A novel near-infrared sensitive photoreceptor incorporating titanium phthalocyanine with a new polymorph named Y-fom has been developed. Y-form titanium phthalocyanine compounds are metastable and have the deepest red-shifted absorption peak among other polymorphs. The dobuble-layered photoreceptor using Y-form titanium phthalocyanine exhibited very high sensitivity in the wide spectral regian from 600 nm to 850 nm (E_1/2 = 1.0 erg/cm²), low dark decay and excellent cyclic stability over 100,000 prints. In particular, the photoreceptor showd very high quantum efficiency which is over 0.9 in the high electric field region and little dependence of the photosensitivity on the ionization potential (Ip) of carrier transport materials (CTM). It was suggested that these characteristics were caused by the high carrier generation efficiency and the high μτ product.

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The author have investigated to apply a plasma image bar using a gas discharge emission as a fourth light source for an electro-photographic printer.
There are several demands to realize in the light source, such as finer resolution, quicker response and better power matching between light intensity and sensitivety of photoconductor.
A negative glow discharge of Ne and Ar mixture gas has good atributes enough to satisfy these demands, and has been most stable efficient glow in all discharge conditions. So we have applied following ideas due to effective use this glow emission as a light source, such as: (1)Applying the DC discharge cell, (2)Setting up auxiliary cell, (3)Applying the matrix driving method, and etc.
As a result of using that, we have created a prototype DC plasma image bar with a resolution of 300 DPI and optical writing speed of 8 PPM on A4-sheet, and its printing has been succeeded.

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This paper theoretically analyses the magnetic force acting on the magnetic toner from the magnetic latent image. Arctangent approximation is employed to express the function of the magnetic transition region. The magnetic force is calculated using the practical characteristics of the recording medium and the toner. The calculated values agreed with the experimental facts.
Physical meanings of the magnetic force are also considered. It is found that the magnetic force attracts the magnetic toner to the assumed magnetic charge center(0, y₀, -a)(a: magnetic transition constant), it is inversely proportional to the third power of the distance from the magnetic charge center, and the magnetic force is substantially as large as the electrostatic force acting on the toner in electrophotography.

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Triboelectric-charging and the two-component development system with insulative carrier have been studied by varying the toner surface-area median size (d₅₀) from 6.8 to 13.5 μm and the carrier surface-area median size (D₅₀) from 43 to 106 μm.
It has been found that the development efficiency is determined by surface-charge density (q/s_t) of the toner particles independent of the toner size (d₅₀), rather than by the charge-to-mass ratio (q/m) as formulated by Schein and by the other workers, and that triboelectric-charging is should more likely be described by q/s_t as a function of surface area ratio of toner to carrier (ns_t/s_c), as suggested by Kurita, rather than by q/m as a function of mixing-ratio (X) of toner to carrier.
The developed toner-mass per unit area on a photoreceptor (M/A) has been described by a formula, M/A∝[α-β(q/s_t)] (where α and β are numerical constants), in the experimental range of q/s_t from 3.5 to 7.0 nC/cm². The triboelectric-charging has been discussed from a view of phenomena entirely concerned with the surface of toner and insulative carrier particles.

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