JPH09128508A - Magnetic recording medium and magnetic recording and reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which is hardly altered and forged and further, does not generates unwanted objects by performing recording while irreversibly attenuating the saturated magnetization of magnetic particles by heating. SOLUTION: In ferromagnetic materials, there is a material which is utilized at ordinary temperature as stable magnetic recording material and loses magnetism by irreversibly changing crystal structure by heating. While utilizing such a phenomenon, the ferromagnetic material (such as magnetite, for example,) with the irreversible attenuation transition of saturated magnetization from magnetic to nonmagnetic because of heating are made into fine particles and this is made into coating together with a binder so that a magnetic recording layer can be formed. Namely, a magnetic coating film 2 is formed on a supporting substrate 1 of polyesther, etc. Magnetic particles 2A are heated by a heating means 3 and transited into nonmagnetic particles 2B partially. The non-heated magnetic particles 2A are made into magnetic particles 2C by a DC magnetic field flowing to a bias coil 4A at a reproducing head 4 but the nonmagnetic particles 2B are not magnetized. At that boundary, free magnetic pole is generated and this is detected by a reproducing coil 4B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium and a magnetic recording / reproducing method using the same, and more particularly to a magnetic card capable of preventing falsification and forgery and a recording / reproducing method thereof.

[0002]

2. Description of the Related Art In recent years, many magnetic cards have been used as cash vouchers. However, the ease of recording / reproducing, which is a feature of magnetic cards, also means the ease of copying, and it is necessary to take various measures to prevent forgery.

A magnetic card is roughly classified into (A) a user, and a semi-permanently repeatedly used cash card, credit card or ID card, and (B) a user, which does not specify a user, and has a certain limit. It is classified into a kind such as a prepaid card, a point card, or a commuter pass, which is used only for the amount of money or the period. When using a card of (A) type, when using, some authentication information for identifying an individual such as a personal identification number, a signature, a unique code number or a face photograph is used for verification, whereas a card of (B) type is mainly used. Since it is used as a data medium for automatic terminal operation in an unattended environment, it is required to add some automatically detectable security function to the card itself to prevent misuse such as forgery and tampering.

Therefore, the structure of the (B) type card is as follows.
In addition to retaining the usual (1) variable magnetic recording area for recording and reproducing various functional information and (2) pictorial character printing area that characterize the card as essential requirements, reuse of the used card as described above is also possible. In order to prevent this, there is an irreversible structural change according to the degree of use, and a sensor is provided to automatically detect and check (3) the use degree determination area is provided to prevent abuse of repeated use.

(3) A method of causing an irreversible structural change in a card before and after use and detecting it by a sensor to prevent reuse of a used card is, for example, an optical method. Are disclosed in JP-A-56-90386,
As disclosed in JP-A-62-35992, a method of perforating a predetermined portion of a card according to the degree of use and detecting passing light with an optical sensor. As a magnetic method, Japanese Patent Laid-Open No.
-79123 and JP-A-61-85624, a method of perforating a magnetic layer portion of a card and detecting a leakage magnetic flux generated at an edge portion with a magnetic head, JP-A-6-86242.
No. 11950, a method of checking the Curie temperature of a magnetic material in combination with heat-sensitive color development by a thermal head, or a ferromagnetic vapor deposition film and a non-magnetic vapor deposition film as in JP-A-57-18027. A method of irreversibly demagnetizing the laminated magnetic film by heating the same is proposed.

Looking at the technique for forming the recording of the usage frequency with irreversible structural change of the conventional card, the above-mentioned method of optically reading the hole can easily close the hole and make it unreadable. In addition, there is a problem in that the spacing between the holes is generally rough, and that use during this time is completely defensive because no evidence of structural change is generated, and unnecessary scraps are generated. Another way is
Abuse of blockage can be avoided compared to the optical method, but fraud of displacing the unused part of the card by shifting the position is also considered, and the problem of rough management intervals and occurrence of scraps remains the same. The method of (1) has the advantage of high recording density and no generation of waste, but the combination of the three elements of light, magnetism and heating complicates the apparatus and the Curie temperature of the magnetic material is irreversible. The signal can be re-recorded instead of being permanently changed. The other method has the advantages that the recording density is generally high, no unnecessary substances are generated, and an irreversible structural change is involved, but for a few minutes, it is necessary to form a laminated structure by vapor deposition and mass production is required. However, it has not been found yet that the method is sufficiently satisfactory, such as the possibility that the property is concerned and that it is probably difficult in practical use. Also, the method of JP-A-59-3 is used.
The same is true of Japanese Patent No. 8926.

