JP2541855B2 - How to write data to magnetic card - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for writing data on a magnetic card.

[Prior Art] Magnetic cards are used everywhere because of their portability and ease of use, but sometimes a fraudulent effort to read recorded data and modify its contents becomes a social problem. In order to prevent such fraud, it is conceivable that a plurality of recording layers having different coercive forces are laminated on a substrate in the order of higher coercive force and data is recorded while selecting one of the recording layers with a certain standard. . In this way, it is possible to read the data, but it is not possible to modify the data because the recording layer in which the data is recorded is not known to those who try to illegally use the data.

When this magnetic card is, for example, a general prepaid card, when performing the collection process, after temporarily reading the stored data of the magnetic card and performing the withdrawal process corresponding to the usage fee,
The processed data is written back to the card and returned to the user. Recording in this case is performed while moving the card or the magnetic head, and the written result is such that 1 bit of information corresponds to a predetermined time width unit t as shown in FIG.

[Problems to be Solved by the Invention] However, when rewriting, the writing width is affected by the magnetic field due to previously written data and the direction of magnetization of the underlying layer, as shown in FIG. 4 (a). Variation occurs. On the other hand, when reading the written data, a peak position appears at the time of switching the magnetization direction. For this reason, the 4th data is affected by the previously written data.
The peak position shifts as shown in FIG. Since the read data is discriminated from the change in the peak position, the fact that the position is controlled by the previously written data causes a misread. Even if the writing width is reduced to increase the recording density, the writing width varies depending on the writing location, so the writing width becomes too narrow depending on the location, which also causes misreading, and the recording density cannot be increased. There wasn't.

[Means for Solving the Problems] In order to solve such problems, the present invention sequentially magnetizes layers having a high coercive force in a certain direction in order from a layer having a high coercive force.
In a layer adjacent to each other, a certain amount of direct current magnetization is performed so that the directions thereof are reversed, and then data is written in an arbitrary layer.

[Operation] In different recording layers, DC magnetization is performed in mutually opposite magnetic fields, the magnetic field affecting from the high coercive force side to the low coercive force side and the magnetic field on the low coercive force side cancel each other, and on the low coercive force side. The state is equivalent to the state where no magnetization is performed.

[Embodiment] FIG. 1 is a side view showing a magnetic card using the present invention, in which 1 is a recording layer having a high coercive force, 2 is a recording layer having a low coercive force,
3 is a protective layer and 4 is a substrate. Hereinafter, a case of recording data on the magnetic card configured as described above will be described.

The data recorded on the recording layer 2 having a low coercive force is read, and the data for which the necessary usage fee and the like have been deducted are already written on the recording layer 2 having a low coercive force of the magnetic card before being written. The recording layer is magnetized to eliminate the influence of written data. Therefore, as shown in FIG. 1, first, a first DC magnetic field is applied to the recording layer 1 having a high coercive force to perform magnetization in a fixed direction, and then a DC magnetic field in the opposite direction is applied to a low coercive force. In addition to the recording layer 2 of FIG. At this time, the magnetization amount of the low coercive force layer is set to a value that cancels the magnetic field appearing on the low coercive force side due to the influence of the high coercive force side. In this way, if the recording layer 1 having a high coercive force and the recording layer 2 having a low coercive force are magnetized by the DC magnetic field, both magnetic fields cancel each other on the low coercive force side, and it becomes equivalent to a state in which no magnetization is made at all. Become.

After the magnetic card is magnetized in this way, for example, when data is recorded on the recording layer 2 having a low coercive force, when a current having a predetermined value is applied to a head (not shown), the low magnetic field is reduced as shown in FIG. Data is recorded on the magnetic recording layer 2. At this time, the current value may be selected so that no data is recorded in the recording layer 1 having a high coercive force by the magnetic field generated by the current.

When data is recorded on the recording layer 1 having a high coercive force, recording is performed by a stronger magnetic field than when data is written on the recording layer 2 having a low coercive force.

