Charged Toner Particles Research Articles

Technology for Electrostatic Separation of Charged Toner Particles with Different Sign by Utilizing Electrostatic Traveling Wave

The author has studied toner transport utilizing electrostatic traveling wave with high-speed photography, measurements of toner charge distributions, and numerical simulations. In this study, the author has concentrated on the toner cloud above the main transport stream. The mechanism of the toner cloud formation has been identified, and a method to separate the correct sign toner from the wrong sign toner particles utilizing the mechanism has been developed. For the fewer toner particles and a lower speed toner transport, we used high-speed photography to observe an arch-shaped toner cloud above the transport. Using a simplified model, we have found that such an arch-shaped toner cloud is formed by the effect of air-drag. On the other hand, in the development system conditions such as a higher toner concentration and a faster speed toner transport, the arch-like cloud becomes dense because of the effect of the electrostatic attraction force. The author has proposed that the cloud comprises the same number of toner particles of both signs, and has designed toner separation and re-charging system using vertical toner transporting.

Toner Display based on Electrically Induced Movement of Black and White Toner Particles

A reflection-type paper-like display based on electrically induced particle movement is proposed. The principle of the display is based on both black and white toner particles moved by applying voltage. Due to its excellent display characteristics, such as high contrast of black and white images and long image memory time, it is expected that the proposed display (called a “toner display”) will find use as electronic paper. The operation principle of the toner display is based on electrically induced movement of charged toner particles. Two types of charged particles (black and white) with opposite polarity are enclosed in the air space between two transparent electrodes. Black toner particles are attracted to the top electrode by electrostatic force across an insulating layer, to display a solid black image. The black toner particles can be transferred to the counter electrode by reversing the polarity of the electric field to display a solid white image. Experiments were carried out to examine the dependence of the display characteristics on the gap between electrodes and the mixing weight ratio of black and white particles. The display contrast and driving voltage were determined by the electrical charge of particles in the display cell. In this study, the triboelectric charges of particles in the display cell were measured using a charge-to-mass (Q/M) meter. These charges were determined to be dependent on the mixing ratio of the two types of particles. The triboelectric charging mechanism between small toner particles is also discussed.

Electrostatic Adhesion Force Measurement of the Partly Charged Toner

The electrostatic adhesion of a charged toner particle is important for the electrophotographic process. Some models for electrostatic adhesion have been suggested. One of the models, the charge patch model, hypothecates that electrostatic adhesion force is caused by charge patches in close proximity to a substrate. It has been reported that the model fits measured data, but the experimental evidence was insufficient. We examined the relation between the charged region on a toner particle and its electrostatic adhesion by experiment. The partly charged toner particles were prepared by means of a corona discharge device, and their adhesion forces were measured using an apparatus based on vibratory detachment method. As a result, it has been verified that the slight charge in the proximity region causes most of electrostatic adhesion as mentioned by the charge patch model, and the rest of charge produces a bit of electrostatic adhesion. Additionally, it is suggested that the magnitude of electrostatic adhesion force depends on the fine charge distribution in the proximity region.

Powder and Film Charging Characteristic Estimation by the Standard Carrier of Imaging Society Japan

Two-component developers which consist of toners and carriers are widely used in modern electrostatic copying machines and laser printers which utilize electrophotographic printing process. Toner charge is essential in electrophotography. The toners are triboelectrically charged by the carriers when they come in to contact. Although there are several factors which come to effect in quality in electrophotography, control of adhesion of triboelectrically charged toner particles is crucial. As such the estimation of toner electrostatic properties is very important. ISJ (The Imaging Society Japan) has proposed the standard carriers with different charging abilities for estimating toner charging property as a standard method of measurement. The electrostatic surface potentials, when the films come in to contact with standard carriers are discussed. Further, Tungsten is used for film charging to understand the charging property. The contact is carried out as carriers and Tungsten beads are rolling on the film. It is confirmed that the standard carriers proposed by the committee of ISJ show same tendency in the film charging estimation as against standard toner. It is proposed that the standard carriers are useful to estimate the charging properties of various shape material.

PRINTING ON THE NANOSCALE

ELECTRICALLY CHARGED JETS of liquid lie at the heart of a novel printing method that can be used to form complex patterns with nanoscale features from a variety of inks on nearly any type of surface, according to a team of researchers based in the U.S. and South Korea ( Nano Lett. , DOI: 10.1021/nl903495f). The study demonstrates a versatile technique for patterning surfaces with positively and negatively charged microscopic regions of arbitrary shape—an advance that may lead to new methods for fabricating electronic devices and controlling their properties. Xerography is a decades-old printing technology based on electrostatic attraction between a charge pattern “drawn” with light on a photoconducting surface (a photocopier “drum”) and oppositely charged toner particles. Efforts to increase xerography’s spatial resolution from the tens-of-micrometers range led to demonstrations in the past few years of new procedures based on scanning-probe tips and elastomeric stamps. Those techniques offer ways of prin...

