JPH10187918A - Magnetic recording medium and magnetic recording and reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium and a magnetic recording/ reproducing method which can assure the high safety against the wrong use of a magnetic card such as its forgery, alteration, etc. SOLUTION: A magnetic recording medium 1 has plural magnetic bars A which are made of a magnetic material whose saturated magnetization is irreversibly increased by heating and arrayed in a bar code shape at least at a part of a magnetic recording layer. When the magnetic recording/reproducing operations are applied to the medium 1, the bars A are selectively heated. Then a magnetic sensor detects the difference of magnetization between the heated and non-heated bars A for reproduction of the recorded information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing method used for a magnetic card or the like which requires high security against unauthorized use such as forgery or alteration.

[0002]

2. Description of the Related Art In recent years, magnetic cards have become very popular and are used in various fields. In particular, applications to cards (prepaid cards) in which amount information and the like are recorded as magnetic information and the amount is subtracted and rewritten each time they are used, are expanding.

[0003] In this application, if the magnetic card is easily altered by falsification of the recorded information or the card itself is easily forged, the security of the system is significantly reduced. For this reason, a magnetic card having a function of protecting information from tampering has been demanded, and various magnetic cards have been proposed and put into practical use in response thereto.

As one of these conventional methods, fixed data for authenticity determination which cannot be rewritten is written on a part of a magnetic card.
Provided at a different position from the magnetic recording unit that records variable data, the fixed data is also recorded in the magnetic recording unit, and when used, fixed data for genuineness determination that cannot be rewritten and variable data are used. There is a method in which the reproduction is verified and the authenticity of the card is determined. Specifically, for example, Japanese Patent Application Laid-Open No. 62-14558
No. 5 and Japanese Patent Publication No. 3-30909, a soft magnetic material having a coercive force of 10 Oe or less or a coercive force lower than that of a magnetic recording layer is provided on a magnetic recording layer having a magnetic recording / reproducing function. A method is proposed in which a magnetic barcode is formed by printing or the like, and a magnetic card provided with a colored layer for concealing the magnetic barcode from above is read while applying an external magnetic field to the magnetic barcode. Have been.

As another conventional method, for example,
JP-A-63-133321 or JP-A-6-133321
As disclosed in JP-A-3-308724, a combination of magnetic barcodes containing magnetic materials having different coercive forces or, for example, as disclosed in JP-A-63-223892, A combination of magnetic barcodes containing different magnetic materials, for example,
As disclosed in JP-A-147191, various types have been proposed, such as a combination of magnetic barcodes containing magnetic materials having different Curie temperatures.

[0006]

However, the above-mentioned Japanese Patent Laid-Open No. 62-145585 and Japanese Patent Publication No. 3-30.
In the conventional method disclosed in Japanese Patent Application Laid-Open No. 909, the presence of a barcode can be confirmed by direct visual observation.
Actually, for example, as disclosed in Japanese Utility Model Application Laid-Open No. 54-118800, by combining a magnetic barcode containing a magnetic material and a dummy barcode not containing the magnetic material, the fixed data can be visually checked. The reality is that it makes decryption difficult and increases the security of the magnetic card.

Further, Japanese Patent Application Laid-Open Nos. 63-133321, 63-308724, and
No. 223892 and Japanese Utility Model Application Laid-Open No. 62-147191.
The conventional method disclosed in Japanese Patent Application Laid-Open Publication No. H11-157, requires a special material such as a plurality of different types of magnetic ink as a material for forming a barcode as fixed information, and also uses a magnetic recording medium. In order to form on top, a separate process from the process of forming the magnetic recording layer, such as screen printing or offset printing, is required, so the manufacturing process is complicated, so it is not suitable for mass production, and the cost is high. turn into.

Further, since these fixed information is formed by printing, there are a plurality of magnetic cards having magnetic bar codes of the same pattern, so that the security is limited. In addition, since the fixed information remains after the use of the magnetic card, it is possible to reuse the information by restoring the information of the magnetic recording unit for recording the variable data to the initial state, thereby enabling unauthorized use. It gives the character.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to effectively prevent a recording medium such as a magnetic card from being falsified by falsification and the like. The purpose is to provide a method for performing reproduction.

[0010]

A magnetic recording medium according to a first aspect of the present invention has a magnetic recording layer on a substrate, and at least a part of the magnetic recording layer has an irreversible saturation magnetization upon heating. And a plurality of magnetic bars formed of a magnetic material and arranged in a barcode shape.

