Surface light source device and display device

摘要

In a front light equipped with minute unevennesses (30) for prevention of reflection on the light emitting surface (29) of a transparent plate (26), a device for suppressing the generation of diffracted light by the unevennesses (30) is provided. In a front light equipped with a light source (24) and a transparent plate (26) emitting light from a light emitting surface (29) which is situated at the reverse side against an observation side surface by conducting light from the light source (24) , the reflection preventive patterns (31) comprising the minute unevennesses (30) for prevention of reflection are formed on the light emitting surface (29). When a wavelength of visible light with the shortest wavelength among light which is emitted from the light source (24) is lambda min, the refractive index of the transparent plate (26) is n1 and the refractive index of air is n0, the period p of the minute unevennesses (30) satisfies the following equation. <DF>p < lambda min/(n0 + n1). </DF> Thereby, it can be prevented that the diffracted light is emitted from the reflection preventive patterns (31) (light emitting surface (29)) of the transparent plate (26). <IMAGE>