Flexible Films & Cardboards 

An ultimate challenge

Digital printing on flexible films with waterborne inks is widely demanded in applications that are still in transition from conventional to digital printing such as luxury vinyl tiles (LVT) or flexible packaging. Compared to solvent or UV inks are sustainable solution due to the low VOC formulations and absence of toxic photo-initiators.

Re-soluble Digital Binders: ESAJET

Water-based inks printing on flexible films is a complex process because there is a risk to unbalance the fragile equilibrium that links sprint reliability with ink drying properties and performance of the printed material.
Unlike printing on porous materials, printing on a non-porous substrate requires the ink to dry faster than usual to deliver a good print quality. This means reducing the amount of humectants, in particular glycols with high boiling point, which, in turn, contributes to faster evaporation of water inside the nozzles.
On the other hand, the printed film is an intermediate product, which needs to show a good adhesion, lamination or scratch resistance. This means using binders delivering high application performance, which are generally good film-formers and put the printhead integrity even more at risk when the ink contains a minimal amount of humectant.
In order to restore this equilibrium, we have developed the ESAJET “digital” binders range, based on polyurethane and acrylic dispersions. They provide an outstanding lamination strength while offering a good ink re-solubility in presence of low humectant levels, assuring safety for the printheads.

Transparent and moisture resistant receptive coatings: ESACOTE^® PU

The absence of porosity of the flexible films impedes to remove water and glycols of the inkjet ink by absorption. Relatively large amounts of low viscosity ink stand in liquid form on the surface of the substrate before an auxiliary drying device speeds up the evaporation process. During that time interval, the ink is prone to “move” laterally creating printing defects like bleeding, mottling and craters. 

To prevent the degradation of the print definition when the ink is still “wet”, we can prime the film with hydrophilic swelling materials, like CMC or silica gel, that will quickly remove water from the incoming ink droplets and deliver a good print definition. However, that generates a translucent or opaque printable layer, which is often detrimental to the further use of the printed film. For example, reverse printing for food packaging will not cast the expected shine, or the lamination strength of a printed film will be insufficient. Therefore this process is limited in some graphic applications and not fit for industrial film applications.

To overcome this issue, we have developed a dedicated range of binders for the formulation of digital primers, that helps to maintain the print definition without losing the film transparency, lamination performance and moisture fastness required in certain food packaging applications.