According to one embodiment of the present invention, the magnetic recording layer comprises a fixed information magnetic recording layer and a variable information magnetic recording layer, and the plurality of magnetic bars are provided on the fixed information magnetic recording layer. Has been.

According to a specific embodiment of the present invention, the magnetic bars are arranged in advance in a pattern having an equal width and an equal interval.

According to another particular embodiment of the invention,
The magnetic bars are arranged in a pre-coded pattern.

A magnetic recording method according to a second aspect of the present invention is a magnetic recording medium having a magnetic recording layer on a substrate, wherein at least a part of the magnetic recording layer has a irreversible saturation magnetization upon heating. In a magnetic recording medium including a plurality of magnetic bars formed of a magnetic material and increasing in a bar code shape, by selectively heating some of the plurality of magnetic bars, Records fixed information specific to the medium.

A magnetic recording method according to a third aspect of the present invention is a magnetic recording medium having a magnetic recording layer on a substrate, wherein at least a part of the magnetic recording layer has an irreversible saturation magnetization upon heating. In a magnetic recording medium including a plurality of magnetic bars formed of a magnetic material and increasing in a bar code shape, by selectively heating some of the plurality of magnetic bars, Record media usage.

According to one embodiment of the present invention, the heating of the magnetic bar is to heat the entire magnetic bar.

According to another embodiment of the present invention, heating the magnetic bar heats only a part of the magnetic bar.

A magnetic recording / reproducing method according to a third aspect of the present invention is a magnetic recording medium having a magnetic recording layer on a substrate, wherein at least a part of the magnetic recording layer has a irreversible saturation magnetization upon heating. A plurality of magnetic bars formed of a magnetic material that increases in number and arranged in a barcode shape,
In a magnetic recording medium on which information is recorded by selectively heating the plurality of magnetic bars, the heated magnetic bars and the unheated magnetic bars are magnetized by applying a DC magnetic field to the plurality of magnetic bars. The recorded information is reproduced by detecting a difference in magnetization between the bar and the magnetic sensor.

A magnetic recording / reproducing method according to a fourth aspect of the present invention is a magnetic recording medium having a magnetic recording layer on a substrate, wherein at least a part of the magnetic recording layer has irreversible saturation magnetization upon heating. A plurality of magnetic bars formed of a magnetic material that increases in number and arranged in a barcode shape,
In a magnetic recording medium on which information is recorded by selectively heating the plurality of magnetic bars, after the plurality of magnetic bars are magnetized by applying a DC magnetic field, the residual magnetization of the heated magnetic bar and the heated magnetic bar are heated. The recorded information is reproduced by detecting the difference in the residual magnetization of the magnetic bar that has not been detected by the magnetic sensor.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in more detail with reference to the accompanying drawings according to embodiments of the present invention.

FIG. 1 of the accompanying drawings is a plan view of a magnetic recording medium according to an embodiment of the present invention, and FIG. 2 is a sectional view of the magnetic recording medium of FIG. 1 taken along line XX '. As shown in FIGS. 1 and 2, in the magnetic recording medium 1 of this embodiment, an irreversible magnetic recording layer 3 is provided in a predetermined area on a base 2. The irreversible magnetic recording layer 3 has a plurality (five in the embodiment shown) arranged in a barcode shape.
And the magnetic bar A constitutes a magnetic bar code 7. In this embodiment, the magnetic bars A are previously arranged in a pattern of equal width and at equal intervals. However, the present invention is not limited to this.
May be arranged in various patterns coded in advance, for example.

As best shown in the cross-sectional view of FIG.
In the magnetic recording medium 1 of this embodiment, a concealing layer 5 for concealing the presence of the magnetic bar A of the irreversible magnetic recording layer 3 formed on the base 2 and a protective layer 6 are sequentially laminated. I have.

FIG. 3 is a view similar to FIG. 2, showing the structure of a magnetic recording medium as another embodiment of the present invention. This figure 3
As shown in FIG. 2, in the magnetic recording medium of the present invention, a variable information magnetic recording layer 4 is formed on a substrate 2 and a plurality of bar codes are arranged thereon. A fixed information irreversible magnetic recording layer 3 including a magnetic bar A is formed, and a hiding layer 5 and a protective layer 6 are sequentially laminated.

The substrate 2 is made of a single or combined composite of a plastic film such as polyethylene terephthalate (PET) and polyvinyl chloride (PVC), paper and synthetic paper.

