As UV Curing Technology is becoming more and more popular in the printing industry, a kind of UV LED light emitting diode is used as the printing method of curing light source, which is concerned by more and more printing enterprises.
1. The Principle of UV LED Curing
Traditional UV Printing is a light polymerization initiator of UV ink. Under the irradiation of UV Light Source, after absorbing UV light of different wavelength and energy, the light polymerization initiator reaches the excited state, to form free radicals or iron, then through the transfer of energy between molecules, which makes the prepolymer, monomer and polymer become a excited states, resulting in charge transfer complex. The continuous cross-linking polymerization between complex particles eventually solidifies the ink into a film and adsorbs it on the printing process.
UV LED (Light-Emitting Diode) Light Source is the product of the development of ultraviolet light source technology towards more energy saving and environmental protection, is a very narrow spectrum that can transmit at a very narrow width, and can convert electrical energy into photoelectric semiconductor electronic components. Using the principle of photoelectric conversion, the PN junction is grown on the semiconductor substrate by implanting dopants and doping impurities. The luminescence mechanism is due to its electro-induced effect, and electrons and positive charges are converted into light energy by collision and binding during movement. The radiation wave crest is single, and the light energy is concentrated in a segment of ultraviolet spectrum with effective curing effect. Because the spectrum half width is much narrower than the traditional UV Light Source, high concentration of energy, low heat energy, more uniform irradiation. The use of UV LED Light Source can reduce the waste of printing resources and reduce the printing cost, thus saving the production time of printing enterprises and greatly improving the production efficiency of enterprises.
2. The Advantages of UV LED Printing
A. Ultra Long Life
Traditional UV Light Source has to change after 1,500 hours of work. Frequently replacing light source parts may cause the printing machine to cure fault frequency. At the same time, it may also reduce the operation efficiency of the printing press and effect the normal production of printing enterprises. However, the life of UV Light Source can reach more than 8 times of traditional UV light source, which can reach 12,000 hours and is not affects by the number of switches. According to the principle of its emitting, that UV LED Light Source is only one direction for electricity, forward biased, when an electric current passes through, electrons and holes is in the inside compound and emits light, ensures the stability of the light source, makes its light source decay rate is much smaller. For example, after 8,000 hours of work, the luminous intensity can reach 95% of its maximum power.
B. Energy-Saving
Traditional UV printing needs to open the light system to preheat before the formal printing, the stronger the light power, the longer the waiting time. Therefore, in order not to delay the printing period and the service life of the UV lamp, some printing enterprises often choose not to turn off the irradiation system so as keep it irradiated, causing a lot of waste of life of the light source. However, UV LED Light Source, according to its own structural characteristics, will convert the electric energy into the light energy instantaneously, which can be started at low pressure. So it can reach the maximum power output without preheating time. More than 80% of light source in the curing light source is used for curing ink. Meanwhile, the luminance and the heat are both low. Low light intensity can achieve the same curing effect of traditional UV light source, which can reduce power consumption by 70% to 80%. It is energy efficiency. It can be turned off when not needed, further reducing energy consumption and costs.
C. Suitable for a Wider
The traditional UV Light Source is large heat, and substrate material easy to heat deformation. But UV LED is a kind of cold light source, is a single wavelength, do not contain infrared light, do not have heat radiation, do not produce too much heat. Therefore, the UV LED Light Source can significantly reduce the heat generated by the solidification process without damaging the substrate appearance. For example, the thermal sensitive film substrate can not be easily printed in the traditional UV equipment, and it can be well printed in the UV LED printing mode. Nowadays, rapid development of label printing, printing speed is faster and faster, the substrate is thinner and thinner. If the heat is too high, the substrate will react with heat to cause wrinkles and affect the product quality. The use of UV LED Printing can greatly reduce the defect rate of the product and ensure the quality and quantity of the finished product during the printing period.
D. Protecting the Environment
Nowadays, the market share of UV Printing in printing industry has increased dramatically. Some printing enterprises also use high pressure mercury lamp as their UV Curing Light Source. After the use of the printing, it is necessary to waste human resources and financial resources to dispose of the mercury. If the processing is not timely, it will permeate into the surrounding environment. The mercury content of waste-water discharged is very low and does not directly cause human body. But the microbes in it can absorb mercury compounds and move through chain, eventually being absorbed and stored by seafood like fish and shrimp. Mercury is very slow to transform and excrete in the organism, and it can be stored in the body for a long time. Eating this kind of seafood can seriously affect your health. The UV LED Lighting System does bot contain any harmful chemical elements such as mercury and it will not cause any pollution to the environment or humans at work.
3. The Expectations of UV LED Printing
Domestic UV LED Technology has shown its obvious advantages in many aspects of industrial and civil use, but it started late in the printing industry. Nowadays, the UV LED market is growing at more than 20 percent a year and expected to reach $35 million by 2020. However, the price of UV LED Light Source is still at a high level. The price of a set of UV LED tubes is basically tens of thousands of yuan, which is much more expensive than a traditional UV lamp. In addition, the UV LED inks with it should choose the suitable photosensitizer in the very narrow spectrum. So it is more specificity. The cost is about 20% higher than the traditional UV ink, and the price is much higher than the traditional UV ink.
Now, most printing companies think the cost of upgrading equipment and raw materials. At the same time, environmental awareness is relatively weak, lacking the comprehensive consideration of social benefits and economic benefits. In addition to the lack of enforcement, laws and regulation in the domestic environmental protection field, most printing enterprises in China still adhere to use the traditional UV Light Source.
However, UV LED Printing conforms to the development trend of high efficiency, energy conservation and environmental protection advocated by packing and printing industry.
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