Xerographic Toner Research Articles

Closable Valves and Channels for Polymeric Microfluidic Devices.

This study explores three unique approaches for closing valves and channels within microfluidic systems, specifically multilayer, centrifugally driven polymeric devices. Precise control over the cessation of liquid movement is achieved through either the introduction of expanding polyurethane foam, the application of direct contact heating, or the redeposition of xerographic toner via chloroform solvation and evaporation. Each of these techniques modifies the substrate of the microdevice in a different way. All three are effective at closing a previously open fluidic pathway after a desired unit operation has taken place, i.e., sample metering, chemical reaction, or analytical measurement. Closing previously open valves and channels imparts stringent fluidic control—preventing backflow, maintaining pressurized chambers within the microdevice, and facilitating sample fractionation without cross-contamination. As such, a variety of microfluidic bioanalytical systems would benefit from the integration of these valving approaches.

Exploration of Factors to Influence Solid Density Based on the Xerographic Toner Digital Printing Field

With the rapid development of the printing industry, relying on its flexibility and advantage for short-run printing, the use of digital printing in various areas of the market becomes more widely. Digital print quality evaluation and control is particularly important. Among them, the solid density is an important indicator of print quality evaluation. Using different digital printing methods, the factors to influence the density is different. In this paper, two factors that affect xerographic toner solid density were discussed base on the principle of electrostatic imaging and toner transfer and fusing process. Experiments analyzed different transfer supply voltage conditions on CMYK four-color solid density; and the fusing temperature on CMYK four-color solid density. The results showed that: transfer supply voltage and fusing temperature are influential factors on the four-color solid density.

The synergistic effect of mixed xerographic toner agglomeration

Agglomeration phenomena of two mixed xerographic toners were investigated using 1-octadecanol as the agglomeration agent and a cationic surfactant as the co-agglomeration agent. One toner carrying no surface charge agglomerated well under most conditions, while the other toner carrying a negative surface charge performed worse. It was found that when mixing these two toners together during pulping and when using 1-octadecanol as the agglomeration agent alone, there was an additive effect on agglomeration. On the other hand, addition of a small amount of cationic surfactant dramatically enhanced the mixed toner agglomeration efficiency and generated an obvious synergistic effect. The particle number after agglomeration was significantly reduced, and the particle size was greatly increased compared to the single toner agglomeration. The optimal amount of the cationic surfactant was close to the optimal cationic surfactant demand of the negatively charged toner. Based on these findings it can be recommended that the cationic surfactant should be added during agglomeration of the mixed office waste paper, and its optimal dosage needs to be chosen to reach the best performance.

The effect of cationic surfactants on xerographic toner agglomeration under alkaline pulping condition

1-octadecanol is known to be a highly effective agglomerating agent for nonimpact-printing toners. However, it was found that some xerographic toners did not agglomerate under alkaline conditions. The effect of alkali on the agglomeration was studied with two different toners, one carrying no surface charge and one carrying a negative charge. The effect of the addition of a cationic surfactant on the agglomeration under neutral and alkaline conditions was then studied using two different cationic surfactants. It was found that both toners agglomerated better under neutral conditions than under alkaline conditions. The toner carrying no surface charge agglomerated much better than the toner carrying a negative charge under either alkaline or neutral conditions. The addition of a cationic surfactant greatly improved the agglomeration of the toner carrying a negative charge but had relatively small effect on that of the toner carrying no surface charge. It is recommended that agglomeration of mixed office waste with 1-octadecanol should be carried out under neutral conditions with the addition of a small amount of a cationic surfactant.

Investigation on solubility of polymeric binder of xerographic toner and de-inking by emulsion process

An investigation of xerography wastepaper recycling by estimating the solubility parameter of toner to select a suitable de-inking agent has been accomplished in aqueous media. The major de-inking agents used in this study were composed of combinations of a suitable organic solvent and a surfactant. This research focused on the addition of water insoluble solvents, with their solubility parameters closely proximate to the polymeric binders in toner, to assist its initial dissolution. Subsequently, the addition of surfactant to the mixture promotes the formation of an emulsion. The ink could then be easily washed away from the pulp aqueous slurry. The most suitable de-inking agent has been identified to be the mixture of naphthalene (20%), isoamyl acetate (80%) and surfactant. At 20 °C, styrene–acrylate copolymer binder in the toner was emulsified in the pulp aqueous slurry to form a stable emulsion with a particle size of 527 nm. After repeated water washings of the pulp, the ink specks on the paper were washed away as a water emulsion and the speck of the recycled paper was lowered from 5760 ppm to less than 10 ppm. In the meantime, the brightness of the final de-inked pulp was improved from 80% GE to 85% GE, which is almost identical to the brightness of virgin unprinted paper (86% GE).

