| dc.description.abstract | Street and highway signs are made from a layered retroreflective material fastened to an aluminum back plate. The retroreflective material uses microspherical glass lenses, commonly called glass beads, as the active optical element. These glass beads have a refractive index of either 1.9 or 2.2. Owing to product construction constraints, a glass bead of 2.9 refractive index would allow products to be developed having improved brightness, simplified construction, and longer sign life. The research presented here involved the preparation of sample quantities of glass beads ranging from 2.5 to 2.9 refractive index from proprietary formulations. The scope of this experiment was limited to crucible batching and melting, hand crushing and screening, and small scale forming into microspheres. The glass crushing and forming equipment was constructed from common farm and laboratory apparatus. Finally, the retroreflective property of the 2.9 refractive index beads produced was demonstrated in a simple product simulation. The author of this research, Clark G. Kuney Jr. is also the author of U.S. Patent Number 4,957,335 titled “Microsphere-based Retroreflective Articles With Enhanced Retroreflective Brightness” and is considered a past authority on the subjects of both microsphere formulations and processing. | |
