UV ink in gravure printing highlights (top)

Keywords: UV ink gravure pad printing technology gravure pad printing UV ink gravure pad printing solvent ink gravure pad printing technology One of the reasons for the wide range of printing is the unique performance of gravure pad printing ink and the ability to print images. Unlike screen printing inks and offset inks, gravure printing inks must undergo several rheological states during the printing process in order to transfer graphic information to the printing material. If the components of the ink are properly formulated, not only can a good ink transfer effect be achieved during printing, but also the resolution and the printing speed of the printed matter can leave a deep impression.
Gravure printing solvent-based inks include traditional solvent evaporation drying inks and epoxy cross-linked epoxy inks. In recent years, UV inks have also been added to the ranks of gravure printing inks. Like the UV inks that have been used for several years in screen printing and offset printing, gravure printing UV inks have the characteristics of fast curing and abrasion resistance. Today, three-dimensional metal, plastic, and glass substrates are very common substrates for gravure printing.
The earliest research on UV technology and gravure pad printing UV light curing technology appeared in the automotive inkjet industry in the early 1950s. It began to shift to offset printing in the 1960s. In the 1970s, UV-curable inks were already used in screen printing. Important position. Today, UV-sensitive resin materials are used not only in the ink industry, but also in materials such as adhesives, coatings, and pressure-sensitive adhesives.
In gravure pad printing, fine ink images can be obtained with UV inks, and the inks can be dried quickly. After the prints are dried, they have strong abrasion resistance and impact resistance, as well as incredible solvent resistance. It can be said that it is the advancement of printing equipment that makes it possible to enter UV ink into gravure pad printing, and can fully demonstrate the UV light curing technology and advantages in the pad printing process. The most obvious improvement in printing equipment is the increase in automation, advanced timing control in the printing process, improved closed-ink design, and automatic cleaning of the print heads. Improvements in these devices have made it possible to use UV ink for gravure pad printing.
The rheological knowledge of gravure printing inks is similar to that of gravure printing solvent inks. Gravure printing UV inks require a distinctive rheology. In a printing cycle, the ink is spread on the printing plate, excess ink is scraped off with a squeegee, leaving the ink in the recessed image corrosion area of ​​the printing plate. Until the silicone rubber pad moves the ink on the plate to the pad, the ink must maintain a certain viscosity on the plate.
After the printing plate ink is transferred to the transfer head (the gravure pad printing UV ink also contains some solvent, giving the ink the necessary rheology), the ink becomes more viscous as the solvent in the ink volatilizes. According to the theory of rheology, the adhesion of the tackified ink increases, the ink sticks to the surface of the substrate during the printing process, and the ink leaves the pad at the same time.
Gravure Pad Printing UV inks As previously stated, gravure printing solvent inks are dried by evaporation of solvents; another drying method is epoxy cross-linking and drying after heating, this ink has a higher molecular weight than normal The molecular weight of the ink is larger. The gravure pad printing UV ink is similar to the epoxy ink, except that the gravure pad printing UV ink undergoes a cross-linking reaction after encountering UV light, and the epoxy ink is thermally dried. After printing, the UV ink cures under strong UV light and it takes only a few seconds to dry completely.
As UV energy enters the ink layer, the photosensitizer in the ink reacts with its neighboring molecules called monomer and resin macromolecules and crosslinks into a solid three-dimensional network of molecules. The entire reaction takes only a few seconds. If the ink components are properly formulated, a UV photocuring reaction can also occur in UV inks with a large specific color. The resulting prints are stronger in abrasion resistance than many epoxy-based inks that are dried by heat, and have better or equal solvent resistance than epoxy inks.
The medium pressure mercury lamp has sufficient intensity of UV energy to cure the UV ink. Some mercury lamps incorporate various metals to change the luminous wavelength of mercury lamps so that the output wavelength reaches a specific wavelength range.
Materials with poor heat resistance, including ABS, PS, etc., can also be printed on top with gravure printing UV ink and cured effectively. When printing on these kinds of materials, the UV light curing device also needs to install a spectroscopic mirror. The mirror is placed on the mercury lamp to absorb most of the infrared light (heat) emitted by the mercury lamp, reflecting only the required UV light and very Less heat to the surface of the print. (To be continued)