What if you could optimize the balance between access time and plate performance, without compromising print quality when using a UV LED exposure?
DuPont Cyrel Solutions’ Cyrel Lightning plate, a recipient of FTA’s 2022 Technical Innovation Award in the Prepress Graphics category, addresses that challenge and more. These plates are formulated from the ground up with UV LED exposure characteristics in mind.
DuPont’s Global Technology Leader Suniti Moudgil explains, “Cyrel Lightning plates use chemistries with tailored UV profiles to achieve tunability between surface- and through-cures. This enables a balanced cure that can be tailored to the unique dynamics of a scanned LED exposure sequence. At the same time, it provides sufficient through-cure using a finely tuned UV absorption profile.”
All photos courtesy of DuPont Cyrel Solutions
Cyrel LSH is a hard-durometer plate with a smooth surface, ideally suited for advanced surface screenings and optimized for a broad range of substrates and clean pressruns in flexible packaging, tag, label and paper printing applications. The plate exhibits excellent compatibility with solvent-based and water-based inks, and good compatibility with UV inks. Plates are offered in 045 and 067 gauges.
- LSH 45 plates measure 0.045-in. thick, have a durometer of 75 Shore-A, are capable of holding a 1 percent to 98 percent image reproduction at 150 lpi, can achieve a minimum positive line width of 2 mil with a minimum isolated dot size of 50 microns and a relief depth of 0.0195-in. to 0.022-in.
- LSH 67 plates measure 0.067-in. thick, have a durometer of 68 Shore-A, are capable of holding a 1 percent to 98 percent image reproduction at 150 lpi, have a minimum positive line width of 2 mil, a minimum isolated dot size of 50 microns and a relief depth of 0.0195-in. to 0.022-in.
Rethinking Exposure
“If photopolymer formulations were optimized for LED exposure from the start, there would be less of a need to compromise between productivity and quality. Optimized flexo plates, along with experienced application support staff, yield the best results,” according to Christian Apenberg, regional marketing manager, East at DuPont Cyrel Solutions and Yuyang Du, research investigator, who jointly authored an article, “UV LED Plate Formulation: Achieving Balance Between Surface- and Through-Cures,” in the October 2021 issue of FLEXO Magazine.
The team indicates, “Fast surface-cure effectively mitigates oxygen inhibition between passes of LED exposure when the plate is in the dark. At the same time, it provides sufficient through-cure through a finely tuned UV absorption profile.”
DuPont, for its part, claims that it has rethought plate formulation, specifically for UV LED exposure. It says that the finely tuned profile “leads to an exposure time reduction of up to 42 percent; improved quality especially in isolated highlight dot and superior print quality amongst LED-exposed plates.”
In making many of those same observations, Apenberg and Du urge flexographic printers to, “Take time to identify the best products to use with your equipment to reap the advantage of the benefits of this new generation of exposure devices.”
Members of the LSH plate development team hold, “Recent developments in UV LED technology have opened the doors for LEDs to be used in curing inks and also in the flexographic plate making process.” Specifically, they note, “UV LED exposure systems deliver energy to the photopolymer differently from the conventional exposure units (see Figure 1). LEDs emit UV radiation at a very different level of intensity (15-20 times higher—LED output: 300 mW/cm2, five passes, 20 seconds per pass, cycle time 26 minutes: 30.000 mJ/cm2) and with a narrower emission spectrum. UV LED exposure systems scan over the plate during main exposure, instead of a constant exposure on fluorescent lamp systems (see Figure 2).
That is exactly what prompts Apenberg and Du to report, “This is why so much effort is put into developing an optimal recipe (set of exposure parameters) to let LED-exposed plates match or exceed the characteristics of the same plate posed with a bank system.”
Keeping It Consistent
Developers point out that, “Consistent formation of the small dots, mid tones and the surface texture help to deliver consistency, which means: customers come to color faster because of how the plate delivers the ink the same way every time the plate is put in the press.” Furthermore, they say, “The LED exposure unit helps to hold the smaller highlight features, like better fade to zero and smaller and more controllable overall highlight gain, which expands the tone range.”
Ask the experts, “What did you achieve?” Plus, “How did you achieve it? Results are attributed to understanding the impact of scanning, high-output LED exposure on photopolymer plate formulation and addressing the differences compared to conventional fluorescent tube exposure. And the actual list of results: reduced access/exposure time, improved productivity when using state-of-the-art UV LED exposure devices and highest-possible plate quality.”
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