Screen Printing Design in Anti-counterfeit Packaging Printing (II)

Second, security printing anti-counterfeiting printing screen printing ink

At present, there are many kinds of anti-counterfeiting inks developed, but according to the characteristics of screen printing, the most suitable inks for screen printing are the following:

1. Liquid Crystal Ink: Liquid crystal ink is a new type of special ink that originated in the United States in the 1970s. It refers to the addition of a compound with crystalline properties to the ink. From the production method, it also belongs to the type of microcapsule structure ink, from the application point of view, is a thermochromic temperature-induced color ink, but from the perspective of the characteristics of liquid crystal ink, mainly the use of liquid crystal thermochromic characteristics. The liquid crystal ink is mainly composed of a water-soluble resin, a liquid crystal capsule, an auxiliary agent, a binder, and a defoamer. The liquid crystal ink is prepared by dispersing the liquid crystals, additives and the like enclosed in the microcapsules in a binder. The liquid crystal ink does not lose the color ink of the ink layer pigment, but uses the liquid crystal temperature in the ink layer to change the molecular direction, thereby selectively reflecting the visible light of a specific wavelength and absorbing the optical characteristics of other wavelength light, thereby rendering the color. Variety. The color forming mechanism of the liquid crystal is formed by selectively reflecting light at a specific wavelength. The molecular arrangement of the liquid crystal is not as strong as the crystal structure, and therefore it is easily influenced by the external environment and changes its optical properties. The liquid crystal ink utilizes this characteristic of the liquid crystal, so that the liquid crystal changes in the crystal lattice under the influence of weak current and temperature to show bright and dark patterns and colors.

The liquid crystal ink printing method is preferably screen printing, so that the printed product has a reversible reaction or an irreversible reaction printing method. The key to liquid crystal printing technology is the ability to display brightly colored liquid crystals at different temperatures, and to make a series of color temperature stability values. The production technology of the liquid crystal microcapsules is also key. The microcapsules must be small and uniform, the capsule wall is transparent and thin, and the ink is incorporated. It requires solvent resistance, stability, reliability, and long life; the liquid crystal microcapsules must also be guaranteed during the printing process. Not broken; surface covered with protective film. The amount of liquid crystal added to the ink is 40% of the total amount of ink. The diameter of the capsule is preferably 10~3um. The screen used for the printing of liquid crystal ink is generally a nylon screen or a polyester screen. If a large amount of ink is required for the printing plate, a stainless steel screen plate may be used. According to the requirements of ink microcapsule diameter and ink layer thickness, generally choose 100 ~ 175 days. Since the humor of the screen liquid crystal microcapsules is water-soluble, the water-resisting photosensitive adhesive should be used when making the plate.

The following problems should be paid attention to when screen printing liquid crystal ink: A. In each printing, the printing plate should have sufficient ink volume, and the ink should be even, and it is best to fill the ink halfway to prevent foaming. B, micro-capsule ink is easy to plug the screen, if found blocking the network, blistering, to stop immediately, thoroughly clean with alcohol water. C, printing pressure should be moderate in size. The pressure is low and the amount of ink on the substrate is insufficient, which affects the color effect. When the pressure is too high, the liquid crystal capsules are broken, thereby reducing the color effect. D. The color of the printed part of the division is obvious. The black color or dark tone should be used for the printing background. Low-color water-soluble solvent ink or organic solvent ink, printing methods available screen printing, offset printing, gravure. When organic solvent inks are used, they must be fully dried after printing to avoid solvent residues in the oil film and react with the liquid crystal and affect the color effect. E. The printing process should pay attention to the smoothness and smoothness of the ink layer, and the thickness should be controlled within 15~35um. F. Arrange the printing color reasonably. Can use black (or dark) ink to print low color, and then use liquid crystal ink to print the desired pattern; you can also use liquid crystal ink to print the desired negative pattern to cover. G. When the printed matter is best to be stacked, do not dry it with hot air of about 40°C. Avoid rapid heating and high temperature drying.

