UNDERSTANDING ULTRAVIOLET LED APPLICATIONS AND PRECAUTIONS
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.
The lower UVA and upper UVB ranges (approximately 300nm – 350nm) are the most recent introduction to the market place.
These devices offer the potential to be used in a variety of applications including UV curing, biomedical, DNA analysis and
various types of sensing. There is significant overlap in all 3 of the UV spectral ranges; therefore, one must consider not
only what is best for the application, but also what is the most cost-effective solution, since the lower in wavelength,
typically the higher the LED cost. The lower
UVB LED and upper UVC
ranges (approximately 250nm – 300nm) is an area that is still very much in its infancy, however, there is great enthusiasm
and demand for this product in air and water purification systems. There are currently only a handful of companies that are
capable of manufacturing UV LEDs in this wavelength range and even a smaller amount that are producing product with
sufficient lifetime, reliability and performance characteristics.
As a result, the costs of devices in the UVC/B range are still very high and can be cost prohibitive in some
applications. The introduction of the first commercial
UVC LED based
disinfection system in 2012 has helped to move the market forward to where many companies are now seriously pursing LED based
products. Precautions A common question regarding ultraviolet LEDs is: Do they pose any safety risks? As described
above, there are different levels of UV light. One of the most commonly used and familiar sources for producing UV output is
the black light bulb. This product has been used for decades to produce a glowing or fluorescence affect on specific types of
posters as well as for other applications such as the authentication of paintings and currency.