At present, the most commonly used UV light source is mercury vapor lamp, which can be divided into three types: low pressure mercury lamp (10-100 Pa), medium pressure mercury lamp (~100000 Pa) and high pressure mercury lamp ("100000 Pa"). It should be noted that high, medium and low pressure mercury lamps are defined in accordance with internationally accepted standards and are different from domestic titles. Early UV curing processes used low pressure to cure styrene-containing polyesters. Because of the small output power of this light source, it was quickly replaced by a medium pressure mercury lamp. The above medium pressure mercury lamp is generally referred to as a high pressure mercury lamp in China. The mercury vapor pressure lamp is a sealed transparent quartz tube with a length of mercury (up to 120 meters) with mercury inside. The electrodes are generally made of tungsten and are located at both ends, and an arc is generated when current is passed between the two electrodes.
UV-cured lamps (mercury) Although quartz is relatively expensive, all mercury vapor tubes used for UV polymerization are made of quartz. The main reason is that quartz has three important properties that are very suitable for making UV lamps: (1) transparent to ultraviolet light, no absorption or little absorption of UV; (2) poor thermal conductor; (3) low thermal expansion coefficient, quartz The purity and presence of other trace compounds can affect the emission characteristics of the lamp. The lamp tube is a fused quartz tube with a wall thickness of about 1 mm, an outer diameter of 20 to 25 mm, and an arc lamp total length of 2 M. A complicated electrode layout (electron emitter, pedestal, conductor, etc.) is sealed at both ends of the quartz tube. The quartz tube contains mercury for emitting energy as well as a starting gas, usually argon.
When the lamp is energized, an arc is generated between the two poles. As the voltage across the electrodes increases, the temperature of the gas rises, causing the mercury to evaporate, producing a mercury vapor arc and emitting characteristic ultraviolet light. When operating at full power, the fixture also emits visible light as well as some infrared light (IR).
Low-power germicidal lamps (for consumer products) arc lamps require a few minutes of warm-up time (ranging from 2 to 10 minutes) to achieve full spectral output because mercury must be completely vaporized in the quartz tube. During the initial warm-up period, the input power is more consumed by the electrode components of the preheating lamp, and finally the mercury present in the tube is completely vaporized. Therefore, the long induction period is one of the disadvantages of such a lamp. In addition, if the power supply is suddenly interrupted during operation, the mercury will quickly condense and it is difficult to restart immediately. The heavier heat load also requires cooling time. Usually it needs to be cooled for a while after shutdown (15-20MIN) before it can be started again. Therefore, the arc lamp should be equipped with a mechanical or electronic shutter to prevent high-intensity IR from burning the medium, and at the same time, it can cause the lamp to generate minimum heat and energy consumption.
A chemical reaction occurs between the electrode and the filler in the capillary mercury lamp (for the PCB industry), and the UV output is gradually reduced over time. In addition, each switch of the luminaire may cause deposition of the filler on the quartz tube, shortening the life of the luminaire. The average life of the lamp is 1000-1500 hours.
SHAOXING ZHENGHONG AUTO PARTS CO.LTD , https://www.kontinental-bearing.com