UV LED printing The technology
UV LED printing technology is based on the rapid curing process of a printing fluid with UV light. The printhead creates individual drops of ink from the fluid and propels them in the direction of the marking material. The drops are applied in lines below the printhead through the movement of the marking material. In the same step, high-intensity UV radiation cures the fluid. The material is not heated by this process, meaning that the resulting markings can be used immediately. The printed plastic or metal markings have high wipe and scratch resistance and are especially resistant to chemicals.
Your advantages
- Versatile marking process with optional color printing and the availability of over 1,000 marking materials made of plastic or aluminum
- Accelerated processing of large quantities with the automatic material feed and the device stacking and de-stacking function
- Scalable print resolution between standard (300 dpi) and HD printing (600 dpi)
- Markings can be used immediately due to the intensive curing of the fluid with UV light
- Print results that are resistant to chemicals, smudges, and scratches
- Low energy consumption with LED technology
(1) Printing fluid (2) UV radiation (3) Polymers (4) Color pigments
Colorants Solvent-based ink or solvent-free fluid
Depending on its application, creating identifications with a solvent-based ink requires that the marking cannot be dissolved by other solvents. This method is therefore not suitable for every application. To cure the ink, the component is heated for several minutes following the printing process. Depending on the material and ink used, it is heated to temperatures between +70°C and +200°C. Not all materials are suitable for this process; plastics in particular can warp at high temperatures.
The UV LED printers from Phoenix Contact use solvent-free printing fluid. This fluid consists of three main components: UV initiators, binder material, and color pigments. The key to UV LED printing technology is photochemically induced polymerization. UV radiation converts the fluid initiators into radicals. Radicals are molecules with one free electron. The radicals activate molecules in the bonding components, called monomers, and bond with them to form chains and matrices. Such chains are referred to as polymers. They surround the color pigments and thereby cure the fluid without generating heat.
Printheads
There are basically two different types of printheads.
| Continuous inkjet | Drop-on-Demand inkjet (DOD) | |
|---|---|---|
| Type of printhead | ||
| Firing off the ink drops | Permanent | If required (during the actual printing process) |
| Inks/fluids | With a high solvent content | Containing solvent or solvent-free |
| Nozzles | An individual nozzle with continuous jet | High number of nozzles with vertically delivered drops |
| Resolution | Low | High |
In Drop-on-Demand inkjets, two different printhead technologies can be used:
Bubble jet method: Here, a vapor bubble is generated through electrical heating, with the resulting pressure then pushing the drops out of the nozzle. Ink containing a solvent is required to generate the vapor bubble. Bubble jets are used in inexpensive printers, e.g., for private use.
Piezo jet method: Here, the nozzle channels consist of piezo crystals, which are moved by electrical pulses in waves. This then causes the drops to be fired out. Piezo jets are high-quality, durable printheads that are used in UV printing, for example. The BLUEMARK ID and BLUEMARK ID COLOR printers from our portfolio use the piezo jet method.
Light spectrum
Light sources
UV lamps (burners) are frequently used as UV light sources. Their use is associated with high heat generation due to their construction. These burners are particularly powerful, but also have a large variance of emitted UV light. As such, a UV C burner (100 to 280 nm wavelength) also emits light in the UV A (315 to 380 nm) and UV B range (280 to 315 nm).
Wavelength range of UV LEDs
LEDs are an alternative to the burner lamps. UV LEDs emit light in a very narrow range (UV A), and therefore have significantly lower variance than the burners. The UV-induced, photochemical polymerization is often in a wavelength range of 200 to 400 nanometers. The minimal heat generation is an additional advantage. This allows the creation of smaller and lighter printers, such as the BLUEMARK ID (COLOR) from Phoenix Contact.
