The discharge properties and chemical surface stability of CeO2 containing Sr (CeSrO) as the candidate for high-γ protective layer of noble plasma display panels (PDPs) are characterized. CeSrO films have superior chemical stability, because of the decrease in reactiveness on surface due to their fluorite structure. The discharge voltage is 50 V lower than that of MgO films for a pure discharge gas of Ne/Xe = 85/15 at 60 kPa. However the topmost surface, monolayer, of the CeSrO film relevant to the discharge property is hardly recovered from the damage by CO2 impurity in discharge gas. We can expect that by pumping down to a sufficiently low CO2 partial pressure (lower than 1 10-3 Pa), PDP panels with very high efficiency are realized with CeSrO protective layer.

We studied the application of precursor solutions that can be fired into oxides to form a protective layer for AC-type Plasma Display Panel (AC-PDP). Our study of alkoxide and metallic soap as MgO precursors revealed that the crystallinity of MgO films depends on the starting substance. Since the electric discharge characteristics of a panel and the lamination effect of the protective layer depend on precursors, it was confirmed that binders having higher crystallinity provide better characteristics. Our study revealed that a compound-oxide film has high crystallinity. The application of a Ba0.6Sr0.4Gd2O4 formation solution to a binder and the application of a Sr0.6Mg0.4Gd2O4 formation solution to a protective layer both are seemed promising We also found that a double-layer film, made by forming a protective layer of fine MgO powder and a Ba0.6Sr0.4Gd2O4 binder, on top of a protective layer made of fine MgO powder and a MgO binder, provides a luminous efficiency 5.3 times higher than that of sputtered MgO film which is one of candidates for the large panel, and the conventional electron beam evaporation is not suitable for the large panel. We further found that a triple-layer protective film made by forming a thin film of Sr0.6Mg0.4Gd2O4 provides low voltages of 1 V in firing voltage (Vf) and 35 V in sustaining voltage (Vs) compared to the double-layer film and provides a luminous efficiency 5.5 times higher than that of sputtered MgO film. A life test revealed the triple-layer film in particular providing a useful life of more than 10,000 hours. From these findings, we concluded that the compound-oxides which is composed of alkaline-earth-metal and rare-earth-element could be applied effectively to a protective layer for AC-PDP.

Protective layers in AC plasma display panels (PDP) are usually formed by vacuum vapor deposition or sputtering. It is important to study the protective MgO layer by means of screen-printing for fabricating a large size PDP and reducing its cost. With the objectives of enlarging the panel size and reducing cost, we studied the fabrication of the protective MgO layer by means of screen-printing. In this study, we succeeded in lowering the drive voltage by using a MgO powder prepared by vapor phase oxidation instead of conventional decomposition of the magnesium salt. Further, by adding a MgO liquid binder, we attained a good luminous efficiency twice as high as that attained with a sputtered protective layer and lowered the drive voltage. When this protective layer was combined with He-Xe gas enclosure, the half-life of luminance was 5,000 hours. With Ne-Xe gas, the luminance deteriorated no more than 40% after 5,000 hours. A screen-printed protective MgO layer containing no MgO liquid binder showed a short half-life of 800 hours even with the use of Ne-Xe gas. In this case, the discharge voltage changed greatly and some cells did not discharge. It is concluded that the combination of an ultrafine MgO powder prepared by vapor phase oxidation and a MgO liquid binder can clear the way for making AC PDPs with a long lifetime, high efficiency, and low voltage a practical reality.