Patent ID: 7927004

Claim:
A backlight unit comprising: a backlight chassis arranged to house a lamp, which includes support surfaces at four edges that are arranged to support optical sheets; and a frame having a picture frame shape extending continuously along an entire outside periphery of the backlight chassis and arranged to hold the optical sheets with the support surfaces of the backlight chassis, the optical sheets being interposed between the frame and the support surfaces; wherein the backlight chassis includes: two positioning pieces arranged on its support surfaces to position the optical sheets at predetermined positions with respect to the support surfaces; and at least one projection on each of the support surfaces; positions of the positioning pieces correspond to approximate centers of two longer edges of the optical sheets; the frame has at least one projection on a surface of each of its four edges; and each of the at least one projection of the backlight chassis and of the at least one projection of the frame are in contact with a portion of a surface of the optical sheets that is arranged to oppose the backlight chassis, and the frame respectively, wherein at least one of the two positioning pieces has a convex portion which fits into a concave portion including a notch at the approximate center of the corresponding one of the two longer edges of the optical sheets.