Ink Setting Research Articles

PAPER INK INTERACTIONS .Impact of oil-binder interaction on pore structure in paper coatings as studied by internal reflectance. Part 2: Relation to structural expansion

Abstract In the case of ink setting on coated paper, s1gmficant decrease of accessible pore volume of the coating matrix can occur due to structural changes caused by swelling of latex hinder particles when contacted with the vehicle of oil-based ink. The impact of latex swelling, reduced network connectivity and the subsequent effects on the dynamic of spatial liquid distribution characteristics within the expanded pore network were examined by a recently established optical retlectance measurement procedure based on the refractive index differences between the coating components and the surrounding medium present in the interparticle pores. GCC model coatings with latex binders displaying differing swelling characteristics were exposed to liquid supersource imbibition without application of external pressure. Effects of both linseed oil and mineral oil on binder swe lling and consequent structural expansion were studied. lt is proposed that the linear retlectance behaviour in the saturated region is related to the mechanical restriction on expansion at the transition between the saturated and partially filling regions of the porous structure, and is consistent with an approximate catenary form in the macroscopic coating dimensional change as a function of depth. A conceptual structural change factor based on the change of retlectance in the saturated region is introduced, and is shown to correlate with the porosity loss values. The results suggest differences in the structural change factors in relation to the equilibrium oil uptake, coating porosity loss, and liquid propagation. The structural change factor also correlates the reflectance gradient within the coating thickness with regard to oil uptake with hinder content as the binder Ievel is increased.

Technical Evolution of Ceramic Tile Printing

Ceramic tile decorating techniques have evolved significantly in recent years. Digital inkjet printing technology has enabled digital systems to be used for the direct decoration of ceramic tiles, revolutionizing ceramic tile decoration and providing many advantages over traditional decoration techniques. It was the formulation of inks with soluble and vitrifiable stains that allowed inkjet printing technology to be introduced into ceramic tile decoration. The incorporation of milled inorganic pigments into the inks broadened the available color palette. However, the colloidal instability of these inks and the constraints of the printing heads themselves made it necessary to reduce pigment particle size, thus limiting color saturation and the color gamut. In order to increase color saturation and obtain a set of pigmented inks with colors more closely resembling CMYK colors, pigments with larger particle sizes need to be used. Indeed, other digital decorating techniques, such as xerography, allow larger particle sizes to be used, while also providing the advantages associated with digital decoration. However, the implementation of this technique for ceramic tile decoration requires the development of appropriate ceramic toners and adaptation of printing machines. This article reviews the technical evolution of ceramic tile printing and describes the development of a prototype, based on xerographic printing, that is able to print ceramic tiles directly and provides greater color intensity and a wider color gamut.

Printing spatially-varying reflectance for reproducing HDR images

We present a solution for viewing high dynamic range (HDR) images with spatially-varying distributions of glossy materials printed on reflective media. Our method exploits appearance variations of the glossy materials in the angular domain to display the input HDR image at different exposures. As viewers change the print orientation or lighting directions, the print gradually varies its appearance to display the image content from the darkest to the brightest levels. Our solution is based on a commercially available printing system and is fully automatic. Given the input HDR image and the BRDFs of a set of available inks, our method computes the optimal exposures of the HDR image for all viewing conditions and the optimal ink combinations for all pixels by minimizing the difference of their appearances under all viewing conditions. We demonstrate the effectiveness of our method with print samples generated from different inputs and visualized under different viewing and lighting conditions.

Printing spatially-varying reflectance for reproducing HDR images

We present a solution for viewing high dynamic range (HDR) images with spatially-varying distributions of glossy materials printed on reflective media. Our method exploits appearance variations of the glossy materials in the angular domain to display the input HDR image at different exposures. As viewers change the print orientation or lighting directions, the print gradually varies its appearance to display the image content from the darkest to the brightest levels. Our solution is based on a commercially available printing system and is fully automatic. Given the input HDR image and the BRDFs of a set of available inks, our method computes the optimal exposures of the HDR image for all viewing conditions and the optimal ink combinations for all pixels by minimizing the difference of their appearances under all viewing conditions. We demonstrate the effectiveness of our method with print samples generated from different inputs and visualized under different viewing and lighting conditions.

