Shigeo Mikoshiba

Saturation of Zn2SiO4 : Mn luminescence under intense vuv excitation

Output luminescence of Zn2SiO4 : Mn phosphor saturates under intense vacuum ultraviolet radiation having a relatively high excitation duty ratio. The saturation is attributed to the depletion of activators at the ground level. This depletion originates from the long decay time constant of the phosphor. The saturation mechanism is explained analytically using a simple model, and the conditions for efficient phosphor excitation are derived.

Limitations on luminance characteristics of gas‐discharge color display panels

Relations between electrical input and optical output of gas‐discharge display panels are developed in which resonance radiation from the xenon negative glow is employed to excite phosphor of appropriate color. A panel having optimized cell configuration for maximum luminance can yield white‐area luminance of only 10 fL at most when reproducing TV images using a one line at a time addressing technique. The optimization reduces the luminous efficiency to an unrealistically low value.

An intense and efficient source of vacuum ultraviolet radiation: Low‐ pressure Xe Townsend discharge

An intense vacuum ultraviolet spike 0.2 μs in width is observed at the initial stage of low‐pressure Xe discharge, i.e., Xe Townsend discharge, in submillimeter tubes. The intensity of the 147 nm resonance line reaches 1.3 W/cm2, about 200 times stronger than that obtained from the steady‐state Xe positive column. Efficiency of the vacuum ultraviolet radiation exceeds 24%, or 32 lm/ W when green phosphor is excited, four times higher than that of the positive column, or more than an order of magnitude higher than that of the negative glow. This high intensity and efficiency originate from the optimized electron energy which can be adjusted externally by changing the electric field and pressure, contrary to that in the positive column or negative glow. Another important feature of the Townsend discharge is its wide dynamic range of operation, which is advantageous when driving a panel having a large number of cells with scattered discharge characteristics. Consequently, a gas discharge display panel utiliz...

A flat gas-discharge panel TV with good color saturation

A flat 8-in diagonal gas-discharge color-TV has been fabricated and operated at 5 fL in white with a luminous efficiency of 0.05 lm/W. The contrast ratio was measured at better than 300:1, owing to the special configuration of the discharge cell, and also the careful adjustment of gas loading conditions. The CIE chromaticity coordinates for red, green, and blue (R,G,B) exhibited in the panel were, respectively, (0.56,0.31), (0.22,0.68), and (0,17,0.14)-- reasonably good values considering those of NTSC. The electrical and optical properties of the panel as well as the techniques for real-time TV picture display are discussed.

A positive column discharge memory panel for color TV display

The dc gas-discharge display panel introduced combines internal memory characteristics with the positive column discharge, yielding high luminance and efficiency. The nature of the memory function is based on shifts in the discharge path between display and auxiliary discharge spaces. Because of this operating principle, the panel has a switching time as fast as 10 µs, enabling use of the panel for real-time color TV displays with 64 gray levels.

Breakdown voltage enhancement by wall charges in repetitively pulsed discharge tubes

It is shown that, over a narrow range of amplitudes, applied voltage pulses can deposit wall charges inside a discharge tube without causing breakdown of the interelectrode gas: these charges enhance the breakdown voltage of the interelectrode gas for subsequent pulses, and the enhancement decays exponentially with the pulse interval. The enhancement decays more rapidly when the temperature of the discharge tube is increased so as to reduce its surface resistance, which furnishes the main leakage path of the wall charges. It is suggested that breakdown voltages of closely packed, repetitively pulsed discharge tubes are frequently enhanced by wall charges.

Use of barium cold cathodes for low voltage DC-gas discharge color display panels

A technique for providing barium cold cathodes in a dc-gas discharge color display panels has been developed. A 21 × 111 cell green panel, fabricated in accordance with this technique, yielded a maintenance voltage of 88 ± 8 V. This value is approximately ⅓ that for conventional nickel cathode panels, resulting in a threefold increase in luminous efficiency.

A 100 lm/W efficacy low‐pressure Xe discharge tube

The luminous efficacy of a Zn2SiO4:Mn‐coated, low‐pressure Xe‐positive‐column fluorescent tube is found to be as high as 100 l/W which corresponds to an electric to 147‐nm radiation energy conversion factor of 66%. This high efficacy can be attained under conditions (pressure)×(column diameter)≃1 Torr cm and (current density)?3 mA/cm2.

Discharge tube breakdown voltages for alternating polarity pulses

The breakdown voltage (VKB) of a cold cathode glass discharge tube, driven by negative voltage pulses, is greatly increased by charges which the pulses deposit on the inside walls of the tube. It is shown that VKB can be almost halved by neutralizing these negative wall charges with positive pulses of amplitude V+, applied to the tube electrodes. Explanations are given of the dependence of VKB on V+ and the implications for gas discharge display systems are also considered.

Formation of Current Leakage Paths at the Interface between Dielectrics in Intense Electric Fields in a Gas Discharge Display Device

Electrically conducting paths were formed at the interface between a soda-lime glass substrate and a lead-glass overglaze in a gas discharge display panel under an electric field of 7 kV/cm. This resulted in the panel malfunctioning after 4000-h operation. The current leakage paths consisted of Pb atoms, produced by the reduction of PbO by Na ions. The rate of path formation was strongly sensitive to the electric field, substrate temperature, and also to the presence of ionized gases in the vicinity of the interface. Methods of avoiding insulation failure include using a Pb-free dielectric overglaze, sandwiching the electrodes between lead glasses, and reducing the intensity of the electric field.