Photoreceptor Drum Research Articles

Statics and Dynamics of Carrier Particles in Two-Component Magnetic Development System in Electrophotography

The authors used a simple model and a prototype machine to study statics and dynamics of a magnetic brush in a two-component development system in electrophotography. In the model experiment, the authors measured the normal and tangential forces of the brush formed from a chain of magnetic carrier particles when it comes in contact with the photoreceptor to clarify the relationship between the tangential friction force and the diameter of the carrier particles, magnetic flux density, and the length of the brush. The tangential friction force increased with the magnetic flux density and decreased with an increase in the length of the brush; however, the total force was unaffected by the diameter of the carrier particles. On the other hand, numerical calculations performed using an improved distinct element method revealed that although the total force was not affected by the diameter of the carrier particles, the individual differential force acting on the magnetic particles of the chain was small, and the density of the carrier particles that come in contact with the photoreceptor drum was high when the size of the particles was small. In the investigation carried out using the prototype machine, it was found that the magnetic brush formed in the development area is inclined in a direction parallel to the magnetic field and that the chains are crushed by the photoreceptor drum. Although the total pressure applied on the photoreceptor was almost independent of the diameter of the carrier particles, the differential force exerted by individual chains is small and distributes dense when the size of the particles is small; on the other hand, it is large and distributes rough when the size of the particles is large as predicted by the model investigation. This result suggests that small carrier particles are advantageous in preventing any disturbances in the images developed on the photoreceptor. The effects of the development gap and the thickness of the laver of supplied carrier particles have also been evaluated.

361 レーザプリンタの2成分磁気ブラシ現像系におけるキャリア粒子の動力学

We have studied dynamics of magnetic brushes in the two-component development system of electrophotography by the numerical simulation with an improved Distinct Element Method (DEM) and experimental observation with a high-speed microscope camera. Two-dimensional magnetic field was calculated by superposing measured discrete magnetic flux densities on a development sleeve. It has been calculated and observed that magnetic brushes grow up in the development area inclining in parallel in the direction of the magnetic field and they are crushed by a photoreceptor drum. It has been evaluated that although the total pressure applied to the photoreceptor is almost irrelevant to the diameter of carrier particles, differential force applied by individual chain is dense and small with small particles but rough and large with large particles. This suggests that small carrier particles are preferable to prevent disturbance of developed toner particles on the photoreceptor.

3804 静電インクジェット現象を利用したマイクロ成膜(S59-1 柔軟媒体ハンドリングと画像形成システム(1),21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

An organic photoreceptor (OPC) drum for electrophotography is mainly manufactured by the dipcoating technology. However, large amount of coating solution is necessary for the dipcoating. In this report, we purposed a new coating method for the carrier generation layer of the OPC utilizing a liquid atomization phenomenon of the electrostatic inkjet system. Atomization of the carrier generation solution had been controlled by the applied voltage and the gap, and we have succeeded to coat a uniform film in 10 × 10 mm.

Cross-Linked Naphthalene Bisimide “E-Barrier” Layer Compositions Using Blocked Isocyanate Chemistry

High-quality electrophotographic applications demand a photoreceptor drum that is “perfect” in many aspects, such as being defect-free—almost to the submicrometer level—environmentally insensitive, and possessing a welldefined photosensitivity that matches the electrophotographic rendering process.Managing hole injection from the conductive substrate is critical to prevent “background and breakdown spots” on the final prints. Typical solutions require a hole-injection barrier layer. These layers need to be environmentally insensitive, resistant to the charge generation layer coating solutions, while allowing transport of photogenerated electrons to the conductive layer to prevent cycling charge buildup.This work describes the development of naphthalene bisimide hole-injection e-barrier layer compositions that can be both coated thick and uniform, and thermally cross-linked. These coating solutions are very stable at normal coating temperature and suitable for the dip coating process. The blocked isocyanate cross-linkers are activated after coating at a temperature above 120 °C. We have developed an offline method to study the kinetics of the cross-linking reaction using the GC headspace analysis technique for optimizing the crosslinked network.

Formation of Magnetic Particle Chains in Ultra High Magnetic Field

Magnetic particles form chain-like clusters in a magnetic field. These chains are used to supply toner particles on a photoreceptor drum in the two-component magnetic brush development system used for high-speed and/or color laser printers. Characteristics of chains influence image quality of the printer. Although experiments had been performed in low magnetic field, characteristics in the high magnetic field are necessary to investigate actual performance of the system and thus an experiment on the chain formation has been performed in the ultra high magnetic field created by a superconducting magnet. It has been clarified that the chain length first increased and then decreased in accordance with the increase of the magnetic field. The result has been confirmed by a numerical calculation with the Distinct Element Method that included the contact force between particles, the gravitational force, and the magnetic force due to the field created by the coil and adjacent magnetized particles. Lastly, it has been discussed that the static stability of chain was determined by a minimization principle of the potential energy that consists of the gravitational and magnetic potential energy.

