INFRARED-TRANSMISSIVE, VISIBLE-LIGHT-ABSORPTIVE RETRO-REFLECTORS

• US 3,758,193 A
• Filed: 07/02/1971
• Issued: 09/11/1973
• Est. Priority Date: 07/02/1971
• Status: Expired due to Term

• Current Assignee: Chi Fang Tung
• Original Assignee: Chi Fang Tung
• Inventors: Tung, Chi Fang
• Primary Examiner(s): Schonberg, David
• Assistant Examiner(s): Tokar, Michael J.
• Application Number:
  US05/159,196
• Time in Patent Office: 802 Days
• Field of Search: 350/97-109,1 106/47,52-54
• US Class Current: 359/359
• CPC Class Codes: G02B 5/128 transparent spheres being embedded in matrix

Abstract

Retro-reflectors that incorporate, between the outer surface of the reflector and a reflective surface within the reflector, a thin layer of a material that transmits infrared radiation and substantially absorbs visible light. The layer comprises discrete, water-insoluble, organic, infrared-transmissive, visible-light-absorptive pigment particles dispersed in a matrix film having an index of refraction substantially the same as the index of refraction of the pigment particles and not substantially greater than the index of refraction of any material between the thin layer and said reflective surface.

Claims

2. A reflector of claim 1 in which the thin layer forms said exterior surface of the reflector.

3. A reflector of claim 1 in which the thin layer is separated from said exterior surface by another layer of material.

4. A reflector of claim 3 in which a monolayer of spherical glass beads is disposed between said exterior and reflective surfaces.

5. Infrared-transmissive, visible-light-absorptive retro-reflective sheeting comprising 1) a base retro-reflective sheeting that incorporates a dense monolayer of visibly transparent retro-reflective spherical glass beads covered with a visibly transparent material that provides a flat exterior surface of the sheeting through which radiation is received for reflection, and 2) a layer between 0.1 and 10 mils in thickness adhered over said flat exterior surface comprising a matrix film and solid discrete pigment partiCles of at least one water-insoluble organic infrared-transmissive visible-light-absorptive pigment dispersed in the matrix film at a particle volume concentration between 0.5 and 20 percent, the matrix film having an index of refraction that is substantially the same as the index of refraction of the pigment and is not substantially greater than the index of refraction of said visibly transparent material, and the layer having an IR/IR+V discrimination ratio of at least 75 percent.

6. Retro-reflective sheeting of claim 5 in which the organic pigment includes Lithosol Fast Scarlet, Benzedine Yellow, and Heliogen Blue.