How to achieve UV curing in offset printing

The main difference between UV curing and drying of traditional inks is the composition and drying mechanism they are attached to. Conventional oil-based inks depend on the absorbency of the liquid material into the printing material. After the liquid penetrates, the ink cures. The resin material in the ink is dried by oxidative polymerization to produce a scratch-resistant surface. This process can take several hours, depending on many variables such as substrate materials, ink coverage, ink and water chemistry, and ink balance. The auxiliary volatilization (infrared and hot air heating) can accelerate the drying speed of the waterborne varnish.

The UV curing process uses a promotional page printing ink containing a photoinitiator. The photoinitiator can be excited by ultraviolet light of a specific wavelength width and a specific intensity. After printing, the substrate is exposed to ultraviolet light (a lamp mounted on the press), which initiates a chemical reaction of the photoinitiator and other UV-reactive components, almost instantaneously curing (drying) the ink layer.

Under the co-catalysis of UV and photoinitiators, the ink binder reacts immediately to produce a dry ink ink film (UV ink binders include polymerizable monomers, oligomers, and prepolymers).

Sheetfed UV inks and gloss systems are based on acrylic resins and are usually used in 4 ways:

• Traditional Ink + Dispersion Primer + UV Polishing

• Classic UV ink and UV Varnish

• Non-classic UV (hybrid) inks and UV varnish

• Combination of UV inks and conventional ink systems and varnish on the same press for rotation.