Aqueous Surface-Smoothing Layer Compositions for High-Quality Photoreceptors

High-quality electrophotographic applications demand a photoreceptor drum that is “perfect” in many aspects, such as being defect-free—almost to the submicrometer level, environmentally insensitive, and possessing a well-defined photosensitivity that matches the electrophotographic rendering process. The surface quality of the substrate strongly influences the quality of the critical charge-generation layer. Every minute defect of the substrate surface is magnified in that layer. Almost always, a substrate surface-smoothing layer is required. This work describes the development of aqueous, environmentally green compositions for thick, uniform, defect-free, transparent, and conductive surface-smoothing layers.

Oscillation of a Cleaning Blade in a Laser Printer (1st Report, Observation of Phenomena in an Actual Machine and Consideration of Oscillation Mechanism)

A mechanism of a cleaning blade squeaking noise due to a friction between a photoreceptor drum and a cleaning blade in a laser printer is presented in this paper. Although this problem has been known for many years, the details of oscillation mechanism is not clarified, so we have not found out the fundamental solution yet. In order to clarify the mechanism, at first, we took notice of the peculiar features of this noise in an actual machine. Then, we proposed a theoretical model based on a multi freedom coupled model, which can explain the above features of this noise. Finally, we clarified that the oscillation is one of a coupled mode flutter.

Development of a New a-Si Photoreceptor Drum by DC Plasma CVD

Development of a New a-Si Photoreceptor Drum by DC Plasma CVD

Improvement of Charging Performance of Corona Charger in Electrophotography by Irradiating Ultrasonic Wave to Surrounding Region of Corona Electrode

In order to improve the performance of a corona charger in charging the photoreceptor in electrophotography, the effect of an ultrasonic wave on the process was investigated experimentally. An ultrasonic wave of 28 kHz was supplied from an ultrasonic generator at five different strengths ranging from 0 to 50 W. Instead of a photoreceptor drum, a coated aluminum drum containing a thin insulator film was used in this study. It was confirmed that the ultrasonic wave had a marked effect on the charging performance of the corona charger; namely, the ultrasonic wave increased the charge density on the insulator layer of the drum. The charge density depended on the magnitude of the ultrasonic wave and the distance between the ultrasonic generator and the wire electrode. These results were attributed to the activation of the corona discharge by the ultrasonic wave and the blowing off of the suppression gas near the corona wire electrode by the ultrasonic wave.

Development of a New a-Si Photoreceptor Drum by DC Plasma CVD

We developed a new pulse DC plasma CVD layer deposition process for a-Si photoreceptor drums instead of the ordinary high frequency 13.56 MHz plasma process. This has made the layer deposition process speed 2 times faster, minimized by-product powder generation and improved the surface smoothness of the a-Si drum. Through these improvements, we realized production cost reduction. This makes it easier to offer small diameter a-Si drums for tandem color printers, where growth in demand is predicted.

261 電子写真の磁性一成分現像システムにおけるトナー像の帯電量と三次元形状

For the purpose of analyzing the magnetic single-component development process of electrophotography, we measured 3D-figures and charge density of toner images on a photoreceptor drum and an OHP sheet with a co-focal laser focus displacement sensor and a Faraday cage. The results were as follows: (1) In a toner image on the photoreceptor, it was confirmed that mountain-like chain structures were formed parallel with development direction. (2) In a toner solid image, charge density in the center area is lager than that in the edge and volume density in the edge is lager than that in the center area.

Effect of Hot Airflow on Charging Performance of Corona Charger in Electrophotography

To improve the performance of a corona charger for charging the photoreceptor in an electrophotographic system, hot airflow was introduced to the corona charger. The hot airflow increased the surface voltage on the insulator layer of the photoreceptor drum and the charging speed. The printing speed was 35% better when a hot air blower was used than when an ordinary corona discharger was used.

A Consideration about Oscillation Mechanism of a Cleaning Blade

A mechanism of a cleaning blade squeaking due to the friction between the photoreceptor drum and the blade in a copy machine is presented in this paper. Although this problem has been known for many years, the details of oscillation mechanism are not clarified, so we have not found out the fundamental solution yet. Here, in order to clarify this oscillation mechanism, we took notice of the feature of the oscillation that the frequency changed discretely with a normal force of the blade. In other words, we found out that the oscillation is caused by couple of immanent modes in the cleaning blade, and it was dependent on the friction force which mode became unstable coupling. As a result, we confirmed that the discrete change of oscillation frequency was explained by the unstable coupled modes of the cleaning blade.

回転体に対向接触する弾性ブレードの自励振動発生メカニズムに関する考察(柔軟媒体ハンドリング/画像形成機器,IIP2004 情報・知能・精密機器部門講演会)

A mechanism of leaning blade squeaking due to the friction between the photoreceptor drum and the blade in a copy machine are presented. Although this problem has been known for many years, the details of oscillation mechanism are not clarified, so we have not found out the fundamental solution method yet. Here, in order to clarify this oscillation mechanism, we took notice of the feature of the oscillation that the frequency changed discretely with a normal force of the blade. In other words, we found out that the oscillation is caused by couple of immanent modes in the cleaning blade, and it was, dependent on a friction force which mode became unstable coupling. As a result, we confirmed that the discrete change of oscillation frequency was explained by the unstable coupled modes of the cleaning blade.

