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Electrophotography is a digital, on-demand, dry, and page printing technique that operates based on toner particles of electronic materials using an electrostatic force and generates an electrical circuit via distribution of the toner particles. We developed a 10 μ m linewidth resolution with various electronic materials, including conductors, semiconductors, and insulators, without any chemical pretreatments on the substrate films, while a 5 μ m resolution was also possible for limited materials. The electrical resistivity of the printed Ag–Ni after an intense pulse light sintering was comparable to that of commercial indium tin oxide transparent films. [ABSTRACT FROM AUTHOR]

Electrophotography is a digital, on-demand, dry, and page printing technique that operates based on toner particles of electronic materials using an electrostatic force and generates an electrical circuit via distribution of the toner particles. We developed a 10 μm linewidth resolution with various electronic materials, including conductors, semiconductors, and insulators, without any chemical pretreatments on the substrate films, while a 5 μm resolution was also possible for limited materials. The electrical resistivity of the printed Ag–Ni after an intense pulse light sintering was comparable to that of commercial indium tin oxide transparent films.

Deinking waste paper is done in various ways, and research on newer methods is also being done. Traditional deinking methods to remove ink from waste printing papers have a relatively high efficiency compared to contact methods, but in non-contact printing such as electrophotographic printing (LaserJet printers and photocopiers) due to Mixing of the ink with the paper texture during the stabilization of the ink with the help of high heat, the traditional deinking methods are less efficient and it is necessary to use newer methods. In this research, enzymatic deinking of office waste paper was done by a commercial cellulase enzyme in a neutral environment. 15 tests were conducted, and optical and printing properties including the paper were investigated. By measuring the reflection before and after printing and measuring the print density after printing, it was determined that the printability of deinked paper is within the desired range. Eric's number was 128 ppm for sample number 8 and 138 ppm for sample number 12, which has decreased compared to the control sample with an Eric number of 571 ppm. Measuring the reflection before and after printing and measuring the print density after printing, show that the printability of decomposed ink paper is in the desired range. [ABSTRACT FROM AUTHOR]

Electrophotography is affected by several parameters, including printing machines and paper type, which determine the final quality of reproduction. For the investigation of those effects, tests were done on the three types of electrophotography printing machines and eight types of uncoated paper with different properties of weight, surface roughness, whiteness, brightness and opacity. Samples were printed with cyan, magenta, yellow and black toner under the standard, identical conditions. The assessment of standard print quality parameter (optical density) was done using spectrodensitometer Techkon Spectro Dens. At the same time, the paper substrates were characterized using the atomic force microscopy (AFM) as well as by spectrophotometric measurements (X Rite Eye-One, i1). Obtained results showed that the reproducibility significantly depends on the type of printing machine rather than optical and mechanical properties of paper.

In addition to printing techniques, there are various characteristics that affect the quality of printed products. Most frequently questioned features are line, dot, and text reproduction. In this paper it is investigated how different substrates, printed by the same printing technique, affect the quality parameters of printed samples. Print quality includes the process of obtaining the desired reproductions of color and image elements, important parameters of print quality are the quality of lines and dots, and the feature of the substrate that is significant for this work is the roughness of the substrate. This paper presents the testing of three different materials on to which the test form was printed by electrophotography, as a digital printing technique. The tests are based on analysis of line, dot and text reproduction, as well as analysis of the roughness of the substrate on samples printed in black. Based on the obtained results it can be concluded that the substrate affects the quality of printed products

In this study, electrophotographic printing and inkjet printing systems were applied to some commercial A4 office papers and their effects on print quality were determined. It is to evaluate the print quality by determining the test parameters that measure the print quality by applying electrophotographic printing and inkjet printing systems to some commercial office papers that have determined the surface properties and optical properties supplied from the market. Print quality was measured by testing with parameters such as delta gloss 60°, print lightness, print chroma, print density. As a result of the tests determined for print quality; print density values were low in A4 office papers with high roughness and porosity values, and the specular gloss values of the samples decreased in both printing applications. In electrophotographic printing; it was determined that darker colors formed with print lightness parameter, and the color scale increases in two-sided printing with print chroma values. It was determined that the color scale of print chroma values increased in two-sided prints. It was determined that mostly some commercial office papers were positively affected by printing on one side in inkjet printing and by printing on two-sided in electrophotographic printing. [ABSTRACT FROM AUTHOR]

