Coating providing ultraviolet 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 UV scattering porous polymer particles having pores with a light scattering effective pore size of no more than 100 nm. The coating has a scattering opacity of no more than 20% in the wavelength band from 500 to 3000 nm.
1. An article comprising:
a substrate with a surface; and
a coating disposed over the surface, including:
a plurality of ultraviolet (UV) scattering porous polymer particles having pores with a light scattering effective pore size of no more than 100 nm; and
a binder material;
wherein the coating has a scattering opacity of no more than 20% in a wavelength band of from 500 to 3000 nm.
2. The article of claim 1 , wherein the pores of the ultraviolet (UV) scattering porous polymer particles have the light scattering effective pore size that is no more than 80 nm.
3. The article of claim 1 , wherein the ultraviolet (UV) scattering porous polymer particles have a shell which is impermeable to a liquid.
4. The article of claim 1 , further including an underlying layer disposed between the coating and the substrate.
5. The article of claim 4 , wherein the underlying layer includes a broad-band absorbing material or a subtractive colorant.
6. The article of claim 4 , wherein the underlying layer includes a plurality of porous polymer particles having pores with a specified distribution of pore sizes.
7. The article of claim 6 , wherein the pores in the porous polymer particles in the underlying layer includes a first set of pores having a first average pore size d1 in a range 0.3≤d1/λ1≤0.7, wherein λ1 is a wavelength in a range of 250-400 nm, a second set of pores having a second average pore size d2 in a range 0.3≤d2/λ2≤0.7, wherein λ2 is a wavelength in a range of 400-700 nm, and a third set of pores having a third average pore size d3 in a range 0.3≤d3/λ3≤0.7, wherein λ3 is a wavelength in a range of 700-3000 nm.
8. The article of claim 1 , wherein the coating is a low-specular-reflectance surface layer, wherein the ultraviolet (UV) scattering porous polymer particles protrude from an upper surface of the coating thereby providing substantially spherical caps, and wherein the ultraviolet (UV) scattering porous polymer particles have a multimodal particle size distribution.
9. The article of claim 8 , wherein the multimodal particle size distribution has a distribution function having two or more modes, each mode having a peak defining an associated mode particle size, wherein the distribution function includes a first mode having a first peak corresponding to a first particle size and a second mode having a second peak corresponding to a second particle size;
wherein a mode width parameter for each of the modes is less than or equal to 1.0, the mode width parameter for a particular mode being given by a ratio of a full-width half-maximum width of the particular mode to the particle size of the particular mode;
wherein a ratio of the second particle size to the first particle size is between 1.7-4.0; and
wherein a smallest of the mode particle sizes is greater than or equal to 1.0 micron, and a largest of the mode particle sizes is greater than or equal to 3.0 microns.
10. The article of claim 1 , wherein the ultraviolet (UV) scattering porous polymer particles have a particle size in a range of 0.5 microns to 100 microns.
11. The article of claim 1 , further including one or more overcoat layers positioned over the coating.
12. The article of claim 11 , 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.
13. The article of claim 1 , wherein the coating includes a subtractive colorant in the ultraviolet (UV) scattering porous polymer particles or in the binder material.
14. The article of claim 1 , wherein the binder material is an organic polymeric material.
15. The article of claim 14 , wherein the organic polymeric material has an aromaticity of less than 10% of the coating.
16. The article of claim 1 , wherein the substrate is a metal or has a metalized surface.
17. The article of claim 1 , wherein the ultraviolet (UV) UV scattering porous polymer particles have a porosity in a range of 10-60%.
18. The article of claim 1 , wherein no more than 5% of the coating corresponds to interstitial voids not filled with binder.
19. The article of claim 1 , wherein the article is a textile.