JPS63308725A - Magnetic recording medium and magnetic recording method thereof - Google Patents

Abstract

PURPOSE:To greatly prevent the ill use such as falsification by providing a magnetic recording part consisting of plural magnetic materials having different coercive forces and magnetizing at least two of said plural magnetic materials in different magnification directions. CONSTITUTION:The two magnetic layers 20, 22 having the different coercive forces are separated by a separating layer 24 and are protected by a protective film 26 formed thereon. The absence of the separating layer 24 is equally satisfactory. Magnetic recording is executed on the magnetic layers 20, 22 in the magnification directions different from each other with the two magnetic materials thereof, by which the data can be magnetically recorded at the recording density twice larger than heretofore. The positional relations between magnetic heads and magnetic stripes 14 at the time of the magnetic recording and the positional relations between the magnetic heads and the magnetic stripes at the time of reproduction are as shown in the figure. The magnetic head 30 for strong magnetic field used for the magnetic recording and the magnetic head 32 for weak magnetic fields vary in the magnification direction and the angle theta between each is preferably about 3-5 deg.. On the other hand, the magnetic heads 34, 36 to be used for reproduction are installed in the directions conforming to the magnification directions respectively by the magnetic head 30 for the strong magnetic field and the magnetic head 32 for the weak magnetic field at the time of the recording.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium such as a magnetic card and a magnetic recording method thereof.

[Conventional technology]

A magnetic card that magnetically records a predetermined signal on a magnetic material is ≦
It is widely used and known as a long rod card, ID card, credit card, and various prepaid cards. , 2, etc., if there is any unauthorized use such as forgery, alteration, or theft, it will cause great damage, so a function to prevent unauthorized use is extremely important.

In particular, if personal data, such as a personal identification code, is simply magnetically recorded on the magnetic stripe portion, it can be decoded with a simple device such as a magnetic viewer, and it can be easily copied using methods such as magnetic transfer. The magnetic transfer method involves placing a genuine card and a counterfeit card upside down so that their magnetic surfaces are brought into close contact with each other, and heating the counterfeit card magnetic layer to a temperature of one curie or higher, or heating the counterfeit card magnetic layer to a temperature higher than the coercive force of the counterfeit card magnetic layer. This is a method of applying a bias magnetic field to transfer the magnetization pattern of a genuine card to a counterfeit card.This transfer method is used for magnetic recording media that is magnetized by arranging the gap of the magnetic head in a direction perpendicular to the longitudinal direction of the magnetic stripe. According to
The same data can be reliably transferred to a counterfeit card.

As a method to hide the recorded data in the magnetic recording layer and to prevent magnetic transfer, a high magnetic permeability magnetic layer is provided on the data recording layer, and the magnetic flux generated from the surface of the data recording layer is transferred to the high permeability magnetic layer. A method of absorbing recorded data so that it does not escape to the outside and making it impossible to read the recorded data with a normal magnetic reader or magnet viewer (for example, JP-A-55-
No. 93514, Japanese Unexamined Patent Publication No. 60-219636, Japanese Unexamined Patent Publication No. 1987-219636
6-51) No. 36), a low coercive force magnetic layer for recording false data is provided on a high coercive force magnetic layer for recording true data,
Methods for preventing reading of true data (for example, Japanese Patent Application Laid-open No. 5
4-85007, JP-A-60-219635, and JP-A-61-145727).

[Problem that the invention seeks to solve]

Although the conventional example described above can prevent reading of recorded data and transfer of recorded signals by the magnetic viewer to some extent, it is still not perfect. In the former case, the recorded data can be easily observed using a magnetic viewer by applying a uniform magnetic field to the high magnetic permeability layer under the same conditions as during reproduction.

In addition, in the latter case, in order to reproduce the true data in the high coercive force magnetic layer, it is first necessary to erase the false data in the low coercive force magnetic layer, and then, after reproduction, the false data in the low coercive force magnetic layer is again transferred to the low coercive force magnetic layer using a weak magnetic field. Data must be recorded, making playback operations cumbersome. Furthermore, in the latter case, the true data can be easily read by erasing the fake data, and counterfeiting is also possible.
It is not so difficult to do this, as it is sufficient to prepare a magnetic material for recording true data and transfer the true data thereto, and to prepare a magnetic material with an appropriate low coercive force for the recording layer for false data.

