Light guide plate, surface light source device, transmissive display device

A light guide plate having a light incident surface on which light is incident, a light emitting surface which intersects the light incident surface and emits light, and a back surface which faces the light emitting surface, the light guide plate emitting the light from the light emitting surface while guiding the incident light from the light incident surface in a light guide direction,

• wherein a plurality of light-emitting-side unit optical shapes are arranged in the light emitting surface in a direction which is perpendicular to the light guide direction and is perpendicular to a thickness direction of the light guide plate,
• wherein the light-emitting-side unit optical shape extends in the light guide direction and is formed in a groove shape which is recessed from the light emitting surface, and a bottom of the groove shape is formed on a concave surface which is concave toward the back surface side,
• wherein flat inclined surfaces which are inclined from an edge portion where recessing from the light emitting surface is started toward the bottom side are formed in two end portions of the concave surface in an arrangement direction, and
• wherein, when a width of the light-emitting-side unit optical shape in the arrangement direction is denoted by W21, a maximum inclination angle θ of the inclined surface with respect to the light emitting surface satisfies 20°≦θ≦45°, and a radius of curvature r of the concave surface satisfies r≧W21/(4×sin θ).