Light guide,method for manufacturing light guide,optical shutter and surface light source

Provided is a plate-type light guide (4) in which two opposing main surfaces are set as light emitting surfaces (6A, 6B) and at least one side-edge surface is set as a light incidence surface (5). In such a light guide, a light emitting mechanism (6) is provided in at least one region of at least one main surface; the haze value is 3% or lower in the region where the light emitting mechanism is provided; when a perfect diffuse light enters through at least one light incidence surface (5), a maximum emission angle (θA, θB), at which maximizes the intensity of emitted light (8) from the main surface is in a range from −60 degrees to +60 degrees with respect to a normal line to the main surface; and the utilization efficiency of emitted light is 15% or greater.