Classic printing processes, such as offset printing, in which the printed image is applied by means of a printing plate or printing block, are increasingly being replaced by digital printing processes. Thereby the desired information is applied directly from the computer to the respective material. While digital printing was previously mainly used for smaller quantities due to its short changeover times, more and more companies are now also using this process for large print runs. One of the reasons is the greater flexibility, which also enables individualized prints. In addition, digital printing can be used to produce large area prints with web widths of up to 2 meters at high printing speeds of up to 50 meters per minute with a resolution of 1200 dpi.

However, printing speed and precision, even on large areas, place special demands on printing inks, because the physical parameters of the inks must be individually adapted to the architecture and functioning of the printheads. On the one hand, customer-specific color brilliance, abrasion and UV resistance as well as environmental compatibility must be guaranteed; on the other hand, manufacturers of printers and printheads must be able to rely on new inks for industrial printing working perfectly.

In their joint research project "InDiPrint", Fraunhofer IMWS and PIT GmbH not only developed custom-fit ink systems which can, for example, be used for printing on paper, textiles or plastics but also a universal evaluation system that accelerates the development of new inks designed for inkjet printing. "In the project, we focused specifically on the basic structure-property relationships of the new inks, in particular on the complex effects of printing ink composition and physical properties relevant to printing, such as viscosity, density and surface tension," says Dr. Sven Henning, scientist in the "Polymer-based Material Design" group at the Fraunhofer IMWS.

Thanks to the rapid evaluation of the relevant physical properties and processing behaviour of the inks, development times for new customized ink systems can thus be reduced while still in the development lab. Also, by studying the interaction between surfaces to be printed on, such as papers, textiles or polymers, and the ink systems specially developed for this purpose, researchers were able to improve quality and usage properties. Dr. Sven Henning, Head of the project, believes that the findings on structure formation processes gained in the project can also be transferred to polymer-based printing or digitally printed material systems for the development of novel biomedical materials.

The project was funded by Investitionsbank Sachsen-Anhalt as part of the ERDF program.