Backlight unit and display device having the same using two different lights

1. A backlight unit comprising:

a case having an opening passing through the case;

at least one lamp assembly on a side surface of the case, the at least one lamp assembly comprising a light source;

an optical transreflective unit on the case, the optical transreflective unit transmitting a portion of first light incident upon the optical transreflective unit from the exterior through the opening and reflecting a portion of second light generated from the light source; and

an optical sheet comprising a first diffusion unit on the optical transreflective unit.

2. The backlight unit according to claim 1 , further comprising a light guide plate between the optical sheet and the optical transreflective unit,

the light guide plate transmitting the first light in a propagation direction, and transmitting the second light by changing a propagation direction of the second light from a side direction to the propagation direction of the first light.

3. The backlight unit according to claim 1 , further comprising a protective film on a rear surface of the optical transreflective unit, the protective film protecting the optical transflective unit from external foreign substances and supporting the optical transreflective unit.

4. The backlight unit according to claim 1 , further comprising a second diffusion unit on a rear surface of the optical transreflective unit,

the second diffusion unit supporting the optical transreflective unit, diffusing the first light, and reflecting and diffusing another portion of the second light transmitted by the optical transreflective unit.

5. The backlight unit according to claim 4 , wherein the each of the first and second diffusion units has a thickness ranging from 1 mm to 3 mm.

6. The backlight unit according to claim 1 , wherein the optical transreflective unit comprises at least one of an optical efficiency enhancement film, a diffusion sheet and a prism sheet.

7. The backlight unit according to claim 1 , the first diffusion unit comprises a plurality of rugged patterns on a rear surface thereof to improve brightness uniformity.

8. The backlight unit according to claim 7 , wherein the rugged patterns are equal in size, and are respectively separated by gaps that progressively differ from a central region of the first diffusion unit to an edge region.

9. The backlight unit according to claim 7 , wherein the rugged patterns are respectively separated by an equal gap, and progressively differ in size from a central region of the first diffusion unit to an edge region.

10. The backlight unit according to claim 1 , wherein the first diffusion unit directly contacts the optical transreflective unit.

11. The backlight unit according to claim 1 , wherein the first diffusion unit is separated from the optical transreflective unit.

12. A display device comprising:

a display panel; and

a backlight unit providing light to the display panel,

the backlight unit comprising:

a first case having an opening passing through the case;

at least one lamp assembly on a side surface of the first case, the at least one lamp assembly comprising a light source;

an optical transreflective unit on the first case, the optical transreflective unit transmitting a portion of first light incident upon the optical transreflective unit from the exterior through the opening and reflecting a portion of second light generated from the light source; and

an optical sheet comprising a first diffusion unit on the optical transreflective unit.

13. The display device according to claim 12 , further comprising:

a second case coupled to the first case to surround the display panel; and

a support member attached to the first case.