Retroreflective glass or plastic beads have fluorescent properties when irradiated with ultraviolet light and are emplaced in signs in patterns indicative of alphanumeric characters, or embedded in... Show moreRetroreflective glass or plastic beads have fluorescent properties when irradiated with ultraviolet light and are emplaced in signs in patterns indicative of alphanumeric characters, or embedded in a hot melt comprising road stripes or embedded in the road asphalt or aggregate during construction of the road, to provide effectively bright and clear indications of signs or the extent and direction of the road. The glass beads comprise spherodized soda lime, borosilicate, phosphosilicate or aluminosilicate glasses with low levels of rare-earth dopants mixed therein, such as compounds containing one of the rare earths, or lanthanides. The plastic beads may have fluorescent materials mixed therein, typically organic pigments or dyes based on coumarin and rhodamine or the like. Show less
