Surface light source device and LCD unit

A surface light source device, comprising:

• a light guide having a top surface, a bottom surface and a pair of light incident surfaces located between both ends of the top surface and the bottom surface and located on opposite surfaces with respect to each other, the light guide including a transparent resin and formed in a substantially tabular shape, the top surface and the bottom surface of the light guide formed in a substantially rectangular shape and being substantially perpendicular to the light incident surfaces, the top surface of the light guide including a plurality of linear convexes that extend in a direction substantially perpendicular to the light incident surfaces and are aligned along a length substantially parallel to the light incident surfaces at a prescribed interval, each of the linear convexes formed in a substantially triangular cross-sectional shape in an aligned direction of the linear convexes, the bottom surface having an imaginary central line divided into two equal parts located between the pair of light incident surfaces, and including a plurality of dots formed in at least one of a minim convex shape and a minim concave shape, wherein the at least one of the minim convex shape and the minim concave shape included in the bottom surface of the light guide is formed as a substantially triangle truncated cone having a direction of a normal vector of a slant surface, wherein the direction of the normal vector of the slant surface is located in a direction substantially perpendicular to one of the light incident surfaces that is closer to the slant surface of the plurality of dots, and an imaginary extended surface of the slant surface enlarges toward the one of the light incident surfaces and also intersects with the direction of the normal vector of the slant surface at an acute angle toward the one of the light incident surfaces, and each of the pair of light incident surfaces formed in a substantially planar shape, wherein each direction of the plurality of dots located on one of the two equal parts and each direction of the plurality of dots located on another one of the two equal parts are substantially opposite with respect to the imaginary central line in a direction between the pair of light incident surfaces;
• a pair of linear LED light sources each having a longitudinal direction and including a plurality of LEDs in each longitudinal direction, each of the linear light sources located adjacent a respective one of the pair of light incident surfaces of the light guide and facing the respective one of the light incident surfaces, the plurality of LEDs included in each of the linear LED light sources being divided into a plurality of groups, and each of the groups included in each of the linear LED light sources configured to emit light into the light guide independently with respect to each of the other groups via the respective one of the light incident surfaces facing each of the linear light sources, wherein each of the groups included in one of the pair of linear LED light sources faces a respective one of the groups included in another of the pair of linear LED light sources with respect to each other via the light guide;
• an LED driving circuit configured to control light intensity of light emitted from each of the groups included in the linear LED light sources;
• a reflective sheet having a top surface located adjacent the bottom surface of the light guide;
• a prism sheet having a top surface and a bottom surface located adjacent the top surface of the light guide, the prism sheet including a transparent resin and formed in a substantially sheet shape, the top surface of the prism sheet including a plurality of triangular prisms that extend in the direction substantially perpendicular to the light incident surfaces of the light guide and are aligned along a length substantially parallel to the light incident surfaces of the light guide at a different interval from the prescribed interval of the plurality of linear convexes of the top surface of the light guide, each of the triangular prisms formed in a substantially triangular cross-sectional shape, and the bottom surface of the prism sheet formed in a substantially planar shape;
• and
• a diffusing sheet having a top surface and a bottom surface located adjacent the top surface of the prism sheet, the prism sheet including a transparent resin and formed in a substantially sheet shape.