Patent ID: 7852431

Claim:
A backlight device comprising: a light guide having a pair of main surfaces facing each other and a pair of edge surfaces facing each other, guiding the light from a light source arranged on one edge surface to both of main surfaces; and a control device controlling said light source to illuminate a main lighting region having relatively large size on a side of one main surface through said light guide, and to illuminate a sub-lighting region having relatively small size on a side of another main surface through said light guide, wherein said control device comprises mode selection switch selecting either a mode of illuminating the main lighting region or a mode of illuminating the sub-lighting region; and a power switch switching a power supply to said light source according to the mode selected by said mode selection switch, and wherein said power switch supplies whole light source with electric power in the mode of illuminating the main lighting region, and supplies a part of the light source less than the whole light source with electric power in the mode of lighting the sub-lighting region.