A new red phosphor, SrTiO3:Pr3+, was developed for vacuum fluorescent displays (VFDs) and field emission displays (FEDs). It was discovered that the addition of Al is essential to achieve a high luminous efficiency of low-voltage cathodoluminescence and photoluminescence. The mechanism underlying the improvement of the luminous efficiency by the addition of Al is discussed. With the addition of 17 mol% Al, luminance of 800 cd/m2 was obtained at the anode voltage of 50 V. Powder X-ray diffraction and Auger analysis showed that the Al ions react with the Sr ions to form SrAl12O19.

The degradation mechanism for the low voltage cathodoluminescence of normalZnS:normalZn and false(Zn0.22Cd0.78false)S:normalAg,normalCl phosphors in vacuum fluorescent displays has been investigated by mass spectrometer, field emission scanning electron microscope observation, Auger electron spectroscopy, and x‐ray photoelectron spectroscopy. It has been found that the decomposition and evaporation of phosphors take place during electron excitation. This causes the deterioration of cathode filaments as well as the decrease in luminous efficiency of the phosphors.

The ZnGa204 phosphor has been investigated for its application to vacuum fluorescent displays (VFDs) utilizing lowvoltage cathodoluminescence. It is expected that this oxide phosphor does not cause damage to filaments in VFD's, while it is a serious problem for conventional sulfide phosphors. This phosphor shows blue luminescence with a spectral peak at 470 nm and a chromaticity at X = 0.170 and Y = 0.130. A luminous efficiency of 0.7 lm/W has been obtalned, when the VFD with this phosphor is operated at 30 V dc. The results of high-temperature operating life test have proven the excellent stability of VFDs utilizing this phosphor.Presently, sulfide phosphors are extensively used for vacuum fluorescent displays (VFDs). However, as previously discussed by the authors (1), sulfide phosphors emit sulfide gases and decompose to scatter phosphor material during electron excitation. This causes not only the decrease of luminous efficiency of the phosphors but also the deterioration of cathode filament, which are serious problems in multicolor VFDs.An attempt has been made to study the ZnGa204 powder phosphor to be used as the alternative of blue cathodoluminescent phosphor of ZnS:C1 phosphor. The ZnGa204 phosphor is a compound oxide of ZnO and Ga20~, crystallizing in the spinel structure, and its optical bandgap is about 4.4 eV. ZnGa204 shows emission from green to red when it is doped with Cr and Mn, and also shows blue emission even without being doped with impurity. It is well known that the phosphor is excited by electronbeams followed by energy transfer to the luminescent center to emit light. Therefore, the essential requirements for low-voltage cathodoluminescent (LCL) phosphors are low resistance and low threshold voltage, as well as excellent crystallinity. In view of these requirements, the ZnGa204 phosphor, which is inherently low in conductivity, was added with conductive materials. This paper mainly discusses the luminous characteristics of the phosphor which was applied to the VFD. REFERENCE

Influences of gases on the field emission were measured using the specimens of Spindt-type Mo field emitter array. Gases were introduced into a vacuum chamber where the specimens were driven with pulse and dc voltages to emit electrons. In case of pulse drive, effects of N2 , H2 , Ar, or CO2 on emitter arrays could hardly be observed until the vacuum level reduced to 5×10−6 Torr. When the vacuum level was recovered to the background level, emission showed the recovery to be almost the same value as that before gas introduction. When pulse driven, a small amount of H2 gas reduced the work function of the emitter surface and increase the emission characteristics of emission array. In case of dc drive, on the other hand, emission began decreasing at 10−7 Torr. The introduction of SO2 led to the decrease of emission to ∼70% of the initial value at 5×10−6 Torr because of the contamination of emitter tips caused by SO2 when pulse driven. It was also clarified that CH4 , H2 , and CO adsorbed to emitters to reduce the work function of emitter tips. Particularly with CH4 , emission was doubled or more the initial value at 5×10−5 Torr.

These epidemiologic results suggest that heavy cumulative alcohol intake and prior exposure to HBV infection are risk factors for the development of HCC in patients with HBs Ag- and anti-HCV-negative alcoholic cirrhosis.