Retroreflective articles and devices having viscoelastic lightguide

• US 9,086,535 B2
• Filed: 07/09/2009
• Issued: 07/21/2015
• 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., Meis, Michael A., Schaffer, Kevin R., Tran, Thu-Van T.
• Primary Examiner(s): Wong, Tina
• Application Number:
  US13/003,193
• Publication Number:
  US 20110122494A1
• Time in Patent Office: 2,203 Days
• Field of Search: 385/31, 385/33, 385/35, 385129-132, 385/146, 362/296.01, 362297-300, 359/515, 359/530, 359/534, 359536-541, 359/546
• US Class Current: 1/1
• CPC Class Codes: G02B 5/128 transparent spheres being embedded in matrix
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G09F 13/0472 Traffic signs
• 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

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 optical device may have a “front lit” configuration such that light being transported within the lightguide is extracted and retroreflected by the film toward a viewer. The optical device may have a “back lit” configuration such that light being transported within the lightguide is extracted and transmitted through the film toward a viewer. The retroreflective film may comprise beaded retroreflective sheeting such as that used in traffic signs and markings.

Claims

1. An optical device comprising:

a light source;

a viscoelastic lightguide, wherein light emitted by the light source enters the viscoelastic lightguide and is transported within the lightguide by total internal reflection; and

a retroreflective film suitable for retroreflecting light and comprising

a layer of transparent microspheres and

reflective material disposed in back of the layer;

wherein the viscoelastic lightguide is disposed in front of the layer of transparent microspheres such that light being transported within the viscoelastic lightguide is extracted from the lightguide and retroreflected by the transparent microspheres;

wherein the viscoelastic lightguide comprises a pressure sensitive adhesive; and

wherein the light emitted by the light source is transported within the pressure sensitive adhesive of the viscoelastic lightguide.

2. The optical device of claim 1, the retroreflective film further comprising a binder, wherein the transparent microspheres are partially embedded in the binder, and the reflective material is disposed between the microspheres and the binder.

3. The optical device of claim 1, the retroreflective film further comprising a transparent binder, wherein the transparent microspheres are completely embedded in the transparent binder, and the reflective material is disposed between the microspheres and the transparent binder.

4. The optical device of claim 1, wherein the reflective material is discontinuous across the retroreflective film.

5. The optical device of claim 1, wherein the reflective material forms a reflective layer.

6. The optical device of claim 1, wherein the reflective material is a reflective binder, and the transparent microspheres are partially embedded in the reflective binder.

7. The optical device of claim 1, the retroreflective film further comprising a transparent binder, wherein the transparent microspheres are at least partially embedded in the transparent binder, and the transparent binder is disposed between the viscoelastic lightguide and the layer of transparent microspheres.

8. The optical device of claim 1, the retroreflective film further comprising a transparent binder, wherein the transparent microspheres are at least partially embedded in the transparent binder, the transparent binder is disposed between the viscoelastic lightguide and the layer of transparent microspheres, and the transparent binder and the reflective material are in direct contact with each other.

9. The optical device of claim 1, the retroreflective film further comprising a transparent binder, wherein the transparent microspheres are at least partially embedded in the transparent binder, the transparent binder is disposed between the viscoelastic lightguide and the layer of transparent microspheres, and the transparent binder and the reflective material are not in direct contact with each other.

10. The optical device of claim 1, the retroreflective film further comprising a transparent binder, wherein the transparent microspheres are at least partially embedded in the transparent binder, and the transparent binder is disposed between the transparent microspheres and the reflective material.

11. The optical device of claim 1, the retroreflective film further comprising a transparent binder, wherein the transparent microspheres are at least partially embedded in the transparent binder, the transparent binder is disposed between the transparent microspheres and the reflective material, and the reflective material forms a reflective layer.

12. The optical device of claim 1, the retroreflective film further comprising a cover film disposed in front of the transparent microspheres and supported by a network of walls extending from the reflective material to the cover film such that at least some of the transparent microspheres are surrounded by the walls.

