The Interaction between Water and Liner and Newsprint in Flexographic CI-Printing Press

摘要

Printing with water-borne ink in a multicolor printing press subjects the substrate to water, because the water-borne ink contains water. The water in the ink can influence the surface properties, e.g. the roughness and compressibility, and can lead to dimensional changes. On the other hand, water derived from the ink can enhance or reduce some aspects of the final print quality depending on the properties of the substrate. In the present study, the manner in which the print quality of unsized paper substrates was influenced by pre-treatment with water and surfactant solution in flexographic printing was investigated. The experiment was designed to imitate the effects of multicolor printing using water-borne ink, since the water derived from the ink in an early printing unit influences the mechanical, dimensional and wettability properties of the paper and can thus influence the print quality in a later printing unit. This paper complements a previous paper, which showed a reduction of print mottle on a white top liner (with a low water absorptivity and wettability) when water and surfactant solution were applied just before the ink. The substrates investigated in the present paper were standard newsprint and a white top testliner, with high water absorptivity and wettability. The printing trials were performed in a central impression flexographic printing press using two of the six printing units. The first unit was used to apply water and a mixture of water and a surfactant and a second unit was used to transfer water-borne ink. The effects of water and surfactant pre-treatment were evaluated by measuring the print quality and the substrate properties. The pre-treatment by water and surfactant solution showed no effect on print mottle in the case of newsprint or testliner.