Application of cationic UV ink Upper half

Cationic UV ink is a special ink, and its curing mechanism and curing process are different from those of traditional solvent-based inks, water-based inks, and free radical UV inks. Its main feature is the use of photosensitive cationic initiators, and the use of various highly active groups such as epoxy and vinyl ether on the skeleton of the resin and monomer. This cationic initiator is insensitive to oxygen and is not easy to quench. Once it is triggered under light, it will quickly trigger a chain reaction of the active groups on the monomer and resin, and continue until all the active groups are completely reacted. The chain reaction will not stop. The ink film formed in this way has very few residual unreacted monomers and resins, and there is no migration, so it is very safe. At the same time, due to the high conversion rate, the ink film is very wear-resistant, scratch-resistant, solvent-resistant, and has excellent physical properties.

Cationic UV inks cure very quickly and have high production efficiency. Under high-power density UV light radiation, 80% of the cross-linking reaction can be achieved within milliseconds. They can be safely rolled up and down on gravure, flexographic or roll-to-roll digital printing machines without sticking or ink residue on the roller surface. Cationic UV inks do not contain volatile organic compounds (VOCs), so they are more environmentally friendly. In addition, cationic UV inks show particularly good adhesion when printed and coated on corona-treated substrates, which is also one of the key properties of cationic UV inks.

In addition, cationic UV inks have low volatility and low odor, and have a better operating environment and health and safety compared to traditional free radical UV inks. During the printing process, after the radiation-cured printed product comes off the press, the ink layer looks like it has been cured, but some monomers and resins have not reacted completely (that is, half-dry or not completely dry). In this case, the free radical UV ink will stop reacting and maintain this state for a long time, or slightly improve. However, cationic curing inks can continue to react even after leaving the UV light until the monomers and resins are completely cross-linked. This is the so-called post-curing, which is completely different from traditional free radical UV inks and is also the biggest advantage of cationic UV inks.

The main components of cationic UV ink

The main components of cationic UV ink are somewhat similar to traditional free radical UV ink, both of which contain oligomers (resins), reactive diluents (monomers), photoinitiators and various additives. Among them, oligomers are equivalent to the binders in ordinary inks and are film-forming materials. They mainly play a skeleton role in the performance of the ink. Structurally, there are photocuring groups on the skeleton of the oligomer, which are photosensitivity and can participate in photocuring reactions. Reactive diluents can not only dilute the ink, making the ink have good printing adaptability, but also participate in the reaction, making the ink have better physical and chemical properties. The photoinitiator is equivalent to the catalyst in ordinary ink. It can produce free radicals or cations by absorbing ultraviolet rays, thereby initiating polymerization and physical cross-linking reactions between oligomers and reactive diluents to form a network structure ink layer.