Absorption Capability and Inkjet Ink Colorant Penetration into Binders Commonly Used in Pigmented Paper Coatings

The absorption of coating binders used in inkjet coatings plays an important role apart from that of the porosity and pore structure of the pigment coating layer. The aim of this work is to clarify how different binder films absorb water-based dye-containing inks and how changes in the ionic nature of both ink dye and binder films affect the ink absorption capability and the final colorant location in the binder film. The studied commercial binders were one carboxylated, and a range of partially hydrolyzed and fully hydrolyzed polyvinyl alcohol (PVOH), and these were compared to an anionic styrene acrylic latex. The hydrolysis modifies the effective crystallinity and hence the swelling tendency. The results show that as the hydrophobicity of the PVOH binder increases, the less the binder absorbs the water-based ink vehicle and the colorant of the ink locates/fixes more on the top part of the coating structure. Both ink vehicle and dye colorant diffuse into the binder film. It was observed that the carboxylated PVOH film produces the most intense coloration (darkest blue color of cyan ink) as the greater ink vehicle absorption promotes the high colorant amount in the film. The combination of opposite charges of the binder film and dye-based ink colorant fixes the colorant most effectively to the top part of the film by the action of chromatographic separation and adsorption.