JPS61276101A - Magnetic recording method - Google Patents

Abstract

PURPOSE:To prevent the forgery using the heat or contact copy method by laminating a magnetic layer of high coercive force and a magnetic layer of low coercive force on a substrate together with a protecting layer formed on the magnetic layer to obtain a magnetic recording medium and recording the normal signal to the magnetic layer of high coercive force and the dummy signal to the magnetic layer of low coercive force respectively. CONSTITUTION:With use of this magnetic recording medium, the current of a sufficiently high level is made to flow to a magnetic head to magnetize a magnetic layer 12 of high coercive force. Then the dummy signal is recorded to a magnetic layer 13 of low coercive force. In this case, the recording current is sufficient to magnetize the upper layer 13 but not sufficient to magnetize the lower layer 12. Thus the normal recording signal and the dummy signal are superposed on each other. This makes it difficult to copy the normal record by means of the heat or contact copy method. A reading device having three magnetic heads is used to read both normal and dummy signals. That is, the 1st magnetic head 21 reads both normal and dummy signals at a time, the 2nd magnetic head 22 demagnetizes the dummy signal and the 3rd magnetic head 23 reads the normal signal respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to magnetic recording media and, in particular, to magnetic recording and a recording reading method effective for preventing counterfeiting of magnetic cards.

<Conventional technology> Recently, magnetic recording media have become widespread in various fields.

For example, there are cashless cards used in banks, telephones, etc., magnetic tickets used in transportation facilities, magnetic coupon tickets, magnetic commuter passes, expressway passes, bus coupons, etc.

As the use of magnetic cards expands, there are concerns that they will be counterfeited. Generally, a magnetic transfer method is considered as a method of duplicating magnetically recorded data in order to forge a magnetic card. They are thermal transfer method and contact transfer method.

The thermal transfer method is a method in which a regular magnetic card and a copying card are brought into close contact with each other with their magnetic surfaces, and a temperature slightly higher than the Curie temperature of the magnetic material used for copying is applied to the card, followed by cooling and magnetization.

In the contact transfer method, the above two cards are brought into close contact with each other,
This is a method of transferring by applying a magnetic field higher than the coercive force of the copying card. When using this method, the condition is that the regular magnetic card has a high coercive force. Generally, the magnetic coercive force is required to be 2.5 to 3 times the magnetic coercive force of the reproduction card.

In addition, recently, expressway passes and common bus passes with a coercive force of 27,500e have appeared. This prevents data from being demagnetized by magnetic products that are used daily, such as magnetic necklaces, magnetic health devices, or games that use magnetism.

Furthermore, products with high coercive force of 40,000e and 150,000e are being considered, and it is thought that magnetic cards will continue to move toward higher coercive force. Therefore, the method of copying and counterfeiting magnetic cards by contact transfer is becoming easier.

<Problems to be Solved by the Invention> In view of these problems, the purpose of the present invention is to prevent the normal signal from being easily reproduced by thermal transfer method and contact transfer method, and further to prevent the normal signal from being easily detected. An object of the present invention is to provide a magnetic recording and reading method that is effective in preventing counterfeiting.

<Means for Solving the Problems> The present invention provides a high coercivity magnetic recording medium in which a high coercive force magnetic layer is provided on a substrate made of a nonmagnetic sheet such as a polyester film, and a low coercive force magnetic layer is laminated thereon. The above object is achieved by recording a regular signal in the magnetic layer and a dummy signal in the low coercive force layer.

Next, the present invention will be explained in detail based on the accompanying drawings. 1st
The figure is a cross-sectional view of the magnetic recording medium according to the present invention, and the base 1
1. Consists of a high coercive force layer 12, a low coercive force layer 13, and a protection [14].

To carry out the present invention using the magnetic recording medium, first, a recording current sufficient to magnetize the high coercive force layer is passed through the magnetic head to magnetize the high coercive force layer. Next, a dummy signal is recorded on the low coercive force layer.

The recording current at this time is set to be sufficient to magnetize the upper low coercive force layer of the magnetic recording medium, but insufficient to magnetize the lower high coercive force layer.

Note that for signal input, a dummy signal may be first recorded in the low coercive force layer, and then a regular signal may be recorded in the high coercive force layer. FIG. 2 shows the qualitative relationship between the recording current and reproduction output of the high coercive force layer and the low coercive force layer in this case.