Effects of Triboelectrical Charge of Toners on Display Characteristics of Toner Display

Toner Display is based on an electrical movement of charged toner particles. Two types of black and white particle charged in the different electric polarity are enclosed in the air space between two transparent electrodes. The black toners are collected to the electrode by an electrostatic force across the insulting layer to display a black image. Those toners can be put to the counter electrode by applying a reverse electric field, and white solid image is displayed.The display contrast and driving voltage depend on the electrical charge of toner particle in the display cell. In this study, the triboelectric charges of particles in the display cell were measured using Q/M meter. Those charges depend on the mixture ratio of two toners. The triboelectric charging mechanism between small toner particles was discussed.

대전입자형 디스플레이의 균등전계내 대전입자의 거동특성에 관한 연구

본 논문에서는 균일한 전계내의 대전입자의 운동특성에 대하여 연구하였다. 패널을 제작하기 위하여 양전하를 띠는 검은색 대전입자(토너)와 음전하를 띠는 노란색 대전입자(토너)를 사용하였으며, 패널구동을 위하여 오버슈트 현상이 없는 power supply로 구형펄스를 인가하였다. 또한 RT-200을 이용하여 광학특성(대조비, 시야각)을 측정하였으며, 레이저와 포토다이오드를 사용하여 응답속도를 측정하였다. 그리고 응답속도와 대조비를 통하여 대전입자의 m/q 분포를 확인하였다. 그 결과, 대전입자의 구동전압, 대조비, 응답속도는 m/g에 의해 결정되며, 패널내부에 주입된 대전입자의 m/q 분포가 동일할수록 구동특성이 향상되었다. In this paper, we studied on a characteristic of movement of charged particle in equal electric field. In order to fabricate a panel, we used positive charged toner particles of black and negative one of yellow. Panel was biased rectangle pulse without any overshoot. Also, panel's optical characteristics with contrast ratio and viewing angle is measured with RT-200. Response time was measure by using incident laser and detective photodiode. The distribution of m/q of particles by driving in panel throughout the contrast ratio and response time. As a results, driving voltage, contrast ratio, and response time are decided by m/q of charged particles and when m/q of charged particles in panel have regular distribution, it is induce improvement driving characteristics.

대전입자형 디스플레이의 응답특성

We studied driving characteristics according to the ratio of mass and charging (m/q) value for charged toner particles with black and yellow color in charged particle type display panel. After biasing rectangle pulse to the transparency electrodes of putted panel with toner particles, its response time and contrast ratio are simultaneously measured using a laser as a optical source, photodiode as a detector and reflective system. As a results, contrast ratio is largest at the shortest response time region which is different to the particle because of m/q. We proposed relational equation for response time, m/q, cell gap and biasing voltage. It has not been studied and reported to analyze the relationship of response time, biasing voltage, lumping phenomena, cell gap, and contrast ratio for toner particle type display.

Comparison of Toner Adhesion Theories

Recent measurements of toner adhesion have been reported [Dejesus et al., J. Imag. Sci. Technol. 52, 010503 (2008)] in which the ground plane was separated from the charged toner particles by a thin dielectric coating of varying thickness (0.8, 4.5, 9, and 22 μm thick), which is less than and approximately equal to the diameter of the toner particles used in the experiment, 7.1 μm. It is claimed that such data can be understood only in terms of an adhesion theory based on van der Waals adhesion. It is demonstrated in this article that the data are, in fact, consistent with the Proximity Theory of toner adhesion, which is an electrostatic theory of toner adhesion that assumes that there is electrostatic adhesion at every contact point due to the discreteness of charge. Combining this result with a comparison of theories of toner adhesion with data showing the effects on toner adhesion of changing the toner charge-to-mass ratio and the extraparticulate concentration leads to the conclusion that the Proximity Force dominates toner adhesion.

A Conceptual Model of Toner Charge Admixing

During xerographic development, charged toner particles are removed from the developer by the latent electrostatic image, and are replaced by uncharged dispensed toner particles. As a result, the total toner population in a developer contains charged incumbent particles and uncharged added particles. To maintain image quality, the latter toner particles must rapidly chargeequilibrate with the already-charged toner particles in the developer. As outlined in the present paper, a conceptual chargeadmix model based on a direct graphical analysis can provide a clear picture of toner-carrier and toner-toner charge-admixexchange processes. The model starts with the “perfect” charge admix case, and this is then used as a base for the development of a model for atypical charge admix processes. The model also describes toner charging performance from the initial developer charge-up step through the charge spectra of the final toner admix step. In this paper, predictions from the conceptual model are also reviewed for various levels of developer mixing and aging.

