In a single-layer organic photoconductor (OPC), depletion charging and surface charge injection are important issues in the electrophotographic (EP) process. During the initial stages of the charging process, a finite amount of free and shallow trap generated charges are swept out of the bulk of the photoconductive layer. Also, surface charges from corona ions can be injected into the layer due to the adsorption of corona generated chemicals on the free surface. Such depletion charging and surface charge injection reduce the charge acceptance. However, in high gamma photoreceptors, the charge acceptance is not reduced in any degree in spite of abundant depletion carriers and excess surface charge injection. The photoinduced and dark discharge characteristics of such high gamma photoreceptors are found to be well described by a mathematical structural trap model which takes into account both carrier depletion and surface charge injection.

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Electrophotography is the technology of controlling toner at high speed and precision. In order to achieve such various advanced requests as better picture, speeding up and colorization, simulation-aided design with Discrete Element Method (DEM) is important. On the other hand, in DEM, the electromagnetic and mechanical interactions between all particles are calculated and each equation of motion is integrated every time step, so the computational cost amounts to very high. In recent years, Graphics Processing Unit (GPU) has received remarkable attention as a low-power-consumption, inexpensive and high-performance shared-memory parallel processing unit from a wide range of areas including High-performance Computing (HPC). Numerical simulation with these GPUs is applied to various scientific computation and achieves very high operation performance. In this paper, we applied the common-used speed-up technique in HPC such as GPU and the tree method to toner particle simulation based on DEM. Then, we implemented the present method on one thin node of TSUBAME 2.0 and verified the method.

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Paper curl is one of the major troubles in electrophotography, and decurler device is put into place in order to reform paper curl. At decurler device, paper is bent in large curvature against curl direction to be reformed. In doing so, reformation amount of paper curl is affected by radius of roller, nip load and other decurler parameters. In addition, curl amount to be reformed varies with paper brand, fusing system and image density. For these reasons, enormous costs and hours are required for designing decurler parameters. To resolve this problem, we built a simulation model to predict paper curl reformation by numerical model considering paper characteristics such as elasticity, plasticity and viscosity. As a result, we established simulation technology to design decurler parameter on virtual experiment.

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It is briefly surveyed how an imaging technology has been progressed against the changes in social environment surrounding printing technology, and, in user's requirement on image for the past 30 to 40 years. We summarized the recording principle of various printing technologies, the characteristics and usages. We could summarize a nature of differences between three existing printing technologies (Electrophotography, Inkjet and Thermal recording) and those which were finished its role, or, disappeared. As a result, we have found that existing printing technologies have usages utilizing its characteristics, which other printing technologies don't have, or, they are technologies developed according to each usage. In addition, we have found the printing technologies required 10 years from now is a value-added one. It mentions 3D printing technology as an example.
This report is documented based on the contents of the Keynote Speech “Novel Printing in the Near Future—Principle of Hardcopy—” in the annual conference ICJ2010 of the Imaging Society of Japan.

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Stencil printing is roughly divided by distinguishing features of plates into two specific kinds--screen printing and mimeograph. A lot of development has been made for mimeograph since Zuccato's invention in 1874. Especially since 1980, uses of mimeograph have rapidly expanded with the realization of the integrated duplicator which has fully automatic platemaking and printing functions, and the establishment of digital thermal platemaking which can deal with digital information. Today, taking advantage of the imaging technology for convenient, quick, and large volume printing, a thermal stencil duplicator, a modern mimeo, is used for business-use, convenience printing, etc. in many countries. This paper reviews the history of such developments and explains the essential part of the imaging technology of thermal stencil duplicating with the viewpoint of platemaking, printing and process designing.

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Canon NP electrophotography (NP-system) was developed in 1965, which was different method from Carlson process. NP system is characterized by simultaneous image exposure and AC discharge, it is different from the Carlson method. We developed many kinds of products using NP system. To solve many problems for products, we had a lot of peripheral technologies. CdS was used for a photoconductive material. The photosensitive plate of NP process contains three layers. It comprises a conductive base, a photoconductive layer, and an insulating layer. The photosensitive plate had so wide range of wavelength-sensitivity that it applied for laser printers and color copiers.
We had developed a rubber blade cleaning system. The insulating layer of the photosensitive plate was so hard that the photosensitive plate was rubbed by the rubber blade. This rubber blade cleaning system is used to almost of copier now. This techniques become long-lived.
In the NP system, an insulating layer has an electrostatic latent image, which enables having the electrostatic image on the photosensitive plate for a long time. This characteristic is applied to the screen process technology. And we were commercialized a mono-color high-speed copiers.
NP system, the potential of electrostatic image was influenced by the environment circumstances. So we developed a sensor to detect the potential on the photoconductive plate and controlled the potential. This technology was used for the color copying machine, because no color-changing is allowed in the color-copying-machine.
During developing many kinds of products using the NP system, we have being making new technologies to solve many kinds of problem. New system technology like NP system creates the many ideas and the strong mind for the engineers.

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Electrostatic printing is classified as the printing method in which electrostatic latent images is generated by pin electrode discharge among non impact printing technologies. The electrostatic printing technology has the characteristics of simple printing mechanism and has built the application fields such as facsimile and wide format plotter. For satisfying the demand of plain paper printing, plain paper printing technology was developed. In this report, comparison between electrostatic printing and electrophotography is also carried out.

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This paper introduces a group of printing technologies which make surface charge image by ion projection. Histories and achievements of the following three major technologies are described : 1) Ionography process which use individual AC discharger for each dot;heavy duty high speed printing is its specialty utilizing toughness of dielectric imaging drum that enables simultaneous image transferring/fixing with pressure roller, 2) Ion flow process which use a common corona discharger and individual ion control apertures;its specialty is continuous tone reproduction at each dot, 3) Retention process which use photoconductor screen for ion controlling;its specialty is high speed duplication utilizing image memory function of the screen. The reasons why the three technologies have not been popularized are also mentioned. One of the major reasons must be related with the history that digital printing technologies have defeated analog printing technologies by using strong tools of mass storage image memories and advanced digital half toning methods.

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Elcography is new imaging process that it is used the hardened ink, which is hardened by electrochemical reaction. It is possible to make high speed printing, because this hardened reaction speed is so high. This reaction is used by the cross-linking reaction with poly-valence metal ion.

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Cycolor is a unique photoimaging system for the application in color copying. This system is based on the photo-hardening of acrylate monomer contained in microcapsules. The paper focuses on how this system provides color images via a single exposure and discusses the photochemistry of latent image formation. It was said, at that time, that the advantages of Cycolor are high image quality, rapid processing, excellent color quality, and tone reproducibility. On the other hand, problem with Cycolor seems to be its durability of images due to the reversible chemical reaction. From the technical point of view, the poor durability might be one of the reasons why Cycolor disappear.

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Recently, we hardly see a blueprint in a daily life. The blueprint is a name instead of diazo copy. Because the mainstream of image copied by using the diazo reprography process was blue image, diazo copy was called a blueprint. The diazo paper and the copying machine were the reprography process that become popular widely from 1955 to 1975 in this country. The image formation process consists of two characteristics property of diazonium salt that was applied to the diazo paper. First, the diazonium salt is decomposed by photoirradiation and becomes colorless compound. Secondly, the diazonium salt which was not decomposed generates a colored azo dye by reacting with a coupler. By using this characteristic of diazonium salt, the posi-posi image is generated by passing through an exposure process and a developing process. Because of low price and easily operation, the diazo reprography process had been used in a large quantity of copy uses of the drawing and so on in various business field. In this article I would like to explain about the change of the diazo reprography process that is one of the diazo imaging technology.

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