In order to obtain high quality printing results, it is important to understand the mechanisms of ink absorption and setting on various substrates. The final position of ink pigments determines the ink density and the resolution of the printed product. Absorption rates of aqueous and solvent inks into nonwoven fabrics were characterized with a Bristow absorption wheel. A model based on Darcy's Law was applied to predict the ink absorption rate into the nonwoven fabrics. The model links the void fraction, pore size, contact angle, and the Darcy permeability coefficients to the absorption rate. The results showed a good correlation between the experimental data and the predicted results for many combinations of substrates and inks, but in a few cases, the absorption rates were different than expected. A clear difference of microscale distributions between aqueous and solvent inks on the nonwoven fabrics could be obtained by confocal laser scanning microscopy.

The wide-format dual-line 1200 dpi thick film thermal head was developed utilizing the following technologies: (a) an alternated conductive lead circuitry inside the thermal head is devised in that it does not use diodes for the prevention of reverse current; instead, it adds a secondary power supply to redirect the reverse current. (b) The heater nib line of the printhead is produced stably and accurately using the direct dispensing system which, based on the air microtechnology, feeds back the air pressure and controls the linear actuator to follow the surface of a substrate. (c) The 1200 dpi printhead is combined of two identical 600 dpi nib lines with half-pitch offset in the nib line direction and separated by a distance of 32 nib lines in the printing direction. Although the printhead is not made of a 1200 dpi single nib line and may be classified as a quasi-1200 dpi printhead in a more strict sense; however, it does exhibit a 1200 dpi-like performance and, for the convenience of presentation, it is still called a 1200 dpi printhead in this article. Several wide-format (up to 54 in. width) products based on the 1200 dpi thermal printhead have been designed and are capable of printing half-tone images of up to 133 lines per inch.

Azo dyes and pigments are widely used in the imaging industry because of their versatile colors as well as their low price. However, it is often pointed out that the color in the solid state is sometimes drastically different from that in solution. An attempt has been therefore made in the present investigation to elucidate the electronic structure of two classical simple azo dyes on the basis of the crystal structure: methyl orange [Na(I)-(dimethylamino)azobenzene-4-sulfonate (MO)] and its derivative [4-(dimethylamino)azobenzene-sulfonic acid (MOH)]. Accordingly the authors found a new trinuclear Na complex (pale red) of MO, as well as a new polymorph (purple) of MOH in addition to the previously reported phase (vivid red). In MO and also in the purple phase of MOH, excitonic interactions are basically responsible for the color change on going from solution to the solid state. On the other hand, the authors found a zwitterionic structure in the vivid-red phase of MOH as formed by NH···O intermolecular hydrogen bonds. The vivid-red color can be interpreted as arising mainly from the zwitterionic structure.

The electronic spectra of the 1:1 rhodamine B base (RBB: leuco dye) with ethyl gallate (EG: developer) have been studied in solution and in the solid state (i.e., in spin-coated films and in single crystals) on the basis of the crystal structure analysis. There are two crystalline phases in the 1:1 "RBB/EG" colorant at low (93 K) and room temperatures. In solution, the maximum color intensity occurs with the 1:1 molar ratio of RBB with HCl, giving an absorption band at about 556 nm. In the solid state of spin-coated RBB/EG layers, an absorption band appears around 577 nm due to the ring opening caused by the hydrogen bond formation between RBB and EG. However, the color intensity is found to be limited to about 80% of the maximum available value. This has been attributed to a residual fraction of RBB molecules whose lactone ring is still closed due to steric hindrance. In addition, the polarized reflection spectra measured on single crystals of RBB/EG exhibit a drastically different spectrum (i.e., absorption maximum about 480 nm) from that of spin-coated films of the amorphous state. This result suggests that strong excitonic interactions of the H-aggregate type are operative in single crystals of RBB/EG that significantly displace the absorption band toward shorter wavelengths.

