How UV-C effect for disinfection?
Conditions for UV-C LED disinfection effect test
(Bacterial strain: E.Coli / Output: 40 mw / Irradiation distance: 100 mm / Irradiation time: 120 seconds)
UV-C disinfection features
UV-C disinfection has features that are different to other disinfection methods that use heat or chemicals, and can be used in many different situations.
What are advantages of ultraviolet disinfection?
no need to wipe and clean the area after use as is the case with chemicals.
also effective against microorganisms that are resistant to chlorine,when chlorine disinfection does not work.
does not create bacteria that is resistant to ultraviolet disinfection.
What are the risks of UV-C?
- ・It may cause health problems to humans and living things (acute and chronic ultraviolet radiation induced damage).
- ・It may cause discoloration and deterioration of such as organic materials, typically resin and plastic-based material.
- ・Places in shadow or where light does not reach cannot be disinfected using this method.
How does UV-C disinfection proceed?
Bacteria and viruses proliferate by cell division based on genetic information to cause infection and illness. DNA and RNA holds the genetic information necessary for this proliferation to occur. Irradiating with UV-C changes the helix structure of DNA and RNA of held by bacteria and viruses, which can inactivate these bacteria and viruses resulting in reducing their proliferation.
Fig.1: UV-C disinfection process
Disinfection effect varies depending
on UV wavelength
The disinfection effect on DNA and RNA of bacteria and viruses dpendes a lot on the UV wavelength. Within the ultraviolet range of UV-A, UV-B and UV-C, UV-C with the shortest wavelength can provide the greatest performance to inactivate bacteria and viruses. Its effect is over 1,000 times greater than UV-A and over 50 times greater than UV-B.
Furthermore, from Fig.3 we can see that a wavelength of around 265 nm from among UV-C wavelengths (100 nm to 280 nm) provides the highest inactivation efficiency. Stanley Electric develops and manufactures UV-C LEDs that generate light with a peak wavelength of 265 nm, which has the highest disinfection effect.
Effectiveness on the new coronavirus
Stanley Electric has verified the effect of ultraviolet LEDs on the new coronavirus (SARS-CoV-2). From the results of evaluation tests performed jointly with Yamaguchi University (with Associate Professor Horishi Shimoda, Professor Daisuke Hayasaka, Veterinary Microbiology Department, Joint Veterinary Faculty) we confirmed that ultraviolet disinfection is highly effective. When verifying the advantage of each wavelength, we also proved that a 265 nm UV-C LED has a better sterilization performance over a 280 nm UV-C LED by a factor of 1.8, and confirmed the superiority of our UV-C light source.
How the disinfection effect is calculated?
The required irradiation amount and conditions by ultraviolet varies depending on the targeted type of bacteria, virus, and other microorganisms. In general, the disinfection effect is determined by totaling (the cumulative light amount or ultraviolet dose) the light strength (intensity) and the time UV light is shone onto the object (irradiation time). The longer irradiation time, the more the cumulative light amount increases, resulting in a greater disinfection effect. Conversely, a high output ultraviolet intensity is required when disinfecting is required for a short time.
How the cumulative light amount is calculated?
Example: When an ultraviolet dose of 40 mJ/㎠ is required to
disinfect 99.99% of bacteria A
Intensity depending on the distance
The intensity changes depending on the distance to the object. In general, the intensity falls the further the distance to the object from the light source. And intensity increases the closer to the light source axis, and intensity decreases the greater the displacement from the axis.