December 2015

Gorazd Golob





Modelling reflectance factor for special effect pigment coatings

Nina Rogelj1 and Marta Klanjšek Gunde2
University of Eastern Finland, Institute of Photonics, Joensuu, P.O.Box 111, Finland
2 National Institute of Chemistry, Ljubljana, Hajdrihova 19, Slovenia


A numerical model to calculate goniometric reflectance factor for effect coatings with interference flakes was developed and analysed here. The model incorporates three parts of the light scattering events; from the front surface of the coating, from pigments inside the coating, and from the coating substrate. In order to validate the model, reflectance spectra were measured at an incident angle of 45º and at reflected angles of −60º, −30º, −20º, 0º, 30º and 65º using a commercial multi-angle spectrometer. Metal lustre coating was used for testing the model. It contains Iriodin 4504 pigment, an interference mica-based pigment coated with iron (III) oxide from Merck. This coating includes all spectral characteristics involved in the model. The thickness of the interference layer on the pigments was adjusted to obtain good matches of interference features between modelled and measured reflectance factor. The influence of surface coverage by pigments and of the pigment orientation distribution on the resulting spectra was analysed. The first parameter represents the fraction of surface area covered with pigments and the second how well the pigments inside the coatings are oriented.

Keywords: appearance, scattering, spectrum, multi-angle reflectance, effect coating

JPMTR 069 | 1504 Original scientific paper
DOI 10.14622/JPMTR-1504
UDC 53.07 : 535.3 | 667.6

Received: 2015-08-10
Accepted: 2015-11-04

Ink adhesion failure during full scale offset printing: causes and impact on print mottle

Hajer Kamal Alm1, Göran Ström1, Joachim Schoelkopf2, Cathy Ridgway2 and Patrick A. C. Gane2*
Innventia AB, BOX 5604, SE-114 86 Stockholm, Sweden
2 OMYA Development AG, P.O BOX: 32, CH-4665 Oftringen, Switzerland
* (also) Aalto University, School of Chemical Technology, P.O. Box 16300, FI-00076 Aalto, Finland


The printing plate used in offset lithography is designed to accept ink on image areas and reject ink on non-image areas. In order to reject ink in conventional offset, fountain solution is needed to form a weak boundary layer between the plate and the ink. Paper and coated paper in particular are designed to accept ink and absorb ink oil and fountain solution. The latter is often transferred to the paper surface through the rubber blanket and its absorption or subsequent displacement is essential for final ink transfer to the surface. There are strong demands on the uniformity of the paper surface, including in respect to absorptivity, both in structure and chemistry, in order to gain a print of high quality. If this is not the case, the ink film thickness may be non-uniform; subsequently, ink adhesion may even fail completely, leaving white spots on the paper surface in the print. This gives rise to print mottle, a severe print quality defect.

The aim of this paper was to study the quality of prints from a full scale offset printing trial made on pilot coated paper, with attention given to ink-surface adhesion. Seven calcium carbonate pigment based coatings with different contents of pigment dispersing agent were included in this study. The work showed that a moderate over-dosage of dispersant significantly increased the ink adhesion failure and print mottle, mainly on prints from the later print units and especially at high fountain feed levels. These findings demonstrate the fundamental impact of fount level, surface chemistry and coating formulation on ink adhesion and thus also print mottle.

Keywords: coated paper, coating permeability, offset print quality, water induced print mottle, uncovered area, polyacrylic dispersant

JPMTR 070 | 1503 Original scientific paper
DOI 10.14622/JPMTR-1503
UDC 539.6 – 035.67 : 763

Received: 2015-06-23
Accepted: 2015-11-17

Soybean oil based inks for enhanced deinkability of litho prints

Veronika Husovska, Jan Pekarovic, Alexandra Pekarovicova and Paul D. Fleming III
Western Michigan University, Center for Recycling, Center for Ink and Printability, CEAS, A-231 Parkview, Kalamazoo, MI 49008-5462, US


