UV LED lamps: Technological innovation

Increasingly, we see how users within the printing and graphics industry are betting on incorporating UV LED lamp technology in their drying (polymerization) and curing processes.

Traditionally, mercury arc lamps have been used for this drying process, but nowadays UV-Led technology is consolidated as a more efficient technology, especially from the energy point of view, and it has proved to be an excellent solution for the industry.

In this article we tell you how this drying technique works, we present you the UV Leds of our represented brand Lrandae and we ask some experts of the printing sector about the use of this technology.

What is UV-Led Drying?

UV-Led drying is a technique that uses the energy generated by light diodes in the violet spectrum to treat inks, varnishes, adhesives and other materials compatible with this drying technology.

How does UV-Led work?

The energy generated by the UV light causes a chemical reaction. The ink remains liquid (monomer) until it is exposed to light. Once this ink is exposed to light, its molecules begin to intertwine and end up forming a polymer, i.e. a solid.

In this way, the ink is liquid when it is in the print heads, avoiding possible obstructions, but once it is printed on the support, it can be quickly fixed without the need to apply special surface coatings or thermal drying. After this drying process, UV inks are insoluble, so we can print multiple layers to create images with textures, volume, etc.

Advantages of UV-Led drying

Low energy consumption

A UV-Led unit radiates approximately 18 to 25 W / cm2 and additionally consumes the liquid cooling of the LEDs and the output control circuit. Compared to conventional drying lamps, the latter consume a total of approximately 5KW/lamp for a width of 420 mm. In terms of exposure, the measured consumption in light energy is 20 w / cm2 against 120 w/ cm2 of power of the conventional system.

In addition, it is necessary to consider that the UV-Led units turn on and off instantly, so the consumption is optimized. In contrast to the conventional drying system, the lamps are always on with maintenance voltage and when they are turned off it is necessary to let them cool down completely before using them again.

Longer lifetime

The lifetime of a UV-Led unit is approximately 20,000 – 25,000 hours, depending on heat dissipation. For example, if a UV-Led drying unit works 16h/day under the minimum estimated life span (20,000 hours), this UV-Led lamp would last 1,250 days, i.e. about 5 years. If we compare it with the life of a conventional drying lamp, it usually has a life of approximately 1,000 -1,500 hours. In this case, with the lampworking at 8 hours a day, it will have to be replaced after 125 days, that is, approximately 6 months from its installation.

Does not generate ozone

Due to its composition, this technology does not generate ozone, so no special ventilation is needed for its elimination, with the added advantage of not having thermal leaks through these ventilation systems.

Adjustable light intensity

The volume of light can be constantly controlled between zero and the maximum power output. The current can be varied or the individual LEDs can be adjusted selectively (per lamp) so that the right intensity is always available. With conventional lamps, the electrical current must always be kept above a fixed value in order to maintain the discharge, although the working power is also adjustable.

The material does not overheat

With the UV-Led, the temperature of the chip is cooled by water so that the material (coil) is not heated. In addition, by emitting UV light with a peak of 385-395 nm, printers incorporating this technology can handle different materials that would be highly vulnerable to heat if conventional drying lamps were used.

Lrandae drying solutions: UV LED

In Zonten we represent and distribute the brand Lrandae, a leading company in the production of UV LED drying processes.

Some of the main features of Lrandae UV drying systems:

• Efficient, easy to use and economical equipment.
• They have a long life span of over 15,000h and have a speed of up to 200M/min, monitoring and multiple protection systems to ensure a safe, flawless and efficient process.
• It has a highly integrated chip. It emits a high intensity of light, up to 40W/cm2. It ensures instantaneous switching, without preheating and continuous regulation.
• It does not generate ozone emissions or harmful gases. Allows energy savings and is responsible for the environment.
• It has a cold light source so the increase in temperature of the material is very low.

What do our experts think?

We asked industry experts who have first-hand knowledge of UV LED technology:

What is the current status of UV LED inks compared to conventional UV inks? What is expected in the future?

As far as standard products are concerned, the portfolios of the two technologies are identical. That is, four-colour and direct inks are comparable in intensity and resistance, both physical and chemical, but much more reliable in terms of polymerization capacity LEDs than the standard. This is due to the fact that the wavelength spectrum of LEDs is much narrower (385 nanometers) than that of conventional UV (100 to 400 nanometers).

The standard LED varnishes are also at the same level as the UV varnishes, but special varnishes (relay type, etc.) cannot yet be compared with the results of current UV varnishes. The same happens with metallized products and other specialities (thermochromic, etc.).

For the future, it is clear. The LED is here to stay. All are advantages, both at the economic level (savings in energy consumption and consumables), as sustainability (De-inkability) and food and pharmaceutical safety (Low Migration).

Ferran Campos​, ​Siegwerk ​Sales Manager Sheetfed & Narrow Web Spain.

Is it cost-effective to install UV LEDs instead of conventional UV today?

Currently, UV conventional technology still covers most applications, but increasingly, we see how UV led technology is much more cost-effective. For example, we recommend in configuring the semi-rotary offset printers with UV led dryers for four-colour offset and flexography for the rest of the printing units, such as screen printing, to keep the conventional UV dryers.

In flexo UV the predominant technology today is conventional UV. I would recommend UV led in case the printer wants to specialize in plastic materials in which it has been demonstrated to have better results in drying and anchoring at high speeds.

Enric Vela​, Maquinaria ​Esagraf ​. Sales Director. 

What is the main advantage of LED technology over filmic and adhesive materials?

One of the main factors at the time of printing that affects filmic materials is heat. The glass surface of the conventional lamp reaches very high temperatures. It not only emits UV light but also visible light, infrared light and far-infrared radiation, to the extent that certain adhesive materials can overheat and suffer distortion. Polypropylenes and Polyethylenes and co-extrusions are mainly affected.

In this same line, the effects of heat on adhesives, especially hotmelt, are also added. Due to their morphology, these are sensitive to heat, producing “bleeding” at the time of converting, and especially adhesive materials that require high adhesive weights due to the type of application and substrate on which the labels are applied. In order to have an adequate anchorage and drying of the inks to the current UV lamps, the manufacturers of self-adhesive materials have been forced to develop special top coatings to alleviate the market demands in terms of drying and effect of the inks on the different materials.

In short, LED technology is attractive for materials and printers because of its almost instantaneous drying properties that eliminate the negative effect on materials, in addition to its ability to adhere to a wide range of papers and films.

Jordi Pérez​, ​Ritrama​, Sales Director

Subsidies for energy saving

Some companies take into account in their investment decisions the factor ”energy-saving”. In Spain, there is currently a package of 308 million euros from the IDAE (Institute for the Diversification and Saving of Energy) and it can be very interesting to apply for a non-refundable subsidy for additional investment in machinery and equipment provided that it can be demonstrated that the energy-saving allows the investment to be recovered in a reasonable time. If you are interested in us helping you to prepare a budget and report to benefit from these energy-saving subsidies and you want to receive more information ask our commercial team.