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Nitrogen UV Curing

(September 1999) posted on Wed Jan 05, 2000

Time for another look?

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By Jerry Davis

Over the past several years, the demand for products with hard, textured UV coatings, while not overwhelming, has spurred the development of new nitrogen-curing equipment that addresses some of the "issues" of the old technology. As stated previously, the new systems use a different nitrogen-dispensing method, which delivers a more consistent and concentrated blanket of nitrogen to provide more predictable texturing results and easier operation.

Another drawback of older nitrogen-curing units was their limited use as only nitrogen-curing units. What happened when a printer needed both nitrogen curing for durable, textured, single-color graphics and a conventional system for printing multicolor UV graphics with good intercoat adhesion? In the past, that printer had to have both nitrogen and conventional curing lines. And frequently, one of these expensive pieces of equipment was sitting idle.

Newer nitrogen-curing designs are much more flexible. They offer the ability to cure with nitrogen when needed and can also be converted for conventional curing in a normal, oxygen-bearing atmosphere. This dual-use profile can be quite attractive in today's profitable market for high-quality, value-added nameplates and graphic overlays. If this is your market, such dual functionality to maximize equipment performance may be worth a closer look.

Nitrogen curing, then and now

Nitrogen curing--that old bowler hat of yesterday--is becoming today's space helmet. But does this technology represent an advantage to the printer? Within the market for nitrogen-cured products, are customers willing to absorb the costs required to support nitrogen-curing equipment, supplies, and procedures? The final judgement becomes one of dollars and cents. One thing is certain: Until either more advanced technology comes along or the need for extremely durable textured hardcoatings disappears, the need for nitrogen curing will continue to expand.

Jerry Davis is president of Ultraviolet Systems & Equipment, Inc., Houston, TX, a manufacturer of UV curing and germicidal UV disinfection systems. A member of SGIA's Technical Support and Signage Steering Committees, Davis has authored several articles on UV-curing technology and spoken at numerous technical conferences for the graphic arts.

Nitrogen-blanket curing made its first appearance in the late 1960s in niche applications that required textured print surfaces. At the time, UV curing was a little-utilized process in the screen-printing industry. But as toggle switches and analog displays gave way to membrane switches and domed keypads, the need arose for more durable print fields to accompany these controls in demanding environments. A new segment of industrial screen printers emerged, not "decorators" but "print technologists." And with their emergence, "print for decoration" was giving way to "print for information."

The insistence among manufacturing and industrial-control customers for highly durable, textured graphic overlays, faceplates, and similar components helped fuel the demand for nitrogen UV-cured products. Customers also wanted what we now accept as characteristics of all UV curing: high gloss, rich color tones, and efficient turnaround.

The early nitrogen-curing equipment market was served by the Linde Division of Union Carbide. Linde was a marketer of nitrogen and developed a UV-curing system that utilized a nitrogen blanket. The supply of nitrogen to the print industry never represented a major portion of Union Carbide's business, and as conventional UV-curing units gained popularity, interest in nitrogen units waned. So did Linde's involvement in nitrogen curing, and today, availability of such systems has reached the point of scavenging.

With the rise of conventional UV curing, ink formulators began to develop coatings that could deliver a low-gloss, matte, or textured surface without curing under a nitrogen blanket. Several such coatings are available today that provide durability and texture characteristics sufficient for many applications. The appeal of conventional-curing systems was further strengthened by the fact that they supported multicolor, overprinted images. The introduction of textured films that can be selectively printed with a clear "window" lacquer to create a part that looks nitrogen UV-cured also impeded the growth of nitrogen curing.

However, applications that require extended surface hardness and scratch resistance, long-term texture life, and non-marring gloss properties expect more than conventional UV-curing equipment and inks can deliver. And this fact has kept nitrogen-curing technology alive.


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