When a magnetic card recorded in this way is played back, the normal recorded signal in the high coercive force layer and the dummy signal in the resistive magnetic layer are detected as a superimposed signal, and it is impossible to detect which signal is the normal signal. . Therefore, it is difficult to reproduce official records using transfer methods or thermal transfer methods.

Next, when actually using the magnetic recording medium of the present invention, a reading method is performed using a reading device having three magnetic heads, as shown in FIG. 3, for example.

That is, first, in the "going" step 24, the regular signal and dummy signal recorded by the first magnetic head 21 are read simultaneously. Next, the second magnetic head 22 demagnetizes the dummy signal. Then, the third magnetic head 23 reads the regular signal.

Next, in the "return" step 25, a new regular signal is written in the third magnetic head, and the new data is checked when passing through the second magnetic head again.Finally, a dummy signal is sent to the low coercive force layer in the first magnetic head. The feature is that the data is recorded and carried out of the device, and then returned to a magnetic card that can be prevented from being duplicated in the same way as before it was inserted into the device.

<Example> Next, the present invention will be explained in detail with reference to examples.

Example 1 A magnetic paint with high coercive force consisting of formulation 1 shown below was applied to a coating thickness of 13 um on a substrate consisting of a polyester film kneaded with titanium oxide having a thickness of 188 um, and on top of this a magnetic coating composition from formulation 2 was coated to a coating thickness of 13 um. A magnetic paint with a low coercive force is rolled out and laminated to a coating thickness of 10 um, and then gravure coated with white gravure ink to form a protective layer, and a predetermined pattern is printed on the surface. A magnetic card was made.

Mixture 1 Mixture 2 This magnetic card has a gap of 30uII + 1 track width of 4
Recording current 600n+A with 11II11 magnetic head
A regular signal was recorded at an FM recording density of 2103 PI. Furthermore, a dummy signal was recorded using the above head at 100 RIA and at the same <FM recording density of 2108 PI. The relationship between the recording current of the magnetic card and the reproduction output obtained in this case is shown in FIG. 4, and a graph with two reproduction output peaks was obtained.

When this recorded magnetic card was reproduced using a normal reading device, the regular signal was superimposed on the dummy signal and the regular signal could not be read. When this magnetic card is read by the reading device according to the present invention, the first magnetic head reads out a recording signal in which a regular signal and a dummy signal are superimposed, and the third
The magnetic head was able to read regular signals.

Example 2 A magnetic paint with high coercive force consisting of formulation 1 shown below was applied to a coating thickness of 15 µm on a substrate made of a polyester film kneaded with titanium oxide having a thickness of 188 µm, and then formulation 2 was applied on top of it to a coating thickness of 15 µm. A magnetic paint with a resistive magnetic force consisting of the following was coated and laminated to a coating thickness of 101 lI, and a protective layer was further provided in the same manner as in Example 1 to prepare a magnetic card.

Formulation 1 Formulation 2 Magnetic recording was performed on the obtained magnetic card in the same manner as in Example 1, and the relationship between the recording current and the reproduction output was as follows.
As shown in the figure, two reproduction outputs were also observed.

As a result of reproducing this recorded magnetic card with a normal reading device, the regular signal was superimposed on the dummy signal and could not be read, but it could be read with the reading device according to the present invention.

<Effects of the Invention> Since the present invention has the above configuration, it becomes impossible to easily sense a regular signal recorded on a magnetic recording medium.
Counterfeiting by thermal transfer or contact transfer methods can be prevented.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a magnetic recording medium used in the present invention;
Fig. 2 is a diagram showing the qualitative relationship between the recording current and reproduction output of the high coercive force layer and the low magnetic force layer according to the present invention, and Fig. 3 is a diagram showing the reading of a magnetic recording medium recorded by the magnetic recording method of the present invention. This is a schematic diagram of the mechanism, and FIG. 4 shows the relationship between recording current and reproduction output obtained by the embodiment of the present invention.

Claims (1)

[Claims] 1. A magnetic layer with high coercive force is provided on a substrate, magnetic layers with low coercive force are successively laminated directly thereon, and a protective layer is further provided on the magnetic layer with low coercive force. A magnetic recording medium comprising the steps of recording a regular signal on a high coercive force magnetic layer, recording a dummy signal on a low coercive force magnetic layer, and reading the regular signal. Recording method. 2. The magnetic recording method according to claim 1, wherein the step of reading the regular signal includes a step of demagnetizing the dummy signal.