Tinplate printing uses offset lithography technology. Based on the physical principle that ink and water repel each other, the image and text are transferred to the tinplate surface through printing pressure and rubber cloth. Due to the unique physical and chemical properties and reprocessing performance of tinplate, its printing process is significantly different from ordinary offset printing.

Tinplate printing has special requirements for ink, as follows:

1. Adhesion and mechanical properties of ink

The printed tinplate needs to go through processing steps such as cutting, bending and stretching, so the ink is required to have excellent adhesion and mechanical properties. In order to enhance the adhesion of ink, tinplate needs to be primed with white before printing. White is the basic color of all patterns, with high brightness. After mixing with other high-energy hues, it can enhance the brightness of the overall color and form a rich color layer.

2. Characteristics of white ink

In order to make the tinplate surface appear silver (or yellow) and retain the metallic luster, glazing treatment is required before printing. Due to the limitation of ink coverage, single color usually needs to be glazed twice, and the whiteness can reach 75%. Whiteness is one of the key factors to measure the quality of tinplate printing. It requires that the white ink and the base ink have good bonding strength, and will not turn yellow or discolor even after multiple high-temperature baking and boiling. Applying the base ink can enhance the adhesion of tinplate, so that the white ink can be better attached. The commonly used base ink is epoxy amine, which is characterized by light color, no yellowing and aging after multiple baking, and excellent processing properties such as flexibility and impact resistance.

3. Requirements for color ink

The color ink used for tinplate printing not only needs to have a certain degree of water resistance, but also other special properties. Since the surface of tinplate does not absorb water and solvents, the ink needs to be dried by baking, so thermosetting ink must be used to meet the requirements of high coloring power and durability. In addition to the basic properties of general offset printing inks, tinplate inks must also have characteristics such as heat resistance, strong ink film adhesion, impact resistance, high hardness, boiling resistance and light resistance.

4. Drying process of ink

In tinplate printing, ink drying is a complex physical and chemical reaction process. Reasonable control of the speed and diffusion mechanism of ink drying is the key to ensure printing quality and efficiency. If the ink dries too fast, the transmission performance of the ink will be reduced, resulting in hollow drums, light color and other problems during printing. The dried ink on the plate roller and the printing plate will hinder the ink transfer and expand the dry layer of the printing plate image outward. In addition, too fast drying speed will lead to excessive ink adsorption capacity, causing the blank part to be dirty.

On the other hand, too slow ink drying speed will lead to poor overprinting effect, poor adhesion, reduced firmness, and easy scratches during transmission. Therefore, the ink drying speed must be moderate, too fast or too slow will have an adverse effect on the printing quality.

5. Special structure of printing equipment

Due to the differences in printing products and materials, the auxiliary machinery of tinplate printing presses is different from that of ordinary paper offset printing presses. Tinplate is insoluble in water and does not absorb solvents. Printing ink needs to be baked at high temperature to solidify into a film, so a drying room must be equipped during the printing process. The total length of the tinplate printing automatic line is about 50 meters, which is characterized by large-scale and precision. In addition, the tinplate printing machine uses magnet slicing and double slicing control technology. Due to the high hardness of tinplate, the continuous conveying system cannot be used during the printing process, so there are significant differences in the structure of the paper feeding section, alignment system and stacking section from the paper offset printing machine.

As a professional tin box manufacturer, Tengda can efficiently complete tinplate printing tasks with advanced printing technology and equipment to ensure product quality and performance.