Validation of Ink Media Interaction Mechanisms for Dye and Pigment-based Aqueous and Solvent Inks

In this article, the dynamics of droplet impingement, spreading, absorption, penetration, and evaporation are discussed for different ink jet ink classes. Both dye and pigment based aqueous inks are included, as well as solvent or eco-solvent inks. The fundamental physicochemical rules determining the dynamics can be very dependent from ink to ink, and are compared. After impact there is a fast spreading phase that takes into account the evolution of the kinetic energy of the droplet to forced spreading on the receiver. Later on, diffusion or capillary wicking is possible, and is depending upon the nature of the substrate. The speed of these processes can be influenced by the presence of dyes or pigments in the inks. After absorption / penetration, the carrier liquid can evaporate leading to the final equilibrium condition. For (eco)-solvent inks the evaporation is much more important compared to the other penetration/absorption processes, so that it cannot be easily separated into different independent time scales. In situ visualization of the dynamics for real size ink jet droplets is not easy, especially for the droplets of only a few pl volume. Comparison of large droplet impact dynamic studies with theory and extrapolation of the behavior to small droplet cases has some risks., Test experiments have been setup in order to simulate transient absorption phases on different receivers. Traditional microscopic evaluations have been done in order to verify whether the proposed models for describing the transient behavior are in agreement with the experimental observations for real small sized droplets.