UV-LED curing units have become more efficient in delivering higher energy to the media, driving the engineering and implementation of environmentally clean, energy efficient, and compact curing units that increase throughput and support flexibility in a variety of production environments.
By Richa Anand
UV-LED curing refers to a technique that uses energy output from light-emitting diodes (LEDs) in the ultraviolet (UV) spectrum to treat inks, coatings, adhesives, and other UV-curable materials. The energy generated by the ultraviolet light triggers the chain reaction, resulting in polymerization of the material and the hardening (or curing) of the material.
Traditionally, mercury-based UV lamps have been used for curing, but now more energy efficient and environmentally friendly LED-based UV technology has proven a superior solution in the printing industry. LED curing technology uses semiconductor-based LEDs to project 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.
LED lamps are recognized for their lower energy consumption, longer lifetime, improved robustness, smaller form factor, and faster on/off switching. But how do they work?
There are three key components of a UV-LED curing system that, when optimized, provide an economically advantageous, high-throughput solution to the printing industry: materials (inks) that can absorb energy in the UV spectrum to undergo polymerization process; LED curing lamps that provide energy in the UV spectrum of the spectrum; and a printing system in which a UV-LED lamp is integrated to cure material that passes underneath it. These elements together provide a long-term, sustainable printing method through green technology, eliminating ozone emissions and lowering energy consumption.
UV LEDs have a narrow spectral output centered on a specific wavelength, ±5 nm. LEDs are solid-state devices and can be built with diodes of various wavelengths, including—but not limited to—395, 365, 385, 405, and 410 nm, unlike the broad spectrum of wavelength output by Hg-based lamps. This monochromatic distribution (Figure 1) requires new chemical formulations to ensure proper curing of UV inks and coatings. Currently, the most popular wavelength is 395 nm, with 365 nm being used in specific applications.
UV-LED curing lamps consist of multiple sub-components that, when combined optimally, can drive system performance. Key components of the UV LED light source can be summarized in four major categories.
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