Multi-indicia fluorescent display tube

Claim 1

In a multi-indicia fluorescent display tube for use with a static driving circuit, having a casing formed of a base plate and a cover plate airtightly bonded to each other, said casing containing therein at least a plurality of pattern display sections provided on said base plate in a row for displaying patterns such as characters, figures and symbols and each composed of a plurality of segment anodes each having a fluorescent material layer thereon and a cathode stretched opposite to said pattern display sections, the base plate being insulating to electrically isolate the plurality of segment anodes thereon, the cover plate being light transparent in order to permit viewing of the display, an evacuated environment between the cover plate and the base plate to permit electrons from the cathode to be accelerated toward the segment anodes relatively unimpeded; the improvement which comprises shield electrode layers for at least preventing electrification, provided on the portions of said base plate in the vicinity of said segment anodes, and a diffusion electrode electrically connected to said shield electrode layer for levelling the density of electron current flowing from said cathode to each of said segment anodes during operation by the influence of a positive potential applied thereto with respect to the potential of said cathode, said positive potential maintained between the anode potential and the average of said cathode and anode potentials, said diffusion electrode being provided on the portion of the inside surface of said cover plate opposite to said pattern display sections or in the vicinity of the inside surface of said cover plate.