JP2660966B2 - Magnetic recording medium authenticity discrimination method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a true magnetic recording medium utilizing a difference in copy amount by applying different demagnetization between alternating current and direct current to a multilayer magnetic recording medium comprising an upper layer and a lower layer having different coercive forces. It relates to a false discrimination method.

[0002]

2. Description of the Related Art A magnetic card reader for reading recorded data or writing data is used for a magnetic card such as a cash card and a credit card. Forgery of the magnetic card is prevented. Countermeasures are urgently needed. Conventionally, countermeasures against this type of forgery have been taken by improving the signal system for recording data on the magnetic card, improving the structure of the magnetic head or the magnetic recording medium of the magnetic card.

[0003]

However, since the surface of the magnetic recording medium is magnetized according to the magnitude of the recording signal, it can be easily read and written by a magnetic viewer and a magnetic head. Therefore, in order to prevent forgery and the like, improvements have been made in the recording signal system, the structure of the magnetic head, the magnetic recording medium, and the like. However, these methods are not perfect alone, but these methods are combined. This is complicated and has drawbacks that are not yet complete.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for determining the authenticity of a magnetic recording medium which can determine the authenticity of the magnetic recording medium by a simple method.

[0005]

According to the present invention, the lower layer 2 is provided.
After magnetic recording on the multilayer magnetic recording medium 1 comprising a magnetic material having a high coercive force and a lower coercive force in the upper layer 3 than the lower layer 2, only the upper layer 3 is moved beyond the magnetic gap length of the magnetic head 4 for recording. With the AC degaussing head 7 having a long gap length,
Demagnetization is performed so that the reproduction output of the information signal of the upper layer 3 is reduced. Only the upper layer 3 is demagnetized by the DC degaussing head 8, and the magnitude of the reproduced output signal before and after the DC demagnetization is compared to determine the trueness. A method for determining the authenticity of a magnetic recording medium, which is characterized by determining falseness, is obtained.

[0006]

The AC output demagnetization is performed so that only the upper layer 3 is demagnetized while keeping the true information of the lower layer 2 unchanged, so that the combined reproduced output waveform of the lower layer 2 and the upper layer 3 becomes small as shown in FIG. Therefore, unless the demagnetization condition of the upper layer 3 is known, true information cannot be read.

On the other hand, when the true information is read, if only the upper layer 3 is demagnetized immediately before reading, a large output reproduction waveform can be obtained as shown in FIG.

That is, according to the present invention, the magnetic recording medium has a multilayer structure, the level of AC demagnetization is arbitrarily set in advance, and the scramble information is superimposed on the true information. Is removed by combining the DC demagnetization, and the authenticity of the magnetic recording medium is determined.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for determining the authenticity of a magnetic recording medium according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, a magnetic recording medium 1 used in the present embodiment has a low coercive force magnetic material as an upper layer 3 and a high coercive force magnetic material having a coercive force two to three times that of the upper layer 3. This is a multilayer magnetic recording medium having a lower layer 2. When an information signal is applied to the magnetic head 4 for recording, the magnetic recording medium 1 is magnetized according to the signal by the magnetic flux 6 generated in the magnetic gap 5. As shown in FIG. 2, the AC degaussing head 7 having a gap length 100 times larger than the magnetic gap 5 of the recording magnetic head 4 demagnetizes the low coercivity medium of the upper layer 3 from above. Is reduced to some extent, and a magnetic card having the magnetic recording medium 1 having the reproduced output waveform as shown in FIG. 3 is obtained.

When reading information from this magnetic card,
When only the low coercivity medium of the upper layer 3 is demagnetized by the reproducing magnetic head or the DC degaussing head 8 having the same magnetic gap 5 as shown in FIG.
As shown in FIG. 5, a signal larger than the information signal output voltage value when the AC is demagnetized is read.

That is, in the AC degaussing by the AC magnetic head 7 having a large magnetic gap 5, the upper layer 3 having a low coercive force is used.
The magnetic flux reversal area is widened, and a specific demagnetization pattern is generated because the magnetic flux density varies depending on the location. On the other hand, in the DC degaussing by the DC degaussing head 8 having the same magnetic gap length as the reproducing magnetic head, the upper layer 3 is completely degaussed, so that a difference occurs in the reproducing output voltage. Therefore, the magnetic card is demagnetized by AC during recording and degaussed by DC during reproduction, and by comparing the signal magnitudes before and after the discrimination, it is possible to distinguish a counterfeit card from a legitimate card and to read information.

[0013]

As described above, the present invention relates to an AC degaussing head having a gap length longer than the magnetic gap length of a recording magnetic head, and only the upper layer after magnetic recording on a multilayer magnetic recording medium. The demagnetization is performed so that the reproduction output of the information signal of the upper layer is reduced, only the upper layer is demagnetized by the DC degaussing head, and the magnitude of the reproduced output signal before and after the DC demagnetization is compared to obtain a magnetic recording medium. Can be determined as true or false.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a magnetization pattern of a magnetic recording medium when an information signal is recorded in a method for determining the authenticity of a magnetic recording medium according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a magnetization pattern when AC magnetic demagnetization is performed in FIG. 1;

FIG. 3 is a reproduction output waveform diagram in which a magnetization pattern in FIG. 2 is read by a reproduction magnetic head.

FIG. 4 is a schematic diagram of a magnetization pattern when DC magnetic degaussing is performed when a recorded signal is read.

FIG. 5 is a reproduction output waveform diagram in which a magnetization pattern in FIG. 4 is read by a reproduction magnetic head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic recording medium 2 Lower layer 3 Upper layer 4 Recording magnetic head 5 Magnetic gap 6 Magnetic flux 7 AC degaussing head 8 DC degaussing head

Claims (1)

(57) [Claims] A magnetic head for recording, after magnetic recording, on a multi-layer magnetic recording medium comprising a magnetic material having a high coercive force in a lower layer and a coercive force lower in the upper layer than the lower layer. 4, the degaussing is performed by the AC degaussing head 7 having a gap length longer than the magnetic gap length of the upper layer 3 so that the reproduction output of the information signal of the upper layer 3 is reduced. A method for determining the authenticity of a magnetic recording medium, comprising comparing the magnitude of a reproduced output signal before and after DC demagnetization to determine the authenticity.