2. Magnetic ink
Magnetic ink anti-counterfeiting principle is the use of magnetic colorants, such as iron oxide or iron oxide added cobalt and other chemical substances, the use of magnetic detection detector detects the magnetic signal and decoding. Magnetic is produced by the magnetic pigment contained in the ink. The best magnetic pigments are Fe3O4 (black) and Fe2O3 (brown). Most of these pigments are needle-like crystals smaller than micrometers. The size and shape of these particles make them extremely easy to arrange in the magnetic field and obtain relatively high residual magnetism. This kind of residual magnetism is symbolized and digitally processed inside the automatic processing device. The friction function realizes the discrimination function. The binder for magnetic ink is generally an alkyd resin. Other pigments can also be added to obtain different colors of ink. The most prominent feature of magnetic ink is the deep color appearance and simple detection equipment.
3. Thermochromic ink
Thermochromic ink, also called temperature-sensitive ink, is a special ink that can change color with temperature. The anti-counterfeit principle of the thermal ink is that the color material uses a substance whose color changes with temperature. In recent years, some research institutes and manufacturers at home and abroad have successively developed thermochromic inks with different characteristics. Now, there are three types of thermochromic inks: color reversible, color irreversible, and memory. Reversible type: When the thermochromic discoloration occurs, the heat source can be restored to its original shape once the color of the ink is removed. The type of discoloration can be divided into sublimation, melting, thermal decomposition, oxidation, and curing reactions, mainly due to loss of water after crystallization or pH change. The value changes and changes color, so when the heat source is eliminated, it can be restored to its original state. The irreversible type is that when the color changing pigment in the printing ink is heated, a physical or chemical change occurs, the original physical and chemical properties are changed, and thus the color change occurs. Therefore, the color of the ink cannot be restored to the original color when the heat source is withdrawn. Memory type has memory function.
Thermochromic inks can be used for screen printing, gravure printing, and flexo printing, especially for screen printing. Screen printing is suitable for printing materials of any shape, especially for substrates with small batches but special shapes. When printing thermochromic inks, attention should be paid to the relationship between the thickness of the ink layer and the effect of temperature-sensitive color change, and at the same time, the viscosity, volatility, etc. of the ink must also be considered because these characteristics affect not only the printing process but also the color rendering effect; Drying should be careful, it is best not to use heat drying method, in addition thermal ink is not suitable for direct printing on aluminum foil material.
4. Photochromic ink
Photochromic inks, also called photochromic inks, are photochromic or photoactive compounds that are added to the ink. In the sun, the ink can change from colorless to colored, or from orange to black, etc., and can generally be divided into common type and UV type. . Ordinary type means that under the effect of ordinary daylight and strong light, the color of the ink will change, and it will return to its original shape after leaving the light source. It looks like it is discolored under the sun, and it is essentially changed by ultraviolet irradiation. The color changing wavelength is 400 to 800 nm. The application of this kind of ink in packaging and decoration not only can improve the grade of goods, increase interest, but also highlight the anti-counterfeiting effect. UV type ink is colorless or does not change color under the irradiation of ordinary light sources, but it will show bright red, orange, yellow, green and green fluorescence under UV light (UV light) irradiation. Most large denomination banknotes are printed using this kind of ink, and authenticity can be revealed under the effect of a counterfeit money detector.
In screen printing, thermochromic and photochromic inks can be transferred to different substrates, such as paper, cloth, nylon, plastic, metal, glass, ceramics, etc., by screen printing. It has the characteristics of sensitive to external conditions, obvious changes and rapid recovery. It is the ideal material for anti-counterfeiting technology and interesting gifts. It has broad development and application value.
5. Fluorescent ink
The fluorescent ink is made of a fluorescent material dissolved in the corresponding resin. Fluorescent pigments are generally coarser particles, and the types of binders are also more. Different binders will produce different fluorescence. When using fluorescent inks, it should be ensured that it has sufficient concentration, and the ink layer on the prints is a little thicker. Satisfactory fluorescence effect is guaranteed. Fluorescent inks are printed brightly after screen printing, and the decorating effect is very good. Under the action of visible light and ultraviolet rays, it can give off glittering fluorescence. Fluorescent ink can be self-aligned, different formulations can get different fluorescence effects, and its anti-counterfeiting effect is better. However, fluorescent inks have poor light resistance, and prints used outdoors are not effective.