[0007]

DISCLOSURE OF THE INVENTION The problem to be solved by the present invention is to provide a magnetic recording medium suitable for a magnetic card and a recording / reproducing method thereof, which is difficult to be tampered with or forged, and which does not generate waste. In particular, in a prepaid card or a point card that is used for a limited amount of money or a limited period, it is possible to perform more precise frequency determination than in the past.

[0008]

[Means for Solving the Problems] Such problems can be achieved by the following constitutions (1) to (4). (1) A magnetic recording medium for recording by irreversibly attenuating the saturation magnetization of magnetic particles by heating. (2) The magnetic recording medium according to (1), which has a usage recording region containing the magnetic particles. (3) The magnetic recording medium according to (1) or (2) above, which has an ID code recording area containing the magnetic particles. (4) A magnetic recording / reproducing method having a procedure of irreversibly attenuating the saturation magnetization of the magnetic particles by heating the magnetic recording medium according to any one of (1) to (3).

[0009]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described.

Some of the ferromagnetic materials used as magnetic recording materials that are stable at room temperature include those that lose their magnetism by irreversibly changing their crystal structure by heating. Unlike the Curie temperature, which temporarily changes from ferromagnetism to paramagnetism, they do not recover their magnetism even if the temperature is restored. Generally, these transition temperatures are relatively high, but if the material is made into fine particles, the thermodynamic increase in surface energy makes it possible to cause uniform transitions at low temperatures. It is generally known that a ferromagnetic material changes from a multi-domain structure to a single-domain structure due to atomization, and further changes to superparamagnetism. In this case, the coercive force of the magnetic particles is
From the multi-domain to the single-domain, it reaches its maximum, and in the superparamagnetic stage, the degree of thermal fluctuation of the particle becomes dominant and finally becomes zero, whereas the saturation magnetization of the particle is from the multi-domain to the single domain. However, it does not change so much and reaches the state of superparamagnetism, which is attenuated by the thermal agitation effect of particles like coercive force, but retains a much larger saturation magnetization amount than ordinary paramagnetic (paramagnetic) magnetic materials. To do.

Utilizing the above phenomenon, magnetism is generated by heating.
A ferromagnetic material having a non-magnetic to saturation magnetization and an irreversible decay transition is made into fine particles, and this is made into a coating material together with a binder to form a magnetic recording layer, and the recording is performed by a heating means such as a thermal head or laser light. The layer is partially heated to locally demagnetize the magnetic particles forming the recording layer. Since the non-heated portion remains magnetic, this results in the formation of a kind of magnetic bar code-like recording of magnetic / non-magnetic. This recording is an irreversible structural change and cannot be returned to the original state, and becomes a magnetic recording specialized for additional recording.

The magnetic recording / reproducing method utilizing the irreversible decay change of the saturation magnetization due to the heating can be summarized into the following three methods. That is, (a) first, the magnetic recording layer is formed as a uniform coating layer, and the coating layer is locally heated,
Method for forming barcode-like non-magnetic pattern, (b)
The second is a method in which the magnetic recording layer is formed in advance as a magnetic bar code-like pattern and the bar code is selectively heated to demagnetize. Since both of these two methods are magnetic bar code-like signal recording, output detection is
It can be reproduced by a method similar to the method performed by a normal magnetic barcode. That is, when the magnetic recording material forming the coating film has a sufficient coercive force and free magnetic flux leakage due to residual magnetization can be expected to occur at the edge of the magnetic bar, after magnetizing with a permanent magnet, etc., with a reproducing head, Even when the recording material is in a superparamagnetic state and has a small coercive force or zero, reproduction can be performed by detecting a leakage magnetic flux of saturation magnetization generated at the edge portion while applying a bias current to the reproducing head.
(C) The third method is slightly different from the above methods (a) and (b), in which a normal digital signal is recorded in advance on a magnetic recording layer formed as a uniform coating layer to erase the magnetic field. Not by heating and demagnetizing, but by counting the residual signal, or by partially heating and demagnetizing the non-recording magnetic recording layer, and counting the unheated magnetic portion intervals by normal digital signal recording and reproduction, It is a method that uses the numerical value as a recording signal, so to speak, in combination with a normal recording / reproducing method. However, in this case, since the usual magnetic recording method is used, it is necessary that the recording material used has a certain coercive force.

