Coating providing panchromatic scattering
An article includes a substrate with a surface, and a coating disposed over the surface. The coating includes a binder material and a plurality of porous polymer particles having pores with a variety of pore sizes including a first set of pores having a first average pore size d1 in the range 0.3≤d1/λ1≤0.7, wherein λ1 is a wavelength in the range of 250-400 nm, a second set of pores having a second average pore size d2 in the range 0.3≤d2/λ2≤0.7, wherein λ2 is a wavelength in the range of 400-700 nm, and a third set of pores having a third average pore size d3 in the range 0.3≤d3/λ3≤0.7, wherein λ3 is a wavelength in the range of 700-3000 nm, wherein the porous polymer particles have a shell which is impermeable to a liquid.
1. An article comprising:
a substrate with a surface; and
a coating disposed over the surface, including:
a plurality of porous polymer particles having pores with a variety of pore sizes including a first set of pores having a first average pore size d1 in the range 0.3≤d1/λ1≤0.7, wherein λ1 is a wavelength in the range of 250-400 nm, a second set of pores having a second average pore size d2 in the range 0.3≤d2/λ2≤0.7, wherein λ2 is a wavelength in the range of 400-700 nm, and a third set of pores having a third average pore size d3 in the range 0.3≤d3/λ3≤0.7, wherein λ3 is a wavelength in the range of 700-3000 nm, wherein the porous polymer particles have a shell which is impermeable to a liquid; and
a binder material that is a matrix polymer;
the article further including one or more overcoat layers positioned over the coating,
wherein one of the overcoat layers is a low-specular-reflectance surface layer including a plurality of protruding substantially spherical caps having a multimodal size distribution.
2. The article of claim 1 , wherein at least some of the porous polymer particles are panchromatic scattering porous polymer particles, each of the panchromatic scattering porous polymer particles including pores in the first set of pores, pores in the second set of pores and pores in the third set of pores.
3. The article of claim 2 , wherein the panchromatic scattering porous polymer particles have pores with a variety of pore sizes which include pores in the first set of pores, pores in the second set of pores, and pores in the third set of pores.
4. The article of claim 1 , wherein the porous polymer particles include:
ultraviolet scattering porous polymer particles having pores in the first set of pores;
visible light scattering porous polymer particles having pores in the second set of pores;
near infrared scattering porous polymer particles having pores in the third set of pores.
5. The article of claim 1 , wherein the substrate is a metal or has a metalized surface.
6. The article of claim 1 , wherein the porous polymer particles have a particle size between 0.5-100 μm.
7. The article of claim 1 , wherein the porous polymer particles have a porosity in the range of 10-50%.
8. The article of claim 1 , further comprising an underlying layer that includes a broad-band absorbing material.
9. The article of claim 8 , wherein one of the underlying layers includes a subtractive colorant.
10. The article of claim 1 , wherein no more than 5% of the coating corresponds to interstitial voids not filled with the matrix polymer.
11. The article of claim 1 , wherein the article substrate is a textile, a metal, a flexible latex resin, an adhesive laminate, a metallized polymer, a cellulosic material, glass, or ceramic.
12. The article of claim 1 , that is camouflage clothing.
13. The camouflage article of claim 12 , wherein the third set of pores having a third average pore size d3 in the range 0.3≤d3/λ3≤0.7 is provided by unfilled interstitial voids among the porous polymer particles, which unfilled interstitial voids represent less than 10% of the volume within the camouflage coating.