In modern presses, the ink doesn’t dry. It is cured. From drying due to absorption by paper, the ink technology has come a long way in form of newer formulations and newer means of drying or as the modern nomenclature goes, energy curing.
The basic funda is that with absorbent substrates, first, the ink dries by penetration into the paper fibres, followed by oxidation and polymerisation. This reaction is accelerated by raising the temperature using IR driers.
As UV curing came into the picture, the need of substrate to absorb inks was done away with and a wider spectrum of substrates, even if non-absorbent (MetPet, PP sheets, metals, foils, etc), can now be printed on offset presses.
Most of the new presses put into service in the country, especially those installed by packaging printers, are UV-enabled. It has several advantages.
What is UV curing?
When the UV inks are exposed to UV light, photoinitiators in the ink activate a polymerisation reaction of vehicles, resulting in ink drying. In this case, the ink film dries completely as soon as the exposure occurs. This is a huge advantage to get a perfectly dry printed sheet off the press so that it can be immediately put on to converting processes. In addition, machines can be run at their optimal speeds on different kinds of substrates, absorbent and non-absorbent, without having to use spray powder or aqueous primer to avoid set off.
Back to basics, conventional UV dryers use mercury vapour lamps that radiate UV light of wavelength between 100 to 380nm. These lamps generate heat which can affect the substrate and hence, the system requires optimum cooling, plus, a provision to eliminate ozone that is a byproduct of the process. This is the basic theory of any UV offset press with minor tweaks by different manufacturers.
Now, some offset press makers in the last few years have developed new modified metal halide lamps, which use less energy to operate.
These special-purpose lamps emit narrower spectrum of light than a conventional lamp. It eliminates shorter wavelengths that create ozone and longer wavelengths that produce IR radiations. Therefore, with these systems one can do away with the provision to extract ozone, plus it requires lesser cooling.
Komori calls its patented version as H-UV, where H stands for ‘highly-reactive’ because it combines special purpose lamps and high reactive H-UV inks. The inks are more sensitive and can be cured with low energy lamps. This technology has attracted significant traction among Indian printers with over 12 installations. Ink manufacturers such as Toyo, DIC, Toka and
Taniguchi have added H-UV inks to their stable.
Heidelberg’s version is named as LE-UV, where LE is ‘low energy’ and KBA calls it HR-UV.
The new kid on the block is LED-UV
LED-UV further takes down the energy consumption by replacing UV lamps with light emitting diodes.
This is because, instead of emitting a spectrum of wavelengths, the LED lamp emits light of a given wavelength, which is required for curing.
Ajay Aggarwal of Komori says, “LED-UV works very nicely for web presses. In sheetfed, there is a slight problem. What happens is LED-UV lamp needs to be very close to the media to dry. Therefore, the distance between the lamp and the cylinder needs to be very narrow; so in the sheetfed press, and specifically when you are doing thick boards and plastics, at the edge it hits the LED lamp. Therefore, this technology didn’t work smoothly.”
But there is progress. LED-UV is already becoming common in wide-format presses. “HUV/LED is also the technology that is being used in digital B2 size press and the web press that Komori is introducing with Konica Minolta/Landa,” adds Aggarwal.
This new kid on the block is rapidly developing. One of the highlights of the year that passed was the Nobel Prize for physics awarded to the trio of scientists in Japan and the US for the invention of blue light emitting diodes (LEDs).
This invention has a significant relevance for graphic arts sector as well. Faridabad-based APL Machinery, who has partnered with Air Motion Systems, US, a manufacturer of UV and LED curing systems, is thrilled with “what we see a great benefit to the print industry”.
“The LED trend will catch up due to energy saving. It has already successfully replaced in televisions and automobiles. Next is lighting. Trends of developing LED technology will replace conventional UV in a short span of time,” says Rajeev Kapoor of APL Machinery, which is engaged in manufacturing of full range of UV coating and curing.
