BACK-LIT TRANSMISSIVE DISPLAY HAVING VARIABLE INDEX LIGHT EXTRACTION LAYER

• US 20140071653A1
• Filed: 05/09/2012
• Published: 03/13/2014
• Est. Priority Date: 05/13/2011
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Thompson, David Scott, Schaffer, Kevin R., Yang, Zhaohui, Hao, Encai, Sherman, Audrey A., Meis, Michael A., Wheatley, John A., Stay, Matthew S., Kamrath, Robert F., Pekurovsky, Mikhail L., Solomonson, Steven D.
• Granted Patent: US 9,541,701 B2
• Time in Patent Office: Days
• US Class Current: 362/19
• CPC Class Codes: G02B 6/0043 provided on the surface 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 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• CPC Class Codes: G02B 6/0058 varying in density, size, shape or depth along the light guide
• CPC Class Codes: G02B 6/0066 characterised by the light source being coupled to the light guide

Abstract

This application describes a back-lit transmissive display including a transmissive display (620) and a variable index light extraction layer (640) optically coupled to a lightguide (630). The variable index light extraction layer has first regions (140) of nanovoided polymeric material and second regions (130) of the nanovoided polymeric material and an additional material. The first and second regions are disposed such that for light being transported at a supercritical angle in the lightguide, the variable index light extraction layer selectively extracts the light in a predetermined way based on the geometric arrangement of the first and second regions. The transmissive display may be a transmissive display panel or a polymeric film such as a graphic.

Claims

1. A back-lit transmissive display assembly, comprising:

a transmissive display; and

an illumination article comprising a lightguide and a variable index light extraction layer, the variable index light extraction layer optically coupled to the lightguide and the transmissive display, the variable index light extraction layer having first and second regions, the first region comprising nanovoided polymeric material, the second region comprising the nanovoided polymeric material and an additional material, the first and second regions being disposed such that for light emitted by a light source and injected into the lightguide, the variable index light extraction layer selectively extracts the light in a predetermined way based on the geometric arrangement of the first and second regions.

2. The back-lit transmissive display assembly of claim 1, wherein the first region has a first refractive index, the second region has a second refractive index, and the difference between the first and second refractive indices is about 0.03 to about 0.5.

3. The back-lit transmissive display assembly of claim 1, wherein the first region has a first refractive index less than about 1.4.

4. The back-lit transmissive display assembly of claim 1, wherein the first region has a void volume of about 20 to about 60%.

5. The back-lit transmissive display assembly of claim 1, wherein the first region has a haze less than about 5% and a clarity greater than about 90%.

6. The back-lit transmissive display assembly of claim 1, wherein the second region has a void volume of less than about 20%.

7. The back-lit transmissive display assembly of claim 1, wherein the variable index light extraction layer has a light transmittance of greater than about 90%.

8. The back-lit transmissive display assembly of claim 1, wherein the variable index light extraction layer has a haze less than about 10% and a clarity greater than about 90%.

9. The back-lit transmissive display assembly of claim 1, wherein the second region comprises a plurality of second regions arranged in a pattern across a transverse plane of the layer.

10. The back-lit transmissive display assembly of claim 1, wherein the assembly comprises an aspect ratio of less than about 1/3, the aspect ratio comprising a thickness of the variable index light extraction layer divided by a smallest width of the second regions.

11. The back-lit transmissive display assembly of claim 1,

the first region having a first refractive index, and

the assembly further comprising a light output layer disposed on the variable index light extraction layer, the light output layer having a third refractive index greater than that of the first.

12. The back-lit transmissive display assembly of claim 1,

the first region having a first refractive index, and

the assembly further comprising

a light output layer disposed on the variable index light extraction layer, the light output layer having a third refractive index greater than that of the first, and

a turning film disposed between the variable index light extraction layer and the transmissive display, the turning film comprising a structured surface facing the variable index light extraction layer.

13. The back-lit transmissive display assembly of claim 1, further comprising a back reflector proximate a major surface of the lightguide for reflecting light emitted by the lightguide.

14. The back-lit transmissive display assembly of claim 13, wherein the back reflector is a semi-specular reflector.

15. The back-lit transmissive display assembly of claim 1, further comprising a brightness enhancement film disposed between the transmissive display and the variable index light extraction layer.

16. The back-lit transmissive display assembly of claim 1, further comprising a reflective polarizer disposed on the lightguide.

17. The back-lit transmissive display assembly of claim 16, wherein the reflective polarizer has a first average reflectance for visible light polarized in a first plane, and a second average reflectance for visible light polarized in a second plane orthogonal to the first plane, the first average reflectance being greater than the second average reflectance.

18. The back-lit transmissive display assembly of claim 16, wherein the first average reflectance is at least about 90%, and the second average reflectance is in a range from about 25% to about 90%.

19. A back-lit transmissive display device comprising a light source and the back-lit transmissive display assembly of claim 1, wherein the light source is optically coupled to the lightguide.

20. The back-lit transmissive display assembly of claim 1, wherein the transmissive display comprises a display panel selected from the group consisting of a liquid crystal display panel, an electrowetting display panel, and an electrophoretic display panel.

21. The back-lit transmissive display assembly of claim 20, wherein the display panel comprises a polymer dispersed liquid crystal display panel.

22. The back-lit transmissive display assembly of claim 20, wherein the display panel comprises a structured electrode.

23. The back-lit transmissive display assembly of claim 20, wherein the display panel comprises a plurality of independently controlled areas.