Momentum-Control Scavenge-less Jumping Development

A new toner-based electrographic development process is presented, which we call “Momentum-Control Scavenge-less Jumping Development” (MC-SJD). It is similar to conventional jumping development in that an AC waveform is used to drive charged toner particles across a small gap from a toned donor roll towards a photoreceptor with a latent electrostatic image. Rather than allowing toner particles to impact the photoreceptor and potentially damage any existing toned image, a four-phase waveform is used to reduce the normal component of the toner's momentum prior to its impact with the photoreceptor. The toner thus forms a nearly static cloud of charged particles near the latent image, which then gently develops onto the photoreceptor. The MC-SJD process is equally applicable to both single and dual-component development subsystems. This approach is particularly useful for image-on-image color printing architectures, but may also help improve the image quality of monochrome and conventional color prints.

Image Noise in Dry Powder Electrophotography

Through both physical experiments and detailed computer simulations, we examine some of the underlying causes of image noise in dry-powder xerography. Although examples are drawn from common electrographic technologies, such as powder-cloud jumping development, our goal is to identify and quantify the limits of toner-based printing systems without regard to any specific product-intent hardware. Understanding and modeling the principle forces between charged toner particles (and surfaces) allows us to simulate complex self-organizing structures that evolve during the development process. It is hoped that studying how these structures form, and how toner properties affect their formation, will lead to improved dry-powder printing technologies that rival lithography.

Templated Self‐Assembly of Colloidal Nanoparticles Controlled by Electrostatic Nanopatterning on a Si3N4/SiO2/Si Electret

Metal and semiconductor nanoparticles display fascinating size-dependent structural, electronic, optical, magnetic, and chemical properties, which make them promising materials to be tailored and functionalized as fundamental building blocks for emerging nanotechnology applications. Because of the strong dependence of nanoparticle properties on their quantum-scale dimensions, the synthesis of nanoparticles with a small size and shape variation is of key importance. At present, size-, shape-, composition-, and surface-chemistry-controlled nanoparticles can be synthesized by colloidal-solution methods for a wide range of materials. Furthermore, strategies have been developed in which monodispersed nanoparticles can form self-assembled, long-range nanoparticle lattices (2D and 3D) under appropriate conditions. The next important challenge for emerging nanotechnological applications (chemical and biological sensing, electronics, optoelectronics) is to perform controlled and hierarchical self-assembly of monodispersed nanoparticles from the solution phase into ordered and specifically designed nanoparticle structures immobilized on solid-surface templates. In this paper, we report an approach for controlled assembly of metal (Au) and semiconducting (CdSe/ZnS core/shell) thiol-terminated nanoparticles onto electrically patterned Si3N4/SiO2/Si (NOS) electret films with an unprecedented resolution. In the past few years, several important breakthroughs in scanning-probe-based lithographic techniques using tip-induced local electrochemical reactions of self-assembled monolayers (SAMs) or tip-induced local-transport processes, such as dip-pen nanolithography, were developed for fabricating surface templates, which can be used to assemble nanoparticles on solid supports. In these techniques, the patterning process is realized by molecular reaction or transport through a water meniscus that naturally occurs between the tip and sample under ambient conditions. Therefore, the typical resolution and writing speed of such techniques is controlled by parameters such as probe scan speed, temperature, humidity, and molecule type. Furthermore, the reaction or transport rate is limited by the reaction or ink-transport process. As a result, these types of lithographic mechanism limit the line-writing speed to the range 0.1–10 lm s and the dotwriting time to the range of a few milliseconds to tens of seconds per dot (size-dependent) under ambient conditions. Recently, electrostatic-force-based assembly of nanoparticles has been proposed as a general, precise, and reliable methodology for such purposes. In the most direct type of electrostatic-force-based assembly, charge patterns are created by scanning-probe or microcontact charging techniques onto electret materials via electronor hole-tunneling processes. As the electret materials can retain electric charge or polarization for a long time, these charge patterns can be used as templates for assembling charged or polarizable nanoparticles. The major advantage of electrostatic lithography is that, in contrast to diffusion processes, the patterning speed can be enhanced over three orders of magnitude. However, because electrostatic forces scale with surface area and particle size, nanoscale electrostatic assembly of nanoparticles is a formidable task. Xerography (a form of electrophotography) is currently one of the prevailing methods for pattern generation or replication, with ∼ 100 lm resolution. In this process, charged toner particles (with diameters in the range of several micrometers) are attracted by electrostatic-charge patterns (latent electrostatic images) created on a photosensitive electret, and the images are developed with these toner particles. Very recently, nanoscale xerography (nanoxerography) using an electrical microcontact printing process or a scanningprobe-based process was proposed as a means for nanoscale pattern generation or replication. In this work, by using an optimized electret structure (NOS dielectric stack), improved local-charging conditions under high vacuum, and chemically modified nanoparticles (5 nm thiol-terminated gold colloids, see the literature and the Experimental section for the synthesis procedure), we are able to perform selective attachment of gold colloidal nanoparticles onto the patterned electret in a toluene solution at a resolution of ∼ 30 nm. Furthermore, in our process, only a C O M M U N IC A IO N S

