US Patent 7513941 Pavement marking, reflective elements, and methods of making micospheres

Presently described are retroreflective articles, such as pavement markings, that comprise transparent microspheres partially embedded in a (e.g. polymeric) binder. Also described are (e.g. glass-ceramic) microspheres, methods of making microspheres, as well as compositions of glass materials and compositions of glass-ceramic materials. The microspheres generally comprise lanthanide series oxide(s), titanium oxide (TiO2), and optionally zirconium oxide (ZrO2).