In the case of binary printers, reproducible halftone steps have been associated with line per inches of halftone screen and resolution of system. As electrophotography has a property of continuous tone reproduction, the graininess of printed images turn out very important point of discussion instead of tone reproducibility. The simulation model for the image noise of half tone predicts the close relationship between toner particle size and spot size of raster scanning laser. Graininess of printed images becomes worse by wider range of continuous tone reproduction, according to higher screen resolution. This gives limiting conditions for the high-definition printing on electrophotography.

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Image output devices using electrophotographic systems that target the conservation of energy achieve higher levels of energy consumption efficiency as a result of power supply control. Through their use of micro-encapsulation technologies and their superior anti-blocking performance (by preventing fusion between toners), low-temperature fusing toners represent a means of achieving higher levels of energy conservation. This report establishes a micro-encapsulation process for encapsulating a solid and evaluates the anti-blocking effects of various toners that have been micro-encapsulated. The results of this report show that the micro-encapsulation of low-temperature fusing toner materials gave them better anti-blocking characteristics and confirmed the possibility of low-temperature fusing toners.

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Compensation method for illumination change, which has big influences on the characteristics of imaging system, is studied. On the condition that color chart is placed in the view of camera, the imaging system recognizes the color chart and the signals from the camera are processed by using the color chart data. Concerning the light from the window, fluorescent light and incandescent lamp, it is confirmed that color chart is possible to be recognized and the color system is corrected to the expected chart signal within the error 5∼7% by considering quadratic terms of RGB. This method is considered to improve the accuracy of motion detection and also to better video communication by realizing preferable color reproduction.

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A compact draw-off type instrument for measuring toner charge has been developed. The instrument can measure the charge to mass ratio (q/m) of both two-component and one-component developers. The instrument can also measure toner charge on a photoreceptor, or on several intermediate media or even on paper. The instrument is highly maneuverable due to the small size of its nozzle unit, thereby ensuring extremely versatile measurement capability. Toner particles are directly absorbed into a Faraday cage by means of a draw-off separation method, so that the measurements are highly accurate. We have found that accurate toner charge measurements could be obtained for two-component and one-component developers by using this instrument. This instrument should be useful for the further development of electrophotographic printing systems.

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The simulation methods of charging and flow behavior of developers in an electro-photographic system are described. The simulation of the charging behavior of toner particles is performed by using the charge transfer equation obtained by impact experiments between plastic spheres and plastic or metal plate. This simulation method, which gives the relation between charging properties and chemical components of toner particles, can be applied to the design of toner particles with optimum charging behavior. The development and flow behavior of a two-component developer are simulated by particle element method taking into account the magnetic and electrostatic interactions between developing particles. The proposed simulation gives very useful information for the design of a two-component development system.

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Numerical simulation is applied to the design of an electrophotographic development process. Magnetic field generated by a magnetic roller is evaluated based on the finite element method (FEM), and motion of development particles is calculated by the distinct element method (DEM). In this report, two issues are discussed. One is toner blow out from cartridge. Detail of toner flow was investigated based on the simulation using data of actual cartridge shape and experimentally measured magnetic field profile on the surface of a magnetic roller. As a countermeasure against the problem, optimized development cartridge shape was proposed. Another issue is what we call poor release problem of development particles from the surface of a magnetic roller. When magnetization pattern of a magnetic roller is inappropriate, particles leaving the magnetic roller surface at a release point are trapped back to the roller resulting in poor image quality. To resolve the problem, the magnetic field profile was modified to increase the repulsive force at the release point. The toner flow simulation indicates that the modified condition is effective as the countermeasure of the poor release.

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Numerical simulations of electrostatic field and of toner motion in the transfer process are reviewed in this paper. In the transfer process, charged toner particles are transferred from one surface to another with the electric field formed in the transfer nip. In order to investigate the transfer process, numerical simulation of electric field is very useful and is carried out energetically. The study of toner scattering with two-dimensional electrostatic simulation is introduced as an example of electric field study. The studies of hollow defect and of toner scattering by Discrete Element Method are also explained as examples of toner motion analysis. These cases show that numerical simulation is very useful for designing and investigating a transfer process in electrophotography.

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In the design process of high-speed laser beam printer, we tried to apply the Analysis-Leads-Design approach. It is one of the evaluation methods using the simulation technology. The purpose of this approach is to improve in reliability and to shorten the design period. Two examples are shown. One is the simulation of a developer flow using a viscous fluid model. And, another is the simulation for fusing system using the thermal analysis.

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For MFP (Multi Function Peripheral)development, simulations are surely informative to figure out temperature increase that is by-product. This paper shows current methods with categorizing into main body and electronics unit. In case of electronics cooling, although CFD (Computational Fluid Dynamic)tool performance has been advancing, how to estimate heating value at device that is boundary conditions cannot be fixed. Author keeps experiment to a minimum by searching an apt system for each range of heat value. In case of the main body cooling, it is ultimately complex system due to the fact that a paper works as a heat transfer media and causes temperature increase at engine and everywhere inside a machine. The development engineers are requested to timely propose low-cost parts configuration with considerations to the aspects such as local cooling, heat exhausting and ozone emission, during short developing term. Therefore, phenomenon that are difficult to predict such as a transition of paper temperature after fusing and temperature of the area affected by toner behavior, are treated as a simple experience model.

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Two-dimensional numerical simulation of cross sectional behavior of sheet moved along a handling path in electrophotographic equipment is reviewed. The two-dimensional analysis is very useful for layout design, because a lot of simulation jobs can run with various cases economically. In this paper, a computational method to analyze transient behavior of the sheet with friction force from a paper guide and gravity is explained. Furthermore, several studies of the behavior unique to electrophotographic equipment are shown.

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Several examples of visualization and measurements which show toner motions and toner image formation processes in development processes inside electrophotography products are shown in this paper. Visualization measurements of toner movement and time-series three-dimensional measurements clarify how toner particles move and toner images are formed. Moreover, by employing PIV and PTV techniques, visualized images are quantified. Those various numerical datum are used for connecting process design and material design.

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