The magnetic bar A constituting the magnetic barcode 7 of the irreversible magnetic recording layer 3 is made of a magnetic material whose saturation magnetization is irreversibly increased by heating according to the present invention. The irreversible magnetic recording layer 3 is an irreversible recording layer.

Such irreversible changes in the magnetic material include, for example, crystallization of a nonmagnetic amorphous alloy such as a Ni—B alloy or a Mn—Ge alloy into a ferromagnetic crystalline alloy, Other transitions from unstable to stable phases can be utilized. Such a magnetic material and a magnetic recording medium using such a magnetic material are disclosed, for example, in Japanese Patent Application Laid-Open No. Hei 8-77622 by the present applicant. The irreversible recording layer formed on the magnetic recording medium disclosed in Japanese Patent Application Laid-Open No. 8-77622 is a continuous layer, not a barcode-shaped discrete layer.

The magnetic change temperature of the magnetic material forming the magnetic bar A according to the present invention may be higher than the temperature during reproduction. If the magnetic change temperature is too low, it becomes unstable with respect to heat and reliability is reduced. Further, the vicinity of the heating area is easily affected, and it becomes difficult to write accurate information. If the magnetic change temperature is too high, the heating temperature required for recording becomes high, which makes it difficult to select a heat-resistant resin for forming the base, and makes the recording apparatus expensive. The Curie temperature of the magnetic material is not particularly limited, and may be higher than the temperature during reproduction.

The irreversible magnetic recording layer 3 is formed by coating a coating or ink obtained by uniformly dispersing the above-described magnetic material in a binder resin made of a polyester resin, a vinyl chloride resin, a polyurethane resin, or a combination thereof on the substrate 2. Is formed by applying or printing a bar code.

The concealing layer 5 is formed by dispersing a highly opaque pigment in a polyester polyurethane resin or the like, and is provided on the magnetic barcode 7 by coating or printing. Examples of highly opaque pigments include aluminum paste and titanium oxide. The purpose of the pigment is to conceal the magnetic barcode 7 to enhance the forgery prevention effect.

The protective layer 6 has heat resistance, chemical resistance, water resistance,
It is provided as needed to improve storage stability such as abrasion resistance, for example, polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose,
Polyacrylamide, aqueous polyester polyurethane resin, vinyl chloride / vinyl acetate copolymer resin, polyester resin, polyurethane resin, acrylic resin, epoxy resin and the like are used. In some cases, in order to improve heat resistance, fine particles such as silicon oxide and calcium carbonate may be added as a filler in addition to these resins.

The irreversible magnetic recording layer 3 of the magnetic recording medium 1 of the present invention can be provided at an arbitrary position, such as a part of the substrate 2 or the whole surface, and in an arbitrary size. The arrangement position and size can be appropriately set according to the use to be used.

Further, in the magnetic recording medium of the present invention, as shown in the sectional view of FIG. 3, a variable information magnetic recording layer 4 for information recording / reproduction can be provided. This is usually used for a magnetic recording medium such as a magnetic card, a magnetic recording sheet, etc., and includes Fe, Co, Ni, γ-Fe ₂ O ₃ , Fe ₂
A known magnetic recording magnetic material such as O ₄ , Co-coated Fe ₂ O ₃ , barium ferrite, strontium ferrite, etc. was uniformly dispersed in a binder resin made of polyester resin, vinyl chloride resin, polyurethane resin or the like or a combination thereof. It is formed by applying or printing paint or ink on the substrate 2. The position and size of the variable information magnetic recording layer 4 can be appropriately set according to the intended use. Further, the variable information magnetic recording layer 4 may be composed of a layer made of at least two or more magnetic materials for magnetic recording having different coercive forces.

Next, a magnetic recording / reproducing method for the magnetic recording medium of the present invention having the above-described structure will be described.

First, a method of reading initial information in the irreversible magnetic recording layer 3 of the magnetic recording medium 1 will be described.
An irreversible magnetic recording layer 3 composed of a magnetic barcode 7 by a magnetic sensor such as a magnetic head, a Hall element, and a magnetic resistance element.
Scan above. At that time, as a DC magnetic field applying means for applying a DC magnetic field to the magnetic barcode 7, for example, a DC bias current applying circuit, a permanent magnet or the like is used, and after applying a DC magnetic field, a magnetic bar A is formed. The magnetic output is obtained as an electrical output from the residual magnetization of the magnetic material. If the magnetic material has a small residual magnetization and it is difficult to obtain a magnetic output with a magnetic sensor, the magnetic output is obtained as an electric output with a DC bias magnetic field applied as necessary.

