Blacklight unit, liquid crystal display device having the same, and method for providing substantially white light for liquid crystal display device

• US 20070147081A1
• Filed: 06/28/2006
• Published: 06/28/2007
• Est. Priority Date: 12/26/2005
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Philips LCD Company Limited (LG Display Co., Ltd.)
• Inventors: Choi, Jong-Hyun
• Granted Patent: US 8,203,665 B2
• Time in Patent Office: Days
• US Class Current: 362/612
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133609 including means for improving the color mixing, e.g. white

Abstract

A backlight unit as embodied includes a plurality of unit groups, each unit group having a plurality of light emitting diodes (LEDs); and a light mixing layer formed over the unit groups, for mixing lights emitted from the LEDs to provide substantially white light.

Claims

1. A backlight unit, comprising:

an optical source including a plurality of unit groups, each unit group having a plurality of light emitting diodes (LEDs); and

a light mixing layer formed over the unit groups, for mixing lights emitted from the LEDs to provide substantially white light.

2. The backlight unit of claim 1, wherein each of the unit groups comprises one red (R) LED, one blue (B) LED, and two green (G) LEDs.

3. The backlight unit of claim 2, wherein the R, B and G LEDs of each of the unit groups are arranged in a matrix form.

4. The backlight unit of claim 3, wherein each of the unit groups further comprises a white LED at a center thereof surrounded by the R, B and G LEDs.

5. The backlight unit of claim 1, wherein the light mixing layer includes a plurality of light mixing layers , each of the light mixing layers covering the LEDs in the corresponding unit group, the LEDs being arranged in a matrix form.

6. The backlight unit of claim 5, further comprising a reflector, the LEDs being enclosed by the reflector and the corresponding light mixing layer.

7. The backlight unit of claim 6, wherein each of the light mixing layers has a substantially semi-spherical shape and is in contact with the reflector.

8. The backlight unit of claim 6, further comprising a heat emitting plate below the reflector, a heat generated by the LEDs being absorbed by the reflector and being transmitted from the reflector to the heat emitting plate.

9. The backlight unit of claim 8, further comprising a printed circuit board for driving the LEDs, the printed circuit board being between the reflector and the heat emitting plate, the heat generated by the LEDs being transmitted from the reflector to the heat emitting plate via the printed circuit board.

10. The backlight unit of claim 1, wherein the light mixing layer is a single-layer structure.

11. The backlight unit of claim 10, wherein the light mixing layer is formed of a dispersion material.

12. The backlight unit of claim 11, wherein the light mixing layer is formed of one of poly methyl methcrylate (PMMA), SK4, silica, and MgF.

13. The backlight unit of claim 1, wherein the light mixing layer is a double-layer structure including an inner layer and an outer layer.

14. The backlight unit of claim 13, wherein a refractive index of the inner layer is larger than a refractive index of the outer layer.

15. The backlight unit of claim 14, wherein the inner layer is formed of one of poly methyl methcrylate (PMMA), SK4, silica, epoxy, and MgF, and the outer layer is formed of one of poly methyl methcrylate (PMMA), SK4, silica, epoxy, and MgF.

16. The backlight unit of claim 1, further comprising an optical sheet over the light mixing layer, wherein the optical sheet comprises:

a diffusion plate for diffusing the substantially white light incident from the optical source;

a prism sheet above the diffusion plate for increasing frontal brightness of the substantially white light passing through the diffusion plate; and

a protection sheet attached onto the prism sheet.

17. A liquid crystal display (LCD) device, comprising:

an LCD panel;

an optical source having a plurality of unit groups for emitting lights toward the LCD panel, each unit group having a plurality of light emitting diodes (LEDs); and

a light mixing layer formed over the unit groups, for mixing the lights emitted from the LEDs to provide substantially white light to the LCD panel.

18. The LCD device of claim 17, wherein each of the unit groups comprises one red (R) LED, one blue (B) LED, and two green (G) LEDs.

