| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a surface light source device with high light extraction efficiency, high brightness in a front direction, and reduced color unevenness. <P>SOLUTION: A surface light source device comprises an organic EL element including a light emitting layer, and has a device light emitting surface for emitting light from the organic EL element. The surface light source device further comprises a light emission efficiency improving part positioned nearer the device light emission surface than the organic EL element. The light emission efficiency improving part comprises a first structure layer, and a second structure layer contacting the first structure layer and positioned nearer the device light emission surface than the first layer structure. The first structure layer is a layer made of a material of a refraction factor n1 having a first uneven structure having an inclined plane whose inclined angle θ1 is 60-80°, on the surface of the device light emission surface side. The second structure layer is a layer made of a material of a refraction factor n2 having a second uneven structure having an inclined plane whose inclined angle θ2 is 40-50°, on the surface of the device light emission surface side. n1 and n2 satisfy a relationship of n2-n1≤-0.12. <P>COPYRIGHT: (C)2012,JPO&INPIT |
