UV Pad Printing Inks
Pad printing is the use of a deformable pad printing tip to transfer the ink from the graphic area on the printing plate to the substrate. The printing process of pad printing is to supply ink to the pad printing plate by the ink supply device, scraping device to scrape the ink from the blank space of the printing plate, the pad printing tip is pressed to the pad printing plate, dipped into the ink in the graphic area, forming a reverse graphic on the surface of the tip, and then the multi-printing tip is embossed on the substrate to transfer ink to the substrate to complete the printing.
Pad printing and screen printing have many similarities, such as the applicability of a wide range of substrates; a wide range of inks, pad printing ink and screen printing ink can basically be common; by replacing the fixture and printing plate can be very convenient to complete the printing of different products and so on. Therefore, in many printing occasions, pad printing and screen printing is like a pair of twin sisters as close, playing an important role in special printing technology.
However, the characteristics of pad printing and screen printing and the use of technology there are some differences. First of all, from the ink transfer process, pad printing and screen printing has obvious differences; Secondly, pad printing machine and screen printing machine structure is not the same; In addition, pad printing technology for product categories and screen printing is also very different. Objectively speaking, the difference between pad printing and screen printing to be far more than the similarities between them, the reason why they are accustomed to bundled together, the greater reason is that pad printing and screen printing in the face of a common market, in this common market, screen printing can not be separated from the pad printing.
The characteristics of pad printing are mainly:
① Can be printed on irregular shaped concave and convex surfaces. These printing using other printing methods is difficult or even impossible to complete, but the use of pad printing can be easily completed, and can achieve multi-color printing.
② can print fine graphics, generally can print 0.05mm fine lines.
③ Printing stability and continuity, even if a long time to print, the printing accuracy will not change.
③ Printing is stable and continuous, even if printing for a long time, the printing accuracy will not change. ④ Eliminate the drying process, continuous multi-color printing.
⑤ Wide range of printing, can be in plastic, metal, glass, ceramics, leather, plastic wood and other materials products on any concave-convex surface accurately one-color, two-color and color graphics printing, but also soft contact printing, but also in the soft items (such as fruits, pastries, etc.) as well as fragile and fragile items (such as ceramics, glass products, etc.) on the printing.
⑥ The pad printing process is easy to learn and reliable, with no particularly esoteric techniques.
Pad printing process also belongs to the indirect printing, pad printing adhesive head surface ink transfer is limited, in general, the pad printing adhesive head can be dipped in the amount of ink for the transfer of the printing plate concave the total thickness of the ink 2/3, pad printing to the substrate on the thickness of the ink layer is only pad printing adhesive head surface of the ink layer thickness of 2/3, so the surface of the substrate is roughly the thickness of the ink layer of the printing ink layer depth of the printing plate is 4/9, so the printing of the ink layer is thinner to obtain a more Therefore, the printing ink layer is thinner, to get more eye-catching graphics, the pigment content of pad printing ink should be higher than screen printing ink, and the fineness is also finer.
Pad printing adhesive tip is pad printing process is unique, it has excellent deformability and resilience, pad printing adhesive tip in the pressure can be completely with the surface of the substrate to realize the printing. However, in the pad printing process, on the one hand, the pad adhesive tip by the pressure generated by the deformation to pass the ink; on the other hand, the deformation of the pad adhesive tip will also cause deformation of the print, dot increase. In order to minimize this effect, the thixotropy of pad printing ink is required.
3.8.2 Plate making for pad printing
At present, the gravure plate used for pad printing includes photopolymerized resin gravure plate and pad printing corrosion steel gravure plate. The application of photopolymer resin plate to pad printing process has not been long, but due to many characteristics of polymer materials, such as high plate making efficiency, ease of use and other advantages, by the industry attention. The photopolymer resin gravure plate making method is the same as the solid photopolymer letterpress plate, using a positive picture to make the plate. The photopolymerizing resin is mainly nylon photopolymer, which is cast on the surface of the zinc plate. Nylon has very good abrasion resistance, photocuring can be obtained after the extremely fine dot, especially for reproducing fine small prints. However, the photopolymerized resin gravure plate has a low surface hardness, short service life and other shortcomings, so it is only suitable for small batch production.
Pad printing steel plate is also known as metal corrosion gravure, steel plate in the pad printing process on the use of the current also occupies a dominant position. In the etching of graphics before the surface of the steel plate should be mechanically fine grinding to a mirror finish to ensure that the corrosion of the edge of the graphics of the neatness, and then ensure the integrity of the dot structure, so that the printing of graphics trimming sharpness and color reproduction to the maximum extent possible, while ensuring that the scraping of the ink cleanliness as well as the rate of print resistance. The production of metal plate is often used to carve and corrosion methods, the cost of engraving is relatively high, only a larger number of orders of gravure printing can be used. Pad printing steel plate is mainly used in the corrosion method. The reason is that the cost of pad printing is very low, difficult to bear the high cost of engraving process. Corrosion method used in the production of metal plates for a long time, due to the corrosive agent is basically an acid solution, there is serious environmental pollution, they are facing the ultimate elimination of the end.
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