Frequently Asked Questions

IR related questions

How are IR and UV drying/curing used for producing printed electronics?

The production of printed electronics requires several different processes such as drying/curing conductive inks and protective coatings, sintering, and laminating. IR is used for both drying and sintering in printed electronics applications. Learn more>

UV curing is used for curing conductive inks, coatings and laminating such as for RFID tag applications.

Sintering printed electronics is also possible using Xenon flash lamps without damaging temperature sensitive substrates.

How can I reduce connected electrical power (KW) and thus energy costs for users of my printing press?

The key to reducing the connected electrical power and thus the electricity service needed by your customer, is to choose the most efficient drying and curing equipment available for the printing process. The most efficient IR drying and UV curing systems convert more of the incoming electricity into useful energy to dry or cure the ink or varnish. For example, Heraeus IR systems are available in a variety of wavelengths to best match the ink and with high power density. Similarly, Heraeus UV curing systems incorporate specialty optics to increase power density onto the substrate and efficient heat management.

How do Heraeus technologies help me design an environmentally friendly and sustainable press?

For environmentally friendly drying and curing it’s important to consider VOCs, carbon emissions, and overall system efficiency. Since IR and UV technologies typically dry or cure with inks that contain little or no solvents, no volatile organic compounds (VOCs) are given off during the drying/curing process. Likewise, IR and UV technologies lower carbon emissions because, unlike most thermal drying ovens, they are both very efficient electric technologies. Additionally, Heraeus designs its IR and UV systems with energy efficient features such as flexible controls that allow turning down the power or turning off sections when not needed and optimized optics to improve the output per unit of electric power.

What’s the best way to determine which IR or UV product is the best solution for my press design?

Because there are many factors to consider and many possibilities for a specific printing press, it is best to involve IR and UV technology experts early in your design process. Discussing your specific requirements and running trials and testing can help the team develop an optimized solution for you. Heraeus has IR and UV technical experts who work alongside you. We offer testing in our Application Competence Center or at your facility to help you create the best drying and curing solutions.

What are some considerations for designing the drying/curing on a hybrid press that will run both water-based and UV inks?

The main consideration for a hybrid press is to position the IR drying prior to the UV curing so that, if water-based UV inks are used, the water can be removed by the IR prior to the UV curing. Of course the controls need to be tightly integrated for automatic control of the IR and UV in relation to print speeds, cure width and safety interlocks. Contacting Heraeus IR and UV technology experts early in your design process can help you get to an optimal solution faster.

How can IR drying and UV curing reduce or eliminate VOCs?

IR drying is used with water-based inks which contain very low or no VOCs. Likewise, UV-curable inks typically have very low or no VOC content. Therefore a printer using solvent inks may be able to use IR and UV technology to eliminate the need for inks which contain VOCs, depending on their specific printing process and the availability of suitable inks.

What are some of the safety concerns related to IR and UV technology?

IR drying - Infrared heat does not produce toxic fumes or radiation, so it requires no special shielding or pollution controls. Typically the IR module requires heater guards to protect workers and safety interlocks to prevent overheating and possible combustion of the substrate.

UV curing – All UV curing systems require light shielding to protect workers and is an integral feature of the UV system design. Mercury-based UV curing systems produce ozone, but this is quickly dissipated through the cooling air exhaust (water-cooled UV systems may require some exhaust air to remove the ozone). Traditional UV lamps containing mercury should be disposed of in accordance with local regulations, the same as fluorescent indoor light bulbs. UV LED curing technology does not produce ozone or contain mercury, so this is an advantage over traditional UV curing. UV LED lamps should be disposed of in accordance with local regulations, the same as liquid crystal displays typically.

Question related to both, UV and IR

Is it possible to integrate UV LED curing into my high-speed industrial digital inkjet variable printing?

Yes, UV LED curing is ideal for industrial digital inkjet variable printing because of its small form factor. UV LED curable inks are available and new printers are now available with UV LED. However, it is possible to retrofit an existing line as well. To learn more, read the technical article, Adoption of UV LED Curing: Trends and Benefits for Industrial Printing.

What is UV pinning and why is it used in digital inkjet printing?

UV pinning is the process of partially curing or “precuring” an ink to fix it in place and prevent it from spreading out or mixing with subsequent color inks. It is used in single-pass digital inkjet printing to provide the highest image quality -- both color registration and rendering. Typically the UV pinning system sits next to the inkjet print head. The UV energy from the pinning system causes the ink to gel which stops dot gain by holding the ink droplet in place until final UV curing by a second higher energy UV curing system. UV pinning is especially useful for low absorbance substrates such as coated paper and plastic films and multicolor ink such as labels.

Will UV LED lamps work in a glass or plastic decorating, direct to object screen print or digital inkjet machine?

Yes, this is already a commercial application for UV LED curing. The small form factor and long wavelengths are often ideal for fitting into these kinds of presses and curing highly pigmented decorating screen or digital inkjet inks. The low heat of UV LED helps protect plastic substrates from damage. Example applications include bottle caps, glass bottles, ceramic tiles, plastic bottles, etc. for beverages, glassware, cosmetics, and personal care products.

