A light guide plate for a backlight. The light guide plate includes: a light source unit for generating light; a light guide plate proximate to the light source unit and including an upper surface and a lower surface; and a light emission pattern configured to diffuse a portion of the light directed toward an image display panel, and a first straight pattern configured to channel the light along a direction substantially parallel to a direction of propagation of the light generated by the light source unit, both the light emission pattern and the first straight pattern being disposed on one of the upper surface and the lower surface of the light guide plate, in which the first straight pattern has peaks and valleys formed in alternating and repeating manner in a direction substantially perpendicular to a direction of propagation of the light generated by the light source unit.