Multi-material additive manufacturing (AM) attempts to utilize the full benefits of complex part production with a comprehensive and complementary material spectrum. In this context, this research article presents new processing strategies in the field of polymer- and metal-based multi-material AM. The investigation highlights the current progress in powder-based multi-material AM based on three successfully utilized technological approaches: additive and formative manufacturing of hybrid metal parts with locally adapted and tailored properties, material-efficient AM of multi-material polymer parts through electrophotography, and the implementation of UV-curable thermosets within the laser-based powder bed fusion of plastics. Owing to the complex requirements for the mechanical testing of multi-material parts with an emphasis on the transition area, this research targets an experimental shear testing set-up as a universal method for both metal- and polymer-based processes. The method was selected based on the common need of all technologies for the sufficient characterization of the bonding behavior between the individual materials. [ABSTRACT FROM AUTHOR]

In this study, the effects of the lacquer applied to the printing materials which were printed by electrophotographic printing method on printing quality were investigated. In practice, printing materials with the same weight and different optical properties were used and the study was carried out in three stages. The optical and physical properties of the printing materials used in the first part were determined, in the second part, the printing of these materials by electrophotographic printing method and printability tests were performed. In the third chapter, matte and glossy lacquers were applied to these printed materials and printability tests were repeated. As a result of the study, it was observed that the application of gloss and matte lacquer caused a decrease in the printing density values and also the application of matte lacquer caused a decrease in the gloss values.

Featured Application: Toner materials for electrophotography. It is empirically known that titanium dioxide nanoparticles stabilize the contact and frictional charge of the host polymers to which they are added. However, the mechanism for the stabilization process has not yet been elucidated. In this study, polyester films doped with titanium dioxide nanoparticles of different crystalline forms were triboelectrically charged and the effect of humidity on their charging characteristics was subsequently investigated to elucidate the charge stabilization mechanism. Our first finding was that the rutile-, rutile–anatase mixed crystal (P25)-, and amorphous-dominant-type titanium dioxide nanoparticles reduced the sensitivity of the films to humidity (humidity dependence), while the anatase-type titanium dioxide enhanced the humidity dependence. This difference in action was explained by associating it with the different water adsorption forms on the major crystalline surface of each titanium dioxide type. The second finding was that doping with titanium dioxide nanoparticles, particularly rutile and P25 nanoparticles, reduced fluctuations in the amount of tribocharges of the polyester film. This crystalline-form-dependent difference in action was considered to be based on the depth of the electron traps involved in each titanium dioxide type. The above two findings have allowed us to propose the first mechanism of tribocharge stabilization by titanium dioxide. [ABSTRACT FROM AUTHOR]

In traditional deinking process, large amounts of chemicals are required which makes these methods expensive and polluting. Also, application of sustainable material implies the use of green processes to reduce waste and pollution. Green enzymatic deinking processes are alternatives to those technologies that have negative effects on the environment. In this work, we applied response surface methodology for deinking the electrophotography-printed paper based on a systematic experimental pattern. The individual and interactive effects of enzymatic deinking parameters including time, temperature, and enzyme dosage on the handsheet properties were investigated. Different analyses were carried out to determine the best process conditions of enzymatic deinking to optimize the handsheet properties (i.e., tensile, burst, whiteness, and brightness). The obtained responses of an oven-dried fiber at 45 min, 43 °C and the enzyme concentration of 1 mg/15 g were 12.44, 0.65, 72.20, and 87 for tensile strength, burst strength, whiteness, and brightness, respectively. Measuring the optical density of the deinked handset after printing showed that the printability of the deinked paper is in the desired range. [ABSTRACT FROM AUTHOR]

It is empirically known that titanium dioxide nanoparticles stabilize the contact and frictional charge of the host polymers to which they are added. However, the mechanism for the stabilization process has not yet been elucidated. In this study, polyester films doped with titanium dioxide nanoparticles of different crystalline forms were triboelectrically charged and the effect of humidity on their charging characteristics was subsequently investigated to elucidate the charge stabilization mechanism. Our first finding was that the rutile-, rutile–anatase mixed crystal (P25)-, and amorphous-dominant-type titanium dioxide nanoparticles reduced the sensitivity of the films to humidity (humidity dependence), while the anatase-type titanium dioxide enhanced the humidity dependence. This difference in action was explained by associating it with the different water adsorption forms on the major crystalline surface of each titanium dioxide type. The second finding was that doping with titanium dioxide nanoparticles, particularly rutile and P25 nanoparticles, reduced fluctuations in the amount of tribocharges of the polyester film. This crystalline-form-dependent difference in action was considered to be based on the depth of the electron traps involved in each titanium dioxide type. The above two findings have allowed us to propose the first mechanism of tribocharge stabilization by titanium dioxide.