6. Storage and Phosphorescent Inks
The light-storing pigments are prepared using certain zinc sulfide/copper phosphors, calcium sulfide/germanium phosphors, etc. having a phosphorescent effect in inorganic phosphors. Inorganic fluorescent substances are generated by crystals. If the crystals are broken due to pressurization, resulting in reduced luminosity, screen printing is generally suitable. Ink carriers and fluorescent substances are mixed during use. Phosphorescent inks are characterized by the ability to absorb light and emit light at a certain wavelength within a certain period of time. The pigment of this ink is a zinc sulfide containing a small amount of impurities (such as cadmium zinc sulfide), which is afraid of acid and alkali, and therefore requires neutral resins such as cyclohexanone resin, cellulose ester and ether. In addition, heavy metals, desiccants, and drying oils should not be added to the ink to avoid damaging the pigment material. The link material used requires transparency and UV light transmission. This type of ink is mainly used for printing advertisements, signage, etc. However, if phosphorescent inks and fluorescent inks are used in anti-counterfeit packaging printing, they can receive very good packaging decoration and anti-counterfeiting effects.
7. Printing ink
The printing ink is mainly composed of pigments, fillers, binders, etc. The choice of pigments is an important step in determining the hue and vividness of printed products. Many manufacturers and ink manufacturers have customized special inks for printing of each product. Its formula is kept confidential by the ink factory. For example, the “China†and “Peony†cigarettes produced by the Shanghai Cigarette Factory are printed with special inks that are specially customized at the Shanghai ink factory. This type of ink does not know that the detailed formula is difficult to tune, and therefore has a better anti-counterfeit effect.
8. Composite ink
After mixing two or more anti-counterfeit inks in a certain proportion, composite inks with new properties can be developed. If the ink formulations are not fully understood, it will be difficult to imitate them.
9. Other security screen printing ink
Plastic security ink. Applicable to PP, PVC, PE, PS, ABS, PC and other plastic products, with 150 to 200 mesh polyester network, per kilogram of ink can be printed 20 ~ 30m2, natural drying or drying at 130 °C for 3min. Metal, glass, ceramic security ink. Suitable for printing on metal temperature signs, color changing glass ware, color changing milk cups and ceramic tea sets, etc., with 70 to 100 mesh polyester mesh, 10-20 m2 per kilogram of ink, and drying conditions of 25°C, 48h or 120°C, 45min. Glass, ceramic decal transfer paper security special ink. Applicable to the printing of glass and ceramic decals, with 150 to 200 mesh polyester webs, and the drying conditions are 200°C and 20 minutes after water transfer. Water-based security inks and printing pastes. Applicable to printing on paper, cotton, knitted fabrics, T-shirts, sportswear, etc., with 80 to 150 mesh polyester mesh, each kilogram of ink can be printed about 20m2 (cotton fabric will be less than this number), drying conditions for 130 °C, 3min.
Third, anti-counterfeiting screen printing process
With the development of high technology and people's demand for high-quality packaging products, the packaging and printing industry has carried out a wide range of technological revolutions in recent years. Multiple printing equipments have been used in combination with each other, and multiple printing processes have infiltrated each other to make printing products more Unpredictable, colorful, and set obstacles for trying to be fake. 〉〉True and fake identification - Thousands of product identification methods
1. Combination printing anti-counterfeiting
Combined printing is a combination of several different printing methods on a single press to meet different customer requirements. Practice has proved that combined printing can not only play a complementary role, but also create new printing effects and enhance anti-counterfeit effects. At present, screen printing is one of the key components in combination printing. It is mainly combined with flexographic printing and flat printing to play a role in security printing such as packaging and decoration.
