Abstract: A light guide plate has an emission face provided with a plurality of projection rows. Each projection row consists of a pair of slopes, a first slope (a slope far from an incidence end face) and a second slope (another slope near to the incidence end face). An inclination angle of the first slope with respect to an imaginary plane perpendicular to a frontal direction decreases gradually in first region on the emission face (or back face) according to an increasing distance from the incidence end face, then increasing gradually in second region according to an increasing distance from the incidence end face. The inclination angle at an incidence-end-face-side end of first region is greater that at a distal-end-face-side end of second region. Variation of the inclination angle in the first region is greater that in the second region.

Abstract: Provided are a light guide plate realizing a high and uniformalized illumination brightness without reducing emission directivity, a surface light source device and an image display which employ the light guide plate. The light guide plate has an emission face provided with a great number of projection rows. Each projection row consists of a pair of slopes, a first slope (a slope far from an incidence end face) and a second slope (another slope near to the incidence end face). Angle ?a is defined as an inclination angle of the first slope with respect to an imaginary plane perpendicular to a frontal direction.