As shown in FIGS. 1 to 3, like the magnetic bar code 7 of the irreversible magnetic recording layer 3 of the magnetic recording medium 1,
If the magnetic bars A are previously arranged in a pattern of equal width and at equal intervals, the initial information read by the above-described reading method without heating any of the magnetic bars A is as shown in FIG. Then, an output waveform appears at a location corresponding to the edge of each magnetic bar A.

Next, when writing predetermined information on the irreversible magnetic recording layer 3 of the magnetic recording medium of the present invention, as shown in the plan view of FIG. B is heated by a heat stamp, a thermal head, a laser beam, or the like, and then cooled to irreversibly change the magnetic properties of the magnetic material forming the magnetic bar. As a result, the magnetic bar B according to the previous heating pattern is heated and has different magnetic characteristics, that is, the saturation magnetization is irreversibly increased by heating.

The magnetic bar B, which has appeared by heating with a heat stamp, a thermal head, or a laser beam, has no change in appearance from the remaining unheated magnetic bar A, so that it is difficult to identify it visually. is there.

Subsequently, a DC magnetic field is applied to the irreversible magnetic recording layer 3 composed of the unheated magnetic bar A and the heated magnetic bar B by a magnetic sensor, or
When scanning while applying the voltage, as shown in FIG. 6, an output waveform appears at a portion corresponding to the edge portion of the unheated magnetic bar A and the heated magnetic bar B. The saturation magnetization of the magnetic material of the magnetic bar B is increased by heating with a heat stap, a thermal head, or a laser beam, and the output waveform from the magnetic bar B is compared with the output waveform from the magnetic bar A that is not heated. Therefore, the magnetic bar A that is not heated and the magnetic bar B that is heated can be detected.

The heating portion of the irreversible magnetic recording layer 3 cannot substantially return to the state before heating, for example, does not substantially crystallize or transition to a crystal phase before heating. The magnetic material itself is heated to a temperature much higher than the transition temperature (for example, 1300 ° C. for a Ni—B alloy), melted and quenched, thereby causing non-crystallization, irregular change, and a crystalline phase before heating. However, if such heating is performed, the resin base 2 will burn. Therefore, the information recorded on the irreversible magnetic recording layer 3 cannot be rewritten, and the information can be prevented from being falsified.

The information recorded on the irreversible magnetic recording layer 3 is not particularly limited. For example, the normal variable information magnetic recording layer 4
When used as a normal prepaid card in combination with the above, the variable information magnetic recording layer 4 records information generally required for the magnetic card such as the amount of issue and the number of issues, and the irreversible magnetic recording layer 3 Records information that needs to be rewritten each time it is used, such as the amount of money used or the number of remaining times, among the information recorded in the variable information magnetic recording layer 4. Each time such information is rewritten in the variable information magnetic recording layer 4, the information is additionally recorded in the irreversible magnetic recording layer 3. Even if the variable information magnetic recording layer 4 has been tampered with, the information in the irreversible magnetic recording layer 3 cannot be rewritten to the initial information.

The information recorded on the irreversible magnetic recording layer 3 is not limited to this. For example, an ID code may be recorded as unique data of a magnetic card. in this case,
If the information recorded in the variable information magnetic recording layer 4 is encrypted with this ID code, the contents of the variable information magnetic recording layer 4 of this magnetic card can be changed to the magnetic data recording layer of another magnetic card having another ID code. , It is impossible to read out the legitimate information.

Next, the irreversible magnetic recording layer 3 as described above is used.
, The reproduced output waveforms from the magnetic bar A before heating and the magnetic bar B after heating, with reference to FIGS.
This will be described in more detail. First, FIG. 7 illustrates the relationship between the magnetic bar A before heating and the reproduction output waveform thereof, and FIG. 7A shows a cross section of the magnetic bar A before heating on the base 2. 7 (B) shows an example of a reproduced output waveform generated corresponding to the magnetic bar A. FIG. As can be seen from these figures, the reproduced output waveform has a peak at a position corresponding to just the edge portion of the magnetic bar A, and these peak values are determined when the magnetic bar A is heated. However, since both the saturation magnetization and the residual magnetization remain small, they are low.

