Photochromic polyurethane laminate
A photochromic polyurethane laminate that is constructed to solve certain manufacturing difficulties involved in the production of plastic photochromic lenses is disclosed. The photochromic laminate includes at least two layers of a resinous material and a photochromic polyurethane layer that is interspersed between the two resinous layers and which contains photochromic compounds. The polyurethane layer is formed by curing a mixture of a solid thermoplastic polyurethane, at least one isocyanate prepolymer, at least one photochromic compound, and a stabilizing system.
1. A photochromic polyurethane laminate for use in an optical article comprising:
a first resin sheet;
a second resin sheet; and
a photochromic polyurethane layer having a top side attached to said first resin sheet and a bottom side attached to said second resin sheet, said photochromic polyurethane layer prepare from a composition comprising:
a solid thermoplastic polyurethane prepared from a composition comprising at least one diisocyanate selected from a group consisting of: aliphatic diisocyanate and cycloaliphatic diisocyanate;
at least one isocyanate-terminated polyurethane prepolymer; and
at least one photochromic compound;
wherein said photochromic polyurethane laminate has a molecular structure resulting from curing said laminate within a temperature range from about 50 degrees Celsius to about 130 degrees Celsius.
2. A photochromic polyurethane laminate according to claim 1 , wherein said solid thermoplastic polyurethane, having a molecular weight in the range of about 9,000 to 100,000 g/mole, is obtained by reacting
a) a polyol selected from a group consisting of polyester polyols and polyether polyols, having a molecular weight in the range of about 500 to 6,000 g/mol, and a functionality of 2;
b) with said diisocyanate in an equivalent ratio of diisocyanate to polyol in the range of about 1.2:1.0 to 8.0:1.0;
c) with a diol as a chain extender having a molecular weight in the range of about 62 to 499 g/mol, the theoretical NCO index calculated by multiplying 100 to the equivalent ratio of isocyanate groups to the sum of the hydroxyl groups of polyol and diol being within a range of about 90 to 105.
3. A photochromic polyurethane laminate according to claim 1 , wherein said isocyanate-terminated polyurethane prepolymer, having a molecular weight in the range of about 1,000 to 6,000 g/mole, is obtained by reacting
a) a polyol selected from a group consisting of polyester polyols and polyether polyols, having a molecular weight in a range of about 500 to 3000 g/mol and a functionality of 2;
b) with an aliphatic diisocyanate, a cycloaliphatic diisocyanate, or both, in an equivalent ratio of diisocyanate to polyol in a range of about 1.2:1.0 to 8.0:1.0.
4. A photochromic polyurethane laminate according to claim 1 , wherein said photochromic compound is selected from the group consisting essentially of benzopyrans, naphthopyrans, spirobenzopyrans, spironaphthopyrans, spirobenzoxzines, spironaphthoxazines, fulgides and fulgimides.
5. A photochromic polyurethane laminate according to claim 1 , wherein the resin material for said resin sheets are selected from a group consisting of polycarbonates, cycloolefin (co)polymers, polymers from acrylate derivatives, cellulose acetate butyrate, cellulose triacetate.
6. A photochromic polyurethane laminate according to claim 2 , wherein said polyester polyol is selected from a group consisting of polycaprolactone polyol and poly(butylene adipate) polyol.
7. A photochromic polyurethane laminate according to claim 2 , wherein said polyether polyol is selected from a group consisting of polypropylene glycol and polytetramethylene glycol.
8. A photochromic polyurethane laminate according to claim 2 , wherein said diisocyanante is selected from a group consisting of hexamethylene diisocyanate, isophorone diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, and dicyclohexylmethane diisocyanate.
9. A photochromic polyurethane laminate according to claim 2 , wherein said diol is selected from a group consisting of propane diol, butane diol, pentane diol, hexane diol, diethylene glycol, dipropylene glycol, and cyclohexane diol.
10. A photochromic polyurethane laminate according to claim 3 , wherein said polyester polyol is selected from a group consisting of polycaprolactone polyol and poly(butylene adipate) polyol.
11. A photochromic polyurethane laminate according to claim 3 , wherein said polyether polyol is selected from a group consisting of polypropylene glycol and polytetramethylene glycol.
12. A photochromic polyurethane laminate according to claim 3 , wherein said diisocyanante is selected from a group consisting of hexamethylene diisocyanate, isophorone diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, and dicyclohexylmethane diisocyanate.
13. A photochromic polyurethane laminate according to claim 1 , wherein said photochromic polyurethane layer has a thickness in a range of about 10 μm to about 100 μm.
14. A photochromic polyurethane laminate according to claim 4 , wherein said photochromic compound is selected from the group consisting essentially of naphtho[2,1b]pyrans and naphtho[1,2b]pyrans.
15. A photochromic polyurethane laminate according to claim 1 , wherein the mixing ratio of said thermoplastic polyurethane to said isocyanate-terminated polyurethane prepolymer is in a range of about 9:1 to 1:9, by weight.
16. A photochromic polyurethane layer for use in an optical laminate prepared from a mixture comprising:
a solid thermoplastic polyurethane prepared from a composition comprising at least one diisocyanate selected from a group consisting of: aliphatic diisocyanate and cycloaliphatic diisocyanate;
at least one isocyanate-terminated polyurethane prepolymer; and
at least one photochromic compound.
17. The photochromic polyurethane layer of claim 16 wherein said solid thermoplastic polyurethane, having a molecular weight in the range of about 9,000 to 100,000 g/mole, is obtained by reacting
a) a polyol selected from a group consisting of polyester polyols and polyether polyols, having a molecular weight in the range of about 500 to 6,000 g/mol, and a functionality of 2;
b) with said diisocyanate in an equivalent ratio of diisocyanate to polyol in the range of about 1.2:1.0 to 8.0:1.0;
c) with a diol as a chain extender having a molecular weight in the range of about 62 to 499 g/mol, the theoretical NCO index calculated by multiplying 100 to the equivalent ratio of isocyanate groups to the sum of the hydroxyl groups of polyol and diol being within a range of about 90 to 105.
18. The photochromic polyurethane layer of claim 16 wherein the isocyanate-terminated polyurethane prepolymer, having a molecular weight in the range of about 1,000 to 6,000 g/mole, is obtained by reacting
a) a polyol selected from a group consisting of polyester polyols and polyether polyols, having a molecular weight in a range of about 500 to 3000 g/mol and a functionality of 2;
b) with an aliphatic diisocyanate, a cycloaliphatic diisocyanate, or both, in an equivalent ratio of diisocyanate to polyol in a range of about 1.2:1.0 to 8.0:1.0.
19. The photochromic polyurethane layer of claim 16 wherein the layer has a thickness between 5 micrometers and 80 micrometers.
20. The photochromic polyurethane layer of claim 16 wherein the layer has a variation in thickness of less than 15 percent.