Since all of these three magnetic recording / reproducing methods perform irreversible recording, they can be used as a recording method of the usage of magnetic cards. That is, in the application example of the magnetic recording / reproducing method of the above (a), the non-magnetic pattern is sequentially heated and additionally recorded on the uniformly formed magnetic recording layer according to the degree of use or the point of use. In the usage example of the magnetic recording / reproducing method of the above (b), a predetermined magnetic bar code is formed in advance, and the bar code for the degree of use is sequentially heated and demagnetized according to the degree of use. Further, in the usage example of the magnetic recording / reproducing method of the above (c), a normal digital signal previously recorded in the uniformly formed magnetic recording layer is sequentially heated to demagnetize and erased in accordance with the degree of use. Or a method of measuring and counting the remaining unheated magnetic region after demagnetization with a digital signal of a predetermined wavelength.

The irreversible use recording layer according to the present invention is, for example, 5 mm / 1 in the conventional perforation method as a method for forming an area of 5 cm, but the total number of perforations is about 10/5 cm. On the other hand, although it depends on the method, it is possible to record at a density of at least 1 mm / 1, and it is possible to expect to discriminate the frequency about 5 times or more that of the punching method. Also in this method,
Since the recording format can be modified in various ways, it is possible to change the form of the usage frequency display for each type of card ticket, and it is extremely effective as a countermeasure against tampering from a low-value ticket to a high-value ticket, for example. Thus, as compared with the conventional perforation method, it is possible to more closely follow the usage frequency, to prevent the generation of waste such as scraps, and to provide a usage frequency recording layer that is more difficult to forge and falsify.

This recording method can be used not only as a usage recording layer, but also as a method of giving a unique ID code for identifying a card, which is another method for preventing forgery of a magnetic card. That is, in the use as a usage recording layer, recording was a simple and continuous non-magnetic pattern formation, whereas in the case of ID code recording, the recording / reproducing method of (a) or (b) above was used. Is formed by demagnetizing the selective position of the recording layer and forming it as a predetermined pattern signal code composed of magnetism / nonmagnetization, or by the method of (c), the interval of the nonmagnetic pattern formed intermittently is digitalized. The signal is counted, and this count value is used to record as a unique code or encryption key code that differs for each card. These methods are non-rewritable write-once type recording and have an advantage that they can be easily formed at the same time as the card issuance at the store.

The temperature at which the nonreciprocal magnetic recording layer according to the present invention can be heated is limited by the heat resistance of the supporting substrate. If the supporting substrate has heat resistance, it can be heated at a high temperature, but if a polyester or vinyl chloride plastic film, which is often used for magnetic cards, is used as the substrate, it may be deformed and the temperature is too high. Can't be heated. If a generally known thermal head used in a thermal recording system of a magnetic card is used as the heating means, the maximum surface temperature of the thermal head is 40.
Since it is around 0 ° C, it is 400 ° C or lower, preferably 350
The material and particle size of the magnetic particles are designed so that the particles are sufficiently transformed at a temperature of about 150 ° C. Here, the lower limit temperature is a temperature that is considered to be necessary to ensure the storage stability of the magnetic particles. Further, what is required of the magnetic particles contained in the magnetic recording layer is that the particles are preferably uniformly transferred by heating and lose the magnetization. However, since the magnetic particles are produced by an industrial mass production method for some minutes, a certain spread of the particle size distribution cannot be avoided. Actually, it may be difficult to realize the ideal state of simultaneous transition, but in practice, if it is attenuated to about ⅕ of the original magnetization amount by the heating means, a low-pass filter that cuts the low output part A signal change can be detected by means such as an electric circuit.

In order to forge or tamper with a card having a usage recording layer or an ID code layer using nonreciprocal magnetic recording according to the present invention, a full-scale manufacturing apparatus and members are required. Furthermore, if a concealment method is devised, and used tickets are collected and used members are leaked out, it is possible to construct a system in which almost no card can be abused.

