Cyclodextrin system having some tosyl groups was evaluated as the charge control agent (CCA). After contacting with iron powder, the styrene/acrylic polymer membrane containing the cyclodextrin compound was generated with a positive charge. The magnitude of the positive charge was affected by the amount of the substituted tosyl group in the cyclodextrin molecule. By mixing iron powder with the toner, a positive charge was generated, therefore, the cyclodextrin compound was estimated as charge control agent. Cyclodextrin compound without tosyl group or catechol having two tosyl group did not show the ability of a charge control agent. The charge increases as the ratio of tosyl groups increases in cyclodextrin molecules up to 55 %, and then begins to decrease as the ratio of tosyl groups increase further. Therefore the results show that the configuration of tosyl groups in the cyclodextrin molecule is responsible for introducing CCA ability.

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The tribocharging behavior of quaternary ammonium salt type CCA was studied by using simple model toners which consisted of polystyrene-acrylic resins and CCA. It was found that (1) it is important that CCA molecules exist as bulky aggregates, (2) a crystalline solid is superior to an amorphous one in the magnitude of tribocharge and charging-rate, and (3) the magnitude of the tribocharge and charging rate depends on the surface conditions of the crysta1. On the basis of these results, it was proposed that the tribocharge is mainly generated at the defects and dislocations on the crystal surface with the aid of its highly incomplete coordination as a driving force for charge-transfer.

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An apparatus for triboelectric charging was designed and constructed. It allowed us to measure charging behavior of sample films dynamically under controlled atmospheres. Using this apparatus, dependences of charging characteristics on humidity and pressure were investigated for some toner components. The charging behavior was greatly dependent on humidity and pressure, and the dependence was a function of the material used.
The effect of film thickness on triboelectric charging was examined at varying humidities for polystyrene. Results revealed that charges penetrated into the bulk of the film, and the bulk charging effect was discussed on the basis of penetration of water molecules into the film.
Ambipolar charging behavior was observed for a polyester film denatured by styrene-acryl resin. It was interpreted by the coexistence of plus and minus charged area in the same film.
In addition, the effect of molecular weight of the sample materials on triboelectric charging is also described.

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A photoreceptor charging method using conductive magnetic brush in contact with the photoconductor surface was studied.
Magnetic powders here employed to form magnetic brush were zinc-copper ferrite, apparent specific resistivities of which were 10⁴, 10⁵, 10⁸ and 10⁹ &Ohm;·cm. Spacing between the magnetic roller and the photoreceptor was varied in the range from 0.7 to 1.3 mm, while the spacing between the ferrite powder thickness regulating doctor blade and the magnetic roller was kept constant at 0.9 mm.
While, for the contact charging using conductive rubber roller, the threshold DC voltage where the photoconductor surface potential begins to rise is reported to be equal to the value predicted from the Paschen's law and also to the threshold AC voltage where the surface potential reaches a plateau, the threshold DC voltage here found was significantly lower than that predicted from the Paschen's law and than the threshold AC voltage. The followings were found to be necessary to attain uniform charging and to avoid charging failure or so-called 'banding' even in the presence of pinhole defects on the photoconductor surface ; apparent specific resistivity of the ferrite powder should be around 10⁸ &Ohm;·cm, AC bias amplitude should exceed certain threshold values determined by the ferrite powder resistivity, and the doctor blade spacing should be larger than the magnetic roller-to-photoreceptor spacing so as to compress the ferrite powder in the latter spacing.
Ferrite powder here used had a low but distinct adsorption surface area and showed a zero-order catalytic activity for ozone decomposition, indicating that the adsorption site of the ferrite surface is completely occupied by ozone molecules, and accordingly, the decomposition reaction is presumably desorption limited reaction. Observed anomalously sharp decrease in ozone concentration accompanying the rotation of the magnetic brush is understandable in this context.

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This study experimentally and theoretically investigates the dependence of charge-to-mass ratio (q/m) of two-component developers on toner concentration. It have been found that there are three types in dependence of q/m on toner concentration. Tribocharging toner concentration dependency is governed by the relative difference of charging site numbers between toners and carrier. To interpret the results, new physical model is proposed and compared with the experiments and other models.

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Using a LED array as an image source, we have constructed a tandem-type electrophotographic color printer composed of4photoconductor drums and4color developers. In this paper, especially, the development of the LED array for color gradation, and the effect due to the tolerance of its light power, mechanical accuracy of dot position, and the thermal effect of LED array are discussed. We also discussed the color registration problems in the tandem-type printer which is easily influenced by the mechanical driving system, the paper transfer system, and the light scan of LED array for 4 photoconductor drums. Furthermore, the pulse control technique of the LED array was developed to obtain the color gradation image, taking the relation between the gradation image and the pulse modulation, the correction for the light power tolerance, and the data transmission speed to the LED into consideration. As a result, the color registration less than 0.1 mm and the gradation image quality more than321evels have been attained.

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