The objective of this study was to evaluate and compare the print performance of some of the new most promising, cost effective absorbent pigments specialised for inkjet coatings on the market in a continuous drive to find an alternative to silica. The target was a lower production cost for ArjoWiggins inkjet products, OMD 01 and OMD 02. Five absorbent pigments are being evaluated through measuring the qualities of the coating mix itself, visual evaluations of print performance and physical testing of the coated paper. Pigments 1,2 and 3, which all are said to be tailored for inkjet coatings, did not reach the print performance needed for an OMD 01 and OMD 02 equal, due to severe bleed and feathering identified especially on the Epson 950 printer. They are therefore currently not seen as viable formulations. A blend of 50% pigment 5 and 50% silica had excellent print performance as OMD 01 and OMD 02 equivalents and is therefore recommended as a potential alternative to 100% silica. It is of the company’s interest to find a more cost effective solution to their inkjet coatings, and a 50/50 blend of Pigment 5 will save the company more than 35 000 euro per year.

Die vorliegende Arbeit befasst sich mit der Anwendung von intelligenten Technologien in der online-Kontrolle von Druckprodukten. Ausgehend von der Qualität der Druckprodukte und den Möglichkeiten der Kontrolle von Druckqualität direkt im Herstellungsprozess werden Lösungen der Druckbildkontrolle diskutiert. Den Kern der Arbeit bildet die Anwendung intelligenter Technologien, wie Fuzzy Logic oder Neuronale Netze, in der Kontrolle von Druckbildern. Aufgrund der Generalisierungsmöglichkeiten und der Modularität der untersuchten Algorithmen eignen sich die beschriebenen Ansätze zur Implementierung in ein Druckkontrollsystem oder in andere zeitkritische Bildverarbeitungssysteme.

Flexographic printing is a common printing method in the packaging field. The printing method is characterized primarily by the flexible printing plate and the low viscosity inks which make it suitable for use on almost any substrate. The object of this study was to obtain further knowledge of the some important mechanisms of flexographic printing and how they influence the print quality. The thesis deals with printing primarily on board and liner but also on newsprint with water-borne ink using a full-scale flexographic central impression (CI) printing press. Several printing trials have been performed with a focus on the chemical interaction between the ink and substrate and the physical contact between the ink-covered printing plate and the substrate. Multicolour printing exposes the substrate to water from the water-containing ink. The emphasis was to investigate the relation between print quality and water-uptake of the paper surface with heat and water. Printing trials was carried out on substrates possessing a hydrophobic, and also a rather hydrophilic surface using a regular commercial water-borne ink. The favorable effect which water or surfactant solution had on the hydrophobic substrate with regard to print mottle could depend on its surface compressibility in combination with the hydrophobic nature of its surface that could affect the wetting properties. Conventional printing involves physical contact between plate and ink and between ink and substrate. A method for measuring the dynamic nip pressure using thin load cells is presented. Print quality was influenced by the plate material. A correction procedure taking into account the size of the sensor was developed in order to estimate the maximum dynamic pressure in the printing nip. An attempt was made to identify essential mechanical and chemical parameters, and also geometrical properties of the plate that affected print quality. Laboratory printing trials were carried out and a multivariate analysis was applied for evaluation of print quality data. The impact of the plate properties on print quality was evident. The essential properties of the plate that influence print quality were the small-scale roughness and long-scale roughness.

<p>U disertaciji su prikazana istraživanja vezana za objektivnu i subjektivnu,<br />psihofizičku metodu koja u eksperimentu utvrđuje koliki uticaj imaju različiti<br />parametri rasterizacije kao i dimenzija posmatrane slike na percepciju<br />realističnog prikaza i zrnaste strukture uz poređenje sa objektivnim metodama<br />obuhvaćenim eksperimentalnim merenjima. U metodologiji istraživanja su<br />korišćeni uzorci rastrirani sa dva različita tipa rastera frekventno<br />modularni i amplitudno modularni. Poznatim i priznatim naučnim metodima<br />obrade podataka došlo se do relevantnih rezultata koji potvrđuju različitost<br />posmatranih reprodukcija i model kontrole parametara rasterizacije.</p> / <p>The research presented in this dissertation is related to the image reproduction quality<br />assessment. Dissertation was designed to determine the impact of halftone attributes<br />on image quality. Objective and subjective quality assessment results were designed<br />to complement recently published findings for quality assessment. These attributes are<br />directly dependent on the chosen halftoning method. In this research the samples were<br />halftoned using two different types of screening methods: frequency modulated and<br />amplitude modulated method. Experiment data samples, were analysed by adequate<br />statistical methods. Results indicate significant influence of halftoning method on the<br />quality assessment and defines control model.</p>

