A display device comprising: a display panel configured to display images; a backlight unit configured to supply light to the display panel, and including a plurality of light generating blocks (800, 810 820, 830), each of the light generating blocks (800, 810, 820, 830) including: a first layer, a plurality of light source devices (220, 225) disposed on the first layer and configured to emit light, each light source device (220, 225) including a light emitting diode for generating the light, a reflection layer disposed on the first layer and configured to reflect the light emitted from the light source devices (220, 225), a second layer covering the light source devices (220, 225) and the reflection layer and configured to propagate the light reflected by the reflection layer, and a controller configured to selectively operate the light generating blocks (800, 810, 820, 830) of the backlight unit, wherein the second layer includes a plurality of first concave portions respectively disposed between two adjacent light source devices (220, 225) of each light generating block (800, 810, 820, 830) and a second concave portion having a shape different from the plurality of first concave portions and disposed between two adjacent light generating blocks (800, 810, 820, 830), and characterized in that the second concave portion is filled with an adhesive material having a refractive index being lower than that of the second layer and in that each of the light generating blocks (800, 810, 820, 830) further includes at least one third layer (235, 251, 252) disposed on the second layer configured to diffuse the light propagated by the second layer. a display panel configured to display images; a backlight unit configured to supply light to the display panel, and including a plurality of light generating blocks (800, 810 820, 830), each of the light generating blocks (800, 810, 820, 830) including: a first layer, a plurality of light source devices (220, 225) disposed on the first layer and configured to emit light, each light source device (220, 225) including a light emitting diode for generating the light, a reflection layer disposed on the first layer and configured to reflect the light emitted from the light source devices (220, 225), a second layer covering the light source devices (220, 225) and the reflection layer and configured to propagate the light reflected by the reflection layer, and a controller configured to selectively operate the light generating blocks (800, 810, 820, 830) of the backlight unit, wherein the second layer includes a plurality of first concave portions respectively disposed between two adjacent light source devices (220, 225) of each light generating block (800, 810, 820, 830) and a second concave portion having a shape different from the plurality of first concave portions and disposed between two adjacent light generating blocks (800, 810, 820, 830), and characterized in that the second concave portion is filled with an adhesive material having a refractive index being lower than that of the second layer and in that each of the light generating blocks (800, 810, 820, 830) further includes at least one third layer (235, 251, 252) disposed on the second layer configured to diffuse the light propagated by the second layer. a first layer, a plurality of light source devices (220, 225) disposed on the first layer and configured to emit light, each light source device (220, 225) including a light emitting diode for generating the light, a reflection layer disposed on the first layer and configured to reflect the light emitted from the light source devices (220, 225), a second layer covering the light source devices (220, 225) and the reflection layer and configured to propagate the light reflected by the reflection layer, and a controller configured to selectively operate the light generating blocks (800, 810, 820, 830) of the backlight unit, wherein the second layer includes a plurality of first concave portions respectively disposed between two adjacent light source devices (220, 225) of each light generating block (800, 810, 820, 830) and a second concave portion having a shape different from the plurality of first concave portions and disposed between two adjacent light generating blocks (800, 810, 820, 830), and characterized in that the second concave portion is filled with an adhesive material having a refractive index being lower than that of the second layer and in that each of the light generating blocks (800, 810, 820, 830) further includes at least one third layer (235, 251, 252) disposed on the second layer configured to diffuse the light propagated by the second layer.