The Effect of Acrylic Emulsion on Coated Paper Properties

This study was carried in order to manufacture the high quality coated paper. High quality includes not only physical and optical properties of coated paper but also final print quality. In this study, new acrylic-styrene emulsion was polymerized in laboratory and compared with conventional styrene-butadiene latex. Low-shear viscosity of coating color was decreased with increasing acrylic-emulsion dosage. Small amount of acrylic emulsion addition increased water retention, but further addition decreased it. Acrylic-emulsion addition improved paper gloss, brightness and whiteness, but decreased PPS and opacity slightly. Ink gloss was increased with using No. 3 acrylic-emulsion due to lower ink setting properties. However No. 1 and 2 emulsion showed the opposite result. Surface strength of coated paper was increased with using No. 3 acrylic-emulsion. These results indicate that high quality coated paper can be manufactured with using No. 3 acrylic-emulsion.

Study on Coating Surface Topography and Properties of Coated Paper Related to Pigment

The physical structure and chemical properties of coating layer have an important influence on transferring and setting of the printing ink. In this study, the effect of pigment on coating layer structure and surface properties was investigated. The surface topography was explored using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The findings indicated that the pigment affected the pore size, depth and distribution of the coated paper surface. The conclusions were drawn that coating could improve coating surface topography and calcium carbonate pigment compared with kaolin pigment was not good to the paper surface properties, which resulted in high roughness, low paper gloss, high ink absorption and low paper surface efficiency.

Test Methods for the Water Sensitivity of Photobooks

Water sensitivity is one of the potential degradation routes of digitally printed images. ISO standards 2836 and 18935 are test methods for water fastness. These are shown to have limited application to some water fastness failure routes of printed images in books. As a result they only have limited applicability to the emerging photobook technologies.ISO 18935 contains 3 test methods. These test the resilience of a print to water spill, wet wiping and total immersion. However, these water exposure routes are not always pertinent to images within books which often spend most of their lifetime closed. In this case the water exposure is commonly by percolation through the exposed edge, resulting in chromatography effects on the exposed image, a very different scenario than those covered in ISO 18935. This renders ISO 2836 less useful too.The paper proposes a suitable test object and geometry for testing printed images within books. The strengths and weaknesses of this approach to in-book testing of images are also examined and the reasons for this choice of geometry are covered.The work concentrates on various plain, uncoated papers to best illustrate the effects and examines ink / media interactions using a number of different ink sets. The effect of UV brighteners within the paper is also examined as a part of this work.This work examines the issues around water sensitivity of inkjet prints within books and as such has direct relevance to photobook assemblies. As such it aims to form the basis for an extension to ISO 18935 to these increasingly important media for photographic hard copy.

Colorant Selection for High-Fidelity Color Reproduction

Recently, with the advent of printers with more than four colorants, the development of selection and optimization for colorant has been an important area of research in color printing. In former studies , gamut volume are the main criterions for colorant selection, and they mainly select colorant from ink sets , which have the biggest gamut volumes. In this paper we proposed other important criterions for selection , such as hue angle, chroma of colorant and then applied these criterions for practical colorant selection.

Investigation into the Coating Surface Topography and Properties of Paper Related to Drying Condition

The physical structure and chemical properties of coating layer have an important influence on transferring and setting of the printing ink. The typical objective of coating is to improve the appearance and printing properties of paper. In this study, the effect of drying condition on coating layer structure, surface properties, and print quality was investigated. The relationship between surface topography and drying condition was explored using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The conclusions were drawn that high and low drying temperature were not good to the paper properties, which resulted in high roughness, low paper gloss, high ink absorption, low print gloss and paper surface efficiency. The findings indicated that the coating drying temperature affected the pore size, depth and distribution of the coated paper surface. Moderate temperature was benefit to pigment particles and binder arranging orderly, which made the coating surface had high smoothness, gloss, paper surface efficiency, and modest ink absorption.

