JPH10149538A - Magnetic recording medium and method for reading magnetic information - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent recording information from being forged and to perfectly exclude a fraudulently altered card, etc., by forming a recording layer into two recording layers of a heard magnetic layer and a high coersive force layer containing magnetic power having its Curie point of lower than a specific temp. and confirming a change of an output level of the recording layers in advance. SOLUTION: This magnetic recording medium 1 is provided with a substrate 10 and a magnetic recording part 20 formed on the substrate 10, and the magnetic recording part 20 is equipped with a two-layer laminated body of the hard magnetic layer 21 and the low Curie point and high coersive force magnetic layer 25 containing the magnetic powder with a Curie point <=200 deg.C. Then, the hard magnetic layer 21 and the low Curie point and high coersive force magnetic layer 25 are recorded with magnetic information in the same patterns or inverted magnetizing patterns to each other (as shown in the figure for the latter). Consequently, an enough output difference can be obtained by this medium 1 before and after magnetic erasing of magnetic information of the hard magnetic layer 21, and hence the using state of the medium 1 can be expressed by magnetic erasing of the head magnetic layer. Then, since it is difficult to restore the medium 1 into its nonused state before magnetic erasing, the card is prevented from being forged.

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 more particularly to a magnetic recording medium such as a magnetic card having a magnetic recording section formed for preventing forgery and a method for reading the same.

[0002]

2. Description of the Related Art Conventionally, in order to prevent forgery of a card such as a prepaid card, for example, non-rewritable fixed information having a predetermined magnetic pattern is formed on a card in advance. This is to determine the authenticity of the card by reading a magnetic pattern formed in advance when used and determining whether a predetermined magnetic output signal is obtained.

In reading such a magnetic pattern,
Usually, a magnetic head wound with two coils is used. A constant current is applied to one of the coils of the magnetic head, and the induced current or voltage induced when the magnetic head scans the magnetic pattern is applied to the other coil. To detect. The induced current is generated according to a change in the magnetic flux of the magnetic head.

On the other hand, as a material constituting the magnetic pattern, for example, a ferromagnetic material is used, and various shapes of the magnetic pattern are conceivable. A so-called bar code pattern is generally used. . The magnetic pattern, which is a barcode pattern, is configured by arranging a plurality of magnetic bars, which are pattern elements, in the width direction, and the width of each magnetic bar constituting the magnetic pattern is one or two. Formed from more than one kind.

[0005] Then, by scanning the bar-code-shaped magnetic pattern at a constant speed with the above-mentioned magnetic head in close contact with each other, a magnetic output signal corresponding to the magnetic pattern is obtained.

[0006] As a method of forming a magnetic pattern, it is known to use a screen printing method, an offset printing method, a gravure printing method, or the like, and these printing methods are advantageous in terms of manufacturing cost.

[0007]

However, pattern formation by the printing method has a physical limit in reducing the printing line width itself due to the characteristics of the printing method.
As the recording density cannot be improved or the recording density is increased, the ink transfer becomes unstable, and the printing shape becomes uneven due to the ink leveling. However, there is a problem that the magnetic output and the waveform become unstable, and it is difficult to obtain accurate information.

In order to solve such a problem, the applicant of the present application has already provided a magnetic layer with fine irregularities using a laser or the like on a magnetic layer and uses the magnetic layer as fixed information like a magnetic barcode. (Japanese Patent Application No. Hei 7-1348)
No. 11). Japanese Patent Laid-Open No. 7-210 discloses a similar technique.
No. 859 proposes a magnetic recording medium in which two magnetic layers are stacked on a substrate to prevent counterfeiting of recorded information, and one of the magnetic layers has a dense / dense pattern of a magnetic material. .

However, in any of the above proposals, the output level of recorded information obtained from the same medium does not basically change due to the configuration of the magnetic layer. In this application, by paying attention to this point, the present invention provides a magnetic recording medium in which the output level of recording information obtained from the same medium changes, and confirms the change in the output level in advance, so that the recording information can be recorded more than before. The purpose is to prevent forgery and completely eliminate falsified cards and the like.

[0010]

In order to achieve the above object, the present invention provides a magnetic recording medium comprising a substrate and a magnetic recording section formed on the substrate, wherein the magnetic recording medium comprises: The part includes a two-layer laminate of at least a hard magnetic layer and a low Curie point / high coercive force magnetic layer including a magnetic powder having a Curie point Tc of 200 ° C. or less, and includes a hard magnetic layer and a low Curie point / high coercive force magnetic layer. Are configured such that magnetic information of the same pattern is recorded.

[0011] The present invention also provides a magnetic head having the same pattern as the low Curie point / high coercive force magnetic layer while heating the low Curie point / high coercive force magnetic layer to a temperature exceeding the Curie point Tc. Are written simultaneously.

