Retroreflective materials and articles incorporating near-ideal total internal retroreflective elements
Retroreflective materials and articles are enabled that increase the retroreflectivity of reflective materials or articles for roadway, automotive, and safety purposes by incorporating retroreflective elements that exhibit near-ideal Total Internal Reflection (TIR).
1. A retroreflective article having a near-ideal retroreflectivity comprising:
a body layer presenting a generally flat incident surface and having a high transparency and a first index of refraction; and
a plurality of discrete, rigid retroreflective elements incorporated with the body layer, each retroreflective element having:
an array of cube corner elements defining a plane parallel with the incident surface with at least some of the cube corner elements having an apex axis having an orientation generally tilted relative to a normal of the incident surface; and
material affixed to the cube corner surfaces with a second index of refraction such that a refractive index ratio of the second index of refraction to the first index of refraction is sufficiently high to produce a high degree of total internal reflection (TIR) of light incident upon the incident surface such that the retroreflective article produces a retroreflectivity of greater than 90% of light incident upon the incident surface that is the near-ideal retroreflectivity,
wherein the plurality of discrete, rigid retroreflective elements are aligned within the body to form a mesh pattern, and
wherein the cube corner elements have a surface roughness of each face of the cube corner element that ranges 0.0005 microns to 0.01 microns.
2. The retroreflective article of claim 1 , wherein the body layer is transparent to wavelengths of light from 400-1000 nanometers.
3. The retroreflective article of claim 1 , wherein the is determined for light incident upon the incident surface over an angular performance range of entrance angles from 80 degrees to 90 degrees.
4. The retroreflective article of claim 3 , wherein the retroreflectivity over the angular performance range is essentially similar for both dry and wet conditions.
5. The retroreflective article of claim 3 , wherein the retroreflectivity is greater than 95% of light incident upon the incident surface over the angular performance range.
6. The retroreflective article of claim 5 , wherein the retroreflectivity is greater than 98% of light incident upon the incident surface over the angular performance range.
7. The retroreflective article of claim 1 , wherein the body layer comprises a sheet of flexible material.
8. The retroreflective article of claim 1 , wherein the body layer comprises a binder material.
9. The retroreflective article of claim 1 , wherein the body layer comprises a road surface material.
10. The retroreflective article of claim 9 , wherein the body layer further comprises an adhesive layer intermediate at least a portion of the road surface material and at least one of the plurality of retroreflective elements.
11. The retroreflective article of claim 1 , wherein each retroreflective element has a thickness of less than 30 microns.
12. The retroreflective article of claim 1 , wherein each cube corner element comprises a single near-ideal TIR retroreflective element having eighteen cube corner faces organized as six groups each of three cube corner faces with each of the faces of the cube corner groups aligned generally 90 degrees from each other.
13. The retroreflective article of claim 1 , where each retroreflective element comprises a configuration of multiple near-ideal TIR retroreflective elements, each near-ideal TIR retroreflective element comprising a subset of the array of cube corner elements.
14. The retroreflective article of claim 13 , wherein each near-ideal TIR retroreflective element has a flat upper surface having an average width in the range of 0.2 to 20 millimeters.
15. The retroreflective article of claim 13 , wherein each near-ideal TIR retroreflective element has an aspect ratio of an average diameter to an average depth of 4:1 or greater.
16. The retroreflective article of claim 1 , wherein each retroreflective element has an average diameter of the element that is less than 1 cm.
17. The retroreflective article of claim 1 , wherein each retroreflective element has an average diameter of the element that is less than 0.1 cm.
18. The retroreflective article of claim 1 , wherein the retroreflective element is made of a material consisting of zirconium, crystallized carbon, or silicon carbide.
19. The retroreflective article of claim 1 , wherein the retroreflective article is incorporated as part of an article selected from the set consisting of: a roadway marker, a road sign, a conspicuity material, and a safety garment.