In addition, when the printed matter is not stacked, it should not be heavily pressed. After drying, it should not be piled up as much as possible. When cutting, excessive partial pressure should not be added to prevent the liquid crystal microcapsules from being crushed. When using liquid crystal inks, the color temperature range should also be determined according to the purpose of use, and the durability of the liquid crystals should be taken into consideration according to the use. In order to improve the surface wear resistance, temperature resistance, gas barrier and maintain its gloss, the surface can be coated with varnish or protective film.

2. Magnetic ink: The anti-counterfeiting principle of magnetic ink is to use magnetic color materials, such as iron oxide or iron oxide to add cobalt and other chemical substances, and apply magnetic detection pigments such as Fe3O4 (black) and Fe2O3 (brown). Most of these pigments are needle-shaped crystals smaller than micrometers. Such particle size and shape make them very easy to arrange evenly in the magnetic field and obtain relatively high residual magnetism. Symbols and numbers with such residual magnetism pass through the automatic processing device. The friction function within the recognition 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 known as temperature-sensitive ink, is a special ink that can change color with temperature. The principle of anti-counterfeiting of thermal ink is the substance whose color changes with temperature. In recent years, some research sites and manufacturers at home and abroad have successively developed thermochromic inks with different characteristics. Nowadays, there are three types of thermochromic inks: color reversible, 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. The main loss of crystallinity after losing crystal water is due to the change of crystal form or pH value. Change and change color, so when the heat source is eliminated, it can be restored to its original state. The irreversible type is when the discoloration color changes in the printing ink so that the ink color cannot be restored to the original color when the heat source is withdrawn. Memory type has memory function.

Thermochromic ink can be used for screen printing, concave drawing 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 Inks: Photochromic inks, also known as photochromic inks, incorporate photochromic or light-level activating compounds in the ink. In the sun, the ink can change from colorless to colored, or from orange to black, etc. Divided into common type UV type. Ordinary type means that under the effect of ordinary daylight and intense light, the color of 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. Under UV light (ultraviolet light), bright red, orange, yellow-green, and green fluorescence appear. 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. He has the characteristics of sensitivity to external suites, obvious changes, and quick response. It is an ideal material for woodware that is used in anti-counterfeiting technology and fun gifts. It has broad development and application value.

5. Fluorescent ink: Fluorescent Humor is made of fluorescent material dissolved in a reactive resin. Fluorescent pigments are generally coarser particles, and the types of binders are also more. Different linkages will produce different fluorescence. When using fluorescent inks to ensure that it has a sufficient concentration, the ink layer on the prints is a bit later, so as to ensure satisfactory Fluorescent effect. 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. Luminescent and phosphorescent inks: Luminescent pigments are prepared using certain zinc sulfide/copper phosphors and calcium sulfide/cerium phosphors that have 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 at a certain 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 the use of neutral resins such as cyclohexanone resin, fiber 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 binder used requires transparency and ultraviolet light. This kind of ink is mainly used for printing advertisements and signage. 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 inks: Printing inks are mainly composed of pigments, fillers, and binders. The choice of pigments is an important step in determining the hue and vividness of printed products. Many manufacturers and ink manufacturers have customized each of them. The special ink for product printing, and the special ink specially formulated for the 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, in line with the ink: the two or more security ink mixed in accordance with the general ratio, you can develop a composite ink with new properties, if you do not fully grasp the ink formula will be difficult to copy.

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, 20 ~ 30m2 per kilogram of ink, natural drying or drying at 30? C 3min. Metal, glass, ceramics, security ink. Applicable to metal temperature signs, color changing glass ware, color changing milk cups and ceramic tea sets, etc., with 70 to 100 mesh polyester mesh, each ink can be printed 10~20m2, drying conditions are 25?, 48h, 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 200min after water transfer. The water-based security printing ink and printing paste. Applicable to paper, cotton, knitwear, T-shirts, sportswear, etc., with 80 ~ 150 mesh polyester net, no kilograms of ink can be printed about 20m2 (weaving will be less than this number), drying conditions for 130? C, 3min .