Ultraviolet Ink Technology from Theory to Practical Extension (2)

European perspective

This is mainly concerned with the evolution and direction of UV technology in the future. European ink formulators want to be able to add water to UV inks. Although the American ink formulator also showed a strong interest in this technology, it was the Europeans that turned it from an ideal to a reality.

There are several factors that are prominent in this development process. The most important is that the UV screen printing ink technology has a fast drying speed and a good gloss, which is an ideal alternative to many traditional printing technologies.

The biggest difficulty is the problem of ink curing height associated with high solid ink technology in the printing process. People should look for ways to solve this problem, especially during the printing of halftone images. If water or water-reducing resins and monomers are added, the percentage of solids in the ink and the final dot height on the print will be reduced without affecting the quality and curing.

Of course, water-reducing or water-based inks are not without their own problems. The stencil must be waterproof, and as the water evaporates, the screen will dry out. In addition, this kind of ink is not very good print. To get a good print quality, it must go through a complicated and tortuous exploration. However, if this process can be controlled with the improvement of ink technology, high-quality printing can be realized. In some cases, screen printing aqueous UV inks can also achieve offset printing quality.

It is not surprising that waterborne UV inks and technologies have not been accepted in the U.S. market. When this type of ink was first introduced to the market, many printers were in the phase of transitioning from solvent-based inks to ultraviolet-based inks, so they did not pay attention to the use of water-based inks. At that time, the number of four-color screen printing performed by printing companies in the United States was very small, which also caused people's neglect of water-based UV inks.

UV fast drying equipment

Along with the development of waterborne UV inks, there is a fast drying (flash drying) technology. The ink formulation on the continuous UV curing device is already mature. The scope and type of photo plates are designed specifically for the main rays of mercury lamps, and people can use them with confidence.

In this device, UV radiation is transmitted through the interface of the ink film and the substrate in the form of a narrow beam, allowing them to cure and adhere in depth. But the main problem with this device is the amount of heat it generates. This heat will cause the substrate to deform, but it will also promote the cross-linking curing reaction, which is more thorough curing. Although the key issues of the continuous UV device have not been solved, the improvement of UV lamp efficiency will reduce the heat generation and cost.

For fast-drying UV equipment, its requirements for functionality and formulation are completely different, and the photolithographic parameters are also different from the continuous curing process. Fast curing requires ink manufacturers have some expertise.

(to be continued)