Advancements in ultraviolet (UV) curing technology—the process of transforming a liquid into a solid by using UV light—are responsible for some of the recent changes in the printing industry.
As an energy-efficient and green technology, printers everywhere have rapidly adopted UV energy curing inks and coatings to print on a variety of substrates, including metal, wood, fabric, plastics and a range of paper grades.
In the web printing arena, UV curing is now one option for the production of high-quality printing, at high speeds. This effectively closes the gaps that previously existed between coldset and heatset printing, in terms of sheetfed versus web speeds, and low productivity versus high-volume production.
UV ink technology has been around for more than 20 years, but until now it has not been an alternative production method for coldset printers. However, newly developed, more sophisticated UV-curable ink technologies are changing the landscape of the traditional coldset web printing operation.
UV-curable inks and varnishes typically consist of four main components: monomers, oligomers, pigments and photoinitiators. The photoinitiators are the catalysts that react to UV light of a certain wavelength, triggering a chain reaction that takes low molecular weight material (monomers and oligomers) and makes larger, high molecular weight polymers. These polymers then become so large by means of crosslinking that they form a continuous solid, or dry film.
Staying Above Surface
The drying of a conventional coldset ink film occurs when the ink vehicle (solvent, oil) is absorbed into the substrate, leaving behind the solids (pigments and resins) to form a film on the substrate surface. In energy curing, on the other hand, virtually all of the components in the ink or coating remain on the surface of the substrate.
Where does the true difference between UV and conventional ink lie? The difference is in the chemistry of the materials in the inks, and in the pressroom equipment needed to initiate the curing process. The materials, when formulated correctly, have made some newer energy curable ink formulas more user-friendly than ever before, making energy curable inks more common today and anticipated to be a growing segment in the years to come.