UV Curing

UV LED curing makes its mark in the labels and packaging space.

From converters to their customers, environmentally friendly practices are profoundly affecting the labels and packaging space. One such way that the industry can save – both from sustainable and cost perspectives – involves ultraviolet (UV) light emitting diode (LED) curing.

UV curing technologies have been designed to instantly cure specially formulated inks, coatings and adhesives through polymerization. UV curing can include medium-pressure mercury arc and microwave-powered lamps, as well as LEDs.

According to Phoseon Technology, both arc and microwave curing technologies rely on the vaporization of mercury within a sealed quartz tube containing an inert gas mixture. Mercury emits ultraviolet light when vaporized, while electrodeless lamps utilize microwaves to vaporize the mercury.

Electrode lamps harness a high-voltage arc struck between two electrodes to achieve the same result. When the mercury is vaporized into an extremely high-temperature plasma gas, it emits a spectral output across UVA, UVB, UVC and UVV bands that can be manipulated by introducing metallic additives to the inside of the lamps. When the ink, adhesive or coating formulations are exposed to ultraviolet energy, they are crosslinked into a photopolymer.

UV LEDs, however, are solid-state semiconductors. Compared to conventional lamp technology, LEDs contain no moving parts or mercury plasma gas. In addition, they often operate at temperatures nearly 1/10th of those dealing with conventional lamps.

Martin Kugler, corporate communications for GEW, states that the electricity consumption of a typical mercury arc system is 2,005,000 kWh over a 10-year period. The equivalent UV LED system would consume 950,000 kWh, a reduction of over 50%. In the US, at approximately 12¢/kWh, this equals a savings of $126,000. This is based on an 18" 8-lamp system with chiller, 60% uptime, two shifts per day and six days a week.

“Improvements in conventional reflector geometry have increased intensity at the web by capturing more UV energy and directing it in a true elliptical focus at the web, increasing curing power by 35%, thus reducing energy consumption,” notes Mark Hahn, VP of sales and marketing at AAA Press International. “UV LED curing technology has seen dramatic improvements in output power going from 16W/CM2 to over 30W/CM2, as well as significant improvements in optics design, allowing complete curing at higher line speeds.”

According to AMS Spectral UV – A Baldwin Technology Company, a mercury arc bulb can last 2,000 hours while the chips in an LED UV module can last 20,000 hours or more. This eliminates the need to frequently replace them as part of production maintenance.

“Over the first 20,000 hours of life, a typical LED system will lose about 15-20% of its UV output,” says Kugler. “After 20,000 hours, the LEDs will continue to work but output will degrade more quickly and the probability of LED failure increases. When a single LED fails, the user will not notice, as surrounding LEDs automatically increase in power to accommodate the loss. However, eventually, enough LEDs in a single area will fail and curing results will suffer.”

Stefanie DeBetta Langler, sales and customer service manager at Southern Lamps, explains that life expectancy and cost play a large role in a customer’s decision-making process regarding UV systems. “A typical LED system can cost $102,000 and the replacement lamp is $49,200. LED lamps are predicted to last 10 times as long as an arc lamp, but for 200 times the cost,” she says. “In comparison, a typical arc UV system will cost $28,500 and a lamp will be $258. The system is almost 1/4 of the cost and the lamps are 1/190th of the cost.”

Read more →