The influence of particle charge and roughness on particle–substrate adhesion

In the electrophotographic process, charged toner particles are transferred from the bulk to the photoreceptor drum and from there to the paper. In high performance printing systems, more than 1000 pages/min are printed, equivalent to the transfer of more than 10 10 particles/min. The key to understand and to improve the printing system is particle–particle and particle–substrate interactions, respectively. We study the adhesion forces by means of atomic force microscopy (AFM) measurements complemented by centrifugal detachment measurements in an ultracentrifuge. The interpretation of AFM measurements requires careful calibration of the used cantilevers together with a sound statistical analysis. Particle charges have been determined from force–displacement curves. Silicon wafers, polished and PVD-coated aluminum substrates with tailored roughness are chosen as model materials. Spherical, smooth polystyrene and specially prepared alumina particles as well as rugged toner particles of irregular shape are investigated. We proceed from well-defined model systems (flat smooth substrate interacting with spherical particles) to technical systems where rugged particles adhere to rough substrates. The adhesion forces consist of electrostatic and of non-electrostatic (e.g. van der Waals forces) components. We show how the influence of electrostatic forces relative to the van der Waals forces can be controlled.

Wear Characteristics and Cleaning Ability of Cleaning Blades

The cleaning performance (lifetime of cleaning blades and cleaning ability) of a leading type blade cleaning system for electro-photography is examined theoretically and experimentally from the viewpoint of tribology and rheology. Wear characteristics and cleaning ability of cleaning blades are found to be described well by a model which takes into account stick–slip behavior of the cleaning blade against a photoreceptor surface. A theoretical analysis of fatigue wear which takes into account vibration loss tangent (or rebound resilience), applied load on the cleaning blade on the photoreceptor surface, and friction coefficient between the blade edge and the photoreceptor surface, agrees well with results of accelerated wear experiments and lifetime evaluation tests using copying machines on the market. The cleaning blade edge once stretched by the photoreceptor surface during the stick process returns to its original position gradually with a characteristic relaxation time during the slip process and forces remaining toner particles to move against the rotating direction of photoreceptor drum. Therefore, toner particles have a greater possibility of going through the blade nip during the slip process. The theoretical analysis and the experimental results suggest that cleaning ability is proportional to the reciprocal of the relaxation time.

2738 電子写真における転写ユニットでの紙速度予測方法

A numerical method that predictr the paper velociry at the roller transfer unit in an electrophotographic system is presented including the roller slip characteristics and the tension in thepaper. The roller slip characteristics are derived from the measurement of the relative velocity behveen the roller and a paper under an erternalforce. The paper feeding simulation is used to calculate the tension in the paper among the registration rollers, the roller transfer unit and the fuser rollers. The paper velociry at the roller transfer unit is predicted solving the equilibrium equations between the traction given by the transfer roller and the photoreceptor drum and the tension in the paper. The predicted velocities agree well with thosefrom e.periments, which is based on the time interval sensing ofthe pattem oflines printed onpapers.

A Numerical Method Predicting the Paper Velocity at the Roller Transfer Unit in an Electrophotographic System

A numerical method that predicts the paper velocity at the roller transfer unit in an electrophotographic system is presented including the roller slip characteristics and the tension in the paper. The roller slip characteristics are derived from the measurement of the relative velocity between the roller and a paper under an external force. The paper feeding simulation is used to calculate the tension in the paper among the registration rollers, the roller transfer unit and the fuser rollers. The paper velocity at the roller transfer unit is predicted solving the equilibrium equation between the tractions given by the transfer roller and the photoreceptor drum and the tensions in the paper. The predicted velocities agree well with those from experiments, which is based on the time interval sensing of the pattern of lines printed on papers.

電子写真現像プロセスにおけるトナー粒子微小隙間飛翔解析

In development process of electrophotography, charged toner particles move to form image by the electrostatic force in a micro-gap between photoreceptor drum and development roller. To improve image quality and prevent image defects, it is important to clarify the motion of toner particles and to study the effects of electric field. In the present study, PIV system is used to measure the velocity of toner particles and the measured results were discussed comparing with the calculated electric field. It was confirmed that the velocity of toner particles increased with increasing electric field intensity. These results show the usefulness of PIV system to measure the motion of toner particles in development process.

Image-on-Image Color Process Using Liquid Toner

The image-on-image (IOI) color process, in which color images are superimposed on a single photoreceptor drum and then transferred to the paper at once, possesses capabilities for realizing a high speed, high quality, and compact color printer. However, in the IOI processes using dry toners, there are unavoidable problems that make it difficult to obtain high quality color images. The authors found that, using liquid toners, these issues are completely resolved and an excellent color process is realized. Development characteristics and color image qualities are compared between IOI processes using dry and liquid toners. The results of theoretical analyses agree with these experimental data.