Screen printing design in the most popular anti-co

Printing design in anti-counterfeiting packaging printing (II)

II. Anti counterfeiting ink in anti-counterfeiting packaging printing

at present, there are many kinds of anti-counterfeiting inks developed, but according to the characteristics of printing, the most suitable inks for printing are as follows:

1. Liquid crystal ink: liquid crystal ink is a new special ink originated in the United States in the 1970s, which refers to the addition of compounds with crystalline properties to the ink. From the perspective of manufacturing method, it also belongs to the type of microcapsule structure ink. From the perspective of application, it belongs to thermochromic ink with heat sensitivity. However, from the perspective of the characteristics of liquid crystal ink, it mainly uses the characteristics of liquid crystal thermochromic ink. Liquid crystal ink is mainly composed of water-soluble resin, liquid crystal capsule, additives, binder and defoamer. It is prepared by dispersing liquid crystal and additives enclosed in microcapsules in binder. Liquid crystal inks are not frustrated that the pigments in the ink layer form color graphics and texts, but use the liquid crystal temperature sensitivity in the ink layer to cause the change of molecular direction, so as to selectively reflect the visible light of a specific wavelength, absorb the optical characteristics of light of other wavelengths, and thus show color changes. The color forming mechanism of liquid crystal is formed by its selective reflection of specific wavelength light. The molecular arrangement of liquid crystal is not as firm as the crystal structure, so it is easy to be affected by the external environment to change its optical properties. It is the notch of liquid crystal ink that is located in the opposite direction of the impact phase, which makes use of the characteristics of liquid crystal, so that the lattice of liquid crystal changes under the influence of weak current and temperature, and shows light and dark patterns and colors

the printing method of liquid crystal ink is silk printing, which makes the printed matter have reversible reaction or irreversible reaction. The key of liquid crystal printing, especially the toothed rod guide wheel and oil brush technology, is to display bright colored liquid crystals at different temperatures, and form a series of color stability temperature range values. The manufacturing technology of liquid crystal microcapsules is also the key. Microcapsules should be small and uniform, with transparent and thin capsule walls, mixed with ink, and require solvent resistance, stability, reliability, and long service life; Ensure that the liquid crystal microcapsules are not crushed during the printing process; The surface is covered with protective film, etc. The amount of liquid crystal added to the ink is 40% of the total amount of ink. The diameter of the capsule should be 10~3um. The silk used for liquid crystal ink printing generally adopts nylon silk or polyester silk. If the printing plate is required to upload a large amount of ink, it can be made of stainless steel silk. According to the requirements of ink microcapsule diameter and ink layer thickness, 100-175 days are generally selected. Because silk liquid crystal microcapsules are water-soluble, photosensitive adhesives with strong water resistance should be used in plate making

the following problems should be paid attention to when printing liquid crystal ink: A. during each printing, there should be enough ink on the printing plate, the ink should be given evenly, and it is best to replenish the ink in the middle to prevent foaming. B. Microcapsule ink is easy to block the version. If blocking and foaming are found, stop the machine immediately and thoroughly clean it with alcohol water. C. The printing pressure should be moderate. Low pressure, insufficient ink on the substrate, affecting the color effect; The pressure is too high, causing the liquid crystal capsule to rupture, thereby reducing the color effect. D. For the teacher, the hair color of the printing part is obvious, and the printing background color should be black or dark tone. Water solvent ink or organic solvent ink can be used for low color printing, and printing methods can be printing, offset printing and gravure printing. When organic solvent ink is used, it must be fully dried after printing to avoid residual oily chicken solvent in the ink film, which will react with liquid crystal and affect the color development effect. E. During the printing process, the ink layer should be smooth and bright, and the thickness should be controlled within 15~35um. F. Arrange printing colors reasonably. You can print low color with black (or dark) ink first, and then print the required pattern with liquid crystal ink; You can also print the required negative pattern with liquid crystal ink to cover it first. G. It's best not to use 40 when stacking printed matter? C around the hot air drying, avoid accelerated, heated high temperature rapid drying

in addition, don't put too much pressure on the printed matter when stacking, and try not to stack too much after drying, and don't add too much local pressure when cutting, so as to prevent the liquid crystal microcapsules from being crushed. When using liquid crystal ink, the discoloration temperature range should also be determined according to the purpose of use, and the durability of liquid crystal should be considered according to the purpose. In order to improve the wear resistance, temperature resistance, gas insulation and maintain its gloss of the ink layer surface, the surface can be coated with gloss paint or pasted with protective film

2. Magnetic ink: the anti-counterfeiting principle of magnetic ink is to use magnetic pigments, such as adding cobalt and other substances to iron oxide or iron oxide, and apply magnetic inspection pigments such as Fe3O4 (black) and Fe2O3 (brown). Most of these pigments are needle shaped crystals smaller than microns. Such particle size and size make it easy for them to be evenly arranged in the magnetic field and obtain relatively high residual magnetism. Symbols and numbers with this residual magnetism realize the recognition function through the friction in the automatic processing device. The binder of magnetic ink is usually alkyd resin. At the same time, other pigments can be added to get different colors of ink. The most prominent features of magnetic ink are deep color appearance and simple detection instrument

