The role of binder type in determining inkjet print quality

There is an increasing trend for the use of aqueous-based inkjet inks in high-speed commercial printing and this challenges the hydrophilic and absorptive properties of the paper surface. The aim of this work is to clarify the role of polyvinyl alcohol (soluble polymer) and styrene acrylate latex (suspension polymer) as binder in the formation of the coating structure for the purpose of inkjet printing. The coating layer properties were studied in combination with a chosen speciality calcium carbonate pigment. The inkjet image quality was assessed on coated papers. The role of diffusion of colorant as well as vehicle absorption was studied using dye-based inks. Among the other traditional paper surface characterization methods, the surfaces were analyzed with the Clara device, which shows how the external pressure affects the inkjet ink penetration into the coated paper structure by measurement of capacitance changes during ink penetration through the paper. The method indicates that inkjet ink penetration depth and speed depends on binder type. The chemical nature of binders affects the ink movement. The polyvinyl alcohol concentrates within the fine pores of the structure and absorbs water in its polymer matrix, and is seen simultaneously to adsorb ink dye, whereas the styrene acrylate acts effectively as a hard sphere, affecting the packing structure of the coating forming a more permeable coating layer. Therefore, structural as well as chemical differences of coating layers determine the final inkjet print quality.