As described above, since the data is written after setting the low coercive force recording layer to an equivalent state in which it is not magnetized at all, the peak position does not shift due to the already written data. Therefore, erroneous reading that has occurred due to the shift of the peak position as in the past does not occur.

Table 1 shows the values of the writing width when recorded in this way. In Table 1, the same direction magnetization is a state in which the high coercive force layer and the low coercive force layer are magnetized in the same direction, and the reverse direction magnetization is a case in which they are opposite to each other, and serves as a reference. The recording time width is 400 μs.

Conventionally, data was written from a recording layer having a high coercive force in a state in which a recording layer having a low coercive force is affected. Since the same-direction magnetization remains in a state of affecting the recording layer having a high coercive force to the recording layer having a low coercive force, it corresponds to the evaluation of the recording method by the conventional method. On the other hand, the reverse magnetization is the method of the present application and apparently has no effect on the recording layer on the high coercive force side to the recording layer on the low coercive force side (both magnetic fields cancel each other in the recording layer with low coercive force). It is correct).

As you can see from the average data, the conventional method gives 400
The data rise time is about 50 μs and the fall time is about 50 μs. Therefore, the peak position is shifted by about 100 μs. On the other hand, according to the method of the present application, the width written as shown in FIG.
The variation is within about s, and the peak position of the waveform shown in FIG. 2B, which is read out, is suppressed within the variation range of about 20 μs. Therefore, according to the method of the present application, the deviation of the peak position is suppressed and the variation of the recording width is reduced, so that the recording width can be uniformly reduced.
The recording density can be increased.

Note that the usage method for ensuring security described below is not the gist of the present application, but will be described for reference.
When recording is performed on the high coercive force recording layer as described above, the same data recorded on the recording layer on the high coercive force side is recorded on the low coercive force side. Therefore, if the data of the recording layer on the low coercive force side is read, all the data can be read. However, even if this is modified and overwritten on the recording layer on the low coercive force side, the previously recorded data remains on the recording layer on the high coercive force side. Are affected irregularly. This causes the same problem as described in the problems of the prior art, prevents normal use, and ensures security. However, this problem does not occur when used legally.

EFFECTS OF THE INVENTION As described above, according to the present invention, data is recorded after the magnetizations in the opposite directions are applied to the different recording layers. Therefore, the recording layer on the low coercive force side is magnetized. Data is written in a state equivalent to the absence of writing data, and the writing width does not fluctuate, so that there is an effect that erroneous reading does not occur. Further, since the writing width does not vary, even if the writing width is evenly reduced, there is no place where the writing width becomes extremely small, erroneous reading hardly occurs, and the recording density can be improved.

Further, when recording data on the recording layer on the high coercive force side, it can be performed in the same manner as recording data on the recording layer on the low coercive force side. After each of the recording layers is subjected to direct current magnetization in a fixed amount in opposite directions, the data is recorded on the recording layer on the high coercive force side by passing through the recording layer on the low coercive force side. In the case of recording data on the recording layer on the high coercive force side as well, like the data recording on the recording layer on the low coercive force side, there is an effect that the writing width does not vary, and thus erroneous reading does not occur.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a magnetic card to which the present invention is applied, FIG. 2 is a view showing a state in which data is recorded therein, and FIG. 3 is a view for explaining a data recording state. FIG. 4 is a diagram for explaining a recording method according to a conventional method. 1,2 ... Recording layer, 3 ... Protective layer, 4 ... Substrate.

Claims (1)

(57) [Claims] 1. A method for writing data to a magnetic card for writing data on a record carrier, wherein a plurality of recording layers having different coercive forces are laminated on a substrate in descending order of coercive force. A method for writing data to a magnetic card, characterized in that a predetermined amount of direct current is magnetized so that the directions thereof are reversed in adjacent layers, and then desired data is written in an arbitrary layer.