Abstract This article presents the experimental photodischarge kinetics of electrostatically fatigued dual-layer organic photoconductors characterized by an electrophotographic incremental charging technique that reveals the differences in the photoconductor charging profiles. During normal operation, 15% of the holes that migrate to the surface after photodischarge are not neutralized by the negative surface ions. The accumulation of these lingering surface charges (charge transport material radical cations) manifests itself as defects in half-tone images, as either missing or reduced size dots or lines. In the presence of corona gases, these surface holes oxidize and reduce the energy barrier for hole injection from a positively charged surface, e.g., contact with a transfer roller. These injected holes accumulate near the charge generation layer and require twice the amount of negative charge to attain the same surface potential as that of a new organic photoconductor (OPC) drum. The damaged depth of this injection region extends to about 50 nm into the OPC surface and is easily removed by the printer’s abrasion mechanisms (e.g., cleaning blade, toner, paper).
Abstract In ceramic decoration by xerography, once the toner particles have been deposited, the substrates need to be subjected to thermal treatment at temperatures above 600∘C to eliminate the organic constituents and enable the inorganic constituents to be integrated into the ceramic surface. The inorganic component includes a fraction that is able to modify the aesthetic appearance and a fraction that facilitates fusibility and integration into the substrate. At present, this type of toner is made by the pulverization method, with the presence of irregularly shaped particles and inorganic particles that are only partly coated by the polymeric matrix, which can lead to problems of particle flowability and electrical conductivity. This article describes a new method of ceramic toner preparation by suspension polymerization that avoids the above problems. The method allows a high inorganic component content in the toner composition to be reached, assuring good color saturation in decoration.
Abstract This article demonstrates the effect of near-neutral deinking chemicals on the outcome of a deinking process. More specifically, we demonstrate that good deinkability of digital prints, i.e. liquid-electrophotographic (LEP), dry-electrophotographic and inkjet (IJ) prints, at the laboratory scale, can be achieved with effective near-neutral deinking chemistry that is based on readily available commercial chemicals. The deinking results meet or exceed the target levels, such as ink speck contamination (i.e. dirt area), ink elimination, filtrate darkening, color shade and luminosity, as defined by the European Recycling Paper Council’s deinking scorecard. It is noteworthy that the proposed chemistry has a prominent effect on reducing the dirt area of LEP print media and suppressing the filtrate darkening of dye-based IJ print media. Experimental results using the proposed deinking chemistry compare favorably to those obtained with alkaline deinking chemistry.
Abstract Emissive screens are generally believed to be the main reason for eye fatigue when reading text on displays. This study examines the impact on eye fatigue of the reading style and medium: reflective or emissive. We test three media: paper, LCD (liquid crystal display with backlight), and electronic paper (book reader using electrophoretic reflective display). Eye fatigue levels in a reading task are evaluated under two reading styles (free condition and fixed condition) for the three media by measuring the increment in near point distances after each reading task. Subjects were requested to read a novel for 180 min using the three media. The fixed reading condition yielded a statistically significant increase of the near point distance on the three media, while the free condition showed no such increment, regardless of the medium.
Abstract There have been numerous reports on the effects of atmospheric pollutants on digitally printed materials that describe fading of colorants, yellowing of substrates, colorant bleed, and delamination of the ink-receiving layer on some digital prints. In 2010, the Image Permanence Institute published the results of an experiment on the effects of ozone and nitrogen dioxide on various digital print types. While it was not the intent of that experiment to determine the long-term effects of pre-exposure to pollutants, it was discovered after publishing the research that some of the samples dramatically yellowed while in storage. This research studied how those same digital prints stored under controlled room conditions changed after being exposed to ozone or nitrogen dioxide prior to storage. The yellowing of papers exposed to ozone before storage was previously documented in studies directed toward the development of test methods for accelerated aging. This article documents real-time observation of digital prints after several hundred days in storage and addresses the potential damage to digital prints over time after exposure to ozone or nitrogen dioxide. The test samples included inkjet, color and black-and-white electrophotography, dye sublimation, digital press, chromogenic, and offset lithography prints. Paper yellowing, colorant change, further colorant bleed, and additional disintegration of the colorant layer of some prints were observed. Porous-coated materials exposed to ozone yellowed more dramatically in storage than when under direct exposure. This illustrates that the initial results of change in these materials do not describe the whole story.
Abstract Gamut volume is one of the parameters generally used for the characterization of printers and other imaging devices. However, it can also be used for monitoring color print fading. Relative gamut volume changes plotted as a function of the exposure dose can be conveniently used to determine the fading rate and corresponding lifetime. Calculation of the gamut volume is a challenge on its own, as a set of isolated points in three-dimensional space does not define a unique body in any obvious way. This problem has been addressed using the quick-hull algorithm combined with a non-linear convexing transformation of the measured data points and subsequent determination of the convex hull. In this article, the optimal degree of convexing is determined empirically on an extensive set of 19 samples including essentially all presently used photoprinting techniques. The actual use of gamut volume changes for monitoring of color print fading is illustrated on selected samples.
Abstract In many practical applications, printed images or text are exposed to a light source, making their lightfastness an important characteristic. Good lightfastness assures good color stability after prolonged use. In this study an accelerated aging procedure using a xenon arc lamp was applied to induce and investigate the degradation of Altona test chart color images and patches of offset and electrophotographic prints on papers made of virgin and 100% recycled fibers. In this article the authors present a new image processing method based on chrominance histogram quantification and discuss its applicability and performance with respect to the conventional spectrophotometric approach. The chrominance histogram quantification method using printed images proves to be a viable alternative to the established spectrophotometric measurements that are implemented on color patches and yield 2D color gamut information.