Patent ID: 8467014

Claim:
A back light unit for a liquid crystal display comprising: transparent electrodes; a pair of transparent plates which are disposed to face each other, the transparent electrodes being formed on corresponding predetermined areas of surfaces facing each other of the transparent plates; a polymer dispersed liquid crystal layer which is formed in a space between the transparent plates and is polymer dispersed liquid crystal; a light source module including a frame which is disposed behind the transparent plates, an area of the frame corresponding to the predetermined areas being empty or transparent, and a planar light source or a plurality of light sources which is mounted to the frame to be disposed at an area corresponding to the predetermined areas of the transparent plates; and a light switch plate, which is disposed behind the light source module, including a light switch member, which can be selectively converted into a transparent state, being disposed at an area of the light switch plate corresponding to the predetermined areas, and another area of the light switch plate being made of nontransparent material.