The chromatographic separation of anionic dye in inkjet coating structures

During the ink setting process on coated inkjet paper, the porosity and pore size distribution of the coating structure determines how much, in which direction and at what speed the surface can absorb the ink. The capillary and permeation flow drives the liquid into the structure and controls the volume flow, respectively. The coating binder, quite often polyvinyl alcohol, has an effect on the inkjet ink imbibition by occupying a proportion of the available pore volume and absorbing via swelling of the polymer matrix. The aim of this work is to clarify the role of the porous structure and the coexistent swelling of binder during the liquid imbibition, with special attention paid to the fixation of dye and its distribution during the chromatographic separation process. The results confirm that water molecules diffuse into and within hydrophilic polyvinyl alcohol binder causing the binder swelling. The swelling affects the number of active small pores remaining available for capillarity, by reducing the diameter and volume of the remaining free pores, thus slowing the capillary flow, such that the permeation flow rapidly becomes the rate determining step rather than the desired fine capillary-driven liquid imbibition. On the other hand, water molecules diffusing into the binder structure open the polymer network so that the colorant molecules can also fit into it. This mechanism is reflected in the observation that, in the case of dye-based inks, there is always a clear (non-coloured) wetting front advancing before the colour front. The swelling binder, therefore, though reducing absorption dynamic, does act to provide sorbtion volume and surface for colorant, aiding an otherwise coating surface area limited function in respect to dye capture and fixation.

HANS – Unlocking New Print Control Alternatives By Bringing Color Separation And Halftoning Closer Together

Color separation is currently used to decide how much of each available colorant to use for each printable color and halftoning then builds patterns that meet those choices. Print color, however, depends not only on how much of each colorant is used, but also on how those colorants are superimposed. Furthermore, there are many halftone patterns that correspond to a given combination of ink amounts. HANS (Halftone Area Neugebauer Separation), which we introduced at last year's IS&T's CIC conference, is a move towards specifying halftone pattern statistics and enables control over print properties beyond their current limits. While the benefits of HANS for color gamut and ink use efficiency have been shown, at this year's NIP, we would like to look more closely at how to determine the set of all possible halftone patterns that match a given color and demonstrate how access to such sets – metamer sets – benefits print control. We will also illustrate how even for a simple CMY ink set, which using current approaches leads to exactly one ink combination per printable color, there are sets of alternative halftone patterns that match a given color. Such sets in turn allow for tradeoffs to be made, e.g., between grain and ink use, even in this simple case.

The Performance of Computerized Spectrum Color Matching Based on Kubelka-Munk Theory and its Color Rendering on Offset Ink Sets

The purpose of the study intended to examine the performance of color rendering based on a computerized spectrum color matching (CSCM) method derived from the Kubelka-Munk theory. In the study, we prepared 2 offset ink sets to produce 30 standard color samples sets. The target color samples were measured by spectrophotometer to compare with the predicted values calculated by the CSCM model. The results showed that average measured color difference (∆E) via CIE L*a*b* and CIE DE2000 formulas between samples and CSCM predicted values averaged 5.89, 3.72 (∆Es), 6.94, 4.22(∆Epv), respectively. The measurements were fallen out the acceptable range of the tolerance of the industrial printing standards. The verification of CFI (Curve Fit Index) test came out with the same conclusion. As a result, we found that the computerized color matching formula derived from Kubelka-Munk theory still required further fine-tuning and more in-depth analysis. In addition, the reflectance database of the ink sets was another important factor affecting the performance of computer color matching model for precise colors prediction.

Use of confocal laser scanning microscopy and a computer model to understand ink cavitation and filamentation

In the offset printing process, ink film splitting has an important impact on formation of ink filaments. The filament size and its distribution influence the leveling of ink and hence affect ink setting and the print quality. However, ink filaments are difficult to image due to their short lifetime and fine length scale. Due to this difficulty, limited work has been reported on the parameters that influence filament size and methods to characterize it. We imaged ink filament remains and quantified some of their characteristics by changing printing speed, ink amount, and fountain solution type. Printed samples were prepared using a laboratory printability tester with varying ink levels and operating settings. Rhodamine B dye was incorporated into fountain solutions to aid in the detection of the filaments. The prints were then imaged with a confocal laser scanning microscope (CLSM) and images were further analyzed for their surface topography. Modeling of the pressure pulses in the printing nip was included to better understand the mechanism of filament formation and the origin of filament length scale. Printing speed and ink amount changed the size distribution of the observed filament remains. There was no significant difference between fountain solutions with or without isopropyl alcohol on the observed patterns of the filament remains.

