The anomalous corona discharge current to zinc oxide and the charging characteristics in various gases is reported.
Experiments were carried out for ZnO-paper, ZnO-layer on a metal plate and Se-plate.
Following results were obtained.
The anomalous current is remarkable in negative corona discharge to ZnO-paper in the dark.
As T. Elder pointed out, it may be inferred that irregulality of surface charge density causes the anomalous corona current.
Corona discharge current, surface potential and photosensitivity were measured in the atomosphere of various gases for ZnO-paper.
High photosensitivity and well-fitted charging character were observed in the oxygen atmosphere.

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Electrolytic development process of the ZnO-resin layer in the aqueous solution of 2, 3, 5-triphenyltetrazolium chloride (T. TC.) as the developing soln. was studied. Experiments were conducted on such electrolytic conditions as the electrodeposition efficiency, the image density vs quantity of deposited 1, 3, 5-tripheny formazan dye, the log exposure vs electrolytic current, polarographic analysis of the developing soln., and on such developing conditions as the temperature of developing soln., the elapsed time after exposure, the applied voltage, the developer concentration, the developing time, and moreover on such characteristics of the layer as the effect of ball milling time compared to the photocurrent measured by a surface-type cell. The mechanism of the electrolytic system is discussed in relation to the results of the polarographic study. Four quadrant relations of the whole conditions are proposed.
The conclusions;
1) The best conditions for a standard development are; the temperature of developing soln. 20°C, the applied voltage 10V., the T. T. C. concentration 1%, and the developing time 10sec.
2) A good agreement is found between the electrolytic characteristics of the ZnO resin layer and the photocurrent characteristics of the layer measured by surface-type cell. This indicates that the electrodynamic property of the layer will greatly influence the characteristics of the system.
3) The mechanism of the electrolytic system could be explained from the results of the polarographic analysis and from the consideration of the equivalent circuit diagram for the system.

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The surface photovoltage of zinc oxide fine powder was measured by the Kelvin method. Spectral response measurements show that the photovoltage is produced not only by wavelength light from 300 to 400mμ, but also by longer wavelength light from 500 to 800mμ. In the short wavelength light, the decay of photovoltage on turning off the light is rapid at high light lntensity, but slow at low light intensity. There are also the similar phenomenon with long wavelength light, though the increasing curve is different from that of short wavelength exposure.
During exposure with short wavelength, the photovoltage increases by replacing the ambient air with an inert nitrogen, and, in long wavelength, no change in photovoltage is observed by the same treatment. It may be considered that these behaviors occur from the difference of extinction coefficient of zinc oxide crystal for different wavelength lights.
The photovoltage is proportional to the logarithm of the incident light intensity in both wave-length ranges.
It is suggested therefore that the change in surface charge is less sensitive to the change of light intensity.

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This study aims to apply the titanium oxide as an electrophotographic material. At first the physical properties of solid state TiO₂ are described; these are the dark conductivity, the photoconductivity and the dielectric property. Afterwards we investigated for the application of TiO₂ to the electrophotograhic fax paper.
The conductivity of TiO₂ is 10^-12~10^-14Ω^-1cm^-1 at room temperature. The photoconductivity observed is 10²~10³ times as large as the dark current at the light of 1000 L/cm². We measured the wave length dependence of photoconductivity. The photocurrent of TiO₂ single crystals shows a maximum at the wave length 4280Å (2.88ev), but the maximum peak of TiO₂ powder is found at the wave length 4000Å (3.01eV). The dielectric constant of TiO₂ single crystal is C//173, C⊥89, and that of powder is 114. The dielectric constant has an importance for the electro-static potential of the electrofax process. We have discovered that the anti-humidity of TiO₂ electrofax paper can be improved by adding SrTiO₃ (ε≈1000 at R.T.) of 5~7 wt%.
From this study the following can be said: We have to improve the sensitivity of photoconduction of TiO₂ for the electrographical application, but even at the present, TiO₂ can be applied to the electrophotographic“scribing”technique.

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