Ink jet printing technology is open to various applications because of advantages such as popularization of relatively cheap printers, litter free printing, ease of operation, easy maintenance, ability to print onto non-flat media, and ease of making prints of various sizes. However, some improvements are still needed in the application of photofinishing to replace color silver halide photographic prints. There are two kinds of ink jet printing systems in terms of inks: dye-based inks and pigmented ones. We know empirically that dye-based inks can produce better print quality than pigmented inks in many instances. Typical weak points of pigmented ink images are conspicuous grain, uneven low gloss, and bronzing. Pigmented ink images, however, generally show better image permanence than dye ink images. We have produced many ink jet prints with both kinds of inks and examined the characteristics of these images. Finally we focused our attention on the pigmented ink images. We determined the possibility of managing both image permanence and print quality, using microporous printing media with a specially coated layer for pigmented inks. We conclude that ink jet printing with pigmented inks can be applied for photofinishing purposes.

In this article, the dynamics of droplet impingement and absorption into microporous materials for pigment based aqueous inks and dye based aqueous inks are compared. For dye based inks it was shown earlier that three main phases could be resolved: inertial spreading, absorption, and evaporation of the liquid, leading to the final equilibrium condition on which the typical customer is evaluating the image quality. For the inertial spreading phase it could be shown that the spreading behavior is largely determined by the hydrodynamic properties, and is easily amenable to dimensionless analysis. The absorption phase could be well described by a capillary wicking process according to imbibition models. Evaporation is the slowest process only being finalized after many seconds. These results are now compared with droplet impingement and absorption of pigment based inks on microporous receivers. It is shown that these inks behave totally differently from dye based inks. Immediately after impingement and initial spreading the pigment particles start to coagulate on the surface of the microporous layer, creating a filter cake limiting the passage of carrier liquid. As a result much longer absorption times are observed and the equilibrium dot stays on top of the microporous layer. Most polymer stabilizers in the pigment based inks create a colored polymer layer having polymeric blend characteristics limiting considerably the penetration of water compared to the capillary wicking process. The capillary imbibition models are not valid any more because now the build-up of the filter cake changes not only the receding contact angle but also introduces a diffusion process changing as a function of time during the drying of the wet ink.

The regulation of energy consumption for printers and copiers is becoming increasingly strict each year. Also, with increasing speeds of the machine system, the fusing of toner on paper becomes even more difficult. Thus, toner that fuses at lower energy is expected. There are several solutions to address this issue. A typical method is to use low Tg and low Tm resins for binder. This solution, however, offers limited improvement. Crystalline polyester (CPES) is a long studied candidate that shows great promise. However CPES is not yet widely used due to its poor storage stability and low anti-offset properties. This report explains how to overcome problems encountered with toner containing CPES, improved uses of CPES in toner, and the enhanced properties of CPES. The properties of toner containing CPES, and how that toner works for low energy fusing, are described.

Experimental research was carried out on transport of particles and particle size classification in a traveling electrostatic field. Particle conveyors which consisted of parallel electrodes were constructed and a four phase traveling electrostatic wave was applied to the electrodes to transport particles on the conveyor. The following points were clarified by the experiment: (1) Particles were transported almost linearly with time. Transport rate was also linear with applied voltage but a threshold existed due to adhesion force. (2) The direction of particle transport did not always coincide with that of the traveling wave but it was in part changed depending on the frequency of the traveling wave, the particle diameter, and the electric field. Motion of particles at low frequency was nearly synchronized with the traveling wave but at medium frequency it was opposite to and slower than the wave. Particles were vibrated but not transported at high field frequency. (3) Particles were efficiently transported under conditions of high electrostatic field with a rectangular waveform. (4) Particles essentially moved along the electric flux line, but electrostatic interaction and particle-particle and particle-conveyor collisions made trajectories complex. (5) Particles were classified according to size under application of voltages of appropriate frequency.

Measurements of toner adhesion are usually at least one order of magnitude larger than predicted by image force calculations that model the toner charge by locating it in the center of the toner particle. In order to account for this discrepancy, it has been suggested that either the toner charge is not uniformly distributed on the surface or that van der Waals forces dominate toner adhesion. We propose an alternative model of toner adhesion, which takes into account a recent result that shows that there is an electrostatic proximity force of adhesion at the contact point between a toner particle and a conductive plane.

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).

This report is a continuation of a project involving the development of printer models that are able to simulate the behavior of printers regardless of the halftone pattern used in the process. The previous report described a model for a laser electrophotographic printer that was able to simulate tone reproduction independently of the halftone pattern.¹ The current report is an expansion of this model to enable a simulation of noise characteristics of the laser EP process. The random noise behavior of the EP printing process, often called “printer instability”, is added to the virtual printer model prior to the application of a characteristic tone transfer function. The result is a printer model that is independent of the halftone pattern used in the printing process, but a model that is able to simulate (a) mean level tone reproduction, (b) RMS deviation in tone, and (c) higher order moments of tone reproduction. The model is semiempirical and was calibrated with experimental data from printed bar patterns. The calibrated model then was challenged with a clustered dot halftone, a Floyd-Steinberg error diffusion process, and a semi-dispersed dot halftone formed from a linear pixel shuffling algorithm. The mean value, the RMS deviation, and higher moments of tone reproduction of modeled images were compared to real printed images by comparing histogram distributions of toner mass coverage on the printed paper.