Calendering Effects on Coating Pore Structure and Ink Setting Behavior

Coating layer pore structure significantly affects surface appearance, optical properties, and print-ability performance of multiply coated papers. Generally, fast ink setting can be realized by use of fine pigments, or pigments with steep particle size distribution. Ink-paper interaction of coated papers also changes significantly in calendering. The objective of this study was to better understand the influence of calendering on the pore structure of multilayered coated papers and to highlight the effect of this pore structure change on ink setting behavior. Laboratory calendering trials demonstrated that the pore structure of calendered paper is reduced with increased calendering temperatures. Mercury porosimetry and image analysis of scanning electron microscope images of calendered papers highlighted the gradual reduction of total pore volume, which, in combination with the reduced surface porosity, resulted in slower ink setting. If ink setting speed is to be preserved, calendering at low surface temperatures and a higher number of nip passes is preferred to reach a desired paper gloss level. Results also were compared to common theoretical models for liquid penetration into porous structures. These models can also be used to describe the influence of calendering-induced pore structure changes on ink setting. This work demonstrates optimization of calendering parameters to reach a balance for paper gloss and ink setting. The optimum depends on the machine equipment available and has to be checked separately for each concept of multiply coated paper and calender conditions.

Evaluation of Plasma-Deposited Hydrophobic Coatings on Pigment-Coated Paper for Reduced Dampening Water Absorption

Hydrophobic plasma coatings were deposited on pigment-coated paper with the purpose of reducing dampening water absorption and create uniform surface chemistry. The influence of plasma coatings on sheet-fed offset printability was also studied. Three plasma chemistries, fluorocarbon, organosilicon and hydrocarbon, were used to adjust the hydrophobicity of paper surface. The plasma coatings reduced, and in some cases prevented, the dampening water absorption into pigment-coated paper in both laboratory and pilot scale trials. Ink transfer, mottle and ink setting were altered due to the presence of the plasma coatings, whereas porosity and surface strength of the pigment-coated papers were not affected. These results suggest that the preferred way to improve the print quality with both mineral and linseed oil-based inks is to use plasma chemistry that modifies the paper surface to be both hydrophobic and oleophilic. Hydrophobic and oleophobic surfaces were found to cause ink repellence. Uniformity of the plasma coatings was crucial for obtaining an even print appearance.

Characterization of Ink–Paper Coating Adhesion Failure: Effect of Pre-dampening of Carbonate Containing Coatings

To attain an improved knowledge about ink–paper coating adhesion during offset printing, we have developed a laboratory procedure to measure adhesion failure between ink and coated paper during ink setting. This paper describes the technique and a special case where two ground calcium carbonate (GCC)-based coatings have been printed, one normal coating containing the delivered amount of dispersing agent already present in a typical GCC slurry and another coating made from the same GCC slurry but with excess additional free dispersant in the form of sodium polyacrylate. The areas where the ink–paper coating adhesion had failed at the pull-off points after tack testing were characterized by determining white spots in the retained print using image analysis. The white spots represent areas where ink has detached from the coating after contact with a rubber coated cylinder. This area is referred to as ink–paper coating adhesion failure area (IPCAFA). A minimum in IPCAFA at the point of maximum in tack force was found for both coatings where the print was applied onto dry coating. When the coatings, however, were pre-damped, IPCAFA increased on the normal coating over a short time period, independent of the dampening level. For the coating with excess dispersant, on the other hand, the higher dampening level strongly increased the IPCAFA. The strong impact of excess dispersing agent in this work may be explained by a number of related effects, including increased polarity of the coating surface, an associated moisture layer and an effective reduction of fine pores due to water-swelling polyacrylate that blocks these pores.

Printing spatially-varying reflectance

Although real-world surfaces can exhibit significant variation in materials --- glossy, diffuse, metallic, etc. --- printers are usually used to reproduce color or gray-scale images. We propose a complete system that uses appropriate inks and foils to print documents with a variety of material properties. Given a set of inks with known Bidirectional Reflectance Distribution Functions (BRDFs), our system automatically finds the optimal linear combinations to approximate the BRDFs of the target documents. Novel gamut-mapping algorithms preserve the relative glossiness between different BRDFs, and halftoning is used to produce patterns to be sent to the printer. We demonstrate the effectiveness of this approach with printed samples of a number of measured spatially-varying BRDFs.

