Thin-type picture display device with means for effecting electron transport by secondard emission

Picture display device having a vacuum envelope with a front wall supporting a luminescent screen at its inner side and a rear wall at a short distance therefrom, connected by side walls. The envelope accommodates a plurality of adjacent electron sources and juxtaposed, local electron ducts cooperating with these sources and having walls of substantially electrically insulating material having a secondary emission coefficient which is suitable for transporting, through vacuum, produced electrons in the form of electron currents. Means are provided to make each electron current substantially travel along a particular wall of its electron duct, as well as means for withdrawing each electron current at predetermined locations from its duct and directing it towards the luminescent screen for producing a picture composed of pixels.