The Effect of Toner Resin on Triboelectric Aging

The base resin for a xerographic toner is typically selected on the basis of its melt rheological properties, especially for highspeed printer applications where imaging fusing performance requires a “low-melt” toner. However, a base resin may also strongly affect the triboelectric aging performance of a xerographic developer. For example, the interaction of a toner charge control additive (CCA) with toner and carrier surfaces will depend on CCA / toner base resin compatibility. Similarly, residual chemical species from the resin polymerization process may act as carrier “poisons” (and thereby degrade or enhance the tribo-charging ability of a carrier). Additionally, a toner base resin can also affect xerographic image performance (via the image density: image development potential relationship), and thereby affect imaging latitude and imaging process control.

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.

Effect of Metal Oxide Surface Additives on Xerographic Toner Powder Flow Cohesion and Cohesion Aging Stability

A systematic approach was used to select metal oxides with varying composition, surface chemistry and particle size, which were then blended on toner particles as surface additives. The Hosokawa Powder Flow tester was used to study the toner cohesion, both as initially blended, and with aggressive toner aging. The toner powder flow cohesion and aging was studied for two different base toner particles, based on a styrene/acrylate resin and a polyester resin. It is shown that selection of the metal oxide size, oxide type and chemistry is important to ensure stable flow with aging time.

Measurement of Cohesive Force Distributions in Powder Flow: The Effect of Metal Oxide Surface Additives on Xerographic Toner

The Hosokawa powder tester has been used for many years to determine cohesion of bulk powders, including toner. For the first time a method is demonstrated to measure the distributions for the interparticle cohesive force, rather than just average values. The new method is demonstrated using the Hosokawa tester, by varying the amplitude of the vibration applied to a Hosokawa sieve screen, enabling the measurement of toner flow as a function of input energy. The method is demonstrated for toner particles, both without surface additives, and as a function of varying surface additive composition and loading of some typical silica and titania metal oxide additives. Toner force distributions are shown to be generally log normal. However it was also shown that poor additive dispersion, due to poor blending, can lead to asymmetric force distributions, which can deviate from a log normal distribution. Improved blending led to log normal distributions in this case as well. Both the mean and width of the distributions generally decrease with increased surface additive loading. Thus, better flow with metal oxide additives, is a result of a decrease in both peak cohesion and distribution widths.

The First Measurement of Cohesive Force Distributions in Powder Flow: New Insights into the Effect of Metal Oxide Surface Additives on Xerographic Toner

The Hosokawa powder tester has been used for years to determine cohesion of bulk powders, including toner. For the first time a method is demonstrated to measure cohesive force distributions, rather than just average values, using the Hosokawa tester. The method is demonstrated for toner, varying surface additive composition and loading. Force distributions are shown to be generally log-normal. Both the mean and width of the distributions generally decrease with increased surface additive loading. Thus, better flow with additives decreases peak cohesion and distribution width.

A Quantitative Cohesive Force Mechanism for Powder Flow: The Role of Metal Oxide Surface Additives in Xerographic Toner

Xerographic toners use sub-micron metal oxide surface additives to control powder flow. Toner powder cohesion, which is inversely related to toner flow, was measured with respect to the primary particle size and surface chemistry of the oxide used as the flow additive. The cohesion data is interpreted in terms of a quantitative cohesive force mechanistic model for toner flow. Thus, cohesion is described in terms of Van der Waals, capillary, and hydrogen bonding forces between the oxide particles on the toner surfaces, and by the nanogeometry of the contact between oxide particles, controlled by the oxide primary particle size. Adhesion forces decrease, and thus flow improves, with decreasing oxide primary particle size and with increasing hydrophobicity.

Flash hydrolysis deinking of laser print using degradable toner resin

AbstractThe choice of vinyl polymers as the plastic matrix for the pigment in xerographic toner did not anticipate the deinking thrust which has swept the paper industry. The hydrolytic stability of the carbon‐carbon bond in vinyl and diene copolymers has prevented the use of a plastic degradation strategy for toner removal. New toner resins based on alkali degradable plastics have been shown to allow up to 97% toner removal. Based on polyimide and polyesterimide toners (either magnetic or non‐magnetic) developed by Xerox, this study uses flash hydrolysis in the presence of 0.5% alkali to repulp. The process operates on 200‐300 second batches at 190−210°C. The best results were obtained using alkaline repulping and magnetic deinking coupled with washing. The alkali also inhibits the hydrolytic degradation of cellulose although it negatively impacts the brightness. Thus the use of a polymer resin containing a chemically sensitive function allows conversion of the toner to pigment fragments and water soluble oligomers. The former is best separated by magnetic deinking while the latter is removed by washing.

