Ink anti-counterfeiting technology in ticket printing (medium)

The binder is the fluid component of the ink: the fluidity, viscosity, dryness, printing properties, etc. of the ink are all mainly determined by the binder. The linking material of magnetic ink is similar to the linking material of general ink, and vegetable oil, animal oil, and mineral oil can be used, but more synthetic resin binders are used. In order to achieve fast drying, bright light and good printing performance, the content of the resin in the linking material is higher and the fixing is faster so that more linking material remains on the surface. This requires the link material to have good water resistance and pigment wetting, otherwise it can not make ink with good printing performance.
Filler can reduce the amount of pigment in the magnetic ink, reduce the cost, and can adjust the properties of the ink, such as thick, fluidity, etc., also improves the flexibility of formula design.
2. The printability of the magnetic ink The link material of the magnetic ink is the same as the general ink, and the link material mainly affects the printability of the ink, so in principle, the flat print, the convex print, the gravure, the silk screen, Flexo can be printed with magnetic ink. For different printing methods, the selected magnetic ink may be different, but the characteristics of magnetic pigments are basically the same, and the difference is mainly the link material, and the proportion of the components in the ink formulation may also be different.
When using lithography, fountain solution is usually used. Magnetic inks, which are the main constituent of magnetic inks, are generally hydrophilic, and are prone to emulsification. Special consideration should be given to this. The general approach to reduce the emulsification of such pigments is to properly adjust the pigment with a resin. In general, the magnetic pigment has a large specific gravity and its content must be quite large, so the affinity of the binder and the pigment must be good.
Second, thermal ink Thermosensitive ink is a kind of special ink that can change the color of the pigment with the change of temperature, that is, it shows different colors at different temperatures, also known as temperature-induced color change ink.
1. Thermal ink 1 Composition of thermal ink
The composition of the ink includes color changing pigments, fillers, and binders. The color change of the ink caused by heat mainly depends on the color changing pigments, because the color change before and after the heating of these pigments is very different, and as a basis for determining whether the ticket is forged. It is well known that the variety of pigments undergoing color change due to heat is too numerous to mention, but the pigment used as a thermal ink must have the following conditions: be sensitive to heat, have a fixed color at room temperature, and change rapidly when reaching a predetermined temperature; There are obvious limits of discoloration, that is, the temperature range of color change is narrow, and the color difference before and after the color change is large; it is less affected by the external environment, and the performance is stable under the light and humid weather conditions without decomposition or fading.
The filler is present in the thermal ink as an auxiliary material, and some fillers allow the ink film to be bright, stable, uniform in color, adjust the discoloration temperature of the color pigment and improve the adhesion of the ink layer. In addition, the type and amount of filler have an effect on the discoloration properties of the thermal ink. The reason is that under the effect of temperature, certain activating elements can play a catalytic or inhibitory role on the color changing pigments, leading to a higher or lower discoloration temperature. The effect of this should be taken into account when preparing thermal inks.
The binder is also an important part of the thermal ink: it requires good temperature resistance, strong adhesion, light color and should not react with pigment components. The type and amount of resin have different effects on the color temperature. Therefore, the thermal ink binder should be selected according to the comprehensive performance of the ink.
2 Printability of Thermosensitive Inks Thermal inks are commonly used for screen printing, gravure printing, and flexo printing. Anything that requires the use of temperature-sensitive printing materials can be screen printing, especially for small quantities, but there are some special shapes of the substrate; also pay attention to the relationship between the thickness of the ink layer and the effect of temperature change, but also Consider the viscosity, volatility, etc. of the ink because these characteristics affect the printing process. Also affect the color effect; print dry carefully, it is best not heated. Gravure printing should use 175 lines / in, the depth of the same general gravure printing plate; should not use copper plate printing, should not be printed directly on the aluminum foil, need cold air drying, heating should be moderate, so as not to destroy the color properties can not be restored.
For substrates with large batch sizes, which do not cause their own deformation or the like due to high temperature (such as paper), and substrates that do not have a very sensitive thermochromic effect, flexible printing should be used.
2. Liquid-crystal inks Liquid-crystal inks are currently the technologies that people are most interested in and are difficult to master, mainly due to changes in the optical properties caused by changes in the crystal lattice. In terms of production methods, it belongs to the microcapsule structure ink type, but in terms of characteristics, it is mainly the use of liquid crystal thermochromic characteristics. (To be continued)