Backlight unit including light emitting diodes and liquid crystal display device including the same

• US 20090284682A1
• Filed: 12/15/2008
• Published: 11/19/2009
• Est. Priority Date: 05/13/2008
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Jang, Kyeong-Kun, Yoo, Kee-Tae, Kim, Pu-Jin, Lee, Koo-Hwa
• Granted Patent: US 8,339,541 B2
• Time in Patent Office: Days
• US Class Current: 349/62
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• 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 for a liquid crystal display device includes a plurality of white LEDs on a PCB, along a length direction of the PCB, and emitting white lights, the plurality of white LEDs including first and second LEDs alternately arranged; and a plurality of optical sheets on a path of the white lights from the plurality of white LEDs to a liquid crystal panel, wherein the white light from the first LED and the white light from the second LED are substantially complementary in color to each other with respect to a target white light.

Claims

1. A backlight unit for a liquid crystal display device, comprising:

a plurality of white LEDs arranged in a line that emit white light, the plurality of white LEDs including first and second LEDs alternately arranged; and

a plurality of optical sheets in a path from the plurality of white LEDs to a liquid crystal panel,

wherein when the white light from the first LED and the white light from the second LED are combined, the combined white light has a color substantially the same as a target white light.

2. The backlight unit according to claim 1, wherein the plurality of white LEDs further includes a third LED emitting the target white light.

3. The backlight unit according to claim 1, wherein the plurality of white LEDs are mounted on a printed circuit board (PCB).

4. The backlight unit according to claim 1, wherein the white light from the plurality of LEDs have a CIE color x coordinate in a range of about 0.005 to 0.030 and a CIE color y coordinate in a range of about 0.007 to about 0.050.

5. The backlight unit according to claim 4, wherein each of a CIE color x coordinate difference and a CIE color y coordinate difference between the white light from the first LED and the white light from the second LED is in a range of about 0 to about 0.02.

6. The backlight unit according to claim 1, wherein each of the plurality of white LEDs includes a blue LED chip and one of a yellow phosphor and a green and red mixed phosphor.

7. The backlight unit according to claim 1, further comprising a light guide plate facing the plurality of optical sheets, the plurality of white LEDs facing a side of the light guide plate.

8. The backlight unit according to claim 1, wherein the plurality of white LEDs are below the plurality of optical sheets.

9. A liquid crystal display device, comprising:

a liquid crystal panel;

a plurality of white LEDs arranged in a line that emits white light, the plurality of white LEDs including first and second LEDs alternately arranged; and

a plurality of optical sheets in a path from the plurality of white LEDs to the liquid crystal panel,

wherein when the white light from the first LED and the white light from the second LED are combined, the combined white light has a color substantially the same as a target white light.

10. The device according to claim 9, wherein the plurality of white LEDs further includes a third LED emitting the target white light.

11. The device according to claim 10, wherein the plurality of white LEDs are mounted on a printed circuit board (PCB).

12. The device according to claim 9, wherein the white lights from the plurality of LEDs have a CIE color x coordinate in a range of about 0.005 to 0.030 and a CIE color y coordinate in a range of about 0.007 to about 0.050.

13. The device according to claim 12, wherein each of a CIE color x coordinate difference and a CIE color y coordinate difference between the white light from the first LED and the white light from the second LED is in a range of about 0 to about 0.02.

14. The device according to claim 9, wherein each of the plurality of white LEDs includes a blue LED chip and one of a yellow phosphor and a green-red mixed phosphor.

15. The device according to claim 9, further comprising a light guide plate facing the plurality of optical sheets, the plurality of white LEDs facing a side of the light guide plate.

16. The device according to claim 9, wherein the plurality of white LEDs are below the plurality of optical sheets.

17. A liquid crystal display device, comprising:

a liquid crystal panel;

a plurality of LEDs arranged in a line that emit light, the plurality of LEDs including first and second LEDs alternately arranged to mix the lights from the first and second LEDs; and

a plurality of optical sheets in a path from the plurality of LEDs to the liquid crystal panel,

wherein when the white light from the first LED and the white light from the second LED are combined, the combined white light has a color substantially the same as a target white light.

18. The device according to claim 17, wherein the light is one of red, green, blue and white, and wherein the optical property is at least one of a color and a luminance.

19. A method of manufacturing a backlight for a liquid crystal display comprising:

selecting first LEDs from a first color bin;

selecting second LEDs from a second color bin that is complementary to the first color bin; and

placing first and second LEDs in alternating positions in the backlight.

20. The method of claim 19 further including placing LEDs in color bins according to the color produced by the LED.

21. The method of claim 19 further including determining the size and location of the color bins.