Surface light source device, light guide element used for surface light source device, and method for producing light guide element

摘要

Disclosed is a plate-like light guide element (24) provided with a light incident surface, a light exit surface (242), and an underside surface (243) disposed on the opposite side of the light exit surface (242). A foamed surface layer (244) is formed on at least a part of at least either the light exit surface (242) or the underside surface (243). The foamed surface layer (244) contains air bubbles and has a recessed sectional surface including the normal direction of the light exit surface (242) or the underside surface (243). The light guide element (24) is produced by performing infrared laser etching for at least a part of at least one of the main surfaces of a plate-like light guide element material composed of an acryl resin plate produced by a continuous plate production method, to form the foamed surface layer (244).