Basically, the higher the recording density of magnetic recording, the more difficult it becomes for those who do not have a compatible reading device to read the recorded data and to make copies. No solution can be obtained.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic recording medium with a high forgery prevention function and a magnetic recording method thereof.

A second object of the present invention is to provide a magnetic recording medium that is difficult or impossible to observe and read with a magnetic viewer, and on which magnetic transfer is impossible or difficult, and a recording method thereof.

[Means for solving problems]

The magnetic recording medium according to the present invention has a magnetic recording section made of a plurality of magnetic materials having different coercive forces, and at least two of the plurality of magnetic materials are magnetized in different magnetization directions.

Further, the magnetic recording method according to the present invention uses a magnetic recording medium having a magnetic recording section made of a plurality of magnetic materials having different coercive forces, and in the magnetic recording section, two or more of the plurality of magnetic materials are different from each other. The method is characterized in that a magnetic field is applied that gradually becomes smaller so that a desired magnetization pattern is formed in the magnetization direction, and a signal is magnetically recorded.

[Effect]

Magnetic materials with different coercive forces can be given different magnetization states according to the different coercive forces. That is, a magnetic field that can saturately magnetize a magnetic material with the highest coercive force is applied, and the magnetic material is magnetized into a desired magnetization pattern. A magnetic field capable of magnetizing the magnetic material with the second highest coercive force is applied to magnetize the magnetic material with the second highest coercive force into a predetermined magnetization pattern. By sequentially magnetizing magnetic materials with lower coercive forces into desired magnetization patterns in this manner, separate magnetization patterns can be imparted to each of the magnetic materials with different coercive forces. However, in order to be able to reproduce each magnetization pattern independently, the magnetization direction of each magnetization pattern is set separately. When reproducing a magnetization pattern in a specific angular direction, a magnetic head with a gap suitable for that angular direction may be used.

During playback, cross-magnetization from magnetization patterns in other angular directions
There is quite a bit of talk, which leads to deterioration of S/N, but this is due to the angle formed by the magnetization direction of each magnetization pattern,
By selecting the mixing ratio and abundance ratio of the magnetic materials such that the residual magnetic flux density of each magnetic material and the reproduction voltage from each magnetic material in the magnetized state are approximately the same, the residual magnetic flux density becomes negligible and becomes a practical hindrance. There is no.

This makes it possible to record at a density more than twice that of the conventional example, making counterfeiting that much more difficult. Furthermore, since a plurality of magnetization patterns are multiplexed and recorded, even when observed with a magnet viewer, the pattern becomes mesh-like or moiré-like and cannot be deciphered.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings. In the present invention, a plurality of magnetic materials having different coercive forces are used, but in the following embodiments, a case will be described in which two types of magnetic materials are used.

FIG. 1 shows a front view of a magnetic card to which the present invention is applied,
The magnetic card 10 consists of a base 12 made of plastic, paper, etc., and a magnetic stripe 14 for magnetic recording.

2A[m shows a cross-sectional view of the first embodiment of the magnetic strip 14 portion, 16 is a magnetic layer in which two types of magnetic materials with different coercive forces are dispersed and mixed and bonded with a binder. is a protective film for protecting the magnetic layer 16. FIG. 2B is a cross-sectional view of another embodiment in which two magnetic layers with different coercive forces are stacked, 20 and 22 are magnetic layers with different coercive forces, and 24 is a layer for separating magnetic layers 20 and 22. Separation layer 26 is a protective film 0 Separation layer 24 may be omitted; protection W1) B, 26 may cover the upper surface of base 12; Of course, a shield layer may be provided.

In the embodiment illustrated in FIGS. 2A and 2B, the magnetic layer 1
By performing magnetic recording in different magnetization directions in the magnetic materials of the magnetic layers 20 and 22 having different coercive forces, data can be magnetically recorded at twice the recording density of the conventional method. The rising right line 28 and the rising left line 29 of the magnetic stripe 14 in FIG. 1 show an example of the magnetization pattern. FIG. 3(a) shows the magnetic head and the magnetic stripe 1 during magnetic recording.
Figure 3 shows the positional relationship between the magnetic head and the magnetic stripe during reproduction. In both cases, the magnetic stripe 14 runs in the direction of the arrow. The magnetic heads 34 and 36 used for reproduction have different magnetization directions, and the angle θ between them is preferably about 3 to 5 degrees for reasons described later.On the other hand, the magnetic heads 34 and 36 used for reproduction are used for recording The magnetic head 30 for a strong magnetic field and the magnetic head 32 for a weak magnetic field are installed in a direction that matches the direction of magnetization at the time.

