Method for coating an ophthalmic lens within an injection molding machine

• US 7,850,879 B2
• Filed: 12/21/2006
• Issued: 12/14/2010
• Est. Priority Date: 12/21/2005
• Status: Active Grant

• Current Assignee: Essilor International SA
• Original Assignee: Essilor International SA
• Inventors: Yang, Hsinjin, Lockwood, Mattew James, Chen, Xu
• Primary Examiner(s): Crispino; Richard
• Assistant Examiner(s): Bell; William P
• Application Number:
  US12/158,613
• Publication Number:
  US 20090124721A1
• Time in Patent Office: 1,454 Days
• Field of Search: None
• US Class Current: 264/1.7
• CPC Class Codes: B29C 2045/0079 applying a coating or covering
• CPC Class Codes: B29C 45/0001 characterised by the choice of material
• CPC Class Codes: B29C 45/1679 applying surface layers onto injection-moulded substrates inside the mould cavity, e.g. in-mould coating [IMC] applying suface layers after ejection B29C45/0053
• CPC Class Codes: B29C 45/32 having several axially spaced mould cavities , i.e. for making several separated articles
• CPC Class Codes: B29D 11/00009 Production of simple or compound lenses
• CPC Class Codes: B29D 11/0048 Moulds for lenses moulds for plastic articles in general B29C33/00
• CPC Class Codes: B29D 11/00865 Applying coatings; tinting; colouring printing, marking or copying processes B41M; identification in general G09F3/00; producing decorative effects in general B44C; positioning or marking of lenses B24B13/0055
• CPC Class Codes: B29K 2995/0026 Transparent
• CPC Class Codes: B29L 2011/0016 Lenses
• CPC Class Codes: Y10S 425/808 Lens mold

Abstract

A method for in-mold coating of an injection molded thermoplastic lens that resides in an injection molding machine oriented to a horizontal parting line. An optical lens is initially formed by injecting molten thermoplastic resin into an edge-gated lens-forming cavity held closed under a primary clamp force. The mold is opened at a time when the lens is rigid enough to retain its shape. An unpressurized full metered charge of coating is applied onto the center of the lens. The coating is co-molded by ramping up the clamp force from zero to a secondary clamp force less than the primary clamp force to compress the coating into a uniformly thick, fringe-free layer.

Claims

1. A method for optically coating an injection molded thermoplastic lens (L1, L2) that resides in an injection molding machine oriented to a horizontal parting line (16), comprising the steps of:

providing an imbibable liquid coating that includes;

(1) at least one monofunctional (meth)acrylate;

(2) at least one difunctional (meth)acrylate;

(3) at least one multifunctional (meth)acrylate;

(4) at least one aliphatic urethane diacrylate;

(5) at least one metal salt; and

(6) at least one initiator;

injecting (102) molten thermoplastic resin into an edge-gated lens-forming cavity held closed under a primary clamp force to form an ophthalmic lens;

opening (106) the mold (10, 12) at a time when the lens is rigid enough to retain its shape;

depositing (108) an unpressurized full metered charge of the imbibable liquid coating (60e, 60f) onto the center of the lens (L1, L2); and

co-molding (110, 112) the coating by ramping up the clamp force from zero to a secondary clamp force not greater than the primary clamp force to compress the coating into a uniformly thick, fringe-free layer thereby providing an ophthalmic lens with an optically transparent, imbibable coating.

2. The method of claim 1, wherein the co-molding step (110, 112) includes reclamping (110) the open mold (10, 12) to the same cavity volume to spread the coating (60e, 60f) radially-outwardly to a lens periphery within a surficial zone.

3. The method of claim 2, wherein during said reclamping step (110), the coating (60e, 60f) is spread in the absence back pressure.

4. The method of claim 1, wherein the co-molding step (110, 112) includes co-molding the coating (60e, 60f) to exactly replicate the part-forming surface without deforming the lens (L1, L2).

5. The method of claim 1, wherein said depositing step (108) comprises applying a liquid coating (60e, 60f) in an open-air state that thermally cures from the heat of the solidifying lens (L1, L2) and the mold.

