Application of pearlescent ink in wrapping paper printing

4 Pearlescent ink application

Pearlescent printing has a history of several decades and it is suitable for almost all kinds of printing. Pearlescent printing can be used for various substrates. The products are mainly used in the packaging and printing of goods, such as soap packaging paper, wallpaper, cigarette boxes, food packaging paper, film printing such as OPP, PET, PE, PS and so on.

Common printing methods include letterpress printing, gravure printing, flexographic printing, and screen printing.

4.1 Letterpress and flexo printing

The pearlescent pigments used in letterpress and flexo printing have low viscosity coefficients between 20-60 centipoises; there is no limit to the type of solvent used. Flexo printing is increasingly favored by many printers because it is more environmentally friendly. In the flexographic printing process should be controlled pearlescent ink viscosity between 40-60s, if you need to adjust the ink viscosity during the printing process, you can use a mixture of water and isopropyl alcohol (the best ratio of 1:2).

4.2 Gravure Printing

Like gravure and flexo printing, gravure also uses low-viscosity inks. The gravure printing needs to pay attention to the uneven printing of pearlescent ink. This is due to the high viscosity of the pearlescent ink, which makes it difficult to apply evenly, and the phenomenon caused by ink layer unevenness after the imprinting. The solution is to select the appropriate diluent to reduce the viscosity of the ink.

4.3 Screen Printing

For screen printing, in order to prevent the clogging of the mesh, the screen mesh size should generally be two times larger than that of the largest pearlescent pigment, so as to ensure the adaptability of the printing.

5 Cautions for use

Now some advanced print and packaging materials (such as paper and polyethylene plastic film, etc.), commonly used pearlescent pigment as a colorant for printing. Pearlescent pigments can show pearl-like brilliance "8" on prints. The use of pearlescent pigments is similar to the use of metallic pigments. However, the pearlescent pigments have different physical and chemical properties when compared with metallic pigments. Therefore, the characteristics of pearlescent pigments need to be considered when printing. The following factors should be considered in the process:

Since pearlescent inks will continue to deposit after dilution, the concentration of pearlescent pigments is usually between 15% and 25% of the finished ink (but due to different printing methods and effects need to adjust the amount of addition); because the average specific gravity is 3, long-term deposition will make the pearl powder adhere to each other, can not be used, so the ink tank should be ready to use, diluted pearlescent ink storage is best not more than 7 days. After a few days, the storage tank should be shaken and shaken evenly to make the ink cycle as much as possible to avoid sedimentation.

Also note that in the production process, pearlescent pigments will also be deposited, so ink tanks should be placed as little as possible ink. In the printing materials, the substrates require high smoothness and good gloss. Glass cardboard, polished paper, coated paper, and sizing paper are preferred.

6 Pearlescent Ink Progress

Recently, a series of pearl-based pigments developed by different coating methods has taken a big step towards the development of pearlescent inks.

From the point of view of the luster effect of pearlescent inks, from the previous single pearlescent effect, it can now show a bright silver luster, a neon-like illusion effect, a golden luster similar to metallic pigments, and a bronze and copper color. Such as rich light color changes "8-10". The surface of the product covered with a layer of varnish, not only can perfectly protect the ink layer, but also the finishing touch, icing on the cake.

From the point of view of the chemical properties of pearlescent inks, it exhibits excellent resistance to strong light, high temperature, and corrosive chemical environments. On the other hand, stable chemical properties make it comply with FDA's strict regulations in food packaging products. .

In addition, as a special glossy spot color pigment, pearlescent pigments that have been developed are easy to combine with commonly used solvent-based or water-based media, making pearlescent inks exhibit strong stability. And it is easy to operate and will not cause environmental pollution.

In the packaging paper printing industry, pearlescent ink printing is currently in a dynamic growth trend. The market has great potential for development and the development space is extremely broad. Therefore, Pearlescent ink printing is promising both from the process itself and from a technical point of view.

(Author/Lee or Huang Dexing Wang Ximao Ye Yong)

"Packaging Project"