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From the moment of production, paper as a printing substrate is exposed to the process of natural ageing regardless of the type of cellulose fibres in its composition. Accordingly, the prints produced by the various printing techniques are also exposed to several factors that impair the quality of the print i.e. its colour over time. Therefore, it is very important to properly select the printing substrate for achieving a high quality of graphic products. For that purpose, three types of papers with hemp fibres were used as printing substrates which were printed with laboratory hand-operated instrument Esiproof using flexographic cyan (C), magenta (M), yellow (Y) and black (K) water-based inks. Prints were artificially aged in SunTEST XLS+ test chamber according to standard ASTM D 6789-02 for 48 and 96 hours. Based on changes in the reflectance spectra of each printed ink after exposure to electromagnetic radiation it was noticed how composition of printing substrate strongly influence on colour stability of prints due time. An increase of exposure time to electromagnetic radiation leads to a decrease in the value of the reflectance of the printing substrate and cyan, magenta and yellow prints. It was confirmed how electromagnetic radiation have the greatest impact on the reflectance of yellow print, while the black one is the most stabile regardless of the substrate it was printed on.

From the moment of production, paper as a printing substrate is exposed to the process of natural ageing regardless of the type of cellulose fibres in its composition. Accordingly, the prints produced by the various printing techniques are also exposed to several factors that impair the quality of the print i.e. its colour over time. Therefore, it is very important to properly select the printing substrate for achieving a high quality of graphic products. For that purpose, three types of papers with hemp fibres were used as printing substrates which were printed with laboratory hand-operated instrument Esiproof using flexographic cyan (C), magenta (M), yellow (Y) and black (K) water-based inks. Prints were artificially aged in SunTEST XLS+ test chamber according to standard ASTM D 6789-02 for 48 and 96 hours. Based on changes in the reflectance spectra of each printed ink after exposure to electromagnetic radiation it was noticed how composition of printing substrate strongly influence on colour stability of prints due time. An increase of exposure time to electromagnetic radiation leads to a decrease in the value of the reflectance of the printing substrate and cyan, magenta and yellow prints. It was confirmed how electromagnetic radiation have the greatest impact on the reflectance of yellow print, while the black one is the most stabile regardless of the substrate it was printed on. [ABSTRACT FROM AUTHOR]

To improve printing results, a printing form can be functionalized and the material transferring behavior can be adjusted. In this work, a flexographic printing form is divided into three different areas: first the elevated, material transferring structures (1); second the rising edges between the printing form substrate and the elevated structures (2); and third the transition area (3) between (1) and (2). These three areas are laser functionalized by inserting a defined micropattern. Subsequently, the printing results are investigated and categorized into groups. The groups indicate which functionalized surfaces (1, 2, and 3) have what kind of influence on the printing result. As part of a low cost and efficient approach to manufacture polymeric optical waveguides, a way is presented to show how the waviness of printed conditioning lines can be reduced significantly by laser functionalizing to improve the quality of the waveguides. [ABSTRACT FROM AUTHOR]

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The aim of this work was to study the influence of primary and secondary hydroxyl groups in the branched polyglycerol on the selected properties of water-based printing ink and copies printed with water-based flexographic printing inks. The branched polyglycerols were synthesized through anionic ring-opening polymerization using trimethylolpropane as a starting material. Obtained polyglycerol exhibited an irregular structure containing primary and secondary or predominantly primary hydroxyl groups in the macromolecule. The analysis (FTIR, 1H NMR, 13C NMR) confirmed the structure of polyglycerols. Obtained polyglycerols were then used as a performance additive in a water-based flexographic printing ink. The contact angles of the printing inks on the printing base were measured. The impact of a small amount of branched polyglycerol on the printing ink color was examined by studying the optical density of a full-tone area, the color values (CIELAB), the total color difference ΔEab∗, and gloss of the dried ink film. In general, the addition of branched polyglycerol containing only primary hydroxyl groups improved the wettability of the plastic film and gloss of printing ink with an acceptable total color difference ΔEab∗ in contrast to branched polyglycerol with primary and secondary hydroxyl groups. [ABSTRACT FROM AUTHOR]

Model elastic inks were formulated, rheologically characterised in shear and extension, and printed via flexography to assess the impact of ink elasticity on print uniformity. Flexography is a roll-to-roll printing process with great potential in the mass production of printed electronics for which understanding layer uniformity and the influence of rheology is of critical importance. A new set of flexo-printable Boger fluids was formulated by blending polyvinyl alcohol and high molecular weight polyacrylamide to provide inks of varying elasticity. During print trials, the phenomenon of viscous fingering was observed in all prints, with those of the Newtonian ink exhibiting a continuous striping in the printing direction. Increasing elasticity significantly influenced this continuity, disrupting it and leading to a quantifiable decrease in the overall relative size of the printed finger features. As such, ink elasticity was seen to have a profound effect on flexographic printing uniformity, showing the rheological tuning of inks may be a route to obtaining specific printed features. [ABSTRACT FROM AUTHOR]

