UV inks have been around for some time, but they may bear serious consideration for at least some of your commercial printing work.
Background: UV Inks vs. Traditional Inks
UV inks are cured through exposure to ultraviolet light, in contrast to traditional printing inks, which dry through oxidation, evaporation, and/or absorption. More specifically, ultraviolet inks are “dual-state” inks. They are liquid until they are exposed to UV light, at which time they instantly harden.
Traditional custom printing inks contain pigments and vehicles, liquids in which the particles of pigment are suspended: oils, resins, and solvents. In sheet-fed offset work, when ink has been printed on a press sheet, the solvent penetrates the paper fibers (absorption), and the resin sits up on top of the surface and hardens as the chemical reaction with the atmosphere (oxidization) occurs, eventually leaving a film of dry ink.
In contrast, heatset web inks dry through evaporation. Exposure of the ink and paper to high intensity ovens followed by exposure to chill rollers first flash off the ink solvent and then set the ink on the paper substrate as the paper travels through the web offset press. (On coldset web presses, the ink solvent dries through absorption into the paper fibers.)
One Benefit of UV Ink: No Drying Time
The greatest benefit of UV inks is the speed at which drying occurs. Essentially the process happens instantly, as soon as the inks are exposed to UV light. Using traditional inks, a stack of press sheets must sit for up to 24 hours before the ink is dry enough to print the back of the sheet without marring the ink on the front, or before post-press operations can begin (such as folding, trimming, etc.). Using UV inks, subsequent press and post-press operations can occur immediately, significantly improving the speed and efficiency of the commercial printing run.
Another Benefit of UV Ink: Ability to Print on a Variety of Substrates
Traditional custom printing inks need to seep into the paper fibers to set. Because of this, they cannot be applied to non-porous surfaces such as plastics, or they will easily rub off. In contrast, the drying of UV inks (called polymerization) allows them to adhere to non-porous surfaces. The resulting dry ink is resistant to scuffing or marring.
More Benefits: No Solvents or VOCs
Traditional inks can contain up to 70 percent solvent. As these inks dry, the solvents evaporate (are given off as gases that enter the atmosphere), and these emissions are toxic (known as volatile organic compounds, or VOCs). Using UV-cured inks in commercial printing eliminates these VOCs and is therefore much more environmentally sound.
Still Another Benefit: Less Dot Gain
Since UV light cures UV ink immediately, the ink sits up on the surface of the paper (called “hold-out”) better than traditional inks. Traditional printing ink seeps into the paper, and the halftone dots spread and become “fringed” (this is known as dot gain). Dot gain can cause the ink colors to shift or make the ink seem muddy (or fuzzy) on the press sheet. In contrast, since UV inks cure immediately, it is possible to hold sharp halftone dots while applying thicker ink films, or in some cases it is possible to maintain brilliant colors while actually using less ink, since the ink sits up on the top of the press sheet.
Drawbacks of UV Ink
There aren’t many drawbacks, but there are some:
- UV printing requires separate inks, press blankets, and rollers from traditional offset work.
- UV printing is therefore more expensive than printing with traditional inks.
- Printing with UV inks requires you to find a commercial printing supplier with different/increased skills and experience.
Jobs You Might Consider for UV Ink
There are a number of instances in which you might want to consider UV inks for a custom printing project.
- Consider UV if you’re on a rush schedule, since the process eliminates almost all of the drying time.
- Consider UV if you’re printing on a non-porous surface.
- Consider UV if you’re printing on an uncoated sheet and you want a “crisp” look. This is an option when you want the subdued appearance and feel of an uncoated offset sheet, or textured sheet, but you want to avoid the subdued look of the ink that usually accompanies printing on an uncoated sheet. In most cases, traditional ink will seep into the paper fibers and become somewhat dulled. Printing UV inks on an uncoated sheet avoids this drawback, allowing the ink to still sit up on top of the substrate due to the immediacy of the drying process.
Talk with Your Printer Early
Not all custom printing vendors are set up to run UV inks, and even if they are, you may not like the cost. So involve your printer early in the discussion process if UV inks appeal to you for a particular commercial printing project.
This entry was posted
on Sunday, July 29th, 2012 at 2:34 pm and is filed under Offset Printing, Printing.
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