During magnetic recording, data is first magnetically recorded by applying a strong magnetic field sufficient to saturate the high coercive force magnetic material using the strong magnetic field magnetic head 30. Next, the weak magnetic field magnetic head 32 applies a weak magnetic field that can magnetize the magnetic material with low coercive force but does not affect the magnetization state of the magnetic material with high coercive force to read other data. Multiplex magnetic recording. In FIGS. 3(a) and 3(b), the magnetization pattern for the high coercivity magnetic material is shown by a line rising to the right, and the magnetization pattern for the low coercive force magnetic material is shown by a line rising to the left. In this case, 1 track has 2 normal
Can record twice as much data. As a result, the recording density can be doubled, and overlapping data can be hidden from each other.

During reproduction, the reproduction head 34.3 is moved in the gap direction according to the magnetization direction of the magnetic material of each coercive force, regardless of the order.
6, the recorded data in each magnetization direction is reproduced. Although magnetic recording in a magnetization direction that does not correspond to that of the reproducing head causes cross talk, select magnetic materials, mixing ratios, or abundance ratios so that the induced voltage in the magnetic head due to residual magnetic flux is the same for each magnetic material. This will not interfere with the reproduction of the digital code, as will be explained in detail below.

For example, if the magnetic moment of the magnetized region of the high coercive force magnetic material is a, and the △ magnetic moment of the magnetized region of the low coercive force magnetic material is b, then the magnetization pattern of the high coercive force magnetic material is the first with respect to the binary code "010". It is assumed that the magnetization pattern of a magnetic material with a low coercive force is expressed as shown in FIG. 4(a) for a binary code "101" as shown in FIG. 4('b). Further, right direction magnetization is + and left direction magnetization is -. When the “1” code portion of the high coercive force magnetic material overlaps the “0” code portion of the low coercive force magnetic material,
The magnetic moment of each part of the composite part is as shown in FIG. 5(a).

Figure 5(b) shows the direction of the composite vector. Needless to say, such overlapping magnetization patterns are created by mixing magnetic powders with different coercive forces, as in the structure shown in Figure 2A. Magnetism] 1) It may be caused by the individual magnetic materials of 6, or it may be caused by separate magnetic layers 20 and 22 having different coercive forces, as in the structure shown in FIG. 2B.

When such overlapping magnetization patterns occur, for example, if reproduction is performed in the gap direction according to the magnetization pattern with high coercive force using 7D 34, the magnetization pattern shown in FIG. 5(C) will be reproduced from a macroscopic perspective. is affected by the magnetization pattern of the low coercive force magnetic material by +Δb/4 and -b/4 compared to the original single magnetization pattern. Select magnetic materials so that the reproduction voltage from the magnetization pattern of each magnetic material is about the same (and the crosstalk from other magnetization patterns is ±1
74, and there is no problem in reproduction signal processing. This is the same even when reproducing the magnetization pattern of a magnetic material with low coercive force.

Also, as the intersection angle between each magnetization pattern approaches 90°, it becomes less susceptible to the influence of other magnetization patterns, but increasing this intersection angle makes it easier to decipher the magnetization patterns with a magnet viewer, etc. Therefore, it is preferable that the intersection angle is as small as possible. When employing the FM recording method, ten magnetization and one magnetization always alternate, so by increasing the recording density, the influence from other magnetization patterns can be reduced.

Table 1 shows the relationship between commonly available magnetic materials and their coercive forces.
Available for 6,20.22.

Barium ferrite of about 3000 (Oe), about 3
In an example in which 00 (Oe) gamma ferrite is used, the former is magnetized in a direction perpendicular to the longitudinal direction of the magnetic stripe, and the latter is magnetized at an intersecting angle of 1 to 6 degrees with respect to the magnetic stripe, it is reproducible. When observed with a magnetic viewer made by Thomson, France, it was found that when the intersection angle was 5°, it appeared like a dot, and when it was 30°, it became moiré, and it was virtually impossible to decipher it using a magnetic viewer.

In addition, in the embodiment shown in FIG. 2A, compared to the embodiment shown in FIG. 2B,
Although it is easy to legally manufacture, counterfeiting requires analysis of the composition, mixing ratio, etc., and has a high anti-counterfeiting function.

