Backlight unit and liquid crystal display device having the same

• US 7,488,104 B2
• Filed: 11/21/2006
• Issued: 02/10/2009
• Est. Priority Date: 05/21/2004
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Suzuki, Toshihiro, Ishiwa, Masaru, Hamada, Tetsuya
• Primary Examiner(s): Truong; Bao Q
• Application Number:
  US11/562,181
• Publication Number:
  US 20070153548A1
• Time in Patent Office: 812 Days
• Field of Search: 362600-634, 362/561, 349 56- 71
• US Class Current: 362/616
• CPC Class Codes: G02B 6/003 Lens or lenticular sheet or layer
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0085 Means for removing heat created by the light source from the package heat extraction or cooling elements for semiconductor light sources in general H01L33/64
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 1/133628 with cooling means

Abstract

A backlight unit has a light source, a reflection sheet, a light guide plate, an air space, and a diffuser, wherein the reflection sheet, the light guide plate, the air space, and the diffuser are overlaid in this order. The light source is configured to arrange individual light sources having different spectra or different light emission quantities near an incident plane of the light guide plate, and on a plane facing the reflection sheet of the light guide plate, scatter dots are disposed which take light propagating through the light guide plate out of the reflection sheet side. The backlight unit and a liquid crystal display device including the same have excellent display quality.

Claims

1. A backlight unit comprising:

a discrete light source section, a reflecting section, a light guide section, a first optical mixing section, and a second optical mixing section;

wherein

the reflecting section, the light guide section, the first optical mixing section, and the second optical mixing section are overlaid in this order;

the discrete light source section includes individual light sources having different spectra or different light emission quantities arranged near an incident plane of the light guide section;

a light drawing section configured to take a light propagating through the light guide section out on a reflecting section side or on a first optical mixing section side is provided on a surface of the light guide section facing the reflecting section or a surface facing the first optical mixing section;

the first optical mixing section is configured to mix color lights of different spectra or lights of different light quantities substantially in an in-plane direction to make the light uniform; and

the second optical mixing section is configured to mix lights at different angles in a same point in a plane to angularly realign the light to make a luminous light color and a luminous light quantity uniform in the plane.

2. The backlight unit according to claim 1, wherein the light guide section has the light drawing section on a side of a plane facing a light emission plane, the reflecting section is disposed on the light drawing section side of the light guide section, the discrete light source section has a plurality of LEDs and a reflector disposed around the LEDs, and the second optical mixing section is disposed at a predetermined space from the light emission plane of the light guide section.

3. The backlight unit according to claim 1, wherein the first optical mixing section is an air space having a predetermined thickness sandwiched between the light guide section and the second optical mixing section.

4. The backlight unit according to claim 3, wherein the predetermined thickness is about 2 mm to about 50 mm.

5. The backlight unit according to claim 1, wherein the light drawing section includes scatter dots disposed on the light guide section.

6. The backlight unit according to claim 1, wherein the light drawing section includes fine projections and recesses.

7. The backlight unit according to claim 1, wherein the light drawing section has a fine lens shape.

8. The backlight unit according to claim 1, wherein the light drawing section is disposed so that an arrangement density is low near the incident plane and the arrangement density is higher away from the incident plane.

9. The backlight unit according to claim 1, wherein the light drawing section is not disposed from the incident plane at a predetermined distance.

10. The backlight unit according to claim 9, wherein the predetermined distance is about 2 mm to about 50 mm.

11. The backlight unit according to claim 1, wherein the discrete light source section has a plurality of red LEDs, green LEDs, and blue LEDs.

12. The backlight unit according to claim 11, wherein the red LEDs, the green LEDs, and the blue LEDs are linearly arranged at almost equal spaces along a longitudinal direction of the incident plane.

13. The backlight unit according to claim 11, wherein the red LEDs, the green LEDs, and the blue LEDs are linearly mounted along a longitudinal direction of an LED circuit board, and arranged on one side of a short direction of the LED circuit board.

14. The backlight unit according to claim 13, wherein a surface of the LED circuit board on the light guide section side is a mirror reflection surface or a diffuse reflection surface.