Next, FIG. 8 illustrates the relationship between the heated magnetic bar A and its reproduced output waveform, and FIG.
FIG. 8B shows a cross section of the magnetic bar B after heating on the substrate 2, and FIG. 8B shows a reproduced output waveform corresponding to the magnetic bar B. As shown in FIG. 8A, in this example, the entire magnetic bar is not heated by the thermal head but is partially heated in a range indicated by a dotted line. As can be seen from these figures, the reproduced output waveform is
The magnetic bar B has peaks at positions corresponding to the edge portion and at positions corresponding to both ends of the portion heated by the thermal head. The peak corresponding to the edge portion of the magnetic bar B is not ferromagnetic because the magnetic bar at that portion is not heated,
The peak corresponding to both ends of the heated portion has a relatively high peak value. It has what it has. In the case where a recording method in which only a part of the magnetic bar is heated as described above is adopted, an output having a close pitch can have a meaning such as being recognized as an address signal. Nevertheless, it is possible to record complicated fixed information. Therefore, there is a high possibility that unauthorized use such as falsification and alteration can be prevented.

Next, FIG. 9 illustrates the relationship between the magnetic bar A after being heated by another method and its reproduction output waveform, and FIG. A cross section of the magnetic bar B is shown, and FIG. 9B illustrates a reproduced output waveform corresponding to the magnetic bar B. In this example, as shown in FIG. 9A, the entire magnetic bar is heated by a thermal head. Heating by the thermal head covers a range shown by a dotted line. As can be seen from these figures, the reproduced output waveform has a peak at a position corresponding to the edge portion of the magnetic bar B, and the peak value is such that the entire magnetic bar B is heated. And ferromagnetic, it is considerably higher. It can be seen that the peak of the reproduced waveform appears at a pitch determined by the width of the magnetic bar B, and is not affected by the heating range of the thermal head. Therefore, by increasing the resolution of forming the magnetic bar, the accuracy of the detection output can be increased without having to increase the heating resolution by the thermal head.

Next, the present invention will be described in more detail with reference to specific examples.

Example 1 On one surface of a white polyethylene terephthalate film substrate having a thickness of 188 μm,
A magnetic ink made by mixing and dispersing a magnetic powder composed of ₅₅ Ge ₄₅ (atomic ratio) with a binder resin, a dispersant, and other additives and a solvent was used to form a magnetic ink by screen printing using a Tetron 350 wire plate by screen printing. An irreversible magnetic recording layer made of a magnetic barcode was formed so that the thickness after drying was 4 μm so as to obtain the magnetic pattern described above.

Next, a silver ink containing a pigment made of aluminum powder was formed on a magnetic recording layer via a magnetic barcode by a screen printing method so as to have a thickness of 1 μm after drying, thereby forming an opaque layer.

Further, a protective layer is formed on the concealing layer such that an ultraviolet curable offset ink composed of an acrylic resin to which silicon oxide particles are added as a filler is dried to have a thickness of 2 μm by an offset printing method. The magnetic card of FIGS. 1 and 2 was punched out to dimensions.

From the protective layer side of the magnetic card having such an irreversible magnetic recording layer, 1000 Oe
With a DC bias magnetic field of
When reading was performed under the condition of 0 mm / sec, the reproduced output peak was obtained at the edge portions of all the magnetic bars as shown in FIG.

Next, from the protective layer side of the magnetic card having the above-mentioned irreversible magnetic recording layer, a heating energy of 1.0 mJ / dot, a pulse width of 2 ms, a heating cycle of 3 m and a pattern of FIG. Under the condition of seconds, a part of the magnetic barcode was written and heated by the thermal head.

When reading was performed at a reading speed of 300 mm / sec from the protective layer side of the written and heated magnetic card of FIG. 5 with a magnetic head applied with a DC bias magnetic field of 1000 Oe, as shown in FIG. The reproduction output peak at the edge of the magnetic bar on which writing and heating was performed by the thermal head increased to five times that before heating, and the same reproduction waveform as before writing and heating could not be obtained.

Example 2 A barium ferrite magnetic powder having a coercive force of 2750 Oe was coated on a whole surface of one surface of a white polyethylene terephthalate film substrate having a thickness of 188 μm with a binder resin, a dispersant, a curing agent, other additives and a solvent. Was mixed and dispersed to obtain a variable information magnetic recording layer, which was applied by a gravure method so that the thickness after drying was 12 μm, and was oriented in a magnetic field and dried.

