Ink anti-counterfeiting technology in ticket printing (I)

Tickets cover a wide range of areas and, to a certain extent, have the nature and functions of money. In order to keep the order of economic activity from being destroyed, when these securities are printed, there must be anti-counterfeiting measures, so that people can easily distinguish between their authenticity and use, and they can not be forged by criminals.
Ticket printing is a special industrial sector in the printing industry. The products produced are mainly special goods that are circulated by society – banknotes, stamps, various bonds, promissory notes, cheques and various commercial papers.
Under market economy conditions, the quality of ticket printing and the prevalence of ticket use represent the level of market economy development. In general, all types of ticket printing are classified into valuable tickets and general tickets according to different purposes. According to the different fields of application and forms of use, they are divided into bank tickets, postal tickets, business forms, and electromagnetic tickets.
The development of economy and technology puts high demands on the security of the ticket, and the anti-counterfeiting technology is also more complicated: there are design aspects, as well as paper, ink and printing technology. In the anti-counterfeiting technology of ticket printing, in order to reduce the cost of anti-counterfeiting technology, it is also necessary to make full use of the current printing process, generally considering starting with ink anti-counterfeiting. In addition to normal expression of the corresponding hue, various anti-counterfeiting inks also undergo special changes under the influence of external light, heat, reagents or magnetic fields, and the public uses this as a means of identification.
The application of ink technology to anti-counterfeiting is achieved by changing the ink formulation or adding some special sensitive materials such as photosensitive materials, heat-sensitive materials, magnetic materials, etc. to the ink. Ink anti-counterfeiting technology is currently the most rapidly developing high-tech. Since it is difficult to develop such an ink and the import price is high, it is difficult to buy on the market, which enhances the objective safety of using this ink. 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 the main application of several security inks.
First, magnetic ink Magnetic ink printing belongs to the field of magnetic recording technology. The magnetic recording body is completed by printing so that it has the desired special properties. Magnetic inks are currently used in many fields, such as banknotes, invoices, cheques, etc. This type of ink has been used on the 1990 version of China's 100-yuan banknotes. This ink can show information contained in or sent out by a special tool to show its authenticity.
1. Basic composition of magnetic ink The basic composition of magnetic ink is the same as general ink, which consists of paint, binder, filler and additive. However, the pigment used in the magnetic ink is not a pigment but a ferromagnetic material. Magnetic materials have the ability to retain magnetic properties after magnetic treatment. Of course, there are many factors that affect magnetism, such as the magnetic properties of pigments, the content of magnetic pigments in inks, and the thickness of the ink film after printing.
The main component in the magnetic ink is a magnetic pigment, and the best magnetic pigments are iron oxide black (Fe3O4) and iron oxide brown (Fe2O3). Most of these pigments are needle-shaped crystals less than 1 μm, and they are easily aligned in a magnetic field, resulting in relatively high residual magnetism. The disadvantage is that the oil absorption is relatively large and the transfer performance is not very satisfactory. Therefore, some granular or cubic iron oxides are sometimes used to improve the printing performance, but the amount should not be too much.
The key to obtaining excellent magnetic prints is to understand the basic characteristics of ferromagnetic materials, reasonably select ferromagnetic materials, and correctly determine the formula for magnetic inks. The iron oxide black pigment has a relatively high oil absorption and a poor stability. In particular, the dry pigment powder has a poorer stability and therefore has a higher magnetic property. CrO2 is a black ferromagnetic oxide and its conductivity is very good. It is a promising magnetic material. (To be continued)