Drying, Curing & UV LED UV:
a flexiproof curing option?
By Tom Kerchiss of RK Print Coat Instruments
I
ts not for want of trying, but when it comes to printing and converting it does take time when developing a new product, a concept or adopting an entirely new way of working for everything to come together. It must be proven beyond any measure of doubt that the advantages will outweigh the steep learning curve typically associated with new ways of working and that the commercial rewards eventually will be forthcoming.
Manipulating light/energy so that a liquid coating could be changed from said liquid to a solid state, altering the chemical, compositional properties of a substrate surface while improving the appearance, of for example a printed pack is an attractive proposition by anyone’s standards, especially print and converting. But energy curable UV has been a technology that by any ones standards has taken time to become a truly rewarding process. Developments on-going in LED UV technology show great promise and point to new processing possibilities. But just how long has it taken for scientists, ink, and adhesive, coating formulators, lamp and power source manufacturers and others to resolve the many issues surrounding radiation curing? Where to begin - The first patent for UV curable inks was granted to General Electric as far back as 1946 when they were experimenting with ionising radiation for the cure of solvent-free coatings. The woodworking, floor covering and coding and marking segments of industry were early
adoptees but for printing and converting the challenges to overcome have been many, and battles have been hard fought over recent decades. Heat; the generation of heat from a variety of sources, including the press, the working environment but particularly from UV lamps and cumbersome power sources placed limitations on the type of substrate that could be processed. It could be argued with some justification that addressing the problems associated
with heat was high on the agenda of everyone engaged in the development of LED UV. In reality the development of LED UV is not just about managing heat, LED UV provides many processing benefits – in the right situation.
LED UV is a solid-state device that is optimised to function within a relatively narrow part of the ultraviolet (UV) spectrum. LED UV lamps are energy efficient, do not generate ozone and are mercury-free. The LED UV lamps that RK Print Coat Instruments are integrating in with the FlexiProof LED UV colour communication-proofing device for users and producers of flexography are designed to operate within the narrow but important 385 or 395 nm wavelength.
LED UV lamps are comparatively cool in operation when compared with conventional UV lamps, which emit heat in the infrared wavelength. Reduced heat minimises or eliminates the need for many complicated cooling mechanisms such as chill rolls or water-cooling needed for many fragile or heat sensitive materials and processes. White and highly pigmented inks can in most circumstances be cured more effectively with LED UV than with vapour lamps. With white inks, the additive titanium dioxide absorbs all wavelengths below 380 nm. LED UV devices emitting energy at the slightly higher output of 380+ nm evades the
titanium dioxide particles associated with white ink enabling the lamps to penetrate and make for a more thorough and deep cure.
RK Print Coat Instruments FlexiProof LED UV is a compact integrated device, similar to the FlexiProof UV and FlexiProof 100. Designed with multi-tasking in mind, all FlexiProof devices are scaled down but are component critically exact versions of a flexographic press. The FlexiProof makes it possible to trial new materials, new formulations, colour match and undertake various printability tests without the need to take a production machine out of line or without out- sourcing.
The FlexiProof UV and FlexiProof LED UV differ from the original FlexiProof 100 in that they incorporate a miniaturised UV system that enables users to print and cure in a seamless manner to fit in with a customers’ workflow practice. With its integrated UV system the FlexiProof UV and LED UV are able to detect and highlight blemishes such as pinholes. Conventional UV conveyors are unable to pick up on pinholes because as the proof is taken to UV conveyor chemical changes take place that make pinholes and other blemishes difficult if not impossible to detect.
Xwww.rkprint.com
18
February 2022
www.convertermag.com
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