Development Roller Research Articles

Optimal doctor blade design considering contact stress and toner properties

The Doctor Blade is mounted to a toner cartridge and applies consistent pressure to the development roller. This part enables the toner adhering to the development roller to form a layer of consistent thickness. The contact pressure between the development roller and the Doctor Blade is an important factor determining not only image quality, but also toner cartridge durability. In this study, test points were extracted using a central composite design method and contact analysis was carried out using NASTRAN, an FEM tool. In addition, based on measurements of toner weight by unit area and image concentrations through sample production and experiments under various conditions, approximated models were derived using the response surface method. With approximated modeling of contact pressure set as an objective function, and approximated modeling in relation to experimental values set as constraint conditions, the optimal solution was derived by applying the optimization technique of genetic algorithms. Moreover, by applying the optimal solution to an actual sample, its reliability was verified through comparison of the optimal results of genetic algorithms with the actual solutions.

New Technology for Improving Image Density Uniformity in the Electrophotographic Process

This paper introduces a new method to reduce periodic density unevenness caused by eccentric rotation of the photoconductor drum and development roller in an electrophotographic printer. In a previous study, a method for controlling periodic density unevenness by using developing bias was proposed. The developing bias is controlled periodically to correct density unevenness. However, no control effects are obtained in low density images; rather, the control somewhat increases the density unevenness.In this study, we developed a new method that reduces the periodic density unevenness through modulation of both charging bias and developing bias based on the rotational periods of the photoconductor drum and development roller. Each bias is periodically changed such that the changes in the developing field due to the eccentric rotation of the photoconductor drum and development roller are cancelled, thus suppressing the periodic density unevenness. Experiments we conducted confirmed that the new method improves periodic density uniformity better than the previous method. The new method guarantees density uniformity is obtained without the use of high-precision components.

Formation of Charged Toner Layer and Degradation of Toner Particles in Doctoring Process of Electrophotographic Non-Magnetic Single-Component Development System

In a non-magnetic single-component development system in electrophotography, formation of a thin and uniform toner layer on the development roller is important for obtaining high image quality. We conducted experimental and numerical investigations to clarify the dynamics of toner particles in this process. Two approaches were adopted for the investigation. One is experimental and the other is numerical simulation using the distinct element method. We manufactured a mock-up apparatus consisting of a supply roller, a development roller, and a doctor blade for forming a thin toner layer on the development roller. The thickness, surface roughness, and charge density of the formed toner layer were measured after the doctoring process. It was clarified that the thickness of the toner layer was increased, but the charge density was decreased, by increasing the applied voltage and rotational speed. These findings were confirmed by direct observation of the toner motion in the doctoring area with a high-speed microscope camera. Numerical calculations performed using an improved distinct element method revealed that the elastic energy applied to the toner particles, which is an index of toner degradation, was increased by increasing the stiffness and pressing force of the doctor blade, but decreased when the curvature of the blade tip was large. The present experimental and numerical results can be used to improve non-magnetic single-component development system in electrophotography.

C-2-2 電子写真の非磁性1成分現像系におけるトナー層のドクタープロセス(C-2 柔軟媒体ハンドリング/画像形成機器2,口頭発表:柔軟媒体ハンドリング/画像形成機器)

In a non-magnetic single-component development system in electrophotography, formation of a thin and uniform toner layer on the development roller is important for obtaining high image quality. We conducted experimental and numerical investigations to clarify the dynamics of toner particles in this process. Two approaches were adopted for the investigation. One is experimental and the other is numerical simulation using the distinct element method. We manufactured a mock-up apparatus consisting of a supply roller, a development roller, and a doctor blade for forming a thin toner layer on the development roller. The thickness, surface roughness, and charge density of the formed toner layer were measured after the doctoring process. It was clarified that the thickness of the toner layer was increased, but the charge density was decreased, by increasing the applied voltage and rotational speed. These findings were confirmed by direct observation of the toner motion in the doctoring area with a high-speed microscope camera. Numerical calculations performed using an improved distinct element method revealed that the elastic energy applied to the toner particles, which is an index of toner degradation, was increased by increasing the stiffness and pressing force of the doctor blade, but decreased when the curvature of the blade tip was large. The present experimental and numerical results can be used to improve non-magnetic single-component development system in electrophotography.