3. Thermochromic ink: thermochromic ink, also known as temperature sensitive ink, is a special ink that can change color with temperature change. The anti-counterfeiting principle of thermal ink is that the pigment changes with temperature. In recent years, some research sites and manufacturers at home and abroad have successively developed some thermochromic inks with different characteristics. Now there are three types of color reversible, color irreversible and memory. Reversible type, that is, when the heat source is removed, the ink color can be restored to its original state once it is removed. Its color change type can be divided into sublimation, melting, thermal decomposition, oxidation and curing reactions. It is mainly due to the transformation of crystal form after losing crystal water or color change due to pH value change. Therefore, when the heat source is removed, it can be restored to its original state. Irreversible type is when the printing ink changes color, so when the heat source is removed, the ink color cannot return to the original color. Memory type has memory function

heat sensitive color changing ink can be used for printing, concave and flexo printing, especially silk printing. Silk printing is suitable for substrate materials of any shape, especially for substrates with small batch but special shape. When printing heat sensitive color changing ink, we should pay attention to the relationship between the thickness of the ink layer and the temperature sensitive color changing effect, and also consider the viscosity and volatility of the ink, because these characteristics not only affect the printing process, but also affect the color rendering effect; The drying of printed matter should be careful, and it is best not to use heating and drying. In addition, thermal color changing ink is not suitable for direct printing on aluminum foil materials

4. Photochromic ink: photochromic ink, also known as photochromic ink, is the addition of photochromic or light activated compounds to the ink. In the sun, the ink can change from colorless to colored, or from orange to black, etc. generally, it can be divided into ordinary UV type. Ordinary type refers to that under the action of ordinary sunlight and intense light, the ink will change in color depth and return to its original state after leaving the light source. It seems to change color in the sun, but it is actually changed by ultraviolet radiation. The color changing wavelength is 400~800nm. The application of this kind of ink in packaging and decoration can not only improve the grade of goods, increase interest, but also highlight the anti-counterfeiting effect. Bright red, orange, yellow green and green fluorescence will appear under UV light (ultraviolet). General large denomination banknotes are printed with this ink, and the authenticity can be found under the action of the banknote detector

in silk printing, thermochromic and photochromic inks can be transferred to different substrates through silk printing, such as paper, cloth, nylon, plastic, metal, glass, ceramics, etc. It has the characteristics of sensitive response to external suites, obvious changes and rapid recovery. It is an ideal material for wood products to be used in anti-counterfeiting technology and interesting gifts, and has broad development and application value

5. Fluorescent ink: fluorescent humor is made by dissolving fluorescent materials in responsive resins. The particles of fluorescent pigments are generally coarse, and there are many types of connecting materials. Different connections will produce different fluorescence. When using fluorescent ink, ensure that it has sufficient concentration, and the ink layer on the print is a little behind, so as to ensure a satisfactory fluorescent effect. After printing, the fluorescent ink has bright colors and good decoration effect. Under the action of visible light and ultraviolet light, it can emit glittering fluorescence. Fluorescent ink can be mixed by itself. Different formulas can get different fluorescent effects, and its anti-counterfeiting effect is better. However, fluorescent ink has poor light resistance, and the effect of outdoor printing is not good

6. Light storage and phosphorescence inks: light storage pigments are prepared by using some zinc sulfide/copper phosphors and calcium sulfide/bismuth phosphors with phosphorescence effect in inorganic phosphors. Inorganic fluorescents emit light by crystals. If they are pressurized, the crystals will break and the luminosity will be reduced. Therefore, it is generally appropriate to use silk printing. The carrier of ink and fluorescents are mixed during use. The characteristic of phosphorescent ink is that it can absorb light and emit light with a certain wavelength within a certain period of time. The pigment of this ink is zinc sulfide (such as zinc cadmium sulfide) containing a small amount of impurities. It is afraid of acid and alkali. Therefore, neutral resins such as cyclohexanone resin, fiber fat and ether are required. In addition, heavy metals, desiccants and dry oils should not be added to the ink to avoid damaging pigment substances. The connecting material used should be transparent and can pass through ultraviolet light. This kind of ink is mainly used for printing advertisements and signs, but if phosphorescent ink and fluorescent ink are mixed for anti-counterfeiting packaging and printing, good packaging decoration and anti-counterfeiting effects can be achieved

7. Special printing ink: printing ink is mainly composed of pigments, fillers, binders and so on. The composition selection of pigments is an important link to determine the hue and brightness of prints. Many manufacturers and ink factories have customized the special printing ink for each product, and its formula is also the special printing ink specially customized by the ink factory. This kind of ink is difficult to adjust without knowing the detailed formula, so it has a good anti-counterfeiting effect

8. Compliant ink: after mixing two or more anti-counterfeiting inks according to the general proportion, a composite ink with new performance can be developed. If the ink formula is not fully mastered, it will be difficult to copy

9. Other anti-counterfeiting inks: Plastic anti-counterfeiting inks. It is suitable for printing PP, PVC, PE, PS, ABS, PC and other plastic products. 150~200 mesh polyester can be used for printing 20~30 ㎡ per kilogram of ink, which can be naturally dried or at 30? Dry at C for 3min. Metal, glass, ceramics, anti-counterfeiting ink. It is suitable for printing metal temperature signs, color changing glass water utensils, color changing milk cups, ceramic tea sets and other gifts. It can be printed with 70~100 mesh polyester, 10~20 ㎡ per gram of ink, and the drying condition is 25? C、48h、45min. Special ink for anti-counterfeiting of glass and ceramic decal transfer paper. It is suitable for the printing of glass and ceramic decals. 150 ~ 200 mesh polyester is used, and the drying condition is 200 ° after water transfer? C，200min. The displacement of water-based anti-counterfeiting oil is proportional to the output Hall potential ink and printing paste. It is suitable for paper, cotton, woven fabrics, T-Shirts, sportswear, etc. with 80 ~ 150 mesh polyester, it can print about 20 ㎡ without kilogram of ink (cotton weaving will be less than this number), and the drying condition is 130? C，3min。