Shinichi Shinada

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.

37.3: Mercury‐Free, Simple‐Stuctured Flat Discharge LCD Backlights Ranging from 0.5 to 5.2‐in. Diagonals

Mercury-free flat discharge lamps with diagonal sizes ranging from 5.0 to 5.2 inches have been developed for LCD backlights. The lamps have simple structures with insulated electrodes. Uniform discharges are obtained by adjusting drive pulse voltage and waveforms. As lamp diagonal becomes larger, luminance and efficacy increa-se, and the dimming can be varied in wider range.

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...

DC Gas-Discharge Display Panel with LaB6 Thin-Film Cathode

A dc gas-discharge display panel with LaB6 thin-film cathodes is proposed for data information systems. A thin-film, having a crystallographic orientation of [100], was formed on a Ni thick-film using the electron-beam evaporation technique. The low work function of the crystallographic orientation provided a low operating voltage. The normal cathode fall potential for the thin-film cathode in a Ne+Ar (0.4%) gas discharge was approximately 80 V, about 1/2 that of the commonly used Ni thick-film cathode. The display panel consisted of two glass plates: cathodes were formed on one plate (substrate) and anodes on the other. The cathodes and anodes were perpendicular to each other, and were separated by barriers formed in parallel between the anodes. Low voltage, high luminance, high luminous efficiency and stable operation were attained without the use of Hg.

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.

Improving the luminance and luminous efficacy of miniature fluorescent lamps for liquid crystal display backlighting by using a double frequency drive

A new method of driving miniature fluorescent tubes for liquid crystal display backlighting, with diameters as small as 2 mm, has been devised with the objective of improving the luminance and luminous efficacies of such lamps. The driver voltage wave form consists of high frequency oscillations at the leading and trailing edges of conventional square-wave form voltage pulses of relatively low frequency. The wave form is produced simply by inserting coils between low frequency square-wave pulse generators and the lamp electrodes. A lamp driven in this way operates in a different discharge mode from the conventional glow discharge obtained in the absence of the coils. The twofold intensity increase of visible emission from the positive column region indicates that the vacuum ultraviolet emission increases, enhancing the excitation of the phosphor in the lamp. There is evidence that the luminous efficacy is also increased by a factor of 2 as a result of more efficient use of the input energy. The minimum vo...

A DC gas-discharge display panel for automobiles

A simple color instrument panel has been developed for automobile use that has a self-scanning function realized through a dc gas discharge. The panel, 120 mm × 270 mm × 5 mm in size, includes four separate bar graphs for the speedometer, tachometer, fuel gauge, and temperature gauge, as well as two digitmeters for the speedometer and odometer or trip distance display. Turn signals are also displayed. During fabrication of the panel all electrodes are screen printed simultaneously on a glass substrate using conductive ink. The anode and cathode electrodes are arranged reciprocally, and are connected to two busses and to two or four busses, respectively. Phosphors for the color display are deposited on nonglare front glass and are excited by UV radiation emitted by a negative glow discharge in a mixture of He + Xe.

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.

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.

Cold barium cathode: glow‐discharge characteristics in rare gases and application to gas‐discharge displays

Normal cathode fall Vn, reduced normal current density jn/p2 (p denotes pressure), and reduced position of negative glow dgp (dg is defined as a distance between the cathode surface and the brightest position in the negative glow) of a cold barium cathode in rare gases were measured. For He, Ne, Ar, Kr, and Xe, Vn=81, 82, 82, 73, and 71 V, jn/p2 =3.7, 3.0, 42, 41, and 37 μA cm−2 Torr−2, and dgp=0.75, 0.51, 0.21, 0.12, and 0.16 cm Torr, respectively. The operating voltage of the Ba cathode in 20 Torr Xe showed no change after 10 000‐h dc operation, and there was no observable chemical interaction between the barium and Zn2SiO4:Mn phosphor. Barium cathodes were formed in an 8‐in. diagonal gas‐discharge panel for TV display by thermally dissociating Ba(N3)2: the operating voltage was 1/2, and the power consumption and required cathode area were 1/4 of the same parameters for a similar panel with a Ni cathode.