19. The LCD device of claim 18, wherein the R, B and G LEDs of each of the unit groups are arranged in a matrix form.

20. The LCD device of claim 19, wherein each of the unit groups further comprises a white LED at a center thereof surrounded by the R, B and G LEDs.

21. The LCD device of claim 17, wherein the light mixing layer includes a plurality of light mixing layers , each of the light mixing layers covering the LEDs in the corresponding unit group, the LEDs being arranged in a matrix form.

22. The LCD device of claim 21, further comprising a reflector, the LEDs being enclosed by the reflector and the corresponding light mixing layer.

23. The LCD device of claim 22, wherein each of the light mixing layers has a substantially semi-spherical shape and is in contact with the reflector.

24. The LCD device of claim 22, further comprising a heat emitting plate below the reflector, a heat generated by the LEDs being absorbed by the reflector and being transmitted from the reflector to the heat emitting plate.

25. The LCD device of claim 24, further comprising a printed circuit board for driving the LEDs, the printed circuit board being between the reflector and the heat emitting plate, the heat generated by the LEDs being transmitted from the reflector to the heat emitting plate via the printed circuit board.

26. The LCD device of claim 17, wherein the light mixing layer is a single-layer structure formed of one of poly methyl methcrylate (PMMA), SK4, silica, and MgF.

27. The LCD device of claim 17, wherein the light mixing layer is a double-layer structure including an inner layer and an outer layer and a refractive index of the inner layer is larger than a refractive index of the outer layer.

28. The LCD device of claim 27, wherein the inner layer is formed of one of poly methyl methcrylate (PMMA), SK4, silica, epoxy, and MgF, and the outer layer is formed of one of poly methyl methcrylate (PMMA), SK4, silica, epoxy, and MgF.

29. The LCD device of claim 17, further comprising an optical sheet located between the LCD panel and the light mixing layer, wherein the optical sheet comprises:

a diffusion plate for diffusing the substantially white light incident from the optical source;

a prism sheet above the diffusion plate for increasing frontal brightness of the white light passing through the diffusion plate; and

a protection sheet attached onto the prism sheet.

30. A method for providing substantially white light for a liquid crystal display device, the method comprising:

providing a plurality of unit groups, each unit group having a plurality of light emitting diodes (LEDs);

emitting lights from the LEDs toward a LCD panel; and

mixing the lights emitted from the LEDs by a light mixing layer to provide substantially white light to the LCD panel.

31. The method of claim 30, wherein the step of providing the plurality of unit groups includes providing one red (R) LED, one blue (B) LED, and two green (G) LEDs in each of the unit groups and arranging the R, B, G LEDs in a matrix form.

32. The method of claim 31, further comprising providing a white LED at a center of the unit group to be surrounded by the R, B and G LEDs.

33. The method of claim 30, wherein the light mixing layer includes a plurality of light mixing layers, and the step of mixing the lights includes

covering the LEDs arranged in a matrix form in the corresponding unit group by the corresponding light mixing layer;

and

mixing the lights emitted from the LEDs in the corresponding unit group by the corresponding light mixing layer.

34. The method of claim 33, further comprising:

absorbing a heat generating by the LEDs by a reflector that is in contact with the light mixing layers; and

dissipating the heat absorbed by the reflector from the reflector to a heat emitting plate below the reflector.

35. The method of claim 30, further comprising forming the light mixing layer to be a single-layer structure by one of poly methyl methcrylate (PMMA), SK4, silica, and MgF.

36. The method of claim 30, further comprising forming the light mixing layer to be a double-layer structure including an inner layer and an outer layer, and a refractive index of the inner layer being larger than a refractive index of the outer layer.

37. The method of claim 36, wherein the inner layer is formed of one of poly methyl methcrylate (PMMA), SK4, silica, epoxy, and MgF, and the outer layer is formed of one of poly methyl methcrylate (PMMA), SK4, silica, epoxy, and MgF.