(1) Flexo and rotary screen printing. Screen printing can show the effect of highlighting by virtue of its thick ink layer and ink layer can be adjusted. At present, the rotary screen printing unit with extremely high printing precision is printed with a flexographic printing press, which makes its application in anti-counterfeit printing more extensive. To sum up, there are the following prominent features:
1 enhance the attractiveness of the product, if the product needs to be more expressive, you can also take the effect of empty design, and then use strong colors or light and other special ink printing, to achieve the desired effect;
2 When printing the indicative signs for specific groups of people (such as the blind, etc.), adopting this printing method can also achieve the desired effect;
3 It is suitable for printing special substrates (such as greeting cards, pictures, books and magazine covers, etc.) with metallic effects such as gold and silver;
4 Applicable to exquisite packaging and decoration printing, such as the appearance of embossing, frosted and other special effects;
5 can print a large area of ​​the field and anti-white;
6 cooperate with the use of optical variable screen, temperature change screen ink, but also improve the security features of valuable tickets, high-grade trademarks;
7 Combination printing can also be used for the printing of batteries, paint labels, etc.
8 Products that need to emphasize product branding and labeling, such as drug labeling and injections. At present, EM series flexographic printing presses are mainly used for packaging and printing. More than 90% of the models have been requested by users to be equipped with a rotary screen printing unit.
(2) flat screen printing combination printing. General high-end packaging and decorating printed products are designed with a large area of ​​color, multi-color sequence of continuous adjustment of complex lines, patterns, etc., to a single printing method has brought a certain degree of difficulty. However, if the combination of plain printing and screen printing can be used to solve this problem, it will make full use of the screen printing machine to print large areas of solid color with a thick and uniform ink, while using the advantages of flat press printing pressure. The four-color and complex lines clearly improve the quality of printed matter and enhance its anti-counterfeiting effect. In addition, for some more demanding and more complex print products, multiple processes such as flat, convex, and gravure printing can be used. Not only does the printing work well, but the anti-counterfeiting effect is also very significant. In short, the more complex the printing process, the greater the difficulty of printing the packaging decoration, the better the anti-counterfeiting effect.
2. Multi-color printing security
Multi-color printing is also called cross-color printing. The screen printing method is based on the requirement that, after the partition is placed in the screen frame, a plurality of hue inks are added, and the ink of the adjacent portion is mixed under the force of the scraper. A print process that leaks onto the substrate. It can be printed in a variety of colors at once, and the middle transition level is soft. Since it is difficult to see from the prints the distance separating the partitions within the screen, it can also play a security role. If such a process is used on a large area of ​​shading, its anti-counterfeiting effect will be more prominent.
3. Hand-carved typesetting anti-counterfeiting
Screen-printed hand-engraved plates are somewhat similar to gravure-engraved plates, and different carving styles can achieve anti-counterfeiting. Indirect plate-making method using screen printing, first film film engraving, and then posted on the screen plate. For example, when carving the word “mouthâ€, the center of the mouth can be carved into a circle to form the shape of the outer circle of the inner circle, and this shape can be seen only by looking closely or under a magnifying glass so as to realize anti-counterfeiting. Using the revised technology for anti-counterfeiting can also achieve the same goal and reduce the cost of plate making.
4. Special gloss security printing
Special gloss refers to the products printed by this process. The surface gloss effect is different from the gloss effect reflected by common ink or printing paper. It is a new type of printing technology that is popular in the packaging printing industry in recent years. The special glossy printing process currently includes the following types:
1 metallic glossy printing. Adopt aluminum foil metal composite paper, use screen printing transparent ink, make the printing product to form a special metallic luster effect;
2 pearl printing. Silver paste is first deposited on the surface of the printed material, followed by a very transparent ink, and the silver paste glitters through the ink layer to show a pearlescent effect;
3 pearl glossy printing. The use of inks incorporating mica particles produces a glossy effect on pearls like shellfish and shellfish;
4 refraction printing. The use of a refraction printing plate to produce a unique effect of glow refraction on a print by a certain pressure;
5 Matt printing. Use matte ink or ordinary