PbO films were prepared by the oxidation of Pb films in oxygen and the photoconductive properties of these oxide films were investigated. The results are as follows:
(1) Pb films prepared by vacuum evaporation were almost completely oxidized by heatig for ten minutes at 450°C in oxygen. It was ascertained by X-ray analysis and conductivity measurement.
(2) The crystal structure of PbO was α-type and not β-type. Other types of lead oxides, i. e. , Pb₂O₃, Pb₃O₄, and PbO₂ were not contained in the prepared PbO.
(3) The relation between the photocurrent, J and the intensity of light, I is given by the following equation: J=k I_n, where k is proportional constant independent on the intensity of light.
The values of n varied from 1 to 0.5 with increasing intenslty of light, i. e., n is approximately equal to 1 at 20~150 luxes, 0.68~0. 75 at 250~8,000 luxes, and 0.5 at 8,000～30,000 luxes. Therefore, in the former, the recombination process is given as the kinetics of monomolecular reaction, while in the latter, the process is given as the kinetics of bimolecular reaction.
(4) Two peaks were observed in the photocurrent curve and one of them exists at 425 mμ and the other at 530mμ. The results coincide with the results of optical absorption.

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Electron spin resonance of acceptors due to a substitutional Li or an adsorbed aromatic compound molecule and the resonance of certain donors previously reported at g=1.96 were examined using polycrystalline samples of ZnO series oxides, e. g. , ZnO-Li₂O, ZnO-Ar (Ar=aromatic compound), and ZnO-Li₂O-Ar. The analysis of the resonance spectra gave for the donor due to an interstitial zinc or an oxygen vacancy g=1.958, for the acceptor due to an adsorbed oxygen molecule ion g=2.0053 or g=2.011, for the acceptor due to an adsorbed quinone or naphthoquinone molecule g=2.003. The resonance signals for the Li acceptor were not detected.

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Exposure before charging process in zinc oxide Electrophotography is known to increase the amount of corona discharge required for the surface potential saturation. The effect of the exposure on the surface potential rise up curves is found especially marked in the zinc oxide layer containing a certain kind of resin binder such as alkyd resin.
This effect is attributed to the presence of some active groups in the resin, which is adsorbed on the zinc oxide micro-crystal interface.
It is found some difference between the effct of UV and visible light absorption, and this is attributed to the localization of immobile positive holes which have been created in the layer by llght absorption. The Absorption of UV light creates positive hole electron pairs only near the surface of the layer, owing to its high absorption coefficient and this effect of holes is eliminated by intense corona discharge. Whereas, in the case of absorption in the dye sensitized region, the positive holes are produced almost uniformly throughout the layer, and these exhibit an effect lowering the surface, potential and decreasing the effective thickness of the layer, by forming positive volume charge in the layer. This volume charge is not eliminated by corona discharge and it requires some interval to be extinguished, from a few seconds to several days, depending on both the kind of binder resin and the temperature. The positive volume charge in the layer, also, has an effect lowering the photographic contrast and equalizing the surface potential.

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Some previous studies on persistent intemal polarization seem to suggust that the larger amount of the polarization may be obtained as the higher voltage is applied. According to our experiments, however, the higher voltage brought often the decrease in PIP, in practical atmosphere. Also, the observed potential of the polarization varied in the polarity during the decay.
Another experiments were also done. A PIP cell of a sandwich type consisting of transparent electrode, insulating film, phosphor layer and metal electrode was used. The charge amount and the polarity of the phosphor layer (PIP) and the insulating film were measured. The results showed that PIP began to decrease at a certain of high voltage and the charge on the insulator began to increase at the same voltage. This seems to suggust that the application of the higher voltage may make the charge distribution in the wide region of both phosphor layer and insulator.

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The Walt Disney Production first introduced xerography in producing animation films.
In October, 1963, the Toei Animatlon Studio adopted xerography for the time in Japan. They have already obtained good results in the production of animatio films with the use of xerography.
The present writer had a privilege that he took part in planning the introduction of xerography for the Toei Studio and reconstructing the studio for it, and he would like to outline here some informations on xerography.

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