Magnetic ink application of two

(C) Magnetic ink printing and its characteristics

After understanding the basic principles of magnetics and magnetic recording, we began to enter the topic of this article—magnetic ink.

As described in the previous article, the principle of magnetic recording, the principle of magnetic recording for anti-counterfeiting magnetic inks is basically the same as the magnetic recording principle of audio tapes. The only difference is that the magnetic recording of anti-counterfeiting magnetic inks has a relatively low requirement and a sense of The magnetic quality of magnetic materials after magnetization is also lower.

Magnetic printing is the application of magnetic ink, and the basic technology of magnetic printing is to apply a magnetic layer on a paper or plastic film base, and then to print letters or patterns on other parts so as to be used to display visual information corresponding to the status of use. The layers, after being molded, become generally known as "magnetic prints", which can be said to be a unique recording medium produced by combining the recording and printing techniques.

Generally speaking, in the magnetic printing technology, the band or pattern magnetic layer is mostly obtained by means of screen or lithography, because it can form the characteristics of the magnetic tape only where necessary for the card, thereby reducing the cost of magnetic printing. After printing, the transparent PVC film is covered on both sides, pressed with a hot press, die-cut to the specified size, and finally it becomes a magnetic printed product.

Figure 4, the flow of magnetic printing

In anti-counterfeiting, magnetic ink printing in order to prevent counterfeiting and tampering, security is increasingly high confidentiality, so in magnetic materials, printing, processing methods often use special materials or technologies, such as the use of special plate-making technology and ink printing, Including the use of fluorescent ink, thermochromic ink, absorbing infrared ink printing, shading printing, micro-printing, full portrait of the rainbow, are commonly used in magnetic printing to prevent counterfeiting materials or methods.

For magnetic ink printing, its characteristics can be summarized as:

1. Data files can be written and read on magnetic cards, and text, patterns and photos can be visually seen;

2. The magnetic signal can be detected by a magnetic detector with a pattern or logo printed by a magnetic ink;

3. Printed passwords and other information printed with magnetic ink can be read by the decoder.

Third, with the magnetic ink printing related printability factors

The so-called printability, simply speaking, is the performance of substrates, inks, plates, printing processes and printing room conditions suitable for printing. In the following, magnetic ink, magnetic film, magnetic number, and substrate for printing will affect the factors related to the printing quality of magnetic ink in four aspects.

(a) magnetic ink

Before and after the 1960s, magnetic inks were applied to the automatic processing of stamps, the automatic sorting of letters, and the automatic processing of the classification of books to enable automation of bank transactions. Since magnetic inks were not used for anti-counterfeiting at the time, magnetic inks were mainly used to print letters and digits to facilitate automatic identification and processing of the prints. Since the 1980s, magnetic inks have broken the restrictions that were originally only in the black or limited range of colors, and have expanded it to four-color magnetic inks.

The magnetic ink is mainly made of fine powder magnetic material and synthetic resin valine and dry oil. At present, the annual consumption of magnetic ink in the world has reached several thousand tons, which is mainly used for symbols on cheques. With the letter printing (figure 5), the printing methods are generally plain printing and embossing, and also used for printing tapes on credit cards.

Figure 5, magnetic printing symbols and numbers

The basic composition of the magnetic ink is the same as the general ink, that is, it consists of a pigment, a binder, a filler and an auxiliary material. The difference is that the pigment used in the magnetic ink is not a pigment but a ferromagnetic material. They are described as follows:

Pigment

Magnetic inks use ferromagnetic materials that retain magnetic properties after magnetic treatment. Among them, the best magnetic pigments are iron oxide black (Fe3O4) and iron oxide brown (Fe2O3), because these pigments are mostly needles less than 1 μm. Crystallization, so they are easier to arrange in the magnetic field, and have a high residual magnetism. Among them, the composition of iron oxide black, the general ferrous oxide content of about 18% -26%, iron oxide content of about 74% -82%, synthetic iron oxide black has excellent permeability, chemical resistance, Lightfastness is almost non-toxic, and heat resistance is acceptable, because when heated to about 177°C, iron oxide black will oxidize to red iron oxide. The disadvantage of these pigments is that the oil absorption is relatively large and the transfer performance is not very good. Therefore, some granular or cubic iron oxides are sometimes used in combination to improve the printing performance.

Author: Chen Yali