| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface light source element having high light utilization efficiency by disposing a light control plate having sugged parts rectangular in section on its surface on the emitting surface side of a light guide body. SOLUTION: A light source 1 and a light guide body 3 having a light incident surface and a light emitting surface in a surface shape are provided. A light control plate 7 having sugged parts rectangular in section is disposed in the emitting surface side of the light guide body 3. Preferably, a ratio between the width of a recessed part 9 and the width of a projecting part 8 in the light control plate 7 is set within a range of 1:5 to 5:1 for high light utilization efficiency. Preferably, a ratio between the height of a recessed part 8 in the light control plate 7 and an uneven cycle is set within a range of 1:5 to 5:1 also for high light utilization efficiency. In this surface light source element, by refraction in a wall surface 10 in the sugged parts formed to be rectangular or by full reflection in the flat of the recessed part 8, the energy of an emitted light shifted from a front direction is limited and thus light utilization efficiency is improved. |