Considering the increasing amount of data for communication and infotainment applications, fabrication of optical networks and bus systems is a challenging task for production engineering. A two-step manufacturing process for polymer optical waveguides is presented. By improving the highly efficient flexographic printing technology by laser functionalization of the printing tool in combination with a subsequent spray application, high-quality waveguides are accomplished. By adjusting the resulting surface energy of the foil substrate in the first fabrication process, the spray application achieved high-aspect ratio waveguides with a low attenuation of 0.2dB/cm at 850 nm. [ABSTRACT FROM AUTHOR]

Water-based or flexographic inks in paper and plastic industries are more environmentally favourable than organic solvent-based inks. However, their use also creates new challenges because they remain dissolved in water and alter the recycling process. Conventional deinking technologies such as flotation processes do not effectively remove them. Adsorption, coagulation/flocculation, biological and membrane processes are either expensive or have negative health impacts, making the development of alternative methods necessary. Cellulose nanofibers (CNF) are biodegradable, and their structural and mechanical properties are useful for wastewater treatment. TEMPO-oxidised CNF have been evaluated for the decolourisation of wastewaters that contained copper phthalocyanine blue, carbon black and diarlyide yellow pigments. CNF in combination with a cationic polyacrylamide (cPAM) has also been tested. Jar-test methodology was used to evaluate the efficiency of the different treatments and cationic/anionic demand, turbidity and ink concentration in waters were measured. Results show that dual-component system for ink removal has a high potential as an alternative bio-based adsorbent for the removal of water-based inks. In addition, experiments varying CNF and cPAM concentrations were performed to optimise the ink-removal process. Ink concentration reductions of 100%, 87.5% and 83.3% were achieved for copper phthalocyanine blue, carbon black and diarlyide yellow pigments, respectively. Flocculation studies carried out show the decolourisation mechanism during the dual-component treatment of wastewaters containing water-based inks. [ABSTRACT FROM AUTHOR]

In this paper, the swelling properties of photopolymer flexographic printing plates related to the variations of UVC post-treatment have been analysed. The aim of the research was to interconnect the changes in the crosslinking degree of the photopolymer material occurring due to the modified UVC radiation of the printing plate and the changes of its surface free energy crucial in the graphic reproduction process. Changes in the crosslinking degree in the photopolymer materials have been analysed by the swelling experiments. Results have proven that the partial dissolution of the photopolymer material caused by the immersion of the printing plates in various solvents is in the direct relation with the changes of the dispersive surface free energy. UVC post-treatment, used for the crosslinking termination and the definition of the surface properties of printing plates, is therefore directly affecting the resistivity of the printing plate in the solvent environment. By calculating the correlation coefficients for the weight loss of the photopolymer material in solvents and the dispersive surface free energy, the relation between the crosslinking degree and the UVC post-treatment has been established. [ABSTRACT FROM AUTHOR]

ABSTRACT The object of this research was to perform, characterize, and apply the functional modification of flexographic photo polymeric printing plate surface by UVA and UVC post-treatments. Photo polymeric printing plates have an important application in functional printing, where new printing inks/coatings and substrate formulations are used and the specific qualitative requirements must be met. The limitations of materials and processes often require expensive reformulations of the functional inks to achieve printability. Results of this research showed that the modification of the photo polymeric printing plate surface at the end of its production process can be used to precisely adjust the printing ink transfer to the printing substrate and thus eliminate the need for changing the ink/coating composition. By applying specific UV post-treatment, one can create a flexographic coating deposition system of tailored properties adjustable to variable reproduction systems with high quality requirements. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43526. [ABSTRACT FROM AUTHOR]

This contribution deals with flexographic printing of nanoparticulate tin-doped indium oxide (ITO) inks for the manufacture of fine lines on PET foils and glass substrates. The development and optimization of ITO inks, based on solutions of water and ethanol, for the flexographic printing process is presented. The influence of the solvent composition, of the particle content, and of the molar mass of the binder polyvinylpyrrolidone on the printing result is shown. ITO lines with a minimum line width of around 120 μm were printed using a printing plate with a feature size of 50 μm; the ITO lines exhibited a thickness of around 1 μm. Laser post-treatment was used to consolidate the top layer of the nanoparticulate ITO structures resulting in improved electrical properties; low sheet resistance values of around 300 Ω/□ were achieved. [ABSTRACT FROM AUTHOR]

