PRISMATIC RETROREFLECTIVE SHEETING WITH REDUCED RETROREFLECTIVITY OF INFRA-RED LIGHT

• US 20120200710A1
• Filed: 10/12/2010
• Published: 08/09/2012
• Est. Priority Date: 10/16/2009
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Nakajima, Toshitaka, Yokoyama, Masami, Muramoto, Akira
• Granted Patent: US 9,519,087 B2
• Time in Patent Office: Days
• US Class Current: 348/148
• CPC Class Codes: B60R 13/10 Registration, licensing, or like devices
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• 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

Abstract

The present application relates to retroreflective sheeting that is capable of use in a license plate and that can be accurately read and/or detected by an ALPR system. The retroreflective sheeting is a prismatic retroreflective sheeting that provides reduced retroreflectivity of infra-red light. The retroreflective sheeting can also be a prismatic retroreflective sheeting that exhibits reduced retroreflectivity of incident infra-red light and substantially unaffected retroreflectivity of incident visible light.

Claims

1. A retroreflective sheet, comprising:

cube corner elements;

a reflector layer adjacent to the cube corner elements; and

an infra-red non-transmissive material.

2. The retroreflective sheet of claim 1, wherein the cube corner elements are one of full cubes, truncated cubes, cube corner type trigonal pyramids, cube corner type cavities, and the like.

3. The retroreflective sheet of claim 1, further including a whiteness-enhancing material.

4. The retroreflective sheet of claim 1, wherein the reflector layer includes one of a mirror-surfaced reflection layer and a multi-layer optical film.

5. The retroreflective sheet of claim 1, further including at least one of a protective layer and a sealing film.

6. The retroreflective sheet of claim 1, wherein the infra-red non-transmissive material forms a separate layer.

7. The retroreflective sheet of claim 1, wherein the infra-red non-transmissive material is in the cube corner elements.

8. The retroreflective sheet of claim 3, wherein the whiteness-enhancing material is in the cube corner elements.

9. The retroreflective sheet of claim 3, wherein the whiteness-enhancing material and the infra-red non-transmissive material form a separate layer.

22. A license plate utilizing the retroreflective sheet according to claim 1.

23. An ALPR system, comprising:

a license plate according to claim 22;

a light source that directs light at the license plate; and

a machine capable of imaging the license plate.

10. A retroreflective sheet, comprising:

cube corner elements;

a reflector layer adjacent to a backside of the cube corner elements; and

an infra-red non-transmissive layer adjacent to a front side of the cube corner elements.

11. The retroreflective sheet of claim 10, further including at least one of a protective layer and a sealing layer.

12. The retroreflective sheet of claim 10, wherein the cube corner elements are one of full cubes, truncated cubes, cube corner type trigonal pyramids, cube corner type cavities, and the like.

13. The retroreflective sheet of claim 10, further including a whiteness-enhancing material deposited on the infra-red non-transmissive layer.

14. The retroreflective sheet of claim 10, wherein the reflector layer includes one of a mirror-surfaced reflection layer and a multi-layer optical film.

25. A license plate utilizing the retroreflective sheet according to claim 10.

27. An ALPR system, comprising:

a license plate according to claim 25;

a light source that directs light at the license plate; and

a machine capable of imaging the license plate.

15. A retroreflective sheet, comprising:

cube corner elements including an infra-red non-transmissive material; and

a reflector layer adjacent to a backside of the cube corner elements.

16. The retroreflective sheet of claim 15, further including a whiteness-enhancing material.

17. The retroreflective sheeting of claim 16, wherein the whiteness-enhancing material is deposited into a front side of the cube corner elements.

18. The retroreflective sheet of claim 15, wherein the cube corner elements include a whiteness-enhancing material.

19. The retroreflective sheet of claim 15, further including at least one of a protective layer and a sealing layer.

20. The retroreflective sheet of claim 15, wherein the cube corner elements are one of full cubes, truncated cubes, cube corner type trigonal pyramids, cube corner type cavities, and the like.

21. The retroreflective sheet of claim 15, wherein the reflector layer includes one of a mirror-surfaced reflection layer and a multi-layer optical film.

26. A license plate utilizing the retroreflective sheet according to claim 15.

28. An ALPR system, comprising:

a license plate according to claim 26;

a light source that directs light at the license plate; and

a machine capable of imaging the license plate.

24. (canceled)