With the rapid development of semiconductor lighting technology, light-emitting diodes ( LEDs ) have gradually entered various visible light illuminations due to their small size, long life, high reliability, and adjustable brightness. UV irradiation applications. As demand for lighting applications changes and demand for high-gloss and high-flux applications increases, the demand for high-power LEDs continues to grow, and specific requirements are constantly changing. In industrial fields such as UV curing, photochemical synthesis and photobio-modification, the power requirements of the UV source used are even above kilowatts (1 to 20 kW).
1, UV curing technology
UV curing refers to the chemical process of irradiating an organic coating with ultraviolet light (UV) to produce a reaction of radiation, radiation crosslinking and radiation grafting, and converting a substance of low molecular weight into a product of high relative molecular mass. Since no heating is required in the curing reaction, the reaction system contains substantially no solvent or only a very small amount of solvent, and the film is almost 100% cured after irradiation, so the volatile organic compound (VOC) emissions caused by the reaction Very low, basically does not pollute the environment, is a green curing technology.
Light curing technology also has many excellent advantages
The reaction rate is very fast, and the curing time is only a few seconds to several tens of seconds, which can effectively improve the productivity;
The curing temperature is very low, no additional heating is required, and curing can be achieved at room temperature, which is about 90% more energy efficient than thermal curing, and is suitable for materials that are not suitable for high temperature curing;
The cured product has excellent performance, corrosion resistance, wear resistance, high strength and impact resistance;
The curing cost is low, the output is high, and the product cost is good.
Therefore, light curing is an efficient, high quality, energy saving and environmentally friendly technology.
For a long time, photocuring technology has developed rapidly in the world, and its products are widely used in many industries, including photocurable coatings, photocurable inks, photocurable adhesives, photocurable protective sleeves, photoresists, laser 3D imaging, 3D. Modeling, etc. With the increasing emphasis on environmental protection around the world, many countries such as the United States, Germany, Japan, and Italy have passed legislation to limit the use of traditional coatings with high VOC emissions. Environmentally friendly new materials such as UV coatings have gradually replaced traditional products.
In recent years, the application of UV curing technology in floor coatings has received more and more attention and promotion, and has achieved commercial breakthroughs in the European and American markets. The floor is required to have a certain strength and rigidity, and according to different performance requirements of different fields, such as moisture, waterproof, warmth, wear resistance, corrosion resistance and the like. Conventional floor coatings use chemical methods to cure the coating under natural conditions. A layer of coating typically requires 2 to 6 hours of drying time and 24 hours of complete curing. In the construction process of the general floor coating, it is necessary to carry out the process of multiple grinding, painting and curing, so the construction period is long and the labor cost is high. The UV curing technology enables the coating to be deeply cured in seconds to tens of seconds, which greatly shortens the construction period and saves costs. Moreover, the surface of the UV coating has a very good performance after curing, and it can fully meet the requirements of the floor for various occasions.
2, ultraviolet light source
As one of the important components of the photocuring reaction, the ultraviolet light source also has a huge demand. According to statistics, in the printing industry, the global installation of UV light source curing devices in 1998 was 42,000 sets, and by 2007 it had reached 85,000 sets, more than doubled. At present, the UV curing technology is still in the initial stage in the application of floor coatings. With the continuous development and maturity of the industry technology, the demand for UV curing equipment will inevitably increase significantly.
There are many different types of UV light source products currently available on the market, including gas discharge lamps such as ordinary medium and high pressure mercury lamps, microwave medium pressure mercury lamps (induction lamps), pulse xenon lamps, etc., and ultraviolet LED light sources, which are used in different industries. . These types of light sources have their own advantages and disadvantages in UV curing applications, depending on factors such as lamp power, radiation efficiency, spectral distribution, and cost.
Figure 1 depicts the spectra of several common UV sources, including low-pressure mercury lamps, UV fluorescent lamps, medium-high pressure mercury lamps, xenon lamps, excimer lamps, and UVLEDs. The UV spectra emitted by different sources vary widely. In the ultraviolet curing reaction, a photoinitiator must be used, and the photoinitiator absorbs energy of a certain wavelength to generate a radical, a cation, etc., thereby initiating a reaction of polymerization and cross-linking of the monomer. However, different photoinitiators have different response ranges to photon wavelengths. Therefore, when designing a UV-curing construction scheme for floor coatings, it is necessary to ensure the matching of the ultraviolet light source and the photoinitiator.
Light-curing coating technology upgrade promotes LED curing equipment development
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Figure 1 Relative spectral power distribution of several common ultraviolet light sources
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