US Patent 9798063 Light guide plate and surface illumination device

A light guide plate has a light conducting portion having a light input surface for introducing light into the light guide plate, a main light guiding body that is thinner than a maximum thickness of the light conducting portion, and disposed continuously from the light conducting portion, a slanted surface that is disposed on the light conducting portion on at least one of a surface near a light output surface and a surface opposite the surface near the light output surface, and that is inclined from a section of the light guide plate that is thicker than the main light guiding body toward an end of the main light guiding body, two cylindrical surfaces that cut into the slanted surface, and a groove formed by the two cylindrical surfaces.