With ongoing advances in LED UV technology, use of LED (light-emitting diodes) for UV (ultraviolet) curing in printing, coating, and bonding processes has become increasingly visible throughout the industry. UV LEDs have overcome many of the technical and economic obstacles that initially prevented wider commercial acceptance.
With the launch of GEW’s hybrid ArcLED UV curing system, barriers to adoption have now been further lowered. Within an ArcLED system, users are able to operate full hybrid UV curing, working with both mercury arc and LED lamp technology on the same press.
Whilst you can find out more about our LED and mercury arc products in our products section, we aim to answer the most common questions and misconceptions about LED here:
Question: Which applications get the best results with LED UV?
Answer: Printing inks, laminating and pressure-sensitive adhesives, wood fillers, and nitrogen inerted fibreoptic coatings are all ideally suited to being cured with UV LED. Viable UV LED printing methods include digital inkjet, screen, pad, flexo, letterpress, offset, and gravure.
White and highly pigmented inks are most suitable for LED curing. Longer UVA wavelengths and greater intensities penetrate through films and densely pigmented formulations better than mercury vapour lamps. In the special case of white inks, titanium dioxide (TiO2) additives absorb all wavelengths below 380 nm. UV LEDs emitting at 395 nm evade TiO2 particles in white inks which enables more UV light to be absorbed by photoinitiators.
Question: Is there a difference between LED and ordinary UV formulations?
Answer: UV LED and conventional UV formulations do contain many similar ingredients. However, a decisive category of the formula, the photoinitiator blend, is often significantly different. This is the chemical component that responds to light. Different photoinitiators react to different wavelengths. For LED technology to deliver speed and full cure, formulations must include photoinitiators that react to longer UVA wavelengths. As a result, conventionally formulated UV chemistry should not be cured with UV LED and must be reformulated.
While some LED formulated inks & coatings can only be used with LED, many are being designed as dual cure. Dual cure versions are specifically formulated for LED but will also work with mercury lamps. Using dual cure inks, coatings, and adhesives helps reduce SKUs and eases the transition to LED.
Question: What is the energy-saving with UV LED?
Answer: LED energy savings varies by system, integration, and means of operation. GEW encourages companies to contact us for a proper assessment and analysis based on individual circumstances.
A recent ROI analysis performed on a 45cm, 8 lamp system running two 8-hour shifts per day, 5-days a week, with a 60% duty cycle resulted in a savings of 16,000 GBP per annum. This is 160,000 GBP over 10 years in both energy and operation costs. This delivers approximately 7 tonnes of CO2 elimination and 46% total energy savings when compared to the most energy-efficient mercury arc systems (E2C) in the market.
However, against older and less efficient conventional UV systems, UV LED systems can often deliver in excess of 75% energy reduction.
Question: Do I need a different power supply for UV LED?
Answer: UV LED lamps are powered by direct current (DC) whereas UV arc lamps use alternating current (AC). Therefore typically a different power supply is required.
However, RHINO ArcLED hybrid power supplies from GEW can supply both; automatically recognising the type of cassette and switching to the correct power output. This means both LED UV lampheads and conventional mercury arc lamps can be used with one single power supply and operated with from the same touch control panel.
Question: Does LED UV work with everything?
Answer: While the entire portfolio of UV chemistry has not yet been reformulated for LED, the list of offerings continues to expand. Printing inks and laminating adhesives work well with LED. Unsupported films, shrink sleeves, and many delicate, heat-sensitive materials are also more easily processed with LED due to reduced thermal transfer. Varnishes, spot colours, and low migration formulations, however, still generally achieve better cure with arc lamps. Protective coatings also benefit from arc lamps as short UVC wavelengths deliver the best surface hardness.
The situation is constantly improving and the latest information should be sought from GEW before a decision is made.
Question: Do frequent starts and stops reduce the durability of LEDs?
Answer: No. Frequent on/off switching does not reduce the life of UV LEDs nor impact their durability. To the contrary, turning LEDs off when not needed extends the life of the system. During stand-by and line stops, UV LEDs should always be switched completely off. When LEDs are not emitting, they are not degrading.
Question: What happens after 20,000 hours?
Answer: Over the first 20,000 hours of emission, a typical LED system gradually loses 10-15% of its output capability. After 20,000 hours, the LEDs will continue to emit UV energy, but output will increasingly degrade making the probability of LED failure greater. When a single LED fails, the user will not notice, as surrounding LEDs automatically increase in power to accommodate any losses. When enough LEDs in a single area fail, curing suffers. At this point, users can either replace the failed LED module or replace the entire assembly to ensure uniformity of output across the curing width.
Question: Is LED UV more expensive?
Answer: CapEx and operating costs vary depending on the UV system, the integration, the formulation, and the needs of the application. In some instances, UV LED is more expensive. In others, it is comparable or even less expensive. GEW encourages companies to contact us for a proper assessment and ROI analysis based on individual circumstances.
Currently, for cure widths greater than 620mm (24”), the cost of a GEW LeoLED system is comparable to, and often less than, that of an arc system. LeoLED also eliminates the need for air extraction, ozone removal, and conditioned make-up air while achieving production speed targets, producing quality product, and capitalizing on energy benefits inherent in LED technology.
Question: How do I decide whether I need LED UV?
Answer: LED UV should be chosen based on three criteria: suitability for the process, availability of formulations, and the ability to achieve productivity gains. For additional guidance and information, please speak with your local GEW representative about the specifics of your application.
Whilst we have tried to answer the most common questions here, we welcome customers contacting us directly to ask any pertinent questions that they have around the subject, that have not been covered here.
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