Patent ID: 7488095

Claim:
A prism sheet of a backlight unit for an LCD, the prism sheet having a structural surface ( 14 ) on one side thereof and a flat surface ( 15 ) opposing the structural surface on another side thereof, the structural surface ( 14 ) including a linear arrangement of right-angled isosceles triangular prisms arranged in parallel and configured to form a plurality of peaks ( 11 ) and valleys ( 12 ), each of the prisms having perpendicular surfaces that slant by an angle of approximately 45.degree. with respect to the flat surface ( 15 ), wherein the structural surface ( 14 ) is configured to have non-planar peaks ( 11 ) with a maximum height and a minimum height along a length direction of the peak, and a curved layer ( 17 ) having the same cycle as a cycle of height variation of the peak is formed at a boundary surface ( 16 ) between the structural surface ( 14 ) and the flat surface so as to maintain the right-angled isosceles triangular prisms formed due to a difference between the highest point and the lowest point of each of the peaks to have a predetermined size so that a distance between the valleys ( 12 ) is uniform along the length direction, and wherein the peak has a height variation of 0.125 - 2.5 μm.