Fundamentals of color reproduction, in particular color formation in multicolor halftone prints is studied. Color correction and enhancement is discussed.
It was found that achieved color depends, besides the dot percentages of the subinks, also on the point spread function of the printing process, the absorption spectra of the inks, the surface and internal reflections in ink layers and microscopic noise of the halftone dot profiles.

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The paper has two parts. First, a systematized overview is given of fundamental aspects related to image quality measurement. Second, the influences of geometrical image degradations on image quality are analysed by means of simulations and analytical computations. Image quality is expressed in terms of information transfer. The results elucidate the role of line and dot spreading, and edge noise on quality, presented as a function of spatial line frequency and halftone cycle frequency.

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The first monocomponent developers introduced to the market were used for direct fixation on dielectric papers. Their low electrical resistance prevented transfer to normal papers. Today's monocomponent developers have a much greater resistance. In this study, developers with various silica coatings are investigated. Alteration of the frequency distribution of the electrostatic charge (q/d) and of the electrical conductivity (DC) is determined.

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In recent years, solid-state diode lasers have advanced remarkably. Active researches are under way with regard to dual-layered photoreceptors using organic materials, especially phthalocyanines (Pes) having sensitivity in the near-infrared region (760-830 nm) for laser beam printers. For instance, ε-CuPc and τ-H₂Pc have been studied. Moreover, phthalocyanines having trivalent or tetravalent metals have been reported by various researchers. Among them, oxotitanium phthalocyanine (TiOPc) has been noted for highly sensitive photoreceptor devices. An m-TiOPc compound has consequently been developed. The m-TiOPc compound was distinguished from α and β-TiOPc. This work describes the newly developed m-TiOPc compound and its application in printer use.
This paper derived the following conclusions.
(1) The m-TiOPc compound had characteristic peaks in X-ray powder diffraction patterns, and distinguished from other polymorphs of TiOPc.
(2) The analysis of DSC was shown the following results. The α-TiOPc had an exothermic peak at 230°C, and it was attributed to crystal transformation from α to β-phase. The. m-TiOPc compound was stable until 400°C, however, we could not analyze the peak at 400°C because of its lowering of crystallinity and decomposition of TiOPc crystal.
(3) The photosensitivity of the m-TiOPc compound photoreceptor device (using the hydrazone derivative) was 0.24-0.30 µJ/cm² in the wavelength of the 600-830 nm regions.

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The effects of a CGM on the photoinjection efficiency (PIE) in the layered organic photoconductor with a-phenylstilbene based-CTL which has a high hole drift mobility have been studied for the first time.
PIE measured shows different features due to the different CGMs, and the rate-determining processes estimated have been classified into two groups of a carrier generation process and a hole injection process.
From oxidation potential measurement, it has proved that a carrier generation process was observed as a rate-determining process when the oxidation potential difference between CGM and CTM was comparatively large, and that a hole injection process was observed when the potential difference was small.
It is considered from these results that the potential difference had driven the hole injection from CGL to CTL quantitatively in the former process and had not in the latter process.
Moreover, the relationship between (i) oxidation potential of azo pigment (CGM) which is the controling factor of hole injection and (ii) its chemical structure has been investigated. It is found that the oxidation potential of azo pigments in this experiment originates in the oxidation potential of diazo component.

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The origin of cone-like structure yielding image defects in amorphous silicon photoreceptors is discussed. The cone-like structure is related to the roughness of A 1 drum substrate and to adhereed alien substance on substrate. The correlation between adhereed alien substance and cone-like structure before and after film growth is obtained by replica method. When the size of alien substances increase, the size of cone-like structure increase. The cones grow in the direction of in-plane but do not grow parpendicular to the substrate plane. The results of XMA, Auger and IR analysis show that adhereed alien substances are silicate compounds which are introduced from outside floating dust.

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New types of a-SiC photoreceptors with excellent sensitivity have been developed using aSiC: H as a carrier generation layer (CGL) or a carrier transport layer (CTL). The a-SiC: H films were deposited at a high rate of 1-6 µm/h from a mixture of SiH₄ and C₂H₂ by a plasma CVD process. It is shown that the highly photosensitive film exhibiting ημτ-product more than 10^-6 cm²/V used as CGL and highly resistive film with a dielectric constant as low as ε_s=9 used as CTL can be prepared by selecting a deposition condition, especially the ratio of [rf power]/[source gas flow rate].

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