We report the theoretical study and the model experiment on twisting ball displays for lowering their driving voltage toward the application of digital signage. A motion equation was theoretically derived for describing the rotation of a cylinder type display element. The motion equation suggests that there are two ways to lower the driving voltage. One is to increase the σ which represents the difference in the surface electric charge densities of the black and white regions of the display elements. Another is to increase the sinθ. The θ is the angle between the boundary of the black and white regions and the perpendicular to the electric field. The rotations of display elements were also characterized experimentally, with particular emphasis on the threshold voltage and the response time, as a function of σ and θ. We found theoretically and experimentally that both σ and θ are important parameters to lower the driving voltage of twisting ball displays.

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A novel and easy method for preparing color-changeable Ag films/plates was discovered using aqueous solutions of sulfides as coloring agents. In the presence of specific sulfides such as lime sulfur solutions, the color of Ag films/plates, initially sliver, changes to yellow, red and blue depending on the preparation conditions such as the dipping time in the solutions and the temperature of the solution. One of the potential candidates is in the application as imaging materials. Assuming the imaging by inkjet devices, we have already investigated the ink receiving nature to Ag films/plates. The focus of this present work is to explore the nature of sulfide solutions which act as inks for changing the color of Ag films in the inkjet system. We found that both the solubility of sulfides in water and the nature of the hydrolyzed constituents of sulfides are important parameters for obtaining successful color-changeable Ag films in this imaging system. For example, K₂S solution works well as coloring agent due to its appropriate solubility in water and KSH, one of the hydrolyzed constituents of K₂S, play an important role to change the color of Ag films/plates.

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We have modeled the charging process of rotating organic photoconductor (OPC), ionic wind and ozone transport by positive direct current (DC) scorotrons. The models have been validated by comparing numerical simulation and experiment. We have shown that the potential on OPC after charging decreases in higher printing speed, though the drum current increases. With numerical simulation of the charging of OPC and the ionic wind, we have conjectured that the charging of OPC will be less effective, concentration of ozone will be higher and the contamination of the wire will be severer when we increase the corona current.

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A novel method that enables the measurement of an electrostatic latent image on a photoconductor is proposed. An electrostatic latent image is formed through electric charging and laser exposure of a photoconductor within a vacuum chamber. The significant feature of this method is that the charging, exposure, and detection devices are all incorporated in the same system, making real-time measurement possible. The electrostatic latent image is measured by detecting secondary electrons generated by the scanning of an electron beam probe. When a primary electron beam hits the photoconductor, secondary electrons are generated. Secondary electrons generated in a charged area travel to an electron detector. In contrast, secondary electrons generated in an exposed area are pulled back to the photoconductor, thereby decreasing the number of secondary electrons that reach the detector. This method has good performance with high-resolution measurement on the order of microns.

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In the fuser process of electro-photography, defects may be caused by a phenomenon called electrostatic offset, in which image smear is caused by toner from the fuser member adhering to the paper after one rotation of the fuser member. This toner is transferred from the paper to the fuser member by electrostatic force. The occurrence of electrostatic offset depends on the electrical resistivity of the fuser member and electric potential of the fuser delivery roller. In this study, we calculated the electric field of the fuser nip region, determined the shape of the fuser nip by structural calculation, and thus examined the physical mechanisms by which the electrostatic offset occurs. We also found that the occurrence of electrostatic offset can be predicted by the electric field strength of the fuser nip region and the electric charge distribution of toner.

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Numerical simulation model has been proposed to predict fix strength on a xerography fuser process. Especially, the model can consider the influence of a paper surface roughness and of a toner dynamic viscoelasticity. The model is derived from the coupled simulation which consists of the structural, the fluid and the thermal simulation. The structural simulation can clarify how a fusing material fits the roughness on the paper structure. The fluid and the thermal simulation can solve the toners transitional deformation on a fuser nip and calculate a contact area between the toner and a paper, which takes into account involved factors : a toner viscoelasticity, thermo-physical properties of materials and a fusing temperature etc. The coupled method can calculate the contact area which agrees with experiments. Additionally, the results have shown that the roughness on a paper structure and the toner viscoelasticity strongly affect the fix strength.

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Paper curl is a phenomenon in which arc-like residual deformation occurs, and degrades publishing quality. To reform the paper curl, decurler devices are installed in electrophotography products. In the decurler devices, the amount of reformation of the curl is affected by parameters including radius of rollers and nip load. Furthermore, the amount of the curl to be reformed varies with paper brand, type of fusing system and image density. For these reasons, much effort and many resources are required for designing decurler parameters. To clarify the mechanism of the curl reformation, measurements of the amount of curl are taken under various conditions, and it becomes apparent that the paper curl is dependent on plastic and viscous characteristics of paper. By calculating the history of stress-strain state during transportation through decurler devices with a visco-elasto-plastic model, prediction of the amount of curl become possible with a high level of accuracy.

