by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
Panpa Bulletin : November December 2006
36 | PANPA BULLETIN November--December 2006 UV or not UV? That is the question Why the sudden interest in UV inks? UV inks have been around for a long time. Sun Chemical was the first ink producer to develop UV inks back in the 1940s, so we have a good deal of experience with using them. In fact, DIC Graphics make UV inks in Sydney for other markets. However their uptake in newspaper production has been slow for a number of reasons, mainly to do with cost and the difficulties of implementa- tion. The current level of interest is due to the fact that newspaper printers are looking for ways in which to leverage their coldset printing technology and establish a point of difference. Anything that offers the possibility of improved quality and a means of adding value to the finished product without vast capital expense needs to be looked at closely. How do the inks work? Unlike conventional inks that dry on the web partly through evaporation and partly through absorption, UV inks contain photo- initiators that are activated when exposed to UV light. These bind the inks to the substrate through a chemical reaction and provide an extremely stable, fast-drying ink film. In order to generate this chemical reaction, the web needs to pass under a UV lamp. The position- ing of these lamps in relation to the web is critical in order to get the optimum drying time and adhesion. So are UV inks worth considering? There's no doubt that you can get very good quality web offset print results using UV inks. But if you're expecting UV inks to deliver heatset quality results on a coldset press then you'll be disappointed. They produce UV quality, not heatset quality. On the other hand, the mileage with UV inks is better and because they dry or 'cure' almost instantly, and -- if the press is run at the right speed -- there are no problems with rub-off. However, without sufficient exposure to UV light, the inks won't dry at all so if you run the press too fast, you end up with wet newspapers. The other attraction with the process is that instant drying allows you to run higher qual- ity substrates such as coated stocks and even some gloss stocks that might previously have been exclusive to heatset. What are some of the drawbacks? Cost is the main issue. UV inks are consider- ably more expensive than conventional offset inks, up to 10 times more for black ink. That's because the acrylate monomers and oligom- ers used in UV inks as well as the photo-ini- tiators used to start the curing process are much more expensive than the typical oils, resins and additives used in coldset inks. You also need to factor in the cost of the UV lamps, which need to be replaced at regular intervals. Current lamps have a life span of approximately 1500 hours which, in a busy newspaper plant, means fairly frequent changes. Then there's the extra power needed for the lamps which, if you're running several lamps on each web, can quickly mount up. Maintenance is another critical issue. The lamps themselves need to be kept dust-free, and the press itself also needs to be in top condition. The operating window for suc- cessfully using UV inks is very narrow so if the press is not set up correctly with regard to roller settings and blanket settings then wastage can very quickly start to escalate. You need to have an eye for detail and be scrupu- lous about your maintenance. Special consid- eration also needs to be given to the type of rollers and blankets used as conventional rollers, for instance, will swell up unaccept- ably if used with UV inks and washes. The inks themselves also need to be handled differently. Obviously exposure to light must be avoided to prevent the inks from starting to cure but, over time, there's also the possibility that they'll start to gel in pump lines so hand feeding is preferable. Is there a future for UV inks in newspapers? New developments and types of UV tech- nology are constantly being investigated to address issues such as running costs and production speeds. As yet, it's too early to say whether any of these will become widespread as viable commercial options. Much of the current activity is taking place in the US on narrow web presses and, there, the focus is on commercial coldset operations rather than regular newspaper production. As an ink sup- plier, we are happy to support customers who want to investigate the use of UV inks -- and there are available options -- but they need to approach the topic with open eyes and not regard it as a 'quick-fix', low cost solution to improve newspaper print quality. Ian Johns is web director with DIC Graphics Australia, manufacturer of a wide range of specialist ink products. For more information visit DIC s website at www.dic.com.au PRODUCTION "The operating window for successfully using UV inks is very narrow, so if the press is not set up correctly with regard to roller setting and blanket settings, wastage can very quickly start to escalate. You need to have an eye for detail and be scrupulous about your maintenance" "If you re expecting UV inks to deliver heatset quality results on a coldset press, you ll be disappointed " There s been a growing interest recently in the use of UV inks for newspapers. Ian Johns outlines some of the issues surrounding their implementation.