Correlations between water-based inks and the inkjet process

The digital inkjet printing process is gradually changing the printing industry by bringing new features (personalization, electronics, etc.) and by producing printed volumes previously manufactured by conventional printing techniques (textile, packaging, flooring, etc.). This process is based on the ejection of pico-volumetric drops on demand by activation of a piezoelectric element. The control of the phenomena involved in the interactions between the liquid-process-substrate is complex and requires in-depth understanding.
This work contributes to the identification, characterization and understanding of the material-process correlations underlying print quality. The scope of the study focuses specifically on printing of aqueous pigmented inks on polymer substrate for flooring industry.

A first axis focus on the colloidal stability assessment of the suspensions as well as the optimization of their rheological and physicochemical properties. The impact of the dispersing agent molecular weight ensuring the colloidal stability is especially studied.

A second axis is devoted to the study of the impact of process parameters and ink formulation on droplet generation. First, the design of the waveform, identified as a critical parameter in the ejection process, is discussed. The origin and characterization of the latency phenomenon, generating printing defects frequently observed in industrial environments, is investigated. This approach leads to the integration of dynamic physicochemical parameters in the jettability assessment.

In the final part of this work, the interactions between the ink and the substrate, in the context specified by the industrial application of this project, are studied. Print quality after drying and adhesion are assessed.

This thesis work therefore contributes significantly to the advancement of the scientific and technological understanding inherent to the inkjet printing process and promotes its industrial integration.