JPH0715726B2 - Security magnetic recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a security magnetic recording system which utilizes different decoupling amounts of alternating current and direct current in upper and lower layers having different coercive forces and utilizes the difference in copying amount. .

<Prior Art> A magnetic card reader for reading or writing recorded data is used for magnetic cards such as cash cards and credit cards. There is an urgent need. Conventionally, as a countermeasure against this type of forgery, improvements have been made in the signal system when recording data on a magnetic card, the structure of the magnetic head or the magnetic medium of the magnetic card.

<Problems to be Solved by the Invention> However, since the surface of the magnetic medium is magnetized in accordance with the magnitude of the recording signal, reading and writing can be easily performed by a magnetic viewer and a magnetic head. Therefore, the recording signal system, the structure of the magnetic head, the magnetic medium, etc. have been improved in order to prevent counterfeiting, etc. However, they are not perfect by themselves, and these methods are combined and complicated, which is not perfect. There are drawbacks.

<Means for Solving Problems> In the present invention, except for such drawbacks of the prior art, a multi-layer magnetic medium card having a lower layer coated with a magnetic material having a high coercive force and an upper layer having a lower coercive force than the lower layer is used for magnetic recording. This is a security magnetic recording method that can identify the magnetic card that is demagnetized by AC demagnetization of the upper layer of the rear upper layer and demagnetized by DC during reproduction and then magnetically reproduced.

<Operation> The reproduced output is small and the waveform is
As shown in Fig. 5, when DC demagnetization is performed, the reproduction output is large and the waveform is as shown in Fig. 5. The difference in the waveform and the difference in the output of the waveform are caused because the card has two layers and the reading condition of the information signal is controlled by changing the AC degaussing DC degaussing magnetic head. A specific signal cannot be output unless such a specific condition is satisfied. This is used to prevent counterfeiting of magnetic cards.

<Embodiment> An embodiment of the security magnetic recording system of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the magnetic medium 1 used in the present invention is a multi-layer having a low coercive force magnetic material as an upper layer 3 and a high coercive force magnetic material having a coercive force of 2 to 3 times that of the upper layer 3 as a lower layer 2. It is a magnetic medium. When an information signal is applied to the recording magnetic head 4, the magnetic flux 6 generated in the magnetic gap 5 magnetizes the magnetic medium 1 according to the signal. As shown in FIG. 2, the low coercive force medium of the upper layer 3 is degaussed from above by the AC degaussing head 7 having a gap length 100 times larger than the magnetic gap 5 of the recording magnetic head 4, so that the reproduction output of the information signal of the upper layer 3 is performed. Is reduced to some extent and has a reproduction output waveform as shown in FIG.
You can get the magnetic card.

When information is read from this magnetic card, when the reproducing magnetic head 8 or the DC demagnetizing head 9 having the same magnetic gap 5 as this, demagnetizes only the low-holding medium of the upper layer 3 as shown in FIG. As the voltage value, as shown in FIG. 5, a signal larger than the information signal output voltage value when the AC demagnetization is performed is read.

That is, in the AC degaussing with the AC magnetic head 7 having a large magnetic gap 5, the magnetic reproduction of the low coercive force medium of the upper layer 3 is hard to occur, and when the DC degaussing head 8 has the same magnetic gap length as that of the reproducing magnetic head, the upper layer 3 is not erased. Magnetic reproduction of No. 3 is likely to occur, which causes a difference in reproduction output voltage. Therefore, the magnetic card is degaussed with alternating current during recording and degaussed with direct current during reproduction, and by comparing the signal magnitudes before and after that, it is possible to distinguish between a forged card and a legitimate card, and it is possible to read information.

<Effects of the Invention> As described above, according to the present invention, the forgery of the magnetic card is prevented by utilizing the difference in the magnetic copy amount between the AC demagnetization and the DC demagnetization for the low coercive force medium layer of the upper layer 3. It

[Brief description of drawings]

FIG. 1 is a pattern pattern diagram of magnetization of a magnetic medium when an information signal is recorded by the magnetic recording method of the present invention, and FIG. 2 is a pattern pattern diagram of magnetization when AC magnetic demagnetization in FIG. FIG. 3 is a reproduction output waveform diagram in which the magnetization pattern in FIG. 2 is read by a reproduction magnetic head, FIG. 4 is a pattern diagram of magnetization when DC magnetic demagnetization is performed when reading a recorded signal, and FIG. FIG. 5 is a reproduction output waveform diagram in which the magnetization pattern in FIG. 4 is read by a reproduction magnetic head. In addition, 1: magnetic 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)

[Claims] 1. A lower layer 2 has a high coercive force and an upper layer 3 has said lower layer 2.
After the magnetic recording on the multi-layer magnetic medium 1 made of a magnetic material having a lower coercive force, only the upper layer 3 is subjected to AC degaussing for writing, and then only the upper layer 3 is degaussed for direct reading by magnetic reproduction. Recording method.