Printing Ink

Pad printing ink is a special ink for pad printing machines.

Features
• Good transferability: suitable viscosity and surface tension, easy to peel off from the pad printing silicone head, transfer to the surface of the substrate, and ensure the complete transfer of the pattern.

• Rich and stable colors: provide a wide range of color options, and the colors can remain bright and fade-free for a long time after printing, with good light resistance and chemical stability.

Ingredients

• Pigment: determines the color of the ink, and the quality of the pigment affects the hiding power, light resistance and other properties of the ink. For example, the use of high-quality organic pigments can make the printed color bright and long-lasting.

• Binder: mainly plays the role of bonding pigments, and at the same time affects the drying speed, adhesion and other characteristics of the ink. For example, resin binders can make the ink adhere better to the substrate.

• Solvent or diluent: used to adjust the viscosity of the ink to meet the requirements of pad printing. Different solvents also affect the drying method and speed of the ink.

Application areas

• Toy industry: used to print patterns, logos and decorative patterns on the surface of various toys. The facial features of plastic dolls and the logos of toy cars are all printed with pad printing inks.

• Electronics industry: Printing brand logos, models, patterns and other information on the shells of electronic products. For example, mobile phone cases, computer mice and other products, pad printing inks can achieve fine pattern printing.

• Household goods industry: Used for surface printing of household decorations, tableware, stationery and other items. For example, printing exquisite patterns on ceramic vases, or printing trademarks on plastic stationery.

 Classification by drying method

• Solvent-based pad printing ink:
Mainly relies on solvent evaporation to dry. The drying speed can be adjusted by adding slow-drying solvents or fast-drying solvents. Generally, pad printing ink dries faster and can be dried naturally or with IR tunnel furnaces.

• UV pad printing ink:
Although the ink layer of pad printing ink is thin, it has strong covering power, so the color concentration of pad printing ink is high, which is bound to affect the penetration of UV light, so UV pad printing ink has been progressing slowly. Through the research of ink engineers, UV pad printing ink is now basically mature and has been maturely applied on ABS materials.
Under ultraviolet light, the photoinitiator in the ink will trigger a polymerization reaction, causing the ink to solidify instantly. Since there is almost no solvent volatilization, the environmental protection performance is good. It is often used for pad printing of high-precision products that need to be produced quickly, such as mobile phone shells, high-end cosmetic bottles, etc.

UV pad printing ink need UV curing unit to dry

   The process of pad printing ink transfer is briefly described as follows: first pour the oil pan into the oil pan, and then the ink will be coated on the surface of the printing plate driven by the inking device; the scraper will scrape off the ink coated on the surface of the printing plate, as shown in the figure The ink in the text will remain in the pit; the pad printing head moves to the top of the printing plate to stick the ink in the pit of the printing plate; the pad printing rubber head moves to the substrate to print the ink on the product surface.
The process of pad printing ink filling the pits of the printing plate requires that the pad printing ink has good fluidity and cannot be dried before the pad printing rubber head is dipped; after the ink is dipped by the pad printing head, it must be ensured that the ink has sufficient plasticity, that is, the ink cannot There are changes in form. The transfer of ink on the surface of the rubber head is similar to the release state of the thermal transfer film, which must be completely transferred without major changes.
Pad printing ink requirements:
1. Fast and stable drying. Compared with screen printing ink, the drying speed of pad printing ink is faster. If the drying speed is too slow, the transferability will be affected, but this is relative. If the drying speed is too fast, the ink will dry on the printing plate. deep. In addition, it is very important for the pad printing ink to have a more stable drying speed range. When the ink is brought from the oil pan into the printing plate, transferred to the surface of the rubber head, and printed on the surface of the product, the amount of ink transferred is very small. To ensure the stability of printing suitability, the ink must maintain a stable drying speed, so the purity of the solvent in the pad printing ink should be higher than that of the screen printing ink.
2. The color concentration of pad printing ink is higher. The ink layer of pad printing ink is similar to that of offset printing. In order to obtain brighter colors, the color concentration of the pigment in the ink must be high, but too high a color concentration means that the adhesion will decrease. Obviously, we will have to refine the molecules of the pigment And choose better resin to make up for this deficiency.
3. Pad printing ink has more stable colloidal properties. Ink is a kind of suspension, and it will appear delamination when it is left for a long time. A uniform amount of ink is obtained on the head surface, which is similar to offset printing ink properties.