In recent years, UV LED curing technology has received great attention from all over the world. In many application fields, UV LED light sources are gradually replaced by traditional mercury light sources. UV LED is an electroluminescent diode. Compared with the traditional UV mercury lamp, it is more environmentally friendly, efficient and has low energy consumption. It is a green industrial technology that is truly oriented to sustainable development.
UV LED Features
Single wavelength, high luminous efficiency, low energy consumption
UV LED can directly convert electrical energy into UV light, and it emits single-band ultraviolet light. The light energy is highly concentrated in a specific ultraviolet light band. Now the mature applications in the market are 365nm, 385nm, 395nm, 405nm. However, the emission spectrum of the traditional UV mercury lamp is very wide, and the ultraviolet spectrum that really plays an effective curing role only accounts for a part of it. At the same time, the photoelectric conversion efficiency is low and the energy consumption is large.
Does not generate infrared rays and ozone
Traditional mercury lamps generate infrared rays and emit a lot of heat, which can easily damage heat-sensitive substrates. The UV LED is a cold light source, which can effectively avoid the shrinkage and deformation of the substrate due to overheating, and has wider adaptability to the material. At the same time, UV LEDs used for UV curing are usually long-wavelength ultraviolet light, so no ozone is generated during the curing process, and a good working environment can be maintained. Compared with traditional mercury lamps, it is safer and more environmentally friendly.
Point and light, electronic control
UV LEDs do not need to be preheated like mercury lamps, nor do they need to be constantly on in order to maintain lamp life and work efficiency. The UV LED can turn on (off) the light instantly, and the output energy can also be freely set, and can be automatically adjusted according to the speed of the machine, which is very energy-saving and simple and convenient to control.
Long service life and low maintenance costs
The service life of LED UV lamps can reach more than 10,000-50,000 hours, which is more than 10 times that of traditional mercury lamps, and the light attenuation is very slow, and the service life is not affected by the number of switches. At the same time, the LED light source has no mercury and no accessories such as lampshade, so almost no maintenance is required, which reduces the maintenance cost.
High flexibility of use and small system size
LED light sources can be divided into point light sources, line light sources, and surface light sources, and the effective irradiation area can be customized. The light source equipment is small in size, and the irradiation device and related supporting devices are very compact, eliminating the need for the large mechanical installation space and pipeline construction in the past. This feature makes it adaptable to various production processes and the production process is more efficient.
UV LED market and prospects
According to TechNavio research, the UV LED market has maintained a very high growth rate in the past seven or eight years, from US$20 million in 2008 to US$90 million in 2014, with a compound annual growth rate of 28.5%. In 2016, due to the active introduction of UV LED products into various applications such as light curing, sterilization and purification, the estimated output value will reach 166 million US dollars, of which the output value of LED application in the light curing market will reach 81 million US dollars. By 2020, the compound annual growth rate of the global UV LED technology market will reach 39%.
In 2015, the UV curing market accounted for 48.14% of the UV LED technology market. The increased demand for UV LED curing equipment in the printing industry and the dramatic improvements in flux density for UV LED chips have made UV curing a significant portion of the UV LED technology market. At the same time, the printing industry has developed into a major user of LED curing equipment. The great success of UV LED technology in the inkjet field has promoted the application of UV LED technology in the entire printing industry.
UV LED technology for the European market
European UV LED technology will grow from $36.28 million in 2015 to $190.2 million in 2020. Environmental regulation of hazardous substances and ban on mercury lamps in Europe have made the European market a significant contributor to the global UV LED market revenue. Because UV LEDs are environmentally friendly and consume less power, they have a large number of applications in the medical, adhesive, and printing curing markets in Europe, and these applications have also become a major factor in the growth of the European market.
UV LED Technology for North American Market
UV LED technology accounted for 26.8% of the North American market share. TechNavio predicts that the North American UV LED technology market will grow from $34.33 million in 2015 to $179.06 million in 2020. Due to the rapid growth of the market, the graphic arts industry in North America is increasingly using UV curing equipment and technology. Other UV LED light curing applications involve the healthcare industry, communication equipment industry, automotive industry, building materials industry, etc.
UV LED resin
Since UV LED is a single-band UV light source, the absorption spectrum of the initiator needs to match the emission spectrum of the LED. At present, there are not many initiators developed for LED light sources on the market, and the ones that can be mass-produced are even scarcer. Therefore, the matching problem of initiators has always been a difficult point in LED light curing. At present, the photoinitiators that can be used include TPO, TPO-L, ITX, DETX, BAPO and so on. However, these initiators do not have very strong absorption peaks in the wavelength bands of 365 nm, 385 nm, 395 nm and 405 nm, so the initiation efficiency is not high. At the same time, compared with the traditional mercury lamp, its power is lower and the irradiation energy is not high, especially for the colored ink system. If the printing speed is too fast, it is easy to cause incomplete curing of the ink.
In view of the problems of initiator matching and equipment power, the light-curable resin used for LED curing must have very high reactivity to avoid problems such as poor curing. At present, there are very few UV LED curing resins available in the market, which are mainly limited by the two major problems of reactivity and stability.
Balance of cure speed, resistance to surface oxygen inhibition and storage stability
Curing speed, resistance to surface oxygen polymerization and storage stability are three important aspects of UV light curing technology. It is relatively easy to achieve alone, but it is very difficult to take into account the three. Through a lot of experimental work, the researchers of Runao Chemical used innovative methods to change the resin structure, and used auxiliary means to develop three UV LED curing resins with different application systems, which perfectly achieved the curing speed, resistance to The balance of surface oxygen inhibition and storage stability can well solve practical application problems.