Multi-layer fluoropolymeric film and articles incorporating such films
The present invention discloses a multi-layer fluoropolymeric film that is useful as a light capture front sheet in solar modules, and more broadly as an antireflection layer. The present invention further discloses a glass shaped article having a multi-layer fluoropolymeric film disposed upon the surface thereof. The shaped article is useful in applications where it is desirable to reduce reflection of incident light.
1. A multi-layer fluoropolymeric film comprising
a first fluoropolymeric layer having a refractive index of 1.45 to 1.50 and a thickness greater than about 10 micrometers, the first fluoropolymeric layer comprising a first fluoropolymer; and
a second fluoropolymeric layer having a refractive index of 1.33 to 1.37 and a thickness of 100 to 150 nanometers, the second fluoropolymeric layer comprising a second fluoropolymer;
with the proviso that the reflectance spectrum of the multi-layer fluoropolymeric film exhibits at least one minimum between 400 and 1100 nm.
2. The multi-layer fluoropolymeric film of claim 1 further comprising a third fluoropolymeric layer disposed between the first fluoropolymeric layer and the second fluoropolymeric layer and in adhering contact with both, the third fluoropolymeric layer comprising a third fluoropolymer and 50 to 60 volume % of one or more nano-scale particulate inorganic oxides or nitrides, the third fluoropolymeric layer having a refractive index of 1.50 to 1.70 and a thickness of 1 to 240 nanometers.
3. The multi-layer fluoropolymeric film of claim 2 wherein the second and third fluoropolymers are the same.
4. The multi-layer fluoropolymeric film of claim 3 wherein the third fluoropolymer is a cross-linked terpolymer comprising monomer units of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene, wherein 50-85% of the monomer units are derived from vinylidene fluoride.
5. The multi-layer fluoropolymeric film of claim 3 wherein the second fluoropolymeric layer and the third fluoropolymeric layer are disposed in a single stratified film layer, the stratified film layer having a polymer-poor bottom stratum and a polymer-rich top stratum, the bottom stratum adheringly contacting the first fluoropolymeric layer, the bottom stratum comprising the second fluoropolymer and the one or more particulate nano-scale inorganic oxides or nitrides, the bottom stratum having a refractive index of 1.50 to 1.70; the top stratum comprising the second fluoropolymer and having a refractive index of 1.33 to 1.37; and wherein the one or more inorganic oxides or nitrides are surface functionalized with an acryloyl siloxyl radical represented by the formula
CH 2 ═CXC(═O)O—Y—Si(R 1 )(R 2 )—O—
where X is H or Me, Y is a divalent organic radical, selected from substituted and unsubstituted C2-C10 alkylene radicals, and substituted or unsubstituted C6-C20 arylene groups, that can comprise ether, ester, or amide linkages; and R 1 and R 2 are independently selected from the group consisting of C1-C20 alkoxy, C6-C20 aryloxy, C1-C20 alkyl, C6-C20 aryl, C7-C30 aralkyl, C7-C30 alkaryl, halogen, and hydrogen.
6. The multi-layer fluoropolymeric film of claim 5 wherein Y is —CH 2 —CH 2 —CH 2 —, and R 1 and R 2 are methoxy.
7. The multi-layer fluoropolymeric film of claim 1 or claim 2 in the form of a continuous roll of film.
8. The multi-layer fluoropolymeric film of claim 2 wherein the particulate nano-scale inorganic oxide comprises ZrO 2 .
9. A shaped article comprising a multi-layer fluoropolymeric film disposed on a glass shaped article having a surface and an adhesive layer disposed between the surface and the film, the multi-layer fluoropolymeric film comprising
a first fluoropolymeric layer having a refractive index of 1.45 to 1.50 and a thickness greater than about 10 micrometers, the first fluoropolymeric layer comprising a first fluoropolymer; and
a second fluoropolymeric layer having a refractive index of 1.33 to 1.37 and a thickness of 100 to 150 nanometers, the second fluoropolymeric layer comprising a second fluoropolymer;
with the proviso that the reflectance spectrum of the multi-layer fluoropolymeric film exhibits at least one minimum between 400 and 1100 nm.
10. The shaped article of claim 9 wherein the multi-layer fluoropolymeric film further comprises a third fluoropolymeric layer disposed between the first fluoropolymeric layer and the second fluoropolymeric layer and in adhering contact with both, the third fluoropolymeric layer comprising a third fluoropolymer and 50 to 60 volume % of one or more nano-scale particulate inorganic oxides or. nitrides, the third fluoropolymeric layer having a refractive index of 1.50 to 1.70 and a thickness of 1 to 240 nanometers.
11. The shaped article of claim 10 wherein the second and third fluoropolymers are the same.
12. The shaped article of claim 11 wherein the third fluoropolymer is a cross-linked terpolymer of monomer units comprising vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene, wherein 50-85% of the monomer units are derived from vinylidene fluoride.
13. The shaped article of claim 11 wherein the second fluoropolymeric layer and the third fluoropolymeric layer are disposed in a single stratified film layer, the stratified film layer having a polymer-poor bottom stratum and a polymer-rich top stratum, the bottom stratum adheringly contacting the first fluoropolymeric layer, the bottom stratum comprising the second fluoropolymer and the one or more particulate nano-scale inorganic oxides or nitrides, the bottom stratum having a refractive index of 1.50 to 1.70; the top stratum comprising the second fluoropolymer and having a refractive index of 1.33 to 1.37; and wherein the one or more inorganic oxides or nitrides are surface functionalized with an acryloyl siloxyl radical represented by the formula
CH 2 ═CXC(═O)O—Y—Si(R 1 )(R 2 )—O—
where X is H or Me, Y is a divalent organic radical, selected from substituted and unsubstituted C2-C10 alkylene radicals, and substituted or unsubstituted C6-C20 arylene groups, that can comprise ether, ester, or amide linkages; and R 1 and R 2 are independently selected from the group consisting of C1-C20 alkoxy, C6-C20 aryloxy, C1-C20 alkyl, C6-C20 aryl, C7-C30 aralkyl, C7-C30 alkaryl, halogen, and hydrogen.
14. The shaped article of claim 13 wherein Y is —CH 2 —CH 2 —CH 2 —, and R 1 and R 2 are methoxy.
15. The shaped article of claim 9 wherein the glass shaped article is in the form of sheet.
16. The shaped article of claim 9 wherein the adhesive consists essentially of an ionomer.
17. The multi-layer fluoropolymeric film of claim 10 wherein the particulate nano-scale inorganic oxide comprises ZrO 2 .