Magnetic printing and magnetic card production

Magnetic printing is an abbreviation for magnetic ink printing. It incorporates a magnetic substance such as iron oxide as an ink pigment, and completes the production of a magnetic recording body by a certain printing method, so that the printed matter has the required special functions. In recent years, with the development of computer technology and network technology, magnetic prints have been used in many fields, such as bankbooks, cheques, ID cards, credit cards, telephone cards, car tickets, and price lists.

Basic composition

In magnetic printing, the material constituting the magnetic recording body is a magnetic ink.

Magnetic ink is a special type of ink, and its basic composition is similar to that of ordinary printing inks. It consists of pigments, binders, fillers and auxiliary materials. However, the pigments used in magnetic inks are not pigments but are strongly magnetic materials. The so-called ferromagnetic material is a special material that is magnetized by inserting it into a magnetic field, and retains magnetism even when the magnetic field is removed. The ink itself is not magnetic before magnetization, and it is magnetic because the pigment used in the ink formulation has the ability to retain magnetic properties after magnetic treatment. Of course, there are many factors that affect the characteristics of the magnetic recording layer, such as the magnetic properties of the pigment, the content of the magnetic pigment in the ink, and the thickness of the magnetic film. Experiments have shown that the thickness of the magnetic film after drying is preferably 10-20 μm. In addition, in order to improve the smoothness and wear resistance of the surface of the magnetic film, the surface can be surface-treated with a synthetic resin after printing.

It is the strong magnetic pigment that plays a functional role in the magnetic ink, and the printing auxiliary function is the ink connecting material that is suitable for it. The following will introduce the material characteristics.

2. Magnetic pigments

The ferromagnetic material mainly includes magnetic elements such as iron (Fe), cobalt (Co), and nickel (Ni), a ferromagnetic alloy of Fe-Mo and Fe-W, and an alloy having a NiAs structure such as Mn-Al and Mn-Bi. Wait. The pigment used as a magnetic ink is mostly ferrite, which is generally an inorganic compound represented by XO-Fe2O3, in which X is a divalent metal ion, depending on the type of X, there are manganese-ferrite, iron-ferritin, respectively. Body, copper-ferrite and so on. The above-mentioned ferromagnetic material is placed in a magnetic field, the strength of the magnetic field is changed, and the corresponding magnetization value is tested, and the HB curve of the ferromagnetic material can be obtained. The HB curve is an important curve representing the characteristics of the magnetic material, where oa represents the saturation magnetization value, ob represents the residual magnetization value, and oc represents the magnetoresistance value.

The quality of conventional prints is often measured using print density values ​​and hue; however, for magnetic prints, the residual magnetization and magnetoresistance values ​​of the HB curve are used as print quality evaluation parameters. For example, in counting and metering magnetic recording media, the ferromagnetic material should have a magnetic resistance of 20,000 to 30000 A/m and a residual magnetization of 0.08 to 0.11T. Therefore, magnetic printing must understand the basic characteristics of ferromagnetic materials, a reasonable choice of ferromagnetic materials, to determine the magnetic ink formulations, which is the key to obtain excellent magnetic prints.

Common magnetic pigments include iron oxide black (Fe3O4), iron oxide brown (γ-Fe2O3), cobalt-containing γ-Fe2O3 and chromium oxide (CrO2).

3. Binder

The binder is an important component of the ink fluid. Its main function is to impart fluidity to solid powders such as pigments, to form a slurry fluid after grinding and dispersing, and to dry and fix on the substrate surface after printing.

The rheology, viscosity, dryness, and printing properties of inks are mainly dependent on the binder. Therefore, high-quality magnetic inks need not only good magnetic materials as pigments, but also linking materials with excellent properties.

Magnetic ink commonly used linking materials are vegetable oil (linseed oil) and synthetic resin (alkyd).

1. Printing method

In the past, magnetic printing used lithography, letterpress printing, and magnetic latent image development in three ways.