Next, on this variable information magnetic recording layer, Mn was added.
A magnetic ink made by mixing and dispersing a magnetic powder composed of ₅₅ Ge ₄₅ (atomic ratio) with a binder resin, a dispersant, and other additives and a solvent was used to form a magnetic ink by screen printing using a Tetron 350 wire plate by screen printing. The magnetic barcode was formed such that the thickness after drying was 4 μm so as to obtain the magnetic pattern described above.

Next, a silver ink containing a pigment made of aluminum powder was formed on a magnetic recording layer via a magnetic barcode by a screen printing method so as to have a thickness of 1 μm after drying, thereby forming an opaque layer.

Further, a protective layer is formed on the concealing layer such that an ultraviolet curable offset ink composed of an acrylic resin to which silicon oxide particles are added as a filler is dried to a thickness of 2 μm by an offset printing method. The magnetic card of FIG. 3 was punched out to dimensions.

From the protective layer side of the magnetic card having such an irreversible magnetic recording layer, 5000 Oe is applied by a magnetic head.
After demagnetizing the variable information magnetic recording layer by applying an erasing magnetic field of, a reading speed of 300 mm /
When reading was performed under the condition of seconds, reproduction output peaks were obtained at the edges of all the magnetic bars as shown in FIG.

Next, from the protective layer side of the magnetic card having the above-mentioned irreversible magnetic recording layer, a heating energy of 1.0 mJ / dot, a pulse width of 2 msec, a heating cycle of 3 m Under the condition of seconds, a part of the magnetic barcode was written and heated by the thermal head.

When reading was performed at a reading speed of 300 mm / sec with a magnetic head applied with a DC bias magnetic field of 1000 Oe from the protective layer side of the magnetic card of FIG. 3 which was written and heated, as shown in FIG. The reproduction output peak at the edge of the magnetic bar on which writing and heating was performed by the thermal head increased to five times that before heating, and the same reproduction waveform before writing and heating could not be obtained.

[0059]

According to the present invention, a magnetic card can be manufactured at a lower cost than a conventional magnetic card because a step of simultaneously forming a dummy barcode and a magnetic barcode having different magnetic characteristics is not performed when manufacturing a magnetic card. Furthermore, since the magnetic pattern of the magnetic barcode is formed in a pattern that can be formatted, an ID code unique to each card can be recorded by heating before use, and it is impossible to tamper with it. The effect of preventing forgery by duplication becomes extremely high.

In general, a magnetic recording medium has an advantage that information can be easily recorded and information can be rewritten, but it has a disadvantage that information can be easily falsified in a magnetic card application. . On the other hand, the magnetic recording medium of the present invention does not require the fixed information unique to the medium to be formed in a pattern at the time of manufacture, and the fixed information unique to the medium can be individually written after the manufacture. Since there is no need to combine with a dummy barcode, the manufacturing process can be simplified.

Further, it is extremely difficult to falsify information, so that the security when applied to a magnetic card is high, and since information can be magnetically read unlike optical reading, a recording / reproducing apparatus can be inexpensive. .

Further, according to the present invention, writing and heating can be performed on the magnetic bars arranged in advance in a bar code shape. Therefore, unlike the case where writing and heating are performed on a continuous magnetic recording layer, a thermal head or the like is used. There is room for positional accuracy when heating. Even if the heating position is slightly shifted, an output can be obtained at the edge of the magnetic bar. Since the position restriction is easy, not only the thermal head but also a heat stamp, a heating bar (resistor) or the like can be used as a heating source.

According to the present invention, when the magnetic bar of the magnetic barcode is provided in a convex shape on the surface of the base, only the magnetic bar can be heated. Since the lower layer (the variable information magnetic recording layer and the base) of the magnetic barcode is not strongly heated, the damage is small. Since it is not necessary to use a heat-resistant material for the variable information magnetic recording layer and the substrate, the range of material selection is expanded.

When writing and heating is performed on a continuous magnetic recording layer as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 8-77622, an output is obtained at a heated / unheated edge portion. Is often attenuated by the thermal conductivity of the material. That is, if the magnetic material forming the magnetic recording layer has good thermal conductivity, the heated / unheated edge portion becomes ambiguous, and the output becomes small. On the other hand, when the thermal conductivity is poor (as is the case with a general dispersion film), the output decreases because the structural change rate in the thickness direction is low and the film thickness cannot be increased. On the other hand, in the heating for writing to the magnetic barcode according to the present invention, since an output is obtained at the edge of the magnetic bar, a large output can be obtained even when heating with high energy (because the edge is clear).

