Retroreflective articles and devices having viscoelastic lightguide

• US 8,651,720 B2
• Filed: 06/26/2009
• Issued: 02/18/2014
• Est. Priority Date: 07/10/2008
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Sherman, Audrey A., Boulos, Marie A., Schaffer, Kevin R., Meis, Michael A., Tran, Thu-Van T., Aeling, Ellen O., Widagdo, Soemantri
• Primary Examiner(s): Hanley, Britt D
• Assistant Examiner(s): Lee, Brenitra M
• Application Number:
  US13/002,810
• Publication Number:
  US 20110182076A1
• Time in Patent Office: 1,698 Days
• Field of Search: 362/297, 362/560
• US Class Current: 362/560
• CPC Class Codes: B42D 2035/20 Optical effects
• CPC Class Codes: B42D 25/29 Securities; Bank notes
• CPC Class Codes: B42D 25/324 Reliefs
• CPC Class Codes: B42D 25/328 Diffraction gratings; Holograms
• CPC Class Codes: B44F 1/045 having mirrors or metallic or reflective layers at the back side
• CPC Class Codes: F21V 13/04 the elements being reflectors and refractors for vehicle rear lights F21S43/40
• CPC Class Codes: G02B 5/12 Reflex reflectors
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0063 for extracting light out both the major surfaces of the light guide
• CPC Class Codes: G09F 13/18 Edge-illuminated signs

Abstract

Disclosed herein is an optical device having a light source, a viscoelastic lightguide and a retroreflective film suitable for retroreflecting light. Light from the light source enters the viscoelastic lightguide and is transported within the lightguide by total internal reflection. The transported light is extracted from the lightguide and retroreflected at a structured surface of the retroreflective film. The optical device may have a “front lit” or a “back lit” configuration depending on the relative positioning of the lightguide and the retroreflective film. The retroreflective film may include prismatic retroreflective sheeting, holographic film or film structured with diffraction gratings. The optical device may be used, for example, as a sign or marking, a license plate assembly, a tail light assembly for vehicles, a security laminate for protection of documents against tampering, or an illumination device.

Claims

1. An optical device comprising:

a light source;

a viscoelastic light guide comprising a pressure sensitive adhesive core, wherein light emitted by the light source enters the pressure sensitive adhesive core and is transported within the core by total internal reflection; and

a retroreflective film suitable for retroreflecting light, wherein light being transported within the viscoelastic lightguide is extracted from the lightguide and retroreflected from a structured surface of the retroreflective film.

2. The optical device of claim 1, wherein retroreflected comprises reflected by refraction.

3. The optical device of claim 1, wherein retroreflected comprises reflected by diffraction.

4. The optical device of claim 1, wherein at least about 80% of light being transported within the viscoelastic lightguide is extracted from the lightguide.

5. The optical device of claim 1, wherein the viscoelastic lightguide has a light transmittance of from about 90 to about 100% and a haze value of from about 0.01 to less than about 5%.

6. The optical device of claim 1, wherein the retroreflective film has a refractive index greater than that of the viscoelastic lightguide.

7. The optical device of claim 1, wherein the retroreflective film comprises prismatic retroreflective sheeting.

8. The optical device of claim 1, wherein the retroreflective film is disposed on a mirror.

9. The optical device of claim 1, wherein the viscoelastic layer is disposed on a printed graphic film.

10. The optical device of claim 1, wherein the viscoelastic layer is disposed on a holographic film.

11. The optical device of claim 1, wherein the retroreflective film comprises retroreflective sheeting, and the viscoelastic lightguide is disposed between the sheeting and a multilayer optical film comprising a three-quarter mirror.

12. An optical device comprising:

a light source;

a viscoelastic lightguide, wherein light emitted by the light source enters the viscoelastic lightguide comprising a pressure sensitive adhesive core and is transported within the core by total internal reflection; and

a retroreflective film suitable for retroreflecting light, wherein light being transported within the viscoelastic lightguide is extracted from the lightguide and transmitted through the retroreflective film.

13. The optical device of claim 12, wherein at least about 80% of light being transported within the viscoelastic lightguide is extracted from the lightguide.

14. The optical device of claim 12, wherein the viscoelastic lightguide has a light transmittance of from about 90 to about 100% and a haze value of from about 0.01 to less than about 5%.

15. The optical device of claim 12, wherein the retroreflective film has a refractive index greater than that of the viscoelastic lightguide.

16. The optical device of claim 12, wherein the retroreflective film comprises prismatic retroreflective sheeting.

17. The optical device of claim 12, wherein the retroreflective film is disposed on a mirror.

18. The optical device of claim 12, wherein the viscoelastic layer is disposed on a printed graphic film.

19. The optical device of claim 12, wherein the viscoelastic layer is disposed on a holographic film.

20. The optical device of claim 12, wherein the retroreflective film comprises retroreflective sheeting, and the viscoelastic lightguide is disposed between the sheeting and a multilayer optical film comprising a three-quarter mirror.

21. The optical device of claim 12, wherein the viscoelastic lightguide is disposed on a mirror.

22. The optical device of claim 12, wherein the retroreflective film comprises retroreflective sheeting, and the viscoelastic lightguide is disposed between the sheeting and a mirror.