Further, decoding by a magnet viewer becomes easy, but as a modification of the present invention, as shown in FIG. 6, the signals (true data and/or (false data) may be magnetically recorded. In this case, decoding becomes relatively easy due to the reduction in recording density, but a person attempting to falsify or counterfeit must prepare a magnetic head with a gap direction that corresponds to a different magnetization direction. It has the appropriate ability to prevent forgery, alteration, and deciphering.

〔Effect of the invention〕

As can be easily understood from the above description, according to the present invention, since data is recorded at a higher density than in the conventional example, forgery, alteration, and deciphering are made that much more difficult, and the fraud prevention function is high. In the case of multiple recording, it is almost impossible to decipher it with a magnetic viewer. Since each magnetic record with a different magnetization direction can be reproduced separately, only the true data can be easily reproduced even if one or more of the records are regarded as true data and the others as false data. Of course, the counterfeiter
The anti-counterfeiting function is extremely high because it cannot be counterfeited unless one knows which records are the true data.

Multiplex recording allows extremely high recording density, and from this point of view, it is difficult to forge or falsify.

In the present invention, since a plurality of magnetization patterns are recorded at angles, even if a counterfeit recording medium is brought into close contact with a genuine recording medium upside down in order to be transferred by the above magnetic transfer method, the magnetization patterns will not cross each other. The angle will be reversed left and right,
It is impossible to copy the same data.

Ultimately, in order to counterfeit the magnetic recording medium according to the present invention,
First, it is necessary to decipher each of the multiple recorded magnetization patterns. Second, in order to magnetically record the same recording pattern as the one that was deciphered, it is necessary to analyze multiple magnetic materials with different coercive forces that make up the magnetic recording area of the authentic recording medium. The magnetic material is applied to the base so that the magnetic material becomes opaque. This is as difficult, if not more difficult, than obtaining raw, authentic recording media. Thirdly, for each magnetic material, a corresponding magnetization pattern must be magnetically recorded at a corresponding angle, which is not very easy for counterfeiters.

For the above purpose, fairly high-grade equipment is required, and the chances of unauthorized use such as forgery or alteration can be substantially reduced.

Table 1 Figure 2A is a sectional view of the first embodiment of the present invention, Figure 2B is a sectional view of another embodiment of the invention, and Figure 3 shows the relationship between the recording head, the reproducing head, and the magnetic stripe. 4 shows an example of a magnetization code for a high coercivity magnetic material and a magnetization code for a low coercivity magnetic material. FIG. 5 is an explanatory diagram of cross talk between magnetization patterns. FIG. FIG. 3 is a diagram showing a magnetization pattern.

10-・Magnetic card 12・-Base 14-・Magnetic stripe 16,20.22-・Magnetic layer 18,26-
Protective film 24...-Separation layer 28.29-Magnetization pattern 30.32--Magnetic head for recording 34°36...-
Reproduction head patent applicant Totsu''pa) 4 sand type company representative patent attorney Tsuneo Naka 1-aku) 2F'2./' Figure 1 Figure 2A Figure 28 Figure 3 (a) (b) Figure 4 (a) (b) (c) Figure 5 Figure 6

Claims (7)

[Claims] (1) A magnetic recording medium comprising a magnetic recording section made of a plurality of magnetic materials having different coercive forces, and at least two of the plurality of magnetic materials are magnetized in different magnetization directions. (2) The magnetic recording medium according to claim (1), wherein the magnetic recording section is made of a mixture of a plurality of magnetic materials having different coercive forces. (3) The magnetic recording medium according to claim (1), wherein the magnetic recording section is a stack of magnetic layers made of magnetic materials having different coercive forces. (4) By applying a magnetic field that gradually decreases to a magnetic recording section made of a plurality of magnetic materials having different coercive forces so that two or more of the plurality of magnetic materials have a desired magnetization pattern in different magnetization directions. , a magnetic recording method characterized by magnetically recording signals. (5) The method according to claim (4), characterized in that signals are multiplexed and recorded. (6) The method according to claim (4) or (5), wherein the magnetic recording section is a mixture of a plurality of magnetic materials having different coercive forces. (7) The method according to claim (4) or (5), wherein the magnetic recording section is a stack of magnetic layers made of magnetic materials having different coercive forces.