UVA band, wavelength 320 ~ 400 nm (nm), also known as long wave black spot effect ultraviolet. It is very penetrating and can penetrate most transparent glass and plastic. More than 98 percent of the UVA radiation in sunlight penetrates the ozone layer and clouds to reach the earth's surface. UVA can reach the skin's dermis, damaging elastic and collagen fibers and tanning our skin. The 360 nanometer (nm) wavelength of UVA ultraviolet light conforms to the optically active response curve of insects, and can be used to make insect trap lamps. UVA of wavelength of 300-420 nm can pass through the special colored glass tube which is completely cut off from visible light, and only emit near-ultraviolet light centered on 365 nm, which can be used for ore identification, stage decoration, money inspection and other places.
UVB band, wavelength 275 ~ 320 nm (nm), also known as medium wave erythema effect ultraviolet. Medium penetration, its shorter wavelength part will be absorbed by the transparent glass, the sun contains uvb mostly absorbed by the ozone layer, less than 2% can reach the earth's surface, in the summer and afternoon will be particularly strong. UVB ultraviolet ray has erythema effect to the human body, can promote the formation of mineral metabolism and vitamin D in the body, but long-term or excessive irradiation can make the skin tanned, and cause redness and swelling desquamate. Ultraviolet health lamp and plant growth lamp are made of special violet glass (no light below 254 nanometers) and phosphors with a peak near 300 nanometers (nm).
UVC band, wavelength 200 ~ 275 nanometer (nm), also known as short wave sterilization ultraviolet. It has the weakest penetration, unable to penetrate most of the transparent glass and plastic. The short-wave ultraviolet radiation contained in sunlight is almost completely absorbed by the ozone layer. The harm of short-wave ultraviolet ray to human body is very big, short time irradiate can burn the skin, long-term or high intensity irradiate still can cause skin cancer. What ultraviolet ray sterilizes a lamp to send out is UVC short wave ultraviolet ray.
UVD band, wavelength 100 ~ 200 nm (nm), also known as vacuum ultraviolet.
The uv wavelength of sunlight is generally divided into long-wave UVA, medium-wavelength UVB and short-wave UVC, among which UVA reaches the surface about 95%, UVB about 5%-2% and UVC almost 0%.
Recently, Japan's industrial technology research institute made LED with the sterilization effect of ultraviolet light. It is reported that the main sterilization methods have high temperature sterilization, chemical sterilization, ultraviolet sterilization. Among these sterilization methods, ultraviolet sterilization of mercury lamp is an important sterilization method. Ultraviolet sterilization is not only effective for heat-resistant bacteria, and there is no chemical side effect of sterilization, can directly act on the DNA of bacteria to inhibit its proliferation. In particular, DNA absorption wavelength of about 260 nanometer light, bactericidal effect is obvious. Currently, most of the sterilization methods used are low-pressure mercury lamps that emit 256 nanometer wavelength ultraviolet light. But if the mercury leaks, it can cause damage to the environment. In addition, the mercury lamp equipment itself is also very large volume, therefore the market requires the development of the use of mercury, light and simple ultraviolet sterilization equipment.
Compared with the mercury sterilizing lamp, the LED ultraviolet lamp invented by the industrial technology research institute of Japan has the advantages of less power consumption, high safety and small size. The research team LED by satoshi yamazaki and junichi makino of the institute has successfully developed a nearly practical diamond LED with a luminous power of 0.3 mW through the modification of the quality of artificial diamonds and the improvement of electronic devices. The team used artificial diamonds to make a 0.5 millimetre diameter LED, which irradiated the tray with ultraviolet light to confirm e. coli's death. The irradiation distance is 2 mm and the irradiation range is 1 cm. In the future, the research team plans to improve the luminescence intensity of electronic devices to verify the effect of short time sterilization, so as to apply it to oral sterilization and tableware sterilization as soon as possible.