Toner Particles Research Articles

The Powder Processing Machines to Do with Grinding Toner Production and a New Technology for Toner Particle Production

The Powder Processing Machines to Do with Grinding Toner Production and a New Technology for Toner Particle Production

Simulation of Image Defect at Edges of Images in Single Component Development Systems

We perform numerical simulations of image defect at edges of solid images in non-contact single-component development systems using nonmagnetic toner. Line deletion at the leading edge of halftone images when the image is placed below a solid pattern often occurs in development systems in which the photoconductor drum surface and the development roller surface rotate in opposite directions in the development gap. This defect is examined by simulating development process in the region between the drum and the roller. The toner movement is traced by solving the equation of motions for toner particles. The Green function approach is used to calculate the electric field in the gap. An efficient numerical method is applied to integrate the Green function over charge distributions over the photoconductor with numerical stability.

Viscoelasticity in toner fusing process

Fusion and fix of images is an important process in digital printing. A base toner is mainly composed of a polymeric binder and a pigment with and without an internal lubricant for fuser roll. Necessary step in fusion of toner after particles melt is coalescence of particles. A review of models of coalescence of particles finds that rate of calescence is dependent on toner particle size, its viscoelastcity and its surface tension. Rolling contact analysis can be used to calculate temperature and shear rate during roll fusing. Temperature and strain rate dependent toner viscoelasticity (viscosity and compliance/modulus) is affected by important variables such as entanglement molecular weight and morphology of a binder polymer. Compared to fusion of toner image, fixing of an image takes place continually as the toner temperature drops. Eventually, adhesion and fixing of the toner image to a substrate is tested at ambient temperature where shear and flexural stresses dominate. Unlike fusion, the effect of molecular weight and morphology of a binder toner is different on image fix because of their effect on brittle - ductile transition and toughness (modulus) of a toner.

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.

Estimation of developed toner mass in two-component electrophotographic system by large-scale Discrete Element Method

The developing behavior of toner particles in a twocomponent development system was simulated to find out the correlation between experimental and simulated results by using large-scale Discrete Element Method (DEM). The effects of developing bias frequency or circumferential speed of photoreceptor on the developed toner mass per area (DMA) was discussed both in experimental and simulation works. The toners were adhered on the outside of latent images under the low frequency, and its mass decreased with increasing the frequency. DMA decreased with increasing circumferential speed of photoreceptor, because the toners had less chances to contact the latent image. The image was also damaged by the magnetic brush under the high speed due to an increase of the shear force. The similar tendency was observed under all conditions, and it was found that the simulation results correlate with experimental ones very well. Therefore, this simulation method is useful for the analysis of the developing behavior in electrophotographic system and the optimization or designing of this system will be possible.

Modeling of the Transient Heat Transfer in Xerographic Fusing Using a Discrete Element Approach

In This study, a computer model, based on discrete element method, is used to simulate unsteady state heat transfer at the fuser/toner and toner/coating layer interfaces during the Xerography fusing process. The model coating layers consisted of randomly arranged spherical pigment and latex particles with commercially relevant size distributions. Effects of coating characteristics, toner size, multiple toner layers, toner melting energy and toner thermal conductivity on the unsteady state heat transfer in the fusing process were investigated. Results showed that temperature variation highly depended on the toner size, toner melting energy and the fuser roll temperature. Moreover, simultaneous coupling of the stress and heat transfer indicated that the pressure exerted by fuser roll cannot significantly affect the rate of heat transfer to the toner particles.

Modelling the role of paper microstructure in electrophotography

We study how paper microstructure heterogeneity affects the electrostatic field acting on toner particles during xerographic printing. We use an efficient multigrid Poisson solver to simulate electrostatic fields. The dielectric distribution of paper is obtained either analytically or input numerically using a recently developed 3D fibre network model of paper. Simulations are used to elucidate the relative importance of paper surface, filler and porosity variations in establishing spatial variations of the electrostatic field. It is found that only long wavelength variations of surface height, bulk filler or porosity variations affect variations in electrostatic transfer forces to any relevant degree. Furthermore, we show that the effect of these long wavelength perturbations can be modelled using a new 1D effective capacitor model. When surface variations and surface filler are mixed together, we found the interesting result that mode mixing can decrease the spatial fluctuations of the electric field. Finally, using simulated 3D paper webs, which mimic the properties of laboratory handsheets, we find that to lowest order surface roughness and not formation is responsible in controlling variations of the electrostatic transfer field, a result of importance in digital printing onto stochastic printing substrates, such as commercial paper.