The magnetic recording material used for the magnetic particles of the present invention may be any material that loses magnetism due to irreversible structural change.

Specific examples include magnetite.
Magnetite Fe ₃ O ₄ is also written as FeO / Fe ₂ O ₃ and is a ferromagnetic (= ferrimagnetic) material having an inverse spinel cubic structure. When heated to about 400 ° C, the rhombohedral α
It is transformed to —Fe ₂ O ₃ and becomes antiferromagnetic (= nonmagnetic). In preparation of the magnetite fine particles to be used as the medium of the present invention and the same paint, care should be taken because the particles are small and chemically activated, but the method well known as a method for producing magnetic fluid can be applied as it is. That is, oleic acid ions or the like are adsorbed on magnetite produced by a wet milling method in which a ball mill is used for a long time in an organic solvent (for example, US Pat. No. 3,215,572) or a coprecipitation method to form particles of particles. Co-precipitation in which particles are dispersed in the vehicle after washing, filtering and drying-
Adsorption in aqueous solution-organic phase dispersion method or its improved method (for example, Proceedings of the 1966 meeting of the Chemical Society of Japan, JP-A-51-
No. 44579, No. 52-42482, No. 56.
No. 118496) can be used.

In addition to this, as a magnetic recording material, γ-Fe ₂ O ₃ similarly having a spinel structure should be transformed to non-magnetic by being transformed into rhombohedral α-Fe ₂ O ₃ by heating at about 400 ° C. Is known and can be used. In addition to this, for example, the ferromagnetic metal may be made into fine particles and activated, and demagnetized by a chemical reaction such as oxidation by heating.

The binder system for forming the coating film is a polyvinyl chloride-polyvinyl acetate-polyvinyl alcohol copolymer resin, polyester resin, epoxy resin, acrylic resin, nitrocellulose resin, phenoxy resin, urethane resin, etc. The binder system for paints and inks that form the coating layer can be used as is. However, as described above, a heat-resistant curable binder system is desirable because heat is applied from the top of the coating layer by heating means.In this case, various curing agents having isocyanate groups or amine groups are added as curing agents. It is formed by means of UV curing, electron beam curing, or the like. Solvents are methyl ethyl ketone, methyl isobutyl ketone, toluene,
Cyclohexanone, THF, a mixed solvent, and other solvents appropriately selected according to the method of forming the coating film are used, and if necessary, surfactants, fillers, and additives are added in appropriate amounts.

The irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention will be described below. 1A,
(B) and (C) are schematic diagrams for explaining an irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention. 1 is a support substrate, 2 is a magnetic coating film, 2A is magnetic particles, 2B is non-magnetized particles, 2C is magnetized particles, 3 is heating means, 4 is a reproducing head,
4A represents a bias coil and 4B represents a reproducing coil. The medium runs under the heating means 3 and the reproducing head 4 in the direction of the arrow from left to right.

The supporting substrate 1 may be any substrate used for ordinary magnetic recording media such as polyester, vinyl chloride, polycarbonate, polyimide film, synthetic paper and paper.

The magnetic coating film 2 is coated with various kinds of coating methods such as gravure coating, nozzle coating, screen printing, offset printing, transfer printing and ink jet printing using the paint or ink prepared by the method described above. Form. The thickness t of the coating film is not so thick that the heating from above can be sufficiently spread in a short time. In the illustrated example, the non-magnetic patterns are formed in the same shape, but since the bar length a can be made thicker than the heating portion length of the heating means by feeding, any combination of the bar length a and the spacing c can be used. A code system can be designed and a usage recording code system can be constructed.

The magnetic particles 2A are heated by the heating means 3 and partially transferred to the non-magnetized particles 2B. Upon reaching the reproducing head 4, the unheated magnetic particles 2A are magnetized by the DC magnetic field flowing in the bias coil 4A to become magnetized particles 2C, but the adjacent non-magnetized particles 2B are not magnetized. Therefore, a free magnetic pole is generated at the boundary between the magnetized particle 2C and the non-magnetized particle 2B, and this is detected by the reproducing coil 4B.

The heating means 3 may be any means such as a thermal head or a laser beam as long as it can locally heat. The thermal head, which is the most common heating means, is usually for dot printing and recording, and the head surface is divided into several cells. In order to perform bar code recording, a thermal head having a flat head surface shape capable of heating uniformly is preferable.

