UV LED Curing Technology Goes Mainstream

UV LED Curing: A rapid technology adoption across a broad array of industries.

In the approximately 10 years since ultra‐violet light‐emitting‐diode (UV LED) curing lamps appeared in the market, there have been significant technological advances in LED efficiency and curing lamp performance. The initial challenges have been met and overcome allowing rapid technology adoption across a broad array of industries.

UV LED Benefits 

While one might argue with any specific cited advantage of the UV LED lamps, the total of the advantages of UV LED curing lamps is clear. They provide:
1. New capabilities to end‐users and machine‐builders by allowing tighter control over the curing process, especially on heat‐sensitive substrates.
2. Operating economics include reductions through energy efficiency, low maintenance and long lifetimes.
3. Environmental advantages by being ozone and mercury free as well as improving workplace safety.

Successful Markets

Printing: First inkjet, then screen and now flexographic. Typical of many new technologies there needed to be a “starting‐point” where a specific benefit of the new technology “out‐ weighs” the traditional method. UV inkjet applications (particularly on heat‐sensitive substrates) were an early and clear success for the UV LED curing lamps. Continued development has enabled the UV LED based curing lamp to be the best overall solution for UV inkjet curing applications. It’s very likely that within the next few years the vast majority of UV inkjet printers will utilize LED-curing lamps. Other ink‐curing applications where close proximity of the lamp to the substrate is easily achieved, such as UV flexographic printing and UV screen printing, will quickly follow. UV LED curing is also used or envisioned in curing of functional materials in many new applications in industrial inkjet.

Today, UV LEDs are finally taking their place as a mainstream curing technology. Rapid technological advancements being made in all areas of printing, from digital inkjet to flexography and even offset, demonstrate the far-reaching potential and growing acceptance of UV LED curing.

End users are increasingly asking equipment manufacturers for LED options, and the market‐leading vendors are responding. Confronted with such exciting and rapidly evolving technology, system builders and end users are closely monitoring the ever‐changing UV LED curing landscape.

Coatings: Wood flooring, cabinetry and advanced electronics.

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: Medical devices and consumer electronics.

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.

UV LEDs are finally taking their place as a mainstream curing technology. Rapid technological advancements being made in all areas of printing, from digital inkjet to flexography and even offset, demonstrate the far-reaching potential and growing acceptance of UV LED curing.

UV LED Lamps

UV LED lamps are available in air‐cooled and water‐cooled versions. Historically, the primary reason for water‐cooling was to efficiently cool the LEDs, so they could operate reliably at high power outputs. As air‐cooled technology and diode efficiency improved, air‐cooled UV LED lamps are now capable of curing materials at high speeds once reserved for water‐cooled systems. Assuming that the power requirement can be met with either air‐cooled or water‐cooled lamps there are a number of considerations when choosing between the two:

• Air‐Cooled: larger for most configurations, airflow — intake and exhaust, air filtering, cooling efficiency and lamp output dependent on the ambient.
• Water‐cooled: Requires water‐cooler and associated plumbing, typically small in relation to the power produced, no airflow considerations or air‐filtration required, precise output control based upon cooler/ chiller control.

Control

A tremendous advantage of LED based lamps is that they are solid‐state devices and can be rapidly and precisely controlled. Delivery of a specific dose or intensity is easily achieved. With response times in the range of milliseconds, the lamp is typically turned‐ off when energy isn’t needed, resulting in power savings and reduced stray light. UV LED lamps provide separate controllers, while other units have the control capability fully‐integrated within the lamp itself. This advanced control capability is being used today in all areas of curing to achieve unique matte or gloss finished in inks and other unique properties in coatings and adhesives previously unavailable.

Wavelength

UV-A

UV LED curing lamps are available today in wavelengths from 365 nanometer to 395 nanometers and higher. 395 nanometer lamps are the most popular due to their efficiency, power and price‐effectiveness. The technology and manufacturing methods of diodes become more challenging, as the wavelength gets shorter. The efficiency “penalty” for 385 nanometers, compared to 395 nanometers is about 10 percent and for 365 nanometers the diodes can be as much as 50 percent less efficient and more costly. All UV diodes have become more efficient over time but the relative efficiency and cost improvements have favored the 395 nanometer diode due to its popularity. The 365 nanometer is sometimes used in specific applications where users are reluctant to change their formulations and the lower wavelength meets the requirements. Diode emission while labeled “monochromatic” is actually a relatively narrow distribution of wavelengths normally distributed around the “peak” with a practical spread of approximately 20 nanometers.