The formation of the printing ink dot on the substrate is the final and the most critical phase in the printing process. The ink distribution on the printing surface and the drying mechanism depend on ink characteristics as well as on many other factors, for example, surface energy, roughness, sizing, and porosity. Suitable dot gain and high circularity (near unity) of printed dots predict the final print quality. High deviation from ideal circularity could cause undesired phenomena like wicking and bleeding. The aim of the present study is to determine ink dot formation by three different microscopic methods, optical microscopy (OM), scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM). The main goal of the authors research was to evaluate the applicability of CLSM as a nondestructive method for three-dimensional visualization in the analysis of ink dot formation on UV ink jet prints. To validate the feasibility of such means in a three-dimensional context, the images obtained are compared to those obtained by traditional two-dimensional imaging systems such as OM and SEM. The authors show that the CLSM produces a replica of the cross-sectioned dot profile as seen in SEM. This means that the CLSM technique can be used to rapidly assess the dot profile without physical sectioning.

With the dramatic increase in the prevalence of photoprinting using ink jet printers in recent years, much effort has been made to increase the longevity of the resulting prints. Many of these phenomena, unfortunately, require long-term testing in order conduct an accurate assessment. Much of the testing to date has been purely empirical in nature, allowing little improvement from a rational perspective. To overcome these limitations, this paper introduces a simple model of the light induced fading of magenta dye-based inks on polymer-coated photo media that represents fading as a two step process. Using this model, fade data collected in as little as nine days may provide accurate predictions of these ink/media combinations out to approximately 20 years of simulated fading. In many instances, the model can be further simplified. This analysis allows the definition of a "light fade factor" for both the ink and media which may serve as a useful figure of merit to facilitate the rapid qualitative comparison of ink and media formulations.

The ionic wind occurs with corona discharge. Knowledge of the ionic wind in a machine is necessary as a measure of the degradation of the image that originates from the generation products on corona discharge. The authors investigate the characteristics of the ionic wind in the neighborhood of a double-wire corona device through computational fluid dynamics to better understand this phenomenon. Various flow characteristics have been found. An inflow appears at the upper ventilation slit in the fan-off case. The primary flow diverges into some branches in a cross section. The authors can easily comprehend that this primary flow is derived from the schematic distribution of the body force. Several secondary vortices are induced by this flow at the same time. It is necessary to consider the effect of the grid electrode. Our numerical calculations correlate well with our experimental results by Particle Image Velocimetry. The primary flow appears also in a cross section on push-pull ventilation. Static pressure decreases along the wire. Large circulation occurs on the upstream side. Free powders that should contaminate the corona device move on the circulation. Large circulation thus has a close relation to contamination.

Electrical tribocharging is a fundamental physicochemical phenomenon and the basis of electrophotographic development. Despite extensive study, a complete understanding of the mechanism–commonly referred to as electron or ion transfer–remains unclear. Using a quantum chemical (QCh) approach, we studied the electron charge transfer (ECT) as one possible atomic-scale mechanism of tribocharging. We also describe ECT for several systems based on two materials in contact (tribopairs). Methods of density function theory and time-dependent density function theory were applied to QCh modeling using a cluster approach. A series of energetic and charge characteristics at the atomic level were calculated: including the highest- and lowest-occupied molecular orbitals (respectively) and the Fermi levels of complex components in their individual (free) as well as contact states, before and after electron excitation, ECT-excited energy states, charge distribution in the complexes, and the dipole moments of the excited complexes with ECT. Correlations were evaluated between the transferred charges and dipole moments and between transferred charges and Fermi levels. Furthermore, we could show that the QCh analysis offers insight into the ranking of tribocharging agents based on their chemical nature.

The binary ink developer (BID) in the Hewlett-Packard Indigo press converts low viscosity ElectroInk® into a pastelike layer that is presented to the photoreceptor. In the BID, ink solids move by electrophoresis onto the developer roller, and the layer is subsequently compacted mechanically and electrically by a squeegee roller. Quantification of ink solids content in this layer facilitates ink formulation and provides insight into BID operation. In this work, we describe the use of a unique tool developed in-house for profiling ink density on the developer roller. This device controllably removes submicrometer strata of ink from the rotating developer roller by applying a step-wise variable force to a scraping blade in contact with the roller. We find that the solids distribution within the paste layer varies depending on the electrophoretic and the squeegee roller voltages. A typical concentration profile starts at a minimum furthest from the roller, peaks within the paste layer, and then drops again as the developer roller surface is approached. We discuss the origin of this profile.

A single-sheet multilayer thermal imaging system consists of three color-forming layers comprising materials that are transformed from a colorless crystalline form to a colored amorphous form by heating. The color-forming layers are separated by thermally insulating layers, allowing for independent addressing of each color-forming layer (i.e., without any undesired color formation in other layers). The temperature required for the conversion from the colorless to the colored form is different for each of the color-forming layers. It may be difficult, however, to find suitable color-forming molecules having the right properties for image formation (e.g., chromophore and stability characteristics) as well as an optimum melting temperature. Incorporation of additional components into the color-forming layers allows the placement of the same color-forming crystalline material in any layer of the imaging system, eliminating the constraint of its intrinsic melting temperature.

Direct write technologies on circuits of printed circuit boards are attractive since the circuit pattern can be altered and manufactured almost instantaneously. In this article, microstrip lines were patterned by using electrohydrodynamic jet printing of silver nanoparticles as one type of direct write technologies. Characteristic impedance and insertion loss of a microstrip line were measured. The characteristic impedance was about 23 Ω, which agreed well with the calculated value of 21 Ω. The insertion loss was below 3 dB for frequencies below 1.8 GHz. This article demonstrated the possibility of using electrohydrodynamic jet printing of silver nanoparticles to obtain microstrip lines on circuit boards.

This article introduces ink jet-printed nanoparticle-based silver ink for integrated circuit interconnections. The environmental reliability of these interconnections at varying temperatures has not been exhaustively reported nor their electrical resistance tested at constant humidity. The authors ran two environmental tests to examine the reliability of ink jet-printed interconnections: 1000 h at 85° C at 85% relative humidity (RH) to evaluate the effects of humidity and 1000 cycles at -40° C – 125° C for the effects of temperature based on common industrial test standards. Results showed no silver degradation, and the electrical resistance fluctuated ∼3-6% for humidity and ∼5-6% for temperature. The results were mathematically modeled to understand the acceleration factor in the humidity test in the chosen user condition, i.e., at 50% RH at room temperature and at time-to-fail in the temperature cycling. The ink jet-printed interconnections showed good reliability.

In order to analyze toner scattering phenomena, toner motion between parallel plates in a transfer process is observed with the model experimental setup. The number of toner scattering events is counted by the IMAGE ANALYSIS software, and the relationship between the number of toner scattering and the transfer gap is obtained. The three-dimensional toner motion is calculated with electrostatic simulation using the distinct element method. The experimental and simulated results relating the number of toner scattering and the transfer gap are in good agreement. The observations on the toner scattering process are carried out for various combinations of parameters in the transfer process. A quantitative relationship between the number of toner scattering events and the parameters is obtained, which can be explained by the model derived from the toner scattering behavior.