Patent ID: 8488090

Claim:
A backlight unit comprising: a light source; and a liquid crystal panel which electrically controls a liquid crystal grating and forms a desired light pattern by using light incident from the light source, wherein the liquid crystal panel comprises: a first substrate which guides the light incident from the light source disposed at at least one side of the first substrate; a transparent electrode disposed on a surface of the first substrate; a second substrate; a reflective electrode disposed on a surface of the second substrate facing the transparent electrode disposed on the first substrate; a liquid crystal layer disposed between the transparent electrode and the reflective electrode; and a transparent film disposed between the transparent electrode and the reflective electrode, the transparent film comprising a surface contacting the liquid crystal layer and patterned with grooves or ribs extending in parallel with a direction in which the light source extends, and the transparent film having a refractive index corresponding to at least one of an ordinary refractive index and an extraordinary refractive index of liquid crystals of the liquid crystal layer, wherein the liquid crystal layer and the transparent film form the liquid crystal grating according to whether refractive indices of the liquid crystal layer and the transparent film match based on a voltage applied between the transparent electrode and the reflective electrode, and wherein the liquid crystal grating is electrically controlled to form the desired light pattern.