Optimization of Dies for the Magnetic Development Roller Using Genetic Algorithm

Optimization of Dies for the Magnetic Development Roller Using Genetic Algorithm

Optimization of Dies for the Magnetic Development Roller using Genetic Algorithm

To optimize a multi-pole magnet roller a finite element method with Genetic algorithm is carried out. A multi-pole magnet roller recently used in the development system of the electrophotography, such as copiers, or laser printers. One procedure for producing the magnet roller is the extrusion molding with applying magnetic fields to the material. This scheme forms magnetic characteristics or flux density pattern by controlling to apply magnetic fields. For desired magnetic characteristics, we must adjust various parameters such as a shape of dies and current in the coils, but the fabrication required many efforts and resources. To make this process more efficient, a FEM simulation tool for the molding process has been developed. And Genetic algorism, which can optimize many parameters, is acquitted to decide these parameters. Then a high flux magnetic density at the main pole can be obtained in comparatively shorter fabrication time than the past.

Simulation of Two-Component Development Process for Frontloading Design

This report describes simulation technologies for digital frontloading of two-component development process in electrophotography. Electrophotography entails using multiphysics involving phenomena with yet unclear mechanisms such as air breakdown, tribocharging and powder dynamics. Thus, it requires much effort and many resources to develop electrophotography products. Numerical simulation is widely recognized as one of valid approaches to overcome these difficulties in product design. A tool for simulating the two-component development process has been developed including particle motion calculation using the Distinct Element Method and electric filed calculation using the Finite Element Method. The tool working on PC clusters is equipped with force decomposition method as a high-efficiency parallel computation algorithm to reduce calculation time. In addition, GUIs, and an online portal for PC clusters has been developed to support product designers utilizing the simulation tool. Validity of the tool was confirmed by comparison of developed toner mass and developer mass on development roller with the experimental results.

Ricoh SD-Development Technology and Pre-mix System for Image Quality

We developed a new full-color development unit, which adopted two new technologies together. The first technology named SD-development system (Stable Density development system) decreases declination of TC (toner concentration) on the development roller, to make high qualities for every printout image. The other one is a pre-mix system. The pre-mix system is to replace old developer in the development unit to fresh developer gradually during development units operating, to keep high quality printout images and to extend the developer lifetime longer. The pre-mix system which is adopted on the new development unit makes a remarkable stability with SD-development system.

Banding Mechanism Caused by Self-Excited Vibration in a Contact Development System

Previous studies on the banding mechanism have proposed various reduction methods for the electrophotographic process. The banding mechanism is generally caused by a vibration that is transmitted by the drive system and its resulting resonance. We analyzed the banding that occurred in a single-component contact development system, and it became evident that banding was caused by a self-excited vibration. The self-excited vibration model consists of the following elements: A spring element (the rubber layer of the development roller), a mass element (the development unit), and an exciting force (the friction between the development roller and the OPC drum). We also observed that the model's vibration frequency varies nonlinearly, an interesting characteristic caused by the nonlinear hardening properties of the spring. Since self-excited vibration can be prevented by stabilizing the system, we propose the use of appropriate damping components. We also statistically verified the banding reduction effect by conducting a quantitative analysis on the vibration intensity.

On Counter-Charges in Development Rollers for Electrophotography

The roles of counter-charges in toner charging and toner deposition processes for single-component development are studied by quantitative analyses of charge injection into and transport through the development rollers, taking into consideration the non-Ohmic nature of the semi-insulating overcoat layer of the rollers. The electrical requirements for the roller coatings, especially as a consequence of increased printing speed, are elucidated. Based on the findings, an ideal evaluation technique for development roller performance is suggested.

A Direct Current-Jump, Nonmagnetic, Monocomponent Electrophotographic Development System

A new monocomponent electrophotographic development system is introduced, in which nonmagnetic toner jumps the gap between the development roller and the photoreceptor only under the influence of the direct current electric fields of the latent image. This development system requires for its operation low toner adhesion, which is achieved by a patented toner formulation. Such a development system is ideally suited for a small size, low cost, color electrophotographic engine. A prototype color printer utilizing this unique development system in an image-on-Image architecture has been implemented to demonstrate its printing capabilities. Photomicrographs of print samples are shown and the scalability and extensibility of this technology are discussed.

