UV Curing Lamps

Mercury Spectrum

Metal halide lamps are mercury vapour lamps with the addition of metal halogens. The metal halogens are added to create specific wavelength lines of ultraviolet radiation to match the sensitivity of the photopolymer being exposed or dried. Metal halogens are compounds composed of metal and halogen elements combined within a curing lamp to form salts. The electro-negative halogens chemically react within an uv curing bulb to cause a reaction in which the metals take on a positive charge. As the internal temperature of the metal halide lamp increases to the vaporization point of the metals, the positive ions being produced allow the metals to release their outer electrons causing ultraviolet radiation output at specific wavelengths. Special lamp ballasts are required for metal halide lamps. These metal halide ballasts have a higher open circuit voltage and special output waveform (crest-factor). This feature also extends lamp life while keeping the mercury and heavy metals within the lamp structure in a plasmatic state during temperature and voltage variations. A standard mercury arc lamp does not have these requirements.

Iron Cobalt Spectrum

Iron metal halide lamps are extremely sensitive to over heating and need proper cooling . If the lamps are over heated for even a short period of time, iron is separated from the salt that is formed with the halogen and irreversibly fuses to the quartz. The iron part of the spectrum is now lost being unable to radiate.

There are three ways to tell if this has occurred:

• Check the spectrum to see if the 390nm peak is present using a spectrometer with the correct filter setting.
• Use a fluoroscope to check of stress fractures in the quartz.
• Visually check for white specks, this method is very difficult even for a experienced lamp technician.

Metal halide lamps are used in many types of applications whose photochemistry requires different UV wavelengths to initiate the photo-polymerization process. These come in either Gallium-Indium (GaI) or Iron-Cobalt (FeCo). Other additives are available upon request.

Gallium Indium Spectrum

Note that the Iron-Cobalt lamp has a broader spectrum with more spectral output in the 380 to 390nm region. The Gallium-Indium has an enhanced output in the 403 to 420nm region.

Another mix shown to the right is a multi-spectrum lamp, which is a mixture of Iron-Gallium producing an increased output over a broader region.

Multi Spectrum

These UV bulbs typically have a useful life averaging between 2000 to 3500 hours with less than a ten percent ultraviolet drop off in UV energy. Long life is accomplished by a technologically advanced process of preparing and coating electrodes with a proprietary formulated emission material. In addition, the lamps are filled with a uniquely formulated inert gas along with a mixture of halogens. This results in a lamp with an identical ultraviolet spectral output at 365 nanometers but with a lower internal electrode temperature.

The combination of improved electrodes and the internal fill mixture results in a lamp which extends electrode life, therefore yielding a cleaner longer lasting lamp with less UV drop off. If you presently have a uv ballast and want to confirm the compatibility of extended life lamps, please fill in ballast operating and striking voltage in comments section of lamp RFQ form.

Mercury Spectrum

These lamps radiate from twenty-five (25%) to one hundred (100%) percent more ultraviolet radiation at 365 nanometers (the standard mercury line) than standard mercury lamps. This only occurs at operation of 400 watts per inch or above. Lamps are manufactured with specially formulated electrodes and a unique metal halide compound.

Note: No additional electrical input power is required; lamps will operate on most standard mercury vapor ballasts. The lamps use a two millimeter quartz wall thickness (24 millimeter minimum outside diameter) and are warranted for 500 hours unconditionally. A typical 400 watt per inch Super UV lamp will equal or out-perform a standard 600 watt-per-inch mercury lamp while having the infrared radiation of a 400 watt-per-inch lamp.

Super UV Spectrum

The operating power level of the lamp affects total radiation efficiency in terms of UV energy output. For example a 400 watts-per-inch lamp will more than double the cure rate when compared to two lamps running at 200 watts per inch each. The UV intensity chart on the right shows a comparison of ultra-violet radiation of the same voltage lamp operated at 200, 300, 400 and 600 watts per inch by varying the secondary current applied to the lamp.

Efficiency vs. Watts per Inch