Overview Of Modern Packaging Anti-counterfeiting Technology (Part 1)

Overview of Modern Packaging Anti-counterfeiting Technology (Part 1)

1. Anti-counterfeiting of printing ink

1. Magnetic anti-counterfeiting ink

Magnetic ink is composed of pigments, binders, fillers and additives. The pigments used are iron oxide black (Fe3O4), iron oxide brown (γ-Fe2O3), cobalt-containing iron oxide brown (γ-Fe2O3) and chromium oxide ( CrO2) and other ferromagnetic materials. Magnetic ink can generate magnetism after magnetic field treatment, which can record and store special coded characters and symbols, so that it has stronger and safer anti-counterfeiting function in packaging and decoration.

2. Reactive color changing anti-counterfeiting ink

(1) Thermochromic ink

It is a special ink that changes the color of the pigment due to the change of temperature and restores the original color after cooling. According to the type of discoloration, it can be divided into irreversible discoloration pigments and reversible discoloration pigments. Different heating time and heating speed affect the discoloration of ink, as shown in the following formula:

Reversible Color Change: T=A BlogV

In the formula, T (°C) is the discoloration temperature; V (°C/min) is the heating speed; A and B are the measured ink constants. It can be seen from the formula that there is a logarithmic relationship between the discoloration temperature and the heating rate. The faster the heating rate, the higher the discoloration temperature.

irreversible color: T=a blogt

In the formula, T (°C) is the discoloration temperature; t is (min) the heating time; a and b are the measured ink constants. It can be seen from the formula that the discoloration temperature is proportional to the logarithm of the heating time. The longer the heating time, the higher the discoloration temperature.

Irreversible color pigments commonly used are: lead, cobalt, nickel, iron, cadmium, strontium, zinc, manganese, molybdenum, barium and magnesium sulfate, nitrate, phosphate, chromate, sulfide, oxide, and even Nitrogen pigments, phthalocyanine pigments, arylmethane dyes, etc., the main discoloration mechanism is caused by thermal decomposition, oxidation, or chemical reaction of the pigment or dye itself. Because it is a chemical reaction, it is irreversible. Reversible color-changing pigments include compounds formed by Ag, Hg, Cu iodide, complex or double salt cobalt salt, nickel salt and hexamethylenetetramine. The main color changing mechanism is that some pigments lose crystal water, and some Some of them undergo crystal transformation, and some are changes in pH value, all of which are physical changes, and their changes are reversible.

(2) Photochromic ink

Photochromic ink is a photochromic organic compound added to the ink, which can be divided into photoredox compounds and photodissimilation compounds. The phenomena that will occur are: cis-transformation anisotropy, tautomerization, or H-movement, heterogeneous cleavage, ion dissociation, homogeneous cleavage, or photodissociation of free radicals, and photoredox. , open-loop and closed-loop phenomena. Common photochromic materials include azo dyes and indigo dyes, spirocyclic benzopyrans, triarylmethane dyes, and 1,4-dihydroxyanthraquinone. The main mechanism is that the chemical structure of the object changes under the irradiation of a certain wavelength, and then the color changes, which can be changed from colorless to colored, or from one color to another color.

3. Fluorescent ink and fluorescent ink

The main component of fluorescent ink is fluorescent pigment, which belongs to functional luminescent pigment. According to the molecular structure, it is divided into organic and inorganic fluorescent pigments. It is mainly a solid solution of synthetic resin dyed with fluorescent dyes. The commonly used synthetic resins are: polymethacrylate, polyvinyl chloride, alkyd resin, uric acid resin, styrene resin and their copolymers, etc. As fluorescent dyes, Thio bright yellow pigment FF, fluoro gold light chlorine, bright yellow 6G, rhodamine B, etc. Its main mechanism is that high-brightness visible light other than ordinary colors is emitted when sunlight is irradiated. The higher the content of ultraviolet light, the stronger the fluorescence it emits. The content is different, showing a spectrum of various colors. Light-storing ink is a kind of fluorescent ink. The phosphorescent pigment contains some sulfide/copper phosphors, calcium sulfide/bismuth phosphors, etc. with phosphorescent effect, and its mechanism is similar to that of fluorescent inks.

4. Other anti-counterfeiting inks

In addition to the above, there are other anti-counterfeiting inks with different functions, such as pressure-sensitive color-changing ink in reactive color-changing ink, adding certain chemical substances to the ink, and the color can be changed when pressed; there are also newly developed and The developed intelligent anti-counterfeiting ink, the anti-counterfeiting material is composed of a variety of variable chemical substances; the resin, pigment and other materials in the nano-ink are all made of nano-materials, the ink does not rely on chemical pigments to develop color, but depends on choosing appropriate The volume of nanoparticles shows different colors; liquid crystal ink is a liquid crystal under the action of weak current and temperature, the crystal lattice changes to display light and dark graphics and colors, and the graphics can show different colors with the change of temperature in the four seasons. , its application in food packaging is immeasurable; biochemical reaction ink is added with substances that can produce biochemical reactions in the ink, and the pictures and texts can be displayed by methods such as micro-heating, wetting, and friction; thin film light Interference color-changing ink is the use of the interference pigment of light in the ink to produce the phenomenon of light interference, so that the printed image and text can be transformed into different colors from different angles. All of the above inks can be used for the anti-counterfeiting printing of food, and play a certain anti-counterfeiting effect.

2. Anti-counterfeiting of printing process

1. Holographic printing technology

Holographic printing is to copy holographic images recorded by laser photography on a specific printing material in large quantities. Due to the high technical content in the production and reproduction of holograms, the grating density of holograms is 10 000 lines/mm, and the height of undulation is a few tenths of a micrometer. Moreover, due to the characteristics of holograms themselves, it is difficult to forge, so it has good anti-counterfeiting. sex. In addition, the anti-counterfeiting property of holographic printing is also strengthened by designing the anti-reveal type and hot stamping type. The process flow of holographic printing is:

Shooting hologram - making hologram master - master surface metal - electroplating metal master - imprinting - vacuum coating

2. Rainbow printing anti-counterfeiting technology

Rainbow printing, also known as multi-color printing or medium-color printing, is generally completed by a set of offset printing units in packaging printing. According to the printing requirements, place a partition plate at a certain distance in the ink fountain of the ink supply device, and then put ink of different hues in different partitions. Under the serial action of the inking roller, the ink in the adjacent parts is mixed and then transferred to the printing plate, so as to obtain a rainbow-like printing effect after rain.

With rainbow printing anti-counterfeiting technology, multiple colors can be printed at one time, and the middle is too soft. The rainbow printing effect is difficult to achieve by the method of multi-color overprinting. Even if the rainbow printing method is used, it is difficult to see the exact position of the ink fountain partition on the packaged product. difficulty. If this process is used on a large area of shading, its anti-counterfeiting effect will be more obvious.