Provided are surface light source devices and LCDs having isotropic and
wide viewing angles. A surface light source device for illuminating an LCD comprises
a light guide plate hiving a back face provided with a great number of micro-reflectors.
Light beams P1, P2 representing an inner input light are inner-reflected
by first and then second inner reflection faces or in inverse order, respectively
to become a first and second inner output lights Q1 and Q2 which
are non-parallel to each other, providing an emission having angular intensity
characteristics showing two peaks. Peak splitting of the emission is dissolved
by a light diffusion sheet disposed along an emission face of the light guide plate,
causing an LCD panel to be illuminated by an isotropic and wide-view-angled illumination
output light. The first and second inner reflection faces may be inclined oppositely
and symmetrically to each other with respect to an imaginary reference plane that
passes a valley bottom of a micro-reflector and extends perpendicularly to the
emission face.
