Self-cleaning UV reflective coating

• US 7,288,232 B2
• Filed: 09/24/2001
• Issued: 10/30/2007
• Est. Priority Date: 09/24/2001
• Status: Expired due to Fees

• Current Assignee: L2B Environmental Systems Incorporated
• Original Assignee: L2B Environmental Systems Incorporated
• Inventors: McLean, Larry James, Morrow, William H.
• Primary Examiner(s): Mayekar; Kishor
• Application Number:
  US09/961,632
• Publication Number:
  US 20030059549A1
• Time in Patent Office: 2,227 Days
• Field of Search: 428/688, 428/689, 422/186.3, 422/121
• US Class Current: 422/186.3
• CPC Class Codes: C09D 1/00 Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
• CPC Class Codes: C09D 17/008 Titanium dioxide
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/263 Coating layer not in excess of 5 mils thick or equivalent

Abstract

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 H₂O and CO₂. This reduces the amount of organic deposits on the surface of the reflective paint layer.

Claims

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 TiO₂.

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.