Light guide plate and surface illumination device

A light guide plate comprising:

• a light input end surface from which light is introduced;
• a light output surface that outputs light spread in a planar manner externally;
• a flat main light guiding body including the light output surface;
• a light conducting portion that has a maximum thickness greater than the thickness of the main light guiding body and includes the light input end surface;
• a first slanted surface provided on the light conducting portion on at least one of a surface near the light output surface and a surface opposite thereto, the first slanted surface inclined from a first location that is thicker than the main light guiding body toward the outer surface of the main light guiding body;
• and
• a plurality of first pattern elements provided on the light conducting portion on at least one of a surface near the light output surface and a surface opposite thereto,
• wherein the first pattern elements are provided between a second location that is thicker than the main light guiding body and closer to the main light guiding body than the first location, and the end portion of the main light guiding body,
• wherein each of the first pattern elements extends parallel to a direction orthogonal to the light input end surface when the light output surface is viewed orthogonally,
• wherein ridges on the first pattern elements incline from the second location toward the outer surface of the main light guiding body;
• and
• wherein, when the main light guiding body is viewed from a side surface, the first pattern elements or the ridges between the first pattern elements incline at an average inclination smaller than the maximum inclination of the first slanted surface.