Surface light source device and its light guide plate

A mobile device comprising

• a light source configured to transmit light;
• a light guide plate comprising:
• a light introduction part comprising an end face on which light from the light source is incident;
• and
• a light guide plate body disposed continuously to the light introduction part and comprising a thickness smaller than a maximum thickness of the light introduction part,
• wherein the light guide plate body comprises a light emitting surface that emits the light incident from the end face,
• wherein the light introduction part comprises an inclined face disposed on at least one side of the light guide plate,
• wherein the inclined face is inclined smoothly from a surface of a part thicker than the light guide plate body toward an end of the light guide plate body,
• wherein an optical pattern part comprising a linear pattern element is disposed near a region in a proximity of the inclined face in a face on a light exit side of the light guide plate body,
• wherein the liner pattern element has a wedge projection shape or a groove projection shape,
• wherein the optical pattern part is formed such that a ridge line and a valley line are alternately arranged along a width direction of the light guide plate, in a region configured to be positioned in front of a light source opposite the end face, and comprising a width equal to that of the light source, in a section of the optical pattern part cut in parallel to the end face,
• wherein a slant face connecting any of the ridge lines of the optical pattern part and one of valley lines adjacent to the ridge line and a slant face connecting the ridge line and the other valley line adjacent to the ridge line are asymmetric with respect to a straight line passing through the ridge line and perpendicular to the light emitting surface,
• wherein at least one set of the asymmetric shape parts comprising different shapes exists on both sides of a plane passing through center of light emission of the light source and perpendicular to the end face and the light emitting surface,
• wherein in the region, and as at least one of two regions separated by the plane, when a normal is set to a slant face connecting a ridge line and a valley line which are adjacent in the optical pattern part, from the inside to the outside, a sum of breadths of the slant faces in which the normal is inclined toward the plane side is larger than a sum of breadths of slant faces in which the normal is inclined toward the side opposite to the plane,
• wherein in the region, breadth of the slant face in which the normal is inclined to the plane side in the normals set to the two adjacent slant faces is larger than or equal to the breadth of the slant face in which the normal is inclined to the side opposite to the plane,
• wherein at least a part of a valley line in the optical pattern part is located on the inner side of the light guide plate body more than the light emitting surface, and
• wherein at least a part of a ridge line in the optical pattern part is located on the center side of the light guide plate body more than the light emitting surface;
• and
• a liquid crystal panel disposed so as to face the light emitting surface of the light guide plate.