Toner Cloud Generation and its Supply over the Width of a Printing Area

Toner cloud generation along with controlling its movement is one of the important parameters in the development of digital printing by the toner cloud beam technique. In the experimental set-up for toner cloud generation, the conductive toner particles were sprayed at the center of a wide chamber-shaped dented electrode as the lower electrode was placed parallel with the upper electrode, leaving a small gap between them using two insulating sheets. An electrical, field was applied between the two electrodes. The toner moved up and down between the two electrodes by electrostatic force, forming the toner cloud, which propagated to both ends of the dented electrode. This research studies the toner cloud generation conditions using the wide chamber-shaped dented electrode, the slope of the nesa glass, and the slope of the system as the influencing factors that governed toner cloud generation and its movement. An increase in the applied voltage led to a faster toner cloud speed. When a greater amount of toner was applied into the dented electrode, a faster toner cloud movement was obtained. On the other hand, the toner cloud speed decreased when increasing the depth of the dented electrode. An increase of the slope of nesa glass increased the toner cloud speed. However, the toner cloud speed was not significant to the system when the slope was between 0 and 5 degrees. It was also found that the width of toner cloud decreased when the applied voltage increased. Furthermore, the two overlapped cone-shaped dented electrodes could be used for generating the toner transport to the printing system. This research also explains the possible phenomena for toner cloud generation and performance.

A Bidirectional Acid-Base Charging Model for Triboelectrification: part II. Experimental Verification by Inverse Gas Chromatography and Charging of Metal Oxides

Inverse gas chromatography (IGC) has been applied to study the surface properties of developer materials, measuring acid, base, and dispersion interactions. Model carrier and toner particles were prepared, where the toner was blended with various nanoparticulate metal oxide surface additives: Silica, titania, and alumina. Toner charging was determined with these surface additive formulations. IGC was used to characterize carrier and additive surface chemistry. Results from IGC were evaluated with respect to toner charge and to metal oxide work functions. A correlation was found between IGC-determined surface acid-base interaction parameters of the developer materials, and their work functions and triboelectric charge. Together, the IGC, work function, and charging results strongly support a work function model for developer charging, where the work function is determined by the acid and base properties of the developer components. Thus, as the ratio of the acid to base interaction parameters of the metal oxide surface additive increased, toner charge became more negative. The results are in quantitative agreement with the surface states charging model proposed in the companion paper in this series.

Analysis of the grinding of toner sheets using Vickers hardness as an index of grindability

In order to analyze the grinding behavior of toner sheets quantitatively, the relationship between Vickers hardness, Hv, and the mean particle size after grinding or the grinding throughput rate, Q, was measured and discussed. Toner sheet samples of different hardness and mechanical properties were prepared from polymer resin and carbon pigment particles by mixing, melting, and cold rolling. Toner powder was prepared from toner sheets of different hardness in a turbo or jet mill under various grinding conditions. The mean toner particle diameter after grinding under the same grinding condition increased with Hv in the case of the turbo mill. In the case of the jet mill, a strong correlation was indicated between Hv and Q when the mean particle diameter of the toner powder achieved was about 7 μm. This relationship is expressed as follows. Q = 36 H v − 0.72 − 1.15 Since the slope of the relationship between the grinding behavior and the maximum hardness was greater than that between the grinding behavior and the minimum hardness, it was suggested that the grinding behavior depended on the hard part in the toner sheets. The internal structure of the toner sheet was evaluated using a supersonic observation system; Hv was observed to be small when many detailed voids existed in the toner sheet.

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

Modelling and DEM simulations of toner behaviour in a print process

This paper describes the modelling of the toner behaviour in the development nip of the Océ Direct Imaging print process. The dynamic motion of and mechanical interactions between toner particles are explicitly modelled. The mechanical interactions are due to collisions, friction, adhesion, and electromagnetic forces. The discrete element method (DEM) is used as the simulation tool for a quantitative description of the system. The interaction rules are determined for the toner particles and the surfaces of the development rollers. The model is validated with print quality results. It is shown that it is possible to achieve quantitative agreement between DEM simulations and experimental print quality results.

Discrete Element Method Simulations of Toner Behavior in the Development Nip of the Océ Direct Imaging Print Process

This paper describes the modeling of the toner behavior in the development nip of the Oce Direct Imaging print process. The discrete element method (DEM) is used as the simulation tool for a quantitative description of the system. The interaction rules and the associated parameters are determined for the toner particles and the surfaces of the development rollers. The model is validated with print quality results. It is shown that it is possible to achieve quantitative agreement between DEM simulations and experimental print quality results.

DEM Simulations of Toner Particles with an O (N log N) Hierarchical Tree Code Algorithm

The computation time for a particle simulation where long-reaching forces, such as electrostatic forces for charged particles, have to be taken into account, rises asymptotically with O (N2). A significant reduction of computation time can be achieved by applying a tree code algorithm. The algorithm exploits the idea of grouping suitable particles to macroparticles thus reducing the number of necessary calculations within a reasonably limited error bound. Although this algorithm was developed for astronomical galaxy simulations, it can be also used for simulations of microscopical particle with finite radii. The tree code can be used for an efficient collision routine if some additional boundary conditions are taken into account. This results in an asymptotic computation time dependence of O (N log N).

