Effects of atmospheric pressure plasma activation on inkjet print quality

This work concerns the suitability of atmospheric plasma activation for the modification of paper and polymer surfaces and its ability to improve inkjet print quality of conventional non-inkjet printing papers and polymer films. In this work pigment coated and surface sized papers, PE and PP films were modified using two kinds of atmospheric plasma equipment; one at the pilot scale and one at the laboratory scale. The pilot scale plasma activation was also compared to conventional corona treatment. The changes in the surface chemistry were measured using X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared spectrometry (FTIR-ATR). In addition, the surface energy was estimated by contact angle measurements. The topographical changes were measured using atomic force microscopy (AFM). The substrates were printed with different ink types with an inkjet printing system simulating industrial production and print quality and rub resistance were measured. Furthermore, the correlation between surface property changes and inkjet print quality are presented and discussed. The treatments oxidized the surface of the substrates increasing the base and the polar components of the surface energy. The conventional corona treatment gave higher surface energy and oxidation level than the nitrogen and helium plasma activations. The laboratory scale plasma activation was the most efficient one, because of the longest treatment time. Inkjet print quality of PE film clearly improved due to treatments. On the contrary, print quality of PP film worsened. Treatments for the paper substrates lead to relatively small changes.