Excelitas Technologies, a global technology provider focused on delivering customized photonic solutions, expands its OmniCure UV LED Curing product line with the introduction of the OmniCure AC8-HD (High Dose) Series of UV LED Curing Systems.
Offering higher optical power and enhanced performance in the same air-cooled mechanical enclosure as its AC8 and AC9 predecessors, the new AC8-HD delivers more than 50% dose with optical uniformity. Excelitas Technologies’ patented control technology for addressing individual UV LED modules enables an outstandingly tight irradiation across the UV emitting length, as well as between heads. Its robust light engine design also provides more protection and longevity of the LED modules. The new UV light source is designed for large area curing of inks, adhesives and coatings in medical, industrial, electronics manufacturing, wood coating, touch panel/display, solar panel, conformal coating, automotive and print applications.
The scalable architecture of the OmniCure AC8-HD allows for multiple heads to be adjoined for customization and flexibility, without compromising output uniformity. The commonly shared platform with the current large area product offerings allows customers to upgrade and support faster process speeds without any changes in mounting or control.
UV LED curing technology presents numerous opportunities for wide web applications. Although most applications on the market today are in digital inkjet, screen, narrow web flexographic and sheet-fed offset printing, and structural bonding, Phoseon Technology sees growing interest in UV LED for wide web applications.
UV LED laminating adhesives is an area of focus for Phoseon. The benefits of UV LED laminating include an immediate cure and a long pot life — also known as working life, or the period that chemicals remain usable when mixed. In addition, using laminating adhesives, as opposed to solvent-less adhesives, enables the laminated web to be slit, converted and filled immediately after the laminator with no controlled environment post-cure processing time requirements.
The wide web market currently uses traditional UV curing systems for protective varnish, silicone release and functional coatings, but businesses are starting to invest time and resources into developing UV LED solutions for their coating applications.
“Companies have started to integrate UV LED curing into their wide web coating lines because of the benefits and growing level of interest in the use of UV LED sources within this application space,” says Jennifer Heathcote, director of business development at Phoseon Technology. “While it is likely some applications may not yet be viable for LED today, there are several coating lines that are successfully being converted, and this trend is expected to grow in the coming years.”
In addition, wide web UV applications that were never achievable with conventional arc or microwave systems due to the large degree of heat transfer, are becoming possible with LED, thus expanding the total UV curing market.
Most of the UV LED formulation work over the past 10 years has been in the areas of inks, adhesives and over-protective varnishes. Many coatings companies are just now starting to evaluate UV LED curing systems for use in curing b-stage, functional, and hard coat chemistry.
“The fact that UV LED coating formulations are garnering attention suggests the latest improvements in the technology are making it increasingly viable — technically and economically — for use in wide web coatings applications,” Heathcote says. “UV equipment suppliers have achieved success in designing and producing UV LED curing systems in short head lengths, and these designs are rapidly being extended to longer lengths.”
Heathcote says that while there are upfront costs to begin using, or switching to, UV LED curing for wide web printing, companies often quickly recoup their investment. UV LED curing systems have no moving or consumable parts, virtually eliminating downtime for maintenance and repairs.
Consumers globally are using touchscreen displays every day in a growing array of electronics, from TV to smartphones to mobile gaming consoles to in-car navigation systems.
With heightened demand for touchscreens, electronic manufactures are increasingly turning to Phoseon Technology’s UV-LED curing for its many benefits in adhesives bonding applications.
Phoseon’s unique UV-LED curing provides a consistent and reliable process to assemble touchscreen displays, whether it be to bond a cover glass to a liquid crystal display (LCD) or an organic light emitting diode (OLED) screen, or curing adhesives on a smartphone’s ultra-thin border to prevent light leaking out through the edges. Phoseon’s solution also cures the encapsulation layer of the OLED display, which is an essential element to prevent the damage of organic elements from oxygen and moisture over its life time.
“Phoseon’s UV-LED technology is used to cure the UV adhesive, typically an acrylic formula, creating a strong and uniform bond between each touchscreen display layer,” said Rui Zhou, technical marketing engineer at Phoseon Technology. “The benefits of UV-LED curing include excellent optical properties such as better light transmission, vivid color display and reduced glare.”
Phoseon’s technology, which has been used commercially for more than 12 years, is a photopolymerization process that uses UV-LED light to rapidly change or “set” a liquid to a solid, usually within seconds, without the use of heat or solvents.
Zhou notes that UV-LED curing also offers electronics manufacturers high yield rates and productivity due to a safe, consistent and stable process without damaging heat-sensitive components. “In addition to its quick-drying capabilities, UV-LED curing creates very little heat that can damage sensitive components used in electronics — a critical element that cannot be replicated with other curing methods,” said Zhou.