Even though LED-UV technology for curing inks is at a very nascent stage, APL’s client, Coimbatore-based Shree Maruthi Printers, is showcasing LED-UV printing technology, perhaps the first time in India.
With this new add-on on Shree Maruthi’s 10-colour Heidelberg press, their customers will be able to reap the benefits of the technology, says Thilak Kumar, the company’s director.
On the LED-UV front, New Delhi-based Provin Technos is demonstrating its Ryobi 920 sheetfed offset printing press equipped with online LED-UV printing technology. It has sold this machine to New Delhi-based Impact Promotions. Perhaps this is the first press installation in India with online LED-UV curing system.
Savings with LED UV
Vinay Kaushal of Provin Technos says, “compared to a conventional lamp, this latest LED-UV light source by Ryobi consumes only 10% power.”
In November last year at Labelexpo India, UV Graphic Technologies, headed by Abhay Datta, launched what it calls a completely Made in India LED-UV curing systems for flexo, offset, gravure and letterpress.
According to Datta, LED UV is the future of UV technology. He says the lamp life is of 50,000 hours, which equals to 30 lamp changes of conventional UV systems. “Besides power saving, it is also the uptime of the lamp that is crucial. In case of conventional UV systems, the lamp needs time to warm up, and then it has to remain on during the make-ready. With LED-UV, the lamp instantly switches on and off,” he adds.
As a technology, LED generates zero-heat. So, the need to have chilled rolls or chilled drums is eliminated. Also, the footprint is way too small as compared to the control panels of conventional systems.
“Since LED UV is an open platform (without patent as in case of H-UV), most of the ink players are gearing up to manufacture LED inks,” he adds.
While the prices of UV inks are twice or thrice that of standard inks, the new generation of HUV/LE and LED inks command even more of a premium, as much as 50% more than standard UV inks, or four or five times that of normal inks.
The PrintWeek India view
The buzz that one hears at PrintPack suggests that LED curing looks more feasible today. Post-PrintPack, LEDs will begin to make a small penetration into the Indian market. At the moment, LEDs are still fairly expensive and much lower in curing power output than lamps. The inks must be tweaked to reduce the cost. Even so, over next few years, the energy savings and elimination of metal halide in the standard UV bulbs may drive the technology toward LEDs.n
What ink manufacturers say
BS Kampani, Toyo Ink
In the HUV and LED, because we are using lamps with lower light intensity wavelengths, the heat generated is much less, so the formation of ozone is more or less eliminated or minimised, compared to the UV lamps dependent inks. Toyo Ink has been a pioneer in the LED curing inks for commercial printing seven years back with Ryobi and had displayed the technology at Drupa 2008.
Availability: Inks for the HUV and the LED type would have to be imported as the volumes are too low to justify their manufacturing locally. The resin technology too would have to be understood well, before we start manufacturing in India. As far as Toyo Ink and Toyo Arets are concerned, the inks would be available in India depending on the agreed commitments. These inks need special temperature storage warehouse and air-conditioned press rooms.
Pricing: The price would definitely depend upon the volumes and the regularity of the offtake. The price difference between a conventional UV and the HUV, LED could be in the range of five to 10% higher in the mid volume range usage. We would also be having knowledgeable technical servicing people from our overseas companies to train our younger technicians for the after-sales service.
RY Kamat, Micro Inks
Availability: We, at Micro Inks, manufacture radiation curable inks and coating which cure under conventional UV lamps. We also have developed a technology for manufacturing the materials which can cure under H-UV/LE UV lamps. Radiation curable inks and coatings are available both for conventional and H-UV/LE UV system as well as for LED curing.
Pricing: The H-UV/LE UV inks and coatings are expensive and that for LED curable materials are even more expensive than the conventional UV curable materials. The difference would minimise over a period of time with more number of installations as well as due to research for the new more economical raw material for formulating inks and coating for these systems.