Studying the impact of non-uniform absorption on print mottle of coated boards with barrier patterns

• 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.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Kemiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Chemical Engineering (hsv//eng)

Nyckelord

Liquid absorption

absorption non-uniformity

print mottle

flexography

coated packaging board

Chemical Engineering

Kemiteknik

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vet (ämneskategori)

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