Drop deposition has been studied over a wide range of time scales under conditions relevant to direct printing of etch resist patterns on printed circuit boards. Early-stage impact-driven spreading of 80 pl drops of UV ink and phase change resist was imaged by 20 ns duration flash-based photography, while a 27,000 fps high-speed camera was used to study the later stages of spreading up to 130 ms postimpact. The presence of an attached ligament at impact was shown to reduce the effect of impact inertia and the tendency for recoil, although this was less significant in the later, capillary phase. The effects of surface wetting appeared to be insignificant during the impact and relaxation spreading phases but dominated the behavior during capillary spreading. Cooling by conduction from the substrate was shown to be effective in arresting drop spreading for the phase-change ink on a submillisecond time scale.

Upon driving the unimorph type piezoelectric actuator of an ink jet in a high temperature high humidity environment (38°C//80%), many failures occurred after approximately 1 billion pulses. We hypothesized that the failures occurred due to hydrogen that was generated from the electrolysis of water, causing the piezoelectric element to deteriorate. Based on this hypothesis, we examined electrode materials to reduce the frequency of failures. We found that failure rate can be improved if material with high standard electrode potential is used as the electrode material on the high potential side and material with low standard electrode potential is used on the low potential side, and more specifically, if metal oxide is used for the electrode on the low potential side. Based on these findings, a combination of silver palladium for the electrode on the high potential side and stannous oxide Sn_xO_y for the low potential side was used as the combination of electrode materials that can be formed at low cost. Upon implementing a running test with this combination of electrode materials under a high temperature high humidity environment, we confirmed that failures do not occur even at a continuous drive of 30 billion pulses and that the long-term reliability of the unimorph type piezoelectric actuator improved significantly.

In this article the authors propose a color correction system for images illuminated by multiple light sources. The proposed system can generate an illumination-invariant image under various light sources. Such illumination-invariant image acquisition becomes possible by adopting a user-defined profile connection space (UD-PCS) that generates custom profiles, which can be used to eliminate the effect of directional light sources. The proposed algorithm consists of the following steps: (i) input image capture with minimum of two light sources and reference Qpcard, (ii) estimation of color correction matrix and tone reproductive curves, (iii) modifying International Color Consortium profile tags to generate UD-PCS, and (iv) color mixture map extraction for fusion of input source images. Experiments were carried out on several test images with different light sources in order to prove the utility of the proposed algorithm.

In image capture a scene with nonuniform illumination has an influence on the image quality, especially the contrast and detail in dark regions. Generally, the tone curve or histogram of an image is modified to improve the contrast and detail, yet this is insufficient as the intensity and chromaticity of the illumination vary with geometric position. Thus, the multi-scaled retinex algorithm has been proposed, where the influence of nonuniform illumination is reduced by partitioning the original image using local average images that are estimated based on Gaussian filtering of the original image. However, the multi-scaled retinex algorithm produces color distortion as the local average images are independently estimated for each channel. In particular, if the chromatic distribution of the original image is not uniform and is dominated by a certain chromaticity, the local average image includes not only the intensity and chromaticity of the illumination but also the dominant chromaticity through the Gaussian filtering, thereby distorting the color. Accordingly, this article proposes a multi-scaled retinex using a modified local average image to reduce the color distortion by the dominant chromaticity of the original image. As with the multi-scaled retinex algorithm, the local average image is obtained through Gaussian filtering of the original image. The local average image is then divided by the average chromaticity value of the original image to reduce the influence of the dominant chromaticity. However, because the average chromaticity value includes the dominant chromaticity of the original image and the chromaticity of the illumination, the chromaticity removed from the illumination in the local average image needs to be compensated. Therefore, the chromaticity of the illumination is estimated based on the chromaticity of the highlight regions in the original image. The chromaticity of the local average image is then modified by the estimated chromaticity. In experiments, the proposed method was found to improve local contrast and reduce the color distortion.