Surface light source device and image display unit comprising a light guide plate with prism protusions

摘要

An LED (5) has many prism projections (12) extending in a direction away from the vicinity of the incident surface are formed in parallel on at least one of the outgoing surface of the plate and a surface (10) opposite to the former surface. The side-surface side portions (10b) of the prism projections are so formed as to gradually reduce the heights of the projections toward the incident surface.