Influence of plasma activation on absorption of offset ink components into pigment-coated paper

The influence of plasma activation on offset printability was investigated. Pigment-coated paper was subjected to industrial corona treatment and experimental pilot scale argon plasma. Surface characterization was made by contact angle measurements and X-ray Photoelectron Spectroscopy (XPS). Five different model inks with different portions of linseed and mineral oils, and one commercial ink were used in ink setting evaluation with Ink Surface Interaction Tester (ISIT) and laboratory scale printing. In addition, samples were printed in a pilot scale sheet-fed printing press using the same commercial ink as in laboratory scale. According to the results, plasma activation increased surface wettability and polarity due to oxidation. Plasma treatment had a clear impact on ink setting, but the response depended on the ink composition. The ink setting rate decreased with linseed-oil-dominated inks, probably due to increased acid-base interactions between the ink oil and polar plasma treated coating. With mineral oils ink setting accelerated. Pilot scale plasma treatments did not have an impact on print quality. When compared to the industrial corona treatment, the pilot scale argon plasma treatment produced higher hydrophilicity. The impact on ink setting was also higher, even if the used power for the argon plasma was only approximately half of the corona's.