Electrostatic adhesion of ion and triboelectric-charged particles

The adhesion of ∼10 μm charged toner particles is of considerable importance in the electrophotographic process for copying or printing documents. If the non-electrostatic short-range adhesion force is reduced with nanoparticle surface additives, the toner adhesion is dominated by an electrostatic force. However, the measured adhesion of triboelectrically charged toner is greater than the prediction of an electrostatic image force model that assumes a uniform surface charge distribution. The enhanced electrostatic adhesion of triboelectrically charged toner is attributed to a non-uniform surface charge distribution. To provide support for this interpretation, the adhesion of ion-charged toner is of interest since a more uniform surface charge distribution is expected. Electric field detachment measurements on ion-charged toner for different charge levels show that the adhesion of ion-charged toner is indeed less than that of triboelectrically charged toner.

Charge Distribution of Corona Charged Toner Particles

Toner charge distributions in corona charged toner layers on a grounded metal plate were investigated. The charge distributions were measured through image analysis of the toner particles displaced onto a filter, depending on their charge to diameter ratio, after being blown off from the toner inlet into an electric field and dispersed. It has been confirmed that the toner charge distributions became broader by corona charging. In order to clarify the cause, dual toner layers have been formed by using different color toners, and the charge distributions at the upper and lower layers have been measured separately. The results show that the lower toner layer has a wider charge distribution than that of the upper layer. This result is attributable to the fact that the lower parts of the toner layer are covered with the upper toner layer and difficult to corona charge. The toner particles in the lower layer located at the opening of the overlapped upper layer tend to be highly corona charged, while the toner particles around the opening in the upper layer receive only a small amount of the corona charge. It has thus been shown that difference in charge distribution between the upper and lower parts of the toner layer is caused by the following mechanisms: 1) The toner particles at the lower part of the layer are shielded from corona charging ions by the upper layer; 2) The toner particles in the lower layer, which are located at the opening of the charged particles in the upper layer, receive more charging ions by concentration of the electric field; 3) The toner particles at the upper layer receive fewer charging ions because of higher electric potential owing to a longer distance from the grounded plate.

Océ's Mono Component, Magnetic, Conductive Colour Toner

Océ's Direct Imaging (DI) technology is a unique 7 colour dry-toner based printing process. The printing process is controlled by a subtle interplay between a magnetic force and an electrical force exerted on the inductively charged toner particles. Océ's DI technology therefore requires magnetizable and conductive colour toners.A major challenge was to develop colour toners that yield a sufficiently large colour gamut. Carbonyl iron has been chosen as a magnetic pigment. For a conductive coating on the toner particles fluorine doped tinoxide (FTO) is used.The FTO coating on the toner particles is completely transparent and colourless. The carbonyl iron pigment in the toner however still absorbs a significant fraction of the incident light. By using fluorescent mixtures of dyes, in addition to colour pigments, we have succeeded in attaining vivid colours and a large colour gamut.

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.

Small Copiers

Photocopies are created in a three-step process. First, light reflected from the white parts of the original is focused onto a charged printing “drum,” where it locally dissipates charge. Next, positively charged toner particles are attracted to the remaining charged areas that were dark in the original. Finally, paper is run over the drum to pick up the toner.

PIV measurement of toner particle motion in a micro-gap in the development process of electrophotography

In the development process of electrophotography, charged dielectric toner particles move in a micro-gap between the photoreceptor and the development roller to form images by the action of electrostatic force. To improve image quality, it is important to clarify the toner particle motion and the effects of the electric field on this motion. In the present study, Particle Image Velocimetry (PIV) was applied to measure the toner particle motion and the results were compared to calculated results. It was confirmed that the toner velocity increased with increasing electric field intensity, and that the measurement results agreed with the calculated results. These results indicated the usefulness of PIV in analyzing toner particle motion in the development process.

A New Technique for Measuring the Distribution of Charge-to-Mass Ratio for Toner Particles with On-Line Use

In this paper, we present a technique for measuring the value of charge-to-mass ratio in toners using a newly developed apparatus in which charged toner particles are transported above a periodic array of conductors driven by four-phase rectangular pulses. At the end of the flow path of toner particles in the transport system, parallel electrodes are set up for sensing charge-to-mass ratio. The sensed input signal is amplified by differential amplifier and is converted to digital values. By analyzing the sensed signal, the value of the ratio for the charged toner particles can be calculated. This technique can measure easily the mean value and its distribution under coditions of on-line use. We find that the distribution shows a good correspondence with the result of the E-Spart method near the peak range.