the surface;   wherein the acrylate-based composition contains an adhesion enhancer comprising a thermoplastic polyurethane (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% thermoplastic, polyurethane (TPU) parts per hundred parts of monomer (phm). 
   
   
       6 . The method of  claim 5 , wherein the coating composition is devoid of photochromic dyes. 
   
   
       7 . The method of  claim 5 , wherein the coating composition comprises at least one monofunctional (meth)acrylate present in an amount of about 10 to 20% by weight. 
   
   
       8 . The method of  claim 5 , wherein the TPU is an aliphatic polycarbonate-based TPU present in an amount of about 1 phm. 
   
   
       9 . The method of  claim 5 , wherein the photochromically-enabled bifocal ophthalmic lens has an % T initial above about 80 and a % T dark around 20. 
   
   
       10 . The method of  claim 1 , wherein prior to said applying step the method further 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. 
   
   
   
       11 . The method of  claim 10 , wherein the coating composition comprises an imbibable, thermoset composition, wherein said at least one thermoplastic polyurethane (TPU) is present in an amount of about 0.5 phm to about 5.0 phm. 
   
   
       12 . The method of  claim 10 , wherein the monofunctional (meth)acrylate is selected from the group consisting of isobornyl acrylate, methyl methacrylate, benzyl methacrylate, benzyl acrylate, hydroxypropyl methacrylate, 2-phenoxyethyl methacrylate, and combinations thereof, and wherein the monofunctional (meth)acrylate is present in an amount of about 10% to 20% by weight. 
   
   
       13 . The method of  claim 10 , wherein the monofunctional (meth)acrylate is benzyl acrylate. 
   
   
       14 . The method of  claim 10 , wherein the multifunctional (meth)acrylate is selected from the group consisting of dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate, hexafunctional aliphatic urethane acrylate, and combinations thereof. 
   
   
       15 . The method of  claim 10 , wherein the multifunctional (meth)acrylate is dipentaerythitol pentaacrylate. 
   
   
       16 . The method of  claim 10 , wherein the difunctional (meth)acrylate is selected from the group consisting of 1,6-hexanediol diacrylate, ethoxylated bisphenol A di(meth)acrylate, polyethylene glycol di(meth)acrylate and combinations thereof. 
   
   
       17 . The method of  claim 10 , wherein the metal salt includes cobalt naphthenate and the initiator is tert-butylperoxybenzoate. 
   
   
       18 . The method of  claim 10 , wherein the thermoplastic polyurethane comprises a polycarbonate-based aliphatic polyurethane having a Specific gravity of between 1.0 and 1.3; a Flexural modulus between 550 and of 690 psi; an Ultimate Tensile of between 4,000 and 6,000 psi; and Mold, shrinkage of 0.006-0.014 in/in., wherein the TPU is present in an amount of about 1 phm. 
   
   
       19 . The method of  claim 1 , wherein said coating is an imbibable thermoset composition comprising:
 (1) at least one monofunctional (meth)acrylate being present in an amount of about 5% to 40% by weight;   (2) at least one multifunctional (meth)acrylate being present in an, amount of about 5% to 50% by weight;   (3) a difunctional (meth)acrylate being present in an amount of about 5% to 50% by weight;   (4) an aliphatic urethane diacrylate being present in an amount of about 5% to 60% by weight;   (5) at least one metal salt being present in an amount about 0.05 to 2.0 phm;   (6) at least one initiator being present in an amount of about 0.1 to 5.0 phm; and   (7) at least one thermoplastic polyurethane (TPU) being present in an amount of about 0.5 phm to 5.0 phm.   
   
   
       20 . The method of  claim 1 , wherein said coating is an imbibable thermoset composition comprising:
 (1) at least one monofunctional (meth)acrylate being present in an amount of about 10 to 20% by weight;   (2) at least one multifunctional (meth)acrylate being present in an amount of about 10 to 35% by weight;   (3) a difunctional (meth)acrylate being present in an amount of about 10% to 35% by weight;   (4) an aliphatic urethane diacrylate being present in an amount of about 30% to 50% by weight;   (5) at least one metal salt;   (6) at least one initiator; and   (7) at least one thermoplastic polyurethane (TPU).