Further, the present invention is a magnetic recording medium comprising a substrate and a magnetic recording portion formed on the substrate, wherein the magnetic recording portion has at least a hard magnetic layer, a Curie point Tc of 200 It has a two-layer laminate of a low Curie point and high coercivity magnetic layer containing a magnetic powder of less than or equal to ℃. The hard magnetic layer and the low Curie point and high coercivity magnetic layer record magnetic information of patterns whose magnetizations have been inverted with respect to each other. It is configured to be.

Further, according to the present invention, magnetic information is previously written on the hard magnetic layer, and thereafter, the low Curie point
By heating the high coercivity magnetic layer to a temperature exceeding the Curie point Tc, magnetic information written in the hard magnetic layer is transferred to the low Curie point / high coercivity magnetic layer.

According to the present invention, there is provided a method for reading magnetic information recorded on the magnetic recording medium, the method comprising:
The magnetic head was scanned over the two-layer laminate of the magnetic recording unit to read the initially set magnetic information, and then erased at least a portion of the magnetic information written to the hard magnetic layer. Thereafter, the magnetic information read in the erasure area is compared with the first magnetic information read before erasure.

The present invention also provides a method for reading magnetic information recorded on the magnetic recording medium, the method comprising:
A magnetic head is scanned over the two-layer laminate of the magnetic recording section to erase a predetermined portion of the magnetic information written in the hard magnetic layer from among the initially set magnetic information. The remaining portion that has not been included is recognized as an unerased area.

Further, according to the present invention, a predetermined portion of the magnetic information written in the hard magnetic layer is erased in accordance with the usage amount, and thereafter, the remaining usage amount is determined from the extent of the remaining unerased area which has not been erased. Is configured to determine.

[0017]

Embodiments of the present invention will be described below in detail. FIGS. 1 to 8 show drawings for explaining an embodiment of the present invention.
1 is a perspective view of a card-shaped magnetic recording medium as an example of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1 and shows a state before magnetic information is recorded.

As shown in FIGS. 1 and 2, the magnetic recording medium 1 of the present invention includes a substrate 10 and a magnetic recording section 20 formed on the substrate 10.

Substrate 1 constituting magnetic recording medium 1 of the present invention
0, considering heat resistance, strength, rigidity, etc. required as a substrate, nylon, cellulose diacetate, cellulose triacetate, vinyl chloride, polystyrene, polyethylene, polypropylene, polyester, polyimide,
It can be composed of a single or combination of materials appropriately selected from materials such as resins such as polycarbonate, metals such as copper and aluminum, paper, and impregnated paper. Also, a so-called photodegradable or biodegradable plastic material may be used. The thickness of such a substrate 10 can be about 0.005 mm to 5 mm.

When the hard magnetic layer 21 is formed by a method of applying a so-called magnetic paint, the hard magnetic layer 21 is made of a magnetic powder exhibiting hard magnetism (hereinafter simply referred to as “hard magnetic powder”). ]) And a resin binder. As the hard magnetic powder to be contained, for example, γ
-Fe ₂ O ₃ , Co-coated γ-Fe ₂ O ₃ , Fe ₃ O ₄ ,
Fe, Fe-Cr, Fe-Co, Co-Cr, Co-N
i, magnetic fine particles such as Ba ferrite, Sr ferrite, and CrO ₂ .

As the resin binder (or ink vehicle) in which the above hard magnetic powder is dispersed, butyral resin, vinyl chloride / vinyl acetate copolymer resin, urethane resin, polyester resin, cellulose resin, acrylic resin, styrene / maleic Acid copolymer resin or the like is used,
If necessary, a rubber-based resin such as a nitrile rubber or a urethane elastomer is added. Further, a radiation-curable resin such as an ultraviolet-curable type or an electron beam-curable type may be used. UV-curable resin components include photopolymerizable oligomers such as epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, silicone acrylate, and unsaturated polyester; monofunctional acrylates (styrene, vinyl acetate, etc.), polyfunctional acrylates, etc. Benzoin-based, acetophenone-based, thioxanthone-based, peroxide-based photopolymerization initiators; amine-based, quinone-based photopolymerization initiators; thermal polymerization inhibitors, inorganic or organic Other additives such as a filler, an adhesive imparting agent, a thixotropic agent, a plasticizer, and a non-reactive polymer; and a coloring agent such as a pigment. The electron beam-curable resin component may be prepared by excluding the photopolymerization initiator from the ultraviolet-curable resin component. Further, in consideration of heat resistance, a resin having a high glass transition temperature (Tg), such as polyamide, polyimide, or polyether sulfone, or a system whose Tg increases by a curing reaction can be used as the resin binder. In a dispersion obtained by dispersing magnetic particles in the resin or ink vehicle as described above, if necessary, a surfactant,
A pigment such as a silane coupling agent, a plasticizer, a wax, a silicone oil, or carbon may be added. As a coating method, a known method such as a gravure method, a roll method, or a knife edge method is used.

