About UV Curing

Microwave Bulbs
Standard UV Curing Lamps
Metal Halide Lamps

The choice of a particular lamp depends both on technical needs and on economic constraints. The two most important characteristics, which determine how fast and effectively a lamp will cure products, are spectral output and intensity.

SPECTRAL OUTPUT
Spectral output is defined as intensity of light at each wavelength over the range of wavelengths emitted by the lamp. For the most effective cure, this pattern of output must be matched to the pattern of absorption of the photoinitiator in the product. This principle forms the basis of all successful light cure applications. Spectral output determines whether a lamp is suitable for a particular application and how effectively the lamp will cure the product. Basic lamp engineering and modification of the material inside the lamp (called doping) enable shifting of emission maxima to other wavelengths to create different spectral output patterns.

Since there are certain absorption maxima common to many systems, there is often a choice of lamps for a given product. Major absorption areas of importance are 254 nm, responsible for surface cure, 365 nm, the "workhorse" cure wavelength also effective in promoting depth cure, and 400-436 nm in visible spectrum particularly useful for very large depth of cure. Please see the electromagnetic spectrum diagram, figure: A

INTENSITY
Lamp intensity is defined as the overall power of the lamp and is most often designated in watts. Also called power density, intensity refers to total lamp output across the entire electromagnetic spectrum. Lamp intensity generally affects rate of cure of particular products, since it is one of the factors determining the amount of light that actually reaches the product.

It is important to distinguish between basic lamp intensity and intensity or amount of light at the working surface. The quantity of light at the working surface is defined in either intensity units or energy units. Light intensity at the product surface, described by the term irradiance, is a measure of momentary exposure and is most often quantified in milliwatts/cm2. Light energy at the surface is a measure of cumulative intensity exposure (intensity x time), quantified as millijoules/cm2, and is simply:

mW/cm2 x seconds = mj/cm2

Measurement of irradiance (light intensity at the working surface) is essential in order to optimize cure conditions and maintain consistency in cure results. Easy to use equipment is available for this measurement.