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We introduce the image quality prediction method using the print quality simulator that predicts the digital image in consideration of the influence of landing accuracy of ink droplets, in order to predict the influence on images by the plurality error factors of inkjet printers. The simulator has become possible to consider the tolerance allocation by comparing the simulation results under plurality error factors. In addition, by using results of the simulation that is capable to reproduce satellite droplets on image, we have proposed a new image quality prediction equation that can be quantitative assessment of the influence of the satellite droplets. Furthermore, it has been found that a proposed prediction equation for image quality including satellite droplets is also possible to predict the bar code quality.

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Stability of a conducting inviscid drop hanging from a nozzle in an electric field with corona discharge is examined theoretically. By this static model with linear stability analysis, jetting mode change of electrostatic inkjet process is estimated. The basic equations, the augmented Young-Laplace equation for drop shape and the Poisson equation for electric field, are coupled and solved by the Finite Element Method. With the increment of non-dimensional electric field, a drop is deformed and subject to corona discharge. According to the shape and the applied voltage at the turning point where the system changes from stable region to unstable region by the linear stability analysis, jetting voltage and the mode of electrostatic inkjet are determined. It is found the existence of corona discharge reduces its stable jetting range. However, there still be needed to include other effect, such as corona wind for the better prediction of jetting mode change by this static model.

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Simulation of printing processes involves modeling of complex processes and materials. It has to be accurate and provide results in a timely fashion. Detailed modeling of printer components and the target of modeling entire printing process are discussed. Technalysis modeling activities towards this goal is summarized. Several case studies are presented describing approaches taken. Development of continuum, particle models, their coupling and analysis of the overall system are emphasized. Close cooperation between test and simulation is referenced both for determining material properties and for validating simulation models. Testing and simulation have to be used concurrently to reduce time to design and improve quality. Recent activities have been centered around strong coupling of particle and flow problems.

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We have developed a numerical method for calculating the motion of toner and carrier particles in an electrophotographic two-component magnetic brush development system to improve system performances by using a three-dimensional distinct element method. Key features of this simulation method are that forces applied to toner and carrier particles include not only magnetic but also electrostatic forces involving a time-dependent electric current in the brush of conductive carrier particles and the air drag due to the airflow induced by the rotation of the development sleeve and photoreceptor drum. Numerical calculations were performed to investigate several subjects that have not been investigated thoroughly : chain formation of the carrier brush, effectiveness of noncontact development, bead-carry-out, and effect of airflow. It was confirmed that the calculation results agree with the experimental observations, and some countermeasures against image defects are proposed. It is expected that the presented numerical method can be used to improve the two-component magnetic brush development system in electrophotography.

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This paper provides an overview of the recent progress of simulation technology for the transfer processes of electrophotography. A simulation model for a transfer process is a complicated one because it includes electric field, convection, discharge and a movement of toner. However, thanks to the recent progress of simulation technologies and highly efficient computers, three-dimensional simulations have been reported. This paper introduces some models, which are recently reported;three models for analyzing transfer process with toner motion, and one model for considering the effect of the toner shape. These models can offer faithful results, and simulation becomes a more useful tool to design electrophotography.

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Suitable simulation models and design methods must be established for parameter design of xerographic systems with simulation. Thermal control design of a complex fusing unit requires a simulation tool not only with high accuracy but also with high speed. The simulation model developed in this study utilizes a hybrid calculation technique of one and two-dimensional heat transfer model, and is capable of high-speed calculation without decreasing accuracy. In this model, heat transfer efficiencies between components are defined and determined in advance by one-dimensional numerical analysis. The simulation tool for belt roll fusing units installed in Fuji Xerox Color 1000/800 press was developed and applied to parameter design. Development time was greatly reduced as a result of its application.

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In copiers and printers that use electrophotography, the fusing process is one of the causes of paper curl. There are two mechanisms that generate curl during fusing : the first is the temperature difference between both sides of the paper, and the second is the bending of the paper in the nip region. In this article, we show the curl mechanism due to the temperature difference and the prediction methods for the two causes of curling. For predicting temperature difference curl, a moisture transportation analysis is proposed that calculates the distribution of moisture in the thickness direction. Next, the stress relaxation of the heated paper is measured experimentally, which uses the prediction of the curl caused by bending in the nip region. These two prediction methods are evaluated, and the calculated and experimental results are found to be in good agreement.

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