Complex retroreflective bead
A retroreflective composite bead for highway marking having high retroreflectivity both when initially installed and over the bead lifetime, allowing vehicle drivers to see highway marking lines at night and in adverse conditions during nighttime. When installed the retroreflective beads essentially retroreflect the base color of the highway marking material in which the retroreflective beads are embedded. The beads comprise a larger bead with a coating of smaller particles heat bonded to its surface.
1. A retroreflective article comprising:
a. a glass central bead component coated with an organo-metallic interfacial modifier forming a coated bead; and
b. a plurality of peripheral smaller globular glass components, forming surface array on the coated bead in the absence of a conventional adhesive;
wherein the combination of central glass bead, peripheral bead and interfacial modifier can be sintered to form the retroreflective article with the array of peripheral components bonded to the central glass bead.
2. The article of claim 1 in which the central component is in the range of from about 0.6 to about 2.0 mm and the peripheral component are in the range of from about 40 μ to 200 μ.
3. The article of claim 1 wherein the central component and peripheral components are heat bonded.
4. The article of claim 1 wherein the central component is of a generally spherical configuration.
5. The article of claim 3 wherein the peripheral components are of a generally spherical configuration.
6. The article of claim 1 wherein the interfacial modifier coating is applied to the central component at 0.2 to 2 wt. % based on the central component.
7. The article of claim 1 wherein the interfacial modifier coating is applied to the peripheral component at 0.2 to 2 wt. % based on the peripheral components.
8. The article of claim 1 wherein the interfacial modifier coating the central component comprises a continuous layer having a thickness of less than about 0.5 micron.
9. The article of claim 1 wherein the interfacial modifier coating the peripheral components comprise a continuous layer having a thickness of less than about 0.5 micron.
10. The article of claim 1 wherein a ratio of diameter of globular central component to the peripheral globular glass components is greater than 10:1.
11. The article of claim 1 wherein a ratio of diameter of globular central component to the peripheral globular glass components is greater than 15:1.