Toner Adhesion Research Articles

Contact and Non-Contact Fusing and Fixing of Toners

Demand on material properties of toner especially viscosity and elasticity are different depending on whether fusing is accomplished by contact or non-contact means. In roll fusing (contact fusing) toner particles are subjected to pressure and heat for dwell time dependent on the roll speed and nip length. The assembly of toner particles goes through compression while the layer is being heated. The molten particles are subjected to shear which results in changes in viscosity and elasticity. Subsequently as the toner particles on the media separate from the roller, they go through stretching at fairly high rates depending on the speed of the roller. Difficulties arise when heat is applied to the media, which leads over drying of the media and causes difficulties in media handling. The pressure distribution can cause image deformation and media curling. In non-contact fusing, radiant fusing, flash fusing, microwave fusing or steam fusing, toner assembly is subjected to intense heat without external shearing or stretching. Coalescence and spreading of the toner particles take place quickly and efficiently. Adhesion of toner to the media is expected to be stronger. Non-contact fusing is contrasted with contact fusing models and compared with experiments.

Nano-Hybrid Technology – A New Tool for Improving Print Quality

Nano-scaled synthetic pigments, which are attached to the surface of an inorganic carrier pigment, are used for the production of a paper with excellent electrophotographic print quality, silk gloss, high brightness and bulk, as well as good toner adhesion. This nano-hybrid technology has the great potential to improve the quality of printing and copy papers by combining the advantageous properties of both nano-scaled and macroscopic materials. In order to address possible health concerns, a new high precision measuring device (Nano Dust Tester – NDT) was developed allowing the precise detection of possible micro- and nanoparticle emissions from paper surfaces. All papers tested with this device showed no emission of nanoparticles, whether nanohybrid technology was employed or not.

50 years of toner adhesion control in electrophotography

50 years of toner adhesion control in electrophotography

Synchrotron X-ray Microtomography: A New Tool to Characterize the Interaction Between Paper and Toner

The interaction between paper and toner depends on paper properties (roughness, paper surface, and tension) and toner properties (granulometry and chemical composition). Deepening the knowledge on fixation and adhesion of toner onto the paper substrate is crucial to improve the end-use properties of paper dedicated to electrophotographic printing. The aim of this article is to introduce and describe a new tool to visualize and analyze this interaction. Three-dimensional (3D) imaging is a key tool used to investigate such a phenomenon. For this reason, synchrotron x-ray microtomography (SXRM) was applied to characterize the toner-paper interaction in a noninvasive and nondestructive manner. To validate the feasibility of such means in a 3D context, the obtained data are compared to those obtained by traditional two-dimensional (2D) imaging systems such as optical profilometry and environmental scanning electron microscopy. SXRM emerges as a crucial tool to get a detailed characterization of the ink layer and of the ink-paper interaction. This is a powerful technique to complete studies carried out by classical means.

Thermal Behavior of Paper in Contact Fusing Technology

In dry toner electrophotography, image fixing by roller fusing technology is affected by the process parameters, and by toner and paper properties. In this type of contact fusing, the fusing energy is applied in the form of pressure and conductive heat as a function of the dwell time determined by the process speed and fusing nip width. The present study was designed to provide a deeper understanding of the behavior of paper in a modified fusing nip with controlled speed and temperature. The effects of moisture content and coating color were examined as well, and some quality factors of toner images were correlated to the thermal behavior and bulk properties of the paper samples used in the experiment. In relation to electrophotography, the objective was to explore the role of paper in the fusing stage, and to show how different paper grades contribute to image quality at different fusing speeds and temperatures, which were the main fusing parameters controlled in the experimental setting. The results show that the thermal behavior of paper is strongly related to the paper mass expressed by grammage, and the thermal behavior is less sensitive to speed with increased paper density. Gloss and toner adhesion are affected by the thermal properties of paper. The experimental design, involving a wide range of fusing variables, confirmed the need to understand on the mechanism of toner fusing and the role of toner-paper thermal interactions more deeply. The thermally controlled fusing system used in this work was found to be useful in characterizing the influence of moisture content and coating color on the thermal behavior of paper and the quality of image fixing.