Analysis of Imaging Density Degradation by Dynamics of Toner Charging and Mass Transfer in the Toner Development Process

In the monocomponent non-magnetic toner developing system, optimum toner charging and mass transfer are important factors to produce high quality images. Also the uniformity of the image is one of the most important properties in electrophotography. One major type of nonuniformity is the problem of image density degradation also known as ghosting. In this article this phenomenon is discussed in terms of the toner charging and mass transfer characteristics during the first and subsequent roller revolutions. It was found that although the toner charge and toner mass on the development roller surface are very important parameters they are not the only causes of the imaging density difference. It was also found that the relationship between roller surface properties and toner development efficiency are closely related to the uniformity of the printed image. It is demonstrated that the optimum development roller requires low charge retention on the roller surface and low current leakage between the supply and the development rollers. Finally the design features of a two-layered development roller are described, that provides significant improvement of image density uniformities in continuous development.

Analysis of the Tribocharging Mechanism and the Surface Properties of a Development Roller in an Electrophotographic Toner Development System

In previous work, we observed that current flows through each system part (i.e. development roller, blade, and supply roller) in normal operation during roller rotation in a mono-component development system. Measurement of these currents was shown to be useful for determining toner charging and charge transfer mechanisms. A theoretical analysis of the process is presented and by comparing this with the experimental data, it is suggested that an effective bias is generated between the doctor blade and the development roller surface due to the toner charging. By measuring the surface potential on the development roller as it was rotated, charge trapping at the development roller surface was experimentally observed. This trapped charge was released by contacting with the supply roller. It was found that the surface characteristics of the development roller considerably affected the current and the charge retention of the surface. This is shown to result in a “residual voltage” that is related to the effective bias controlling the current flow.

The Effect of Toner Additives on Mono-Component, Non-Magnetic Toner Charging using a Current Measurement Technique

In the mono-component non-magnetic toner development system, the toner is charged by contacting with the system parts, such as a doctor blade, a development roller and a supply roller. In such systems the toner charging and fluidity is conventionally controlled by the use of extra-particulate additives on the toner surface. However, the influences of the additives on the charging and fluidity of the toner are still not completely understood. In this study we investigated the effect of using sub-micron sized inorganic extra-particulates on the dynamics of the toner charging mechanism by measuring the currents flowing through each of the system parts. Development rollers having various surface properties and toners having different surface concentrations of the toner additives were prepared. By using the current measurement technique, we examined the influences of the additive on the toner charging in the development process. It is shown that the system currents and resulting toner charges are very dependent on the amount of the additives. As a result, we concluded that these additives affect not only the toner mass transport but also the charge transfer.

The Relationship Between Toner Charging and Properties of the Development Roller for Minimizing Degradation of Imaging Density

Optimum toner charging and mass transfer are important factors to produce fine images with high quality in electrophotography. Also the uniformity of the image is one of the most important properties to produce high quality printing. The charging mechanism of toners and the mechanism of toner development in the electrophotographic monocomponent laser beam printer system was studied in this article. Development rollers with various surface properties were prepared. The dynamics of toner charging were investigated by using a current measurement technique. A current was observed to flow through each system part, i.e., development roller, blade, and supply roller, during the roller rotation with toner attached on its surface. Currents and toner charge to mass ratio and the uniformity of printing image were measured for each roller. It was found that the current had a strong relationship to the roller surface properties. It was also shown that the relationship between toner charge and roller surface properties is related to the uniformity of printing image. Finally the mechanism of toner development is discussed, and the design of a high quality development roller is proposed.

