Self-cleaning UV reflective coating
A photo-catalytic overcoat on a UV reflective paint layer is employed to maintain high reflectance for long periods of time by continuously removing organic films when exposed to UV light. Advantageously, nano-particles comprising the photo-catalytic overcoat are composed of a semiconductor material that lead to the production of oxygen and hydroxyl free radicals when illuminated with UV light in the presence of water vapor. Some of these free radicals oxidize organic surface films, converting the surface films into gaseous H 2 O and CO 2 . This reduces the amount of organic deposits on the surface of the reflective paint layer.
1. An enhanced ultra-violet (UV) light reflector comprising: an ultra-violet light reflective substrate; and a plurality of nano-particles of a photo-catalytic material partially embedded in said substrate, said nano-particles covering 0.01% to 5.0% of a surface area of said substrate so as to not materially affect UV reflectance, where said photo-catalytic material is a semiconductor material that leads to production of oxygen and hydroxyl free radicals when illuminated with ultra-violet light in the presence of water.
2. The reflector of claim 1 wherein said plurality of nano-particles cover about one percent of a surface area of said substrate.
3. The reflector of claim 2 wherein said photo-catalytic material is TiO 2 .
4. The reflector of claim 1 wherein said nano-particles have a size of between 0.5 nm and 1,000 nm.
5. The reflector of claim 4 wherein said nano-particles have a size of about 25 nm.