The mechanism of the Canon Toner Projection Development is studied. The technical features of TPD comprise two processes; one is to smoothly coast a toner applicating sleeve which involves permanent magnets in it with electrically insulative and magnetic toner, and the other is to oppose the sleeve to the image bearing member retaining the gap between them, which is larger than the thickness of the toner layer and to accomplish the development. It is the characteristic of TPD that toner goes back and forth between the toner applicator and the image bearing member both in the image areas and in the non-image areas under the influence of the external alternating electric field.
The model of the development is made with some simplifications considereing the following forces which act on the toner particles; the first is electric forces which originate from both the image bearing member and the alternating electric field, the second is image force which originates from the tridoelectric charge of the toner layer, and the last is magnetic force.
The numerical calculation of the V-D characteristic well agrees with the experimental results, which confirms the validity of the model. According to this model, V-D characteristics of TPD depend on mainly the image force of the toner charge.

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Field-induced CT fluorescence quenching has been observed in a poly-N-vinylcarbazole (PVCz) film doped with tetracyanobenzene (4CNB), which exhibits a large sensitized photocurrent in the corresponding CT absorption region. The CT fluorescence quenching has been found to be attributable to carrier photogeneration due to the “field-assisted thermal dissociation” of an ion pair which is produced from higher excited CT state as a precursor. Analysis in the framework of the Onsager's model for the dissociation process of an ion pair satisfactorily explains the experimental data of field-dependence and temperature-dependence of the fluorescence quenching by electric field. Combining with previously proposed mechanism of extrinsic carrier photogeneration in the exciplex systems, more general mechanism has been presented for the extrinsic carrier photogeneraion in a solid state of the excited donor-acceptor system.

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A jar-mill experiment was carried out using developers of 100 μm steel powder mixed with 12 μm toner (Sample 1) and 6 μm toner (Sample 2). At milling time ∼400 h, KYOKUBAN (Parallel-Electrode Device) detected appreciable amount of wrong-sign toner in only Sample 1. Toner-impaction analysis revealed that the weight and coverage of impacted toner on carrier surface of Sample 1 were smaller than those of Sample 2. In an additional jarmill experiment using 12/μm pigmentless “toner”, no wrong-sign “toner” was observed. These experimental facts led to an assumption that free carbon black (or fine toner rich in carbon black) is involved in wrong-sign toner generation. A simulation technique called KYOKUBAN Spectrum which demonstrates quantitatively the effect of free carbon black on triboelectric properties of developer was applied to the sample developers, and the assumption was shown to be consistent with the results of jar-mill experiments.

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