UV Curing

The physical properties of UV curing material are essentially influenced by the drying systems that are used to solidify them. The expected performance will depend on the parameters, design and control methods of the tubes, whether they are protective glue, ink, or adhesives. There are four key parameters of UV light:

1. UV Irradiation (Intensity)

2. Spectrum Distribution (Wavelength)

3. Radiation Quantity (UV Energy)

4. Infrared Radiation

Compared with the maximum radiation or radiation amount, and different UV spectrum ink and protective glue will show very different characteristics. The ability to identify different UV lamp tubes and match them with the optical properties of the curable material extends the UV cure as a fast, efficient process. Many of the optical and physical properties of the curing system (other than its own composition) affect the curing effect, which results in the difference in the appearance (performance) of the UV curable material.

The efficiency of a UV tube is determined by the efficiency of a UV lamp. UV curing is determined by the collision of photons - molecules.The light triggers the molecule to spread evenly through the material but the photon is different. Besides the characteristics of UV light source, the cured film also has optical and thermodynamic properties. Their interactions with radiation energy have a significant impact on the process of solidification.

Spectral Absorptivity: Energy is the effect of matter absorbing into the wavelength in a gradual increase in thickness.The more energy absorbed near the surface, the less energy it gets. But it varies with wavelength.The total spectral absorption rate includes all the effects of the oligomers and additives, including pigments, from the photo-initiator. 

Reflection and Dispersion: light, relative to absorption, is more likely to be changed by matter (or in matter), which is usually caused by the matrix materials and/or pigments in the curable material. These factors reduce the amount of UV energy that reaches deep, but improve the curing efficiency of the reaction.

Optical Density: like absorption. It consists of two factors: "opacity" and film thickness;Including absorption and scattering of light attenuation. It is represented by a single number, not as a spectral distribution.

Diffusivity: A thermodynamic characteristic contains specific heat, conductivity and density;The material "powder", the ability to accept heat. An increase in the temperature of the film and substrate resulting from the sudden influx of infrared energy.

Infrared Absorptivity: Temperature has a significant effect on the rate of curing reaction. Although the temperature rise in reaction also has an effect on temperature, but from the UV lamp, radiant IR radiation is the root of the surface heat source (not from the surrounding air or transmission of heat in the atmosphere. Excessive temperature rise is one of the most important limiting factors to affect the curing process.

Optical Thickness Coating and Ink

Due to the fact that opacity or color intensity is the feature we need, ink and pigment coatings pose special problems. Adhesives usually also provide relatively thick films. The optical thickness of a thin film is very important. When light penetrates or passes through a material, its reduction is described by Beer - Lambert - the upper layer of the film is not absorbed and the light that is not reflected will be worn to the bottom of the film.

The Significance of Spectral Absorption

The absorption of matter varies with wavelength. Obviously, a short UV wavelength of 200~300nm will be absorbed on the surface and can't reach the bottom. Generally speaking, the thickness of the film is limited, and the adhesive force is the primary characteristic of the substrate. Even the light trigger can absorb its sensitive wavelength energy, preventing the wavelength from reaching the deep light triggering molecules. A light can trigger for varnish coating, but for ink may not be the appropriate choice. For ink, corresponding to longer wavelength light trigger is a better choice. In addition to physical thickness, another function of spectral absorption is optical thickness. A thin film cannot be thick at one wavelength and thin at the other. Even the optical thickness of the varnish coating short-wave length 200~300nm is inclined to be thicker.

When the cured product contains a layer of "transparent" material on top of the UV curable material, the absorbency blocks the light energy. This is laminating, lens bonding, drug assembly, and, of course, DVD bonding. It is important to understand the spectral propagation characteristics of "transparent" materials to select the most effective spectra through which they are solidified. In general, the selection of long wavelength UV lamp, combined with long wavelength light trigger, is the key to successful solidification through materials such as PC.