A DC Plasma Display Panel With Inherent Storage

Normally, the impedance of the glow discharge exploited in a d.c. plasma panel is low, and if information is to be stored in the display itself, the current in the cells must be controlled by a series resistor in each cell. Empirical studies of cell characteristics have shown the relationship between the impedance and such parameters as cell geometry, cathode material and gas composition and pressure. By suitable choice of these parameters, in particular the use of graphite as the cathode material, it was found possible to design a d.c. storage plasma panel, where the cell impedance is sufficiently high to obviate the need for a series resistor. A new theoretical model is proposed which considers the averaged field rather than the instantaenous field when deriving the ionization across the cell in the non-uniform field glow-discharge condition. The theory also takes into account losses at the cell walls and the gas density changes due to the heat dissipation in the cathode region. The model is consistent with the empirical data, and explains some of the discharge characteristics not accounted for by earlier theories. The construction and characteristics of an experimental 128 character panel with graphite cathodes operating in the storage mode is described.