A flat panel display comprises the following components. A display module has a lower glass substrate for fabricating thin film transistors, an upper glass substrate for fabricating a color filter, and a displaying molecule layer inserted between the lower glass substrate and the upper glass substrate. The lower glass substrate is connected electrically to a control circuit board via a flexible printed circuit board for driving the thin film transistors. And a backlight unit is fabricated beneath the display module and has a lightguide, a lamp disposed aside the lightguide to emit lights into the lightguide in the edgelight form, and a plurality of optical films disposed on the lightguide for scattering the lights emitted from the lightguide uniformly. The backlight unit comprises a sensor board disposed beneath the lightguide for receiving inputting signals from a signal stylus above the flat panel display. And the sensor board has a reflector surface layer for reflecting lights dispersed from a lower surface of the lightguide.