The fact that ultraviolet light can kill bacteria is no longer news, and UV lamps can be seen everywhere in our daily lives, including hospitals, laboratories, and even our homes. As long as there is a need for sterilization, the UV lamp will never be absent.

In fact, the structure of the UV lamp is closely related to its principle of sterilization. Ultraviolet sterilization is known to destroy and change the structure of microbial DNA (deoxyribonucleic acid) through ultraviolet radiation, so that bacteria immediately die or can not reproduce offspring, to achieve the purpose of sterilization.

Depending on its different biological effects, ultraviolet light can be divided into UVA band, UVB band, UVC band and UVD band. Among them, the wavelength of UVC is 100 ~ 275 nm, which has a tangible sterilizing effect and is therefore also referred to as short-wave ultraviolet. The ultraviolet sterilization lamp emits UVC short-wave ultraviolet.

UVC is suitable for sterilization because it is easily absorbed by the DNA of the organism, especially ultraviolet light at a wavelength of approximately 253.7nm. However, this same property renders it highly damaging to the human body. Short-time exposure to UVC radiation may result in burns, and prolonged exposure to UVC at high intensity can cause skin cancer. In everyday life, the fact that UVC does not cause harm is due to its minimal penetration ability. The short-wave ultraviolet rays present in sunlight are largely absorbed by the ozone layer and prevented from penetrating most transparent glass and plastic.

The reason why quartz glass is applied in UV lamp

As previously stated, the penetration of UVC is weak. The ultraviolet germicidal lamp is actually the same as the ordinary fluorescent lamp, which belongs to the low-pressure mercury lamp, using low-pressure mercury vapor (<10-2Pa) to emit ultraviolet rays after being stimulated. However, the fluorescent lamp tube uses ordinary glass, which can not be penetrated by the UVC (253.7nm) with poor penetration ability, so it can only emit visible light after the UVC being absorbed by the fluorescent powder inside the lamp tube.

In comparison to conventional glass, quartz glass exhibits a significant enhancement in performance, with a higher transmittance of up to 80%–90% for all wavelengths of ultraviolet light. Consequently, the majority of germicidal lamp tubes are now manufactured using quartz glass. However, due to the different coefficient of thermal expansion, the germicidal lamp can not generally seal the aluminum cap, and the lamp cap material is mainly bakelite, plastic or ceramic.

In addition, the spectral lines of the ultraviolet germicidal lamps are mainly 254nm and 185nm. The 254nm ultraviolet light is effective in killing bacteria by irradiating the DNA of microorganisms. In contrast, the 185nm ultraviolet light is capable of transforming O2 in the air into O3, which has a potent oxidation effect and can compensate for the limitations of ultraviolet light in reaching all areas. The addition of a sufficient quantity of the titanium (Ti) element during the processing of quartz glass allows for the blocking of ultraviolet light with a wavelength below 200nm, while the ultraviolet light with a wavelength of 254nm can penetrate the quartz glass smoothly. It can be seen that the addition of titanium elements can be effectively controlled in order to regulate the escape of 185nm ultraviolet light, which in turn allows the production of three distinct ultraviolet bactericidal lamps: low ozone (ozone free) UV lamp, ozone UV lamp and high ozone UV lamp.