WATER-BORNE AND SOLVENT-BASED FLEXOGRAPHIC INKS-INFLUENCE ON UNCOVERED AREA AND INK LEVELING ON PE-COATED PAPERBOARD

摘要

A smooth and a rough PE-extrusion-coated paperboard, with and without corona treatment, were printed flexographically using a solvent-based and a water-borne ink with the objective to examine the influence of surface roughness and wetting of the paperboard on ink transfer, uncovered area (UCA), ink-film thickness distribution, ink leveling, and print unevenness. The results showed that ink transfer was significantly lower for the solvent-based ink, but because this ink has a stronger pigment, less ink was needed for a given ink density. Both inks were equally prone to yield UCAs, and both inks also formed dry ink layers with the same thickness distribution in the 2-4 mm range. Both inks also leveled out to same extent. The leveling was controlled by the corona treatment and reduced the UCAs. The smooth substrate exhibited the least UCAs. On a submillimeter level the print unevenness for the water-borne ink exhibited patterns that resemble crawling worms or curled thread ends aligned in the direction of the printing. The pattern for the solvent-based ink was grainy and without orientation. These patterns are suggested to reflect the splitting pattern of the ink during the transfer to the paperboard.