As the reproducing head 4, a normal ring head can be used as it is. However, the head gap is designed in consideration of the recording density and boundary resolution so that the leakage magnetic flux can be efficiently caught. Of course, a magnetoresistive element may be used for reproduction.

FIG. 1B is a view of the formed barcode-like pattern as seen from above. The width b of the cord corresponds to the heating portion width of the heating means.

FIG. 1C shows an example of the output signal detected by the reproducing head. The output signal is generated at the boundary between the magnetic part and the non-magnetic part of the pattern.

2 to 3 show the outline of a first embodiment in which the irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention is used for recording the usage of a magnetic card. The first embodiment corresponds to the magnetic recording / reproducing method (a). 1
Is a support substrate, 2a is a usage recording layer, 2Aa is an unheated magnetic part, 2Ba is a heated non-magnetic part, 3a is a thermal head, 4a.
Represents a reproducing head, 4A represents a bias coil, and 4B represents a reproducing coil.

FIG. 2 is a diagram showing the state of the first usage of the magnetic card usage recording layer in the first embodiment. The usage recording layer is in this case formed as a uniform coating,
The coating film formation region L is determined in consideration of the maximum effective frequency of the card, the bar pattern length of unit frequency, and the pitch.

FIG. 3 is a schematic diagram of formation of a usage frequency pattern and detection of output when the card is used. In accordance with the use of the card, the recording layer is locally heated by the thermal head 3a with the start reference edge as a base point, and bar-shaped non-magnetic portions 2Ba are sequentially formed at a preset pitch and length. In the reproducing head 4, a current is passed through the bias coil 4A to detect the leakage magnetic flux generated from the free magnetic pole generated at the boundary between the unheated magnetic portion and the heated non-magnetic portion, and count the number of formed bar patterns. This method is exclusively for write-once recording, so it is suitable for application to cumulative usage-type point cards.However, if the maximum effective usage is predetermined as described above, the remaining usage count can be easily calculated. Of course, it can also be used for prepaid cards. Further, in this method, it is possible to form different usage recording layers for each card bill type by changing the bar length and pitch.

4 to 5 show the outline of the second embodiment in which the irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention is used for recording the usage of a magnetic card. The second embodiment corresponds to the magnetic recording / reproducing method described in (b) above. 1
Is a support substrate, 2b is a usage recording pattern, 2Ab is an unheated magnetic pattern, 2Bb is a heated non-magnetic pattern, 3a is a thermal head, 4 is a reproducing head, 4A is a bias coil, and 4B is a reproducing coil.

FIG. 4 is a diagram showing a state at the time of the first issuance of the magnetic card usage recording layer in the second embodiment. The usage recording patterns 2b are formed with a predetermined length and pitch, each of which has a unit frequency corresponding to the value display of the magnetic card, and a necessary number of patterns corresponding to the maximum effective frequency are formed in advance. To be done.

FIG. 5 is a schematic diagram of demagnetization of a pattern and detection of output when the card is used. The unheated magnetic pattern 2Ab is heated by the thermal head 3a according to the degree of use, and changes into a nonmagnetic heated nonmagnetic pattern (used pattern) 2Bb. The remaining number of cards is detected and counted by the reproducing coil 4B while the unheated magnetic pattern 2Ab is being supplied to the bias coil 4A by the reproducing head 4. Also in this case, it is possible to form different usage recording layers for each bill by changing the length and the interval of the pattern. Since this method is exclusively an erasing type recording method, it is mainly suitable for a subtraction residual level recording type prepaid card.

FIGS. 6 to 7 show an outline of a third embodiment in which the irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention is used for recording the usage of a magnetic card. The third embodiment corresponds to the magnetic recording / reproducing method of (c) above. 1
Is a support substrate, 2a is a usage recording layer, 2Aa is an unheated magnetic part, 2Ba is a heated non-magnetic part, 3a is a thermal head, 4a.
Represents a reproducing head, and 4B represents a reproducing coil.

FIG. 6 is a diagram showing the state at the time of the first issuance of the magnetic card usage recording layer in the third embodiment. The degree-of-use recording layer 2 is preliminarily recorded on the coating film uniformly formed by the same method as described above, in the form of the normal number of digital signals of a constant wavelength in the maximum effective frequency.