In this study the prints were made on paper substrates, which were thought as map substrate alternatives, with 3 different surface properties at 1200 dpi by using the electrophotographic printing system. Color and gloss values of the samples were determined both before and after exposure to light for a period of 42 hours to determine the light fastness of the substrate and the print on it. The studies revealed that after the light fastness tests (i) the width of the color universe of the papers with matte surfaces is more than that of the papers with glossy surfaces, (ii) the loss of brightness of woodfree paper is higher than that of the other paper samples and (iii) the print chroma values obtained in woodfree paper is lower than those of the coated surfaces. Moreover, (iv) the delta E 00 {E_{00}} measurements revealed that all paper samples experienced different color losses in different colors, and the most significant differences in these color losses were in magenta and black. [ABSTRACT FROM AUTHOR]

Generating multimaterial parts, reaching higher efficiency in powder consumption, and decoupling of powder application behavior from powder properties such as powder flowability are key aspects for using electrophotographic powder application (EPA) in laser-based powder bed fusion of polymers (PBF-LB/P). Moreover, EPA allows the layer thickness to be reduced from around 100–150 μm, depending on respective particle size distribution, in the case of conventional doctor blade or roller-based powder application methods to the diameter of the applied polymer particles (typically between 50 and 130 μm). This can have positive effects on the interlayer connection and, therefore, the mechanical properties of the additively manufactured part because less powder volume has to be fused with the already generated underlying part. Moreover, due to the above-mentioned independence of EPA from powder flowability, the addition of flow aids, such as nano silica, can be reduced to a minimum or even avoided completely. This is the first comprehensive study on resulting properties of parts generated by PBF-LB/P using EPA taking into account both the reduction in layer thickness and reduced addition of flow aids. In addition to improving mechanical properties of generated parts, the independence of powder flowability, in particular, offers the possibility of qualifying currently unsuitable materials for PBF-LB/P. For this purpose, besides widely employed polyamide 12 (PA12), a polypropylene (PP) powder is used that is very difficult to process in conventional PBF-LB/P and can only be applied there with the help of flow aids. [ABSTRACT FROM AUTHOR]

In the late 1980s, the commercialization of digital reproduction technology led copy art in a new direction, ushering in a new era of events with global impact and significance. Among these events was the second International Electrography and Copy Art Biennial, held in Valencia, Spain, in October 1988, which commemorated the 50th anniversary of the first electrophotographic copy. This landmark occasion marked the beginning of a new and prosperous digital era that would continue throughout the following decade and was spearheaded by artists of the so-called third generation. [ABSTRACT FROM AUTHOR]

High efficiency in terms of powder consumption and the ability to generate multi-material parts using additive manufacturing are key features of the electrophotographic powder application for laser-based powder bed fusion of polymers (PBF-LB/P). The reliable deposition of powder particles onto the build platform is one decisive process step. The aim is to achieve a high degree of coverage and, at the same time, maintain an accurate contour of the deposited powder layer. In addition to the use of a suitable electrical transfer field, which has already been investigated, targeted vibration excitation offers enormous potential for improvement. For this purpose, a mechanical simulation model is set up in this study, which is subsequently validated experimentally. By using the knowledge gained from the simulation, for example with regard to suitable vibration modes, the powder deposition has been significantly improved. [ABSTRACT FROM AUTHOR]

Nowadays, the paper industry supplies its required fibers either from primary fibers, including wood and plants, or waste papers, called secondary fibers. One of the most challenging recycling processes is deinking of papers digitally printed with electrophotographic ink. In order to produce optically high-quality paper from recycled waste papers, deinking step is required at the desired levels. In this work, the environmentally friendly green enzymatic deinking of printed paper was modeled and optimized via an innovative approach called artificial intelligence method. The effect of treatment temperature, treatment time, and enzyme dosage on mechanical properties (tensile and burst strengths) as well as optical properties (whiteness and brightness) of handsheet was investigated. The developed code can appropriately learn the non-linear behavior of deinking process, and make decisions according to the pattern constructed intelligently. Finally, multi-objective optimization at the specified treatment temperature, treatment time, and enzyme dosage was performed to identify the best conditions for enzyme-deinked handsheet (maximized mechanical and optical properties). [ABSTRACT FROM AUTHOR]

