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 material for creating roadway markers having a near-ideal retroreflectivity, the retroreflective material comprising:
a mesh made of a flexible compound; and
a plurality of discrete retroreflective elements made of a rigid material retained within the mesh in an array pattern that defines an incident material surface, each retroreflective element formed of one or more cube corner elements 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 material surface and each retroreflective element includes at least a front surface exposed to the incident material surface having a tilted surface normal angle of between about 2 degrees and 8 degrees relative to the normal of the incident material surface,
wherein each of the plurality of discrete retroreflective elements is configured to produce a near-ideal total internal reflection (TIR) when the retroreflective material is installed on a roadway.
2. The retroreflective material of claim 1 , wherein the retroreflective material is configured to be installed with a body layer presenting a generally flat surface corresponding to the incident surface and having a high transparency and a first index of refraction, and wherein each retroreflective element has a 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 retroreflective element.
3. The retroreflective material of claim 2 , wherein the retroreflective material produces a retroreflectivity of greater than 90% of light incident upon the incident surface over an angular performance range of entrance angles from 80 degrees to 90 degrees.
4. The retroreflective material of claim 1 , wherein the flexible compound is a plastic compound and the rigid material is a crystalline compound or element.
5. The retroreflective material of claim 4 , wherein the plastic compound consists of polycarbonate or acrylic and the crystalline compound or element consists of zirconium, crystallized carbon, or silicon carbide.
6. The retroreflective material of claim 1 , wherein the flexible compound is transparent to wavelengths of electromagnetic radiation from 400-1000 nanometers.
7. The retroreflective material of claim 1 , wherein the flexible compound is a degradable material.
8. The retroreflective material of claim 7 , wherein the degradable material consists of an ultraviolet degradable material or a water soluble degradable material.
9. The retroreflective material of claim 1 , wherein each retroreflective element has a thickness of less than 30 microns and an average diameter of the element that is less than 1 cm.
10. The retroreflective material of claim 1 , wherein each cube corner element has at least one surface having a surface roughness that ranges 0.0005 microns to 0.01 microns.
11. A retroreflective element comprising a cube corner element having at least one incident surface exposed to incident radiation and having a cube corner apex axis with an orientation generally tilted relative to a normal of the incident surface, wherein the element comprises at least about 10 percentage by weight TiO 2 , and wherein the element has an index of refraction of at least 2.3.
12. The element of claim 11 , wherein the element is transparent to wavelengths of light in a range selected from the set consisting of 400-700 nanometers, 400-1000 nanometers, and 400-1800 nanometers.
13. The element of claim 11 wherein the element comprises at least about 40 percentage by weight TiO 2 .
14. The element of claim 11 wherein the element comprises at least about 65 percentage by weight TiO 2 .
15. The element of claim 11 wherein the element further comprises at least about 0.5 percentage by weight CaO.
16. A retroreflective article formed of a plurality of the retroreflective elements of claim 11 in a binder material.
17. A retroreflective article formed of a plurality of the retroreflective elements of claim 11 configured in a mesh made of a flexible material.
18. A retroreflective article formed of a plurality of the retroreflective elements of claim 11 configured in a body layer presenting a generally flat incident surface and having a high transparency.