The present disclosure is directed to a liquid crystal display device including a display panel including a red pixel, a green pixel, and a blue pixel; and a backlight unit which emits light to the display panel. The backlight unit includes a light source which outputs a first color light; a color conversion layer which is configured to convert the first color light into a second color light; an optical sheet which diffuses or condenses the second color light; and an air gap formed between the color conversion layer and the optical sheet.