Selection of ink for screen printing of metal materials (medium)

When ordering coated metal materials from a supplier, it is necessary to clearly understand the type of coating (acrylic, polyester, etc.) on the metal and to confirm whether the coating material contains a smoothing agent that can cause the ink to adhere. Other surfactants. If surfactants are included, suppliers should recommend to printers cleaners that can safely remove these contaminants before printing.
Ink-based and UV-curable inks that meet metal screen printing requirements can be used to decorate coated metal materials, but the use of solvent-based inks is more common. Although technical advancements have allowed UV-curable inks to be used on a wide range of metallic materials, their chemical composition and cure characteristics still limit the range of applications and appear to be inferior to solvent-based inks.
Solvent-based inks for metal printing typically have 2 dry forms: one is air-dried (by evaporation) and the other is heat-cured (chemically hardened or cross-linked).
Air-dried inks are generally used for vinyl, acrylic, or lacquer-effect products. These inks do not chemically react during drying, so they are easily scratched and abraded and cannot resist the attack of solvents, gasoline, and cleaning solutions. If it is not completely dry, the ink film will appear agglomeration problems. Because metal is a relatively heavy substrate, if the phenomenon of ink agglomeration occurs on the metal, it will bring about certain problems. At present, many air-dried inks give prints good flexibility and excellent outdoor durability.
Solvent-based inks that use thermosetting drying methods usually contain some form of epoxy, enamel, polyester, or acrylic (epoxy components are very suitable for thermosetting inks that require high outdoor durability). All of these inks require long-term drying at higher temperatures. After curing, the ink film is very hard, so they are stronger than air-dried inks. They not only resist the corrosion of solvents, gasoline, and cleaning solutions, but also avoid Scratches and wear. Of course, these inks are inferior to air-dried inks in terms of flexibility, but they are suitable for hot embossing or deformation. If a suitable curing and cooling process is performed prior to stacking, prints produced with thermosetting solvent inks will not exhibit ink agglomeration.
UV curable inks for metal printing are also divided into two types: cationic and free radical (acrylate). The main chemical component of cationic UV-curable inks is epoxy resin. This ink system cures at a slower rate than conventional free radical systems. The main component of the latter is acrylic resin. If properly processed, both ink systems can provide good outdoor durability for prints. Both cationic and radical UV-curable inks are chemically reactive, producing a stiff ink film during curing that not only resists abrasion and chemical attack, but also has the same flexibility as thermoset solvent inks.
Match the ink and print performance requirements Regardless of the type of ink chosen for metal printing, this ink should be able to meet the specific performance requirements of the print. For example, the ink film formed by the screen printing ink not only has a certain hardness, so as to resist problems such as abrasion, scratches, ink accumulation and solvent erosion, but also has enough flexibility to facilitate people to bend and mold the printed matter. Cut and press the bumps. There will not be an ink and a metal substrate that will satisfy all your production requirements. Instead, you will need to perform different coating treatments on the metal, while also matching the ink system with the different coating materials and the end use of the product. match.
For example, if the product is used indoors, it is very suitable for epoxy type inks, other resin-based heat-curing inks are also available; if the product does not need to have solvent resistance, then the use of air-drying solvent-based ink is sufficient However, if prints need both corrosion resistance and outdoor durability, air-drying and epoxy-based solvent inks are not ideal, but other traditional heat-curable or UV-curable inks can be used in this area. When selecting the type of ink, the first task is to ensure that the ink film adheres to the substrate after drying or curing, and that different types of inks are selected according to different materials.
Why is the choice of ink so important for metal printing? This is closely related to the metal coating process. If the metal coating is thermoplastic, many inks can adhere to it. However, if the coating is thermoset (most thermosetting inks are used in most screen printing), the use of any type of screen printing ink is difficult and requires strict and regular monitoring of the entire production process.
The difficulty in printing on metals with a thermosetting coating is that the hardness of these coatings is high, and the hardness of the thermosetting coating is affected by the resin system, the coating method, and the way the coating is cured. The higher the temperature of the curing process and the longer it lasts, the harder the coating surface is, and the harder the surface, the harder it is for the ink to adhere to the coating. The higher surface hardness is the reason why it is difficult for a screen printing factory to print UV-curing inks on metallic materials.