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

A light guide plate comprising:

• a light exit surface;
• a back surface opposed to the light exit surface;
• at least one light entrance surface consisting of part of a side surface between the light exit surface and the back surface;
• and
• a counter surface consisting of part of the side surface and opposed to the one light entrance surface in a first direction;
• said light guide plate further comprising:
• a body portion;
• and
• unit shaped elements defining the light exit surface, the unit shaped elements being arranged on one-side surface of the body portion in an arrangement direction intersecting the first direction;
• wherein each unit shaped element extends in a direction intersecting the arrangement direction;
• wherein in a main cross-section parallel to both the arrangement direction and a normal direction of the one-side surface of the body portion, a light exit surface angle, which is an angle of a contour of each unit shaped element with respect to the one-side surface of the body portion, is more than 10° and not more than 30° in a zone of the contour of each unit shaped element, a width of the zone along the arrangement direction being not less than 35% and not more than 70% of a full width of the unit shaped element;
• wherein the unit shaped elements each have, in the main cross-section, a pentagonal shape whose one side lies on the one-side surface of the body portion and whose two sides lie between a top and each end of the contour, or a shape in which one or more of the corners of the polygonal shape are chamfered;
• and
• wherein of said two sides lying between the top, the farthest point from the one-side surface, and each end, connecting to the one-side surface, of the contour, the top-side side has a light exit surface angle of more than 10° and not more than 30°, and the end-side side has a light exit surface angle of more than 30° and not more than 60°.