The year 2013 witnessed an expansion of LED usage in UV curing applications with higher-power emitters enabling faster cure times across a variety of life science and industrial applications, writes BILL CORTELYOU, and component lifetimes have increased as well.
When people hear the terms “light-emitting diodes” or “LEDs,” most people think of visible LEDs for lighting applications. Indeed, LED technology is used increasingly throughout the world for indoor lighting, outdoor lighting, street lighting, automotive, and signage . But there are many other industrial applications such as curing (drying) and counterfeit detection. Ultraviolet (UV) LED technology for curing is one of the market segments that has gained worldwide acceptance and continues to grow. Let’s examine the state of UV curing technology and consider how well LEDs are fulfilling promises of taking over that space.
UV-LED curing refers to a technique that utilizes energy output from the LEDs in the UV spectrum to treat inks, coatings, adhesives, and other UV-curable materials. The energy generated by the UV light triggers a chain reaction resulting in polymerization of the material, thus hardening or curing the material (Fig. 1). For more background on UV-LED curing, see “UV LEDs ramp up the quiet side of the LED market” (links at the bottom of the article).
UV light instigates a chain reaction resulting in curing of materials such as inks or adhesives.
FIG. 1. UV light instigates a chain reaction resulting in curing of materials such as inks or adhesives.
Traditionally, mercury-based UV lamps have been utilized for curing, but now more energy-efficient and environmentally-friendly LED-based UV technology has proven a superior solution for many applications. LED curing technology uses semiconductor-based LEDs to project the UV light when an electric current is passed through them. When an LED is forward-biased, electrons are able to recombine with electron holes within the device, thus releasing energy in the form of photons.
The color of the light emitted or corresponding energy of the photon is determined by the energy gap of the semiconductor material. A number of companies that make LEDs used for general illumination also make LEDs that radiate in the UV spectrum.
Advancements in UV-LED curing
It is an accepted fact for many industries that LED lamps provide many advantages including lower energy consumption, longer lifetime, improved robustness, smaller form factor, and faster on / off switching. Those advantages are also important in curing applications.
UV-LED curing technology has advanced significantly in the past few years and is now readily available for a variety of applications in printing, coatings, and adhesives. There are many benefits driving companies to move toward acceptance of UV-LED technology such as higher productivity and a more environmentally-friendly solution, which more and more end customers are demanding. As manufacturers are developing UV-LED curing systems, knowing how the key sub-components work together will help in creating the optimum system and thereby reducing the overall environmental impact of the process and at the same time maintaining or improving productivity and product performance.
Application segments
Curing is a broad market with many application niches But let’s consider some of the major application segments.:
Printing:. The UV curing process has been in use in the printing industry for more than thirty years LED curing technology for UV printers is rapidly replacing older technology with compelling advantages of better economics, system capabilities, and environmental benefits UV-LED curing technology. is ideal for the UV curing of inks in digital inkjet, screen, flexographic, and other printing processes.
Coatings: A significant number of coatings are cured worldwide today with UV-LED sources in applications ranging from traditional materials such as flooring and cabinetry to advanced electronics Material development and long-term performance testing will further open markets in the areas of automotive, electronics. , residential, and commercial construction materials.
Adhesives: UV adhesives are a great tool in modern assembly and manufacturing processes with UV-LED electronic control and stability, ensuring excellent results in a wide variety of UV-LED adhesive applications from medical devices to the most advanced consumer electronics.
Snapshot of 2013
2013 was another year of strong growth in UV-LED adoption. In the last few years, there has been much discussion around the rate of adoption and usefulness for the wide range of UV curing applications. Essentially, the question has been “Will UV- LED curing technology fulfill its promise? “Well, the answer is yes! In fact, it has exceeded the promise and will continue its strong growth, accelerate, and open new UV curing markets.
The early concerns of output, lifetime, and cost have all been met with rapid technology and product improvement. Today, UV-LED curing technology meets a wide range of application requirements and is continuing to improve at a rapid pace. Lamps of 16 W / cm2, which cure at the highest of speed requirements, have been shipping in volume for more than two years Lamp manufacturers routinely quote lifetime expectations in excess of 20,000 hours of on-time -.. double what was quoted a few years ago Soon, leading manufacturers will be producing lamps promising even longer lifetimes — likely around 30,000 hours, matching or exceeding the life of various curing installations.
Nearly all UV-curable materials providers have UV-LED-curable chemistries along with aggressive technology and product roadmaps. Although the monochromatic nature of UV-LED lamps requires special consideration from the chemists, it has not been a long-term impediment as once thought .
One of the most exciting aspects of utilizing a UV-LED curing process is that it opens many new process possibilities with its precise electronic control of energy delivery. Many users have tailored their processes to achieve results unattainable through other means. Today there are many proprietary uses of energy control across varying applications.
Recent milestones
Consider the milestones reached in 2013. The Labelexpo Europe 2013 tradeshow reflected large-scale UV-LED adoption. The event validated the claims of rapid adoption of UV-LED curing. The show reported record-breaking attendance figures by attracting 31,795 visitors (up 11 % over 2011) from 158 countries (up from 123 in 2011) with nearly 600 exhibitors (up from 550 in 2011). Everywhere they looked, attendees saw UV-LED curing systems being implemented on machines. To UV LEDs’ traditional strength of digital inkjet were added rotary screen printing, area curing, offset, and flexographic printing.
Comparing Labelexpo 2013 to Labelexpo 2011 proves just how rapidly the industry has adopted the technology. More than 80 UV-LED curing lamps were installed on equipment at the 2013 show, up from 10 instances during the 2011 show for an 8x increase. Curing uses ranged from pinning to full cure and many of the printers were 100% UV-LED based.
Attracting the highest ever number of entrants in its history, the Label Industry Global Award for Innovation, sponsored by Label & Narrow Web, Labels & Labeling, and NarroWebTech magazines, was jointly won by Mark Andy and Flint Group Narrow Web. Flint Group was honored for its Ekocure UV-LED ink technology, which the judges described as providing improved cure response, cost and productivity savings, waste reduction, energy savings, and enhanced safety that will undoubtedly have a significant impact on the future of the label industry. Mark Andy was recognized for its complementary ProLED ink curing technology, which delivers high production rates and 50% energy savings.
More material formulation suppliers
At the advent of UV-LED curing, some ten years ago, very few types of inks, coatings, and adhesives were compatible with UV-LED technology. As Fig. 2 shows, the spectral energy distribution of UV LEDs is quite different from that of mercury lamps and indeed is in a much narrower band. That difference required new material formulations.

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