JPH0715727B2 - How to identify a magnetic card - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for preventing forgery of a magnetic card, and more particularly to a method for discriminating between a legitimate magnetic card and a forged card.

[Prior Art] Recently, various magnetic cards that do not specify a user have been used. Data indicating the amount of money is recorded on the magnetic recording layer of the magnetic card. However, this type of magnetic card may be easily forged by data transfer or the like.

Therefore, conventionally, there has been proposed a magnetic card in which a magnetic recording layer is composed of two layers, a low coercive layer and a high coercive layer, and data is recorded in the high coercive layer while interference information is recorded in the low coercive layer. According to this magnetic card, it is difficult to forge by copying, etc.
It is effective in preventing forgery of magnetic cards.

[Problems to be Solved by the Invention] However, the latter magnetic card is difficult to manufacture because it records interference information in addition to data on the magnetic recording layer. Moreover, the data must be retrieved separately from the interfering information, which makes it unavoidable that the device for reading the magnetic card becomes complicated and expensive.

Therefore, an object of the present invention is to provide a method for identifying a magnetic card that can effectively prevent the use of a forged magnetic card, and that does not require an expensive device for writing data to the magnetic card and reading the data. To do.

[Means for Solving the Problems] According to the present invention, a low coercive force layer and a high coercive force layer are provided.
In a method of distinguishing a regular magnetic card having a magnetic recording layer having a layered structure and having data recorded in the high coercive force layer from another forged card, the data of the magnetic card is reproduced to perform a first reproduction. To obtain an output, to apply a transfer magnetic field to the magnetic card such that the data can be transferred to the low coercive force layer, and after applying the transfer magnetic field, reproduce the data of the magnetic card to obtain a second To obtain the reproduction output of the above, comparing the first and second reproduction outputs with each other, and recognizing only the one in which the second reproduction output is increased by a certain amount as compared with the first reproduction output as the regular magnetic card. And thereafter erasing the recording of the low coercive force layer, a method for identifying a magnetic card is obtained.

[Operation] When the transfer magnetic field is applied to the above-mentioned regular magnetic card, the data in the high coercive layer is transferred to the low coercive layer. As a result, the second reproduction output becomes larger than the first reproduction output. That is, the reproduction output increases after the transfer magnetic field is applied. On the other hand, in the case of a counterfeit card, the reproduction output does not increase after the transfer magnetic field is applied. Therefore, a legitimate magnetic card and a forged card can be distinguished. After this identification, the magnetic card is restored to the state in which data is recorded only in the high coercive force layer.

[Example] FIG. 1 shows a magnetic card used in an example of the present invention, in which 1 is a card substrate, a material is a polyester film, and a thickness is 188 μm. 2 is a high coercive force layer, the coercive force is formed by using the magnetic powder of SrO-6Fe ₂ O ₃ of 30000Oe, a thickness of 40 [mu] m. 3 is a low coercive force layer, the holding force is formed by using a magnetic powder of Ba-6Fe ₂ O ₃ of 7000e, thickness of 18 [mu] m.

FIG. 2 is a sectional view in which the recording / reproducing head 4 having a head gap of 45 μm is arranged on the low coercive force layer side of the magnetic card of FIG. The recording / reproducing head 4 can record data on a magnetic card and reproduce the data.

FIG. 3 shows the recording / reproducing characteristics using the recording / reproducing head 4 in the case where the low coercive force layer and the high coercive force layer of FIG. This is the recording / playback characteristic of the coercive force layer.

Data is recorded on the magnetic card shown in FIG. 1 by causing the recording / reproducing head 4 in FIG. 2 to generate the recording magnetic field A shown in FIG. As can be seen from FIG. 3, the recording state of the magnetic recording layer in this case is such that the high coercive force layer 2 is saturated and magnetized while the low coercive force layer 3 is almost not magnetized. Therefore, while the reproduction output in the high coercive force layer 2 is the highest, the reproduction output in the low coercive force layer 3 is hardly obtained.

In the above-described magnetic card in the recorded state, when the recording / reproducing head 4 reproduces the magnetic field after applying the magnetic field, the reproduction output characteristic shown in FIG. 4 is obtained. Fourth
In the figure, the maximum point of the reproduction output when the applied magnetic field is around 1.5 KGauss is about four times as large as the reproduction output when the applied magnetic field is zero. This is because the magnetization of the high coercive force layer was converted to the low coercive force layer by the applied magnetic field and the reproduction output was improved. Therefore, the applied magnetic field at this time is called a transfer magnetic field here.

The magnetic card is identified using the above principle. Less than,
An example of the procedure will be described.

First, the data of the magnetic card is reproduced by the recording / reproducing head 4. The reproduction output at this time is called a first reproduction output. Next, a transfer magnetic field of about 1.5 KGauss is applied to the magnetic card. As a result, in the case of a regular magnetic card, the data is transferred to the low coercive force layer. Then, the data of the magnetic card is reproduced by the recording / reproducing head 4 again. The reproduction output at this time is called a second reproduction output. This second playback output is the first
Compared with the playback output of. The second reproduction output is the same as the first reproduction output when the magnetic card is a counterfeit one, but is significantly larger than the first reproduction output when the magnetic card is a genuine one, for example, about 4 times increase. Therefore, by recognizing only the one in which the second reproduction output is increased by a certain amount as compared with the first reproduction output as the legitimate magnetic card, the legitimate magnetic card and the counterfeit magnetic card can be discriminated.

After that, the magnetic card is returned to the original state in which the data is recorded only on the high coercive force layer. That is, the recording on the low coercive force layer is erased. This can be done by applying a magnetic field stronger than the transfer magnetic field, for example, a magnetic field of about 3.0 KGauss to the magnetic card. Data may be re-recorded on the magnetic card by the recording magnetic field A.

[Effects of the Invention] As described above, according to the present invention, it is possible to effectively prevent the use of a forged magnetic card, and moreover, an expensive device is required for writing data to the magnetic card and reading the data. It is possible to provide a method of identifying a magnetic card without a problem.

[Brief description of drawings]

FIG. 1 is a perspective view of a magnetic card used in an embodiment of the present invention, FIG. 2 is a side view in which a recording / reproducing head is arranged on the surface of the magnetic card, and FIG. 3 is a recording magnetic field dependence of reproduction output. The graph shown in FIG. 4 is a graph showing the dependence of the reproduction output on the applied magnetic field. 1 ... Card substrate, 2 ... High coercive force layer, 3 ... Low coercive force layer, 4 ... Recording / reproducing head.

Claims (1)

[Claims] 1. A normal magnetic card having a two-layer magnetic recording layer consisting of a low coercive force layer and a high coercive force layer and having data recorded on the high coercive force layer is discriminated from other counterfeit cards. In the method, reproducing the data of the magnetic card to obtain a first reproduction output, applying a transfer magnetic field to the magnetic card to the extent that the data can be transferred to the low coercive force layer, Obtaining a second reproduction output by reproducing the data of the magnetic card after applying a magnetic field, comparing the first and second reproduction outputs with each other, and comparing the second reproduction output with the first reproduction output. Also, the method for identifying a magnetic card, which includes recognizing only the magnetic card that has increased by a certain amount as the regular magnetic card, and then erasing the record of the low coercive force layer.