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- Thorman, Sofia, et al.
(författare)
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Simultaneous determination of absorption mottle and white-top mottle in the same area on coated boards
- 2013
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Ingår i: Proceedings of the 40th International Research Conference of iarigai. - Darmstadt, Germany : International Association of Research Organizations for the Information, Media and Graphic Arts Industrie (IARIGAI). - 9783981270440 ; , s. 225-232
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The proposed measurement technique offers a number of advantages compared to other absorption methods. It enables one to study liquid absorption in a time period that is relevant to printing. Moreover, with this technique one can quantify the contributions of white-top mottle and absorption mottle at the same location and in great detail. This makes this technique a useful tool for quality control of paper board products and for predicting print mottle of flexographic printing. The reproducibility and reliability of the technique were very promising, as suggested by the Round Robin tests.
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| 2. |
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| 3. |
- Thorman, Sofia, et al.
(författare)
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Studying the impact of non-uniform absorption on print mottle of coated boards with barrier patterns
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Absorption and surface roughness of a substrate are believed to impact flexographic print mottle. However, their respective contributions are not that well recognized as they always co-exist. In addition to average absorption rate, absorption uniformity is of higher importance and even more difficult to separate from surface roughness. Therefore we propose a method to independently study the effects of absorption non-uniformity on print quality. This is achieved by introducing artificial absorption non-uniformity with well-controlled barrier patterns. The barrier patterns are added onto coated boards by means of flexographic printing with appropriate chemicals. These patterns modify not only surface chemistry but also pore structure by closing the surface pores.This article provides proof of the concept, which has successfully been applied to seven coated liquid boards. For the first time, this technique enables one to create a property-matrix, absorption non-uniformity vs. e.g. surface roughness. From this matrix the impact from either of the properties on print mottle can be studied independently. Experimental investigations showed that the level of absorption non-uniformity in a coated board had clear impact on print mottle. In most cases the relationship appeared to be linear, though the degree of impact differed from one board to another. This suggests that the print was more sensitive to uneven absorbency on some samples. This may be contributed to relative importance of other properties including the original non-uniformity of the board surface. When absorption non-uniformity is at a constant and low level, the effects of surface roughness becomes more pronounced.
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| 4. |
- Thorman, Sofia, et al.
(författare)
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The impact of non-uniform ink absorptionon flexographic print mottle
- 2018
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Ingår i: Journal of Print and Media Technology Research. - Darmstadt, Germany : International Association of Research Organizations for the Information, Media and Graphic Arts Industrie (IARIGAI). - 2223-8905 .- 2414-6250. ; 7:1, s. 7-18
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Tidskriftsartikel (refereegranskat)abstract
- Absorption non-uniformity and surface roughness of coated packaging boards are believed to have an impact on flexographic print mottle. Yet, their respective contributions are not well recognised due to their co-existence. Therefore, we propose a method that can solely study the effects of absorption non-uniformity on print mottle. This is achieved by artificially introducing uneven absorption, through well-controlled barrier patterns. The barrier patterns were added onto board surfaces using flexographic printing. By applying barrier patterns of several area coverages on board substrates of different intrinsic surface roughness it is possible to create a property-matrix, absorption non-uniformity versus for example surface roughness. With this matrix, the impact on print mottle from either of the properties can be studied independently. The results showed that surface roughness had a dominant effect on the print mottle, but mainly when comparing samples that spanned a broad roughness range. On the other hand, within a limited range of surface roughness, uneven ink absorption governed print mottle instead. This may explain why printing problems are sometimes encountered despite smooth board surfaces. Although the impact of absorption non-uniformity on print mottle differed from one board to another, the results indicated that a change towards more uneven absorption will have a negative impact on the print quality for most of the coated boards. The results give a better understanding of flexographic print quality and thereby can enable more reliable print mottle predictions.
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| 5. |
- Thorman, Sofia, et al.
(författare)
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Uniformity of liquid absorption by coatings : Technique and impact of coating composition
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 456-465
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between a liquid and a paper surface is important for a number of paper treatment processes, where absorption is of special significance during printing. Many absorption measurement techniques use a large available volume of liquid to characterise absorption, when compared to the volume of the coating. The uniformity of the absorption is also seldom characterised. We have developed a new technique, which is presented in this article, to study the uniformity of absorption of a small amount of liquid. This technique is based on the short-time absorption (tenth of a second) of a coloured liquid, the blotting of excess liquid and a characterisation of the pattern of the stain. This method made it possible to detect differences among coating layers with different compositions. In many cases, the absorption non-uniformity could be linked to variations in the coating thickness and/or wettability. The thinner and thicker areas of the coating layers were interpreted as having different pore structures. Neither the coating thickness nor the wettability could provide a full explanation, which showed the need to develop a method to characterise absorption uniformity instead of only relying on measuring the total absorption potential.
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