Injection molding a lens onto a coated ophthalmic wafer

Abstract

A method of in-mold coating utilizing an injection molding machine oriented to a horizontal parting line. At the beginning of the cycle the mold opens and a charge of liquid coating solution is deposited onto the lower mold insert. A ophthalmic wafer is deposited on the coating to spread it across the insert surface. The mold is closed and a pre-cure phase elapses before the thermoplastic resin is injected into the mold cavity above the wafer. The process provides coated and functionally enhanced lenses upon ejection from the molding machine.

1 . A method of injection molding a functionally enhanced coated thermoplastic optical lens in an injection molding machine ( 60 ) having a horizontally oriented parting line with a metal concave insert ( 60   f ) disposed in the lower stationary mold half ( 60   a ), wherein the insert ( 60   f ) has a base curve C and is heated to a temperature T below a thermoplastic glass transition temperature T G , comprising the steps of:
 depositing ( 12 ) an unpressurized liquid coating ( 42   a ) drop onto the concave insert while ( 60   f ) the mold is open;   providing ( 14 ) a functional ophthalmic wafer having a concave side and a convex base curve C to spread the coating ( 42   a ) across the entire surface of the insert ( 60   f );   closing ( 16 ) the mold to heat and pre-cure the coating;   injecting ( 18 ) thermoplastic resin via an edge gate onto the concave side of the wafer; and   integrally forming ( 20 ) a functionally enhanced coated optical lens by allowing the resin to cool towards T.   
   
   
       2 . The method of to  claim 1 , wherein the insert temperature T is in the range from about 240° F. to about 290° F. 
   
   
       3 . The method of  claim 1 , wherein the insert temperature T is about 250° F. 
   
   
       4 . The method of  claim 1 , wherein the liquid coating ( 42   a ) has a sufficiently low viscosity whereby it is spread across the entire surface of the insert ( 60   f ) under the weight of the wafer ( 55 ). 
   
   
       5 . The method of  claim 4 , wherein the coating ( 42   a ) is spread in the absence of back pressure. 
   
   
       6 . The method of  claim 1 , wherein said closing step ( 16 ) comprises:
 closing the mold and pausing to heat and pre-cure the coating.   
   
   
       7 . The method of  claim 6 , wherein said injecting step ( 18 ) initiates after a two minute pause. 
   
   
       8 . The method of  claim 6 , wherein the injecting step ( 18 ) initiates after the coating ( 42   a ) has pre-cured sufficiently to resist deformation by the force of the injected resin. 
   
   
       9 . The method of  claim 1 , wherein the mold includes a movable top half that opens and closes vertically. 
   
   
       10 . The method of  claim 1 , wherein the coating drop comprises a full metered charge of coating ( 42   a ) modified by diluents to avoid curing until the coating ( 42   a ) completely covers the convex base of the wafer. 
   
   
       11 . The method of  claim 10 , wherein the full metered charge of coating ( 42   a ) amounts is deposited in an amount ranging between 0.1 ml to 0.8 ml. 
   
   
       12 . The method of  claim 1 , wherein the coating ( 42   a ) is deposited in an amount ranging between 0.1 ml to 0.8 ml. 
   
   
       13 . The method of  claim 13 , wherein the coating ( 42   a ) is deposited in an amount ranging between about 0.2 ml to about 0.5 ml. 
   
   
       14 . The method of  claim 1 , wherein the wafer ( 55 ) is a polarized film and said integrally forming step comprises integrally forming a polarized lens in which the film is protected on one side by the thermoplastic lens and on the other side by the cured coating. 
   
   
       15 . The method of  claim 1 , wherein the wafer ( 55 ) is a photochromic film and said integrally forming step comprises integrally forming a photochromic lens in which the film is protected on one side by the thermoplastic lens and on the other side by the cured coating. 
   
   
       16 . The method of  claim 1 , wherein the thermoplastic resin and the carrier are independently selected from the group consisting of polymethyl(meth)acrylate, polycarbonate, polycarbonate/polyester blends, polyamide, polyester, cyclic olefin copolymers, polyurethane, polysulfone and combinations thereof. 
   
   
       17 . The method of  claim 16 , wherein the resin and the wafer ( 55 ) include the same material. 
   
   
       18 . The method of  claim 17 , wherein the resin and the wafer ( 55 ) include polycarbonate derivatives. 
   
   
       19 . The method of  claim 1 , wherein the liquid coating ( 42   a ) includes one or more (meth)acrylate compounds, an initiator, and a metal salt. 
   
   
       20 . The method of  claim 19 , wherein the liquid coating ( 42   a ) includes at least one hexafunctional acrylate compound, at least one difunctional acrylate compound, and at least one monofunctional acrylate compound. 
   
   
       21 . The method of  claim 19 , wherein the initiator is a alkyl aralkyl peracide compound. 
   
   
       22 . The method of  claim 19 , wherein the metal salt is cobalt naphthenate. 
   
   
       23 . A functionally enhanced coated thermoplastic optical lens manufactured by the process of  claim 1 . 
   
   
       24 . A polarized coated thermoplastic optical lens manufactured by the process of  claim 1 . 
   
   
       25 . A photochromic coated thermoplastic optical lens manufactured by the process of  claim 1 .