What is UV curing?
UV curing is a high-speed, solventless photochemical process that uses high-intensity electronic ultraviolet (UV) light to change inks, coatings, adhesives or other photo-reactive substances through polymerization into an instantly fixed-in-place solid. “Drying,” by contrast, solidifies chemistry through evaporation, oxidation or absorption. With UV curing, the cured substances become securely adhered to the substrate onto which they were applied, with adequate depth of cure without being tacky, sticky or flakey.
What are the types of UV curing?
Types of UV curing include spot curing, flood curing, hand-held curing and conveyor curing. UV curing systems use a variety of lamps as the UV light sources: mercury-based arc lamps which generate broad spectrum UV light; and light emitting diodes (LEDs) that emit only UVA energy. While UVC LEDs are an option, the power output and efficiency is much lower.
What is LED UV?
Light Emitting Diode (LED) is a semiconductor device that emits light when current flows through it. When attuned to the UV spectrum, LED technology can be effectively used for curing. Learn more here about LED UV Curing.
How is LED UV different from traditional UV?
Mercury arc (HG type) lamps are the original equipment for UV curing and are widely deployed as solutions for printing and other industrial manufacturing processes. While they work well, they have their downsides. Most significantly, they create substantial heat and consume a large amount of energy. They also produce ozone, which requires exhaust systems to maintain air quality. Mercury-arc bulbs must be disposed of at a cost and under regulatory scrutiny and have a long-term environmental impact. A mercury-arc UV lamp, or bulb, typically lasts about 1,500 hours.
LED-based UV curing provides all the advantages of traditional UV curing while adding solutions to many of the problems encountered with heat-set drying. They include instantaneous turn-on/turn-off, fast and uniform drying/curing, low heat emission, and low power consumption. Additionally, LED UV’s small-form factor makes it ideal for incorporating into processes or machinery with little available space. LEDs last approximately 20,000 hours on average.
What are the advantages of UV LED?
Instantaneous turn-on/turn-off, fast and uniform drying/curing, low heat emission, low power consumption, and small form factor.
What are the disadvantages of UV LED?
Limited irradiation intensity, cannot emit short-wave UV light, and shorter irradiation distances from lamphead to substrate.
Do LED UV lamps get hot?
No. The surface temperature of LED UV lamps is 122°F to 140°F (50°C to 60°C), whereas mercury lamps have surface temperatures exceeding 750°F (398°C). The low operating temperature of LED UV prevents damage to heat-sensitive products during the curing process.
How long do LED UV lamps last?
LED UV lamps average around 20,000 hours of operation, which is 10 times longer than arc UV curing lamps, which average a 1,000- to 2,000-hour life, making for more uptime and less maintenance and bulb replacements.
Where are the biggest trends happening in the LED Curing space?
We see it happening in the web offset side of the printing industry. See the video below for more info.
What happens after 20,000 operating hours?
The lamp will continue to work, with lower energy emission as single LED bulbs age. This does not mean the lamp needs to be replaced immediately; rather, the lamp can be adjusted to a higher intensity to adjust for the lost power.
What are the applications of LED UV in the printing industry?
The printing industry was one of the earliest adopters of HG UV and then LED UV curing for inks and coatings. This was especially true with sheetfed offset and narrow web flexo printers. LED UV curing is becoming increasingly standard for digital inkjet and web offset presses. , There is a growing movement of printers retrofitting production lines that have existing UV curing systems to LED UV.
The majority of UV-curable inkjet printers on the market use LED curing as their default curing technology as it has advanced to ensure faster curing and high-quality printing as well as improved production output.
For flexographic presses, LED UV’s ability to cure with cooler temperatures is widely adopted as a game changer for printing on thinner films and a wider range of label stocks. Inkjet LED UV curing leads the market in wide-format graphics primarily because of the ability to print on specialty substrates, and most narrow web presses are sold standard with LED UV curing as well.
What are the applications of LED UV outside of the printing industry?
LED UV light has moved into the mainstream in industrial manufacturing as the preferred process to instantaneously cure UV-light-reactive adhesives, coatings and finishes for superior bonding, sealing, coating and finishing on substrates of all kinds. Its applications include electronics, medical products, automotive and plastic parts, EV batteries, food and beverage, wood furniture, building products, aircraft/aerospace, and venue safety/germicide, aluminum cans, and many more. Read more about Industrial use cases here.
