A novel class of electron-acceptive compomds, unsymmetrically substituted diphenoquinones with two kinds of alkyl groups, was designed and synthesized for electron transport materials. The unsymmetrical substitution produced extraordinarily high solubility in organic solvents and dispersibility in a wide range of polymers. In the polymeric dispersion of 3,5-dimethyl-3',5'-di-tert-butyl-4,4'-diphenoquinone (DMDB), a representative member of these compounds, high electron mobilities over 10^-6 cm²/Vs were obtained, which are comparable to those of the hole transport materials in practical use.Its electron transport properties were characterized according to the Schein's analytical technique. The results indicated that the electron mobility in the limit of zero-field is consistent with the non-adiabatic small-polaron hopping mechanism. It was also found that electrons can be photo-injected from phthalocyanine pigments into the DMDB-based electron transport layer, suggesting the promising application to xerographic photoreceptors that can work in the positive charging mode.

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Amorphous polymeric films with 3, 5-dimethyl-3', 5'-di-tert-butyl-4, 4'-diphenoquinone (DMDB9 and N, N, N', N'-tetra(m-tolyl)-m-phenylenediamine (PDA)as electron- and hole-transporting dopants, respectively, were found to exhibit ambipolar transport characteristics. The dopants functioned independently as hopping sites for electrons and holes without electronic interactions. In addition, it was found that both electrons and holes can be effectively photo-injected from titanylphthalocyanine (TiOPc) into these films. On the basis of the ambipolar carrier transport and injection, a new type of single-1ayered xerographic photoreceptors has been developed which can work equally in both positive and negative charging modes.

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In this report a new model for triboelectric charging of toner with charge control agents (CCA) is proposed and the model is estimated by computer chemistry, using the molecular orbital method (MO) and the molecular mechanics method (MM)developed by us. This “ Water dissociation model ” is composed of three processes which are: 1) the orientation of the CCA molecule on the toner surface ; 2) the construction of a water bridge from the hydrophilic portion of the CCA to the carrier surface ; and 3) the polarization and subsequent dissociation of an end water molecule at the CCA side of the water bridge. It has been shown that the triboelectric charge of several toners containing synthesized CCA are intimately related to the calculated charge on the water molecule effected by the CCA. In addition, the simulated water bridge using MO and MM was constructed for the CCA and some water molecules. This model and calculation elucidates the mechanistic role of CCA in toner charging.

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In the reversal development process, development and cleaning can be performed simultaneously by the same development unit. The residual toner particles on the nonexposed area of the photoreceptor are attracted to the development roller by an electrostatic force and return into the development unit, while the toner particles on the development roller are attracted to the exposed area simultaneously. This simultaneous development and cleaning is due to the phenomenon that residual toner particles are charged to the same polarity as that of development toner in the reversal development process during charging of the photoreceptor. A compact and waste-toner-free cleanerless laser printer, based on this idea, was put into practical use. In order to realize still simpler printing process, the authors studied the feasibility to apply a contact-type monocomponent nonmagnetic development using a soft and conductive development roller. It is assumed that undesirable memory images, caused by residual toner, can be diminished by this development system, because the development roller as an developing electrode is so close to the photoconductive surface that the development and cleaning electric field becomes very high. In this paper, a high cleaning efficiency of this development system is shown, based on an analytical model, in which effects of residual toner in both the charging and exposure processes are taken into consideration. Residual toner on the photoconductive surface up to an amount as high as 0.55 × 10^-2 (kgm²) can be removed perfectly in this process.

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A contact charging method has the advantages compared to a corona charging method. Applied voltage is lower and ozone generation is negligible. However, it did not work well because of an uneven charge distribution and the change of charging-characteristic in environmental conditions.
These problems were solved by a newly developed roller charging method. In this method, a conductive elastic roller covered with a thin resistive layer is applied with an improved AC and DC voltage.
The LBP-LX uses this roller charging system in the image forming process.

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