There are 6 types of pad printing ink. The ink specially used for pad printing is different from general solvent ink, water-based ink and UV curing screen printing ink. Although pad printing ink and screen printing ink have some similar characteristics, they are still very different. Different from silk screen printing ink, the drying speed of pad printing ink is faster, which is also a prominent feature of pad printing ink. At the same time, pad printing ink is often printed on thin film. This use makes pad printing ink vulnerable to some factors such as temperature, humidity and static electricity. The ink specially prepared for pad printing includes single component ink, two-component ink, drying ink, oxidation ink and sublimation ink.
One component ink. The drying of one component ink (also known as solvent volatile ink) depends on solvent volatilization. This kind of ink does not have to add a catalyst. One component inks are glossy and non glossy. They are mainly used for the printing of plastic substrates.
Two component ink. Two component ink is also called chemical reaction ink. Catalyst must be added before printing. The catalyst reacts with the resin in the ink to achieve the purpose of ink drying through polymerization. When two-component ink is used in pad printing, it is necessary to add a certain ratio of catalyst, usually measured by weight. The addition ratio of catalyst must be strictly controlled. Adding too much will greatly shorten the "adaptation period" of ink; If you add too little, you may not achieve good drying performance when the ink is dry. Generally speaking, if the proportion of ink and catalyst is improper, it will lead to printing defects such as uneven ink adhesion and insufficient durability of printed images.
Drying ink, drying ink is divided into two types: one is to add another catalyst on the basis of standard two-component ink; The other is the ink specially prepared for substrates such as glass, ceramics and metals. Just like its name, the drying ink must be heated and dried at a certain temperature. When using this ink, the drying time should be calculated. The higher the temperature, the shorter the drying time. However, too high drying temperature will make the ink film brittle. Therefore, the ink should be dried at a temperature that can maintain the flexibility of the ink.
Oxidation type ink, oxidation type ink absorbs oxygen in the surrounding environment for polymerization reaction to form ink film without adding catalyst. Typical applications of oxidized inks are flexible packaging substrates and synthetic substrates, such as rubber products or keyboards. Due to the slow drying speed and long time of oxidation ink, the use amount is limited.
Sublimation ink, sublimation ink needs special processing in the use process, that is, it needs to be heated after printing to make the substrate porous. In this way, when the dye contacts the heated substrate surface, the dye in the ink becomes gaseous, and then enters the substrate surface, which actually changes the surface color of the substrate. Once the substrate cools, the ink sticks to the surface of the substrate. The more common applications of sublimation ink are computer keyboard printing and printing materials with high requirements for oil resistance and wear resistance, which can not be achieved by using two-component ink. In particular, it is worth noting that the sublimation ink actually changes the surface color of the substrate, so the matching between the substrate and the ink color is more difficult. Therefore, the color of the substrate must be lighter than the required color after printing, because the color change of sublimation ink on the surface of the substrate with darker color is often less obvious.
Special inks and additives. Pad printing special inks include edible inks, silicone resin inks, lubricating inks, corrosion-resistant inks, conductive inks and UV curing inks. The ability of these inks to quickly become sticky will determine whether they can effectively transfer the ink to the substrate surface. At the same time, in order to adjust the printability and performance of ink, in addition to adding solvent and catalyst, many additives may be used, such as viscosity inking agent, antistatic agent, rheological agent, etc. However, the use of additives will have a great impact on the printing performance of ink, so we must be careful when using them.