[Brief description of the drawings]

FIG. 1 is a plan view of a magnetic recording medium as one embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX ′ of the magnetic recording medium of FIG. 1;

FIG. 3 is a view similar to FIG. 2, showing the structure of a magnetic recording medium as another embodiment of the present invention.

FIG. 4 is a diagram exemplifying a reproduction output waveform obtained from a magnetic barcode before heating the magnetic recording medium of FIG. 1;

FIG. 5 is a plan view illustrating a write heating pattern of the magnetic recording medium of FIG. 1;

FIG. 6 is a diagram exemplifying a reproduction output waveform obtained from a magnetic barcode of a magnetic recording medium after performing writing and heating as shown in FIG. 5;

FIG. 7 is a diagram illustrating a relationship between a magnetic bar before heating and a reproduction output waveform thereof.

FIG. 8 is a diagram illustrating a relationship between a heated magnetic bar and a reproduced output waveform thereof.

FIG. 9 is a diagram exemplifying a relationship between a magnetic bar after heating in another manner and a reproduction output waveform thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic recording medium 2 Substrate 3 Irreversible magnetic recording layer 4 Variable information magnetic recording layer 5 Hiding layer 6 Protective layer 7 Magnetic barcode A Magnetic bar B Heated magnetic bar

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 5/80 G06K 19/00 B 23/00 A G07F 7/08 Z

Claims (10)

[Claims] 1. A magnetic recording medium having a magnetic recording layer on a substrate, wherein at least a part of the magnetic recording layer is formed of a magnetic material whose saturation magnetization is irreversibly increased by heating, and a bar code. A magnetic recording medium comprising a plurality of magnetic bars arranged in a shape. 2. The magnetic recording according to claim 1, wherein the magnetic recording layer comprises a fixed information magnetic recording layer and a variable information magnetic recording layer, and the plurality of magnetic bars are provided on the fixed information magnetic recording layer. Medium. 3. The magnetic recording medium according to claim 1, wherein the magnetic bars are arranged in advance in a pattern having an equal width and an equal interval. 4. The magnetic recording medium according to claim 1, wherein the magnetic bars are arranged in a pattern coded in advance. 5. A magnetic recording medium having a magnetic recording layer on a substrate, wherein at least a part of the magnetic recording layer is formed of a magnetic material whose saturation magnetization is irreversibly increased by heating. In a magnetic recording medium including a plurality of magnetic bars arranged in a barcode, fixed information unique to the medium is recorded by selectively heating some of the plurality of magnetic bars. Magnetic recording method. 6. A magnetic recording medium having a magnetic recording layer on a substrate, wherein at least a part of the magnetic recording layer is formed of a magnetic material whose saturation magnetization is irreversibly increased by heating; In a magnetic recording medium including a plurality of magnetic bars arranged in a bar code shape, by selectively heating some of the plurality of magnetic bars, the use condition of the medium is recorded. Magnetic recording method. 7. The magnetic recording method according to claim 5, wherein the heating of the magnetic bar heats the entire magnetic bar. 8. The magnetic recording method according to claim 5, wherein the heating of the magnetic bar heats only a part of the magnetic bar. 9. A magnetic recording medium having a magnetic recording layer on a substrate, wherein at least a part of the magnetic recording layer is formed of a magnetic material whose saturation magnetization is irreversibly increased by heating; In a magnetic recording medium including a plurality of magnetic bars arranged in a barcode shape and recording information by selectively heating the plurality of magnetic bars, the plurality of magnetic bars are magnetized by applying a DC magnetic field to the plurality of magnetic bars. And reproducing the recorded information by detecting a difference in magnetization between the heated magnetic bar and the unheated magnetic bar by a magnetic sensor. 10. A magnetic recording medium having a magnetic recording layer on a substrate, wherein at least a part of the magnetic recording layer is formed of a magnetic material whose saturation magnetization is irreversibly increased by heating; In a magnetic recording medium including a plurality of magnetic bars arranged in a barcode shape and recording information by selectively heating the plurality of magnetic bars, after magnetizing by applying a DC magnetic field to the plurality of magnetic bars, And reproducing the recorded information by detecting the difference between the residual magnetization of the heated magnetic bar and the residual magnetization of the unheated magnetic bar with a magnetic sensor.