Backlight unit and display apparatus having the same

1. A backlight unit comprising:

a light guide plate including an exit surface which has a polygonal shape, a lower surface which faces the exit surface, and side surfaces which connect the exit surface and the lower surface, wherein the light guide plate guides a light such that the light exits from the exit surface; and

a light source unit including a plurality of light sources which provide the light to the light guide plate,

wherein

the light guide plate further includes a protrusion which protrudes from an end of the lower surface in a direction opposite to the exit surface, and

the protrusion comprises a first inclination surface which extends directly from a side surface of the light guide plate nearest the light source unit, and a second inclination surface which connects the first inclination surface and the lower surface to each other.

2. The backlight unit of claim 1 , wherein the protrusion is between two side surfaces parallel to each other among the side surfaces, and longitudinally extends in a direction substantially perpendicular to the two parallel side surfaces.

3. The backlight unit of claim 1 , wherein the light source unit is on the first inclination surface.

4. The backlight unit of claim 3 , wherein an angle between the first inclination surface and a surface substantially perpendicular to the lower surface of the light guide plate is equal to or greater than a critical angle of the light guide plate.

5. The backlight unit of claim 4 , wherein

the angle between the first inclination surface and the surface substantially perpendicular to the lower surface of the light guide plate satisfies an equation

θ

≥

sin

-

1

⁡

(

1

n

)

,

where θ denotes the angle between the first inclination surface and the surface substantially perpendicular to the lower surface of the light guide plate and n denotes a refractive index of the light guide plate.

6. The backlight unit of claim 4 , wherein an angle between the second inclination surface and the surface substantially perpendicular to the lower surface of the light guide plate is equal to or greater than the angle between the first inclination surface and the surface substantially perpendicular to the lower surface of the light guide plate.

7. The backlight unit of claim 1 , wherein

a distance (d) between a point at which the first inclination surface meets one of the side surfaces and a point at which the second inclination surface meets the lower surface satisfies an equation

d

≥

h

⁢

⁢

1

tan

⁢

⁢

θ

1

+

h

⁢

⁢

2

tan

⁢

⁢

θ

2

,

where θ 1 denotes an angle between the first inclination surface and a surface substantially perpendicular to the lower surface, θ 2 denotes an angle between the second inclination surface and the surface substantially perpendicular to the lower surface, h1 denotes a shortest distance between the exit surface and a point at which the first inclination surface meets the second inclination surface, and h2 denotes a shortest distance between the exit surface and the lower surface.

8. The backlight unit of claim 1 , further comprising a reflective member which overlaps a portion of the exit surface, which overlaps the protrusion.

9. The backlight unit of claim 8 , wherein the reflective member further overlaps one of the side surfaces, which meets the first inclination surface.

10. A display apparatus comprising:

a light guide plate including an exit surface which has a polygonal shape, a lower surface which faces the exit surface, and side surfaces which connect the exit surface and the lower surface, wherein the light guide plate guides a light such that the light exits from the exit surface;

a light source unit including a plurality of light sources which provide the light to the light guide plate; and

a display panel which receives the light which exits from the light guide plate, and displays an image,

wherein

the light guide plate further includes a protrusion which protrudes from an end of the lower surface in a direction opposite to the exit surface, and

the protrusion comprises a first inclination surface which extends directly from a side surface of the light guide plate nearest the light source unit, and a second inclination surface which connects the first inclination surface and the lower surface to each other.

11. The display apparatus of claim 10 , wherein the protrusion is between two side surfaces parallel to each other among the side surfaces, and longitudinally extends in a direction substantially perpendicular to the two parallel side surfaces.

12. The display apparatus of claim 10 , wherein the light source unit is on the first inclination surface.

13. The display apparatus of claim 12 , wherein an angle between the first inclination surface and a surface substantially perpendicular to the lower surface of the light guide plate is equal to or greater than a critical angle of the light guide plate.

14. The display apparatus of claim 13 , wherein

the angle between the first inclination surface and the surface substantially perpendicular to the lower surface of the light guide plate satisfies an equation

θ

≥

sin

-

1

⁡

(

1

n

)

,

where θ denotes the angle between the first inclination surface and the surface substantially perpendicular to the lower surface of the light guide plate and n denotes a refractive index of the light guide plate.

15. The display apparatus of claim 13 , wherein an angle between the second inclination surface and the surface substantially perpendicular to the lower surface of the light guide plate is equal to or greater than the angle between the first inclination surface and the surface substantially perpendicular to the lower surface of the light guide plate.

16. The display apparatus of claim 10 , wherein

a distance (d) between a point at which the first inclination surface meets one of the side surfaces and a point at which the second inclination surface meets the lower surface satisfies an equation

d

≥

h

⁢

⁢

1

tan

⁢

⁢

θ

1

+

h

⁢

⁢

2

tan

⁢

⁢

θ

2

,

where θ 1 denotes an angle between the first inclination surface and a surface substantially perpendicular to the lower surface, θ 2 denotes an angle between the second inclination surface and the surface substantially perpendicular to the lower surface, h1 denotes a shortest distance between the exit surface and a point at which the first inclination surface meets the second inclination surface, and h2 denotes a shortest distance between the exit surface and the lower surface.

17. The display apparatus of claim 10 , further comprising a reflective member which overlaps a portion of the exit surface, which overlaps to the protrusion.

18. The display apparatus of claim 17 , wherein the reflective member further overlaps one of the side surfaces, which meets the first inclination surface.

19. A method of forming a backlight unit, the method comprising:

forming a base of a light guide plate, the base including an exit surface which has a polygonal shape, a lower surface which faces the exit surface, and side surfaces which connect the exit surface and the lower surface to each other;

forming a protrusion of the light guide plate, wherein the protrusion protrudes from the lower surface of the base in a direction away from the exit surface and comprises:

a first inclined surface which extends directly from one of the side surfaces, and

a second inclined surface which connects the first inclined surface and the lower surface to each other; and

disposing a light source unit including a plurality of light sources which provide the light to the light guide plate, facing the first inclined surface of the protrusion,

wherein the first inclined surface extends directly from a side surface of the light guide plate nearest the light source unit.