The aim of this work was to develop a solid knowledge on formulation effects controlling offset ink-paper coating adhesion and to identify key factors of the coating and printing process affecting it. Focus lay on comprehending the impact of pigment dispersant on ink-paper coating adhesion and ultimately on the print quality of offset prints. The work covers laboratory studies, a pilot coating trial designed to produce coated material with a span in surface chemistry and structure, and an industrial offset printing trial. The lab scale studies quantified ink-paper coating adhesion failure during ink setting with a developed laboratory procedure based on the Ink-Surface Interaction Tester (ISIT) and image analysis. Additional polyacrylate dispersant resulted in slower ink setting and reduced ink-paper coating adhesion, with a dependence on its state of salt neutralisation and cation exchange, mainly in the presence of moisture/liquid water. The industrial printing trial on pilot coated papers was designed to study how these laboratory findings affected full scale offset print quality. These trials confirmed the dispersant-sensitive effect on ink-paper coating adhesion, especially at high water feeds. Evaluation of prints from the printing trial resulted in two fundamentally different types of ink adhesion failure being identified. The first type being traditional ink refusal, and the second type being a novel mechanism referred to as ink-lift-off adhesion failure. Ink-lift-off adhesion failure occurs when ink is initially deposited on the paper but then lifted off in a subsequent print unit. In this work, ink adhesion failure by this ink-lift-off mechanism was observed to occur more often than failure due to ink refusal. Print quality evaluation of the industrial prints suggested that water induced mottle was caused by a combination of ink-surface adhesion failure, creating white spots on the print, together with variation in ink layer thickness due to emulsified ink. / <p>QC 20161019</p>

<p>Print mottle is a problem that has been hassling the printing business for a long time. Along with sharpness and correct colour reproduction, absence of print mottle is one of the most important factors of print quality. The possibility to measure the amount of print mottle (reflectance variation) may in many ways facilitate the development of printing methods. Such a measurement model should preferably follow the functions and abilities of the Human Visual System (HVS). </p><p>The traditional model that STFI-Packforsk has developed to measure print mottle uses frequency analysis to find variations in reflectance. However, this model suffers some limitations since is does not perfectly agree with the functions of the HVS and does only measure variations in lightness. A new model that better follows the functions of the HVS has thus been developed. The new model does not only consider variations in lightness (monochromatic) but also variations in colour (chromatic). The new model also puts a higher weight on systematic variations than on random variations since the human eye is more sensitive to ordered structures. Furthermore, the new model uses a contrast sensitivity function that weights the importance of variations in different frequencies. </p><p>To compare the new model with the traditional STFI model, two tests were carried out. Each test consisted of a group of test patches that were evaluated by the traditional STFI model and the new model. The first test consisted of 15 greyscale test patches that originated from conventional flexo and offset presses. The second test consisted of 24 digitally simulated test patches containing colour mottle and systematic mottle. </p><p>The evaluation results in both the traditional and the new model were compared to the results of a visual evaluation carried out using a panel of test persons. The new model produced a result that correlated considerably better with the visual estimation than what the traditional model did.</p>

<p>The appearance and design of a package are key properties to attract and to focus the attention of a customer. Print quality contributes to a great degree to achieve these requirements. Most critical perceived in terms of quality are print defects like mottling, gloss and stripiness, which all appear in the printing of corrugated board. Stripiness is especially critical because it is a defect directly caused by the corrugated board construction. A further cause can be generated by the production process of corrugated board. Pre-studies by Odeberg Glasenapp (2004) revealed a difference in surface micro-roughness between the regions on the peak line of the liner and the regions in the valley between two peaks of the corrugation. This knowledge was the basis for the work described in this thesis.</p><p>In a first stage, laboratory trials were conducted with sets of coated and uncoated samples of various grammages. The trial was set-up in order to simulate the conditions in the corrugator as closely as possible. In the evaluations, it was found out that the settings were too high. For that reason, the coated samples were influenced to a too high degree and needed to be excluded from further evaluations. With the uncoated samples, on the other hand, a change in micro surface roughness was detectable. The roughness is decreased on the peaks and the gloss appearance was the conclusion. The analysis of the printed samples focused on shifts in colour and print density. It is unclear if both are affected only surface roughness changes and/or by the typical corrugated board effect of washboarding.</p><p>A full-scale test was performed in order to confirm the results of the laboratory test. A test series was chosen with coated and uncoated outer liners. Contrary to the lab-test results, the uncoated grades showed no surface roughness changes. Instead, the coated samples were affected to a great extent. The changes in surface roughness and gloss appearance were similar to the lab-test. This confirms that the lab-test samples were exposed to heat, pressure and shear to a too high degree. The print analysis of the full-scale test did not agree with the laboratory test. Gloss lines were visually detectable, but they were difficult to measure. A reason could be that the ink is capable on forming an ink film layer on top of the surface of the paper. This would cover the micro roughness of the matt parts thereby creating an almost homogeneous glossy appearance.</p>