15. The backlight unit according to claim 1, wherein a diffuser is used as the second optical mixing section.

16. The backlight unit according to claim 1, wherein a diffuser sheet is used as the second optical mixing section.

17. The backlight unit according to claim 1, wherein the side of the first optical mixing section is a mirror reflection surface or a diffuse reflection surface.

18. The backlight unit according to claim 1, wherein a color sensor is disposed on the side of the first optical mixing section.

19. The backlight unit according to claim 18, wherein the color sensor is disposed substantially at a center portion of the side on which the discrete light source is not disposed.

20. The backlight unit according to claim 1, wherein a color sensor is disposed on a side of the surface of the light guide section facing the reflecting section at a position at least about 10 mm away from the incident plane as a surface of the sensor faces the light guide section side.

21. The backlight unit according to claim 13, wherein a radiator plate or a radiation fin is provided on a back side of the LED circuit board.

22. The backlight unit according to claim 21, wherein a high heat radiation member is disposed on a surface of the radiator plate or the radiating fin.

23. The backlight unit according to claim 21, further comprising a housing configured to hold the light guide plate, wherein the housing includes a high heat radiation member.

24. The backlight unit according to claim 13, further comprising a housing configured to hold the light guide plate, wherein the LED circuit board has an L shape and contacts the housing.

25. The backlight unit according to claim 24, wherein the housing includes a high heat radiation member.

26. The backlight unit according to claim 1, wherein the light guide section has two light guide plates, and the two light guide plates are disposed so that opposing surfaces thereof facing the incident plane face each other.

27. The backlight unit according to claim 26, wherein the two light guide plates have a wedge shape in which a thickness on the incident plane side is thicker than a thickness on the opposing surface side.

28. The backlight unit according to claim 26, wherein a mirror reflection member or a diffused reflection member is provided between the opposing surfaces of the two light guide plates.

29. The backlight unit according to claim 1, wherein the light guide section has a light guide plate in a wedge shape in which a thickness on the incident plane side is thicker than a thickness on the opposing surface side facing the incident plane.

30. The backlight unit according to claim 29, wherein the light emission plane of the light guide plate is disposed at a predetermined space from the second optical mixing section.

31. The backlight unit according to claim 29, wherein the light guide plate is disposed so that the light emission plane is tilted toward the second optical mixing section, and a plane facing the light emission plane is disposed substantially in parallel.

32. The backlight unit according to claim 29, further comprising two plates on the light guide plates, wherein the two light guide plates are disposed so that a predetermined space is provided between opposing surfaces.

33. The backlight unit according to claim 29, wherein the reflecting section has a projecting shape so that a distance from the second optical mixing section is at a minimum near a center portion in the plane.

34. The backlight unit according to claim 1, wherein the light guide section has the light emission plane with a mountain shape in cross section which is tilted at a predetermined angle with respect to a surface of the light guide section facing the reflecting section.

35. The backlight unit according to claim 11, wherein the green LED, the red LED, and the blue LED are arranged adjacently in this order from one end portion of the incident plane to the other end portion along a longitudinal direction;

a plurality of LED groups are arranged adjacent to the blue LEDs, in which a plurality of the red LEDs, the green LEDs, and the blue LEDs are adjacently arranged in a predetermined order; and

the red LED and the green LED are adjacently arranged in this order adjacent to the LED group.

36. The backlight unit according to claim 35, wherein in the LED group, the green LED, the red LED, the green LED, and the blue LED are adjacently arranged in this order from the one end portion side to the other end portion side.

37. The backlight unit according to claim 35, wherein in the LED group, the red LED, the green LED, the red LED, and the blue LED are adjacently arranged in this order from the one end portion side to the other end portion side.

38. A liquid crystal display device comprising:

a backlight unit according to claim 1, the backlight unit further provided with a light guide plate and a light source portion; and

a liquid crystal display panel disposed on a light emission plane side of the light guide plate.

39. The liquid crystal display device according to claim 38, wherein a lens sheet or a polarizer sheet is disposed between the backlight unit and the liquid crystal display panel.

