Magnetic printing and magnetic card production
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Magnetic printing is the abbreviation of magnetic ink printing. It uses magnetic substances such as iron oxide as ink pigments, and completes the production of magnetic recording materials by a certain printing method, so that the printed matter has the special functions required. In recent years, with the development of computer technology and network technology, magnetic prints have been applied in many fields, such as bank passbooks, checks, ID cards, credit cards, telephone cards, train tickets and price lists.
1. Basic composition
In magnetic printing, the material constituting the magnetic recording body is a magnetic ink.
Magnetic ink is a special ink. Its basic composition is similar to that of ordinary printing ink, that is, it consists of pigment, binder, filler and auxiliary materials. However, the pigment used in magnetic ink is not a pigment but a ferromagnetic material. The so-called ferromagnetic material refers to a special material that is magnetized when it is inserted into a magnetic field, and retains magnetism even if the magnetic field is removed. The ink itself is non-magnetic before magnetization and is magnetic because the pigment used in the ink formulation has the ability to retain magnetism after being subjected to magnetic field treatment. Of course, there are many factors affecting the characteristics of the magnetic recording layer, such as the magnetic properties of the pigment, the content of the magnetic pigment in the ink, the thickness of the magnetic film, etc. Experiments have shown that the thickness of the dried magnetic film is preferably 10-20 μm. Further, in order to improve the smoothness and abrasion resistance of the surface of the magnetic film, surface glazing may be performed with a synthetic resin after printing.
The ferromagnetic pigment plays a functional role in the magnetic ink, and the printing aid is suitable for the ink binder, which will be described below according to the material characteristics.
2. Magnetic pigment
The ferromagnetic materials mainly include magnetic elements such as iron (Fe), cobalt (Co), and nickel (Ni), ferromagnetic alloys of Fe-Mo and Fe-W, and alloys of NiAs type having Mn-Al and Mn-Bi. Wait. The pigment used as the magnetic ink is mostly ferrite, that is, an inorganic compound generally represented by XO-Fe2O3, wherein X is a divalent metal ion, and depending on the type of X, there are manganese-ferrite and iron-ferric, respectively. Body, copper-ferrite, etc. The above-mentioned ferromagnetic material is placed in a magnetic field, the magnetic field strength is changed, and the corresponding magnetization value is tested, that is, the H-B curve of the ferromagnetic material can be obtained. The H-B curve is an important curve representing the properties 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 by printing density values and hue as evaluation parameters. For magnetic printing, the residual magnetization value and magnetoresistance value of the H-B curve are used as parameters for print quality evaluation. For example, in counting and measuring magnetic recording body printing, the magnetoresistance value of the ferromagnetic material should be 20,000 to 30,000 A/m, and the residual magnetization value should be 0.08 to 0.11 T. Therefore, magnetic printing must understand the basic characteristics of ferromagnetic materials, rational selection of ferromagnetic materials, and determination of magnetic ink formulations, which is the key to obtaining excellent magnetic prints.
Common magnetic pigments are iron oxide black (Fe3O4), iron oxide brown (γ-Fe2O3), cobalt-containing γ-Fe2O3 and chromium oxide (CrO2).
3. Link material
The binder is an important component constituting the ink fluid. Its main function is to impart a fluidity to the solid powder such as a pigment, so that it forms a slurry fluid after grinding and dispersion, and is dried and fixed on the surface of the substrate after printing.
The rheology, viscosity, dryness, and printing properties of the ink depend mainly on the binder. Therefore, high-quality magnetic inks not only have good magnetic materials as pigments, but also excellent binders.
Common binders for magnetic inks are vegetable oil (linseed oil) and synthetic resin (alkyd resin).
1. Printing method
Magnetic printing used to be lithographic, letterpress, and developed magnetic latent images.
