Surface coating UV curing technology explain (3)

7. Current status of major fields

7.1 Super standard varnish application
The largest area of ​​UV application in Australia is paint for ultra-standard varnish. The future growth rate in this area will be lower than that of other applications that are used in smaller quantities and are being promoted, because at present it has a broad application base. Currently, end users in this field are looking for ways to improve processing efficiency (especially in the art of etching). A typical example being explored is the use of lamps of high power, such as 800-1000 watts/hour, which are now used in the United States and Japan. Industrial products using charge transfer complexes as photoinitiators (so-called acrylate-free chemistry) will also be used for this purpose. The use of these radiation-curing products to improve the reuse technology is also under investigation. 

7.2 Printing
The second major area of ​​application of ultra-standard varnish is printing. Due to the diversity of printing processes, radiation curing has a great opportunity to be promoted in this field. A new UV printer is being installed for signage printing. It can be used for movable sheet printing and rotary screen printing on narrow paper drums. In addition, foil printing and embossing can also be used. This type of printing press is particularly useful in high-quality multicolor printing. The use of this technology to print transparent labels on plastic bottles is superior to direct screen printing on bottles. Low-to-medium technical high-volume label printing is the area where UV offset printing applications have grown the most. Such placards can be produced at a moderate cost, with an offset speed of 100 meters per minute. Cationic UV offset printing inks have been used in the production of polyolefin labels, and acrylic inks cannot be used because they cannot withstand the low-temperature sterilization processing conditions necessary after printing. 
In other aspects of printing, aqueous varnishes for offset printing have shown a very competitive effect on UV technology. However, the economically viable UV dry transport system can be used in existing printing processes, which has increased the interest of people using UV printing. With a small extra cost, the traditional printing can be covered with a UV coating whose gloss can be almost equivalent to a laminate. Studies in these areas illustrate the close relationship between printing and coating technologies. In offset printing, Australian printers have adopted UV inks in wide paper tube systems, regardless of the application of live technology in narrow tube printing. The current experimental studies are significant for solving problems such as odor, contamination, migration of various content residues, and adhesion to various substrates used in the technology. Wide-web printing is currently being widely adopted in Europe and North America and will certainly be applied in Australia in the near future. Recent applications of UV screen printing in various high-quality reports and multi-color printing and overlaying of similar prints continue to grow rapidly. On the fabric, UV inks are not used for printing, and the use of plastisols is still the mainstay. However, the current progress indicates that UV printing on fabrics may be industrialized in the near future.

8. UV curing applications in security
In this regard, Australia’s development work is world-leading. In particular, the Australian Reserve Bank developed the first UV coating and UV-cured polymer currency. The need to develop this new type of banknotes was due to the reform of Australian circulation currency (from British pound to US dollar) in 1960. The new currency was paper. At that time, the criminal activities of the counterfeit currency were more serious. Therefore, AR Bank established A major research goal is to develop new coins that are not easily forged. The substrate for the new polymer banknotes is a polypropylene film. Because the original paper used was imported, the use of domestically produced polymers could improve the country’s foreign exchange balance. Moreover, the polymer is much smoother than paper, so that banknotes based on it can be printed very thin, ie the printing height is only 0.25 mm, so thin that it is impossible to copy with a copying machine. Polymers can also be made transparent, which is another way to deal with color photocopying. Compared with paper, the use of polymers can be better matched with other safety measures. Earlier, many countries in the world had tested coins stuck with high-density polyethylene lines. However, such banknotes were eventually peeled off with ink after they had absorbed moisture. Australian banknotes are the first stable plastics produced and are printed by the post-use molding machine. These polymer banknotes have been used repeatedly for about 8 years and have proven to be extremely successful. It has recently been proved that it is very difficult to forge, and the production of the banknote is reduced to 25% due to the long service life of the product. The production of such banknotes is a globally successful example of the application of UV technology. Since this production is very important to Australia, it focuses on the technologies in this area. During the processing, a polypropylene twin roll machine laminates about 75 μ thick sheets under heat and pressure, and the equal thickness sheets serve as original paper stocks. The polypropylene sheet was then processed in four steps to create an ink-shaded background and a watermark-like covert indicia. The roll paper is then cut into thin sheets using the same molding machine for printing paper. The sheet is sent to offset printing and printed on both sides of the sheet simultaneously using fine multicolor lines. According to traditional concave printing, a security measure was applied to the banknotes at this time. It may be an OVD or a packaging machine with special flowers 'target=_blank'. The cost of adding OVD is very high. It is used on the notes commemorating the 200th anniversary. Even during economic development, it will be limited to such uses. After the security flower is pressed, the bank note is coated with the last two UV varnish coatings. The first layer is high gloss, which makes it have good adhesion to polypropylene printing sheet; the second layer is matt, covered in The banknote used above has the feel and appearance of the original banknote. Here, the UV-cured overcoat is very important because it must be flexible, good detergency, antistatic, and conductive. The research work to improve such UV coatings continues. New UV-cured polymer banknotes have many advantages (Table 7). This shows that it is extremely difficult to fake such new banknotes. This also proves that the initial research and development plan is correct. The UV coating is adaptable, and it is easy to change the design of the banknotes with a little effort, so that it can cope with the counterfeit tactics that may occur at any time and be upgraded. The new banknotes are very clean, with good dirt and long life. This new polymer banknote has special environmental advantages. The banknote is beneficial to the environment because the UV topcoat is solvent-free and therefore the air pollution is extremely low during processing. In the early stages of production, the packaging used to dispose of discarded banknotes was necessary, because in the process of coin-making, a large amount of banknotes were destroyed due to destruction and sent to waste disposal. In addition, in order to sort out the circulation situation, the banknotes that have been circulated once every six months are to be recycled. Polymer banknotes can be easily recycled by the crushing process and are now used in fertilizer bins and agricultural support rods such as grapes. In contrast, previous paper currency handling is smashing and masking.                 
Table 7 - Performance of UV polymer banknotes over original paper currency
Hard to fake
2. Long life
3. Lower manufacturing volume
4. Lower production costs
5. Keep it clean in circulation
6. Recyclable

(to be continued)