Is LED UV environmentally friendly?
LED UV lamps require specially formulated adhesives and inks, which are free of solvents, so LED UV curing eliminates the release of VOCs (volatile organic compounds), minimizing their environmental impact, along with reducing the amounts of materials used and waste produced.
Because LED UV emits UVA energy, the lamps do not generate ozone, which is a byproduct of many print curing processes that must be exhausted from the work area. LED UV lamps are also free of mercury, a toxic metal that is contained in arc UV lamps, which removes the need to safely handle and dispose of mercury arc bulb
The elimination of heat, ozone and mercury from press rooms by using LED-based UV makes them safer. LED UV also eliminates the costs generated by cooling air blowers and ozone extraction systems and the ambient noise and odor associated with other systems, further improving the work environment.
Lastly, LED consumes much less energy than arc mercury UV.
How can LED UV speed up production?
LED UV reacts with a photo initiator blend to deliver an instant cure, eliminating the drying process when compared to drying solvent-based inks and adhesives. Printed materials can come off the press and immediately go to trimming, binding, or other post-production steps.
An advantage of LED-based UV lamp heads is that they power on and off instantly, so they can be turned on and are immediately ready to cure, versus traditional arc-based lamps which remain on throughout production and require an initial warm-up period that slows production.
How can LED UV save energy and costs?
LED curing systems consume approximately 65% less energy than a similar sized mercury arc UV system. The power required to run LEDs is considerably lower than what is required to create the electrical arc in a UV bulb to produce enough heat to vaporize mercury and create UV light.
In addition to boosting output speed and capacity, the instant on/off process of LED UV substantially lowers the energy usage and stress on lamp bulbs that’s inherent with conventional “always-on” UV mercury lamp curing. LED UV also has no moving parts and eliminates the time spent servicing other parts such as ballasts, shutters, reflectors and fans that are standard in arc-based lamps.
Another benefit of LED UV curing is that it ensures stable output, versus UV arc bulbs that degrade over time. This removes the need for constant monitoring and pre-emptive bulb changing, leading to better process and quality control.
Taking it a step further, operators have the flexibility to program the exact UV energy needed for changing process needs to reduce product waste, expand production capabilities and most efficiently utilize production lines. It is also possible to turn off individual modules in multiple-unit installations to save energy without slowing production speed or compromising quality.
Additionally, lower-heat curing reduces electrical consumption by eliminating need with conventional ink presses for dryers, which in addition to their direct consumption of energy in the printing process, contribute to higher cooling costs in the printing plant. Mercury arc UV lamps produce high levels of heat that can require the use of chill rollers when using film substrates. These cooled rollers keep the heat from warping the film, but they require an energy-consuming chiller system to cool the water.
How do frequent starts and stops affect LED UV lamps?
Frequent start-ups and shut-downs do not shorten the lifespan of LED UV lamps; rather, operators can take advantage of the instant start-ups and shut-downs by turning off LED UV during downtime to extend the lifespan of the lamps.
How is LED UV powered?
LED UV is powered by direct current (DC).
Is there a difference between UV LED and conventional UV formulations?
The ingredients in conventional UV and LED UV formulations are very similar. The main difference is in the photo initiator blends. Conventional formulations contain mixtures that initiate curing for a broad range of mercury lamp frequencies, whereas LED emits a specific frequency and therefore requires a matching specific photo initiator to carry out a curing reaction. The most common wavelength for printing ink is 385nm.
Can LED UV cure 3D objects?
Yes, by placing lamps in different positions with specific energy dispersion, manufacturers can completely cure regularly shaped and irregularly shaped 3D objects using LED UV. LED lampheads with optics that extend the distance that UV light can travel without a steep drop in peak intensity or dose are most suited for curing dimensional objects.
What kind of maintenance do LED UV lamps need?
LED UV lamps require very little maintenance. Routine cleaning of the emissions window and air filters is standard. Periodically checking LED dies to measure the UV output will let press operators know when to begin turning up the power to make up for end-of-life performance drop-off.