Inkjet ink spreading, absorption and adhesion on substrates coated with thin layers of cationic polyelectrolytes

The effect of a thin layer of cationic polyelectrolyte coating on ink spreading, absorption and adhesion on a paper substrate has been studied. Four different cationic polyelectrolytes with different chemistries and physical properties were coated onto an 80 g/m² wood free paper. The samples were printed on two desktop printers using a water-based ink with dye and pigment colorants, respectively. An improvement in print quality was observed with increasing amount of cationic polymer, especially with the pigmented ink. Surprising effects concerning the dye ink print density were seen on coating containing certain cationic polymers. The print mottle and ink bleeding behavior indicate that the cationic charge density of the polymer alone cannot explain the colorant fixation efficiency. The colorant- capturing mechanism is a complex mechanism where the accessibility and activation of the cationic sites must also be considered. This was confirmed when the coat weight dependence was analysed.