Patent ID: 8111354

Claim:
A backlight unit supplying light from a LED light source to a liquid crystal panel via a light guide plate and a light diffusion plate; wherein the light guide plate is formed such that a thick portion and a thin portion are repeated at certain intervals, the repeated thick portions and the repeated thin portions gradually decreasing in thickness; wherein a surface facing the light diffusion plate is in parallel therewith, and a surface facing the opposite side of the light diffusion plate forms a slope from the thick to thin portions; wherein the LED light source is attached to a lateral side of each of the thick portions; wherein grooves are formed in the light irradiation direction of the LED light source at equal intervals on the side facing the light diffusion plate; wherein each of the grooves is formed in an concave shape (V-shape or trapezoid-shape); wherein each of the grooves is deep at the thick portion and shallow at the thin portion, forming a slope bottom surface of groove; wherein there is a relation 0.2/30<=W/D<0.1 where D denotes the distance between the light guide plate and the light diffusion plate, and W denotes the width of each of the grooves; and wherein an inclination angle θ relative to the center of each of the grooves is between 9 and 15 degrees inclusive.