Effect of medium (substrate) on toner adhesion

Adhesion of toner to a medium such as paper or plastic depends on modulus of toner paper interface that is energetic of interactions and dynamics. Energetic of interactions depend on spontaneous spreading of high surface tension liquids, while interfacial dynamics is controlled by surface friction.Surface energy is reviewed for toner and medium used in making images. Adhesion of two different solid surfaces can be predicted from their ability to induce spontaneous spreading of high surface tension liquids because interfacial forces govern the processes. The friction behavior of solid surfaces, on the other hand, is controlled by the interfacial dynamics, which has some features that are common to the sliding behavior of a liquid drop on a solid surface. In the absence hysteresis, surface energy by contact method is comparable to the indirect method by wetting. The adhesion is analyzed in terms of wetting and drop spreading. While wetting is dependent on surface energy of toner and medium, toner spreading is influenced by the ratio of surface energy to viscosity of the toner.

An Action Model of Silica Additives on the Electrification and the Adhesion of Toner

An Action Model of Silica Additives on the Electrification and the Adhesion of Toner

Electrostatic proximity force, toner adhesion, and a new electrophotographic development system

It has recently been shown that the electrostatic adhesion of a discrete distribution of charge points that are uniformly distributed around a sphere in contact with a conductive plane is larger than the conventional result, (1/4 πε 0)( Q 2/4 r 2), by (1+4/ π), where Q is the total charge and r is the radius of the spherical particle. This new electrostatic force, the 4/ π term, is due to discrete nature of charge and is called the electrostatic proximity force. This electrostatic proximity force is active at every contact point between a real, charged insulating particle and a conductive plane. By minimizing the number of contact points, the adhesion of electrophotographic toner particles to a conductive surface has been reduced by at least a factor of 10 compared to commercially available toners, allowing the viability of a new electrophotographic development system: a dc-jump, non-magnetic, monocomponent development system.

Design and Operational Characteristics of a High-Speed Contactless Fuser

Océ's VarioStream 9000 series of high-performance digital production printers features a non-contact fusing unit with unique properties. The printer's dual-engine architecture and simultaneous-duplex capability posed a challenge for the selection of the best suited fusing technology. Another challenge were the printer's changing paper movement modes due to its multi-pass operation. Monochrome printing runs with steady web motion, while dual, triple, and full-color print modes require the web to run, stop and retract in a multitude of fashions depending on the actual document content. The process speed must be adaptable to the requirements of light and heavy paper stock and special media.Traditional hot-roll fusing in combination with contact pre-heating was ruled out for the obvious reason of process incompatibility and high running cost. Contactless infrared fusing held the promise to meet the abovementioned challenges. Other pros were its durability, wide operating range, and low TCO figures. Shutter curtains allow for waste-free printing in continuous and noncontinuous printing modes, even when the web starts and stops periodically every few seconds. A web cooling section effectively suppresses hot offset on drive rolls and blocking of printed material. While the printed web runs through hot and cold process sections the respective atmospheres are kept separate by means of support rollers. If required, these can be actively engaged to smoothen the surface of the soft toner image.Process control employs pre-set parameters in start-up situations and a bunch of non-contacting sensors for infrared power and web temperature control.The fusing unit is able to process papers from 40 g/m2 to 160 g/m2 with full speed (1 m/sec) and up to 240 g/m2 with reduced speed. Toners with tailored rheological properties have been developed to achieve good balance between power consumption, process time, and web dehydration. The fusing process delivers excellent toner adhesion and crease resistance for a wide range of media.This paper also gives a breakdown of the physics involved in design and operation of the fusing system. Radiator types, print media, toner properties, and heat transfer are discussed. Engineering aspects like shutter movement, power control, safety concept round off the picture.

A Direct Current-Jump, Nonmagnetic, Monocomponent Electrophotographic Development System

A new monocomponent electrophotographic development system is introduced, in which nonmagnetic toner jumps the gap between the development roller and the photoreceptor only under the influence of the direct current electric fields of the latent image. This development system requires for its operation low toner adhesion, which is achieved by a patented toner formulation. Such a development system is ideally suited for a small size, low cost, color electrophotographic engine. A prototype color printer utilizing this unique development system in an image-on-Image architecture has been implemented to demonstrate its printing capabilities. Photomicrographs of print samples are shown and the scalability and extensibility of this technology are discussed.