“UV-LED curing has no moving parts, virtually eliminating down-time for maintenance and repairs,” said Zhou. “In addition, UV-LEDs last longer and require less energy to operate than traditional arc lamps or metal halide lamps, reducing operation costs and energy usage by up to 70 percent.”
Furthermore, because UV-LED curing does not contain mercury, which is used in arc lamps, it produces no ozone emissions or hazardous waste concerns, and are environmentally friendly and safe.
In addition to display bonding, Phoseon Technology’s UV-LED technology also is used in a wide range of other applications, such as narrow-web, wide-web and decorative printing, manufacturing wood, and curing wood and filament coatings.
For a number of years, UV technology has been a reliable technique for the curing of photo-reactive chemicals. In response to increasing production speeds and new applications, for instance in the field of 3D, UV lamp technology has also developed. Presently, a significant range of different systems are available, each specific to the particular application.
Users and providers of chemistry are continually developing new applications for UV curing. Their groundbreaking ideas mostly mean increasing demand on UV curing devices – where at times conventional UV technology has touched its technical limits. Therefore, within the recent years, a totally new branch of UV technology has formed: UV LEDs. This article offers the reader with an objective comparison between both technologies, UV and UV LED. It should help the user determine to what degree LEDs can provide a substitute to conventional UV solutions.
The operating technology of conventional UV lamps is based on plasma physics and optics, while UV LEDs are based on optics and semiconductor technology.
LEDs are founded on semiconductor technology. Specific wavelengths are directly discharged by the current input. The spectrum is a quasi-monochromatic radiation in distinct wavelengths, for example 365 nm, 385 nm or 405 nm.
UV LED curing makes its mark in the labels and packaging space.
From converters to their customers, environmentally friendly practices are profoundly affecting the labels and packaging space. One such way that the industry can save – both from sustainable and cost perspectives – involves ultraviolet (UV) light emitting diode (LED) curing.
UV curing technologies have been designed to instantly cure specially formulated inks, coatings and adhesives through polymerization. UV curing can include medium-pressure mercury arc and microwave-powered lamps, as well as LEDs.
According to Phoseon Technology, both arc and microwave curing technologies rely on the vaporization of mercury within a sealed quartz tube containing an inert gas mixture. Mercury emits ultraviolet light when vaporized, while electrodeless lamps utilize microwaves to vaporize the mercury.
Electrode lamps harness a high-voltage arc struck between two electrodes to achieve the same result. When the mercury is vaporized into an extremely high-temperature plasma gas, it emits a spectral output across UVA, UVB, UVC and UVV bands that can be manipulated by introducing metallic additives to the inside of the lamps. When the ink, adhesive or coating formulations are exposed to ultraviolet energy, they are crosslinked into a photopolymer.
UV LEDs, however, are solid-state semiconductors. Compared to conventional lamp technology, LEDs contain no moving parts or mercury plasma gas. In addition, they often operate at temperatures nearly 1/10th of those dealing with conventional lamps.
Martin Kugler, corporate communications for GEW, states that the electricity consumption of a typical mercury arc system is 2,005,000 kWh over a 10-year period. The equivalent UV LED system would consume 950,000 kWh, a reduction of over 50%. In the US, at approximately 12¢/kWh, this equals a savings of $126,000. This is based on an 18″ 8-lamp system with chiller, 60% uptime, two shifts per day and six days a week.
“Improvements in conventional reflector geometry have increased intensity at the web by capturing more UV energy and directing it in a true elliptical focus at the web, increasing curing power by 35%, thus reducing energy consumption,” notes Mark Hahn, VP of sales and marketing at AAA Press International. “UV LED curing technology has seen dramatic improvements in output power going from 16W/CM2 to over 30W/CM2, as well as significant improvements in optics design, allowing complete curing at higher line speeds.”
According to AMS Spectral UV – A Baldwin Technology Company, a mercury arc bulb can last 2,000 hours while the chips in an LED UV module can last 20,000 hours or more. This eliminates the need to frequently replace them as part of production maintenance.
“Over the first 20,000 hours of life, a typical LED system will lose about 15-20% of its UV output,” says Kugler. “After 20,000 hours, the LEDs will continue to work but output will degrade more quickly and the probability of LED failure increases. When a single LED fails, the user will not notice, as surrounding LEDs automatically increase in power to accommodate the loss. However, eventually, enough LEDs in a single area will fail and curing results will suffer.”
