SURFACE LIGHT SOURCE DEVICE OF SIDE LIGHT TYPE

摘要

PROBLEM TO BE SOLVED: To avoid occurrence of sticking of a light control member by providing a surface light source device of side light type having a surface light control member to correct the directionality, equipping the light source device with a plate-shaped member having a light emission surface, and forming this light emission surface in the specific arithmetic mean surface roughness range. SOLUTION: A surface light source device of side light type has a plate- shaped member as a light scattering light member 11, and illumination light is put incident from its end face and emitted upon deflection from the light emission surface 12, wherein the directionality is corrected by a light control member in sheet form arranged on the light emission surface 12. The light emission surface 12 is formed into a mat surface through a matting process so that a range is obtained where an emitted light having an arithmetic mean surface roughness Ra of 0.02-0.25 (μm) is not diffused. Thereby it is made practicable to effectively avoid sticking of a prism sheet consisting of light control member to the light emission surface 12 which may result in a remarkable deterioration of the grade of a display screen.