Optically active materials and articles and systems in which they may be used

• US 9,581,740 B2
• Filed: 05/02/2014
• Issued: 02/28/2017
• Est. Priority Date: 12/15/2008
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Smithson, Robert L. W., Biernath, Rolf W.
• Primary Examiner(s): POWERS, LAURA C
• Application Number:
  US14/268,469
• Publication Number:
  US 20140285889A1
• Time in Patent Office: 1,033 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: B60R 13/10 Registration, licensing, or like devices
• CPC Class Codes: G02B 5/0816 Multilayer mirrors, i.e. having two or more reflecting layers G02B5/0883, G02B5/0891 take precedence
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: G02B 5/128 transparent spheres being embedded in matrix
• CPC Class Codes: G02B 5/136 plural reflecting elements forming part of a unitary body G02B5/124 takes precedence
• CPC Class Codes: G02B 5/208 for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation
• CPC Class Codes: G02B 5/26 Reflecting filters G02B5/28 takes precedence
• CPC Class Codes: G06V 10/143 Sensing or illuminating at different wavelengths
• CPC Class Codes: G06V 20/625 License plates
• CPC Class Codes: G09F 13/16 Signs formed of or incorporating reflecting elements or surfaces, e.g. warning signs having triangular or other geometrical shape
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor
• CPC Class Codes: Y10T 428/24802 Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]

Abstract

The inventors of the present application developed novel optically active materials, methods, and articles. One embodiment of the present application is an optically active article, comprising: an infrared-reflecting material positioned adjacent to an optically active substrate such that the infrared-reflecting material forms a pattern that can be read by an infrared sensor when the optically active substrate is illuminated by an infrared light source. Another embodiment of the present application relates to a method of manufacturing an optically active article, comprising: obtaining an optically active sheeting; and positioning an infrared-reflecting material on the optically active sheeting to form a pattern. The optically active article may be, for example, a license plate.

Claims

1. A method of manufacturing a retroreflective article, comprising:

obtaining a retroreflective sheeting; and

positioning an infrared-reflecting multi-layer optical film on the retroreflective sheeting to form a pattern;

wherein the infrared-reflecting multi-layer optical film is transparent and not significantly visible in the visible light spectrum; and

wherein the retroreflective sheeting causes incident light to retroreflect via a retroreflective light path, and wherein the infrared-reflecting multi-layer optical film causes incident infrared light to be reflected from the retroreflective light path.

2. The method of claim 1, wherein the article is a street sign, a signage used for traffic control purposes, a license plate, a validation sticker, a usage permit, an identification label, or a tag.

3. The method of claim 1, further comprising:

affixing the retroreflective sheeting to a license plate base.

4. The method of claim 1, further comprising illuminating the retroreflective sheeting with an infrared light source to facilitate reading of the pattern by an infrared sensor.

5. The method of claim 1, wherein the retroreflective sheeting is one of prismatic sheeting or beaded sheeting.

6. The method of claim 1, wherein the pattern includes at least one of machine readable information, graphics, images, alphanumeric characters, bar code, or other indicia.

7. A retroreflective article comprising:

retroreflective sheeting; and

an infrared-reflecting multi-layer optical film disposed on at least a portion of the retroreflective sheeting, wherein infrared-reflecting multi-layer optical film is not significantly visible in the visible light spectrum; and

wherein the retroreflective sheeting retroreflects incident light via a retroreflective light path, and wherein the infrared-reflecting multi-layer optical film causes incident infrared light to be reflected from the retroreflective light path.

8. The retroreflective article of claim 7, wherein the infrared-reflecting multi-layer optical film forms a pattern.

9. The retroreflective article of claim 8, wherein the pattern includes at least one of machine readable information, a graphic, an image, an alphanumeric characters, a bar code, or other indicia.

10. A retroreflective sign comprising the retroreflective sheeting of claim 7.

11. A retroreflective sign comprising:

retroreflective sheeting including covert indicia, wherein the covert indicia in the form of a pattern is infrared-reflecting multi-layer optical film and not significantly visible in the visible light spectrum;

wherein the retroreflective sheeting retroreflects incident light via a retroreflective light path, and wherein the infrared-reflecting multi-layer optical film causes infrared light to be reflected from the retroreflective light path.

12. The retroreflective sign of claim 11, wherein the covert indicia forms a pattern that can be read by an infrared sensor.

13. The retroreflective sign of claim 11, wherein the covert indicia includes at least one of an alphanumeric character, a sinusoidal curve, a bar code, a design, an image, a symbol, a machine-readable information, a graphic, or information selected from the group consisting of signage material lot number, installation date, reorder information and product life expectancy.

14. The retroreflective sign of claim 11, wherein the retroreflective sign is one of a highway sign, a traffic sign or a street sign.