Simulation Technology for Analyzing Xerography

Xerography used for printers and copiers is a complex process involving various physical phenomena in which many factors, including electromagnetic, structural and heat factors, are mutually affected. Fuji Xerox is conducting research to enhance images and improve device performance by reproducing the phenomena through numerical simulation and clarifying their mechanisms. Using such simulation technology, we promote development efficiency and speed up the development time.

In xerography, various types of copy-quality degradation may occur depending on conditions. For instance, Fig. 1 (a), an enlarged invert image, shows a decrease in image density on the left side of the character.

However, it is not easy to specify the mechanism of such degradation due to multiple possible causes. Our approach to this is simulating the image state as shown in Fig. 1 (b) by calculating the motion of each toner particle forming the image. With such calculation, we can find the best conditions for image formation and make products that can provide stable and high quality images over long periods.

Xerography mainly consists of five processes: charging, exposure, development, transfer, and fusing. In charging and exposure, the discharge phenomenon and photoelectric effect are used, respectively. In development, the electric field acts on the charged toner particles, thereby attracting the particles to the photoreceptor in order to form a powder image. In transfer, the toner image is transferred to paper by the effect of the electric field again. Lastly, the image is permanently fused and fixed to the paper. According to each of these processes, we have developed numerical simulators for discharge, electric field, charge transport, toner particle motion, toner fusing, etc. and enabled the numerical reproduction of xerography on computers. By analyzing phenomena with such simulation technology and advanced measurement technology, we can realize products of higher quality and reliability.

Fig. 2 shows an example of the development simulation with particle motion analysis. The developer-the charged toners (red) electrostatically-attached with magnetic carriers (gray) -forms a brush structure in the magnetic field and moves with rotation of the development roller. The image is formed when the toners on top of the brush move and attach to the photoreceptor due to the electrostatic force in the field.

For enhancing our product quality, we utilize simulation technology to calculate and predict the actual developed images, and clarify the relation between development conditions and image quality.