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Evolutions in food packaging printing

You are here: Conferences & Events * 2011 Budapest * Abstracts * 2. Printing Materials

2. Printing Materials

2.07 Impacts on the impression of printed effect pigments

Martin Haas, Edgar Dörsam, Evgeny Kurmakaev, Thorsten Euler, Martin Schmitt-Lewen, Immanuel Fergen, Joachim Sonnenschein


Abstract
Effect pigments are more and more used to upvalue printed products in finishing processes. The main effect of these pigments is their changing color impression (color shift) depending on the viewing and illumination angle based on the physical effect of interference. Also higher gloss and sparkling effects can be achieved. While effect pigments of the first generation reflect color changes from a certain color to transparent, further developed pigments (second generation) allow changes from one to another color. The relative high pigment prices compared to those of common varnishes makes it interesting to use a highly effective printing process with a maximal utilization of the desired effects. In fact pigment manufacturer give considerations for the application of effect pigments by different printing processes. Nevertheless a general impact of print parameters to the effects caused by effect pigments has not been reported. Furthermore in printing praxis measurement systems for a quality control of the effects are rarely used. Printed products including effect pigments are often evaluated visually by the operators and customers.

The impacts of several print and material parameters on the impression of printed effect pigments are shown and discussed intensively. Based on the results of a systematic printing trial, general considerations for the operator to optimize the effects regarding customer-related issues like enhanced print quality and economic aspects are presented.


Keywords:
effect pigments, print parameters, design of experiments, print quality
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2.08 Screen printing with effective printing inks

Raša Urbas, Jana Rozman, Marta Klanjšek Gunde

Abstract

The quality of prints prepared by screen printing depends on relationship between mesh geometry and pigment particles which are transferred trough the mesh. Relatively simple relationships are valid for conventional inks which have uniform distribution of nearly round-shaped pigments. In such circumstances the fineness of the screen, its thickness and degree of opening determine printing properties.

The rather simple situation could change considerably if the ink contains flaky-shaped pigments. If flaky-shaped pigments are used in printing ink, the printing process should support the parallel orientation. The simple rules for conventional inks are not valid for inks with flaky pigments. Our research is devoted to get the connections between the mesh properties and print quality for such printing inks. Three different pigments were applied, two bright conductive and one interference pigment, with different lateral sizes, ranging from 59 up to 110 µm. They were applied in printing base in 5% and 20% mass concentration. The prepared printing inks were screen-printed on two papers, Biogloss and Biomatt. Two mesh densities were applied, 27 and 61 threads/cm. The quality of prints was analysed by scanning electron- and optical microscope, optical profilometer and /D geometry. The angle-dependent effects were judged?colorimetry in 8 visually.

It was found that higher density of meshes gives thinner layers, larger angle-dependent effects and sharp edges of prints. Larger concentration of flakes gives rise to higher disorder of flakes and poor angle-dependent effects. Wet on wet printing causes large deterioration of orientation. Smooth substrate surfaces support better orientation of flakes. The research on influence of these parameters on functional properties is going on.

Keywords:
screen printing, effect pigments, flakes, angle-dependent optical effects
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2.09 Pore structural changes in inkjet coatings by the inclusion of binders and additives

Cathy J. Ridgway, Vesa Kukkamo, Patrick A.C. Gane,

Abstract
This study considers pore volume loss in inkjet coating structures when using various binders and polymer additives. Starch is shown to prevent access to the crucially absorbing pores, and is non-absorbing. Polyvinyl alcohol (PVOH) absorbs up to ~30 % of its own weight of water, but acts to limit the absorption rate by reducing it to that of the interpolymer matrix diffusivity. PVOH also reduces the volume according to the binder filling internal pore space. Latex particulate binder can be used to allow continued access to the nanopore region by choosing the right glass transition temperature, Tg, and chemistry of the synthetic polymer. Similarly, the permeability can be maintained to a large extent. Water fastness requires that the coating be cationic, when considering anionic ink dyes. The added cationic polymer, such as PolyDadmac, itself reduces the available pore volume by distributing itself on the pigment surfaces and within pores. Linking pore volume loss to increased feathering and bleeding supports the need to re-consider the use of water soluble polymers and binders, and indicates that coating formulation optimisation, when using cost-effective porous pigments in inkjet coatings, points to the minimising of charge conversion requirements and the development of improved particulate binders.

Keywords: inkjet coatings, speciality inkjet pigments, formulating for inkjet coating, cationising, soluble binders
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