US Patent 7980718 Illuminating device, display device having it, and television receiver

A thin, lightweight illuminating device, in the form of a backlight unit, is capable of securing even brightness and improving light use efficiency. The backlight unit includes a light source including a plurality of light emitting diodes mounted on a mounting surface of a board, a diffusion plate which has a light introduction surface that faces the mounting surface of the board at a predetermined distance therefrom and diffuses the light emitted from the plurality of light emitting diodes, and a reflection sheet that is adhered to the mounting surface of the board. A light emission direction of the plurality of light emitting diodes is parallel or substantially parallel to the light introduction surface of the diffusion plate.