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In the packaging and printing industry, pearlescent ink can show pearlescent or metallic luster on different substrates (paper, plastic, etc.), which improves the grade of packaging products. This feature makes pearlescent ink printing a bright spot in packaging and decoration printing, and is favored by people. Today, the editor of the paper industry network has inquired about the relevant information and will take you to understand the relevant pearlescent ink technology in detail, and learn about the relevant content.
Pearlescent inks generally consist of pearlescent pigments and binders. Pearlescent pigments are in powder form, so in order to ensure uniform dispersion, they must be fully wetted with the solvent of the corresponding system before blending. In the process of gravure printing with pearlescent ink, we generally soak the pearlescent pigment with butyl ester for more than 3 hours, then add the corresponding binder (such as the ratio of gold oil 1:1), and stir gently. Never stir with a high-speed ink mixer, because the mica in the pearlescent pigment is flaky, brittle, easily damaged, and loses its pearlescent effect.
Pearlescent pigments in pearlescent inks have large particle sizes. The commonly used mica titanium pearlescent pigment has a particle size of 25 μm and a thickness of 0.25-0.60 μm, which is easy to precipitate. So pearlescent ink is best to be ready-to-use. The prepared pearlescent ink should be sealed away from light, and the storage time should not exceed 5 days. When printing, stir frequently at low speed to ensure full flow of pearlescent pigments.
In the printing process, proper ink viscosity can ensure smooth transfer of pearlescent pigments and gloss of printed matter. However, due to the continuous volatilization of the solvent in the ink, the viscosity of the ink will become higher and higher, so an appropriate amount of butyl ester should be added for adjustment. Generally speaking, the viscosity of pearlescent ink is maintained at about 16 seconds (coating with a 4# cup at 25°C), and satisfactory results are often obtained. Better pearlescent effect can be obtained by printing pearlescent ink on smooth substrate surface. Among the paper substrates, glass cardboard, coated paper and white cardboard are the best. Due to the large particle size of pearlescent pigments, the pearlescent pigment particles contained in the mesh of the plate cylinder are limited, and it is difficult to express tiny dots. Therefore, pearlescent ink is not suitable for printing halftone products, and is mostly used for solid printing. In on-site printing, in order to ensure the smooth transfer and uniform coating of large pearlescent pigments, the dimple depth of the gravure cylinder is greater than 25μm, and the number of screen lines on the printing plate is greater than 75 lines/inch.
In addition, the printing pressure should be appropriately increased. Generally speaking, the thicker the ink layer transferred from the pearlescent ink to the substrate, the more uniform the distribution, and the more obvious the pearlescent effect. But pay attention to adjust the appropriate machine speed, workshop temperature and humidity at the same time, improve the drying speed, and prevent the back of the substrate from sticking. In order to better show the pearlescent effect of the product, the product printed with pearlescent ink can be polished. This not only protects the pearlescent ink layer, but also improves the gloss of the product. Note: A good varnish needs to be selected when glazing. Commonly used varnishes generally include UV varnishes and water-based varnishes. In actual production, it can be selected according to product requirements, process and equipment. The UV varnish coating is thick and has high brightness, so UV curing is required after coating, and the cured product often has peculiar smell, which needs to be left for a period of time to remove. The water-based varnish coating is thin and slightly lower in brightness, and does not require a special drying device. It is generally technically possible to print in the last color.
In addition, on products printed with pearlescent ink, special visual effects can often be obtained through calendering, embossing, embossing and other processes, adding more charm to pearlescent ink printing. At present, pearlescent ink printing is not only limited to gravure printing, but also suitable for offset printing, letterpress printing, flexographic printing, screen printing and other printing methods. Substrates have also expanded from traditional paper and plastic to cloth, rubber, ceramics, car shells, and more. The color range of pearlescent pigments has been extended to silver series, gold series, rainbow series, metallic color series, etc. More and more products are printed with pearlescent ink, and the grades are getting higher and higher. With the development and breakthrough of pearlescent pigment technology, the application range of pearlescent ink printing will be further expanded, and pearlescent ink printing will bring new special effects, which will definitely add more brilliant colors to life.
