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A discussion on the curing speed, flexibility and adhesion of UV ink

Time: 2018-03-27


When design UV offset ink formula, it is necessary to start with the principle of UV ink curing, which is based on the characteristics of the bearing material and the special requirements in the application. UV offset ink Co often meet some confusion when they use UV resin UVP30. Same batch will have a deviation in the flexibility and adhesion of the ink layer after adjusting the curing speed. Holywill’s engineer study and found industry found that the faster the ink solidified, the worse the surface activity after the curing. The photoinitiator molecules in the ink, irradiated by UV light, begin to react and connect to form a molecular chain until all the molecules are linked. If a high active photoinitiator is used, molecules will form links around the fast phase. This is a fast drying type of ink. Once cured, the ink surface is not too active. But if a low activity photoinitiator is used, because of the lack of active bonds, molecules are easy to form long chains. The ink will dry slowly, but the ductility and toughness of the ink will be much stronger.

The chemical raw material used in the ink can not react with the surface of the substrate, otherwise it will cause cracking or delamination and so on. Under this condition, we usually need to solidify the slower ink. UV ink, designed for production cards or hard plastic panels, is not flexible or flexible, as long as it is suitable for material surface characteristics. Usually, these products can be designed to be fast drying. However, the curing rate is too fast, which will increase the shrinkage rate during the curing process and make the ink layer move relative to the substrate, resulting in the poor adhesion and the drop of peel strength. The faster the UV ink is dry, the surface adhesion is relatively poor, and the flexibility and ductility will also decrease. The following ink overprint varnish and adhesion, will have a certain impact. The use of fast drying ink is not necessarily good, the use of slow drying ink is not necessarily bad, the important thing is to be able to determine according to the material and subsequent processing.

What we are more worried about is that when using slow dry ink, it uses excessive UV energy to irradiate, not only affects the adhesion of the ink, but also reduces the ink's ductility. While the use of fast drying type ink, but the lack of UV energy resulting in poor curing, resulting in more adhesion.

We need to know the characteristics of UV ink clearly, and we should know how to control the drying and curing state of the ink.