Anti-counterfeiting inks for anti-counterfeit packaging printing (2)

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. The reversible type means that when the thermochromic discoloration occurs, the heat source can be restored to its original shape once the ink color is removed. The type of discoloration can be divided into sublimation, melting, thermal decomposition, oxidation and curing reactions, mainly due to the loss of crystal water after the conversion of crystal form or due to PH. 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 Therefore, the color of the ink cannot be restored to the original color when the heat source is withdrawn.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 radiation. The color changing wavelength is 400~800nm. 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 ~ 200 mesh polyester net, each kilogram of ink can be printed 20 ~ 30m. , Dry naturally or at 130 °C for 3 minutes.

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 to 20 square meters per kilogram of ink, and drying conditions of 25, 48, or 120 degrees Celsius. 45min.

Glass, ceramic decal transfer paper security special ink. Applicable to the printing of glass and ceramic decals, with a 150 to 200 mesh polyester web, 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 ~ 150 mesh polyester net, each kilogram of ink can be printed about 20m2 (cotton fabric will be less than this number), drying conditions for 130 °C, 3min.

Source: Screen Printing Industry