Low specular reflectance surface
A low-specular-reflectance surface, includes a coating on a surface, wherein the coating includes a plurality of substantially spherical particles having a multimodal particle size distribution, wherein the particles protrude from a top surface of the coating to provide substantially spherical caps. The multimodal particle size distribution has 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. A ratio of the second particle size to the first particle size is between 1.7-4.0. A smallest of the mode particle sizes is greater than or equal to 1.0 microns, and a largest of the mode particle sizes is greater than or equal to 3.0 microns.
1. A low-specular-reflectance surface, comprising:
a coating on a surface, wherein the coating includes a plurality of substantially spherical particles having a multimodal particle size distribution, the particles protruding from a top surface of the coating to provide substantially spherical caps;
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 and 4.0;
wherein a smallest of the mode particle sizes is greater than or equal to 1.0 microns, and a largest of the mode particle sizes is greater than or equal to 3.0 microns;
wherein the coating includes a binder which adheres the particles to the surface; and
wherein a volume percent of the binder in the coating is less than a volume percent of the particles.
2. The low-specular-reflectance surface of claim 1 , wherein a total volume of the particles in the first mode is in the range of 20-70% of a total volume of all of the particles.
3. The low-specular-reflectance surface of claim 1 , wherein a total volume of the particles in the second mode is in the range of 20-70% of a total volume of all of the particles.
4. The low-specular-reflectance surface of claim 1 , wherein the distribution function further includes a third mode having a third peak corresponding to a third particle size, and wherein a ratio of the third particle size to the second particle size is between 1.7 and 4.0.
5. The low-specular-reflectance surface of claim 4 , wherein a total volume of the particles in the third mode is between 10-40% of a total volume of all of the particles.
6. The low-specular-reflectance surface of claim 4 , wherein the distribution function further includes a fourth mode having a fourth peak corresponding to a fourth particle size, and wherein a ratio of the fourth particle size to the third particle size is between 1.7 and 4.0.
7. The low-specular-reflectance surface of claim 1 , wherein the mode width parameter for each of the modes is less than or equal to 0.6.
8. The low-specular-reflectance surface of claim 1 , wherein a minimum value of the distribution function between adjacent modes is no more than 50% of the adjacent mode peaks.
9. The low-specular-reflectance surface of claim 1 , wherein the particles are adhered to the surface with a binder.
10. The low-specular-reflectance surface of claim 1 , wherein the first particle size is at least 2 microns.
11. The low-specular-reflectance surface of claim 1 , wherein at least some of the particles are substantially transparent.
12. The low-specular-reflectance surface of claim 1 , wherein at least some of the particles include a colorant.
13. The low-specular-reflectance surface of claim 1 , wherein at least some of the particles are inorganic particles.
14. The low-specular-reflectance surface of claim 1 , wherein at least some of the particles are polymeric particles.
15. The low-specular-reflectance surface of claim 1 , wherein at least some of the particles are porous.
16. The low-specular-reflectance surface of claim 1 , wherein G20, G60 and G85 gloss values of the low-specular-reflectance surface are each no more than 3.0.
17. The low-specular-reflectance surface of claim 1 , wherein an onset of grazing-incidence specular reflection occurs at an incidence angle of at least 85 degrees.
18. The low-specular-reflectance surface of claim 1 , wherein the particles are distributed over the surface in substantially a monolayer.
19. A low-specular-reflectance surface, comprising:
a surface including a plurality of protruding substantially spherical caps having a multimodal size distribution;
wherein the multimodal size distribution has a distribution function having two or more modes, each mode having a peak defining an associated mode cap size, wherein the distribution function includes a first mode having a first peak corresponding to a first cap size and a second mode having a second peak corresponding to a second cap 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 cap size of the particular mode;
wherein a ratio of the second cap size to the first cap size is between 1.7 and 4.0;
wherein a smallest of the mode cap sizes is greater than or equal to 1.0 microns, and a largest of the mode cap sizes is greater than or equal to 3.0 microns; and
wherein the surface is the surface of a layer, and wherein the caps are molded features of the layer.
20. A low-specular-reflectance surface, comprising:
a surface including a plurality of protruding substantially spherical caps having a multimodal size distribution;
wherein the multimodal size distribution has a distribution function having two or more modes, each mode having a peak defining an associated mode cap size, wherein the distribution function includes a first mode having a first peak corresponding to a first cap size and a second mode having a second peak corresponding to a second cap 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 cap size of the particular mode;
wherein a ratio of the second cap size to the first cap size is between 1.7 and 4.0;
wherein a smallest of the mode cap sizes is greater than or equal to 1.0 microns, and a largest of the mode cap sizes is greater than or equal to 3.0 microns; and
wherein the surface is the surface of an object, and wherein the caps are molded features of the object.