Frequently Asked Questions
Here are examples of the type of questions we are asked about UV Drying Systems;
What is UV curing Technology?
UV curing Technology has been utilised since the 1970’s and provides a technology that cures an ink, coating or adhesive in milliseconds.
The ink, coating or adhesive is a special formulation that when UV light it applied to it, it cures instantly.
What is different between Conventional inks, coating and adhesives and UV curable?
Convectional inks, coating and adhesive usually contain solvents and /or water which has to be evaporated. This takes time and the solvents are emitted to the air around the drying area. The solvent can be as much as 60% of the total amount applied to a surface.
UV curable chemistry is 100% solids and when it has UV light applied to it, it forms a polymer which is the same volume as the liquid chemistry that was applied.
What are the benefits of UV Curing?
Obviously, UV curable materials being 100% solids less of the product needs to be applied meaning a saving in material applied. As there is no Solvent then there is nothing expelled to atmosphere.
As the UV curable chemistry cures rather than drying, it tends to adhere better to many more base/substrates than convention chemistry.
As it dries instantly secondary process can be carried out immediately.
What the real benefits to me as a printer?
As above. The ink will be dried instantly meaning that there will be no “set off” in the stack or in the reel. If sheet fed printing no spay powder will be required.
You will be able to print on many different substrates some which were difficult with solvent based inks. There will be no solvents in the work place and in general printing speeds can be increased. And post processing can be immediate meaning you can cut and crease and ship all in one go. Greatly reducing work in progress and releasing large areas of your shop floor.
Where can UV curing be used?
The applications are many and various.
Printing & Coating:- Packaging, Labels, Metal decorating, Point of sale display
Automotive and Aeronautic
LED Matrix display
What are the benefits of UV curing for offset sheet fed Printing?
Because the coasting or ink is curded instantly. i.e it forms a plastic film the surface is completely dry as soon as it emerges for the drying unit. This means on press the dot is frozen immediately improving print quality. On a sheet fed press there is no need for spray powder or other non-offsetting technology. Also as the print is totally dry in the stack the printed sheets can be further processed right away. That could mean immediate work and turn or immediate cut and crease. Thus reducing work in progress and it also speeds up delivery of final product to the customer. Additionally, using UV curing technology facilitates the printing on a greater variety of substrates from recycled board to polypropylene.
What about printing on a web press with UV curing technology?
Whilst, predominantly UV curing has been used with offset printing on sheet fed presses it is available for Flexo, Letter press and offset on web presses large and small. Because the ink or coating cures instantly the web can be rewound with no set off so it can be re wound or reprocessed in line. With web bypass printing units UV dryers can be mounted between colours which mean no in on by pass rollers allowing the press to be run a higher speed.
What about gloss coatings?
With both web and sheet UV cured costing can produce a very high gloss finish with high scratch and scuff resistance. Conversely there are also many matt costing available so that interesting matt and gloss images can be generated.
How good is the ink or coatings rub or scuff resistance?
UV cured inks and coatings provide some of the highest scratch, rub and scuff characterise available to the printer.
What do I need extract ducting and fans with Conventional Arc lamp UV technology?
The curing UV output needed for the old style UV curing inks and coating is at the short wave end of the UV spectrum. An arc lamp emits a range of wavelengths some of which, the longer ones are near visible light, are not required and some at the very short wave end produce Ozone. The bit in the middle does the curing. It is both the heat produce by the lamps and the Ozone generated that needs to be extracted. The Ozone needs to be ducted out of the working place.
What about temperature at the substrate?
Conventional UV systems do produce heat which is directed onto the sheet or web. This is taken away with lamp head cooling and heat sinks on the back side of the web or sheet.
What about the lamps don’t they have mercury in them?
Yes the lamps do contain a small amount of mercury which is of course contained within the lamp. This is similar to high output street lighting. The main issue is that the lamp run 1200 hours maximum, and have to be replaced. If broken the Mercury has to be recovered and disposed of correctly. The UV lamps also have to be returned to the supplier or to a registered recycling company.
What has change to allow me to consider LED UV technology?
The basic issue has been that LED’s emitting at the wave length required at the shorter wave lengths to match the photo imitators currently used were, and continue to be very expensive. In the last 10 years both LED suppliers and Ink chemistry manufactures have worked together and a. The LED manufactures have developed low cost high power LED’s but at slightly longer wave lengths and b. the ink suppliers have developed new initiators that respond at the longer wave lengths both matching up to provide a new UV curing technology.
So what is different between LED UV and conventional UV?
Apart from the different UV wave lengths being encompassed there are many differences which actually bring many benefits to the user. Electrical energy required is reduced by more than 50%, they need no ducting to atmosphere, they do not emit heat to the substrate, LED’s run for more than 25,000 hours without a drop in output, there are no heavy metals (mercury) and no issues with disposal of the lamps as there are no lamp changes involved.
Can I change to LED UV and carry on as normal?
Yes, the ink suppliers now have a complete range of LED Curable UV Inks for Offset and Flexo. Coatings are still in development because there is some yellowing due to the longer wave lengths used but this issue is being resolved. Inks and coating are more expensive but set of against the massive electrical energy saving the overall costs can still be lower.
Still need to know more, give us a call to discuss your needs on +44 (0) 844 3570157