FIG. 7 is a schematic view of the usage indication and output detection status when the card is used. Depending on the usage of the card, a constant area of the digital signal is heated and erased by the thermal head 3a to form the heated non-magnetic portion 2Ba. The remaining frequency is measured by counting the digital signal left by the reproducing head 4. Alternatively, when the card is issued, it is set as a signalless coating film area as in the first embodiment, and the residual number is
A method of recording / reproducing a digital signal having a predetermined wavelength and measuring and counting the interval of the unheated magnetic portion regions is also possible. However, in this case, it is necessary to add a recording head to the system. In the case of this system, the discrimination classification for each bill type can be realized by changing the digital signal wavelength, for example.

In the above, the case where the magnetic recording medium of the present invention is applied to the recording of the usage of the magnetic card has been described. The irreversible recording in the usage example of this usage recording is characterized in that a pattern is sequentially formed continuously from the start.

When the irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention is used as fixed code recording such as an ID code, for example, the magnetic recording / reproducing method described in (a) or (b) above is used. Non-magnetic part is selectively formed,
It is recorded as a magnetic / non-magnetic binary signal or an ordinary bar code-like signal in which the bar length and pitch are combined.
In the method of (C), for example, a predetermined non-magnetic portion is intermittently formed in the magnetic recording layer, and the length of the magnetic portion sandwiched therebetween is measured by recording and reproducing a normal digital signal, and the numerical value is measured. Is used as a code display. The principle of recording and reproducing is exactly the same as the method described above. This irreversible recording method differs from, for example, bar code formation in a printing method using a printing plate,
There is an advantage that a different code for each card can be issued at the same time at the store.

FIG. 8 is a structural example of the magnetic recording medium of the present invention. 10 is a magnetic card, 10A is a support base, 10B is a variable magnetic recording area, 10C is a usage recording area, and 10D is an ID code recording area. Variable magnetic recording area 1
Reference numeral 0B is a reversible recording layer according to a normal method, and various kinds of data such as the remaining amount, the remaining period, and the remaining number of times which are rewritten for each use are recorded and reproduced. The usage recording area 10C is a recording layer based on an irreversible magnetic recording method, and is formed in a different pattern for each bill type. ID code recording area 1
Reference numeral 0D is a recording layer based on a nonreciprocal magnetic recording system, and it is assumed that various fixed signals including a bill type code that are not rewritten are recorded.

It is considered that a typical prepaid card as a magnetic card is used through the following three procedures. That is, (I) card carry-in / card authenticity determination / card remaining count verification, (II) usage count input / calculation / remaining count write, (III) card remaining count verification / card discharge
It is a step. In the first step (I), at the same time as the carry-in, the authenticity of the card is first judged by referring to the unique code and the like recorded in the ID code recording area, and at the same time, the ticket type code is read, for example, the ticket type code is used as an encryption key. By using the predetermined algorithm, the remaining balance of the card corresponding to the remaining balance signal in the usage recording area is calculated. This value and the balance data recorded in the variable magnetic recording area are collated to verify the correctness of the card. In the second step (II), when the usage amount is input by means such as a numeric keypad provided separately, the usage amount is additionally written in the usage recording area,
At the same time, the balance data in the variable magnetic recording area is rewritten.
In the final third step (III), the remaining amount is calculated from the remaining amount signal of the newly added usage recording area and the bill type code, and the remaining amount of the newly rewritten variable magnetic recording area is collated and a series of correct values is calculated. Verify that the operation is complete. Here, since the recording in the ID code recording area and the recording in the usage recording area are formed by the non-rewritable irreversible magnetic recording method, the data cannot be falsified once it has been recorded, so that the data in the variable magnetic recording area is falsified. Immediately, however, a mismatch in verification occurs, and fraud is discovered. Moreover, since the usage recording area of the used card is irreversibly demagnetized, it cannot be tampered with again. Further, even if a low-priced ticket is to be tampered with, for example, the recording format of the ticket type code and the usage record area is completely impossible because it is formed by irreversible recording that is different for each ticket type.

The variable magnetic recording area 10B, the usage recording area 10C, and the ID code recording area 10D may be located at any position on the medium or may be on the front and back sides, and may have a protective layer or a concealing layer or an upper portion. It is self-evident that even if a dummy layer is formed, it is within the scope of the present invention.

