Technological basics

The main difference between inkjet printing and other printing processes is that there is no printing form required for transferring the image to the material. The image is printed directly and contact-free onto the substrate. This is done using what is known as a “Computer-to-Print” process. Inkjet printing distinguishes between an image format in just one flow (single-pass systems) and an image format in several flows (multi-pass systems). With the single-pass system, the quality of the print is restricted by the resolution of the print heads, whereas the multi-pass system achieves greater print quality, however at the expense of productivity. In terms of technology, the inkjet process boasts the most compact tools for transferring information as a printed image to the substrate.

There are two different options when it comes to applying ink, which in turn also offer further possibilities. For the continuous inkjet process, a continuous flow of small ink drops is created. Depending on the image to be printed, they may also be electrically charged to some extent. Any drops not required are diverted and collected; the drops required continue on to the substrate. With the drop-on-demand process, an ink drop is only created once it is required for the image. There are two different options here: Either the ink drop is created by heating or locally evaporating a liquid in the nozzle chamber (thermal inkjet), or the drops are formed through the deformation of what is known as a piezoelectric crystal. This is attached to the nozzle chamber and is deformed by the electrical voltage. The drops are formed from the resulting excess pressure, catapulted out of the nozzle chamber and onto the substrate (piezo inkjet). With the development of this type of colour application, the advantages of UV technology have also been made accessible to the inkjet printing market. In contrast to thermal inkjet systems, piezo inkjet systems facilitate higher frequencies and a greater variety of colour formulations.

It is mainly low-viscosity (liquid) inks that are used for inkjet printing. Depending on the print head, this means a variety of layer thicknesses can be used when applying the ink, resulting in very high quality prints. The use of UV and LED inks for inkjet printing also has a number of further advantages which contribute towards increased output and process safety. Through the development of coordinated UV ink systems and suitable print heads, a superb result can be achieved with regard to ink resistance, resistance to fading, as well as chemical and mechanical stability, without any additional coating or lamination. UV and LED inks are 100 percent solid formulations. They do not contain any solvents and therefore cannot dry out. There are no unpleasant odours or health risks posed by the inks, and legally stipulated limit values are met. There is also less maintenance and cleaning work required at the printing press as UV and LED inks are only cured when in contact with UV light.