Banding Mechanism Caused by Self-Excited Vibration in Contact Development System

Previous studies of the banding mechanism have proposed various reduction methods for the electrophotographic process. The banding mechanism is generally caused by vibration transmitted by the drive system and the resulting resonance. We analyzed banding that occurred in a single-component contact development system, and it became clear that banding was caused by self-excited vibration. Our self-excited vibration model consists of the following elements: a spring element (the rubber layer of the development roller), a mass element (the development unit), and an exciting force (the friction between the development roller and the OPC drum). We also observed that the model's vibration frequency varies nonlinearly, an interesting characteristic caused by the nonlinear hardening properties of the spring. Since self-excited vibration can be prevented by stabilizing the system, we propose the use of appropriate damping components. We also statistically verified the banding reduction effect by conducting quantitative analysis of vibration intensity.

Tribocharging mechanism of mono-component irregular and spherical toners in an electrophotographic development system

Toner is charged and transferred to the developing area in the development cartridge of a laser beam printer on a development roller. Optimum toner charging and mass transfer are important factors to produce fine images with high quality. The charging mechanism of toners in the electrophotographic mono-component developing system was studied in this work. Two different kinds of mono-component nonmagnetic toners were used. One was a polymerized toner (spherical), and the other was a pulverized toner (irregular). The dynamics of toner charging were investigated by using a microscopic current measurement technique. A current was observed to flow through each system part (i.e. development roller, blade and supply roller) during the roller rotation with toner attached on its surface. Development rollers with various surface properties were prepared for this study. Currents and toner charge to mass values were measured for each roller for the two different toners. It was found that the current had a strong relationship to the toner charge and mass. It was also conjectured that the current and toner charge are related to the movement of toner at the blade.

Influence of Paper Dust on Electrophotographic Images in Mono-component Impression Development Process

The fog image shaped as the fiber-type paper dust on the background occurs under the combination of the monocomponent impression development with the cleaner-less system. Occurrence of fiber-shaped fog images was studied by using two types of printers. The microscope observation of the fiber-shaped fog image indicates that many toner particles stick to the fiber-type paper dust on the photoreceptor and there are many toner particles without paper dust on the paper. The occurrence condition of the fiber-shaped fog image is different between the two different processes. The fiber-shaped fog image has periodicity in with-rotation printer, while no periodicity in counter-rotation printer. The fiber-type paper dust is collected by the development roller and this collected paper dust causes the fiber-shaped fog images in counter-rotation printer. The toner pressure pushes the fiber-type paper dust with toner out of the development room and the fibershaped fog image occurs in counter-rotation printer. The fiber-type paper dust is not caught by the development roller and kept turning with rotation of the photoreceptor in with-rotation printer. The paper dust is corona charged with positive polarity after scorotron charging device. However, it should be charged negatively, if it can not be caught by development roller. The styrene-acrylic polymerized toner can be considered to makes the paper dust tribocharged negatively at the place where the photoreceptor rubs against the development roller in with-rotation printer.

Analysis of the Surface Properties of a Development Roller for Mono-Component Toner Charging by Using a Current Measurement Technique

In the mono-component non-magnetic toner system, optimum toner charging and mass transfer are important factors to produce fine images with high quality. In previous work, we confirmed that a current flows through each system part (i.e. development roller, blade, and supply roller) during the roller rotation with toner attached on its surface. In this paper, we discuss the possible mechanism of generation of these currents in the development system. Development rollers having various surface properties were prepared for this study. It was found that the surface characteristics of the development roller considerably affected the value of the current. In particular the rate of charge decay of the roller surface strongly affected the current and also the toner charging. From these results, we propose a possible mechanism for this current generation.

Surface-Potential-Decrease Phenomenon of Photoreceptor in Electrophotographic Mono-component Impression Development Process

Surface-potential-decrease phenomenon occasionally occurs by the interaction between the development roller and the photoreceptor via toner in the non-magnetic mono-component impression development process. The surface-potential-decrease phenomenon was investigated by using polymerized styrene-acrylic resin and pulverized polyester toners. The surface-potential-decrease is much larger with the styrene-acrylic resin toner than the polyester resin toner. The surface-potential-decrease phenomenon may be originated from two causes, one is the tribocharging between toner and photoreceptor, and the other is the charge injection to the photoreceptor through the toner. The order in the triboelectric series between photoreceptor and toner resin is most important. It is preferable for the reduction of the surface-potential-decrease phenomenon and the stability of development process that the toner resin is neutral to the photoreceptor in the order of the triboelectric series.