[0044]

Embodiments of the present invention will be described below.

100 parts by weight of magnetite having an average particle size of about 100 A, prepared by a wet milling method using a ball mill, 30 parts by weight of modified polyester resin, and an isocyanate curing agent 3
A coating containing, by weight, 15 parts by weight of oleic acid and 170 parts by weight of an organic solvent as main components was prepared by a sand mill, and an applicator was used to form a uniform coating film having a thickness of about 3 μm on a polyester film substrate having a thickness of 250 μm. Was formed.
Next, this coating film was cured in a drying oven at about 100 ° C. to form a magnetic recording layer, and then punched into a JIS II type card size to obtain a magnetic card. Next, after partially heating the magnetic recording layer with a thermal head, reading was performed while applying a bias current to the reproducing head, and it was confirmed that output was generated in the boundary region between the heated portion and the non-heated portion.

[0046]

INDUSTRIAL APPLICABILITY The magnetic recording medium of the present invention, when used in the above-described recording / reproducing method, is hard to be tampered with or forged, and does not need to be perforated in the medium, so that no waste material is generated. Further, when applied to a prepaid card or a point card that is used for a limited amount of money or for a limited period, it is possible to perform more precise frequency determination than in the past. Further, since the magnetic particles, the heating means and the reproducing head used in the present invention can be relatively easily procured by applying the conventional technology,
The investment for industrializing the present invention is small.

[Brief description of the drawings]

FIG. 1 (A) is a schematic diagram for explaining a non-reversible magnetic recording / reproducing method using a magnetic recording medium of the present invention, and FIG. 1 (B) is a diagram of a formed barcode-like pattern as seen from above. Yes, (C) is an example of the output signal detected by the reproducing head.

FIG. 2 is an outline of a first embodiment in which the irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention is used for recording the usage of a magnetic card, and the first issue of the magnetic card usage recording area. It is a figure showing the state of time.

FIG. 3 is an outline of a first embodiment in which the irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention is used for recording the usage of a magnetic card, and a usage frequency pattern is formed when the card is used. FIG. 3 is a schematic diagram of detection of output and output.

FIG. 4 is an outline of a second embodiment in which the irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention is used for recording the usage of a magnetic card, and the first issue of the magnetic card usage recording area. It is a figure showing the state of time.

FIG. 5 is an outline of a second embodiment in which the irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention is used for recording the usage of a magnetic card, and the pattern is made non-magnetic when the card is used. FIG. 3 is a schematic diagram of detection of output and output.

FIG. 6 is an outline of a third embodiment in which the irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention is used for recording the usage of a magnetic card, and the first issue of the magnetic card usage recording area. It is a figure showing the state of time.

FIG. 7 is an outline of a third embodiment in which the irreversible magnetic recording / reproducing method using the magnetic recording medium of the present invention is used for recording the usage of a magnetic card, and the usage display and output when the card is used. It is a schematic diagram of the detection of.

FIG. 8 is a structural example of a magnetic recording medium of the present invention (magnetic card).
FIG.

[Description of Reference Signs] 1 support base 2 magnetic coating 2a usage recording layer 2b usage recording pattern 2A magnetic particles 2Aa unheated magnetic part 2Ab unheated magnetic pattern 2B non-magnetized particle 2Ba heating non-magnetic part 2Bb heating non-magnetic pattern 2C Magnetized particles 3 Heating means 3a Thermal head 4 Reproducing head 4A Bias coil 4B Reproducing coil 10 Magnetic card 10A Support base 10B Variable magnetic recording area 10C Usage recording area 10D ID code recording area

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G11B 11/14 9075-5D G11B 11/14

Claims (4)

[Claims] 1. A magnetic recording medium for recording by irreversibly attenuating the saturation magnetization of magnetic particles by heating. 2. The magnetic recording medium according to claim 1, further comprising a usage recording area containing the magnetic particles. 3. The magnetic recording medium according to claim 1, which has an ID code recording area containing the magnetic particles. 4. A magnetic recording / reproducing method having a procedure of irreversibly attenuating the saturation magnetization of the magnetic particles by heating the magnetic recording medium according to claim 1. Description: