US Patent 7364339 Flexible backlight unit for key of input device

Provided is a backlight unit for a key of an input device. The unit includes a light guide plate and at least one light emitting unit. The light guide plate is formed of flexible transparent resin and has a light guide pattern portion in which a plurality of engraved patterns are formed in a plurality of requirement character shapes so that light can be diffused and scattered at desired luminance from a necessary light emitting portion, using a minimal number of light sources. The light emitting unit is installed at a side wall of the light guide plate.