Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Impact of non-uniform water absorption on water-interference print mottle in offset printing
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). RISE Bioeconomy.
RISE Bioeconomy.
OmyaInternationalAG, Switzerland; Aalto University, Finland.
2018 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 1, p. 150-163Article in journal (Refereed) Published
Abstract [en]

Print mottle is a serious and yet common print defect in offset printing. An imbalance between the feed of fountain solution and the ability of the paper substrate to absorb and transport this water away from the surface can cause moisture/water interference problems. In the study presented here, we have investigated the uniformity of aqueous absorption and coating structure of pilot-coated papers with different types and dosages of dispersants and linked this to print mottle and uncovered areas (UCA). In earlier studies, the print quality of these papers indicated that a moderate addition of excess dispersant caused ink refusal, ink-lift-off (ink-surface adhesion failure) and water-interference mottle when printing at elevated fountain feed. In the present study, we have shown that a majority of the samples with uneven water/moisture absorption and an uneven burn-out reflectance tended to have more severe printing problems related to surface-moisture/water.An aqueous staining technique was used to characterise the absorption non-uniformities. This method has been developed previously with focus on absorption of flexographic water-based inks but can clearly give relevant information also for offset printing, when it comes to moisture/water interference mottle.

Place, publisher, year, edition, pages
De Gruyter Open, 2018. Vol. 33, no 1, p. 150-163
Keywords [en]
absorption non-uniformity, coated paper, dispersant, offset printing, uncovered area, water-interference mottle, Fountains, Moisture, Dispersants, Non-uniformities, UnCovered Areas, Water interference mottles, Water absorption
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
URN: urn:nbn:se:kau:diva-68066DOI: 10.1515/npprj-2018-3011ISI: 000450919200017Scopus ID: 2-s2.0-85047988264OAI: oai:DiVA.org:kau-68066DiVA, id: diva2:1223983
Available from: 2018-06-26 Created: 2018-06-26 Last updated: 2018-12-06Bibliographically approved
In thesis
1. Where did the ink go?: The effect of liquid absorption on ink distribution in flexography
Open this publication in new window or tab >>Where did the ink go?: The effect of liquid absorption on ink distribution in flexography
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The appearance of a print is affected by the individual ink layers. If the ink is unevenly distributed on the substrate it lowers the quality. This thesis puts focus on how the liquid absorbency of a coated substrate impacts on the ink distribution in flexographic printing. It is well known that a smooth surface increases the chances of a uniform print, whereas the influence from an uneven absorption is not established and has even been difficult to measure. If the ink is applied directly onto the substrate, or as an overprint onto already present ink layers, the outcome is even more complex. Ink trapping behaviour affects the uniformity of overprint layers. As of yet, this been largely overlooked in flexography.

The work includes several trials, from monochrome laboratory printing at 0.5 ms-1 to multicolour printing at 10 ms-1 in production-scale. These studies showed that ink absorption interacted directly with monochrome ink layers and that pore-structures with larger pores and greater liquid uptake generated more uniform prints. The tolerance of uneven pore-structure, and thereby absorption, varied between samples.

In multicolour printing, the overprint layer interacted directly with the preceding ink and indirectly with the absorbency (rate and uniformity) of the substrate. Overprint layers became thicker when the first ink layer was thinner and, consequently, turned uneven when the first layer was uneven. Moreover, the time between the applications of the two inks was important. When immobilisation of the first ink was too slow or uneven, it disturbed the ink trapping so that the overprint layer became uneven.

Output from this project offers a palette of tools to use when studying liquid absorption and its impact on print quality: a) experimental approach to separate the influence of uneven absorption from surface roughness, b) aqueous staining technique to characterise absorption non-uniformity, and c) technique to characterise ink trapping non-uniformity.

Abstract [en]

The appearance of a print is affected by the individual ink layers, and when the ink is unevenly distributed it will bring negative consequences. As an extension, print quality can affect how packaging is perceived and may even create ideas about the product inside the packaging. Therefore, it is important to understand the reasons behind poor and uneven print and to ensure that the board substrate provides a stable quality.

This thesis puts focus on how the absorbency of a coated substrate impacts the ink distribution in flexographic printing. Both monochrome and multicoloured areas are dealt with. To generate an understanding of these interactions, two new measurement techniques were developed where the non-uniformities in liquid absorption and ink trapping can be characterised. Surface roughness often has a strong influence on the print and this may hide interactions from ink absorbency. Therefore, the materials used here were carefully selected (or designed) to highlight the way liquid uptake affects the ink layers. Interactions between substrate and printing ink were studied in several ways, from monochrome printing at 0.5 ms-1 in laboratory-scale to multicolour printing at 10 ms-1 in production-scale.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2018. p. 96
Series
Karlstad University Studies, ISSN 1403-8099 ; 2018:52
Keywords
flexographic printing, print mottle, ink trapping, absorbency, absorption non-uniformity, water-interference mottle
National Category
Chemical Engineering Paper, Pulp and Fiber Technology
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-69984 (URN)978-91-7063-892-3 (ISBN)978-91-7063-987-6 (ISBN)
Public defence
2018-12-18, 21A 244, Ljungberg, Universitetsgatan 2, Karlstad, 10:15 (English)
Opponent
Supervisors
Funder
Knowledge Foundation, Dnr 20100268
Note

Samarbete med RISE AB

Available from: 2018-11-28 Created: 2018-10-30 Last updated: 2018-11-28Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Authority records BETA

Thorman, Sofia

Search in DiVA

By author/editor
Thorman, Sofia
By organisation
Department of Engineering and Chemical Sciences (from 2013)
In the same journal
Nordic Pulp & Paper Research Journal
Chemical Engineering

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 12 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf