JP2687344B2 - Magnetic medium and its confirmation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic medium and a confirmation method thereof, and more specifically, a magnetic medium to which a predetermined signal is added by a magnetic material and its authenticity are confirmed. Regarding the method. [Prior Art] A magnetic card for magnetically recording a predetermined signal on a magnetic material is
It is widely used for bank cards, ID cards, and various prepaid cards (prepayment cards), and is well known. In such a magnetic card, there is a possibility of causing great damage in the case of unauthorized use such as forgery, alteration, and plagiarism. Therefore, the function of preventing the unauthorized use is extremely important. In particular, when personal data, such as a personal identification code, is simply magnetically recorded on the magnetic stripe portion, it can be easily read by a simple device and can be copied. It is desired and various proposals have been made. For example, as an identification means for determining whether or not it is an authentic card, a method of applying a magnetic material at a predetermined position in a predetermined discontinuous pattern (Japanese Patent Laid-Open Nos. 58-111130 and 58-58). 150133), a method of forming a predetermined position or a predetermined number of discontinuous portions in the magnetic layer portion, for example, through holes, scratches, etc. (Japanese Patent Laid-Open No. 61-85624), and forming a bar code pattern of a magnetic material. Japanese Patent Application Laid-Open No. 58-101385 discloses a method of coating the card at a predetermined position. Further, in Japanese Patent Laid-Open No. 61-24020, at least two types of regions having different electromagnetic impedances, for example, coating with a suspension of ferromagnetic particles and coating with a suspension of paramagnetic particles or diamagnetic particles are disclosed. (The same publication, page 5, upper left column, lines 6 to 15) discloses a method of adding invariant data unique to a card. [Problems to be Solved by the Invention] However, the methods disclosed in JP-A Nos. 58-111130 and 58-150133 have a small amount of information that can be represented by the discontinuous pattern,
In other words, a large area is required for the amount of information, which is not efficient. Further, as in JP-A-58-101385, the pattern can be known visually or by a magnet viewer or the like, and it is relatively easy to create the same pattern. In the method of Japanese Patent Laid-Open No. 61-85624, it is necessary to maintain the position control accuracy of the through hole and the scratch to a certain level or more, and depending on the positioning accuracy, the magnetic card producing device and the magnetic reading device are expensive. Or become vulnerable to counterfeiting and alteration. In any case, in the case of this method, the forgery / alteration method can be easily inferred from the reproduction waveform by the magnetic head. Further, the method disclosed in Japanese Patent Laid-Open No. 61-24020 requires a dedicated sensor for detecting the magnetic impedance value, resulting in an expensive reading device. When this electromagnetic impedance is a magnetic resistance, it can be detected by a magnetic head, but it is difficult to provide one magnetic head with the reproducing ability of the magnetic stripe portion which is a variable data recording area and the detecting ability of the magnetic resistance. And enabling it could facilitate the decryption of the immutable data area. Therefore, an object of the present invention is to provide a magnetic medium having an extremely strong fraud prevention function and which can be manufactured at low cost, and a confirmation method thereof. [Means for Solving the Problems] In the magnetic medium according to the present invention, at least two types of magnetic materials having different coercive forces are arranged in a predetermined distribution that expresses unique data. A confirmation method of a magnetic medium according to the present invention is a method of confirming the unique data of a magnetic medium in which at least two kinds of magnetic materials having different coercive forces are arranged in a predetermined distribution expressing the unique data. With an initialization step of applying a magnetic field stronger than the maximum coercive force to the magnetic material region composed of the magnetic material in one direction to magnetize the magnetic material region and a strength capable of reversing the magnetization of at least one kind of the magnetic material in the magnetic material region. A magnetization pattern detection step of detecting a magnetization pattern at least once by applying a magnetic field in a direction opposite to that of the initialization step, and a unique property retained in the magnetic material region from the magnetization pattern detected in the magnetization pattern detection step. And a confirmation step for confirming the data. [Operation] Since at least two types of magnetic materials having different coercive forces are arranged in a predetermined distribution that expresses unique data, it is possible to increase information density and enhance confidentiality. Replication itself is also difficult unless the magnetic material used and its placement are known. Therefore, the fraud prevention function is high, and a forged / altered card and an authentic card can be easily identified. Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment in which the present invention is applied to a general magnetic card, and FIG. 2 shows a cross section taken along the line AA of FIG. In FIGS. 1 and 2, the magnetic card 10 has immutable data unique to the card, such as the card number of the cardholder, a membership code and / or a personal identification code, a type code according to the amount of money in the case of a prepaid card, and a card. The management code of the issuing company is magnetically recorded. 12 is plastic,
A base made of paper or the like, 14 is a variable data recording area formed by applying a magnetic material for magnetic recording of variable data to the base 12, and 16 is an invariant data recording area. region
In 14, for example, the balance of the prepaid card and the like are recorded. Reference numeral 18 is a shielding layer for protecting both recording areas 14 and 16. The shielding layer 18 is formed by applying printing ink or sticking a thin tape, for example. In the illustrated embodiment, as clearly shown in FIG. 2, in the invariant data recording area 16, areas 16H and 16L of two kinds of magnetic materials having different coercive forces are unidirectional and represent arbitrary invariant data. Are arranged in this order, and a gap 16G is provided between the regions 16H and 16L to separate them. The gap 16G may be made of the same material as the shielding layer 18, for example. Area 16
Both H and 16L can be formed by applying a magnetic ink in which ferromagnetic fine powder having a single domain structure is dispersed to the base 12.
A magnetic material having a high coercive force is used for the region 16H, and a magnetic material having a lower coercive force is used for the region 16L as compared with the region 16H. Area 16
If the magnetic materials do not mix with each other when forming H and 16L, the gap 16G is not always necessary. Next, with reference to FIG. 3, a method of magnetizing the constant data recording area 16 will be described. First, a strong magnetic field is applied to the entire invariant data recording area 16 in the direction of arrangement of the areas 16H, 16L, 16G for initialization. The direction of the applied magnetic field at the time of this initialization may be any direction. As a result, the magnetic powders in the regions 16H and 16L spontaneously magnetize in the easy axis direction close to the direction of the applied magnetic field, and residual magnetization occurs in the direction of the applied magnetic field as a whole. That is, each area
16H and 16L are magnetized in the same direction as indicated by an arrow mark in FIG. 3 (2), for example. In this state, a reverse magnetic field, which is stronger than the coercive force of the magnetic material in the region 16L but smaller than the coercive force of the magnetic material in the region 16H, is applied. Then, only the magnetization direction of the region 16L is reversed as shown in FIG. If the arrows in FIGS. 3 (2) and (6) point to the right, the binary value is "1", and the arrow to the left is "0".
In the case of FIG. (6), it means that the binary code "10101" could be recorded. Since this binary code depends on the arrangement of the area 16H and the area 16L, the area 16H depends on the recording target signal.
And the arrangement of the area 16L may be changed. Since the present invention utilizes the difference in coercive force, when the constant data recording area 16 is magnetized as shown in FIGS. 3B and 3C, an external magnetic field in the target direction is applied to the entire constant data recording area 16. It is only necessary to apply
Compared with scanning 16L, it is much easier. Of course, the method of magnetizing by scanning the individual regions 16H and 16L with the magnetic head is not excluded. Next, a circuit for reproducing the magnetization state shown in FIGS. 3B and 3C will be briefly described. FIG. 4 shows the basic circuit block. 20 is a magnetic head, 22 is a reproduction amplifier, 24 is a shaping circuit, 26 is a gate signal generation circuit that generates a gate signal for controlling the opening and closing of the AND gate 28, and 30 is a response to a positive pulse from the AND gate 28. The monostable multivibrator (MM) 32 is an arithmetic circuit for digitally arithmetically operating the reproduced binary signal from the MM 30 to determine the authenticity of the card 10.
In the magnetized state of FIG. 3 (2), the reproduction voltage by the magnetic head 20 basically has the waveform shown in FIG. 3 (3), and the shaping circuit 24 shapes this and outputs a rectangular pulse. As shown in FIG. 3 (4), the gate signal generation circuit 26 generates a gate signal in synchronization with the reproduction pulse voltage from the leading edge portion of each magnetic material region 16H, 16L, whereby the MM30
Outputs the pulse train shown in FIG. 3 (5). In the magnetized state of FIG. 3 (6), the reproduction voltage from the reproduction amplifier 22 has the waveform shown in FIG. 3 (7), and the MM 30 outputs the pulse train of FIG. 3 (8). When the magnetization state of the region 16 represents a predetermined pattern, the arithmetic circuit 32 may evaluate and evaluate the pulse train from the MM 30, and the array of the regions 16H and 16L represents fixed fixed data. In this case, after initializing the region 16 to a unidirectionally magnetized state, a strong magnetic field is gradually applied in the opposite direction to gradually reverse the magnetization direction, and the magnetization direction is examined, whereby It suffices to detect the coercive force distribution of the magnetic material. That is, the magnetization direction of the region 16L is reversed by applying a reverse magnetic field of a certain strength, but by comparing the binary signals forming the pulse train from the MM30, the region 16L is
You can know the occupied position of. Specifically, the exclusive OR of the binary signal in FIG. 3 (5) and the binary signal in FIG. It is the region 16L. FIG. 4 shows a basic circuit for reproduction, and various other types of circuits can be used as the reproduction circuit. For example,
Use an RS flip-flop to generate a positive pulse of the playback voltage.
The RS flip-flop may be set and reset by the negative pulse of the reproduction voltage, and the Q output of the RS flip-flop may be appropriately sampled. Also a playback amplifier
The reproduction voltage from 22 may be integrated to form a signal waveform corresponding to the magnetic flux distribution in the region 16, and the recording magnetization state may be determined from the amplitude of the signal waveform. Further, in the circuit of FIG. 4, magnetic recording is reproduced with a single magnetic head 20, but a plurality of magnetic heads are arranged side by side, and the coercive force distribution of the entire region 16 is made in one scan by a reproduction signal from each head. Alternatively, the recording signal may be detected. For example, the plurality of magnetic heads may be sequentially used for initial magnetic field application, reproduction (reading), reverse magnetic field application, reproduction (reading), .... FIG. 5 shows a modified embodiment in which four types of magnetic materials having different coercive forces are used. Coercive force H of each region 40, 41, 42, 43
It is assumed that _C1 , H _C3 , H _C4 , and H _C2 are H _C1 > H _C2 > H _C3 > H _C4 .
First, a strong magnetic field of H _C1 or more is applied to the entire region 16 to magnetize all of the regions 40 to 43 in the same direction (rightward in the illustrated example) as shown in FIG. 5 (2). This state indicates the binary number "1111". Then, a reverse magnetic field smaller than H _{C2 and} higher than H _C4 (to the left in the illustrated example) is applied. Then, only the magnetization of the region 42 of the coercive force H _C4 is inverted, and the state becomes as shown in FIG. 5 (3). This state corresponds to the binary number "1101". FIG. 5 (4) shows the magnetization distribution when a reverse magnetic field smaller than H _C2 and not less than H _C3 is applied from the initial state or the state (3) of FIG. 5 (2). The magnetizations of the regions 41 and 42 are inverted and the binary number "1001" is shown. FIG. 5 (5) shows the magnetization distribution when a reverse magnetic field smaller than H _{C1 and} greater than H _C2 is applied from the initial state or the state (4) of FIG. 5 (2). The magnetizations of the regions 41, 42, 43 are inverted, and the binary number "1000" is shown. Fig. 5 (6) shows that H _{C1 has} changed from the initial state of Fig. 5 (2).
