South Africa’s GM Graphix maintains, “UV LED technology uses significantly less power than its mercury counterparts. With its instant on/off capabilities, Phoseon’s curing is ideal for South Africa’s power fluctuations. The press’ electrical consumption is currently 30 percent less than GM Graphix’s other flexo presses. Solar panels at GM Graphix generate enough energy to run the press for 5.5 hours each day, which would never be possible with mercury UV.”
Central Valley Label in Fresno, CA, indicates that, before switching to LED curing technology, the plant was spending close to $40,000 to $50,000 per year on spare parts for the old UV mercury presses. “When the company switched to the Phoseon UV LED solution, that expense was eliminated. The presses with LED systems were so productive, so we were able to eliminate their night shift.”
Opaque Whites, Dense Blacks…
Beyond general label and package printing, UV LED technology is vastly superior to mercury systems for the curing of opaque whites, dense blacks, metallic and other densely pigmented colors.
The critical element each of these has in common is the requirement that UV energy travel through dense pigments, additives or films without being redirected or prematurely absorbed before full cure is achieved. Due to the physics of light and nature of UV LED output, depth of penetration is exactly where LED technology excels.
Due to longer UV-A (395-nm.) wavelengths as well as intensities that are four-to-eight-times greater than mercury lamps, UV LED technology drastically outperforms mercury lamps. The longer UV LED wavelengths naturally penetrate deeper, and by starting with a much higher irradiance, even if intensity diminishes as light travels through the formulation (due to absorption, scattering, and reflection), more light is still reaching the substrate.
For label and packaging applications where black, white, metallic inks represent process bottlenecks, switching to a UV LED process with its ability to penetrate deeper into the ink, will result in increased press speed, more opacity, stronger color, greater adhesion, better cure, greater yields and less scrap.
In the case of laminating and cold foil adhesives, since the UV energy must first pass through a film or foil construction in order to reach the adhesive, near visible output of UV LEDs is advantageous. Longer UV-A and UV-V wavelengths have superior luminous transmittance through materials, compared to shorter UV-B and UV-C wavelengths. The fact that the adhesive is cured between two films also eliminates any need for UV-C wavelengths, as none of the adhesive is exposed to oxygen, which can inhibit cure.
UV LEDs are significantly more efficient and effective at curing laminating and cold foil adhesives than mercury lamps. In addition, when compared to solventless chemistry, UV cured laminations and cold foils can be immediately processed following exposure:
- One-to-three-day curing time, required with solventless adhesives, is completely avoided with a UV process
- Higher irradiance and ability of UV LEDs, at 395-nm. to penetrate deep into the chemistry, makes the technology ideally suited for label and flexible packaging applications
If you find yourself interested in UV LED curing, consider upgrading one or two stations on your press to see how the UV LED system performs. This is the best way to become familiar with what is possible and demonstrate first-hand the many ways in which UV LED systems are superior to mercury arc lamps. Fully integrated solutions for narrow web upgrades consist of station-by-station building blocks, including light sources and power and control systems.
About the Author
Adam delivered a FLEXO Tech Talk with the same title as this article—LED Curing: The Future Is Now—on Tuesday, June 15, 2021.
Since 2002, Phoseon Technology pioneered the use of LED technology for life sciences and industrial curing. Through relentless innovation, it delivers high performance, reliable and patented LED-based solutions. Strong focus on customer collaboration has resulted in worldwide market leadership position and presence. Phoseon is an ISO9001-certified company manufacturing award-winning products that are covered by more than 300 patents worldwide. With a 100 percent concentration on LED technology. Phoseon has forged a reputation for superior reliability, business economics and environmental benefits.