UV light history and evolution
UV stands for Ultra Violet, representing light with a shorter wavelength than violet light that is invisible to the human eye. UV light has always been present in sunlight, but it was not until 1801 that a German scientist discovered its existence.
In 1878, people discovered that the ultraviolet radiation in sunlight had germicidal and disinfectant properties.
In 1901 and 1906, humans invented the mercury arc, an artificial UV light source, and the quartz tube that transmitted UV light more efficiently, respectively, officially opening up the use of artificial UV light sources.
In recent years, new UV light sources have been invented, such as UV LEDs and excimer UV lamps.
UV (Ultraviolet)
Types of UV Light
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UVA Wavelength : 320~400nm
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UVB Wavelength : 280~320nm
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UVC Wavelength : 200~280nm
UVC disinfection principle
UV light can destroy the DNA or RNA molecular structure of microorganisms, causing them to die or be unable to reproduce, thus achieving the purpose of sterilization and disinfection.
The optimal sterilization wavelength is around 265nm, so 265nm UVC LED is currently the most effective light source for sterilization. Other UVC wavelengths also have sterilization effects, but the farther away from 265nm, the decrease in effectiveness and more energy is required to achieve the same sterilization power.
To quantify the amount of UV light, the commonly used unit is the dose, measured in J/cm^2.
Dose = UV radiation intensity (W/cm^2) x time (sec). The required dose for sterilization for each microorganism can be verified through experiments, but UVC LED is a relatively new technology, and most experimental data is still based on UV mercury lamps.
In recent years, a new 222nm UV excimer lamp has emerged. Due to the characteristics of this wavelength, it causes less damage to the human body than other sterilization lamps. However, its sterilization efficiency is still not as good as the 265nm light source, and the lifespan and price of the excimer lamp are not ideal, so it has not yet been widely used in the sterilization application market.