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Ultraviolet light occurs between the visible and x-ray spectrums. The Ultraviolet wavelength range is specified as 10 nm to 400 nm; however, many optoelectronic companies also consider wavelengths as high as 430nm to be in the UV range. Ultraviolet light gets its name due to the violet color it produces in the visible portion of the spectrum although much of the output of UV light is not visible to the human eye.
UV LEDs have seen tremendous growth over the past several years. This is not only the result of technological advances in the manufacturing of solid state UV devices, but the ever increasing demand for environmentally friendly methods of producing UV light which is currently dominated by mercury lamps. The current offering of UV LED modules in the optoelectronics market consists of product ranging from approximately 265nm – 420nm with a variety of package styles including through-hole, surface mount and COB (Chip-On-Board). There are many unique applications for UV LED emitters; however, each is greatly dependent on wavelength and output power. In general, UV light for LEDs can be broken down into 3 general areas.
The upper UVA type devices have been available since the late 1990s. These LEDs have been traditionally used in applications such as counterfeit detection or validation (Currency, Driver’s license, Documents etc) and Forensics (Crime scene investigations) to name a few. The power output requirements for these applications are very low and the actual wavelengths used are in the 390nm – 420nm range. Lower wavelengths were not available at that time for production use. As a result of their longevity in the market and the ease of manufacturing, these type LEDs are readily available from a variety of sources and the least expensive of all UV product. The middle UVA LED component area has seen the greatest growth over the past several years. The majority of applications in this wavelength range (approximately 350nm – 390nm) are for UV curing of both commercial and industrial materials such as adhesives, coatings and inks. LEDs offer significant advantages over traditional curing technologies such as mercury or fluorescent due to increased efficiency, lower cost of ownership and system miniaturization. The trend to utilizing LEDs for curing is increasing as the supply chain is continually pushing to adopt LED technology. Although the costs of this wavelength range is significantly greater than the upper UVA LED module area, rapid advances in manufacturing as well as increasing volumes are steadily driving down prices.
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