SURFACE LIGHT SOURCE DEVICE AND DISPLAY DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a surface light source device capable restricting asymmetry in brightness angle distribution in a lateral direction with respect to a front direction while keeping a direction where a peak luminance can be obtained in the front direction and facilitating a manufacturing through a plate making of a unit prism.SOLUTION: A surface light source device 20 comprises a light guide plate 30, an optical sheet 60 and a light source 24. The optical sheet has a plurality of unit prisms protruded toward the light guide plate and arranged in the first direction. The unit prism includes the first prism surface 71 facing one side in the first direction and the second prism surface 72 facing to the other side of the first direction. The second prism surface 72 includes three element surfaces 73 with different inclination angle to each other. A width Wof the unit prism along the first direction, an angle δformed by the first prism surface 71 in respect to a normal direction of the main body part, a length Wof the first prism surface 71 along the first direction, an angle θformed by each of the element surfaces in respect to the first prism surface 71 and a length Wof each of the element surfaces along the first direction may satisfy the predetermined conditions.SELECTED DRAWING: Figure 2