Effect of Alcohol Grafting on the Charging Characteristics of Silicas in Xerographic Toner

A series hydrophobic silicas have been synthesized by reacting normal alcohols with hydrophilic fumed silica A130 (16-nm) at high temperature. Elemental analysis, solvent washing study and IR analysis suggest that alcohols molecules are grafted onto the silica surface. A rough estimation from the elemental data reveals that the surface area that is accessible for alcohol grafting is ∼ 4% and the grafting process is independent of the chain length of the normal alcohol. Water wetting tests indicate that the synthesized silicas are hydrophobic. Charging studies of the alcohol grafted silicas in unpigmented SPAR (a polyester) toner reveal that they generally charge to a higher charge level at both low (20%) and high (80%) relative humidity (RH). The charging process appears to be less humidity sensitive as compared to analogous, commercially available hydrophobic silica, e.g., R972, from Degussa. The length of the grafting group is shown to affect the charging performance and the molecular origin is proposed and discussed. Two strategies to further improve the charging performance of alcohol-grafted silicas were also studied in this work. We observed very similar charging levels and a reduction in humidity sensitivity when we grafted hydrophilic silica A130 with branched alcohols. We observed very interesting humidity effect when we modified a 1-dodecanol grafted A300 silica with 1-hexadecanol. Relatively speaking, the charge level of the modified silica is found to be lower than that of the unmodified grafted silica at 20% RH. The opposite is observed at 80% RH. This results in a developer that has very little humidity sensitivity in toner charging. The insensitivity of the toner charging process is rationalized.

Chemical Surface Modification of Alumina and Titania Surface Additives for Charge Control of Xerographic Toners

Nanosize silica, titania and alumina metal oxide particles are common xerographic toner additives for control of flow, charge, development and transfer. While silica is the most common and most studied oxide, titania and alumina have a more complex surface, comprised of surface acidic, basic and neutral sites. Further, superacid sites can be created by treatment with sulphuric, phosphoric or boric acids. These treated oxides show increased negative charge and admix when used as toner surface additives. For titania the charge increases with the acidity of the acid, in the order: boric acid < phosphoric acid < sulphuric acid.Infrared spectroscopy shows that calcining results in surface attachment of these acidic sites to the TiO2 surface. Further, these acidic sites, which involve about 5% of the total hydroxyl sites, can form ionic salts with triethylamine, a result of proton transfer from the acid to the amine. This results in a further increase in charge, and improvement in toner admix rates and RH sensitivity.

POCK MODEL SIMULATIONS OF PULMONARY QUARTZ DUST RETENTION DATA IN EXTENDED INHALATION EXPOSURES OF RATS

In recent years, a physiology-oriented multicompartmental kinetics (POCK) model was developed to simulate pulmonary retention data of biopersistent, noncytotoxic aerosols in long-term inhalation exposures of rats. Experimental data were successfully simulated for submicrometer-sized aerosols like carbon black, diesel soot, and titanium dioxide and for a micrometer-sized xerographic toner aerosol (Stober et al., 1994, 1995). This article describes for various rat strains successful POCK model simulations of experimental pulmonary retention data of micrometer-sized aerosols of biopersistent cytotoxic SiO2 modifications like quartz and quartzite. In the past, the POCK model was not applied to cytotoxic aerosols and dusts. Cytotoxicity was considered incompatible with the m od el assum p tion of a constant m acrophage lifetim e indep endent of the macrophage aerosol load. The few relevant experimental retention studies with biopersistent silica found in the open literature showed particulate lung burdens up to some 15 mg per rat lung. Apparently, at these loads, pulmonary burdens could be simulated because the fraction of alveolar macrophages killed by the cytotoxic particles was possibly still small compared to the total number of viable macrophages. Of necessity, however, the classical alveolar clearance in these studies was exclusively performed by alveolar macrophages that were burdened with cytotoxic particles, and the cells appeared to suffer from a substantial initial decrease of their inherent mobility. Thus a sizeable reduction of the alveolar clearance rate coefficient in comparison to nontoxic aerosol was found. The results for the model parameters of several different exposure studies are shown and interpreted in comparison to nontoxic titanium dioxide retention parameters.