The effect of coating structure variations on flexographic print quality was studied using pilot-coated paperboard samples with different latex content and latex particle sizes. Two latexes, with particle sizes of 120 nm and 160 nm, were added at either 12 parts per hundred (pph) or 18 pph to the coating formulation. The samples were printed with full tone areas at print forces of 25 N and 50 N in a laboratory flexographic printing press using a water-based ink. A high ratio of uncovered areas (UCAs) could be detected for the samples that contained 18 pph latex printed at a print force of 25 N. UCAs decreased with increased print force and with decreased amounts of latex in the coating formulation. The fraction of latex covered area on the coating surface was estimated to be 0.35-0.40 for the 12 pph, and 0.70-0.75 for the 18 pph samples. The ink penetration depth into the coating layer could be linked to the fraction of latex-free areas on the coating surface. Optical cross section microscopy indicated that a higher printing force did not increase the depth of penetrated ink to any greater extent. Higher printing force did increase contact between plate and substrate, leading to an improved distribution of the ink. This, in turn, increased print density and decreased UCAs. On closer inspection, the UCAs could be categorized as being induced by steep topographic changes. When appearing at other locations, they were more likely to be caused by poor wetting of the surface. To understand the wetting behavior of the coating surface, observed contact angles were compared with calculated contact angles on surfaces of mixed composition. Application: The detrimental effects of surface heterogeneity can be overcome by increasing printing force. The results can be used to improve print quality by understanding the balance between surface properties and printing parameters. [ABSTRACT FROM AUTHOR]

A commercially available silver paste was modified to match the flexographic process requirements. Rotational and oscillatory rheological tests were carried out to assess the printability and spreading behaviour of the resulting inks. Then, a multifactorial approach was used on a laboratory-scale printing press to adapt the flexographic process for the front side metallisation of Cz-Si solar cells, especially for the seed layer deposit of two layer contacts. To quickly identify the significant process parameters, a fractional design of experiment based on a screening approach at two levels was performed. Afterwards, two full factorial designs of experiments were implemented. While the first one allows a better understanding of the effect of the main factors and interactions, the second allows a fine tuning and a confirmation of the first results. Additionally, this methodology allows corroborating the influence of the ink rheological properties on the printing results. Following the process study and optimisation, a seed layer with an average width of 25 µm was printed at a high 0.3 m/s throughput. Additional results suggest that the line width and the throughput can be further improved, which underlines the potential of flexography for photovoltaic applications. Finally, the light-induced process was used to thicken the seed layer after a standard firing-through step, leading to an encouraging 17.9% efficiency on Cz-Si solar cells. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Paper recycling systems based on flotation technologies are not efficient to deink secondary fibers from new printing technologies based on flexographic inks which, even being more environmentally friendly, still present some recycling problems. We have evaluated the efficiency of a biotechnological approach, based on the laccase-mediator system, for biodeinking of three flexographic inks (Blue 1, Magenta HX-E and Red 48:4) in the presence of several pulps (bleached pulp, deinked paper pulp from secondary fibers and pulp from commercial uncoated and coated office paper sheets). Two fungal laccases, one from the basidiomycete Coriolopsis rigida and the other from the ascomycete Myceliophthora thermophila , were used as catalysts in the presence of HBT (1-hydroxybenzotriazole) or methyl syringate, as models of synthetic and natural mediators, respectively. Higher decoloration rates were achieved for Blue 1 and Magenta HX-E than for Red 48:4. The best results were obtained using bleached pulps without additives. Then, to identify the chemical compounds that may hamper enzymatic biodeinking, the influence of several additives on ink decoloration and enzyme activity was tested. Only calcium carbonate slowed down ink decolorization by up to 40%, although it also decreased the mediator assisted enzyme deactivation. In this work, a system to evaluate the efficiency of the laccase-mediator system in biodeinking of flexographic inks in the presence of different pulps and papers has been developed. [ABSTRACT FROM AUTHOR]

TNowadays, flexographic printing process is the most cost-effective printing technique. Due to its capacity to produce very good print quality it is predominantly used for labelling and packaging applications. Additionally, flexography has become a very strong competition to the gravure printing process in performing more demanding printing tasks. In order to improve reproduction quality obtained by flexographic printing technique, some modifications in producing printing plates have been developed in the recent years. In this paper, two new technologies, DigiCap and SquareSpot, are presented. The aim of the research was to analyse and define the quality of reproduction obtained with DigiCap and SquareSpot technologies in the production of printing plates. The definition of the overall reproduction quality was determined using objective and subjective analysis. Three image quality attributes were observed: line reproduction quality, circularity of dots and dot gain in objective analysis. [ABSTRACT FROM AUTHOR]