6. The method of claim 5, wherein the liquid coating includes a surfactant.

7. The method of claim 6, wherein the liquid coating (60e, 60f) includes at least one hexafunctional (meth)acrylate compound.

8. The method of claim 6, wherein the initiator is selected from alkyl aralkyl peracide compounds.

9. The method of claim 6, wherein the metal salt is Cobalt naphthenate.

10. The method of claim 5, wherein the liquid coating (60e, 60f) sufficiently cures at the molding temperature of the substrate lens.

11. The method of claim 1, wherein the mold (10, 12) opens and closes vertically.

12. The method of claim 1, wherein the primary clamp force is over 100 tons.

13. The method of claim 1, wherein the primary clamp force is about 150 tons.

14. The method of claim 1, wherein the secondary clamp force is less than the primary clamp force, and preferentially in the range from about 10% to about 90% of the primary clamp force.

15. The method of claim 1, wherein the secondary clamp force is equal to the primary clamp force.

16. The method of claim 1, wherein the full metered charge of coating is between 0.1 ml and 5.0 ml.

17. The method of claim 1, wherein the full metered charge of coating (60e, 60f) is between 0.1 ml and 0.8 ml, and preferentially between 0.2 ml and 0.5 ml.

18. The method of claim 1, wherein the thermoplastic resin is selected from the group consisting of polymethyl(meth)acrylate, polycarbonate, polycarbonate/polyester blends, polyamide, polyester, cyclic olefin copolymers, polyurethane, polysulfone, polystyrene, polypentane and combinations thereof.

19. The method of claim 18, wherein thermoplastic is a polycarbonate derivative.

20. The method of claim 1, wherein said co-molding step (110, 112) includes curing the coating (60e, 60f) for about 20 seconds to 5 minutes.

21. The method of claim 1, wherein said cold-molding step includes curing the coating for about 20 seconds to 1 minute.

22. The method of claim 1, wherein the edge-gated lens-forming cavity is one of an afocal lens forming cavity, a unifocal lens forming cavity, a bifocal straight-top lens forming cavity, a trifocal straight-top lens forming cavity, and a progressive lens forming cavity.

23. The method of claim 1, wherein following said co-molding step (110, 112), the method further including the step of:

ejecting (116) the lens from the mold after the coating has cured and the lens is capable of withstanding ejection forces without deforming.

24. The method of claim 1, wherein following said co-molding step (110, 112), the method additionally including the step (120, 112) of:

further opening (106) the mold at a time when the lens is rigid enough to retain its shape;

further depositing (108) an unpressurized full metered charge of further coating onto the center of the lens; and

further co-molding (110, 112) the coating by ramping up the clamp force from zero to a secondary clamp force to compress the further coating into a further uniformly thick, fringe-free layer.

25. The method of claim 1, wherein the liquid coating includes the following concentration percentages,

(1) said at least one monofunctional (meth)acrylate being present in an amount of 18% to 27%;

(3) said at least one multifunctional (meth)acrylate being present in an amount of 33% to 52%;

(4) said at least one aliphatic urethane diacrylate being present in an amount of 13% to 31%;

(5) said at least one metal salt being present in an amount of 0.25% to 1%; and

(6) said at least one initiator being present in an amount of 0.5% to 2%.

26. The method of claim 25, wherein the liquid coating further includes a surfactant selected from the group consisting of a fluorinated surfactant and a silicone surfactant.

27. The method of claim 26, wherein the surfactant is present in an amount of 0.02% and wherein the surfactant improves wetability of the mold surface.

28. The method of claim 25, wherein said at least one monofunctional (meth)acrylate is selected from the group consisting of isobornyl acrylate, hydroxyl propylmethacrylate and combinations thereof.

29. The method of claim 25, wherein said at least one difunctional (meth)acrylate controls the viscosity of the liquid coating for process-ability and increases the flexibility of the coating.

30. A thermoplastic ophthalmic lens having an optically transparent, imbibable coating manufactured by the process of claim 1.