How are UV LED inks different from traditional UV inks?

All UV-curable inks require a photoinitiator (PI) to initiate the photopolymerization process. Traditional mercury-based UV curing lamps emit broadband UV energy with a large percentage in the shorter wavelengths. And since efficient UV curing requires closely matching the PI absorbance wavelengths to the emittance of the UV lamps, most traditional UV-curable printing inks use a combination of PIs that absorb shorter and longer wavelengths of the spectrum emitted by the mercury-based UV curing lamps. PIs absorbing the shorter wavelengths are useful for producing good surface cure, while the PIs absorbing the longer wavelength are good for curing through the print to ensure good adhesion to the substrate.

In contrast, UV LED lamps emit nearly monochromatic UV wavelengths at either 365, 385 or 395 nm. So for efficient curing with UV LEDs, an ink needs to incorporate longer wavelength PIs. Some formulators now offer inks that work with both traditional and LED UV curing lamps by using a short wavelength and a longer wavelength absorbing PI in the ink.

Another consideration for printing inks is the absorption of the various pigments. For example, this can make UV curing of dense black inks more difficult than a yellow ink. Selection of the PI combination with longer wavelength absorbing PIs is important to overcome this issue.

Can I use UV LED technology to cure overprint varnishes?

Traditionally clear overprint varnishes (OPV) cure with broadband mercury arc medium-pressure UV curing lamps which emit shorter wavelengths (UVC & UVB) along with the longer wavelengths (UVA). OPVs contain photoinitiators (PIs) that absorb these wavelengths close to the surface of the OPV producing the scratch, chemical resistance properties that are required by the products, without causing problematic yellowing of the clear coating.

In contrast, UV LEDs emit longer wavelength energy, so curing OPVs was a challenge. Today, formulators use specific additives alongside longer wavelength PIs to cure OPVs without causing yellowing. These LED formulated OPVs are more expensive, but are mostly offset by the energy cost savings.

What should I consider when converting a press design over to UV LED technology?

First, make sure UV curable inks designed specifically for curing with UV LED lamps are available for the intended press application you are designing. Compared to traditional UV curing technology, UV LEDs require much less space with typically lower cooling requirements. So think about ways to take advantage of this in your design to minimize floor space, but take into account if water-cooled UV LEDs will be needed for the press application and allow space for that plus a water chiller. Also, UV LEDs are easy to control, i.e. they have instant on/off and dimming capability, and can be set up to operate only portions as needed across a given width of the press. By taking advantage of these control capabilities you can design a more energy efficient press that’s less costly to operate. Finally, the connected load for UV LEDs is much less than that of traditional UV curing lamps, so this may enable adding other electrical loads to the press without requiring higher electrical service.

What differences are there to consider for ink management with UV-curable inks?

Unlike traditional solvent and water-based inks, UV curable inks will not dry or cure in the press, so ink management is much easier. For example, at the end of the day, there’s no need to flush and clean ink out of the press and ink handling system. The press can simply be restarted the next day.

UV related questions

If most of my printing press buyers use solvent inks, can I still use IR technology?

IR technology is not recommended for solvent inks due to fire hazards as the solvents evaporate. However, if your printing press will be used in print processes which use water-based inks, then incorporating IR capability onto your printing press provides more production flexibility and lower operating costs for your customer and widens the market for your press.

What is the optimal distance between the infrared emitters and the product surface?

The quality of the material and other parameters influence this distance.

Optimal parameters can be worked out by tests in our application centre or from experiences in earlier applications.

What are some considerations for selecting IR drying equipment for my press?

1. Wavelength - IR drying with medium wavelength emitters such as Heraeus Carbon IR (CIR) technology, are most efficient for drying water-based inks. If the press will be used to print onto materials which absorb the ink such as napkins and uncoated cardboard, then consider using a hybrid emitter such as the Heraeus twin tube which emits both short wave and medium wave IR. This combination of wavelengths provides both surface drying and drying in deeper layers where the ink is absorbed.

2. Power Density – IR emitters with high power density mean higher production speeds are possible in a smaller footprint.

3. Heat management – Choosing a medium wavelength IR emitter such as the CIR means there’s no need for water cooling which simplifies your press design. Automated temperature controls adjust the emitters to prevent damage to heat sensitive substrates during production, changeovers, and stoppages. For especially heat sensitive substrates such as films, a fan can provide additional cooling.

4. Controls – IR emitters are essentially instant on/off, so tying their operation into the press operation saves energy costs and prevents heat buildup in the press. For example, it is possible to use a PID controller to program the desired drying temperature alongside a pyrometer which monitors substrate temperatures to adjust the CIR emitters accordingly. Also, if no paper is being fed, the emitters can go to standby, or if there is a press stoppage, they can switch off.

What input power will be required?

This depends on the absorption characteristics of your material, its specific heat capacity, its mass, the temperature required and the speed of your process.

Is it possible to control the maximum temperature?

Yes, and we are able to deliver control units and power supplies together with the Infrared system.

How wide should the heated length of the infrared system be compared to the material width?

There are several factors such as the distance of the infrared system to the heated material and the temperature. We are able to calculate this data based on our experience and provide you with a complete solution.