Magnetic flux measurements of toners can aid in the rapid differentiation of toner‐printed specimens in the context of investigations of forgeries or alterations of printed documents. However, some variables that may impact magnetic flux measurements, including hysteresis effects, are not currently well understood. This study assessed the impact of hysteresis and other induction spatial effects on magnetic flux measurements of toners analyzing five toner‐printed samples produced from different devices. The samples were printed with controlled grids of square, rectangular, and elongated rectangular blocks with the same area. Thirty measurements were conducted on each sample, on each grid type. The measurements were repeated in planes of rotation 90°, 180°, and 270° counter to this original position. The values obtained for the square grids were evaluated using one‐way ANOVA to assess the presence and impact of hysteresis effects. The values obtained for the rectangular grids were compared with those obtained for the square grids using a two‐way ANOVA to determine potential induction current orientation effects. The results of both one‐way and two‐way ANOVA were significant with p < 0.05, indicating that both hysteresis effects and induction current spatial effects contribute significantly to variations in magnetic flux measurements. Results confirmed that sensor orientation is an important factor that must be accounted for in method protocols for the measurement of magnetic flux of toners. Controlling these variables is a step forward toward the development of a reliable screening method to be deployed in the context of investigations of document forgeries or alterations. [ABSTRACT FROM AUTHOR]

Functional dye is a new term in the field of dye chemistry which has been specifically designed for hightechnology applications such as solar cells, photochromic dyes, liquid crystal, electrophotography, fluorescent sensors and photodynamic therapy. BODIPY and its derivatives as organic fluorophores have optical properties and can be used as potential sensors in various applications for biotechnological, industrial and medical purposes. In this research, a group of a new fluorescent indicators based on BODIPY structure were designed which have been composed from two seven-membered rings including Al or B atoms that has been connected with methine bridge complexed with NH2 or PH2 center. The geometries, optical properties and electronic structures of various designed molecules were studied using time-dependent density functional theory (TDDFT). The results of the calculations showed that the new designed structures are stable and highly optically active with considerable quantum yield (Φ) absorption and emission as if is promising candidates for hi-tech different applications. [ABSTRACT FROM AUTHOR]

The electric-field dependence of photocarrier generation efficiency has been investigated in several different types of organic photoconductor for electrophotography to elucidate the controlling factors of light-to-electrical energy conversion. The rate-determining step in generating photocarriers has been considered to be the charge transfer between two neighboring molecules. Overall photocarrier generation efficiency has been determined using the charge transfer velocity at the ratedetermining step as a function of electric-field-dependent activation energy, which is influenced by the symmetry factor α and the energy gap ΔE. The formula used successfully fits the experimental data for different types of organic photoconductor over a wide field strengths range. From the fitting results of high-sensitivity photoconductors, the zero-field activation energy is small and the reactant lifetime is long. In addition, ΔE is zero, which implies that the hole-electron interaction in the reactant is negligible at the rate-determining step. In contrast, for low-sensitivity photoconductors, the zero-field activation energy is large and the reactant lifetime is short; however, ΔE<0 and α>0.5, which suggest that the hole-electron interaction is not negligible. Consequently, the proposed formula well explains the electric-field dependence of photocarrier generation efficiency on the basis of its controlling factors. [ABSTRACT FROM AUTHOR]

Atmospheric pressure corona discharges are used in electrophotographic (EP) printing technologies for charging imaging surfaces such as photoconductors. A typical corona discharge consists of a wire (or wire array) biased with a few hundred volts of dc plus a few kV of ac voltage. An electric discharge is produced around the corona wire from which electrons drift towards and charge the underlying dielectric surface. The surface charging reduces the voltage drop across the gap between the corona wire and the dielectric surface, which then terminates the discharge, as in a dielectric barrier discharge. In printing applications, this underlying surface is continuously moving throughout the charging process. For example, previously charged surfaces, which had reduced the local electric field and terminated the local discharge, are translated out of the field of view and are replaced with uncharged surface. The uncharged surface produces a rebound in the electric field in the vicinity of the corona wire which in turn results in re-ignition of the discharge. The discharge, so reignited, is then asymmetric. We found that in the idealized corona charging system we investigated, a negatively dc biased corona blade with a dielectric covered ground electrode, the discharge is initially sustained by electron impact ionization from the bulk plasma and then dominated by ionization from sheath accelerated secondary electrons. Depending on the speed of the underlying surface, the periodic re-ignition of the discharge can produce an oscillatory charging pattern on the moving surface. [ABSTRACT FROM AUTHOR]