With the popularization of various magnetic cards, magnetic printing has begun to adopt various printing methods such as gravure printing and screen printing. In addition, there are special types of printing, such as the formation of magnetic images by jetting; high-speed printing of non-impact devices; magnetic capsule printing and magnetic layer transfer.
2. Performance requirements

The function of most printing inks is to obtain the text of the floor plan, while the magnetic printing is to use the special graphics printed to use as detection and recording. In addition to evaluating the magnetic ink's performance as a key indicator of the ink's magnetic parameters, printability and ink adhesion should also be considered. For example, the magnetic ink used for lithographic printing must solve the problem of ink emulsification due to the hydrophilicity of the magnetic material, because the emulsification phenomenon causes the ink to adhere to a blank part, weakening the magnetic part of the graphic part, and giving the magnetic detection and discrimination band for the next step. Bad influence. In general, magnetic pigments have the characteristics of high density and high content relative to other ink pigments. Therefore, it is necessary to ensure good affinity between the binder and the pigment.

In order to improve the printability and ink adhesion of magnetic inks, iron powder and other permanent magnetic materials and polyamide resins, thermoplastic epoxy resins, pitch fibers, polystyrene, and oxygen-neutral resins are currently used. After mixing, it is suspended in an aqueous medium in a molten or liquid state to obtain a developed magnetic latent image ink suitable for high-speed printing.

The magnetic recording material used by the magnetic card has relatively stable physical and chemical properties and good reliability; it is convenient for long-term preservation, has good inducing performance, and can be used repeatedly; after magnetic elimination, it can be recorded again with good economical efficiency; and the read-write device is simple and can be realized. It is small and lightweight, easy to carry and use; its types and application areas are gradually expanding.

1. Classification of magnetic cards

(1) Classified by purpose: Generally divided into magnetic cards, password cards, and prepaid cash cards.

(2) Classification according to production and information reading methods: generally divided into magnetic cards and special magnetic cards.

2. Magnetic card base materials and specifications

The base material used for magnetic card needs to meet some basic requirements. From the use conditions, it should have corresponding physical and chemical properties, and requires good durability. During use and long-term preservation, the performance does not change greatly.

(1) Material type: The commonly used magnetic card base materials can be divided into plastic bases and composite paper bases. Plastic sheet-based materials require good mechanical properties, dimensional stability, smooth surface, but the need for prepress treatment; composite paper-based materials, printability is good, does not require prepress processing, but its comprehensive indicators far better than plastic film-based materials.

(2) Performance characteristics of plastic base materials: Plastic base materials can be divided into polyester (polyester) base, cellulose acetate, and polyvinyl chloride base. Performance comparison of several commonly used film-based materials.

(3) Size specification of plastic magnetic card: The international standardization organization has developed the size specification of plastic magnetic card, ie ISO specification, and stipulated the standard magnetic card size as:

Length: 85.47~85.72mm;

Width: 53.92~54.03mm;

Thickness: 0.68 to 0.84mm.

Plastic magnetic card ISO standard size.

In addition, under the premise of meeting the ISO standards, various countries have formulated corresponding national standards according to their actual conditions. For example, Japan has developed the JIS-X6301 standard, which is divided into type I and type II. The magnetic strip of the type I card is located on the back of the plastic magnetic card; the magnetic strip of the type II card is located on the front of the plastic magnetic card.

3. Magnetic card processing technology

(1) Production process

Design → Group Edition, Calibration → Plate Making → Printing → Coating → Magnetic Stripe → Leveling → Breaking, Molding → Expansion Processing → Magnetic Inspection, Demagnetization → Data Writing → Final Inspection → Finished Product

(2) Main production process

Magnetic processing and expansion processing are important processes in magnetic card printing and processing, including magnetic processing, hot stamping and coloring, and signature marking.
1 magnetic processing, the width of about 6mm magnetic strip attached to the designated area of ​​the magnetic card, the leveling, magnetic inspection and degaussing processes, and finally write the necessary magnetic information.

2 Pressing and coloring by hot pressing, text-embossing of the surface of the magnetic card by means of a hot pressing device, forming characters such as numbers, expiration dates, etc., and coloring may also be performed using colored foils.

3 Signature label processing, using screen printing or paste, hot press method.

Reprinted from: Ke Yin Network

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