Stefanie DeBetta Langler, sales and customer service manager at Southern Lamps, explains that life expectancy and cost play a large role in a customer’s decision-making process regarding UV systems. “A typical LED system can cost $102,000 and the replacement lamp is $49,200. LED lamps are predicted to last 10 times as long as an arc lamp, but for 200 times the cost,” she says. “In comparison, a typical arc UV system will cost $28,500 and a lamp will be $258. The system is almost 1/4 of the cost and the lamps are 1/190th of the cost.”
The company says it is 100% focused on LED technology and providing rugged, high-performance products.
When it comes to label and packaging solutions, Phoseon Technology has the (LED) cure. Phoseon’s UV LED (light emitting diodes) curing products are currently being utilized in the printing, coating and adhesive industries, and the technologies are available to clients in custom configurations.
According to Phoseon, the company is 100% focused on LED technology–providing rugged, high-performance products for application specific solutions. Phoseon’s patented Semiconductor Light Matrix (SLM) technology encapsulates LEDs, arrays, optics and thermal management to ensure curing performance. Each of these four components is a strictly engineered system that provides maximum UV energy and superior performance while also increasing long-term robustness for demanding applications.
While arc and microwave curing technologies rely on the vaporization of mercury within a sealed quartz tube containing an inert gas mixture, LEDs are solid-state semiconductors. They contain no moving parts or mercury plasma gas and operate at temperatures that are often less than 1/10 the operating temperatures of conventional lamps. When connected to a DC power source, an electric current flows through the semiconductors, dropping electrons into a state of lower energy as they travel from the negative to the positive side of each discrete LED. The energy differential is released from the device in the form of a relatively monochromatic spectral distribution.
Commercially, UV LED technology has significant market adoption with longer UVA wavelengths (365, 385, 395 and 405 nm), and development work in shorter UVB and UVC bands continues, says Phoseon.
Phoseon describes UV LED curing sources as “high-tech electronics,” so the technology has blossomed with that of smartphones, laptops, tablets and televisions. During the technological boom, which has occurred between 2010 and 2017, UV LED sources have become more powerful, more efficient, more reliable and less expensive.
“UV LED curing technology has arrived,” the company says. “It is no longer an emerging technology but an enabling technology− one that is bringing a host of advanced capabilities to screen printing, flexographic and digital printing. These advances and new capabilities are helping industrial, graphics and specialty printing operations be more productive, versatile and energy efficient.”
Phoseon Technology believes it’s just a matter of time before UV LED cured low-migration inks, coatings and adhesives are widely adopted across global markets.
Low migration is a term used to describe the entire process of applying and curing specially formulated inks used in packaging such that there is minimal to no migration through the packaging materials and into the product. Low migration — also known as food safe process — is not exclusive to food packaging; it also extends to other products such as pharmaceuticals, cosmetics and pet products where uncured or migrating inks can negatively impact the product’s composition or odor.
Since 2004, EU Framework Regulation EC 1935/2004 requires low migration for all food packaging. While there are a variety of processes that can reduce migration levels, Phoseon Technology’s revolutionary UV-LED curing technology offers superior process stability and consistency, both top requirements for low-migration printing.
“The UV output of LED curing equipment is much more stable over time compared with conventional mercury based systems. This results in greater process control when used to crosslink inks, coatings and adhesives in low-migration processes,” said Jennifer Heathcote*, global business development manager at Phoseon Technology.
UV LED curing is becoming increasingly more viable for decorating applications spanning printed labels, flexible and shrink films, rigid containers, and carton and corrugated board. In addition to its quick-drying capabilities, UV LED curing creates less heat transfer to the substrate, thereby, eliminating or significantly reducing any damage to the print surface.
“That’s a critical benefit, especially when printing on heat-sensitive plastic films often used in food packaging,” said Heathcote.
Heathcote notes that while there are upfront costs to switch to UV LED curing for food safe process printing, companies often quickly recoup their investment. UV LED curing technology has no moving or consumable parts which significantly reduces down-time for maintenance and repairs. UV LED systems last longer and can reduce energy consumption by up to 70 percent compared with traditional arc lamps. In addition, UV LED curing does not contain mercury, which is used in conventional lamps, making for a safer environment and workplace.
Artist? Scientist? Glass artist Sidney Hutter, of Auburndale, Massachusetts, considers himself to be both.
“I use science to make my art,” he said. “The pieces are sculpture, 3D and a continually changing sculpture depending on the viewer’s angle is what I wanted. One of the things people who collect my work say is that, depending on the angle, you can look right through the piece and not see any of the color or adhesive. Change the angle of view by 20 or 30 degrees, and you see something different. It depends on the angle perspective from where the viewer is standing.”
