Rapid, thermally cured, back side mar resistant and antireflective coating for ophthalmic lenses
Disclosed is a process to rapidly spin-apply an AR coating system to a backside of a prescription lens. The AR coating system comprises a polyurethane primer layer, a siloxane thermally cured scratch resistant coating layer, a two-layer sol-gel AR coating, and a hydrophobic layer. The process comprising steps of spin-applying each of the layers provides a quick way to furnish a prescription lens that is AR coated on both sides.
1. A process for spin applying an AR coating system onto at least one surface of a lens made of polymer within the same spin coating unit, which comprises:
(a) Providing a semi-finished lens wherein a front surface of said semi-finished lens has a pre-applied AR coating;
(b) Creating a prescription power in said lens by grinding a back surface of said lens;
(c) Applying a thermally curable siloxane hard coating composition to said back surface in a spin coating unit;
(d) Precuring said hard coating to a tack-free state in the same spin coating unit at a set temperature for a set time;
(d) Applying a high index layer of an AR coating to said back surface at a set spin rate for a set time in said same spin coating unit, and precuring the layer at a set temperature and for a set time;
(f) Applying a low index layer of an AR coating to said back surface at a set spin rate for a set time in said same spin coating unit, and precuring the layer at a set temperature and for a set time;
(g) Applying a hydrophobic coating layer to said back surface at a set spin rate for a set time in said same spin coating unit;
(h) Substantially fully curing the high index AR coating, the low index AR coating and the hydrophobic coating layer in a vapor curing oven.
2. The process of claim 1 , wherein a primer layer is applied and cured in the spin-coating unit before the hard coating is applied.
3. The process of claim 1 , wherein the precuring in step (b) includes curing for less than about ten minutes at a chamber temperature range from 150° F. to 300° F.
4. The process of claim 1 , wherein the high index layer, the low index layer of the AR coating and the hydrophobic coating layer are spin-applied at a temperature ranging from about 80° F. to 100° F.
5. The process of claim 1 , wherein the final curing of the high index AR coating, the low index AR coating and the hydrophobic coating layer in step (f) lasts between about five to twenty minutes in a vapor curing oven at a temperature range from about 200° F. to 300° F.
6. The process of claim 1 , wherein the thermally curable hard coating comprises an aqueous organic solvent mixture including hydrolysis products and partial condensates of a functional silane, a tetrafunctional silane and a multifunctional compound wherein the multifunctional compound is selected from the group consisting of multifunctional carboxylic acids, multifunctional anhydrides and combinations thereof and an amount of water sufficient to hydrolyze the functional silane and the tetrafunctional silane.
7. The process of claim 6 , wherein the functional silane is selected from a group consisting of epoxy functional silanes, amino functional silanes, halo functional silanes, hydroxyl functional silanes, carboxyl functional silanes, and isocyanate functional silanes.
8. The process of claim 7 , wherein the functional silane compound containing at least one epoxy group and at least two alkoxy groups directly bonded to the silicon atom of the molecule has formula:
wherein R1 is an alkyl or alkoxy alkyl group having 1 to 4 carbon atoms; R2 is an alkyl or aryl group having 1 to 6 carbons atoms; R3 is hydrogen or methyl group; m is 2 or 3; a is an integer from 1 to 6; and b is 0,1 or 2.
9. The process of claim 7 , wherein the functional silane compound contains at least one epoxy group and at least two alkoxy groups directly bonded to the silicon atom of the molecule is selected from the group consisting of 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxyethoxypropylmethyldimethoxysilane, and mixtures thereof.
10. The process of claim 1 , wherein the lens material is selected from a group consisting of (meth)acrylic resins, di(ethyleneglycol) bis(allyl carbonate) (co)polymers, (halogenated) bisphenol A di(meth)acrylate hormopolymers and copolymers, urethane modified (halogenated) bisphenol A, and polycarbonates.
11. The process of claim 2 , wherein the primer coating layer is from a waterborne aliphatic polyurethane dispersion.
12. The process of claim 8 , wherein the hard coating composition contains 0.05% to 5%, by weight cationic photoinitiator, and the precure of the hard coating is affected with ultraviolet radiation or a combination of ultraviolet light and heat.
13. The process of claim 1 , wherein the high index layer of the AR coating is made of metal oxide selected from the group consisting of titanium oxide, zirconium oxide, indium tin oxide, indium oxide, tin oxide, and antimony tin oxide.
14. The process of claim 1 , wherein the low index layer of the AR coating is derived from a metal alkoxide, M(OR)n, wherein M is selected from at least one of the group consisting of Si, Ti, Al, and Zr; R is an alkyl group having 1–6 carbons and n is an integer representing the valence state of the metal ion.
15. The process of claim 1 , wherein the hydrophobic coating layer is derived from a silane, R n SiX (4-n) , wherein R is an alkyl or a fluorinated alkyl group having 1–8 carbons, n is the number alkyl group attached to the silicon and X is selected from the group consisting of 1–6 carbon alkoxy, fluorinated alkoxy, hydroxyl, acetoxy, and halogens.
16. The process of claim 1 , wherein the lens is an ophthalmic lens whose front side is coated with a multi-layer AR coating that has been applied with a vacuum deposition process.