Optimizing ink and substrate with surface science
Ink-jet as a digitally controlled process with a large variety of possible combinations of ink-types and print carriers is a very flexible and versatile tool. The quality highly depends on the droplet formation at the print head nozzle, the drop spreading on the substrate, and the wetting behavior of the substrate. Evaluating the static and dynamic surface tension of the ink as well as surface properties of the material is the domain of our instruments.
Common applications of inkjet printing
- Office printer
- Industrial printing
- Printing on packaging
- Printing large-scale OLED displays
Drop formation and spreading is largely controlled by the surface tension of the ink, which is commonly lowered with surfactants. Our tensiometers help to adjust the surfactant concentration by measuring the static surface tension. The critical micelle formation concentration (CMC) as an indicator for the surfactant’s efficiency is measured automatically using a wide concentration range.
To optimize ink in terms of wetting means to regulate the speed with which the surfactant lowers the surface tension. During ink ejection, the surface tension needs to be large enough to ensure meniscus recovery inside the nozzle, and thereby, guarantee a proper drop formation. However, after a very short flight time, the surface tension needs to be low enough to assure proper wetting of the substrate. Our bubble pressure tensiometers monitor the dynamic behavior of the surface tension in a wide range of speed.
The surface energy of the substrate defines the wettability and partly controls the adhesion between ink and substrates such as paper or plastics. Our Drop Shape Analyzers determine the surface free energy and its division into polar and disperse parts. This energy profile serves to optimize surface preparation steps like plasma or corona treatment.
As ink-jet printing drops of approximately 100 pL are ejected onto a substrate, our picoliter dosing unit, microscope optics, and high speed camera characterize this wetting process very closely to true environmental conditions.
Wherever there are surfactants involved in dynamic processes, foam formation can become a challenge to solve. Our Dynamic Foam Analyzer – DFA100 offers highly reproducible methods for measuring foam formation in the short-term range of unstable foams. This makes it a powerful tool for optimizing antifoam agents added to the ink.
AR269: Investigating the foam-inhibiting effect of antifoaming agents in printing lacquers
To avoid the numerous quality problems due to foam, antifoaming agents are added to aqueous printing inks and lacquers. The efficiency of two silicone-based antifoaming agents is investigated and compared using foam height measurements with respect to time.
AR267: Foam behavior and foam stability of aqueous surfactant solutions
The foaming and stability behavior of three surfactant low-foaming solutions are characterized. Comparative interfacial rheology measurements provide a good correlation between interfacial rheology parameters and the data from the foam measurements.
AR256: How plastics lose their hydrophobia
The increase in surface polarity by ozone treatment is proven with the help of contact angle measurement. The results also show the dependency of the degree of surface activation on the duration of the treatment.
AR221: Wettabilities and Surface Tension of Different Paper Types
Rapid change of contact angle describes the absorption into porous paper, the capillarity of which is measured in addition with the Washburn method. For coated paper, different hydrophilic behavior is detected via surface energy determination.