Photochromic coating exhibiting improved performance
View Patent ↗A photochromic coating exhibiting improved performance and photochromic lenses made using the coating. The coating has excellent photochromic darkening and fatigue properties. The coating formulation is made from a monomer blend having at least two different types of monomers. A metal salt catalyst is used along with an initiator. An antioxidant is used in combination with a hindered amine light stabilizer. The coating is suitable for use in an in-mold coating process.
1. A thermally curable photochromic coating composition comprising:
a mixture having two different monomers, where the monomers are selected from the group consisting of: (a) monofunctional (meth)acrylate; (b) difunctional (meth)acrylate; (c) a combination of a monofunctional (meth)acrylate and a difunctional (meth)acrylate; (d) multifunctional (meth)acrylate; and (e) aliphatic urethane diacrylate;
a metal salt selected from the group consisting of a metal ester of 2-naphthoic acid, a metal ester of 2-ethylhexanoic acid, a metal ester of octoate material, and combinations thereof;
a Hindered Amine Light Stabilizer (HALS);
an antioxidant;
an initiator selected from the group consisting of t-amylperoxy-2-ethylhexyl carbonate organic peroxide and t-butylperoxy-2-ethylhexylcarbonate; and
a photochromic dye.
2. The photochromic coating composition of claim 1 , wherein the monofunctional (meth)acrylate is selected from the group consisting of isobornylacrylate, hydroxypropylmethacrylate, benzyl acrylate, and combinations thereof.
3. The photochromic coating composition of claim 1 , wherein the difunctional (meth) acrylate is selected from the group consisting of polyethyleneglycol (600) dimethacrylate, ethoxylated (8) bisphenol A dimethacrylate, ethoxylated (10) bisphenyl A diacrylate, and ethoxylated (30) bisphenyl A dimethacrylate.
4. The photochromic coating composition of claim 1 , wherein the multifunctional (meth)acrylate is selected from the group consisting of hexafunctional aliphatic urethane acrylate and dipentaerythritol pentaacrylate.
5. The photochromic coating composition of claim 1 , wherein the aliphatic urethane diacrylate is selected from the group consisting of aliphatic polyester urethane diacrylate, aliphatic urethane diacrylate diluted with a reactive diluent 1,6-hexanediol diacrylate, aliphatic urethane diacrylate diluted with a reactive diluent isobornyl acrylate and combinations thereof
6. The photochromic coating composition of claim 1 , wherein the antioxidant is a sterically hindered phenolic compound.
7. The photochromic coating composition of claim 6 , wherein the antioxidant is a pentaerythritol tetrakis [3 -(3,5 -di-tert-butyl-4-hydroxyphenyl)propionate]hindered phenolic compound.
8. The photochromic coating composition of claim 1 , wherein the metal salt is selected from the group consisting of tin-2-ethylhexanoate, bismuth carboxylate, and cobalt naphthenate.
9. The photochromic coating composition of claim 1 , wherein the HALS is selected from the group consisting of [4-(methoxyphenyl)-methylene]-bis-1,2,2,6,6-pentamethyl-4-piperidinyl-propanedioic acid ester and phenyl-(3,5-di-tert.butyl-4-hydroxy-benzyl)-malonic acid-bis-(1,2,2,6,6-penta-methyl-4-piperidinyl)ester.
10. The photochromic coating composition of claim 1 , wherein:
the monomers of (a) monofunctional (meth)acrylate; (b) difunctional (meth)acrylate; and
(c) a combination of a monofunctional (meth)acrylate and a difunctional (meth)acrylate are present in an amount from 10% to 25% by weight;
the monomers of (d) multifunctional (meth)acrylate are present in an amount from 20% to 40% by weight;
the monomers of (e) aliphatic urethane diacrylate are present in an amount from 50% to 70% by weight;
the metal salt is present in an amount from 0.10 phm to 0.30 phm;
the Hindered amine light stabilizer (HALS) is present in an amount from 1.00 phm to 5.00 phm;
the antioxidant is present in an amount from 0.20 phm to 0.50 phm;
the initiator is present in an amount from 1.00 phm to 2.00 phm; and
the photochromic dye is presents in an amount from 1.00 phm to 5.00 phm.
11. The photochromic coating composition of claim 1 , wherein the monomer of (a) monofunctional (meth)acrylate comprises a mixture of isobornyl acrylate in an amount from 1% to 5% by weight and benzyl acrylate or 2-hydroxypropylmethacrylate in an amount from 10% to 21%.
12. The photochromic coating composition of claim 1 , wherein
the mixture of monomers comprises isobornylacrylate present in an amount of 5% by weight, hydroxypropylmethacrylate present in an amount of 10% by weight, aliphatic urethane diacrylate present in an amount of 18% by weight, hexafunctional aliphatic urethane acrylate present in an amount of 33% by weight, and aliphatic urethane diacrylate present in an amount of 34% by weight;
the metal salt comprises tin-2-ethylhexanoate present in an amount of 0.14 phm;
the Hindered amine light stabilizer (HALS) is selected from the group consisting of [4-(methoxyphenyl)-methylene]-bis-1,2,2,6,6-pentamethyl-4-piperidinyl-propanedioic acid ester and phenyl-(3,5-di-tert.butyl-4-hydroxy-benzyl)-malonic acid-bis-(1,2,2,6,6penta-methyl-4-piperidiny)ester present in an amount of 1 phm;
the antioxidant comprises pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]hindered phenolic compound present in an amount of 0.25 phm;
the initiator comprises t-amylperoxy-2-ethylhexyl carbonate organic peroxide present in an amount of 1.5 phm; and
the photochromic dye is present in an amount of 2.0 phm to 4.0 phm.