LENS FILM FOR SURFACE LIGHT SOURCE

摘要

PROBLEM TO BE SOLVED: To prevent optical adherence at the time of overlapping a lens film with a light guide or another lens film so as to prevent increase of the side lobe light by providing a back face with fine unevenness with specific centerline mean roughness and ten-point's mean roughness. SOLUTION: A lens film 10 for a surface light source is so constituted that a lens layer 2 is laminated on the surface side of transparent base material 1 and that a mat layer 3 is laminated on the back side, respectively through adhesive layers 4. These adhesive layers 4 are occasionally omitted. The roughness of fine unevenness of the surface of the mat layer 3 is so set that centerline mean roughness Ra is in a range of 0.5<=Ra<=2.0μm and that centerline roughness Rz ten-point's mean is in a range of 1.5<=Rz<=6.5μm. The roughness of fine unevenness based on both characteristic values is thus set in these ranges so as to reduce the side lobe light and to prevent the generation of interference fringes of a uniform thickness. The lens layer 2 or the mat layer 3 is formed of transparent material, and the set material of ionizing radiation setting resin or the like can be used.