Error diffusion is widely used in digital image halftones. The algorithm is very simple to implement and very fast to calculate. However, it is known that standard error diffusion algorithms, such as the Floyd Steinberg error diffusion, produce undesirable artifacts in the form of structure artifacts, such as worms, checkerboard patterns, diagonal stripes, and other repetitive structures. The boundaries between structural artifacts break the visual continuity in regions of low intensity gradients and therefore may be responsible for false contours. In this paper, we propose a new halftone method to reduce the structural artifacts and to improve the gray expression, called hybrid error diffusion, by using the concept of "error diffusion by perturbing the error coefficient with a mask." The proposed algorithm consists of two steps in each pixel position. In the first step, a perturbation is calculated using the internal pseudorandom number and a selected 4×4 mask, similar to a dither mask. In the second step, error diffusion weights are calculated with the criterion for each pixel value. The proposed hybrid method can reduce the structural artifacts while keeping the advantage of the error diffusion. This paper discusses the performance of the proposed algorithm with experimental results for natural test images. Then, objective assessment results are given using statistical tools and the structural similarity measure for color images.

Contour is an important element of an image, usually expressed by the difference in density between two areas of an image. Objects are usually recognized from observation of their contours. In some cases, emergence of a false contour is a problem in image coding and decoding. Halftoning is an essential image process for digital printing of continuous tone. Contour perception is studied experimentally under various halftoning conditions, observation distances, and illumination conditions. The results show that in the human visual system, contour perception becomes easier with a decreasing stimulus of dots, which serve as the component of a halftone image.

Application of full color printers has spread rapidly in the office environment, and demands on the full color printer have been also increasing; especially, high-speed printing, oilless fusing and fine image quality are strongly requested. Recently, several types of chemical toner have been launched. Because they have small and narrow particle size distributions, they have an advantage in fine image quality. However, the resin of chemical toners are usually styrene-acrylic, which is not suitable for high-speed printing and glossy images for pictorial applications because the styrene-acrylic has to be high molecular weight to make toner have sufficient durability. On the other hand, polyester has better properties for high-speed printing than styrene-acrylic because of the existence of a polar group that enhances a compatibility with the cellulose of paper. Polyester has good durability even if it has a low molecular weight and thus can provide a glossy image. Thus polyester has several advantages over styrene-acrylic. In general, it is difficult to use polyester as the binder resin of chemical toner. On the other hand, it is easy to make polyester color toner by the pulverization method, but it is difficult to make pulverized toner having small and narrow particle size distribution for fine image quality, and it is also difficult to make pulverized toner having both oilless fusing ability and sufficient durability. In this article, design of oilless fusable, pulverized color toner with small and narrow particle size distribution was investigated. This advanced color toner named "MC toner" can provide high-speed printing, oilless fusing, and also fine image quality.

This study describes the preparation of microemulsion inks based on commercially available disperse dyes for thermal bubble ink jet printing. The approach to make the inks is by formulating to form water-soluble emulsions (o/w), which were then optimized to reach a dynamically stable isotropic condition. The dyes in three primary colors–cyan, magenta, and yellow–were systematically investigated. Different species and amounts of dispersants, emulsifiers, and dyes were selected to prepare microemulsions after intense stirring. The system, D50/963H/ Pannox140/glycerin/water, performed excellently in particle size reduction and size stabilization. The surface tension, pH value, viscosity, and stability of the microemulsion inks meet the requirement of the applied printhead to provide both good printing quality and excellent printing consistency without clogging in the nozzle. The interaction between dyes and the microemulsion system can be comprehensively understood based on the results of particle size analysis, lightfastness, water fastness, and the characterization of printing quality. The low particle size-reducing efficiency can be attributed to the compatibility between dye and dispersant structures as well as particle aggregation. The lightfastness could be enhanced with smaller particle size but decreased with dye content. However, the water fastness of the preformed sample was identically high without being affected by the dye particle size in the range between 80 nm and 96 nm. The printing performance was found to be closely correlated with the dye structure and ink concentration.