The magnetization distribution when a reverse magnetic field smaller than H _C2 is applied is shown. The magnetization is inverted in all of the regions 40, 41, 42, 43, and the binary number "0000" is shown. In this way, the magnetization directions of the regions 40 to 43 are once aligned (initialized) in one direction, and then, in the opposite direction, a magnetic field having a strength equivalent to the intermediate value of the coercive force of the magnetic material used is applied. The magnitude of the coercive force of the magnetic material in each region can be known by reversing the magnetization direction of a partial region, reproducing the binary signal from the reproducing voltage, and comparing. In other words, the unique data of the magnetic card 10 can be converted into a signal in the distribution of magnetic materials having different coercive forces, or in the order of arrangement. From the viewpoint of forgery, even if the coercive force distribution of the magnetic material in a series of regions can be read, magnetic material of each coercive force must be prepared, and each magnetic material must have the same distribution. Is quite difficult and requires expensive equipment. That is, as the number of types of magnetic materials having different coercive forces increases, the ability to prevent forgery and alteration can be increased. In the illustrated embodiment, since the magnetized state is discretely valued due to the difference in coercive force of the magnetic material, compared with the method of controlling the direction and strength of magnetization by discretely changing the current applied to the recording head. A desired magnetization distribution can be easily formed, and the signal density can be extremely increased in position as compared with the case where a signal having the same magnetization pattern is recorded on a magnetic stripe having a uniform coercive force. Generally, the higher the signal density, the more expensive the decryption device and the recording device, and in that sense, the fraud prevention function is high. As magnetic materials having different coercive force, for example, barium ferrite or strontium ferrite metal having a high coercive force, and cobalt-adhered ferrite or chromium oxide having a smaller coercive force are used. Γ-ferrite or ferrosoferric oxide has a small coercive force. Of course, other magnetic materials can be used. Further, in the illustrated embodiment, the target data may be carried by arranging magnetic materials having different coercive forces. In this case, suitable dummy data may be magnetized as the constant data recording area 16. At the card confirmation stage, the coercive force distribution can be detected by performing initialization and reverse magnetization as described with reference to FIGS. 3 and 5, and the authenticity, type, etc. of the card can be detected from the coercive force distribution. Can be confirmed. In this case, forgery is impossible unless it is known that the coercive force distribution is coded, and even if it is known and the coercive force distribution is decoded, the same coercive force distribution remains unchanged. It is extremely difficult to form the data recording area, and the fraud prevention function is extremely high. When the gap 16G is provided in the region 16, the regions 16H, 16G, 40 to 43 and the gap 16G shown in FIGS. 3 and 6 are arranged as if expressing a bar code or other known code. Is preferred. By doing so, the function of the present invention that utilizes the difference in coercive force can be hidden, and the fraud prevention function can be further enhanced in combination with the use of the known code. In the present specification, a magnetic card means a card using a magnetic material, and is not necessarily limited to a card in which signals are magnetically recorded. For example, it may be a card that digitizes and records signals. Further, it may be flexible such as paper, and for example, a flexible sheet material is coated with magnetic materials having different coercive forces and attached to another article such as a so-called bar code label. It does not preclude its application to display the attributes of articles. [Effects of the Invention] As can be easily understood from the above description, according to the present invention, it is extremely difficult or impossible to know the recording structure of the unique data from the observation result or the reproduced waveform by the magnet viewer, Highly preventive function against forgery and alteration. Forgery,
It is possible to effectively prevent fraud such as alteration and illegal use. Since the device for authenticity verification may be inexpensive, the whole system can be constructed inexpensively.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a magnetic card according to an embodiment of the present invention, and FIG.
FIG. 4 is a sectional view taken along the line AA in FIG. 1, FIG. 3 is an explanatory view of magnetization and reproduction signals in the invariant data recording area according to the present invention, and FIG.
FIG. 5 is an example of a reproducing circuit, and FIG. 5 is an explanatory diagram of a modified example using magnetic materials having four types of coercive force. 10 ... Magnetic card, 12 ... Base, 14 ... Variable data recording area, 16 ... Invariant data recording area, 18 ... Shielding layer, 20
...... Magnetic head, 22 ...... Reproduction amplifier, 24 …… Shaping circuit,
26 …… Gate signal generation circuit, 28 …… And gate, 30
…… Monostable multivibrator, 32 …… Arithmetic circuit

Claims (1)

(57) [Claims] A magnetic medium characterized in that at least two kinds of magnetic materials having different coercive forces are arranged in a predetermined distribution that expresses unique data. 2. The magnetic medium according to claim (1), wherein dummy data is magnetically recorded on the magnetic material. 3. A method for confirming the specific data of a magnetic medium in which at least two types of magnetic materials having different coercive forces are arranged in a predetermined distribution that expresses the specific data, and the maximum is set in a magnetic material region composed of the at least two types of magnetic materials. The initialization step of applying a magnetic field stronger than the coercive force to magnetize the magnetic material in one direction and the strength that can reverse the magnetization of at least one kind of the magnetic material in the magnetic material region causes a magnetic field in the direction opposite to that of the initialization step. A magnetization pattern detection step of applying and detecting the magnetization pattern at least once, and a confirmation step of confirming the unique data held in the magnetic material region from the magnetization pattern detected in the magnetization pattern detection step. How to check the characteristic magnetic media.