Xerographic Printing Research Articles

UV Watermarking of Images in Clustered Dot Scenarios

Digital Watermarking of printed images is an important capability for many applications. Visually detecting the watermark through, e.g. UV illumination, enables the watermark use in uncontrolled environments. In our previous work, UV watermarking was proposed for in dispersed dot scenarios (assuming the use of standard colorants). This talk describes the generalization of that concept to clustered dot scenarios thereby allowing the creation on standard printing equipment, such as offset or xerographic printing.

The synthesis of styrene acrylate emulsion and its application in xerographic paper

Abstract During xerographic printing processes, the electric charge properties of the paper surface are essential to obtain effective toner transfer and high image quality. Surface and volume resistance are indispensable to the accumulation of the surface charge and different resistance values generate different electrical fields with optical drum, and have a significant effect on toner transfer efficiency. In this paper, surface sizing was investigated to improve the surface properties for better toner transfer and image quality. Styrene acrylate emulsion (SAE) latex was successfully synthesized and fully characterized with a Fourier transform infrared (FT-IR) spectrometer, a laser particle analyzer and a scanning electron microscope (SEM). The results showed that under the conditions of emulsifier dosage at 3 wt%, initiator concentration at 0.5 wt% and the reaction temperature at 80°C, the monomer conversion can reach 80%. The effects of various factors including initiator dosage, emulsifier dosage and monomer ratio on the sizing performance were studied. The effects of different ratios of SAE to starch on surface and volume resistance of paper were also systematically investigated. The differences in electric properties of various paper samples were quantified and their influence on paper-toner adhesion and print quality was clarified. Relationships between electrical properties of paper and paper-toner adhesion force, and thus print quality were established. Strategies to improve printing performance through effective control of paper electrical properties were also developed. It is concluded that the best printing quality and toner adhesion were achieved when the ratio of SAE to starch is between 1:10 and 2:10.

Lattice-Based $n$-Point Time-Sequential Sampling and Two-Stage Process Control for Maintaining Tone Consistency of Xerographic Processes

This paper proposes: 1) a lattice based time-sequential sampling approach that requires the printing and measuring of the smallest number of tonal samples to characterize the high-dimensional tone reproduction curve (TRC) at each print cycle, and 2) based on this characterization, the design of a two-stage control strategy to maintain tone consistency of a xerographic printing process. The printer's TRC maps the desired tones to the actual printed tones and it is high dimensional due to the large number of desired tones. To avoid using many sensors, the measurement of the TRC is achieved by sampling it time-sequentially and by reconstructing the TRC from the samples via a Kalman filter. In time-sequential sampling, only a few distinct <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$n$</tex></formula> tones are printed and measured at each print cycle. Using a lattice-theoretic framework, an optimal time-sequential sampling sequence with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$n=1$</tex></formula> is designed. This is then extended to the case of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$n&gt;1$</tex></formula> to enable the tradeoff between sampling time and sampling resources. With the reconstructed time-varying TRC, a two-stage control strategy uses both the physical xerographic and the image processing processes to compensate for the TRC variations from the desired TRC. Simulations and experiments show that the proposed TRC stabilization system is effective for practical implementation. By stabilizing all the cyan, magenta and yellow primaries of the color xerographic print system, color consistency can be maintained. Furthermore, the proposed time-sequential sampling approach with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$n=1$</tex></formula> exceeds the capability of conventional three-fixed-point sampling (light, middle, and dark tones) approach while requiring three times fewer samples.

Technical Evolution of Ceramic Tile Printing

Ceramic tile decorating techniques have evolved significantly in recent years. Digital inkjet printing technology has enabled digital systems to be used for the direct decoration of ceramic tiles, revolutionizing ceramic tile decoration and providing many advantages over traditional decoration techniques. It was the formulation of inks with soluble and vitrifiable stains that allowed inkjet printing technology to be introduced into ceramic tile decoration. The incorporation of milled inorganic pigments into the inks broadened the available color palette. However, the colloidal instability of these inks and the constraints of the printing heads themselves made it necessary to reduce pigment particle size, thus limiting color saturation and the color gamut. In order to increase color saturation and obtain a set of pigmented inks with colors more closely resembling CMYK colors, pigments with larger particle sizes need to be used. Indeed, other digital decorating techniques, such as xerography, allow larger particle sizes to be used, while also providing the advantages associated with digital decoration. However, the implementation of this technique for ceramic tile decoration requires the development of appropriate ceramic toners and adaptation of printing machines. This article reviews the technical evolution of ceramic tile printing and describes the development of a prototype, based on xerographic printing, that is able to print ceramic tiles directly and provides greater color intensity and a wider color gamut.

Effects of Nanoparticle Coating on the Adhesion of Emulsion Aggregation Toner Particles

Toner is a key material for the xerographic printing and copying industry. Compared to conventional pulverized toner particles, emulsion aggregation (EA) toner particles could adhere more strongly to substrates and their property distributions are narrower because of their near-perfect spherical shape and higher surface free energy. However, in general, uncoated EA toner is more difficult to transfer and clean during printing/copying processes for the same reasons. Nanoparticle additives could be used as control agents to reduce the toner particle–substrate adhesion. In order to optimize their adhesion and handling performances, an accurate adhesion characterization of the toner particles coated with different levels of additives is required. In current study, two non-contact adhesion characterization techniques based on acoustic air-coupled excitation and ultrasonic base excitation are presented. Their use for the adhesion characterization of individual bare toner particles with an average diameter of 6.0 μm on silicon substrates, and their silica nanoparticle coated variants with a surface area coverage (SAC) of 50% is demonstrated. The techniques are based on the detection of the resonance frequencies of rocking motion of micro-spheres. The out-of-plane transient displacement responses of the rocking particles are captured by a laser interferometer, and the natural frequencies of particle rocking motion obtained from transient displacements at the top of particles and the substrate are related to the strength of the adhesion bond. It is reported that the work of adhesion values of the 50% SAC-coated toner on silicon substrates are almost an order of magnitude lower than those for the bare ones.

Modeling and Control of a Hybrid Two-Component Development Process for Xerography

Development is one of the six key steps in xerographic printing processes. Under certain printing conditions, the “deveopability” of the toner particles tends to degrade resulting in a loss of image quality. Existing process controls have limited authority in compensating for this degradation, and, ultimately, a service operation may be required to install fresh toner. From a customer perspective, this machine maintenance results in productivity loss and added cost, both of which need to be minimized. In this paper, a control oriented model that characterizes “developability loss” is derived from an experimentally validated comprehensive statistical model. The resulting model considers the stress case of printing “low area coverage” documents (e.g., text pages) in a low relative humidity environment, and it maps the development voltage and toner dispensing rate actuators to the developed toner mass per unit area, which is the sensed output and is also used as a surrogate for print quality. Under these operating conditions, system analysis shows that developability loss is unavoidable. Given this result, a constrained time optimal control problem is formulated to determine the dispensing strategy to maximize the printer operating time while maintaining acceptable developability. Numerical solution shows that for the stress operating condition leading to developability loss, the optimal dispensing strategy increased the operating time by 170% compared with a conventional dispensing strategy.

On the relations between color, gloss, and surface texture in injection‐molded plastics

AbstractThe relation between color and gloss of injection‐molded plastic specimens was evaluated by means of a 45°/0° geometry spectrophotometer and a glossmeter. The specimens were plaques having one smooth, glossy field and one rougher, textured region made of two different polymeric materials (acrylonitrile‐butadiene‐styrene and polypropylene) in a range of colors. A significant influence of the lightness L* of the specimens on the measured gloss of the textured field, with a low gloss appearance, was found. This can probably be attributed to a contribution from bulk scattering, which is linked to the reflectance from within the specimen. The influence of texture on the measured color of the plaques was assessed by evaluating the color difference between the smooth field and the more textured area on the specimens. When the surface was textured, the color changed; in general it became lighter and less saturated. The magnitude of the change depended on the color of the material. The darker the material was, the larger was the increase in lightness L* as the surface became rougher. The shift in chroma C* was determined not only by the saturation but also by the lightness of the specimens. Darker specimens exhibited a larger decrease in chroma when the surface was textured. The change in the measured color caused by increasing the surface roughness could be predicted in a satisfactory manner using a model developed for xerographic printing paper. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 291–298, 2009

Direct Color Consistency Control for Xerographic Printing

Direct Color Consistency Control for Xerographic Printing

Xerographic Printing System Performance Optimization by Toner Throughput Control

For two component xerographic development systems the toner concentration and the average toner residence time in the developer sump are desired to be within optimal ranges for acceptable image quality. The toner concentration and the average toner residence time are coupled such that independent ranges are not typically achievable, and so a tradeoff must be managed. Also the required toner for any given job is highly variable and not known well in advance, yet significantly impacts the two aforementioned parameters. In this paper the authors propose and demonstrate a model predictive control design framework to optimally manage toner throughput to achieve performance objectives.