The intention of the study was to improve the efficiency of total organic carbon (TOC) and colour removal from the wastewater samples polluted with flexographic printing ink following coagulation treatments with further adsorption onto activated carbons and ground orange peel. The treatment efficiencies were compared to those of further flocculation treatments and of coagulation and adsorption processes individually. Coagulation was a relatively effective single-treatment method, removing 99.7% of the colour and 86.9% of the organic substances (TOC) from the printing ink wastewater samples. Further flocculation did not further eliminate organic pollutants, whereas subsequent adsorption with 7 g/l of granular activated carbon further reduced organic substances by 35.1%, and adsorption with 7 g/l of powdered activated carbon further reduced organic substances by 59.3%. Orange peel was an inappropriate adsorbent for wastewater samples with low amounts of pollution, such as water that had been treated by coagulation. However, in highly polluted printing ink wastewater samples, the adsorption treatment with ground orange peel achieved efficiencies comparable to those of the granular activated carbon treatments. [ABSTRACT FROM AUTHOR]

Highlights: [•] Flexographic ink showed significant antibacterial activity with nano silver. [•] Antibacterial activity against Gram-positive and Gram-negative bacteria is good. [•] Flexographic ink characterization improved by adding nano silver. [Copyright &y& Elsevier]

Flexographic printing inks form electrosterically stabilized colloidal dispersions in water that display extreme stability at the alkaline pH values of most wastepaper deinking systems. A significant amount of U.S. newspapers are now printed using water-based flexographic inks, and the residual inks from these sources are problematic to remove in deinking plants. A successful flocculant for flexographic ink particles used in deinking plant filtrate streams requires that both the electrostatic and steric components of colloidal stabilization be eliminated simultaneously. The present study shows the advantageous characteristics of cupric chloride in achieving rapid flocculation of flexographic inks. Flocculation experiments were performed with a model ink as well as a mixture of offset and flexographic inks from recycled newspapers. The critical coagulation concentration of cupric chloride has been compared to other chloride, nitrate, and copper salts. Copper(II) chloride has been found to be significantly more effective than other such salts in achieving destabilization and aggregation of flexographic ink particles. A possible flocculation mechanism of flexographic ink particles by cupric chloride is presented. [ABSTRACT FROM AUTHOR]

Abstract: The use of new printing technologies based on flexographic inks hampers ink elimination during paper recycling, making necessary the development of alternative methods. Decolorization of four flexographic inks has been evaluated by using fungal laccases, three of them from basidiomycetes (Trametes villosa, Coriolopsis rigida, and Pycnoporus coccineus), and one from the ascomycete Myceliophthora thermophila in the presence of synthetic and natural mediators. The results obtained showed a higher capacity of the three basidiomycete laccases to decolorize flexographic inks as compared with M. thermophila laccase, a low redox potential laccase. Basidiomycete laccases decolorized inks without mediators at long reaction times, although the presence of natural or synthetic mediators (above all HBT) accelerated the process. On the other hand, M. thermophila laccase was unable to decolorize the inks assayed. The addition of syringyl-type mediators led to medium levels of decolorization except for R48 ink, which was almost completely decolorized. Most decolorization was obtained during the first hours of treatment, when all the basidiomycete laccases were fully active in the presence of mediators. As opposed to other basidiomycete laccases, which become inactive in the presence of HBT after 24h, the enzyme of P. coccineus was not deactivated by this mediator even after 48h. A complete loss of M. thermophila laccase activity was observed at short times with acetosyringone and methyl syringate, the only two mediators able to promote ink decolorization with this enzyme. [Copyright &y& Elsevier]

Abstract: The use of cross-flow ultrafiltration for the recovery of coating material from aqueous streams started about 30 years ago with electro-deposition paint in the automotive industry. This early success can be related to both environmental and economical advantages of using ultrafiltration. Ultrafiltration recovers and concentrates electro-deposition paint on the retentate side and produces purified water on the permeate side. Based on this success, the focus more recently moved to other coating materials, such as paper coatings, latex and flexographic ink. Similar to electro-deposition paint, the concept is to recover the diluted coating materials with ultrafiltration to obtain a solid-free permeate stream, which can be either recycled or easily treated, and a retentate stream, which contains the coating materials preferably at concentrations suitable for recycling or disposal. The advantages can be directly translated into very short payback times for ultrafiltration systems of typically less than two years. Application studies focusing on the coating recovery in a paper mill, the concentration of latex from the tank wash at a latex producer and the recovery of flexographic ink at a producer of printed cartons will highlight these benefits. [Copyright &y& Elsevier]

Tweets, or posts from the microblogging web site Twitter, on several topics, including the launch of the Digital Secure Print (DSP) technology, the impact of human traits on color perception and the projected 2020 value of the flexographic ink market, are presented.