A high-speed color laser printer at a printing speed of 50 ppm has been developed. The printing process consists of four OPC drums each with a two-component developing unit and roller transfer through a dielectric belt.
This paper describes the transfer process theoretically and experimentally, based on the analysis of the equivalent circuit model. As a result, it is clarified that the transfer voltage is decreased by opposite polarity charge to the dielectric belt the transfer roller.
We have obtained the most suitable method to design the transfer process in the color laser printer.

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The color reproduction of the electrophotographic print strongly depends on the fusing properties of color toners. To obtain the excellent color tone, the color toners must be melted enough and the surface of the toner layer must be smooth. The gloss value of the color picture with the sufficient smooth surface is over 10. And the gloss value and the color tone of the picture strongly depend on the image density.
On the other hand, there are many problems coming from the influence of silicone oil applied to the heat roller. By including the large amount of the releasing agent to the color toner, the color images could be fixed without applying silicone oil to the heat roller. However there are the many subjects to handle such color toners.

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We have examined relations between development efficiency and graininess of developed images. We have modified Kurita's model for the charge transport equilibrium mechanisms which determines mass of toner developed in the two-component developing system. The term of the counter-charge layer is replaced as follows;
d_c/k_cθ=d_snF_v/F_ek_cθ
Q/M, θ, particle size of toner and distributions of latent image potential have been varied in the examinations. The results have corresponded to the theory and development efficiency and graininess have been correlated. We have also found that the reduction of particle size of toner causes the decline of development efficiency.

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We developed a new half-tone rendition method for electrophotography. This method is based on conventional multi-level error diffusion method. It switches threshold levels adaptively according to the signal of preceding pixels, so that it suppresses to output isolated narrow signal, which causes unstable rendition.
We calculated potential histgram of latent image, by computer simulation, and confirmed that frequency of lower potential is reduced, as we desired. By experiments by actual printing, we confirmed that this method realized linear gradation characteristics, higher rendition and lower noise level at high-light area, comparing with conventional methods.

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It is well known that an image has a particular gazing area. From the experimental results of our previous papers, we found that total image quality is highly influenced by quality of the gazing area. In this paper, we evaluated total image quality of degraded images by a physical quality criterion calculated from the gazing area. The experimental result showed that the calculated criterion is not dependent on the scene. On the other hand, the criterion calculated from the whole area of the image is dependent on the scene content. In this paper, the effectiveness of the evaluation of image quality under the consideration of gazing area is presented and discussed.

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The role of carbon black and CCA in triboelectrification was elucidated by studies on the mechanism of charge polarity inversion during agitation of model toners with silicone-coated ferrite carrier. Carbon black itself has very low tribocharging ability. The role of carbon black seems to be to decrease the number of charging sites on the surface of the toner particle. CCA itself has very high tribocharging ability. The role of CCA seems to be that the charge of the toner particle is either increased or decreased from the toner composed only of the resin even if the presence of CCA on the surface of the toner particle decreases the number of charging sites composed of the resin. It is proposed that triboelectrification of two-component developers can be estimated by the concept of the time and energy dependent charging of positive and negative sites that arise on each component (binder resin, carbon black and CCA) of the toner surface.

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Toner particles were synthesized by suspension polymerization technique. Styrene and butyl methacrylate were used as monomer with the ratio of 7 to 3, and fillers, such as carbon black, charge control agent (CCA) and wax were incorporated. AIBN was used as initiator and tricalcium phosphate slurry, as stabilizer. Most reactions were carried out at 70 to 80°C, and reaction generally took 6 to 9 hours, depending on reaction condition. Adding filler particles significantly decreased the reaction rate, thus conversion. This phenomenon became more manifested for CCA and wax particles. The glass transition temperature, determined by DSC, was found to be around 60°C regardless of the amount of filler particles. Particle size varied from 4 to 15 um in diameter, depending on polymerization condition. Charge to mass ratio was determined to be -15 μC/g. Imaging test has been conducted, which exhibited a fine image.

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From the viewpoint of digital latent image formation, the induction effect of pigment dispersed single layer photoreceptor is calling attention once again. In this study, supposing charge mobility to have negative electric field dependency, the induction effect was theoretically explained. On the other hand, supposing structural traps to exist at charge current path, the induction effect was also deduced with calculation. These results suggest that the induction effect occurs because of the peculiar charge transport process, in which structural traps bind charge carriers under strong electric field.

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The title compound (abbreviated to DTPP) is known to possess three crystal modifications, among which only modification III exhibits an intense near-IR absorption. Because of this, DTPP has attracted attention as a material suitable for laser printers as well as optical information storage systems based on GaAsAl laser diodes. Modifications I and II are quite similar and crystallize in a “herringbone” fashion; whereas modification III is characterized by the “bricks in a brick wall” structure composed of homochiral hydrogen-bond pairs and heterochiral convex and concave pairs. The mechanism of the near-IR absorption has been therefore investigated from the standpoint of exciton coupling effects. The exciton displacement energies due to the nearest molecule-pairs within a sphere of about 30 A (12 pairs for modifications I&II and 16 pairs for modification III) have been calculated on the basis of the crystal structure. The hydrogen-bond pairs are found to displace the optical absorption towards longer wavelengths by about 1500 cm^-1 in all modifications. In modification III, the convex and concave pairs additionally contribute to the bathochromic shift. These results indicate that the “bricks in a brick wall” structure plays the decisive role for the appearance of the near-IR absorption.

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Due to an intense near-IR absorption, the title compound has recently attracted attention as a material suitable for laser printers and optical disks. The near-IR absorption, however, appears only in modification III characterized by the “bricks in a brick wal1” structure comprising three kinds of molecule-pairs: hydrogen-bond, convex and concave pairs. Intermolecular forces in modification III have been investigated by means of an energy partition analysis of the total energy on the basis of molecular orbital calculations. In the H-bond pair, the orbital overlap and the electrostatic interactions almost equally contribute to the stabilization of the total system. On the other hand, in convex and concave pairs, the intermolecular interactions are found to be purely of electrostatic nature. The present calculation gives us a rough picture how the “bricks in a brick wall” structure is formed in modification III.

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Recently, K. Sukata et al. proposed the theoretical equation of triboelectric charging mechanism by kinetic model at Electrophotography (vol. 36(4), p. 260-267, 1997). Their model equation is similar to our model¹⁾equation. However, they made a big mistake to solve the equation, then they obtained the opposite conclusion to ours. In this paper, we give the collect solving method of their equation and point out their error (mistake) and we do correction of pointed out part by K. Sukata et al.

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FX DocuColor4040 was launched into the Japan market with the highest Xerographic color printer speed (40 ppm/A4) in the world, targeting the short run color market in November 1995. This tandem color printing technology which is able to make one-pass full color prints extremely improved the printing speed, compared with the multiple transfer one, however there existed concerns of the print quality and machine reliability due to component increase. In particular, the subject for the high accuracy color registration technology is important and difficult to deal with, so the innovation of a new technique was proposed, not to be the improvement of a conventional one. This report describes the new technology of Docucolor4040 to counteract these problems, especially about the high accuracy color registration technology.

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