Back-lit displays with high illumination uniformity

• US 7,789,538 B2
• Filed: 11/15/2006
• Issued: 09/07/2010
• Est. Priority Date: 11/15/2006
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Hanley, Kenneth J., Epstein, Kenneth A.
• Primary Examiner(s): TSO, LAURA K
• Application Number:
  US11/560,260
• Publication Number:
  US 20080112184A1
• Time in Patent Office: 1,392 Days
• Field of Search: 362/244, 362/245, 362/246, 362/326, 362/330, 362/333
• US Class Current: 362/333
• 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 display panel and one or more light sources disposed behind the display panel. A diffuser is disposed between the one or more light sources and the display panel, and a light diverting layer is disposed between the one or more light sources and the diffuser. The light diverting layer has a first light-diverting surface facing the one or more light sources and a second light diverting surface facing the display panel. The light diverting layer diverts light passing from the one or more light sources to the diffuser, thus improving the uniformity of the light in the display unit.

Claims

1. A directly illuminated display unit, comprising:

a display panel;

one or more light sources disposed behind the display panel, and capable of producing illumination light;

a diffuser disposed between the one or more light sources and the display panel; and

a light diverting layer disposed between the one or more light sources and the diffuser, the light diverting layer comprising a first light diverting surface facing the one or more light sources, the first light diverting surface diverting light normally incident on the light diverting layer primarily in a first diverting plane orthogonal to the light diverting layer, the light diverting layer further comprising a second light diverting surface facing the diffuser, the second light diverting surface being configured so as to divert light propagating within the light diverting layer in a direction perpendicular to the light diverting layer into a second diverting plane non-parallel to the first diverting plane.

2. A unit as recited in claim 1, wherein the first diverting plane is substantially perpendicular to the second diverting plane.

3. A unit as recited in claim 1, wherein the first light diverting surface comprises light diverting elements having at least two adjacent surface portions separated by a surface discontinuity.

4. A unit as recited in claim 1, wherein the diffuser is attached to the light diverting layer.

5. A unit as recited in claim 4, further comprising an adhesive layer on a side of the diffuser facing the light diverting layer, portions of the second light diverting surface penetrating into the adhesive layer.

6. A unit as recited in claim 4, wherein at least some portions of the second light diverting surface are parallel to the diffuser and are attached to the diffuser.

7. A unit as recited in claim 1, wherein at least one of the first and second light diverting surfaces comprises a light diverting member that is asymmetrical relative to an axis normal to the light diverting layer.

8. A unit as recited in claim 1, wherein at least one of the first and second light diverting surfaces comprises a light diverting member having a surface portion parallel to the light diverting layer.

9. A unit as recited in claim 1, wherein at least one of the first and second light diverting surfaces comprises at least one flat surface portion between two neighboring light diverting members.

10. A unit as recited in claim 1, wherein at least one of the first and second light diverting surfaces comprises an elongated light diverting member extending across the light diverting layer.

11. A unit as recited in claim 10, wherein the elongated light diverting member has a height that is constant substantially along the length of the elongated light diverting member.

12. A unit as recited in claim 11, wherein the elongated light diverting member has a height that varies along the length of the elongated light diverting member.

13. A unit as recited in claim 10, wherein the elongated light diverting member has a width that varies along the length of the elongated light diverting member.

14. A unit as recited in claim 1, wherein at least one of the first and second light diverting surfaces comprises two adjacent light diverting members whose heights are not the same.

15. A unit as recited in claim 1, further comprising one or more light management films disposed between the diffuser and the display panel.

16. A unit as recited in claim 15, wherein the one or more light management films comprise at least a first brightness enhancing film and a reflective polarizer film.

17. A unit as recited in claim 16, further comprising a second brightness enhancing film having a prismatic structure oriented substantially orthogonal to a prismatic structure of the first brightness enhancing film.

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

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

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

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 unit as recited in claim 1, wherein the diffuser is a diffusing surface.

23. A unit as recited in claim 1, wherein the diffuser is a diffusing layer.

24. A directly illuminated display unit, comprising:

a display panel;

one or more light sources disposed behind the display panel, the one or more light sources being capable of producing illumination light;

a diffuser disposed between the display panel and the one or more light sources; and

a light diverting layer disposed between the one or more light sources and the diffuser, the light diverting layer comprising a first light-diverting surface facing the one or more light sources, and a second light diverting surface facing the diffuser, at least a first portion of the light from the one or more light sources that propagates within the light diverting layer in a direction substantially perpendicular to the light diverting layer substantially being transmitted through a flat portion of the second light diverting surface and at least a second portion of the light from the one or more light sources that propagates within the light diverting layer in a direction substantially perpendicular to the light diverting layer being totally internally reflected at a sloped portion of the second light diverting surface.

25. A unit as recited in claim 24, wherein light incident on the first light diverting surface from the one or more light sources is substantially diverted in a first light diverting plane and light incident on the second light diverting surface from the first light diverting surface is substantially diverted in a second light diverting plane non-parallel to the first light diverting plane.

26. A unit as recited in claim 24, wherein the first light diverting plane is substantially perpendicular to the second light diverting plane.

27. A unit as recited in claim 24, wherein at least one of the first and second light diverting surfaces comprises light diverting elements having at least two adjacent surface portions separated by a surface discontinuity.

28. A unit as recited in claim 24, wherein the diffuser is attached to the light diverting layer.

29. A unit as recited in claim 28, further comprising an adhesive layer on a side of the diffuser facing the light diverting layer, portions of the second light diverting surface penetrating into the adhesive layer.

30. A unit as recited in claim 28, wherein at least some portions of the second light diverting surface are parallel to the diffuser and are attached to the diffuser.

31. A unit as recited in claim 24, wherein at least one of the first and second light diverting surfaces comprises a light diverting element that is asymmetrical relative to an axis normal to the light diverting layer.

32. A unit as recited in claim 24, wherein at least one of the first and second light diverting surfaces comprises a light diverting element having a surface portion parallel to the light diverting layer.

33. A unit as recited in claim 24, wherein at least one of the first and second light diverting surfaces comprises at least one flat surface portion between two neighboring light diverting elements.

34. A unit as recited in claim 24, wherein at least one of the first and second light diverting surfaces comprises an elongated member extending across the light diverting layer.

35. A unit as recited in claim 34, wherein the elongated member has a height that is constant substantially along the length of the elongated member.

36. A unit as recited in claim 34, wherein the elongated member has a height that varies along the length of the elongated member.

37. A unit as recited in claim 34, wherein the elongated light diverting member has a width that varies along the length of the elongated member.

38. A unit as recited in claim 24, wherein at least one of the first and second light diverting surfaces comprises two adjacent light diverting elements whose heights are not the same.

39. A unit as recited in claim 24, further comprising one or more light management films disposed between the diffuser and the display panel.

40. A unit as recited in claim 39, wherein the one or more light management films comprise at least a first brightness enhancing film and a reflective polarizer film.

41. A unit as recited in claim 40, further comprising a second brightness enhancing film having a prismatic structure oriented substantially orthogonal to a prismatic structure of the first brightness enhancing film.

42. A unit as recited in claim 24, wherein the display panel comprises a liquid crystal display (LCD) panel.

43. A unit as recited in claim 24, wherein the one or more light sources comprise at least one light emitting diode.

44. A unit as recited in claim 24, wherein the one or more light sources comprise at least one fluorescent lamp.

45. A unit as recited in claim 24, further comprising a control unit coupled to the display panel to control an image displayed by the unit.