Illumination device having viscoelastic layer

• US 9,239,417 B2
• Filed: 02/09/2011
• Issued: 01/19/2016
• Est. Priority Date: 02/10/2010
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Wolk, Martin B., Sykora, Michael J., Brott, Robert L., Bryan, William J., Aho, Erik A., Kristoffersen, Martin, Meis, Michael A., Schaffer, Kevin R., Sherman, Audrey A., Schultz, John C., Mazurek, Mieczyslaw H.
• Primary Examiner(s): TSO, LAURA K
• Application Number:
  US13/577,692
• Publication Number:
  US 20130170218A1
• Time in Patent Office: 1,805 Days
• Field of Search: 362/618, 362/627, 362/326, 362/330, 362/336, 362/337, 362/339
• US Class Current: 1/1
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 6/0001 specially adapted for lighting devices or systems lighting or signalling on vehicles using light guides B60Q1/00; lighting devices for vehicle dashboards B60Q3/10; lighting devices for vehicle interior using light guides B60Q3/62; lighting devices mounted on the vehicle rear part using light guides F21S43/235; measuring arrangements having light conducting pointers G01D13/265; illumination of liquid crystal displays G02F1/1336; illuminated signs G09F13/00
• CPC Class Codes: G02B 6/0035 provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: Y10S 977/78 Possessing fully enclosed nanosized voids or physical holes
• CPC Class Codes: Y10S 977/932 for electronic or optoelectronic application

Abstract

An illumination device, such as a backlight for electronic display devices, is disclosed. The illumination device includes a lightguide optically coupled to a light source, and a viscoelastic layer and a nanovoided polymeric layer are used in conjunction with the lightguide to manage light emitted by the light source. The viscoelastic layer may be a pressure sensitive adhesive.

Claims

1. An illumination device comprising:

a light source; and

an optical article comprising;

a lightguide,

a viscoelastic layer disposed on the lightguide, and

a nanovoided polymeric layer disposed on the viscoelastic layer opposite the lightguide, the nanovoided polymeric layer comprising a plurality of interconnected nanovoids, at least some of the interconnected nanovoids connected to one another by hollow passages,

wherein the light source is optically coupled to the lightguide such that light emitted by the light source enters the lightguide and is transported within the lightguide by total internal reflection.

2. The illumination device of claim 1, wherein the interconnected nanovoids have an average size of less than about 0.7 micron.

3. The illumination device of claim 1, wherein the nanovoided polymeric layer has an effective index of refraction of from about 1.15 to about 1.45.

4. The illumination device of claim 1, the nanovoided polymeric layer comprising a binder and a plurality of nanoparticles, wherein a weight ratio of the binder to the plurality of nanoparticles is greater than about 1:

2, and a volume fraction of the interconnected nanovoids in the nanovoided polymeric layer is not less than about 20%.

5. The illumination device of claim 4, wherein the nanoparticles comprise reactive groups that are chemically bound to the binder.

6. The illumination device of claim 4, wherein the nanoparticles are not chemically bound to the binder.

7. The illumination device of claim 4, wherein the nanoparticles comprise elongated particles having an average aspect ratio that is not less than about 2.

8. The illumination device of claim 4, wherein the nanoparticles comprise spherical particles.

9. The illumination device of claim 1, the nanovoided polymeric layer further comprising beads having an average diameter of from about 0.01 to about 10 um.

10. The illumination device of claim 1, the nanovoided polymeric layer having an effective refractive index less than the refractive index of the viscoelastic layer.

11. The illumination device of claim 1, wherein an interface formed between the nanovoided polymeric layer and the viscoelastic layer comprises a plurality of features.

12. The illumination device of claim 1, wherein the optical article further comprises an additional layer disposed on the nanovoided polymeric layer opposite the viscoelastic layer.

13. The illumination device of claim 12, the additional layer comprising a multilayer optical film, a reflector, a mirror, a polarizer, a prismatic film, a three-quarter polarizer, a retroreflective film, polymer, metal, glass, ceramic, a graphic, paper, fabric or a combination thereof.

14. An illumination device comprising:

a light source; and

an optical article comprising;

a lightguide,

a first viscoelastic layer disposed on the lightguide,

a second viscoelastic layer disposed on the lightguide opposite the first viscoelastic layer, and

a first nanovoided polymeric layer disposed on the first viscoelastic layer opposite the lightguide, the first nanovoided polymeric layer comprising a first plurality of interconnected nanovoids, at least some of the interconnected nanovoids connected to one another by hollow passages,

wherein the light source is optically coupled to the lightguide such that light emitted by the light source enters the lightguide and is transported within the lightguide by total internal reflection.

15. The illumination device of claim 14, the optical article further comprising a second nanovoided polymeric layer disposed on the second viscoelastic layer opposite the lightguide.

16. An illumination device comprising:

a light source; and

an optical article comprising;

a lightguide optically coupled to the light source,

a viscoelastic layer disposed on the lightguide, and

a nanovoided polymeric layer disposed on the viscoelastic layer opposite the lightguide, the nanovoided polymeric layer comprising a plurality of interconnected nanovoids,

wherein the interface formed between the viscoelastic layer and the nanovoided layer comprises a plurality of elongated prisms.

17. The illumination device of claim 16, the optical article further comprising a light emitting layer disposed on the lightguide opposite the viscoelastic layer, wherein an outer surface of the light emitting layer comprises a plurality of elongated lenses.

18. The illumination device of claim 17, wherein the elongated prisms extend orthogonal to the elongated lenses.

19. The illumination device of claim 17, the optical article further comprising a second viscoelastic layer disposed between the lightguide and the light emitting layer.