Martin Habekost
Wide-format inkjet
Inkjet inks for wideformat printing
Many companies showed their advancements in inkjet technologies, but many products that were shown at the 2008 Drupa never really made it into the marketplace or did not fare very well
For wide-format and super-wide format inkjet printers it is important to know what type of ink system is being used with the printer. One might wonder why this is important. It is important since no ink can be used for all types of applications and substrates. There are solvent-based inks that can be used on a variety of substrates, but these inks require a good ventilation system in the print shop to remove the emitted VOC’s. In order to move away from harmful solvents the so-called eco-solvent inks were developed. These inks are quite often glycol-based, which is derived from mineral oil. The eco-part of these inks stem from the fact there is less need for forced ventilation to remove harmful airborne substances. The substrate needs to be warmed up to become receptive for these inks and the solvent needs to be removed as well to achieve proper drying.
tem is drawing a lot more electrical power that a UV-LED system. You need to do the calculation which system will cost you more to operate and how do the cost of the consumables play an overall role.
Water-based inks are another possibility for inkjet inks. Since it is necessary to remove the water from them after printing, either the media gets heated and/or forced air is applied to the media to remove the water, so the ink will be dry. Prints made with solvent- or water-based inks quite often require a lamination so the prints can be handled rather quickly and also extend the fade-resistance of these prints in an outdoor application. One might say, “well then, use UVcurable inks. The inks are almost instantly dry and the prints can be handled rather quickly. Quite often the prints are durable enough for an outdoor application where resistance to sunlight and weather is required.”
The latest developments in the inkjet ink field are the latex inks and resin-based inks. Both ink systems use water as the main ingredient but the carrier for the pigments is either latex- or resin-based. Inkjet printers using these types of inks also need heaters built into the printer, so the media becomes receptive for the ink and the ink also dries properly. HP just introduced their new and improved latex inks. According to HP, these inks outperform eco-solvent inks in regard to faderesistance and other properties. It is also said that a wide variety of substrates can be used with these new latex inks. Since the inks are water-based there is no need for extra ventilation to remove any harmful substances emanating from the printer.
This answer is only partially correct. UV inkjet ink does adhere to many different substrates but not all of them. Certain substrates still need a corona-type pre-treatment or coating to make it receptive to this type of ink. The media also needs some kind of heat application during the print process to soften up certain type of plastic materials so they become receptive to the ink. With UV-curable inks there is always some curing after the initial print phase. This might lead to possible odour generation if the printed material is rolled up right away after printing.
Various reports on the internet suggest that there will be some quite interesting developments happening very shortly and they will be shown at Drupa 2012.
DRUPA 2012, the inkjet DRUPA, again?
This leads me to my next segment. Drupa 2008 was touted as the inkjet Drupa. Many companies showed their advancements in inkjet technologies, but many products that were shown at the 2008 Drupa never really made it into the marketplace or did not fare very well. The upcoming Drupa will show the advancements that have been made and that inkjet will deliver on promises made in the past. It will be interesting to see what kind of developments have happened in this market segment.
Usually, UV-curable inkjet inks are cured (aka dried) using a mercury-vapour UV lamp that can be part of the scanning print head assembly or is built stationary into the machine and the media passes under the lamp array. One of the latest technological advancements in this area is the UV-LED technology. This technology use small but powerful LED’s that emit the required UV rays. Their advantage is that the LEDs do not consume as much power as a conventional mercuryvapour lamp. The LEDs also do not get very hot, so they can be closer to the printed substrate. UV-curable inks made for use with mercury-vapour lamps cannot be used with UV-LED equipped printers.
What classifies a printer to be a wide-format printer?
Wide-format printing seems to encompass any inkjet printer that can print on substrate up to 2.5m in width and superwide printers are those that are capable of printing onto substrates up to 5m in width. The ink and inkjet head technologies differ from manufacturer to manufacturer and each of the wide-format or super-wide printers cater to certain market segments.
This is due to the nature of the emitted UV spectrum. Mercury-vapour lamps emit a broader UV spectrum with some peaks in the 200 nm range of the 200 to 400 nm UV spectrum. UV-LEDs emit only a very narrow band of UV light, which is more towards to middle of the UV spectrum. The photoinitiators in the UV ink, that are needed to start the curing process have be tuned for this different type of UV spectrum. Since this technology is still being developed and is not as widely used as mercury-vapour UV curing, the photoinitiators used for LED curing are more expensive and therefore make the ink also more expensive. One still has to take into consideration that a mercury-vapour UV curing sys-
February 2012 | Graphic Arts Magazine
Wide-format printing at Graphics Canada 2011
At the Graphics Canada trade show I spoke to a few suppliers and manufacturers of wide-format inkjet printers. It seems
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