The advantages of UV LED light curing over the traditional mercury lamp have been pushing its growth.
Explosive Growth Recently
LED lighting technology, because of its low energy consumption and long life, has been eating up the competition while being rolled out with an explosive future trend playing out. Research from Gartner, Inc. says that Smart LED lighting has the potential to reduce energy costs by 90 percent. Internet of Things (IoT) architectures are driving the technology which will grow from 46 million installed units in 2015 to 2.5 + billion units by 2020.
Smart LED lighting is defined as a lighting system connected to a network for monitoring and control from a centralized system or from the cloud. We can see the trend to LED lighting ourselves as close as in replacement home lighting where the price of bulbs and control systems are plummeting. Additionally, it is forecasted that Sensorization, the remote monitoring of various sensor networks, checking on everything through the IoT will connect 50 billion devices by 2020. Even more rapid growth will occur in the next decade.
In the world of printing, giant strides are being made demonstrating and commercializing ultraviolet UV LED (light emitting diode) curing systems. These curing systems are being used to polymerize (cure) printing inks, coatings and adhesives. It is now being forecast that LED UV curing systems will replace traditional mercury lamp curing technology in the near future.
LED UV System Components
- LED is a solid-state device that generates UV light.
- ARRAY represents a grouping of LEDs designed to maximize UV light over a given area to cure effectively.
- OPTICs ensures that the maximum amount of light at the target irradiance is emitted through the lamp’s window glass.
- THERMAL COOLING is necessary to remove heat that is generated by a LED array.
UV LED vs. Mercury Spectral Distribution
UV wavelengths are measured in nanometers (nm). UV curing wavelengths are generally split into UV-A: 315 to 400nm, UV-B: 280 to 315nm, UV-C: 100 to 280nm, and UV-V 395 to 445nm. Alongside these groupings in the electromagnetic energy ranges are visible light: 400 to 700nm, and infrared: 700 to 3000nm. Longer wavelength UV-A and UV-V are able to penetrate deep into inks, coatings and adhesives. Shorter wavelength UV-C is capable of providing surface cure.
UV LED Curing Systems
An LED is a solid-state device that produces light when an electrical current is made to flow from the positive side (anode) of the circuit to the negative side (cathode). Key LED characteristics controlled by the lamp designer include wavelength and UV intensity output (W/cm²). Initially, UV LED curing systems, due to curing intensity output limitations, were adopted by small-scale and slow-speed applications in spot adhesives and digital inkjet markets. Gradually UV LED system suppliers have been able to develop higher intensity curing output systems so that larger scale, high-speed applications have become feasible, and now include flexo, gravure, sheetfed & web offset printing.
UV LED curing has required special formulations with narrow UV LED wavelength range responsive (expensive) photo initiator packages to enable effective curing. The majority of UV LED curables have been formulated to respond to 395nm. UV LED array manufacturers typically use rows of different wavelength LEDs commonly, 385nm, 495nm, and 405nm. Nevertheless, UV LED curing has grown quickly as adopters have been attracted to its advantages over conventional mercury lamp UV curing. These include very low energy consumption, long life, very favorable economics, low heat, safe operation, no mercury or ozone hazards, solid-state consistent curing, and elimination of bulb changes.
LED UV Curing Advantages
- Solid state curing consistency
- Small, compact, and scalable
- Low power consumption
- Instant on-off
- 30,000+ hours of reliable diode output
- Power to compete with mercury lamps
- 100% of spectral output in the UV range
- Lower pile temperatures
- Collimated optics to optimize curing from as close as 5mm to 150mm
- Uniform output across array width
- Liquid or air-cooled LED arrays
- Heat, mercury, and ozone eliminated
- No IR heating radiation
- No shutters required
- Heat-sensitive substrates tolerated
UV LED curing continues to spread across graphic arts applications with technological advances redefining cost-effectiveness and future growth.
UV LED preferable applications include curing black, white, and metallic inks, and laminating and cold foil adhesives. A common element with these is the necessity of curing energy to penetrate through dense pigments, films, or additives to effect a complete cure.