Metal halide (MH) light sources were developed in the 1960s for general purpose lighting. These light sources are categorized as high intensity discharge lamps, and utilize a ceramic or quartz arc tube to vaporize mercury and metal halides (bromine, iodine, etc.). The resulting bright white light that is produced has a high color rendering index, and the light energy may be projected at a significant distance from the source when combined with a reflector. The chemistry of the lamp may be adjusted, and the lamp may be used with filter combinations, so that the spectral power distribution (light energy) provides a match to natural sunlight or other sources of light.
An example of how the spectral power distribution (SPD) of natural sunlight compares with light produced by MH lamps is shown in the figure below.
Because the MH lamp produces a close spectral match to natural sunlight it was increasingly used in applications that would allow for laboratory testing of the effect of sunlight on certain products. Applications included testing photovoltaics, vehicle components, and materials like coatings and polymers.
Weathering Chambers and the EYE Super UV
In 1982 Iwasaki Electric and Dainippon Plastics collaborated on the development of a metal halide lamp weathering test chamber. Their goal was to create a weathering test chamber that used high irradiance, and therefore provided the promise of significantly reducing the time required for laboratory weathering tests. The metal halide lamp was chosen because of its ability to maintain its close spectral match to natural sunlight while also allowing for very high levels of irradiance.
This collaboration ultimately led to the development of the EYE Super UV chamber.
The graph below compares the spectral power distribution and irradiance of the metal halide Super UV to traditional fluorescent and xenon tools, and natural sunlight.
In 1984 the first commercially available metal halide weathering tester was sold in Japan.
Iwasaki began selling its Super UV (SUV-W161) weathering test chamber through its North American subsidiary EYE Lighting Applied Optix in 2010.
In 2014 the ASTM G03 Committee on Weathering created a subcommittee to develop a standard for metal halide weathering chambers.
As of 2020 there are approximately 1000 metal halide weathering chambers installed globally.
Standards Compliance Testing: Metal halide weathering chambers are presently specified in company proprietary compliance test standards. These companies are Japanese in origin and have been using the Super UV chamber for decades.
Screening Tests: A growing number of non-Japanese companies are using the Super UV to rapidly expedite the screening test process during new product research and development. These companies are highly focused on leading their respective industries with regard to new product development, quality, cost savings, etc. and use the Super UV to gain a competitive advantage due to the huge reduction in test and product development time.