By Olivia Cahoon
Part 1 of 3
Manufacturers use UV printing technology for durable, high-quality graphics in high-speed production processes. Curing is an important part of the UV printing process that instantly dries UV inks and coatings for scratch-resistant graphics. It offers reduced drying speeds and eliminates ghosting and flaws produced by naturally drying inks.
Curing systems are available as traditional UV and UV LED devices. Due to a shorter wavelength, UV LED systems are compatible with UV-sensitive materials, thin substrates, and films that soften. However, greater compatibility comes with increased costs.
Curing technology is used for digitally printed applications due to its compact size, ease of use, and high intensity. Curing enables inks and coatings to bond to surfaces like ceramic, concrete, metal, plastic, and wood. UV-cured applications include three-dimensional (3D) printing, bottles, coding, labels and packaging, products, and signage.
Traditional UV curing devices include an arc lamp, arc light, or discharge light—lamps that produce light by an electric arc. Discharge lamps are named for the gas contained in the bulb including argon, krypton, mercury, metal halide, neon, sodium, and xenon, shares Sara Jennings, senior technical marketing engineer, Phoseon Technology.
Traditional arc lamps use an electric arc inside a mercury gas to excite atoms, which then decay, emitting photons. Microwave lamps excite the gas via microwave emission while xenon lamps use xenon gas without mercury, explains Jennings. Xenon lamps are used as replacements for UV mercury light but can only be flashed.
“UV LED is an electronic light source with electromagnetic radiation that contains a wavelength shorter than that of visible light but longer than x-rays,” says Jennings. UV LED devices utilize LEDs to dry ink, coatings, adhesives, and other UV-sensitive materials through polymerization instead of evaporation. “UV LEDs are solid state devices containing no moving parts or mercury plasma gas and often operate at temperatures nearly one-tenth of temperatures emitted from traditional curing lamps,” she continues.
According to Jennings, a UV LED light source’s spectral output for curing UV LED materials is very narrow, between 350 and 405 nanometers (nm), as compared to UV mercury systems, which operate from 200 to 700 nm. She believes UV LEDs efficiently convert 20 to 40 percent of the input electrical power into usable UV light with no harmful UV-C or infrared light output. This translates to a 70 percent energy savings compared to mercury-based lamps.
Printing equipment developers use UV LED curing technologies for controlled curing intensity on thin plastics, foils, and films that soften, warp, or discolor under heat produced by traditional UV devices. Jennings offers, “UV LEDs are easy to maintain with no moving or replacement parts and improve up-time for printing equipment.”
Lamp Life Expectancy
UV lamp life depends on the lamp’s operation, environment, and curing device. UV lamps have high power consumption with a lower life than UV LED systems. Re-lighting UV lamps is not instantaneous and requires an extended run-up time and cooling before re-lighting. “Traditional UV-curing lamps typically last between 500 and 2,000 hours and need to be replaced as UV output decreases,” comments Jennings.
While most UV lamps are designed to last 1,000 hours, Meredith Stines, president/CEO, American Ultraviolet, says some spot cure units only last between 200 and 400 hours. “They’re usually replaced twice a year or more depending on usage,” he offers.
UV LED lamps offer low power consumption and instantaneous on and off switching—allowing users to recover investments more quickly. Because it is a solid-state electronic device, Jennings says UV LED systems deliver more than 20,000 operating hours with a minimal drop off in the unit’s life. In some cases, UV LED devices have exceeded 60,000 hours of operation.
Lamp life also depends on proper handling, installation, reflector maintenance, number of starts, and the system’s cleanliness, points out Jack Karas, managing partner, Oxytech Systems, Inc. “We’ve seen as much as 1,500 hours with 1,000 watts per inch mercury vapor lamps but typically expect 1,000 hours. LED devices can reach 20,000 hours.”
Although UV LED devices have a greater life expectancy than traditional systems, they also have a higher price point. As a specialized device, UV LEDs are considered an equipment upgrade while traditional UV devices are viewed as consumables.
To combat a higher investment, UV LED devices offer operational savings including lower operating temperatures and energy efficiency. “Coupled with the elimination of exhaust and higher yield, UV LED curing can increase total energy savings by as much as 90 percent,” offers Jennings. Manufacturers should compare device costs with potential operational savings in addition to increased revenue from UV-cured products.
Manufacturers use curing devices for industrial and assembly applications, labels and packaging, bottle printing, 3D printing, coding, and signage. Curing systems are selected based on the customer and application’s needs.
The packaging industry uses traditional UV devices for its compatibility with a variety of substrates and applications. UV devices produce a wide band wavelength that offers a deeper cure for challenging applications. However, UV devices also produce high heat and can melt heat-sensitive films or substrates.
UV LED systems are compatible with heat-sensitive substrates like bottles, electronics, granite, labels, plastic packaging, posters, and wood. “UV LED curing is now an accepted tool in the printing industry because it allows advanced capability on challenging applications for industrial printers,” says Jennings. It also offers increased productivity, operating economics, and sustainability for bottle label applications.
Touch panel display manufacturers use UV LED curing technology. According to Jennings, it provides stable output, low heat, and no hot spots. Curing is also suited for mobile phone assembly for camera modules, camera lens, earpiece, microphone, and casings. She offers, “the ability to provide consistent output even during high-volume jobs with cured sensitive products makes UV LED technology an effective solution in manufacturing settings.”
As curing devices integrate into manufacturing settings, high-performance UV LED curing technology advances. “With the features it offers today, it opens the door to new applications and new revenue opportunities with the ability to print on heat sensitive and thinner substrates, offering increased profitability for printers and end users,” admits Jennings.
Manufacturers select curing devices based on customer and application needs. For industrial printers, UV LED systems are popular in assembly applications with the ability to broaden applications and increase productivity and sustainability.
Jun2018, Digital Output