Copper phthalocyanine dyes, widely used in various imaging systems, are susceptible to fading under ambient conditions. One of the main factors responsible for such fading is the presence of ozone. Addition of suitable antiozonants has been shown to be effective in improving ozone stability. Although the exact mechanism of such stabilization is not fully understood, the electronic structures of the additives have shown to have significant impact on their effectiveness. In order to increase the ozone stability of copper phthalocyanine dyes without any additives, several copper phthalocyanine dyes containing substituents of varying electronic structures were synthesized and tested for ozone stability. The structure of a copper phthalocyanine dye with significantly improved stability to ozone is described in this paper. Possible mechanisms leading to such stability are also discussed.

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.

A simulation method to analyze the behavior of a toner cloud driven by a traveling electrostatic wave with air drag is proposed. The two-fluid flow model, which regards air and toner cloud as incompressible and viscous fluids, is employed. A method of the calculation of the electric potential using the moving particle semi-implicit (MPS) method, which is often used in the study of fluid dynamics, is developed in this article. In the present method, all of the motion of the toner, the airflow, and the electric potential are calculated by using the moving particle semi-implicit method. Common calculation points are used in the electrostatic calculation, the toner motion calculation, and the airflow calculation in order to avoid the complexity of data exchange among those calculations. The validity of the calculation of the electric potential using the MPS method is confirmed by comparing the results to those of a model that has a known strict solution. Modeling of the behavior of toner cloud in toner transport with a traveling electrostatic wave is performed. An increase in the maximum synchronous frequency due to air drag is demonstrated.

New techniques have been developed for analyzing, in detail, the shape and development of ink jets and drops. By using flash illumination of very short duration (ca. 20 ns), high quality, single-event digital images of jets and drops can be captured. A computer program, PEJET, has been written to automate the processing of such images and to generate quantitative data about the whole ink stream. From this data, it is then possible to compute the variation in fluid volume, volume flow, and velocity as a function of both position and time. The method has been shown to have high accuracy. The results can be used to study the influences of nozzle design, drive waveform, and fluid properties on jet and drop formation, as well as to provide accurate data for comparison to the results of computational modeling. Examples of results from a drop-on-demand system are presented that illustrate the potential of the method to compare quantitatively the performance of print systems and inks.

We investigated effects of thin film layers on actuating performance of microheaters. Bubble behaviors on microheaters were observed experimentally, and heat conduction characteristics in thin film layers were analyzed numerically. Nine kinds of tantalum nitride (TaN) microheaters were prepared. Step-stress test showed that voltage limits of nonpassivated heaters were <50% of those of passivated heaters. Open pool bubble test was carried out using deionized water as a working fluid. Nonpassivated heaters produced comparable bubbles with only 20–50% of input energy required for passivated heaters. However, nonpassivated heaters could be operated only in a narrow range of driving voltage. We constructed a hybrid model for bubble nucleation prediction correlating nucleation times with driving powers. Based on work of bubble formation estimated from bubble volume evolution, actuation efficiencies of microheaters were calculated and compared. Efficiencies of nonpassivated heaters were much higher than those of passivated heaters. However, nonpassivated heaters failed to show robust actuating characteristics over a wide range of power density. As promising microactuators, nonpassivated heaters need further investigation from a viewpoint of reliability.

This article describes a method of forming a stacked hybrid metal structure and pattern to enhance radio-frequency identification antenna coil inductance. The essential strategies included the use of multilayer self-assembled polyelectrolytes to modify the surface property of substrates, an ink jet printing process for a Pd containing catalyst, and a stacked hybrid metal layer formed by electroless plating in subsequent processes. The results demonstrate that the minimum line width and line spacing can reach 100 μm/100 μm, and electrical performance is compared to prior research in employing different approaches. The method presented in this article enhances the capability by adapting to any substrate surface using the self-assembled polyelectrolyte technique. Therefore, results were verified on different substrates, such as PI, PET, and FR-4; satisfactory electric performance for application was obtained. In detail, the inductance of the antenna improved from 300 nH to 20 μH for a monolayer coil, and 600 nH to 50 μH for a double layer coil, depending on the metal thickness.