Technology declared dead is alive and kicking

UV technology has known only one state since 1970: continuous growth. The same applies to the printing industry, where UV curing now occupies an estimated market share of 90% in narrow web printing or nearly 30% in offset printing. In the last decade, media attention has almost exclusively concentrated on the LED UV variant. As a consequence, conventional UV systems are often viewed as a relic of outdated technology, even though they continue to dominate the market. However, closer inspection shows that classic UV lamps are actually undergoing something of a revival, and their use is steadily expanding in several areas. This article examines why that is the case and what it has to do with the ongoing coronavirus pandemic.

The applications of UV technology have two major focuses. One is the UV curing of inks, varnishes, adhesives and other coatings; the other is disinfection. Both segments are growth markets in which both classic UV systems, for example with medium-pressure mercury vapour lamps, and LED UV systems are used.

Classic UV lamps continue to play a key role

The various application areas of UV technology are divided into many different sub-markets. These can vary greatly in terms of their respective applications. In practice, the application determines which technology is used. That explains why one or the other UV system dominates, depending on the market segment. As both variants offer specific advantages, they are each experiencing continuous growth, independently of one another. For example, according to a study by Yole Développement SA, Lyon, the number of lamps used for UV curing on the European market increased by approx. 20% between 2015 and 2018.

For the future, the organisation predicts further growth of more than 40% in value terms for conventional UV lamps from 2019 to 2024, and an increase of almost 50% on the UV LED market (see Figure 1). The increase in UV LED systems can be explained in particular by the rapid expansion of UVC-based water disinfection with an annual growth rate of 26% (see Figure 2). In the UV curing market segment, which includes polymerisation of inks and varnishes in printing processes such as offset, flexographic, screen and inkjet printing, the use of LED UV systems is expected to increase at a significantly slower rate of 5% annually.

Consequently, conventional UV lamps will retain their key role in the UV curing market for the foreseeable future. Typical applications for UV curing range from commercial printing and all kinds of labels and packaging, to credit cards and security features on bank notes. This category also includes the UV curing of surface coatings in the furniture and flooring industry, printed circuit boards in the electronics industry, products such as spectacle lenses and contact lenses in the optical industry, as well as CDs and DVDs and functional coatings in the automotive industry.

Reliable disinfection without chemicals using UV light

As well as in the curing of various coatings, UV lamps have long been commonplace in other application areas. One example is the chemical-free disinfection of drinking water using UV devices, for which public water supplies have opted with increasingly frequency within the last ten years. The company eta plus electronic gmbh in Nürtingen, is one of them. The company produces UV lamps and electronic ballast devices which are used for the disinfection of drinking water, wastewater, ship’s ballast water, process water, water in fish farming, pools in leisure parks or swimming pools and water for the food and beverage industry. Prominent examples are the municipal water treatment plants of Paris, San Francisco and Basel.

The UV light of the classic lamp systems deactivates the DNA of harmful germs. Short-wave light is particularly effective in UVC disinfection as it inhibits cell division and thus the multiplication of microorganisms. A further advantage is that the process neither requires chemicals, nor does it produce unwanted or even harmful by-products. Pathogens that are resistant to chlorine, for example, are also reliably killed off. Natural taste, odour, colour and pH values of the water are not affected by the UV light treatment.

Considering all these advantages, it’s no surprise that demand for UV systems in sterilisation and disinfection has been increasing for years. As shown in Figure 2, this is yet another future growth market for LED UV technology. Currently, however, companies are more frequently opting for systems using conventional UV lamps, because they offer a comparably higher power output – especially in the frequently used wavelength range of 254 nm – and are therefore more economic.

Air disinfection with UVPE

UV light can not only be used to disinfect water, but surfaces and air streams too. As hospital-specific germs become increasingly resistant to antibiotics, the currently still widespread use of disinfectants in hospitals may increasingly be replaced by UV disinfection, as this eliminates the possibility of mutations leading to antibiotic resistance.

In this context, the company Virobuster International GmbH in Windhagen, developed the patented ultraviolet pathogen elimination (UVPE) process. Devices equipped with the technology, such as the Steritube product range, enable the efficient elimination of harmful microorganisms. Steritube systems, which are distributed together with IST Metz, have been used for air disinfection in the medical industry for a longer time, and now also the food industry. They can easily be integrated in existing ventilation systems and deactivate microorganisms in a single process.