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Gray balance is one of the key issues of color balance and color appearance adjustment during printing. It takes into account the overlap of two or more colorants to achieve a visually neutral tone. It works in parallel with the adjustment of the main color channels. In electrophotography, the setting of color channels separately is usually carried out using tone reproduction curves. However, this traditional approach does not take into account the effect of changes in shades caused by their overlapping, We previously suggested using gradation trajectories (an analogue of tone reproduction curves in CIE Lab space) as an alternative paradigm for color channel adjustment. Further, we expanded the idea to the gradation surfaces as an expression of binary overlays. We proposed both analytic and discrete approaches to the computation of gradation trajectories and surfaces. The computations use the mathematical apparatus of differential geometry of spatial curves and surfaces. Discretization uses color quantization in digital printing devices and means that color coordinates are considered as continuous functions of filling a discrete raster cell with dyes. The color space metric is determined by the value of the CIE dE color difference. As gradation trajectories, we apply the discrete type of geodesic lines on the gradation surfaces of the corresponding binaries. In this work, we suggest using gradation surfaces in discrete form as a mathematical model of double dye overlays to adjust the gray balance in electrophotography. [ABSTRACT FROM AUTHOR]

To realize high quality electrophotography, it is important to clarify the influence of the design parameters in a charging roller (CR) system on the output image on the paper. We first analyzed the parameters related to the direct current (dc) bias CR system, and consequently confirmed micro jitter generation as a printing quality indicator for varying CR resistance and the surface roughness of the CR elastic layer. It turned out that the micro jitters were correspondingly generated for the chosen representative parameters, and therefore, the analyses can be used as a design platform to prepare an optimum dc CR system. [ABSTRACT FROM AUTHOR]

The temperature-dependence of the electrical and dielectric properties of paper substrates was studied using experimental papers with different NaCl contents, different thicknesses, and different grammages. Physical processes related to the charging potential, charge decay rate, conductivity, dielectric constant, and dielectric loss of papers are dependent on thermal energy, and this dependence on temperature can be described by exponential expressions. The ion content of paper not only determines the level of these properties at a given temperature, as expected but also influences their temperature-dependence. Frequency analysis of the dielectric loss confirms that new structures are formed in paper by the addition of NaCl. The results may be applicable to the design of materials and equipment, e.g., for the electrophotographic printing processes. [ABSTRACT FROM AUTHOR]

Print quality is very important for every printing technique. It depends on many different quality attributes. This research included analysis of macro non-uniformities and line reproduction. 16 different paper substrates printed by electrophotographic process were analyzed. They were separated in two groups: coated and uncoated papers. Analysis of macro non-uniformity showed that print mottle has lower values when printed on coated papers than on uncoated papers. Line reproduction analysis showed that the toner spreaded, during melting and fixation, on line edges for both types of paper. According to these results it can be concluded that paper substrate affects the macro non-uniformity and line reproduction, thus overall print quality.

Understanding electrification is particularly important in materials science since the use of charged particles, e.g., the electrophotographic printer with toner particles, is one of the most successful applications of electrification. However, the charge generation mechanism still remains unclear due to the lack of an appropriate method for evaluating individual fine particles. In this study, we describe an approach for determining the charge of a single toner particle that uses electron holography in combination with a shielding technique. Two long-standing problems in holographic studies—namely, perturbation of the reference electron wave and unwanted charging by illumination—have been overcome by introducing two types of shields in a microscope. Using this method, the amount of charge on a single toner particle was determined, and the surface charge distribution was found to be inhomogeneous. Furthermore, an in situ observation of triboelectricity was conducted inside the microscope. [ABSTRACT FROM AUTHOR]

