UV has been the printing industry’s quiet revolution. While there has been prediction after prediction about the impact of different digital technologies whether toner, inkjet or offset inkjet, UV printing has arguably been responsible for more pages than the digital technologies combined.
Approximately 97% of all pages (newspapers included) are printed litho which means that any transition from conventional litho to UV has the potential to have a significant impact both for printers and for the industry as a whole. And this is what is seen with UV curing in commercial printing.
UV has been used in carton printing for more than 30 years; it is used extensively in label printing and has been used in forms printing, but issues around ozone and extraction systems always prevented its take up by commercial printing, except perhaps where over varnishing was needed.
The arrival of low energy UV has changed all that. Ryobi, now RMGT, showed LED UV at Drupa in 2008 and Komori was close behind with H-UV. This uses a standard mercury vapour lamp, doped to generate UV in a narrow spectrum, and requiring less energy to do so. As well as Komori, low energy lamps like this are used by Heidelberg with LE-UV, KBA with HR-UV, Manroland Sheetfed and Presstek on its 52DI Eco-UV press. Heidelberg and KBA can also offer LED UV alongside Japanese press manufacturers Sakurai and RMGT. Presstek will introduce LED UV to its 34DI at Ipex.
Craig Bretherton, product and marketing manager at KBA UK, says: “Commercial printers are also being attracted to this technology as it means difficult-to-dry stocks, such as offset, can be quickly turned around without the need for coating. In addition, due to the lack of a requirement for extraction and coating units in many cases, capital costs to add new drying technologies are not prohibitive.”
The advantages from using UV also include reduced emission of VOCs, ability to print on plastics and other hard to handle substrates, elimination of spray powder and reduced maintenance, if only because spray powder does not build up in every corner. In print terms this also helps lift and printing is sharper.
This is because the ink does not dry through evaporation and absorption into the paper, as with conventional inks. Instead the ink is trapped on the surface of the substrate in a cross-linked polymer lattice initiated by the UV energy applied to photoinitators in the ink.
Because there is no loss of ink volume as solvents are driven away by heat in a normal dryer, there is more pigment for a given volume of ink. This means printers will run higher densities for greater lift, or can run with a reduced ink film for the same impact.
This is important as the UV inks remain more expensive than conventional inks and because of the photoinitator component will remain so. But with greater competition and further technological advances, prices will gradually fall.
Prices will fall too for the LEDs and their pound per wattage output will increase, further increasing their versatility by opening up new compounds for ink makers to use and a greater choice of locations to fit systems to presses. Retrofit opportunities will increase. Bluprint UK already does this with AMS LED UV; Flint creates a package using the LED and its inks; and IST can retrofit either a lamp or LED system.
As well as inks, plates are a crucial component of a successful transition to UV in commercial printing. At Kodak there is a wealth of experience with the coatings needed for the harsher chemistry needed for UV printing. It has produced plates for packaging printing for many years and has developed new plate technology, including specifically for UV.
The inks and washes used to clean blankets and plates are more aggressive than on a conventional litho press. Historically the answer had been to bake the plate to make it more resilient. But this adds an energy hungry element to production and counters the beneficial impact that new generation UV has in cutting energy needed to dry on press. The trend to shorter runs also means that baking is out of the question.
For Kodak's plate scientists, this means creating a coating with greater resistance to the chemicals used without adding to the environmental cost. It has come up with two products suited to the new way of printing. The Kodak Electra Max thermal plate has a coating which offers good resistance to the washes and solvents used with UV printing, with no baking required. Furthermore, less developer is used in processing as a further environmental benefit.
In recent years, commercial printers have switched in numbers to Kodak’s Sonora process-free plate which require no processing and eliminate the equipment, energy and chemical waste associated with processing. These are also suited to new generation UV printing, up to 10,000 impressions with the standard Sonora XP plate, and to 30,000 impressions with the Sonora UV plate. For runs beyond this, the answer is the Electra Max.
But it is not a static market. New inks, new diodes and new varnishes are being developed all the time. And in its own labs, Kodak's scientists strive to keep ahead of these and other developments in litho printing.
Plates are a crucial component of a successful transition to UV in commercial printing. At Kodak there is a wealth of experience with the coatings needed for the harsher chemistry needed for UV printing.
It has produced plates for packaging printing for many years and has developed new plate technology, including specifically for UV.
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