When using a UV flatbed printer to print some materials, because of the instantaneous drying of the UV ink, it sometimes leads to the problem of low adhesion of the UV ink to the substrate. This article is to study how to improve the adhesion of UV ink to the substrate.
corona treatment
The author found that corona treatment is a method that can effectively improve the adhesion of UV ink! The positive and negative electrodes of the corona device are grounded to the ground plane and the Yuden air nozzle respectively. The free electrons with high energy are accelerated to the positive electrode, which can change the polarity of the non-absorbent material and increase the surface roughness, enhance the ability to combine with the ink, achieve the correct UV ink adhesion, and improve the adhesion fastness of the ink layer. .
Corona-treated materials have poor surface tension stability, and the corona effect will gradually weaken over time. Especially in a high humidity environment, the corona effect will weaken faster. If corona treated substrates are used, cooperation with the supplier must be made to ensure the freshness of the substrates. Common corona treated materials include PE, PP, nylon, PVC, PET, etc.
UV ink adhesion promoter (AdhesionPromoters)
In many cases, cleaning the substrate with alcohol will improve the adhesion of the UV ink to the substrate. If the adhesion of the substrate to the UV ink is very poor, or the product has high requirements for the adhesion of the UV ink, you can consider using a primer/UV ink adhesion promoter that promotes the adhesion of the UV ink.
After the primer is applied on the non-absorbent substrate, the adhesion of the UV ink can be improved to achieve the ideal adhesion effect. Different from corona treatment, the material of chemical primer does not contain non-polar oily molecules, which can effectively eliminate the problem of unstable corona effect caused by the migration of such molecules. However, the scope of application of the primer is selective, and it is more effective for glass, ceramic, metal, acrylic, PET and other substrates.
UV ink curing degree
In general, we can observe poor adhesion of UV inks on non-absorbing substrates in cases where the UV inks are not fully cured. To improve the curing degree of UV ink, you can start from the following aspects:
1) Increase the power of the UV light curing lamp.
2) Reduce the printing speed.
3) Extend the curing time.
4) Check whether the UV lamp and its accessories are working properly.
5) Reduce the thickness of the ink layer.
Other methods
Heating: In the screen printing industry, it is recommended to heat the substrate before UV curing before printing on difficult-to-adhere substrates. The adhesion of UV inks to substrates can be enhanced after heating with near-infrared or far-infrared light for 15-90 seconds.
Varnish: If the UV ink still has problems adhering to the substrate after using the above suggestions, a protective varnish can be applied to the surface of the print.
Post time: Jun-09-2022