Several new security ink introduction

There are many kinds of inks, such as oily, waterborne, synthetic resin, and powders. With the development of printing technology, materials science, computer science, and various cross disciplines, new high-tech inks are also being used more and more. Most are special products such as banknotes, stamps, various bonds, invoices, and promissory notes. The new type of ink used for ticket printing is mainly to improve its anti-counterfeiting performance. In addition to normally expressing the corresponding hue, various new inks can also undergo special changes under the influence of external light, heat, reagents or magnetic fields. This comes as a means of identification. This type of ink realizes its anti-counterfeiting performance by changing the ink formulation or adding some special sensitive materials such as photosensitive materials, heat-sensitive materials, magnetic materials, etc. to the ink. Since it is difficult to develop such an ink, the price of imported products is high and it is difficult to buy on the market, which increases the security of printing. Anti-counterfeiting inks are used in the same way as ordinary inks and are suitable for various printing machines, so they are versatile. The following describes these inks.

Light change ink

Optically variable materials are widely used in the field of printing inks. There are sleeping-based inks, ink-based inks, plastic inks, and interference inks according to their different uses. The ink is generally produced by dissolving a photochromic dye in a solvent to produce a microfine pigment capsule, and a binder is added to the dissolved pigment depending on the application. The preferred method of manufacture is to dissolve the photochromic dyestuff into a superposed monomer, and to pulverize the superfine polymer particles to make a powder as a pigment. The ink produced by this method is light-resistant compared to the microcapsule capsule ink. Increased sex by 10 times. These powders can be used as pigments in water-based inks, oil-based inks, and plastic inks, as well as all adhesives.

(1) Photochromic water-based screen printing ink

Water-based inks stand out in the textile industry for their safe use and easy operation. This type of water-based ink is screen printed with 80 to 120 mesh, dried at 100° C. for 1 minute (preferably dried overnight), and then heated and bridged at 130° C. for 3 minutes to obtain excellent fiber adhesion. Products. The characteristics of this water-based ink are as follows:

● It can quickly develop color in the sun, and recover the colorless state in a short time after shading (different colors have different colors, yellow through 2 ~ 3min, cyan can be completed in an instant);

● Dispersion performance, can get uniform color printing products;

● Good color rendering and fastness to friction;

● This water-based ink is a liquid ink;

● Good storage stability and easy operation.

(2) Photochromic oil-based ink

Oil-based inks are mainly used for surface printing on plastic films and metal plates. This ink is printed with a screen printing of 100 to 200 mesh. There are many resins used for adhesives: propylene, epoxy, urethane, silicone denatured resins, etc. As solvents, there are esters, ketones, etc. Others include mineral turpentine, petroleum, and the like. Adding photochromic materials to these binders made of resin and solvent can properly adjust the viscosity of screen printing inks to make oil-based screen printing inks.

(3) Photochromic plastic ink

According to investigations, there are few printing manufacturers of plastisol screen printing inks used in Japan. However, in the United States and some other countries, especially in the T-shirt production industry, such printing inks are used more often.

As a kind of difficult-to-dry ink, plastic ink often does not need to clean the screen printing plate. The ink remaining on the plate can also be used in the next day. This plastic ink is made by dilating particles of ultrafine powder of vinyl acetate copolymer with DOP plasticizer to make screen printing ink. Photochromism can also be added to this plastic polymerizer to make screen printing inks. However, when the characteristics of the photochromic material itself are suppressed, the photochromic dye itself is completely decomposed, and this phenomenon can be expressed only after a few days. Therefore, it is difficult to use it as a commodity. However, if the plastic resin does not use vinyl acetate copolymer but uses an ultrafine powder material with the same properties and can control the decolorization of the photochromic, it will be an ideal powder-like photochromic plastic ink.

(4) Interference type ink

This type of ink is the most sophisticated type of modern security ink and is currently a popular high-tech product. Optically variable inks are reflective inks with pearlescent and metallic effects, and color copiers and electronic copiers cannot be copied. In products printed with light-variable inks, the ink patches appear as a pair of colors. Such as magenta - blue, green - blue, blue - green and so on. If the pattern is tilted to 60°, the pattern can be shifted from one color to another. Since only the ink film on the print product is thick, a significant color drift phenomenon can occur, so the printing feature is that any other ink and printing method cannot be imitated.