Electrostatic proximity force, toner adhesion, and atomic force microscopy of insulating particles

It has recently been shown [Czarnecki and Schein, J. Electrostat. 61 (2004) 107] that the electrostatic adhesion of a discrete distribution of charge points that are symmetrically distributed around a sphere in contact with a conductive plane is larger than the conventional result, ( 1 / 4 π ε 0 )( Q 2 / 4 r 2 ), (which describes the adhesion of a spherically symmetric charge distribution to a conductive plane) by ( 1 + 4 / π ) where Q is the total charge and r is the radius of the spherical particle. This is a surprising result since it is conventionally assumed that a charged insulating particle can be modeled as a spherically symmetric charge distribution which is equivalent to a single charge point Q located in the center of the sphere. This new electrostatic force, the 4 / π term which is due to quantized nature of charge, is called the electrostatic proximity force. Previously published, poorly understood toner adhesion data and atomic force microscopy experiments with insulating particles can be accounted for using the proximity force.

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.

Microfluidic devices obtained by thermal toner transferring on glass substrate

A new process for the manufacture of microfluidic devices based on deposition of laser-printing toner on glass substrates is described. It is an alternative method to the toner on polyester film (toner-polyester) one, previously introduced. Commercial laser printers cannot print directly on glass, thus the toner must first be printed on a special paper and then transferred by heating under pressure to the glass surface. Although this procedure is more complex than the toner-polyester one, it can be repeated several times, yielding multiple toner layers. Even without special alignment equipment, up to four layers could be satisfactorily piled up. Characterization tests revealed that the toner-glass devices have similar behavior as toner-polyester ones regarding the toner layer porosity. The main advantages of the toner-glass technology are improved mechanical stability, possibility of multiple toner layers, augmented electroosmotic flow (EOF), and improved heat transfer. On the other hand, toner adhesion to glass is weaker than to polyester, which limits the device lifetime and usable liquid media. The measured EOF mobility (3.5 x 10(-4) cm2.V(-1).s(-1) for pH 7) suggests that it is mainly determined by the glass surface, being little influenced by the toner walls. Microchip electrophoresis with contactless conductivity detection and photometric detection were implemented using toner-glass devices.

The role of surface modification in digital printing on polymer‐coated packaging boards

AbstractDigital printing is increasingly being used for package printing. One of the major techniques of digital printing is dry‐toner electrophotography. This paper evaluates the printability of three different extrusion coatings used for packaging boards: low‐density polyethylene (PE‐LD), ethylene methyl acrylate (E/MA) and polyethylene terephthalate (PET). Extrusion coatings in general have an impervious, chemically inert, nonporous surface with low surface energies that cause them to be non‐receptive to bonding with toners. The most common methods used in improving the adhesion properties of polymer coatings are different surface treatments. These increase the surface energy and also provide the polar molecular groups necessary for good bonds between the toner and polymer molecules. The polymer coatings have been modified with electrical corona discharge treatment. The effects of corona on polymer surfaces and the correlation between surface modification and print quality have been evaluated. Results show that sufficiently high surface energy and surface‐charge uniformity are necessary for even print quality and toner adhesion. E/MA and PET have the required surface‐energy level without the corona treatment, but PE‐LD needs surface modification in order to succeed in the electrophotographic process. E/MA also has exceptional surface‐charge properties compared with PET and PE‐LD. Polym. Eng. Sci. 44:2052–2060, 2004. © 2004 Society of Plastics Engineers.

Experimental Verification of the Proximity Theory of Toner Adhesion

Recently a new theory of toner adhesion was suggested. In this new theory an electrostatic proximity force of adhesion is taken into account. The proximity force is due to the attraction of charges on the toner particle in close proximity to a conductive plane to their respective image charges in the conductive plane. In this paper experimental verification of this new theory is presented using a 16 μm diameter, ground toner with silica additives. The theory is fit to complete curves of the developed and residual (1) mass per unit area, (2) charge-to-mass ratio, and (3) size distribution in an electric field detachment experiment, a much more stringent test of an adhesion theory than has been published before (to the authors' knowledge). The observed adhesion and ratio of the measured toner adhesion to theory are the lowest ever observed (to the authors' knowledge).

