The influence of electron-affinitive molecules (EAM) adsorbed on zinc oxide upon static electrification of electrophotographic layers (ZnO-Resin system) by corona discharge was studied. When EAM (maleic anhydride, phthalic anhydride, iodine or p-chloranil) was adsorbed, the initial surface potential (saturated surface charge in darkness) was depressed. Also photosensitivity, i. e., the ratio of dark to light decay rates was increased, though both the decay rates themselves decreased. These results were discussed comparing them with the results obtained from measurement of dark-and photo-conduction reported in the previous paper⁽¹⁾ . It was found that co-adsorption of EAM and an optical sensitizer (Rose Bengal) resulted in a quite effective sensitization in accord with the similar effect (hypersensitization effect) observed in photoconduction.

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The Electrophotography has made possible a photographic-type direct recorder.
The recording paper is daylight loaded, and the completely processed, permanent record is ready for use on leaving the recorder. There is no deterioration of the recording from brightsunlight.
Copies can be made directly with a conventional diazocopying machine.
A schematic diagram of general purpose electrograph is shown in Fig. 1
The device is constructed with a super-high pressure mercury lamp and a mirror-type galvanometer off high-sensitivity so that it gives the writing rate of about 45 meters per second. (700 c/s, ±10mm)
A trial produced a directing recorder with an electro-photographic paper which permits immediate trace up to high frequency to which an ink-writing or a heat-styles recorder has never reached and in addition, it can record the exposure up to high radioactive intensties.

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Sensitization of polyvinylcarbazole with compounds having electron accepting properties has been investigated. Light decay characteristics both for negative and positive charge and the photocurrent as well as photovoltaic effect were studied with monochromatized light. Acceptors used are I-VI (cf. formulae).
Polymer film is prepared on a copper plate as explalned in Fig. 1. Spectral intensity distribution of the xenon light source is shown in Fig. 2. Experimental arrangement for the decay experiment is shown in Fig. 3. Photocurrent through the film is measured with a cell like Fig. 4
For decay experiment, slit width was 20mμ. Decay constant was calculated by an equation
V=V_0e^-αt1/2 (cf. preceeding paper), and corrected for the light intensities.
As show in Fig. 5, decay constant of polyvinylcarbazole is very large when charged positive, having some sensitivity even in visible region where almost no light absorption is observed (Fig. 6) . The result suggests that the major carrier in polyvinylcarbazole is hole.
Spectral response of the photocurrennt is shown in Fig. 7. Photocurrent obtained when positive electrode is illuminated being larger, the result suggests again that hole is the dominant carrier. Spectral response of the photovoltaic effect is shown in Fig. 8. As the sign of the current is taken as explained in the figure, the result is understood by assuming higher mobility of positive carrier.
Decay constant of polyvinylcarbazole sensitized with varying amount of chloranil is shown in Fig. 9. From this result the amount of various acceptors added to polylvinylcarbazole as sensitizer is settled to 1％. Spectral response of the decay constant with different acceptors is shown in Fig. 10. When charged negative, 3-7 fold increase in α is observed by sensitization, showing considerable sensitivity also in visible region. When charged positive, the sensitivity of polyvinylcarbazole being very large, the sensitization is restricted in 1-2 fold increase.
Spectral response of photocurrent of polyvinylcarbazole with compound I (TCNQ) is shown in Fig. 11. The current is larger when positive electrode is exposed. Considerable response in visible region is explained by charge transfer band of polyvinylcarbazole TCNQ complex (Fig. 12). Photovoltaic effect observed with the same system is shown in Fig. 13.
All these result are reasonably explained by assuming that the major carrier of sensitized polyvinylcarbazole is hole.

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The transfer phenomenon of electrostatic latent images on electrophotography was investigated both expermentarily and theoretically.
The experiment was performed following the process shown by H. Bogdonoff and C. F. Carlson in the Japanese patent. Two sorts of electrofax paper were mainly used as original Plate. Successful results were obtained when the receiving surafaces were charged previously at the same polarity as the original plates and proper bias potentials were imposed. The transfer characteristics were obtaind by measuring the receiving surface potentials after being printed in contact with the original plates of various initial charging potentials.
These results were analysed and transfer mechanisms were considered.
It was clarified that in many cases the latent images on the original plates play the role that a grid does for the dissipation of charges on the receiving surfaces.

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In order to improve the visible response in the Electrofax system, dye-sensitization is available and rosebengal is one of the most excellent sensitizers. Rosebengal is not a good photoconductor but it induces a remarkable improvement in the photoresponse On the other hand, malachitegreen does not sensitize zinc oxide though it is a good photoconductor. This paper describes the mechanism of dye-sensitization process in the Electrofax system.
The photocurrents were measured by single excitation and double excitation with ultraviolet and/or visible radiations in rosebengal dye-sensitized zinc oxide and in pinaflavol dye-sensitized zinc oxide. From these results the increase in the photocurrents was estimated to correspond to the ultraviolet or the visible radiation under double excitation. From these experimental data we may say that exciton was produced in dye by absorbing lights, which excited trapped electrons neaf the surface of zinc oxide particles up to the conduction band and then photoconduction was increased. This conclusion supports A. Terenin's proposal on the dye sensitization of photoconduction.

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