Discrete element modeling of the transient heat transfer and toner fusing process in the Xerographic printing of coated papers

In this study, a computer model based on discrete element method is employed to simulate the unsteady state heat transfer from the fuser roll to the toner and coating layer during the Xerography printing of coated papers. 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, toner thermal conductivity, coating layer thermal conductivity, and fuser roll temperature and pressure were investigated. Iso-thermal contours of fusing time were generated to demonstrate the relative importance of different fusing conditions and toner properties. Simulation results showed that temperature variation highly depended on the toner size, toner melting energy and the fuser roll temperature. Moreover, simultaneous coupling of the compressive stress and heat transfer indicated that the pressure exerted by the fuser roll did not significantly affect the rate of heat transfer.

Predictive Design of Paper Microstructure for Xerographic Printing

The authors present a new approach for modeling toner transfer in xerographic printing. Our formalism combines a new three-dimensional (3D) stochastic fiber network model of paper, a 3D model of electrostatic, and contact adhesion forces acting on toner particles in xerographic printing. Our modeling platform allows the authors to study the relative importance of paper surface and mass density variations in establishing the electrostatic and contact adhesion forces crucial in controlling toner transfer efficiency during xerography. Simulations of xerographic printing are used to show that state of compression of the paper surface in the print nip is critical in controlling the distribution of toner onto paper. This is quantified by showing how the paper surface controls the distribution of both the electrostatic and contact adhesion forces that draw toner to paper. In contrast, paper formation, a traditional index of paper quality in the paper industry, is found to play a negligible role as a predictive measure of print uniformity in xerographic printing. Our simulation results are validated against new xerographic printing experiments of black toner onto laboratory handsheets.

The role of paper-nip interactions on electrostatic toner transfer forces in Xerographic printing

We present a new model that uses a 3D stochastic fibre networks to simulate the role of paper structure and paper-nip interactions on the process of toner transfer in Xerographic printing. Our simulations show that the surface properties of paper under deformation in the print nip are critical in establishing the electrostatic field responsible for transferring toner to paper. When the spatial distributions of simulated electrostatic transfer fields – established in the presence of paper surfaces in a state of z-compression – are compared to the distribution of toner experimentally printed onto laboratory handsheet, good agreement is found.

Xerographic Printing System Performance Optimization by Toner Throughput Control

For two component xerographic development systems the toner concentration and the average toner residence time in the developer sump are desired to be within optimal ranges for acceptable image quality. The toner concentration and the average toner residence time are coupled such that independent ranges are not typically achievable and so a tradeoff must be managed. Also the required toner for any given job is highly variable and not known well in advance, yet significantly impacts the two aforementioned parameters. In this paper we propose and demonstrate a model predictive control design framework to optimally manage toner throughput to achieve performance objectives.

Occupational vocal cord dysfunction due to exposure to wood dust and xerographic toner

Vocal cord dysfunction is a poorly understood entity that is often misdiagnosed as asthma. Both irritant and non-irritant vocal cord dysfunction have been described. This report presents two cases of irritant vocal cord dysfunction secondary to specific environmental exposure, the first to iroko and western red cedar wood (a carpenter) and the second to xerographic printing toner (a secretary). Several tests were performed, including chest radiographs, measurements of total serum immunoglobulin E, skin prick tests with common pneumoallergens (as well as iroko and western red cedar in the first case), pulmonary function studies, methacholine challenge testing, specific inhalation challenge performed with suspected agents in a single-blinded fashion, and peak expiratory flow testing and fiberoptic rhinolaryngoscopy (in case 1). During the specific inhalation challenge, the patients showed dysphonia, chest tightness, inspiratory stridor, and flattening of the inspiratory limb of the maximum flow-volume loop in spirometry, with no significant decreases in the level of forced expiratory volume in 1 second; fiberoptic rhinolaryngoscopy confirmed the diagnosis of vocal cord dysfunction in case 1. It is important to know that agents that can cause occupational asthma can also cause vocal cord dysfunction. The mechanisms by which these agents produce vocal cord dysfunction are unknown. The differences in the clinical presentation of the patients described relative to the reported cases suggest that more than one pathophysiological mechanism may be implicated in the genesis of this entity.

