Direct type backlight unit and liquid crystal display device having the same

1. A backlight unit, comprising:

a plurality of lamps, each of the lamps having a quadrangular shaped lamp tube and an external electrode connected to two short sides thereof, respectively; and

a bottom cover holding the plurality of lamps.

2. The backlight unit according to claim 1 , wherein each of the external electrodes has a width smaller than its longitudinal length.

3. The backlight unit according to claim 1 , further comprising:

a first lower support, a second lower support, a first upper support, and a second upper support, each having a plurality of grooves for receiving the short sides of the lamps.

4. The backlight unit according to claim 3 , wherein the external electrodes are completely covered by the supports.

5. The backlight unit according to claim 3 , wherein the grooves formed in the first supports and the second supports are coupled to secure the lamps, respectively.

6. The backlight unit according to claim 3 , wherein the first supports and the second supports have a conductive layer for supplying power to the lamps.

7. The backlight unit according to claim 1 , wherein the lamps are external electrode fluorescent lamps (EEFLs).

8. The backlight unit according to claim 1 , wherein a high-high voltage is applied to each of the external electrodes to drive the lamps.

9. The backlight unit according to claim 1 , further comprising:

a reflection sheet disposed under the lamps for reflecting light from the lamps to a front side of the backlight unit; and

at least one optical sheet disposed above the lamps for scattering and condensing light from the lamps and light reflected from the reflection sheet.

10. A liquid crystal display device, comprising:

a liquid crystal display panel including an upper substrate, a lower substrate attached to the upper substrate, and a liquid crystal layer between the upper and lower substrates;

a backlight unit disposed at a back side of the liquid crystal display panel, the backlight unit including a plurality of lamps, each of the lamps having a quadrangular shaped lamp tube and an external electrode connected to two short sides thereof, respectively; and

a bottom cover holding the plurality of lamps.

11. The liquid crystal display device according to claim 10 , wherein each of the external electrodes has a width smaller than its longitudinal length.

12. The liquid crystal display device according to claim 10 , further comprising:

a first lower support, a second lower support, a first upper support, and a second upper support, each having a plurality of grooves for receiving the short sides of the lamps.

13. The liquid crystal display device according to claim 12 , wherein the external electrodes are completely covered by the supports.

14. The liquid crystal display device according to claim 12 , wherein the grooves formed in the first supports and the second supports are coupled to secure the lamps respectively.

15. The liquid crystal display device according to claim 12 , wherein the first supports and the second supports have a conductive layer for supplying power to the lamps.

16. The liquid crystal display device according to claim 10 , wherein the lamps are external electrode fluorescent lamps (EEFLs).

17. The liquid crystal display device according to claim 10 , wherein a high-high voltage is applied to each of the external electrodes to drive the lamps.

18. The liquid crystal display device according to claim 10 , further comprising:

a reflection sheet disposed under the lamps for reflecting light from the lamps to a front side of the backlight unit; and

at least one optical sheet disposed above the lamps for scattering and condensing light from the lamps and light reflected from the reflection sheet.