Illuminated signage using quantum dots
An illuminated sign has a primary light source in spaced apart relation to a transparent or translucent substrate having quantum dot phosphors printed or coated thereon. The primary light source may be a blue LED, a white LED or an LED having a significant portion of its emission in the ultraviolet region of the spectrum. The LED may be a backlight for the transparent or translucent substrate and/or an edge light, a down light or an up light.
1. An illuminated sign comprising:
an enclosure having at least one transparent or translucent surface;
a light source within the enclosure configured to illuminate the transparent or translucent surface with primary light;
a light diffuser located between the light source and the transparent or translucent surface; and,
a plurality of quantum dots adhered to the transparent or translucent surface in a preselected pattern, said quantum dots emitting secondary light in response to excitation by the primary light,
wherein the sign illumination is a blend of the primary light and the secondary light.
2. An illuminated sign as recited in claim 1 wherein the preselected pattern comprises alphanumeric characters.
3. An illuminated sign as recited in claim 1 wherein the preselected pattern comprises a graphics pattern.
4. An illuminated sign as recited in claim 1 wherein the light source comprises light-emitting diodes that emit predominately in the blue portion of the visible spectrum or in the ultraviolet portion of the electromagnetic spectrum.
5. An illuminated sign as recited in claim 1 wherein the quantum dots comprise a core of II-VI, II-V, III-V, IV or IV-VI semiconductor material.
6. An illuminated sign as recited in claim 5 wherein the quantum dots comprise a core of heavy metal-free semiconductor material.
7. An illuminated sign as recited in claim 6 wherein the heavy metal-free quantum dots comprise a core comprising indium and phosphorus and optionally comprising one or more elements selected from the group consisting of zinc, sulphur, and selenium.
8. An illuminated sign as recited in claim 5 wherein the heavy metal-free quantum dot cores are shelled with one or more layers comprised of heavy metal-free II-VI and/or III-V semiconductor material and/or their ternary and quaternary alloys.
9. An illuminated sign as recited in claim 1 wherein the quantum dots are adhered to the translucent surface as a component of dried ink.
10. An illuminated sign as recited in claim 9 further comprising an oxygen barrier coating applied to the dried ink.
11. An illuminated sign as recited in claim 10 wherein the oxygen barrier coating comprises butyl rubber.
12. An illuminated sign as recited in claim 1 wherein the quantum dots are contained within polymer beads.
13. An illuminated sign as recited in claim 1 wherein the quantum dots are contained within the pores of a porous polymer.
14. An illuminated sign as recited in claim 1 comprising a solid-state light emitting diode and a quantum dot phosphor at a location remote from the light-emitting diode.
15. The illuminated sign recited in claim 1 wherein the transparent or translucent surface is a surface of the light diffuser.