Patent ID: 7661864

Claim:
A back-light unit comprising: a light source for providing light exposed to a liquid crystal display panel of a transmission type liquid crystal display device, a planar light guide for changing a direction of propagation of said light to said liquid crystal display panel, and a prism sheet disposed adjacently to said planar light guide; wherein said prism sheet comprises: continuous prism structures extending throughout a surface of the prism sheet in close proximity, each prism structure comprising: a sheet base; a sheet top; and a reflective surface element for reflecting the light to the liquid crystal display panel, said reflective surface element extending from said sheet base to said sheet top and wherein said reflective surface element comprises: a peak; a small planar surface extending from the peak to an end portion; a small curved surface portion continuous to and starting from the end portion of the planar surface extending toward the sheet base; wherein the curved surface is larger than the small planar surface; and wherein a top of the prism structure extending above the small curved surface portion comprises a near triangular prism such that the peak forms an apex of the near triangular prism.