This paper deals with an electrophotographic process which utilizes a photosensitive element consisting of a conductive layer, a photoconductive layer and an insulating layer. The latent image formation mechanism is based on the effective capacitance difference between light-exposed part and dark part of the photosensitive element. The methods, method 1 and 2, are investigated. The steps in forming latent image in method 1 are : 1) uniform charging and 2) image exposure. These in method 2 are : 1) simultaneous corona charging and image exposure and 2) blanket exposure. The latent image is then developed by magnetic brush. As a result, characterestics of latent image formation and that of development were clarified. High quality printing was obtained by each method. Moreover, combining these two methods, the new posi-overlay process which can print out composite image of positive and negative image was developed.

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Using the same 3 toner samples, B, C, and D, as used in the previous report, a detailed quantitative analysis was made concerning the “potential decay” experiment. In process of the so planned experiment, an unexpected phenomenon, i. e., field affected triboelectric charge transfer between PET film and the toner samples, was found.
According to the detailed analysis of the potential decay experiment, even though it was intended to reduce the above mentioned charging effect to minimum, its contribution to the potential decay is still quite larger than that of the effect of the charged perticle migration and deposition onto the PET film in most cases.
Further, an additional series of experiments, i. e., static or quasi-static toner deposition onto the PET film by voltage application and toner charge to mass ratio, Q/M, measurement, was made in order to verify at least mixed presence of positively charged and negatively charged particles in the toner layer.
The results were just as anticipated, showing that all 3 samples exhibited more or less both positive and negative particles, and measured Q/M values for toner B range from 4 to 20 μC/g.

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In the development of electrophotographic system named “FF SYSTEM”, the electric field of latent image has been analysed and the contribution of the principal parameter to the system has been investigated, in order to fix the parameters of the photoconductor.
And it is confirmed that the calculated value on the model agrees well with the experimental result by using solid area response model.
The model is useful for the design of system process control for the image quality stability.

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