Investigation of the Mechanism of Humidity Effect on Toner Charging: A Model Toner Study

The mechanism of humidity effect on the charging of xerographic toner is studied using model toners prepared by solution coating charge control additives (CCAs) lithium 3,5-di-t-butysalicylate (LitBSA) and cesium 3,5-di-t-butylsalicylate (CstBSA) onto the surface of 9 μm styrene-butadiene toner at a concentration of 4 μg of CCA per gram of toner. These toners were shown to acquire negative charges against polymer-coated metal beads largely by an ion-transfer mechanism. Investigations of the charging of these toners at 20 and 80% relative humidity (RH) show that there is a ∼29% decrease in toner tribo (toner charge), from −80 to −57 μC/g for the LitBSA toner as the ambient RH (relative humidity) increases from 20 to 80% during charging. On the other hand, the charging of the CstBSA toner is RH insensitive; the toner tribo remains at 29.5 ± 1.5 μC/g under identical conditions. The surfaces of the recovered metal beads (after tribo measurements) were analyzed by the time-of-flight secondary ion mass spectrometry technique. While Li+ and Cs+ are expectedly observed on the respective surfaces of the recovered metal beads due to the ion-transfer mechanism, we are surprised to find that the amount of ion that is transferred is insensitive to humidity changes for both toners, despite the fact that we observe an RH effect on toner charging for the LitBSA toner. In the negative mass spectral experiments, we observe an RH effect on the surface chemistry of the recovered metal beads. For beads that were charged with the LitBSA toner at 80% RH, we detected a small quantity of tBSA− at m/z 249. The 249 peak is not observed for beads that are contacted with the LitBSA toner at 20% RH, nor with the CstBSA toner at both high and low RHs. Based on the RH effects on toner charging and the surface chemistry, we suggest that the humidity effect on the charging of the LitBSA toner originates from a charge-recombination process between Li+ and tBSA- at 80% RH. The critical roles of the “water bridge” and the electric field developed between the charged toner and the metal beads on the humidity effect are discussed.

Mechanisms of Charge-Exchange in Xerographic Toner Powders

The mechanism of charge-exchange between a fresh uncharged toner and a charged toner in a xerographic developer has been studied using model toners in a cross-over experiment. The two model toners studied were prepared by solution-coating charge control additives cesium 3,5-di-t-butylsalicylate (CstBSA) and rubidium 3,5-di-t-butylsalicylate (RbtBSA) onto the surface of 9-μm unpigmented stryene—butadiene toner particles at a concentration of 4 μmole/g. We previously showed that these toners acquire negative charges when they are rubbed against the surface of polymer-coated metal beads. We further showed that the transfer of the cation from the surface of the toner to the surface of the metal beads is the major charging mechanism. In this work, we studied the mechanism of charge-exchange in these toners. The charge-exchange is monitored by the so-called “admix time,” the time required for the uncharged and charged toners to become equilibrated chargewise after mixing together. The mechanism was studied by adding 1% fresh uncharged RbtBSA toner to a charged developer consisting of 2% CstBSA toner and 98% of the polymer-coated metal beads. The surfaces of the toner particles and the polymer-coated metal beads, before and after toner admix, were examined by the time-of-flight secondary ion mass spectrometry technique. Results show that (1) both Cs+ and Rb+ are randomly distributed on the surfaces of toner particles after admix and (2) the surface of the metal beads consists of both cations. The mechanism of charge-exchange is discussed in terms of a dual mechanism involving an ion-exchange process between the charged and uncharged toners and a contact charging (ion-transfer) process between the fresh toner and the polymer-coated metal beads.

Photoresist-free fabrication process for a-Si:H thin film transistors

We fabricated a-Si:H thin-film transistors by using only computer-generated masks of xerographic toner, which replaces photoresist in each patterning step. This photoresist-free process produced thin film transistors with an on/off current ratio of ∼10 7, a threshold voltage of ∼3 V and an electron mobility of ∼1 cm 2 V −1 s −1.

Metal Oxide Surface Additives for Xerographic Toner: Adhesive Forces and Powder Flow

Xerographic toners use submicron metal oxide surface additives to control powder flow. Indeed, oxides have been used to improve flowability or compressibility of cohesive powders for decades, from coffee whitener to aspirin. To date there has been little attempt to understand the mechanism of action of flow aids. In this paper, toner powder cohesion was measured with respect to the primary particle size, hydrophobicity, and hydrogen bonding of the oxide. Cohesion is interpreted in terms Van der Waals, capillary, and hydrogen bonding forces. Flow with oxides is determined by the nano-geometry of contact between oxide particles, determined by the oxide primary particle size. Adhesion forces decrease with decreasing oxide primary particle size and increasing hydrophobicity.

A-Si:H Thin-Film Transistors on Rollable 25-µ;m Thick Steel Foil

AbstractWe report the first amorphous silicon thin film transistors (TFTs) on flexible, ultra-thin substrates of 25 µm thick stainless steel foil. The transistors remain operational under convex or concave bending down to 2.5 mm radius of curvature. Taking advantage of the flexibility and resiliency of these devices, we have successfully fabricated TFTs using only xerographic toner masks printed directly on to the steel substrate and using mechanical alignment in the laser printer to obtain the necessary overlay accuracy. The goal of our work is to develop a foldable active-matrix transistor backplane, at low cost and high throughput, for use in highly rugged and portable applications such as foldable intelligent maps. Our results suggest that such foldable backplane circuits are feasible.