Cube corner cavity based retroreflectors and methods for making same

• US 6,287,670 B1
• Filed: 01/11/1999
• Issued: 09/11/2001
• Est. Priority Date: 01/11/1999
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Smith, Kenneth L., Benson, Gerald M., Coderre, James C.
• Primary Examiner(s): Loney, Donald J.
• Application Number:
  US09/227,963
• Time in Patent Office: 974 Days
• Field of Search: 428/192, 428/172, 428/141, 428/148, 428/161, 428/164, 428/913, 428/156, 428/209, 428/131, 428/137, 359/529, 359/530
• US Class Current: 428/172
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: Y10T 428/24413 Metal or metal compound
• CPC Class Codes: Y10T 428/24479 including variation in thickness
• CPC Class Codes: Y10T 428/24521 with component conforming to contour of nonplanar surface
• CPC Class Codes: Y10T 428/24529 and conforming component on an opposite nonplanar surface
• CPC Class Codes: Y10T 428/24545 Containing metal or metal compound
• CPC Class Codes: Y10T 428/24612 Composite web or sheet
• CPC Class Codes: Y10T 428/24851 Intermediate layer is discontinuous or differential
• CPC Class Codes: Y10T 428/24917 including metal layer
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/31 Surface property or characteristic of web, sheet or block

Abstract

Retroreflective sheeting includes a body layer having a structured surface with recessed faces and top surfaces, the recessed faces forming cube corner cavities. The recessed faces have a high specular reflectivity, while the top surfaces have a low specular reflectivity. In some embodiments a substantially continuous film of reflective material covers the structured surface, and a masking substance is provided over the reflective material at the top surfaces. Alternatively, the top surfaces are given a non-smooth surface finish so that the film of reflective material on those portions has a diffuse reflectivity. In other embodiments the film of reflective material is discontinuous, disposed selectively on the recessed faces and not on the top surfaces. A cover layer is also provided, and can bond at least to the top surfaces. Keeping the top surfaces substantially free of reflective material inhibits corrosion and can enhance the bond integrity. The top surfaces are preferably flat, and diffusely reflective to enhance the daytime whiteness of the sheeting.

Claims

1. A cube corner article, comprising:

a body layer having a structured surface comprising recessed faces and top surfaces, wherein the top surfaces have a width, and the recessed faces defining cube corner cavities; and

a film of reflective material exposed selectively on the recessed faces of the structured surface.

2. The article of claim 1, wherein the film is substantially continuous.

3. The article of claim 2, further comprising:

a masking material disposed selectively on the top surfaces and covering the film.

4. The article of claim 3, wherein the masking material is diffusely reflective.

5. The article of claim 4, wherein the masking material is substantially white.

6. The article of claim 3, wherein the masking material is substantially opaque.

7. The article of claim 1, wherein the film is discontinuous.

8. The article of claim 7, wherein the film is substantially absent from at least some of the top surfaces.

9. The article of claim 8, wherein the film is substantially absent from all of the top surfaces, and the structured surface consists essentially of the recessed faces and the top surfaces.

10. The article of claim 8, wherein the body layer is exposed at the at least some of the top surfaces, the body layer comprising a diffusely reflective material.

11. The article of claim 7, wherein the body layer is transparent.

12. The article of claim 7, wherein the reflective material comprises silver.

13. The article of claim 1, wherein the structured surface comprises intersecting sets of parallel ridges.

14. The article of claim 13, wherein the ridges within at least one of the sets of parallel ridges have upper portions with differing transverse dimensions.

15. The article of claim 14, wherein the upper portions of ridges for at least two of the sets of parallel ridges have differing transverse dimensions.

16. The article of claim 1, wherein the cube corner cavities comprise cube corner cavities of differing aperture size.

17. The article of claim 1, further comprising:

a substantially transparent cover layer that covers the structured surface.

18. The article of claim 1, further comprising:

an adhesive applied to a rear surface of the body layer.