Three types of food grade soybean oils were tested to determine if their byproducts could be utilized in the paper recycling industry. Free fatty acids were extracted from these commercially available soybean-oils. These acids were utilized in one loop air flotation deinking of litho-printed paper substrates. It was found that the three experimental fatty acids used in deinking differ in their chemical composition, namely Acid number and Saponification number. The effect of each of the soy-oil free fatty acid on deinking was studied, quantified and compared to the standard INGEDE 11p procedure. The INGEDE method employs commercially available oleic acid and experimental fatty acids were tested as its replacement. INGEDE method 11p was slightly modified due to unavailability of a Hobart type pulper. Therefore, a MicroMaelstrom™ Laboratory Pulper was used instead. The substrate used for deinkability study was heavily printed from both sides by sheetfed offset lithography. Due to heavy ink mileage, none of the four fatty acids had the power to deink such substrates in a one loop flotation recycling experiment. Besides INGEDE deinking evaluations, further deinking assessments were performed. Deinkability factors DEMLab and DEMf were used to express the success of ink removal from the pulp, since ERIC instrument measuring equivalent residual ink concentration, considered in INGEDE scoring, was not available. Dirt count analysis of deinked handsheets was performed by scanning them using an Epson Perfection V500 Photo scanner followed by processing of scanned images by Verity IA Color Image Analysis software. Overall, it was found that two of the three experimental fatty acids (free fatty acid from everyday pure soy oil and the one from high oleic soy oil) performed better than the standard, using oleic acid. It was also found that these free fatty acids had lower acid number than the standard oleic acid, which could improve the deinking performance.

Keywords: deinking, offset litho printing, recycling, acid number, deinkability factor

JPMTR 071 | 1506 Original scientific paper
DOI 10.14622/JPMTR-1506
UDC 582.736 – 0277.33 : 763

Received: 2015-07-29
Accepted: 2015-11-19

Self-supported printed multi-layer capacitors

Michael James Joyce, Ali Eshkeiti, Paul D. Fleming III, Alexandra Pekarovicova and Massood Zandi Atashbar
Western Michigan University, Center for the Advancement of Printed Electronics (CAPE), 4601 Campus Drive, Room A217, Kalamazoo MI, 49008


The increasing demand for miniaturized electronic devices has elevated the need for rechargeable micro-power sources. While lithium and lithium ion batteries have been utilized in these applications since the late 1990s, other energy harvesting technologies, such as mechanical, thermal and solar, are now being used to augment batteries to enable systems to be self-powered. However, the lifetime of any battery is finite, which may be a major problem when the application is in a permanent structure or medical implant device. For power or significant energy storage applications, printed multilayer capacitors or supercapacitors are being explored as an enhancement, or replacement of micro-batteries.

The printing of multilayer capacitors offers an inexpensive manufacturing process for these devices. Though the ability to print supercapacitor electrodes, supercapacitors, and batteries on rigid and flexible substrates is well known, having a device supported by a substrate is not always advantageous. This is especially true for cases where the rigidity of the substrate limits the extent to which the device can be bent or wound, or where substrate compatibility issues to the surface to which it is to be attached is faced. The ability to bend or wind devices can improve the attachment to surfaces; enable its placement in confined spaces and advance efforts to further miniaturize devices. In this research, a sacrificial water-soluble polymer layer was used to produce self-supported (substrate free) printed conductive and dielectric ink films of different thicknesses, as well as a completed capacitor. The electrical and mechanical properties of these films and the capacitor were measured. Such measurements have not yet been reported and should therefore advance our understanding of properties at different thicknesses.

Keywords: supercapacitor, printed electronics, screen printing, alginate, silver electrode

JPMTR 072 | 1435 Research paper
DOI 10.14622/JPMTR-1435
UDC 655.1 – 024.25 : 621.38

Received: 2014-09-01
Accepted: 2015-09-24