Patent ID: 7490971

Claim:
A planar lighting device comprising: linear light sources arranged in parallel to each other; a light guide plate comprising a flat light exit surface, a rear surface opposite to said light exit surface and parallel grooves formed in said rear surface, for accommodating said linear light sources, respectively, wherein a cross-section of said light guide plate perpendicular to said parallel grooves has a rear surface profile of said rear surface such that convex portions are formed at respective portions where said parallel grooves are formed, while concave portions are formed between adjacent parallel grooves, and a thickness of said light guide plate in each concave portion decreases from each parallel groove toward either midpoint between adjacent parallel grooves and is thinnest at said midpoint; and a support member arranged in a side of said rear surface of said light guide plate, for supporting said light guide plate, wherein said support member has a first surface facing said rear surface of said light guide plate and a second surface opposite to said first surface, wherein a cross-section of said support member perpendicular to said parallel grooves of said light guide plate has a first surface profile of said first surface such that a portion of said first surface facing each convex portion of said rear surface profile of said light guide plate is identical to the profile of each concave portion of said rear surface profile of said light guide plate, while a profile of said second surface of said support member is identical to a profile of said flat light exit surface of said light guide, and wherein said support member further comprises parallel grooves formed in each of a portion of said first surface facing each concave portion of said rear surface profile of said light guide member parallel to each other, respectively, and each parallel groove of said support member has substantially a same shape as said parallel groove formed in each of said convex portions of said light guide plate; wherein the linear light sources are disposed within the parallel grooves formed in the light guide plate, and the parallel grooves formed in the support member are devoid of linear light sources.