A light guiding plate according to the invention is mounted in a vertical
backlight module between an illumination element and a diffusion plate.
The light guiding plate has a flat light incidence surface at a bottom of
the light guiding plate and a light emergence surface at a top of the
light guiding plate. The light incidence surface faces the illumination
element. The light emergence surface is adjacent to the diffusion plate
and has a concave portion right above the illumination element. The
concave portion of the light guiding plate further diffuses the light
transmitted right above the illumination element to homogenize the light
emergence and increase the glow for display of the backlight module. The
total thickness of the vertical backlight module thereby is reduced to
minimize the volume of the backlight module.