Fluorescent ink

Fluorescent ink is one of the more widely used inks for ticket printing. Its main component is fluorescent pigments. Fluorescent pigments are functional light-emitting pigments. The difference from ordinary pigments is that they can absorb certain forms of energy when exposed to external light (including ultraviolet light), excite photons, and release absorbed energy in low visible light, resulting in different Hue fluorescence. Different shades of light combine to form an unusually bright color, and when the light stops irradiating, the luminescence phenomenon disappears, so it is called a fluorescent pigment. The ratio of fluorescent pigments to macromolecular resin binders, solvents and auxiliaries can be obtained by grinding the fluorescent ink. This type of ink, which is invisible to the naked eye, only emits light under ultraviolet or infrared light. Due to its switchable and hidden characteristics and its inability to be accurately reproduced on a color copying machine, the ink is used in the special printing industry. The application is more popular.

Fluorescent inks are suitable for printing on paper and vinyl films. Since the inorganic fluorescent substance emits light from the crystal, if the pressure is too high, the crystal may be broken, thereby reducing the brightness of light emission. Therefore, relief printing is generally not used, and it is suitable for screen printing and gravure printing. The rheological properties of most fluorescent inks are pseudoplastic flow, and the viscosity is small. This characteristic determines the printing process is very different from the printing process of common inks. When performing gravure printing and screen printing, besides paying attention to the characteristics of stickiness, connection materials, and drying properties, it is also necessary to pay attention to the adjustment of the printing pressure, and it is not possible to make the printing pressure too large to affect the printing effect. When screen printing, pay attention to the following points:

(1) Fluorescent inks are suitable for screens up to 200 mesh;

(2) When the amount of ink on the printed matter is 50 to 60 g/m2, the hair color and light resistance are ideal.

(3) When the substrate is a transparent object, white ink should be printed first, which can improve the fluorescence effect.

Thermal ink

Thermal ink is a kind of special ink that can change the color of the pigment with the change of temperature. The thermal sensitive material can be classified into inorganic, organic, liquid crystal, etc., and the liquid crystal ink is used for screen printing. , LCD thermal ink printing is a technology that people are more interested in and difficult to grasp. From the production method, it also belongs to the type of microcapsule structure ink, but from the perspective of the characteristics of liquid crystal ink, the main use of the characteristics of liquid crystal thermochromic. The liquid crystals and auxiliary agents enclosed in the microcapsules are prepared by dispersing them in the binder during production, and the main components are as follows:

● Water-soluble resin, acrylic copolymer emulsion, etc.;

● Microcapsule liquid crystal, cholesteryl benzoate, etc.;

● Defoamers, glycerol, etc.

This ink does not use pigment, good thixotropy, good leveling, viscosity of 4 ~ 6Pa · s. It is more suitable to adopt the screen printing process, and the following matters need to be taken care of in the process.

(1) Plate Making

General screen version available nylon or polyester mesh. If the plate needs to carry a large amount of ink, stainless steel mesh plate can be used. The number of meshes is generally 100-175 mesh, and is selected according to the requirements of the ink microcapsule diameter and ink layer thickness. The diameter of the microcapsules is generally between 10 and 30 μm. Use water-resistant emulsions when making plates.

(2) Printing

● The plate should be filled with enough ink at one time, and it is best not to fill the ink in the middle to prevent foaming.

● Because the microcapsule ink is easy to clog the plate, when the network is blocked or foamed during printing, it is necessary to stop the machine immediately and thoroughly wash with alcohol water.

● The printing pressure should not be too large to prevent the liquid crystal capsule from being crushed.

● In order to make the color of the printing part obvious, the black color or dark tone should be used for the printing background. The background color can be water-soluble ink, organic solvent ink can also be used. Printing methods available screen printing, offset printing, gravure. When using an organic solvent ink, it must be fully dried after printing. The organic solvent should not remain in the ink film, otherwise it will react with the liquid crystal and affect the color effect.

● The printing ink layer should be smooth and smooth. The thickness of the ink layer should be controlled to 20-30 μm. The uneven or too thin ink layer will reduce the color effect.

● The printing sequence can be printed with black (or dark color) ink first, then the desired pattern can be printed with liquid crystal ink; it can also be printed with liquid crystal ink first, and then printed with water-soluble black (or dark color) ink. The pattern is covered.

(3) Drying

● The drying method is preferably natural drying. It can also be dried with warm air at about 40°C. Do not heat rapidly at high temperatures.

● Do not overlap stacking after drying. Do not apply pressure when breaking.

Source: China Ink Web