13. The optical device of claim 1, the retroreflective film further comprising a cover film disposed in front of the transparent microspheres and supported by a network of walls extending from the reflective material to the cover film, wherein at least some of the transparent microspheres are grouped together by the walls.

14. The optical device of claim 1, wherein the viscoelastic lightguide is in direct contact with the retroreflective film.

15. The optical device of claim 1, further comprising one or more optional layers, the optional layers comprising:

a first optional layer disposed between the viscoelastic lightguide and the retroreflective film,

a second optional layer disposed on the viscoelastic lightguide opposite the retroreflective film, and

a third optional layer disposed on the retroreflective film opposite the viscoelastic lightguide.

16. The optical device of claim 1, wherein an image is provided by one or more of:

the viscoelastic lightguide,

a first optional layer disposed between the viscoelastic lightguide and the retroreflective film, and

a second optional layer disposed on the viscoelastic lightguide opposite the retroreflective film.

17. The optical device of claim 1, wherein an image is provided by one or more of:

an imaging layer disposed between the layer of transparent microspheres and the reflective material,

an imaging layer disposed between the retroflective film and the viscoelastic lightguide, and

an imaging layer disposed on the viscoelastic lightguide opposite the retroreflective film.

18. An optical device comprising:

a light source;

a viscoelastic lightguide, wherein light emitted by the light source enters the viscoelastic lightguide and is transported within the lightguide by total internal reflection; and

a retroreflective film suitable for retroreflecting light and comprising a layer of transparent microspheres and not comprising reflective material disposed in back of the layer;

wherein the viscoelastic lightguide is disposed in front of the layer of transparent microspheres such that light being transported within the viscoelastic lightguide is extracted from the lightguide and retroreflected by the transparent microspheres;

wherein the viscoelastic lightguide comprises a pressure sensitive adhesive; and

wherein the light emitted by the light source is transported within the pressure sensitive adhesive of the viscoelastic lightguide.

19. An optical device comprising:

a light source and an optical device, the optical device comprising;

a viscoelastic lightguide, wherein light emitted by the light source enters the viscoelastic lightguide and is transported within the lightguide by total internal reflection; and

a retroreflective film suitable for retroreflecting light and comprising

a layer of transparent microspheres, and

reflective material associated with each transparent microsphere and disposed in back of each transparent microsphere;

wherein the viscoelastic lightguide is disposed in front of the layer of transparent microspheres such that light being transported within the viscoelastic lightguide is extracted from the lightguide and retroreflected by the transparent microspheres,

wherein the viscoelastic lightguide comprises a pressure sensitive adhesive;

wherein the light emitted by the light source is transported within the pressure sensitive adhesive of the viscoelastic lightguide; and

the reflective material associated with each transparent microsphere forms an individual image, and a composite image is formed by the individual images such that the composite image appears to the unaided eye to float in front of the layer of transparent microspheres.

20. An optical device comprising:

a light source and an optical device, the optical device comprising;

a viscoelastic lightguide, wherein light emitted by the light source enters the viscoelastic lightguide and is transported within the lightguide by total internal reflection; and

a reflective film suitable for reflecting light and comprising

a layer of transparent microspheres, and

reflective material associated with each transparent microsphere and disposed in back of each transparent microsphere;

wherein the viscoelastic lightguide is disposed in back of the layer of transparent microspheres such that light being transported within the viscoelastic lightguide is extracted from the lightguide and transmitted through each of the transparent microspheres,

wherein the viscoelastic lightguide comprises a pressure sensitive adhesive;

wherein the light emitted by the light source is transported within the pressure sensitive adhesive of the viscoelastic lightguide; and

the reflective material associated with each transparent microsphere forms an individual image, and a composite image is formed by the individual images such that the composite image appears to the unaided eye to float in back of the optical device.