Patent ID: 6871976

Claim:
A wedge plate type light guiding plate for a front light mounted on a reflective display unit having a display portion, wherein the light guiding plate guides light from a light source and irradiates the light onto the display portion, the light guiding plate comprising: an incidence plane, which permits light to enter the light guiding plate; an opposite end plane opposite to the incidence plane; an exit plane facing the display portion, wherein light entering the light guiding plate through the incidence plane exits through the exit plane toward the display portion; and a reflection-exit plane opposite to the exit plane, wherein light reflected on the display portion passes through the exit plane and the reflection-exit plane, wherein a plurality of grooves are formed on the reflection-exit plane, wherein the grooves extend in a direction parallel to the direction in which the incidence plane extends, and are arranged at a predetermined pitch in a direction perpendicular to the direction in which the incidence plane extends, and wherein, in any adjacent pair of the grooves, the depth of the groove closer to the opposite end plane is greater than the depth of the groove closer to the incidence plane, and wherein the depth of the grooves substantially increases toward the opposite end plane.