Using Time-Sequential Sampling to Stabilize the Color and Tone Reproduction Functions of a Xerographic Printing Process

Tone and color reproduction functions (TRC and CRC) characterize how a printer maps a desired tone or color into the actual printed output. TRC/CRC ideally, should be identity maps to achieve tone and color consistency. Whereas the TRC/CRC is potentially high or infinite dimensional, typically, only a small number of tone/color test patches for sensing can be printed and measured at a time and only a small number of actuators are available for control. Time-sequential sampling is proposed to address the sensing limitation issue in order to enable the time varying TRC or CRC to be reconstructed based on a small number of samples. A periodic Kalman filtering approach is employed for the reconstruction. A curve-fitting TRC stabilization controller based on linear quadratic (LQ) control with integral dynamics is proposed to address the actuation limitation issue. Two classic time-sequential sampling sequences are compared based on their spectral aliasing properties, and the reconstruction operations of the periodic Kalman filter is analyzed using Floquet theory. Simulations and experiments show that the proposed TRC/CRC stabilization system can be implemented practically and the control performance with one time-sequential sampled sensor is nearly as effective as using full sampling using sixteen fixed sensors

Relationship between Paper Properties and Fuser Oil Uptake in a High-speed Digital Xerographic Printing Fuser

The fuser roll in high-speed xerographic printers is typically coated with a silicon-based oil to facilitate clean splitting of the fused image and paper as it exits the fusing nip. If oil uptake by paper is excessive, the fuser roll will become insufficiently coated with oil. Consequently, both image quality and fuser roll life will be negatively impacted. A variety of commercial papers were characterized and evaluated for their oil uptake performance. Using partial least-squares regression, key paper properties correlated with oil uptake were identified. Surface energy of paper was found to have the strongest correlation with oil uptake. Furthermore, based on contact mechanic theories, a contact area index (CI) was used to describe the degree of contact between paper and the fuser roll at the nip. A positive correlation between oil uptake and CI suggests that roughness and stiffness also have significant influences on oil uptake.

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.

The Relationship Between Paper Properties and Fuser Oil Uptake in High-Speed Digital Xerographic Printing

Fusing plays a vital role in achieving high resolution print quality in high-speed digital xerographic printing. The fuser roll is typically coated with a release agent so as to facilitate clean splitting of the fused image and paper as it exits the fusing nip. If oil uptake by paper is excessive, a fuser oil depletion problem will develop with time and the fuser roll will become insufficiently coated with oil. In this study, the oil uptake performance of a wide range of commercial papers was evaluated using a prototype highspeed xerographic fuser. The key paper properties that control oil uptake are identified using a partial least squares regression model. A mechanistic view of how these paper properties interact to affect oil uptake is explored in terms of the wetting of oil on paper and in terms of a contact area index (CI). Surface free energy of paper was found to be the dominant property in describing the wetting of oil on paper. CI, based on theory from contact mechanics, is used to describe the degree of contact between paper and the fuser roll at the nip. A positive correlation between CI and oil uptake suggests that roughness and bending stiffness have significant influences on oil uptake.

Modelling dielectric heterogeneity in electrophotography

We introduce a continuum model of electrophotographic printing of paper and other disordered composite films. The model allows simulation of any dielectric distribution within a toner transfer gap. It is used to elucidate the role of mass density and paper thickness variations on toner transfer efficiency in Xerographic printing. Our simulations show that spatial variations in inorganic filler distribution within paper as well as paper thickness variations will strongly affect toner transfer uniformity by controlling the point-to-point variation of the local dielectric constant of paper. This variation will manifest itself as a mottle in toned images. It is specifically shown that paper thickness variations in paper lead to toner density variation on the scale of 1 mm, similar to those found in Xerographic printing of commercial papers.

Robust stabilization of tone reproduction curves for the xerographic printing process

The problem of stabilizing a single color tone reproduction curve of a xerographic printing engine is considered. This problem is critical to ensure high-fidelity color printing. The control system uses a small number of actuators and a small number of measurements to stabilize the potentially high-dimensional tone reproduction curve. The goal is to minimize the overall least squares deviation of the tone reproduction curve from the ideal nominal one in the face of disturbances like material changes, temperature, humidity, and uncertainty in the system description. The control design consists of the steps of (1) determining a robust optimally performing static controller and (2) realizing the controller that utilizes only past measurements. Numerical simulations and experiments validate the efficacy of the controller.