Near infrared reflective coatings, pigments, and colored compositions
Techniques and compositions are described for reflective coatings and pigments for reflecting electromagnetic radiation, such as visible and solar near-infrared light. In one aspect, a reflective coating includes a base layer having a reflective surface, and an absorber layer formed on the reflective surface of the base layer, in which the reflective coating provides an average reflectance of electromagnetic radiation for wavelengths in the range of 900 nm to 2500 nm irradiated upon the reflective coating greater than substantially 70%, and provides an average reflectance of electromagnetic radiation for wavelengths in the range of 400 nm to 700 nm irradiated upon the reflective coating of less than 40%.
1. A reflective pigment, comprising:
a base layer structured to include a top reflective surface and a bottom reflective surface;
an absorber layer directly attached to each of the top and bottom reflective surfaces of the base layer; and
a dielectric layer directly attached to each of the absorber layers, wherein the dielectric layer includes at least one of silicon nitride, silicon dioxide, metal nitrides, metal oxides or metal fluorides,
wherein the reflective pigment provides an average reflectance of electromagnetic radiation for wavelengths in the range of 900 nm to 2500 nm irradiated upon the reflective pigment greater than about 70%, and provides an average reflectance of electromagnetic radiation for wavelengths in the range of 400 nm to 700 nm irradiated upon the reflective coating of less than 40%.
2. The reflective pigment of claim 1 , wherein the absorber layer includes an amorphous silicon.
3. The reflective pigment of claim 1 , wherein the absorber layers directly attached to the top and bottom reflective surfaces of the base layer are configured to have a thickness in a range of 5 to 50 nm.
4. The reflective pigment of claim 1 , wherein the dielectric layers directly attached to each of the absorber layers are configured to have a thickness in a range of 5 to 500 nm.
5. The reflective pigment of claim 1 , wherein the dielectric layers are configured to have an index of refraction at 550 nm of 1.3 to 2.5.
6. The reflective pigment of claim 1 , further comprising:
a polymer layer directly attached to each of the outer surfaces of the dielectric layers.
7. The reflective pigment of claim 1 , further comprising:
a second absorber layer directly attached to each of the outer surfaces of the dielectric layers.
8. The reflective pigment of claim 7 , further comprising:
a polymer layer directly attached to each of the outer surfaces of the second absorber layer.
9. The reflective pigment of claim 7 , further comprising:
a second dielectric layer directly attached to each of the outer surfaces of the second absorber layers.
10. The reflective pigment of claim 9 , further comprising:
a polymer layer directly attached to each of the outer surfaces of the second dielectric layers.
11. The reflective pigment of claim 10 , wherein the polymer layer is configured to have a thickness in a range of 1000 to 3000 nm.
12. The reflective pigment of claim 1 , wherein the base layer is a metal layer.
13. The reflective pigment of claim 12 , wherein the metal layer includes aluminum.
14. The reflective pigment of claim 1 , wherein said base layer is an aluminum/polymer/aluminum layered structure.
15. The reflective pigment of claim 1 formed in a colored composition, the colored composition comprising:
a polymer medium; and
a plurality of the reflective pigments dispersed in the polymer medium.
16. The reflective pigment of claim 15 , wherein the polymer medium is a paint or ink.