Evaluation of plasma-deposited hydrophobic coatings on pigment-coated paper for reduced dampening water absorption

Hydrophobic plasma coatings were deposited on pigment-coated paper with the purpose of reducing dampening water absorption and create uniform surface chemistry. The influence of plasma coatings on sheet-fed offset printability was also studied. Three plasma chemistries, fluorocarbon, organosilicon and hydrocarbon, were used to adjust the hydrophobicity of paper surface. The plasma coatings reduced, and in some cases prevented, the dampening water absorption into pigment-coated paper in both laboratory and pilot scale trials. Ink transfer, mottle and ink setting were altered due to the presence of the plasma coatings, whereas porosity and surface strength of the pigment-coated papers were not affected. These results suggest that the preferred way to improve the print quality with both mineral and linseed oil-based inks is to use plasma chemistry that modifies the paper surface to be both hydrophobic and oleophilic. Hydrophobic and oleophobic surfaces were found to cause ink repellence. Uniformity of the plasma coatings was crucial for obtaining an even print appearance.