Mechanism of liquid development of electrophotography was studied by use of a comparatively simple system wherein polyester film with copper evaporated on the back side was used as Electrofax layer and two kinds of dispersions as developers; one was a dispersion of Aerosol OT and carbon black in n-Hexane (A-type) and the other a dispersion of methacrylate polymer and carbon black in n-Hexane (M-type).
From this study it was suggested that liquid development is mainly carried out through electrophoresis and that other factors, such as dielectric polarization and wetting, should be taken into consideration when the mechanism of liquid development is discussed.
Furthermore, development characteristics of weakly negative toner and space charge of toner and particle size of toner were investigated.

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We have studied new-type of sensitizing dyestuffs for PVK. We synthesized 12 kinds of 3, 3-dicarbazolylphenylmethane dyes and evaluated the properties of dyes such as visible absorption spectra, fastness to light and electrophotographic properties. Thus we confirmed that these dyes have many advantages as a sensitizer for PVK in comparison with other type of dye. Theyl satisfied the following conditions required for practically applicable sensitizer.
(1) high sensitizing effect
(2) faint coloring
(3) panchromatic spectral characteristic

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The photochemical sensitizing treatments of PVK were studied with respect to the solution system. The standard solution contained carbon tetrabromide, N-vinylcarbazole, PVK and benzene. To account for the some behaviors of the photochemical reaction, we observed IR spectra, elementary analysis, viscosity, gel-permiation chromatogram and gas chromatogram. And also, we had tried the investigation of blue dye formation process using N-vinylcarbazole substituents and PVK derivatives. We could confirm the crosslinkage of PVK, carbazole formation from N-vinylcarbazole and presumed the formation of blue dye component similar to 3, 3'-carbazolylmethane dye. We could observe the direct interaction between blue dye formation and NVK in the standard solution.

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