We have analyzed the thermal transfer printing process and 600 dpi high definition thermal transfer ink ribbons. The results of our analysis revealed that four factors would play an important role in high definition thermal transfer ink ribbons: (1) the rupture strength of the ink under printing pressure and temperature, (2) the adhesive strength between the ink and paper, (3) thickness of the ink layer and (4) the adhesive strength between the heated ink and the base film. We have used a quantitative model for the printing process to design an improved ink ribbon, and we describe measurements of the viscoelastic characteristics which were used to optimize the ink materials. The improved 600 dpi high definition full color thermal transfer ink ribbon has a base of 2.5 μm polyethylene terephthalate (PET). The ink comprises two layers; a 1.3 μm ethylene-vinyl acetate copolymer thermoplastic resin and a release layer of 0.9 μm wax.

An ink jet instrument was used to measure the drop absorption time of various ink-receiver systems. The drop absorption time is defined as the time required for the receiver to completely absorb the impinging ink drop, i.e., the drop totally penetrates into the receiver and disappears from the receiver surface. The instrument consists of a piezo printhead with drive electronics, a stage for receiver support, a strobe light, a CCD camera, imaging optics, and image capture system. The drops ejected from the printhead have a volume of about 25 pL and a velocity of about 5 m/sec. The receivers used in the measurements include both non-porous and porous receivers. Results indicate that nonporous receivers with swellable polymeric coatings have much longer drop absorption time (>30 sec) than those receivers with porous coatings (∼33-100 msec). The difference in drop absorption time between non-porous and porous receivers can be ascribed to the basic difference in the physical mechanisms of ink penetration into the receiver, i.e., diffusion of ink in the polymeric receiver versus capillary flow of ink in the porous receiver. Based on these physical phenomena, simple one-dimensional models have been developed to describe the drop absorption process in the non-porous and porous receivers. The dependence of drop absorption time on the volume of ink drop and physical properties of ink, such as viscosity and surface tension, and receiver, such as diffusion coefficient and porosity, was also derived. Comparison of model results with experimental data are presented and discussed.

The dot fidelity of ink jet dots has been investigated for several different coated ink jet papers. Serafano and Pekarovicova have defined dot fidelity in terms of dot area and roundness. For ink jet printers, we can also define a nominal dot area and an “ideal” dot area, once the resolution of the printer is known. The nominal dot area is the area of the square pixel defined by the inverse of the resolution of the printer. The “ideal” dot area is defined as the area of the circle in which the square pixel can be inscribed. This is the smallest circular dot that will cover 100% of the area when all dot positions are printed. This pixel area is π/2 times the area of the square pixel. Thus, we can compare the actual printed dot size with both nominal and ideal dot sizes. This analysis provides a direct interpretation of dot gain, which can be compared with values obtained from densitometry. The dot areas observed in our laboratory varied between 1.25 and 13 times the ideal dot area, depending on the resolution of the printer and whether the coating was matte or glossy.

Digital image analysis and optical microscopy are used to compare various print quality parameters of pretreated fabrics. In this work, woven and knitted cotton fabrics were treated with various chemical formulations containing ingredients like alginate, silicone based textile softeners and fine silica powder. A special print pattern was designed and printed on paper-supported pretreated fabric samples using a commercially available ink jet printer. Analysis of these print patterns was performed using an optical microscope and a digital image analysis program. The quality of these printed patterns were evaluated in terms of (1) color related metrics (L* a* b*) and (2) appearance related metrics (line width). Results show that digital textile printing quality on plain weave and knitted cotton fabrics is influenced by the fabric pretreatments, the most noticeable being the appearance related quality, i.e., the line width. The print quality on these pretreated cotton fabrics was not significantly affected by the fabric structure and the hydrophilicity of the fabric surfaces as long as the pretreatment can give cotton fabrics a balanced hydrophilic/hydrophobic character. From these studies it is concluded that digital textile printing quality can be optimized with appropriate pretreatments. For the plain cotton weave and knit fabrics studied, a pretreatment containing 2% alginate, 2% silicone softener and 1% silica shows good balance in colorant retention and line width control.

Experimental, theoretical, and numerical investigations have been carried out to evaluate resonant frequency and stiffness of a magnetic bead chain in the magnetic field. Chains formed on a solenoid coil were vibrated by the sinusoidal wave and impulse wave to deduce resonant frequency. It showed weak dependency on the magnetic flux density and the bead diameter, because both the equivalent stiffness and the chain length were large in accordance with the increase of the magnetic flux density. These characteristics were confirmed by theoretical considerations based on an assumption of potential energy minimization and a numerical calculation with the Distinct Element Method. Stiffness of the chain was directly measured by observation of chain deflection in inclined gravitational field and the results agreed with the dynamically deduced characteristics. It was concluded that the resonant frequency was 20–60 Hz and the static stiffness at the top of the chain was 10⁻⁴ – 10⁻² N/m. The investigation is expected to be utilized for the improvement of the two-component magnetic brush development subsystem in electrophotography.

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 cleaning performance (lifetime of cleaning blades and cleaning ability) of a leading type blade cleaning system for electro-photography is examined theoretically and experimentally from the viewpoint of tribology and rheology. Wear characteristics and cleaning ability of cleaning blades are found to be described well by a model which takes into account stick–slip behavior of the cleaning blade against a photoreceptor surface. A theoretical analysis of fatigue wear which takes into account vibration loss tangent (or rebound resilience), applied load on the cleaning blade on the photoreceptor surface, and friction coefficient between the blade edge and the photoreceptor surface, agrees well with results of accelerated wear experiments and lifetime evaluation tests using copying machines on the market. The cleaning blade edge once stretched by the photoreceptor surface during the stick process returns to its original position gradually with a characteristic relaxation time during the slip process and forces remaining toner particles to move against the rotating direction of photoreceptor drum. Therefore, toner particles have a greater possibility of going through the blade nip during the slip process. The theoretical analysis and the experimental results suggest that cleaning ability is proportional to the reciprocal of the relaxation time.

Charge control agents for liquid development were evaluated by electrochemical measurements, cyclic voltammetry and pulse voltammetry. Characteristics of charging were easily founded at high speed by these electrochemical methods. The NH standard potential of the charge control agent (versus NHE) was obtained and converted into an ionization potential. The control of charging in developing materials was adequately explained by the redox potential of the charge control agent. The present article reports that the best combination can be predicted by measuring redox potentials before formulating the toner.