Theory of Toner Adhesion

A theory of toner adhesion to a conductive plane is suggested which takes into account the electrostatic proximity force. The proximity force is due to the attraction of charges on the toner particle in close proximity to the conductive plane to their respective image charges. In this paper the origin of the proximity force is discussed and experimental verification of this theory of toner adhesion is presented using a 16 micron diameter, ground toner with silica additives. The theory is fit to complete curves of the development and residual mass per unit area, charge-to-mass ratio, and size distribution in an electric field detachment experiment. The observed adhesion and ratio of the measured toner adhesion to theory is the lowest every observed (to the authors' knowledge).

The Kodak Digimaster Digital Production System with MICR Option: Securing the Path to Achieve Tough Customer Requirements

Checks continue to be the leading non-cash method of payment around the world. As security and fraud concerns heighten, MICR solution manufacturers need to develop new capabilities to enable innovative security features. During development of the Digimaster system, the engineering team interviewed customers, banking experts and industry organizations to understand MICR application needs. This presentation describes what was learned and how those findings were applied to MICR features and capabilities for the Digimaster print systems.This customer centric approach resulted in:• Security and forensic printing applications, including variable microprinting• Flexibility to produce both MICR and non-MICR jobs on one print system• Image quality that meets/exceeds PIRA specifications• Exceptionally low reader/sorter reject rates exceeding all requirements worldwide• High toner adhesion to resist fraud and enable new applicationsThe customer centric product development process provided a “reality check” for product performance specifications, and verified the feature mix and performance level required by the customers.

Effects of submicrometer particulate silica addenda on the adhesion of micrometer-size particles to a polyester-composite substrate

The force needed to detach five sets of different size particles, having number-averaged diameters between 3.6 and 8.5 µm, from a composite substrate was measured using an ultracentrifuge. In addition to size variations, the asperity concentration for each size particle was adjusted by varying the silica concentration, adjusted so that the surface area concentration at each level was kept constant for the five sizes of particles. Due to the changing silica concentration and particle size, the charge per particle also varied. It was found that the detachment force appeared to be virtually independent of charge, with any correlation actually appearing slightly negative, if anything. However, the detachment force increased monotonically with increasing particle diameter and decreased monotonically with increasing silica concentration. Moreover, upon normalizing the detachment force to the particle diameter and the silica concentration to the surface area concentration of silica, it was found that the detachment force clustered into groups in which the force needed to separate the particle from the substrate depended only on the silica concentration. These results suggest that van der Waals interaction, rather than electrostatic forces, are the dominant mechanism controlling toner adhesion in this instance.

Applicability of FTIR and Raman Spectroscopic Methods to the Study of Paper—ink Interactions in Digital Prints

Vibrational spectroscopic methods are widely used in analyzing materials both in xy- and z-directions. The need to gain a deeper understanding of the print durability, especially the light fastness of ink jet prints and toner adhesion mechanisms in electrophotography, calls for analytical techniques that are capable of detecting both the physical and chemical state of prints. The sample sets used to study the applicability of various FTIR and Raman techniques to analyzing paper—ink interactions included ink jet prints with the light exposure time as a variable, and electrophotographic prints fixed at different conditions. Because of their versatility and ability to detect features from inks, toners and papers, Raman and FTIR spectroscopy proved to be suitable for studying paper-ink interactions. In addition, these methods also detected changes in the spectra due to light exposure and fixing. In examining ink jet prints on coated papers, FTIR-ATR, confocal Raman and UV Resonance Raman spectroscopy (UVRRS) turned out to be the most suitable methods for studying the light fastness of the prints. In studying the adhesion of electrophotographic prints, various FTIR methods seemed to be particularly useful because of their ability to detect hydrogen bonding.

Media/Toner Interactions in Laser Printing

According to CAP Ventures, monochrome Print-on-Demand (POD) book publishing is currently a 10 bn industry growing at a rate of 10% each year. Such POD and other electro-photographic applications demand an exceptionally high degree of print resolution as well as good toner adhesion. Controlled particle size distribution of the toners, higher print speeds, and other advances in color laser printing are also placing special demands on the media used for printing. This paper attempts to separate the effects of three different fuser roll cover materials, which impact the nip dynamics, to the print resolution and uniformity as well as the toner adhesion to the substrate. The toner adhesion was characterized by Scanning Electron Micrographs (SEM's). A model has been developed to estimate nip residence time for the fuser roll covers. As shown in the model, this parameter can be affected both by roll cover design as well as print speed. In this limited study where the print speed was held constant and the nip residence time changed only due to roll cover design, it was shown to correlate well with print resolution as measured by image analysis techniques.