UV Curing

UV curing is a photochemical process, in which ultraviolet light is used to instantly cure or “dry” inks, coatings or adhesives. Liquid monomers and oligomers are mixed with photo initiators and when exposed to the UV energy, it instantaneously hardens. 

We distribute the following UV systems:

What is UV Curing?

UV curing is a photochemical process, in which ultraviolet light is used to instantly cure or “dry” inks, coatings or adhesives. Liquid monomers and oligomers are mixed with photo initiators and when exposed to the UV energy, it instantaneously hardens.
UV curing has been shown to increase production speed, reduce reject rates, improve scratch and solvent resistance, and facilitate superior bonding.

What are the advantages of UV Curing?

UV curing offers many advantages over traditional curing methods as solvent based products and heat drying.

  • Increases production speed
  • Reduces reject rates
  • Improves scratch and solvent resistance
  • Facilitate superior bonding
  • Prevents loss of coating thickness
  • Minimizes pollutant emissions
  • Takes up less floor space

Where is UV curing used?

UV curing is used within most industries where gluing, coating or surface modification is needed.

  • automotive
  • telecommunications
  • electronics
  • graphic arts
  • converting
  • metal, glass and plastic decorating

UV Radiation

The UV spectrum of bulbs and diodes depend on the materials inside them. By changing materials and the relative proportion of them, we can change the distribution of the output. This is a typically Hg, Ga and UV LED spectrum when we narrow down and look into the UV band width plus a little into the visible light.

It is important to be aware of which wave length is needed with your system.

Gallium Bulb
Mercury bulb
UV-LED

UV Radiation Curing

The wavelengths needed are defined by the coating formulation. When looking at the overall curing process, the important thing is to convert a liquid mass into a solid mass.

Converting the liquid into a solid mass, is done by sending photons into a coating with photo initiators, which are designed to react with the photons. It is crucial that the coating formulation matches the UV spectrum in order to activate the photo initiators correctly.

Coating formulation:
- Oligomer/polymer 
 (final coating properties)
- Monomer (reactive diluent, 
 lowers viscosity)
- Photo initiator
- Additives: Flow, wetting etc.
- Pigments
UV Radiation Curing

Measuring UV

UV measurement is an essential and integral part of a UV curing application process.

A UV measurement device called a Radiometer, provides the ultimate in process control, allowing for measurement of the radiant energy output of the light guide or optical accessory, generally directly at the cure site, either at specified wavelengths or integrated over broad wavelengths. The radiometer is an essential tool to set, monitor and control the exact amount of output irradiance for maintaining a repeatable, calibrated process traceable to the National Institute of Standards and Technology (NIST). A quality Radiometer should retain it’s calibration for at least 6 months. A memory for storing data with a PC software interface for downloading makes it easy to track and log the processes.

Measuring devices can be combined with Spot Curing systems, to provide a complete curing station with unmatched control and repeatability. Special electronics built into some sophisticated radiometers allow for connection of custom sensors for measuring light energy directly at the cure site, with some detector systems accurately measuring wide varieties of spot cures. Light guide ports automatically sense a diverse range of industry standard light guides (2, 3, 5, 8mm diameter).

UV Penetration

Each cure material (adhesive, ink) has specific absorption characteristics that react to a certain UV wave length.

UV light curing is widely used in the assembly of micro-electronics, medical, fiber optic assembly and printing industries.

It is important that the spectral output (the intensity of light at each wavelength over the whole wavelength range emitted by the lamp), is matched with the absorption characteristics of the photoinitiator of the cure material.

Some important wavelength regions include 250nm (UVC range) which is associated with surface cure, 320 and 365nm (UVB and UVA range) where wavelengths greater than 350nm improve depth cure, and the range between 400 and 500nm (Visible light) which employs visible photo initiators to absorb light and to provide even greater depth of cure.

Learn more about UV Curing here.

UV Curing Adhesives

Every high performance adhesive has at least two components to it. An obvious example is the two-part, room temperature curing material already mentioned. A less obvious example would be contact cement, where only a single material is handled. For this kind of adhesive to work, a solvent must evaporate from the product, leaving the actual bonding resin behind. So, the resin is one part and the solvent is the second part. In an ultraviolet-curing adhesive, there are also two components. One part is the adhesive resin itself and the second part—already mixed in—is called a photoinitiator. The secret of the photoinitiator is that it will not react with the resin by itself. The photoinitiator must absorb ultraviolet light before anything can happen. When the UV light is delivered, the photoinitiator will undergo a chemical reaction and produce by-products that cause the adhesive to harden.

Previously, we said that UV light has two important characteristics — wavelength and intensity. For the photoinitiator to react correctly, it must be exposed to light of the correct wavelength and of sufficient intensity. Otherwise, the chemical reaction will not happen, or may not happen completely. The result will be poor or inconsistent adhesive performance.