Equipment that can measure a triboelectric charge between powder and beads was developed, using a blow off Faraday Cage that has a unique structure. The triboelectro charge between toner particles and iron beads for electrophotographic two-component developer can be measured very quickly and automatically by using this equipment.
At a blow pressure higher than 0.5 kg/cm², the corrected charge that was obtained after deducting the tribo-charge between toner (or carrier) and Faraday Cage from the measured charge shows very small variation with blow condition, e.g. blow gas pressure, nozzle orifice, etc. Therefore, these values can be considered to be representative values to indicate the triboelectric characteristics between toner and carrier.
From the analysis of toner size effects on measured charge, it was deduced that the integrated number of toner-carrier contacts through the blow off measurement decided the charge magnitude. Other factors that influence the charge magnitude, e.g. toner concentration, agitation and storage, etc, also support this consideration.
Although the toner-carrier contact and separation during blow off operation seems to be a very intricate phenomenon, similar activities are occuring during the development process. So, the charge obtained by the blow off method is nearly equal to the one obtained by other methods concerned with development and is closely related to the development characteristics.
Therefore, from practical point of view, this equipment is very useful to evaluate development characteristics, material selection and triboelectric charge control for electrophotographic powder developer.

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If it is possible to prepare a series of standard carriers which differ in tribo-electric property in a certain orderly manner, one can expect to determine tribo-electric coodinates (positions in tribo-electric series) of fine particles compared with such carriers by “blow-off” method.
Such a series of standard carriers have been obtained by coating natural sand with mixtures of tribo-electrically positive ethyl cellulose and negative nitro cellulose in varying mixing ratios.
Several inorganic and organic compounds were subjected to TEC measurements by using this series of standard carriers to successively determine their TEC values.

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Fine aqueous mists are applied to the development of electrostatic latent image. The mist development needs no fixing.
Mists generated by ultrasonic wave were used to develop latent images on ZnO sensor or polyester film, and mist image properties were analyzed. The image density quickly saturated on ZnO sensor probably due to the image charge leakage during development. The density was also dependent on the surface tension of the mist since the mist aggregated on a poorly wettable surface. The image density D on polyester film is proportional to both the surface potential and developing time, but independent of the thickness in range 25-250 μm. The developing velocity dD/dt with charged mist was twice as fast as with uncharged mist.
Considering the various experimental facts, mist development may be characterized by the following two features; a relatively large developing velocity and a capability of developing a low charge density image, which may be attributed to the small charge amount on individual mist droplet and to the low viscous drag of carrier (air).

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The imaging mechanisms of charging development process with ZnO-Mylar photoreceptor has been studied. It has been shown that a conductive magnetic toner (CMT) acting as a filings electrode deposits on dark portions of the photoreceptor, and the deposited toners have the same polarity as the applied potential; further, the total positive potentials (or charges) on the developed portions have two components, toner layer potentials (or charges) and photoreceptor surface potentials (or charges). It has been demonstrated that the ratio of two components changes with exposure to light. The photographic characteristics has been measured. The results of these measurements indicate that the photographic sensitivity corresponding to ASA at wavelength of 581 nm is 0.2 and gamma is about 10.

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