The electric potential close to a boundary between two dielectric material layers reflects the geometry of such an interface. The local variations arise from the combination of material parameters and from the nature of the inhomogeneity. Here, the arising electric field is considered for both a sinusoidally varying boundary and for a “rough,” Gaussian test case. We discuss the applicability of a one-dimensional model with the varying layer thickness as a parameter and the generic scaling of the results. As an application we consider the effect of paper roughness on toner transfer in electrophotographic printing. [ABSTRACT FROM AUTHOR]

Last generation printing equipment is easily used nowadays in committing crime, to create highquality counterfeits and forgeries. Forensic experts participate actively in the fight against criminality by identifying new ways of examining a document. For this purpose, this method of identifying electrophotographic printers was studied and implemented. This was done by examining the grid made by the yellow dots on the printed documents. A large majority of electro-photographic printer manufacturers embed a yellow dot code of various shapes in colour printouts. This code contains data which allow us to determine the identification series of the printer which was used, the date of printing or other information. [ABSTRACT FROM AUTHOR]

Until today, the electrophotographic transfer of toner powders has been applied successfully in common printing technology for many years. Utilizing the electrophotographic principle for the transfer of polymer powders in the context of additive manufacturing can give a variety of advantages like e.g. the possibility of generating multi-material components or a reduced consumption of powder. Here, the multiple depositions of powder particle-layers via electrostatic forces to create 3D objects have turned out to be a major challenge. Therefore, a new strategy based on the usage of a grounded transfer grid is examined. Due to its positioning above the generated layers, it makes the powder deposition independent of the already produced part height. For improving the particle transfer, geometrical properties of the grid are analyzed with respect to their influence on the efficiency of the powder deposition. Here, particular attention is paid to the manipulation of the electric transfer field, which is applied for accelerating the charged powder particles. The aim is to enhance the coverage and dimensional accuracy of the deposited powder layers by finding a new transfer structure. [ABSTRACT FROM AUTHOR]

Highlights • Stereospecific synthesis of polymers containing pendant carbazolyl groups. • Influence of polymer stereochemistry on photophysical behaviour. • Applications of stereoregular polymers containing pendant carbazolyl groups in light-emitting diodes. Abstract The most recent results concerning the stereospecific synthesis and the microstructural, chemico-physical and optical characterization of polymers containing pendant carbazolyl groups are reviewed for the first time. Stereoregular poly(N -alkenyl-carbazole)s, poly(4-(Ncarbazolyl) methyl styrene), poly(ω-(N -carbazolyl)alkyl acrylate)s and poly(ω-(N -carbazolyl)alkyl metacrylate)s are considered in this review, with a particular focus on the influence of polymer stereochemistry on photophysical behavior. Potential applications of these materials in light-emitting diodes (LEDs), electrochromic devices, electrophotography and holographic memories are also discussed. Among these, we show the appealing results of our experiments, concerning the color tuning in organic LEDs based on poly(N -pentenyl-carbazole) by means of the polymer chain stereoregularity. [ABSTRACT FROM AUTHOR]

Starting in 1973, researchers at the Xerox Palo Alto Research Center (PARC) built the first networked workstation platform (Alto and Ethernet) and a suite of applications and services to explore office automation. Separate interactive tools allowed people to create and edit different sorts of document content, which were then merged onto pages using Press files, a page description file format. [ABSTRACT FROM AUTHOR]

Presents a study on electrophotographic discharge of cadmium sulfide explained by surface-depletion discharge model. Introduction to the use of corona-charged photoconductor; Description of the depletion-discharge model; Results and analysis.

Presents a study that examined the photocarrier generation mechanism in an organic photoreceptor for laser beam printers. Background on exitons; Information on azo pigments used in photoreceptors for electrophotography; Mechanism of photoinduced discharge in photoreceptors.

Presents information on a study which described a basic concept on the molecular design using thiophenylene moieties and polyimides, including the electrophotographic properties of polyimides in relation to the crystallinities. Methods; Results; Discussion.

Describes a photoreceptor charging method by rubbing with magnetic conductive particles. Details on the charging mechanism of particle charging; Depth of the trapped charges; Description of the proposed electrophotographic printing technology.

Presents information on a study which described a mathematical method based on first principles to predict the behavior of the magnetic brush in the development zone of an electrophotographic process. Steps in making a print by electrophotography; Experimental measurements; Results of calculations; Conclusions.