Influence of gas mixture ratio on the luminous efficiency in surface discharge alternating current plasma display panels New combination of a three-component gas, Ne-Xe-Ar, for a high efficiency plasma display panelThe dependence of the efficacy of an alternating current surface-discharge plasma display panel on the gas pressure is investigated for several Xe-Ne gas mixtures. In monochrome green 4 in. test panels the efficacy trends and emission spectra are examined for increasing gas pressure and/or Xe concentration. The measured panel efficacy and emission characteristics are compared with the results of a numerical discharge model. It is found that the discharge efficiency for the cell geometry used in present-day commercial products can be increased significantly by using a larger Xe partial pressure. An increase of the electron heating efficiency and of the Xe excitation efficiency contribute about equally to the efficacy increase. The contribution of the increasing Xe dimer radiation fraction to the efficacy improvement is relatively small. These findings are applied in a 4 in. color test display with a design that resembles the one used in present-day commercial products and contains a gas mixture of 13.5% Xe in Ne at 800 hPa. For realistic operating conditions an efficacy of 3.8 lm/W at a white luminance of 2010 cd/m 2 is obtained. Furthermore, the panel chromaticity improves for increasing Xe partial pressure due to decreasing Ne emission.

The dependence of the panel efficacy of an alternating current-surface-discharge plasma display on the input power is investigated. Test panels with a design resembling the one used in main stream commercial products are used. The input power is varied in two ways: namely by changing the dielectric layer capacitance (thickness) and by changing the sustain voltage. An interesting different behavior is found: for increasing capacitance the efficacy decreases markedly, whereas for increasing sustain voltage the efficacy increases slightly. The different behavior is attributed to changes in the ion heating losses. It is found that plasma saturation, which implies a fundamental trade-off between luminance and efficacy, is not significant at practical input power values. A high luminance and a high efficacy are concurrent for a plasma panel design with a low dielectric layer capacitance and a high sustain voltage.

A study was made of the darkening of sodium and potassium silicate glasses by a low pressure mercury discharge, using electron spectroscopy, Rutherford backscattering, and transmission electron microscopy. Initial changes in glass exposed to a mercury discharge are twofold: (i) mercury from the discharge penetrates very rapidly into the glass to depths of the order of 1 nm. (ii) Alkali ions migrate more slowly away from the surface in a photoelectric field that is caused mainly by trapping of photoelectrons. However, mercury entering the glass does not replace alkali ions. Rather, the mercury penetrates into voids in the glass network that are sufficiently close to the surface. From this "surface reservoir" mercury migrates slowly deeper into the glass. This migration is slower in mixed than in single alkali glasses. We assume that mercury migrates as ions in a photoelectric field, assisted by photoelectrons. Ultimately the mercury ions are reduced by photoelectrons to atoms that agglomerate into droplets of metallic mercury reponsible for glass darkening. A mercury discharge provides not only(i) mercury ions and (excited) atoms entering the glass and(ii) photons, creating a photoelectric field in the glass. The discharge also provides (iii) low energy electrons flooding the glass. The latter greatly enhance the strength of the photoelectric field in the glass by recombination with photoholes in the glass near the surface. As regards the effect on the darkening of the glass composition, not only the overall composition is considered (e.g., conductivity, molar volume, shear modulus), but also superficial changes in the composition.It is well known that a low pressure mercury discharge operated in a soda lime glass envelope will gradually darken the envelope unless the latter is coated with a fluorescent powder or otherwise protected (1-4). This darkening is associated with the intense bombardment of the glass by photons, mercury ions and electrons, and the associated recombination energy of the ions (10.4 eV). For a 1 in. fluorescent tube geometry the photon flux is about 1(} n photons of 4.9 eV and 1'01B photons of 6.7 eV per cm 2 per sec. For the ions and electrons the flux is about 1014 (5). An interpretation of long standing for the darkening, that is well known from the patent literature [see examples in Ref. (2)], is as follows. Sodium ions from the glass migrate to the inner surfaoe of the envelope. Here they are neutralized by the incoming electrons from the discharge and the resulting sodium atoms serve as nuclei for the condensation of minute droplets of mercury on the surface of the glass. These give the glass its dark appearance. This view is tempting, since it is well known that the inner surface of the envelope acquires a negative potential of about 8V with respect to the discharge. The existence of this potential difference can easily be demonstrated by painting a conductive coating on the outer wall of the envelope and connecting it via an electrometer with one of the electrodes of an a-c operated ...

The dependency of the efficacy of an alternating-current surface-discharge plasma-display panel (PDP) on the gas pressure was investigated for several Xe-Ne gas mixtures. Also, the sustain voltage was varied. Monochrome 4-in. test panels, with a design which resembles the one used in mainstream commercial products, were used. The experimental panel efficacy and emission characteristics were compared to the results of a numerical discharge model. A strong increase in the efficacy for increasing voltage was found in high-gas-pressure mixtures with a high Xe concentration. An increase in the electron-heating efficiency and of the Xe-excitation efficiency contribute, about equally, to the increase in efficacy. The increase in the Xe-excitation efficiency is due to an increase in the excitation in the lower Xe levels induced by a lowering of the electron temperature. The contribution of the increasing Xe-dimer radiation fraction to the efficacy improvement is relatively small. These results imply an efficient panel design comprised of the combination of a high Xe concentration, a high gas pressure, and a high sustain voltage. A high luminance and a high efficacy are concurrent for such a design. A 4-in. test panel containing a mixture of 13.5% Xe in Ne at 800 hPa has been realized, demonstrating a white luminance of 2600 cd/m 2 and an efficacy of 3.1 lm/W for continuous operation at 50 kHz and 230 V.