The gamut of color in bi-level digital printers is discussed with a simple color mixing model based on the Neugebauer theory. A halftone area is composed of at most eight colored dots: Cyan, Magenta, Yellow, Red, Green, Blue, White, and Black. These eight basic colors make the twelve skeleton edges of color solid independent of color mixing method.
On the other hand, the surfaces of color solid surrounded by twelve edges are determined mostly depending on the mixing method of two primary colors. It is shown how the color gamut and the chromatic locus change by the overlay method of two colored halftone dots. Experiments on a thermal transfer color printer resulted in a very good coincidence with the theoretical estimations. The dot allocations of primary colore cause the significant changes in the hue of red tone and the gamut of bluish colors.

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The energy distribution of localized states in amorphous As₂Se₃ (a-As₂Se₃) has been extensively studied in terms of a time-of-filght (TOF) or a transient photodecay (TPD) technique. Although the exactly same behavior is expected of TOF and TPD photocurrent transients in the light of a trap-controlled band transport theory, in which homogeneous spatial distribution of localized states is explicitly assumed, the respective shape of the experimentally obtained TOF and TPD photocurrent is different. This leads to considerable controversy with respect to the distribution of localized states even in a prototypical amorphous chalcogenide, a-As₂Se₃. In this paper, the influence of surface states on current transients is examined via computer simulation based upon the trap-controlled band transport theory. The surface states are taken into account by increasing characteristic temperatures of exponential distributions of localized state at the surface region. It is demonstrated from the simulation that the disagreement between the TOF and the TPD transients can be resolved by introducing the surface states.

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A residual image phenomenon of hydrogenated amorphous silicon (a-Si:H) photoreceptor has been investigated from analyses of carrier mobility and life time. As the result, it is found that the residual image is occurred by remain of minarity carrier near the photoreceptor surface. Especially, the residual image is apt to occur when a-Si:H photoreceptor is used in the following conditions; (1)a speed of imaging process is high, (2)a light source with long wavelength is used in the exposuring process, (3)a drift mobility of the minarity carrier is less than 10^-2 cm²/V&mdot;s due to boron doping.
The residual image can be reduced by a suitable choice of the wavelength of light source and the doping amount of boron.

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The Staebler-Wronski effect in a-SiGe:H alloys bas been examined for the highly photoconductive alloys prepared by the microwave-excited plasma CVD method. It was found that the light induced change in photoconductivity depends upon the Ge content in alloys, rather than upon the initial value of the photoconductivity. The light-induced change in photoconductivity decreased with the increase of Ge-content and disappeared in the alloys with equi-molar composition of Si and Ge, irrespective of initial value of the photoconductivity. The above mentioned dependence of the Staebler-Wronski effect upon the alloy composition was not continuous to a-Si:H, and the light-induced change in photoconductivity of the alloys with small amount of Ge was larger than that of a-Si:H. These results suggest the difference of subgap states between a-SiGe: H and a-Si: H.

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The ionization potential and the hole drift mobility of organopolysilanes with different kinds of substituents were investigated for the best use of their high mobility in layered organic photoreceptors. The ionization potentials of alkyl-substituted organopolysilanes showing themochromic behavior were found to vary from 5.7 to 5.9 eV with themally induced reversible confomational changes in the Si backbone, while aryl-substituted organopolysilane gave a smaller ionization potential of 5.62 eV due to σ-&pai; mixing between Si backbone σ and side-group &pai; electrons. The hole drift mobility of organopolysilanes was found to be dependent on the σ-conjugation length in the Si backbone and successfully analyzed in the framework of Gill's empirical expression, which led us to the conclusion that the charge carrier transport in organopolysilanes is controlled by charge hopping through the intrinsic states derived from “domainlike” σ-conjugated segments of the Si backbone. Instead of “transport-inactive” binder polymers such as polycarbonate resin (PC) so far, organopolysilanes with high mobility and film-forming capability were shown to be useful for a “transport-active” polymer to be doped molecularly with low-molecular-weight charge carrier transport compounds. As an interesting result, the organopolysilane doped with a charge transport compound having the same ionization potential to organopolysilane host, gave the highest hole drift mobility of 10^-3 cm²/Vsec for amorphous polymeric solids. The layered photoreceptors consisting of organopolysilanes and organic pigments showed the high photo-sensitivity endurable for the practical use. The combinations with some organic pigments, however, were found to exhibit the anomaly in hole carrier injection from organic pigments to organopolysilanes contrary to a common knowledge in the usual organic layered photoreceptors. The doping technique improved the anomaly as well as some other practical problems. These results suggested that organopolysilanes are the promising material for the practical use in electrophotographic photoreceptors.

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A novel method for preparing pigment thin films on an Al substrate was presented. The controlled-current electrolysis of pigment-dispersed solutions gave the pigment films on the Al substrate used as a cathode. The X-ray photoelectron spectro-photometric and scanning electron microscopic analyses of the Al substrate and the films grown on it revealed that the film formation may be induced by the physical and chemical alterations in the Al surface. Film-formation experiments using α, β, and ε-type copper phthalocyanine pigments indicated that the electrolytic processes is accompanied by no changes in crystal form. Film-formation experiments were carried out by varying the electrolytic condition such as electrolysis temperature, amount of electricity passed through the AI substrate, and current density. It was found that the surface coverage of the pigment can be controlled over a wide range by controlling the current density.

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Characterstic specifications of videoscope were presented by the principle, the way of use, and the actually realized specifications in the videoscopes of various manufacturs.
The status of the endoscope image file which has been highlighted by the introduction of videoscope was also prensented.

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