Hutter, who has been working with glass since 1974, blends art with the science related to glass properties, use of dyes and pigments, coatings and UV cure. As a graduate student, he was forced to change the way he approached glass art after a fire in the studio eliminated his ability to blow glass, so he began gluing glass pieces together.
“I started using UV-cured adhesives in the early ’80s and, prior to that, used anaerobic adhesive,” he explained. “The technology has continually evolved over the years.”
Hutter began curing adhesive under a fluorescent black light, but the low UV output resulted in a long cure time. In addition, it would only cure a single layer. He developed a pre- and post-cure system that allowed for the spot cure of multiple layers with a low-intensity UV lamp, then cleaning the piece and full curing with a higher intensity UV.
“I began researching LED use as the technology developed,” he continued. “The change in the last several years is amazing. There’s no heat, so it makes the working environment much more comfortable, and the bulbs last much longer. The disadvantage is that it is spectrum-specific, and I don’t have a spectrometer to figure out the cure.
“I’ve been a member of RadTech for over 20 years,” he continued, “but I’m only as technical as I need to be to get the work done. I have to have an understanding of the technology I’m using. Some industry professionals find it intriguing that I use the technology in that way. Now I’ve been at it so long that people ask me technical questions related to my art. It’s a critical part of what I do.
As technology developed in the early ’90s, more options for glass were available, along with the ability to color the adhesives. “Until that point,” Hutter wrote, “the only color in my work came from the limited colored commercial plate glass available, which I laminated with clear adhesive, or opaque antique architectural glass, which would not transmit light. The ability to add color into the adhesive between the layers of glass opened up many possibilities.
“This advancement led to new series of work. The interior of the pieces was becoming as compelling as the exterior, and I began cutting and polishing ‘windows’ into my vessels, allowing a look inside.”
The most important fields in which the use of UV-LED technology has increased are wood coatings and printing inks. We spoke to Frédéric Taché and Charles Bourrousse of Sartomer about the current state of the art in UV-LED technology and UV-curable adhesives.
How prevalent is UV-LED technology? Frédéric Taché: Today, the perceived advantages of UV-LED, including increased productivity, higher quality and a more environmentally friendly technology, have enabled UV-LED curing to play a major, if not dominant, role in many UV-curing applications, as well as to convert traditional processes to UV. The most important fields in which the use of UV-LED technology has increased are wood coatings and printing inks – even to the extent that some lines are now “full” LED. More recently, the development and marketing of low-migration systems specifically developed for use with LED has led to greater acceptance across all sectors of the coatings and printing inks industry in the EU wherever indirect food contact is critical.
Charles Bourrousse: Moreover, the reduction in heat generated during curing has paved the way for the use of thin-film, heat-sensitive plastic substrates. This has facilitated rapid development in flexible packaging applications. Further progress in UV-LED will be based on the development of new wavelength lamps and/or better-adapted photoinitiator packages. As a key supplier to the UV industry, Sartomer continues to develop and recommend market-leading solutions for the highest surface cure performance.
The UV LED community is increasing its number of members in Europe
In just a few years, the UV LED Community has reached over 100 members. This shows the growing interest and the acceptance of UV LED technology in a wide range of applications. Now uvledcommunity.org is getting some additional support in Europe to increase its reach and to promote the adoption of UV LED technology.
Members who join the Community are key players in advocating for of UV LED in various fields. Members include suppliers of materials, resins, photo-initiators, adhesives, inks, coatings, equipment, measurement and end-systems. These companies have the common goal of accelerating the adoption of the LED curing technology through education and knowledge sharing.
Following the rapid growth of UV LED solutions in Europe, the UV LED Community will now be supported locally by Jochen Christiaens, European site editor. Jochen will be assisting local suppliers and manufacturers to promote the community site and grow the number of new members (membership is free to qualified suppliers and end users of LED technology).
The Community website is an educational forum that enables participants to share their knowledge of UV LED curing technologies, applications and chemistry, as well as to exchange news and information.
The Community has two primary goals:
To provide a forum for UV LED curing conversations.
To foster communication between suppliers and consumers of UV LED solutions.
“As an advocate of UV LED curing technology for years, I have been involved in the development of various inkjet printing projects for over 15 years. It is a great pleasure and honor to be part of educating the market and support the UV LED technology, and help growing the community web site,” said European site editor Jochen Christiaens.
To date, we have posted over 200 industry articles on LED curing, and we are looking forward to our members to contributing to the unique content of the UV LED Community by providing news, technical articles, and in joining the active discussions about UV LED applications.”