How would you describe “offset printing with UV drying”?
The ink is not dried through oxidative absorption, but through UV light. With this method, the printed sheet dries instantly allowing for further processing immediately off-press. Particularly in the case of uncoated papers, the ink is absorbed to a lesser degree by the paper and does not “flood it”, to use a colloquial expression, but dries immediately on the surface of the paper.
What is special about this method?
This form of offset printing provides new opportunities, particularly for natural papers, because the ink dries on the spot. And whilst the drying process in conventional offset printing can frequently lead to colour changes in uncoated papers, with UV curing this is not the situation.
What are the origins of offset printing with UV drying?
This offset printing method has its origins in the world of foil (or film) printing. Stickers as well as hard and soft PVC can only be printed with UV ink because conventional ink cannot dry on non-absorbent materials.
A further development of the printing method is Low-Energy UV offset printing (LE-UV). The ink is exposed to a smaller light spectrum. This approach reduces the consumption of energy and has become very popular since it was first introduced. This process is particularly attractive to medium to large print runs on natural papers as the production process can be completed more quickly.
How does the technique work?
UV ink consists of 70 percent monomers/oligomers, 15 percent pigments, 12 percent photoinitiators and 3 percent additives/stabilizers. If the ink is exposed to UV light radiation, polymerization begins a chain reaction that leads to the curing of the UV ink.
What can be achieved with this method and where are the limits?
Actually, there are no real limits. Everything that runs through a printer can be printed. However, only UV inks can be used. Special colours like gold and silver as well as fluorescent inks are available.
Why is offset with UV drying particularly interesting for uncoated papers?
As previously mentioned, traditional sheet-feed offset printing can be problematic with uncoated (so-called natural) papers because the ink dries very slowly. For this reason, the paper is often sprayed extensively, but there are still waiting times between 48 and 72 hours until the paper can be processed further. None of this is an issue with UV offset printing. The ink is applied to the paper and is cured immediately by the UV light. No spray is necessary and the project can be processed further without delay.
Another advantage of this method is the brilliance of the print results. Because the colour enters the substratum only minimally, it achieves a print result that is much higher in contrast and colour intensity than conventional sheet-feed offset printing. The printed object also very much reminds us of the HP Indigo technology and enables the user to create hybrid print products.
However, we would like to mention one disadvantage of the UV technology: Due to the higher price of the printing machines and the ink, it is slightly more expensive than traditional offset printing. If you want to achieve large print runs where the price also matters, traditional offset printing still takes the pole position.