With the popularity of various magnetic cards, magnetic printing has begun to adopt a variety of printing methods such as gravure and screen printing. In addition, there are special printing, such as forming magnetic images by spraying; high-speed printing by non-impacting devices; magnetic capsule printing and magnetic layer transfer.
2. Performance requirements
Most printing inks function to obtain a plan view, while magnetic printing uses special graphics obtained by printing for inspection and recording. In addition to the magnetic parameters of the ink as a key indicator, the evaluation of the performance of the magnetic ink should also pay attention to printability and ink adhesion. For example, the magnetic ink used for lithography must solve the problem of ink emulsification caused by the hydrophilicity of the magnetic material, because the emulsification phenomenon causes the ink to adhere to the blank portion, and the magnetic properties of the image portion are weakened, and the magnetic detection and discrimination zone for the next step is given. Bad influence. In general, magnetic pigments have a high density and a high content relative to other ink pigments, and 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 magnet materials and resins such as polyamide resin, thermoplastic epoxy resin, asphalt fiber, polystyrene, oxygen (hetero), ruthenium, and the like 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 in the magnetic card has stable physical and chemical properties and good reliability; it is easy to store for a long time, has good probabilistic performance, and can be used repeatedly; it can be recorded again after magnetic elimination, and the economy is good; the reading and writing device is simple and can be realized. Small, lightweight, easy to carry and use; its types and applications are gradually expanding.
1. Classification of magnetic cards
(1) Classification by purpose: generally divided into magnetic card, password card, prepaid cash card.
(2) Classification according to production and information reading: generally divided into magnetic cards and special magnetic cards.
2. Magnetic card base materials and specifications
The base material used for the magnetic card needs to meet some basic requirements. From the use conditions, it should have corresponding physical and chemical properties, and require good durability. During use and long-term storage, the performance does not change greatly.
(1) Material type: Common magnetic card base materials can be divided into plastic base and composite paper base. The plastic sheet-based material requires good mechanical properties, dimensional stability, and smooth surface, but requires pre-press treatment; the composite paper-based material has good printability and does not require pre-press processing, but its comprehensive index is far less than that of plastic-based materials.
(2) Performance characteristics of plastic sheet base material: The plastic sheet base can be divided into polyester (polyester) sheet base, cellulose acetate and polyvinyl chloride base according to material composition. Performance comparison of several commonly used base materials.
(3) Dimensions of plastic magnetic card: The international standardization body has established the size specification of the plastic magnetic card, that is, the ISO standard, which stipulates that the standard magnetic card size is:
Length: 85.47 ~ 85.72mm;
Width: 53.92 ~ 54.03mm;
Thickness: 0.68 to 0.84 mm.
Plastic magnetic card ISO standard size.
In addition, under the premise of meeting the ISO standards, countries have formulated corresponding national standards according to their actual conditions. For example, Japan has developed the JIS-X6301 standard, which is divided into I type and II type. The magnetic strip of the I type card is located on the back of the plastic magnetic card; the magnetic strip of the type II card is located on the front side of the plastic magnetic card.
3. Magnetic card processing technology
(1) Production process
Design → Group Edition, Calibration → Plate Making → Printing → Film Lamination → Magnetic Striping → Leveling → Broken, Forming → Expansion Processing → Magnetic Inspection, Degaussing → Data Writing → Final Inspection → Finished Product
(2) Main production process
Magnetic processing and expansion processing are important processes in magnetic card printing, including magnetic processing, hot stamping and coloring, and signature label processing.
2.1 Magnetic processing, a magnetic strip of about 6mm width is attached to a specified area of the magnetic card, and the necessary magnetic information is finally written by processes such as leveling, magnetic inspection and degaussing.
2.2 Hot-pressing plastic characters and coloring, the surface of the magnetic card is subjected to text convex processing by a hot pressing device to form characters such as a number, an expiration date, and the coloring foil can also be used for coloring processing.
2.3 Signature label processing, made by screen printing or pasting, hot pressing.