Quite often, ink performance in industrial inkjet print production is improved by using primer and/or varnish. But should you opt for a fully digital process, jetting all fluids in one go, or for a hybrid process that combines inkjet printing with an analog coating or printing technology?
The key benefits of inkjet printing are known: the absence of a print master, the ability to produce variable print runs with the first print being of good quality, fast changeover between jobs, and minimal waste. Yet the economic viability of incorporating inkjet printing into an industrial product manufacturing process depends on how well the inkjet printing complies with the processes before and after printing. If it fits in smoothly, only the printing system requires investment, as the other processes can be carried out using the existing installations.
Ink performance can often be enhanced by using primer and/or varnish, although in some specific cases, a surface pre-treatment (usually corona, plasma, or flame) may be sufficient. Such a primer and/or varnish can be applied either in a fully digital or in a hybrid workflow. The former jets all fluids simultaneously, whereas the latter combines inkjet to print the image with an analog printing or coating process to apply the primer and/or varnish.
Both fully digital printing and hybrid printing can offer advantages in UV as well as water-based inkjet printing.
An example of hybrid printing in the case of UV inkjet printing is enhanced lightfastness of the printed image by applying a coating on top of the jetted image. The outdoor lightfastness of UV inks, which contain organic pigments, is generally 2 to 3 years. However, applying a coating that includes anti-fading agents can extend the lightfastness up to 4 to 5 times, allowing for up to 10 years of outdoor durability.
Another example of hybrid printing in the case of water-based inkjet: Printing on décor paper using water-based inkjet can benefit from a primer coating, as it enhances the color strength by limiting ink penetration into the highly porous paper while reducing ink consumption by up to 20%. The primer also helps to control dot growth of the ink droplets, limiting ink bleeding.
Product printing using UV LED inkjet technology is a prime example of where a fully digital process is best suited. In that case, adhesion on a wide range of substrates using a single ink set can be achieved through the in-line jetting of a very thin layer of UV LED-curable primer. The primer’s chemistry is perfectly matched to that of the ink, enabling printing on multiple materials, such as metal and plastics, without the need for an ink swap.
Jetting all functional fluids in one go can be very successful when they are matched to each other. This approach is particularly advantageous when the printed area of the product is small, which is usually referred to as low print coverage of the surface.
For full-surface printing applications, hybrid printing can be a more cost-effective option. Using coating or analog printing to apply a primer and/or varnish with proven performance has a positive impact on the cost price, as the formulations do not require low viscosity or compatibility with the inkjet printheads. However, the challenge is to ensure that the jetted ink functions effectively in combination with the analog primer and/or varnish.
A specific application where utilizing a primer has a significant impact, is the printing of cardboard packaging, both folding and corrugated, using water-based inks.
Agfa can be your consumables partner because we develop the chemistry for both fully digital and hybrid printing primers in-house. The crucial aspect in the case of a hybrid approach is to ensure that the ink and primer formulations are compatible to control ink bleed and attain homogenous print quality, which is key in carton printing. Matching these formulations is vital in achieving consistent printing outcomes, encompassing both image quality and physical properties of the prints.
