Back-lit displays with high illumination uniformity

• US 20070030415A1
• Filed: 05/16/2005
• Published: 02/08/2007
• Est. Priority Date: 05/16/2005
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Epstein, Kenneth
• Application Number:
  US11/129,942
• Publication Number:
  US 20070030415A1
• Time in Patent Office: Days
• US Class Current: 349/64
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/133611 including means for improving the brightness uniformity

Abstract

A directly illuminated display unit has a light source unit that includes one or more light sources capable of producing illumination light for illuminating a display panel. A diffuser layer is disposed between the light source unit and the display panel. At least one of a first brightness enhancing layer and a reflective polarizer is disposed between the diffuser layer and the display panel. A light-diverting surface is disposed between the diffuser layer and the light source unit. The light-diverting surface diverts a propagation direction of at least some of the illumination light passing from the light source unit to the diffuser layer.

Claims

1. A directly illuminated display unit, comprising:

a light source unit comprising one or more light sources capable of producing illumination light;

a display panel;

a diffuser layer disposed between the light source unit and the display panel;

at least one of a first brightness enhancing layer and a reflective polarizer layer disposed between the diffuser layer and the display panel; and

a light-diverting surface disposed between the diffuser layer and the light source unit, the light-diverting surface diverting a propagation direction of at least some of the illumination light passing from the light source unit to the diffuser layer as the illumination light passes through the surface.

2. A unit as recited in claim 1, wherein the display panel comprises a liquid crystal display (LCD) panel.

3. A unit as recited in claim 1, wherein a single pass transmission through the diffuser layer is greater than about 70%.

4. A unit as recited in claim 1, wherein a single pass transmission through the diffuser layer is greater than about 74%.

5. A unit as recited in claim 1, wherein the one or more light sources comprise at least one light emitting diode.

6. A unit as recited in claim 1, wherein the one or more light sources comprise at least one fluorescent lamp.

7. A unit as recited in claim 1, wherein the diffuser layer has a lower surface facing the light source unit, the lower surface comprising the light-diverting surface.

8. A unit as recited in claim 1, further comprising an intermediate layer disposed between the diffuser layer and the light source unit, the intermediate layer comprising the light-diverting surface.

9. A unit as recited in claim 8, wherein the diffuser layer is attached to the intermediate layer.

10. A unit as recited in claim 8, wherein the light-diverting surface faces the diffuser layer.

11. A unit as recited in claim 10, further comprising an adhesive layer on a side of the diffuser layer facing the intermediate layer, portions of the light-diverting surface penetrating into the adhesive layer.

12. A unit as recited in claim 10, wherein at least some portions of the light-diverting surface are parallel to the diffuser layer and other portions of the light-diverting surface are non-parallel to the diffuser layer.

13. A unit as recited in claim 12, wherein at least some of the portions of the light-diverting surface parallel to the diffuser layer are attached to the diffuser layer.

14. A unit as recited in claim 8, wherein the light-diverting surface faces the light source unit.

15. A unit as recited in claim 1, wherein the light-diverting surface comprises a repeating structural pattern.

16. A unit as recited in claim 1, wherein the light-diverting surface comprises one or more structure portions, the one or more structure portions being regions of the light-diverting surface that are non-parallel to the diffuser layer.

17. A unit as recited in claim 16, wherein the light-diverting surface further comprises one or more flat portions parallel to the diffuser layer.

18. A unit as recited in claim 1, further comprising a second brightness enhancing layer having a prismatic structure oriented substantially orthogonal to prismatic structure of the first brightness enhancing layer.

19. A unit as recited in claim 1, further comprising a reflecting polarizer disposed between the first brightness enhancing layer and the display panel.

20. A unit as recited in claim 19, wherein the reflecting polarizer comprises a multilayer optical film.

21. A unit as recited in claim 1, further comprising a control unit coupled to the display panel to control an image displayed by the unit.

22. A method of operating a display panel, comprising:

generating illumination light;

directing the illumination light generally towards the display panel;

diverting at least some of the illumination light at a first structured surface as the illumination light passes through the structured surface;

diffusing the deviated illumination light; and

passing the diffused illumination light to the display panel.

23. A method as recited in claim 22, further comprising modulating portions of the diffused illumination light to form an image displayed by the display panel.

24. A method as recited in claim 23, further comprising controlling different modulation pixels of the display panel to modulate the illumination light.

25. A method as recited in claim 22, wherein diverting at least some of the illumination light comprises refractively diverting at least some of the illumination light at the first structured surface.

26. A method as recited in claim 22, further comprising enhancing brightness of the diffused illumination light by passing the diffused illumination light through at least one brightness enhancing film.

27. A method as recited in claim 22, further comprising reflecting diffused illumination light in a first polarization state back towards the first structured surface.

28. A method as recited in claim 27, further comprising changing the polarization state of the illumination light reflected in the first polarization state.