Effect of latex on surface structure and wetting of pigment coatings

The amount and type of latex binder has a significant effect on both the structure and chemical properties of pigment coatings, which affects critical surface properties, e.g., gloss, ink setting rate via liquid absorption, and spreading properties. Increased knowledge is required for improved optimization in practical applications of pigment coating layers. To this end, the effect of binder amount for two different styrene–butadiene latices in kaolin pigment coatings on a base paper was studied, by measuring the surface topography, surface chemistry, and liquid absorption of these coatings. The topography was thoroughly analyzed from nanometer to millimeter length scales by atomic force microscopy (AFM), confocal optical microscopy (COM), and X-ray tomography. The area fractions of latex and pigments on the surface of the coating were determined from AFM phase contrast images, and the contact angles for pure latex and kaolin fractions were determined by using the Cassie equation. An explicit value for the effective surface area of the coatings was determined from the topographic data, which was used for determining the Wenzel correction for the contact angles. Work of adhesion and surface energy components were determined for the samples using three different methods (Owens–Wendt, Wu, vOCG). The latex was found to be evenly distributed over the surfaces, based on AFM phase imaging and ToF–SIMS mapping. The latex binder amount significantly affected the wetting behavior and interfacial properties of the coating layer. The results of this fundamental study can be used for optimization of functional properties of pigment coating systems by regulation of the amount and properties of their latex binder.

A review of modified surfaces for high speed inkjet coating

There are many interaction phenomena occurring between inks and the printed surface during the inkjet ink setting and drying process on coated papers. First, the ink wets the surface and then absorption into the capillary network occurs. After milliseconds, the colourant and solvent/diluent parts of the ink separate. Wetting of the coating surface, and the interior of the capillary network, depends on the relative surface energies of the components being brought into contact, and their interaction may include selective adsorption. Additionally, diffusion phenomena occur a few seconds after the ink arrives at the surface, which may be vapour dependent or liquid–liquid and liquid–solute concentration dependent. The final ink drying and polymerization can last for hours. The interactions have a direct connection to the final print quality. The most important properties of the coated surface are the porous structure parameters – pore size, amount and the network they form – and the chemical nature. In the beginning, at the first contact of the ink with the surface, the chemical properties of the coating layer and the ink dominate. As the mobile ink components penetrate deeper into the coating structure, the pore structure becomes more important. In some cases, depending on the nature of the binder (water soluble and/or emulsion polymer-based), the ink diluent or solvent may enter the intermolecular structure of the binder of the coating layer by diffusion, and the binder often swells as a result. A more hydrophilic binder in contact with water-based ink swells more than the one that is less hydrophilic. The most important control parameters in designing inkjet print surfaces, from the point of view of ink spreading and penetration, are the porosity, permeability, thickness/bulk, sizing (hydrophobizing), moisture content, temperature, and capillary structure of paper. Depending on whether an ink is dye-based or pigment-based, a main aspect that affects the print quality is the distribution and permanence of the colourant. The aim, in the inkjet ink setting process, apart from providing a dried ink surface, is to fix the colourant part of ink at or in the uppermost layer of the coating whilst allowing the diluent/solvent part of ink to penetrate deeper into the structure. Proper colourant fixation produces high optical print density, bright colour tones, high sharpness, low bleeding, low print-through, and high rub and wet resistance.

Py/GC/MS characterisation of naturally and artificially aged inks and papers

A set of inks was analyzed using Py/GC/MS technique. They were prepared following some ancient Armenian recipes and then analyzed after being dried in air to obtain solid samples. A simple analytical procedure was adopted which excludes any treatment of the samples and consists in introducing the solid sample directly into the injector of the furnace pyrolyzer. Inks were also written on whatman paper by calamum and analyses of papers containing ink were carried out. A real sample analysis was reported. Comparing the pyrograms it was possible to discriminate fragments derived from ink, from that formed by the decomposition of paper by the influence of ink. In order to understand the origin of the fragments formed during the pyrolysis of inks the standard compounds used to prepare them were carried out, too.