Led back-light unit and display device

A back-light unit comprising:

• a plurality of substrates;
• a plurality of light sources respectively disposed on the plurality of substrates and configured to emit light;
• and
• N (N≧2) light guide plates respectively disposed adjacent to the plurality of light sources, each light guide plate including a light incidence part having a light incidence surface for receiving light emitted in a first direction from a corresponding light source, and a light emission part for emitting the received incident light in a second direction different than the first direction,
• wherein at least one of the light guide plates comprises light-extracting surface patterns disposed on the light emission part, and
• wherein the light-extracting surface patterns comprise a predetermined region of light-extracting surface patterns of a K-th (K=1, 2, . . . , N−1) one of the light guide plates, which is adjacent to the light incidence part of a “K+1”-th one of the light guide plates, having a higher pattern-density than the other region of light-extracting surface patterns of the K-th one of the light guide plates.