PURPOSE: A back light assembly is provided to prevent light from leaking to an adjacent light guide part by using a partition arranged between the light guide parts. CONSTITUTION: A first partition(170a) is arranged in the empty space between a second light guide part(131b) and a first light guide part(131a). A second partition(170b) is arranged in the empty space between a third light guide part(131c) and a second light guide part. A partition(170) and a supporter support a diffusing plate. The light emitted from the lateral surface of a light guide part(131n) runs to an adjacent light guide part. The lateral surface of the partition reflects the light to an upper direction.