Portable device for disinfection of surfaces

During the times of the coronavirus pandemic, these technologies have naturally been the subject of increased interest. Since the global spread of the SARS-Cov2 virus, the company Integration Technologie Ltd. (ITL) has accelerated an existing product development and designed a portable disinfection system which is being marketed under the name SubZero RS Virus Sanitiser. It is specially designed for professional applications and requires suitable personal protective equipment to be worn during use. Although in recent years ITL has primarily developed LED technologies, when it comes to the compact handheld device, the company has drawn on its tried-and-tested SubZero range, featuring a classic UVC lamp system, which was launched in the printing industry in 2005. “We were developing a portable system that was intended for use in an industrial environment”, explains Managing Director Simon Roberts. “Due to the large-scale spread of the coronavirus, however, we quickly switched our priorities to medical applications. The use of UV lamps provides sufficient energy to reliable deactivate microorganisms like the coronavirus.” Disinfection with ultraviolet light is an economic and environmentally friendly process and is particularly suitable for ambulances and hospitals, public transport, schools, offices, hotel rooms and much more.

Suitable inks and varnishes available for UV lamps

In most areas of the printing industry, UV lamps have become an integral technology, despite the fact that their impending demise has been predicted for years. A major reason for this is that suitable inks and varnishes for the traditional lamp systems are widely and reliably available. In contrast, the narrow emission spectrum of LED systems is a considerable disadvantage in the formulation of suitable printing inks and varnishes. The development of suitable inks and varnishes is particularly critical in low-migration applications. In this context, the broad emission spectrum of UV lamps offers clear advantages in achieving safe and reliable curing in the printing of food packaging.

However, the formulation of food-compliant LED UV ink systems is not only challenging because of the narrow spectrum. It is also impeded by legal regulations, such as the European chemical regulation (REACH), as in recent years, certain chemicals have been prohibited, reducing the available selection of raw materials (e.g. photoinitiators).

Use of mercury in a controlled cycle

Ecologically speaking, being solvent-free is one of the primary advantages of UV systems. However, UV lamps have the disadvantage that as gas discharge lamps, they are dependent on the use of mercury vapour as a filling gas. The use of hazardous substances like mercury is regulated by EU Directive 2011/65/EU – also known as RoHS (Restriction of Hazardous Substances). The directive contains a list of exemptions, which includes discharge lamps for special applications. The RoHS is intended to prevent hazardous substances from entering the environment. The biggest emissions are created by the generation of electricity using coal or waste incineration, as well as by gold mining. While a typical coal power plant releases many tons of mercury into the environment, despite measures to reduce emissions, all the lamps used for UV curing in Europe are estimated to contain approx. 150 kg of mercury.

There is a high probability that the described exemptions for mercury vapour lamps will remain in place in future, particularly for applications in UV curing and UV disinfection. For this reason, the aforementioned market study by Yole Développement SA supposes that the “Minamata Convention”, which was agreed by the United Nations in 2013 to reduce the use of mercury, will initially have no significant effect on the market development of conventional UV lamps.

Another factor to take into account is that virtually all mercury from UV lamps is sent for recycling. By doing so, the industry also complies with the WEEE Directive 2012/19/EU (Waste Electrical and Electronic Equipment). In Germany, for example, certified recycling companies are responsible for the collection and processing of used UV lamps. Careful recycling makes ecological sense in any case, as the lamps contain valuable raw materials and electronic components. LED systems too should be effectively recycled at the end of their product lifespan. After all, LEDs are also subject to the WEEE directive and it’s essential that suitable recycling methods are established, especially for the recovery of expensive raw materials like rare earths or indium and gallium from LEDs.

Good future prospects for proven lamp technologies

In everyday practice, UV lamps have proven themselves useful over many years, thanks to their many positive attributes. They offer extremely high power density and are economic to operate. In many market segments, users are increasingly looking for systems that reliably meet their respective requirements. As well as classic UV lamps, this trend is also benefiting other well-known systems, such as excimer lamps, which are currently enjoying a significant revival. The future outlook for proven technologies like UV lamps is decidedly positive. They offer so many advantages for established areas of application, as well as for emerging new fields, that they hold a great deal of potential for future growth.