Selecting inks for screen printing on metallic materials (1)

Editor's note: This article will give you an idea of ​​how ordinary coating on metallic materials can be used to visualize the final printing effect, and why you need to carefully select the ink before proceeding to production.

Among all the features of screen printing, the durability of screen printing ink is the most important one. Moreover, screen printing is also a popular decoration method. Both solvent-based and UV-curable inks can impart rich colors to prints while also helping them to avoid being damaged during handling, as well as being subject to wear, fading, and other environmental factors. The use of screen printing inks with these functions in combination with highly durable substrates can bring us excellent prints with outstanding performance.

Many high-performance screen printing products have the characteristics of printing on metallic materials such as steel and aluminum. Metal logos, signage, appliance signs and decorations, containers and many other printed products, these products generally have many images and logos printed with screen-printing inks. But the production of such prints is indeed a huge challenge for screen printers that do not have the experience of printing on metal.

When you want to print on metallic materials, your homework must be done well. To understand the nature of the coatings on metallic materials, the production tolerances of these materials, and the best combination of ink/substrate, this plays a decisive role in the success or failure of printing. To make effective use of these materials, printers must first understand the main properties of these metal materials. In addition, screen printing inks suitable for different materials and different image requirements are also to be found.

Understanding metal substrates

Normally, when we talk about printing on metal, the metal we refer to is actually not an unprocessed metal material. Moreover, most screen printing processes involving metals are printed on coated or treated metal materials. The coating on metal is roughly divided into two types: thermoplastic materials or thermosetting resins.

Thermoplastic coating does not undergo chemical reactions during the drying of the substrate. The drying of the thermoplastic coating is completely achieved by evaporation or heating. During the heating process, the coating material can be fused with the metal. In the thermoplastic coating of metallic materials, it must be remembered that this coating does not resist the corrosion of high temperatures and aggressive solvents. In other words, the coating on the metal melts again if it encounters a high temperature or aggressive solvent during screen printing.

Thermosetting resin coatings are generally cured by chemical reactions called "polymerization" and/or "crosslinking." The coating can be dried by heating the coated metal with a high temperature for a long period of time. Thermoset coatings are resistant to high temperatures and re-melting, but also have high resistance to solvent corrosion and wear.

Resin systems that can be used as metal-coated base materials are ethylene (plastisol or solution systems), polyester or acrylic, and the like. The vinyl coating is thermoplastic. Although it is softer than the thermosetting coating and it is easier for the ink to adhere, the thermoplastic coating has little resistance to chemicals or abrasion, which makes them in multiple screen printing applications. It is restricted. Therefore, screen printers prefer to use metal substrates with thermosetting coatings.

Polyester and acrylic are the most common resins in thermosetting coatings. Thermosetting coatings, unlike flexible thermoplastic coatings, do not dissolve screen-printing inks, but instead have a stronger cross-linking effect, making it difficult for ink to adhere to the coating.

When ordering coated metal materials from a supplier, you must ensure that the materials you ordered are suitable for use on metals (acrylic, polyester, etc.), and make sure that the coating material contains The ink is adhering to a slip agent or other surfactant. If such surfactants are included, suppliers should recommend to printers cleaners that can safely remove these contaminants before printing.