Numerical Analysis of Image Defects in Single Component Magnetic Development in Electrophotography

In order to cope with image defects observed in the electrophotography using the single-component magnetic development system, a two dimensional numerical simulation has been carried out considering effects of multiple physics. The electrostatic field generated by the bias voltage applied and the electric charge on the photoreceptor and the toner particles are calculated using the finite difference method. The pressure equation is also solved by the finite difference method to obtain the flow field induced by motion of the photoreceptor and the development sleeve. The magnetic field is expressed by superposition of fields created by two-dimensional magnetic dipoles to extrapolate measured magnetic flux density on the development sleeve. Total force exerted on each toner particle by those fields are calculated and motion is tracked considering adhesion onto solid surfaces to estimate density distribution of toner particles on the photoreceptor. Two types of image defects are simulated. One is low-density area observed near a white line with dark background. The other is a phenomenon that large particles contained in the development particles are intensively developed on a non-image area close to a solid patch. Countermeasure against the image defect is also simulated.

Tribo-Charging Characteristics on Pulverized Toner Particles in Two-Component Developer

Tribo-charging characteristics on toner in a two-component developer are affected by various factors such as material component, shape, and methods of tribo-charging or measuring. A negative yellow type of pulverized toner is used as a sample, and the material is based on bisphenol A and polyester resin. Tribo-charging treatment is performed by using a developed mixing shaker with arm length of 200 mm. Charge to mass ratio q/m is measured by the E-SPART method. From the experimental results, it is shown that the q/m varies unstably and fluctuates with shaking time within 5 min, but the q/m changes gradually to a constant value of −13.5 μC/g at 20 min after 4 min for the 5 wt% of toner concentration. In order to investigate the change of the q/m, the observation via SEM on toner particles after the shaking treatment is performed. The q/m dependence on toner concentration from 1 wt% to 10 wt% in the developer is also reported.

Classification of Particle Size Utilizing Traveling Wave Field

The authors have developed five kinds of techniques on electrostatic classification of particle size utilizing the balance of the electrostatic and gravitational force. The first is an inclined plate conveyer system. A plate conveyer consisted of parallel electrodes was constructed and four-phase traveling field was applied to the electrodes to transport particles on the conveyer. Particles were classified with size under the voltage application of appropriate frequency based on the feature that small particles were transported upward against the gravity but large particles were apt to fall down. The second technique was an inclined tube conveyer system. The principle is common with that of the inclined plate system. The third technique utilizes a circular electrostatic conveyer similar with the mass spectroscopy. The forth is also circular but utilizes the feature that a locus of the small particle is high compared to that of the large particle. The last is the combination of the linear conveyer and an electrostatic separation roller located at the end of the conveyer. Small particles were attached onto the roller charged by a charger roller. These techniques are expected to be utilized to the classification of toner and carrier particles used in electrophotography.

Color Toner Display Based on Control of Particle Movement

Toner Display is based on an electrical movement of charged particles. Two types of black toner and white particles charged in the different electric polarity are enclosed between two electrodes. The particle movement is controlled by the external electric field applied between two transparent electrodes. The toner is collected to the electrode by an electrostatic force across the insulating layer to display a black image. The toners can be put back to the counter electrode by applying a reverse electric field, and white solid image is displayed. We have studied on the movement of three color particles independently to display color image in Toner Display. Two positively charged color particles with different amount of charge to mass ratio and negatively charged white particles were enclosed in the toner display cell. Yellow, cyan and white images were displayed by an application of voltage.

448 進行波電界による粒子の粒度分別

The authors have developed four kinds of techniques on electrostatic classification of particle size utilizing the balance of the electrostatic and gravitational force. The first is an inclined plate conveyer system. The plate conveyer consisted of parallel electrodes. Four-phase traveling field is applied to the electrodes to transport particles. The second is an inclined tube conveyer system. The third is a vortex electrode conveyer system. The last is the combination of the plate conveyer and an electrostatic separation roller. These techniques are expected to be utilized to the classification of toner and carrier particles used in electrophotography.

Treated Colloidal Silica Particles for Toner Formulations

Surface modified silica particles are used as external additives to toners to improve free flow, to reduce agglomeration of toner particles, and to modify the tribo-charging characteristics of the final toner formulation. In many of the new toner formulations, large diameter spherical silica particles, rather than the traditional aggregated fumed silicas, are needed to give the required performance characteristics to the toner. In fact, large (order 100 nm) spherical silica particles have been cited as an essential additive in preventing agglomeration in new toner formulations [1].The manufacture of large treated spherical silica particles presents a variety of chemistry and processing challenges. Both the reaction and drying conditions during manufacture must be carefully controlled to produce powders with uniform treatment and minimal aggregation. In this paper, we shall discuss the effects of the treatment chemistry and the base silica particle size on toner tribo-charging and humidity stability and toner free flow for a model toner system.