A backlight unit includes a light source which generates a first light; a quantum dots member which is spaced apart from the light source by a first distance and converts the first light into a second light; a guide member which lengthwise extends in a first direction and fixes positions of the light source and the quantum dots member; and an optical member which reflects the second light. A blade adapter is recessed into the bottom of the housing to form a bearing seal and position the blade. The beam has a high directivity in a certain scanning direction.