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Primer inks in which a divalent salt is the main active ingredient play a critical role in inkjet printing by governing the penetration, lateral spreading, and interaction of subsequently deposited color inks with the coated paper substrate. These mechanisms directly influence image sharpness, color fidelity, and drying behavior, thus overall print quality [1]. However, interpreting interactions between primer and ink-coated paper is experimentally challenging due to the thin, optically opaque nature of paper and the sub-second timescales of liquid uptake. To address this challenge, we use Ultrafast Nuclear Magnetic Resonance imaging (UFI-NMR) [2], which offers a real-time, non-invasive monitoring of liquid penetration with micrometer spatial and sub-millisecond temporal resolution.
To understand how the chemistry of primer ink influences transport in porous coating and base paper, we examine imbibition and swelling using aqueous solutions containing different concentrations and types of divalent salts. UFI-NMR allows us to use the same real-time signal variations in pore-scale saturation to determine both the position of the advancing liquid front and the swelling of the base paper subsequently. The imbibition dynamics of primer ink exhibit an inverse dependence on viscosity, consistent with Washburn-type capillary flow in a rigid porous medium. Swelling, however, does not exhibit the same viscosity-controlled scaling, indicating contributions beyond purely hydrodynamic effects. The swelling rate increases with increasing salt concentration. This concentration dependence is strongly ion-specific, with each divalent salt producing a distinct swelling behavior. We attribute these differences to chemical interactions between the dissolved divalent ions and the chemistry of the coating layer of paper.
| References | [1] Krainer, S., Saes, L. and Hirn, U. (2020) ‘Predicting inkjet dot spreading and print through from liquid penetration- and picoliter contact angle measurement’, Nordic Pulp & Paper Research Journal, 35(1), pp. 124–136. https://doi.org/10.1515/NPPRJ-2019-0088 [2]Nicasy, R.J.K., Huinink, H.P., Erich, S.J.F., Adan, O.C.G. and Tomozeiu, N. (2023) ‘Ultra Fast Imaging NMR method for measuring fast transport processes in thin porous media’, Magnetic Resonance Imaging, 103, pp. 61–74. https://doi.org/10.1016/j.mri.2023.06.009 |
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| Country | The Netherlands |
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