Print mottle is a problem that has been hassling the printing business for a long time. Along with sharpness and correct colour reproduction, absence of print mottle is one of the most important factors of print quality. The possibility to measure the amount of print mottle (reflectance variation) may in many ways facilitate the development of printing methods. Such a measurement model should preferably follow the functions and abilities of the Human Visual System (HVS). The traditional model that STFI-Packforsk has developed to measure print mottle uses frequency analysis to find variations in reflectance. However, this model suffers some limitations since is does not perfectly agree with the functions of the HVS and does only measure variations in lightness. A new model that better follows the functions of the HVS has thus been developed. The new model does not only consider variations in lightness (monochromatic) but also variations in colour (chromatic). The new model also puts a higher weight on systematic variations than on random variations since the human eye is more sensitive to ordered structures. Furthermore, the new model uses a contrast sensitivity function that weights the importance of variations in different frequencies. To compare the new model with the traditional STFI model, two tests were carried out. Each test consisted of a group of test patches that were evaluated by the traditional STFI model and the new model. The first test consisted of 15 greyscale test patches that originated from conventional flexo and offset presses. The second test consisted of 24 digitally simulated test patches containing colour mottle and systematic mottle. The evaluation results in both the traditional and the new model were compared to the results of a visual evaluation carried out using a panel of test persons. The new model produced a result that correlated considerably better with the visual estimation than what the traditional model did.

<p>U disertaciji je izvršena karakterizacija sliv nosioca flekso<br />štamparskih formi i predstavljena su istraživanja uticaja promene<br />mehaničkih i adhezivnih svojstava slivova na parametre kvaliteta<br />štampe kartonske ambalaže. Korišćene su dve grupe samolepljivih<br />slivova (potpuno novi i slivovi korišćeni za štampu 5.000.000 m<br />materijala). Ciljevi istraživanja su povećanje predvidivosti i<br />konstantnosti kvaliteta štampanog proizvoda i procesa proizvodnje<br />kartonske ambalaže, formiranje preporuka za upotrebu slivova<br />različitih svojstava i nivoa eksploatisanosti i otkrivanje u kojim<br />fazama i kojim procesima dolazi do promena svojstava slivova.</p> / <p>Research presented in this dissertation includes characterization of<br />flexographic sleeves and the study of the influence of the changes in<br />mechanical and adhesive properties of the sleeves on print quality<br />parameters of the cardboard packaging. Two groups of self-adhesive sleeves<br />were used (entirely new and sleeves used for printing of 5.000.000 m of<br />material). Aims of the research are the increase in predictability and stability<br />of the printed product quality and the production process of cardboard<br />packaging, forming of the recommendations for the use of sleeves with<br />different properties and levels of exploitation, as well as defining the phases<br />and processes responsible for the changes in sleeve properties.</p>

Die vorliegende Arbeit befasst sich mit der Anwendung von intelligenten Technologien in der online-Kontrolle von Druckprodukten. Ausgehend von der Qualität der Druckprodukte und den Möglichkeiten der Kontrolle von Druckqualität direkt im Herstellungsprozess werden Lösungen der Druckbildkontrolle diskutiert. Den Kern der Arbeit bildet die Anwendung intelligenter Technologien, wie Fuzzy Logic oder Neuronale Netze, in der Kontrolle von Druckbildern. Aufgrund der Generalisierungsmöglichkeiten und der Modularität der untersuchten Algorithmen eignen sich die beschriebenen Ansätze zur Implementierung in ein Druckkontrollsystem oder in andere zeitkritische Bildverarbeitungssysteme.