40. A liquid crystal display device comprising:

a side lit backlight unit provided with a light guide plate and a light source portion disposed near at least one side end surface of the light guide plate; and

a liquid crystal display panel disposed on a light emission plane side of the light guide plate;

wherein

a flexible substrate or a printed circuit board is disposed in a peripheral portion of the liquid crystal display panel and includes a driver circuit arranged to drive liquid crystals at every pixel of the liquid crystal display panel; and

the flexible substrate or the printed circuit board is disposed so as not to cover the light source portion.

41. The liquid crystal display device according to claim 40 wherein the flexible substrate or the printed circuit board is disposed near an upper portion of the light source portion when folded.

42. The liquid crystal display device according to claim 40, wherein the flexible substrate or the printed circuit board extends from an end surface side on which the light source portion of the light guide plate is not disposed, and is connected to a control circuit portion which drives the liquid crystal display panel.

43. The liquid crystal display device according to claim 42, wherein the light source portion has a plurality of LEDs arranged in a direction along a side of an incident plane of the light guide plate.

44. A liquid crystal display device comprising:

a backlight unit provided with a light guide plate, a light source portion, and a control portion;

a liquid crystal display panel disposed on a light emission plane side of the light guide plate and having a plurality of pixels arranged in a display area; and

a light quantity sensor disposed on a viewer side of the liquid crystal display panel;

wherein

in an area of the liquid crystal display panel outside of the display area, the liquid crystal display panel has an area from which a red light, a green light, and a blue light are emitted from a backlight unit side;

the light quantity sensor is arranged on the area of the liquid crystal display panel outside of the display area to detect a light quantity; and

the control portion controls the light source portion based on the light quantity.

45. A backlight unit comprising:

a discrete light source section, a first reflecting section, a light guide section, a first optical mixing section, and a second optical mixing section;

wherein

the first reflecting section, the light guide section, the first optical mixing section, and the second optical mixing section are overlaid in this order;

the discrete light source section includes individual light sources having different spectra or different light emission quantities arranged near an incident plane of the light guide section;

a light drawing section configured to take a light propagating through the light guide section out on a first reflecting section side or on a first optical mixing section side is provided on a surface of the light guide section facing the first reflecting section or a surface facing the first optical mixing section; and

a relationship, 0≦

Lp/H≦

2.5 is maintained, where a height of the first optical mixing section is H, and a length of a minimum unit of a cycle of an array of the discrete light source section is Lp.

46. The backlight unit according to claim 45, wherein the first optical mixing section is an air space sandwiched between the light guide section and the second optical mixing section.

47. The backlight unit according to claim 45, further comprising a second reflecting section which is disposed on the side of the first optical mixing section.

48. The backlight unit according to claim 45, wherein the second reflecting section is a scattering reflector.

49. The backlight unit according to claim 48, wherein the reflector is made of a plastic or resin.

50. The backlight unit according to claim 45, wherein the second optical mixing section is a transmissive diffuser.

51. The backlight unit according to claim 50, wherein the transmissive diffuser is a bulk diffuser having a transmittance of about 80% or below and a plate thickness of about 2 mm or greater.

52. The backlight unit according to claim 45, wherein the discrete light source section has a plurality of red LEDs, green LEDs, and blue LEDs.

53. The backlight unit according to claim 52, wherein the length Lp of the minimum unit of the cycle of the array of the discrete light source section is an arrangement pitch of an LED array unit group having at least one of the red LEDs, the green LEDs, and the blue LEDs.

54. The backlight unit according to claims 45, further comprising a third reflecting section which is disposed adjacently to the second optical mixing section and reflects light entering in a substantially perpendicular direction.

55. The backlight unit according to claim 54, wherein the third reflecting section is a prism sheet.

56. A liquid crystal display device comprising:

a liquid crystal display panel provided with a pair of substrates disposed facing each other, and liquid crystals sealed between the pair of the substrates; and

the backlight unit according to claim 45 disposed on a back side of the liquid crystal display panel.