The hard magnetic layer 21 is not limited to the above-described coating method, but can be formed by a vacuum evaporation method, a sputtering method, a plating method, or the like using the above-described magnetic material itself.

In the present invention, the hard magnetic layer 21 is a magnetic layer mainly for recording or erasing magnetic information which can be rewritten at room temperature, and also has a function as an original magnetic information source for magnetic transfer.

On such a hard magnetic layer 21, a low Curie point / high coercive force magnetic layer 25 is formed. The low Curie point / high coercive force magnetic layer 25 has a Curie point Tc of 200 ° C.
Hereinafter, it is particularly configured to include a magnetic powder at 100 to 150 ° C. When the Curie point Tc exceeds 200 ° C., when performing magnetic writing or magnetic transfer to the low Curie point / high coercive force magnetic layer 25 as described later, the thermal load increases, and the thermal damage to the substrate 10 increases. There is a disadvantage that writing unevenness due to the magnetic head is likely to occur.

As in the case of the hard magnetic layer 21, the low Curie point / high coercive force magnetic layer 25 has a low Curie point / high coercive force magnetic property when it is formed by applying a so-called magnetic paint. As a constituent material of the layer 25, a magnetic powder exhibiting characteristics of a low Curie point and a high coercive force as described above and a resin binder are contained. As the magnetic powder material showing a characteristic of a low Curie point, a high coercive force, the magnetic material of coercive force than 4000Oe an A in and Curie point Tc 200 ° C. or less of the magnetic material at room temperature, for example, A-O _{n
{(Fe 1-xy Cr x} Zn y) 2 O 3}, A · O n
_{{(Fe 1-x Cr x} ) 2 O 3}, A · O n {(Fe 1-x
_{Al x) 2 O 3},} A · O n {(Fe 1-x Ga x) 2 O 3
_{}, A · O n {(} Fe 1-xyz Ga x Cr y Al z) 2
_{O 3}, A · O n} {(Fe 1-xy Cr x Ga y) 2 O 3
Sr ferrite or Ba ferrites represented by｝ or the like (where A represents one or two selected from Sr and Ba, and n represents 5 to 6);
₂ ; CrTe and the like. Among them, in particular, CrO ₂
It is preferable to use CrTe or CrTe. The resin binder and other additional components used are as described for the hard magnetic layer 21. Further, the low Curie point / high coercive force magnetic layer 25 can also be formed by using the above magnetic material by a vacuum evaporation method, a sputtering method, a plating method, or the like.

In the present invention, the low Curie point / high coercivity magnetic layer 25 cannot be erased or rewritten by a magnetic head at normal temperature, and is functionally used as fixed information. In order to write or erase information, heating exceeding the Curie point Tc is required.

Such a hard magnetic layer 21 has a low Curie point.
The magnetic information initially set as the initial product state (unused state) of the magnetic recording medium is recorded on the high coercivity magnetic layer 25. As a first mode of the recording pattern, as shown in FIG. 3, a magnetic information having the same pattern is recorded on the hard magnetic layer 21 and the low Curie point / high coercivity magnetic layer 25, respectively.

The magnetic information of the same pattern is formed by the following method. That is, while the low Curie point / high coercive force magnetic layer 25 is heated to a temperature exceeding the Curie point Tc, the magnetic head for writing has a low Curie point / high coercive force.
Magnetic information is formed by simultaneously writing magnetic information of a predetermined pattern on the high coercivity magnetic layer 25 and the hard magnetic layer 21. In this case, the magnetization direction in each magnetic layer is
As shown in FIG. 3, the upper and lower magnetic layers 21 and 25 have the same form, and magnetic information of the same pattern is recorded.

As a second mode of the recording pattern, as shown in FIG. 4, the hard magnetic layer 21 and the low Curie point / high coercive force magnetic layer 25 record magnetic information of a pattern whose magnetization is reversed with respect to each other. Are included.

The magnetic information of the mutually inverted patterns is formed by the following method. That is, as shown in FIG. 5, predetermined magnetic information is previously written only in the hard magnetic layer 21 at normal temperature, and thereafter, the low Curie point / high coercive force magnetic layer 25 is heated to a temperature exceeding the Curie point Tc. As a result, the magnetic information previously written on the hard magnetic layer 21 is transferred to the low Curie point / high coercive force magnetic layer 25 (FIG. 4). In this case, the magnetization directions of the upper and lower magnetic layers 21 and 25 are reversed at the time of transfer as shown in FIG. 4, and the upper and lower layers form magnetic information of a pattern whose magnetization is reversed with respect to each other.

The magnetic recording unit 20 (the magnetic layer 2)
As shown in FIG. 2, a concealing layer 40 may be provided on the magnetic recording unit 20 for the purpose of concealing the magnetic recording unit 20, adjusting the color tone of the medium, and making printed characters easy to see. preferable.

The concealing layer 40 is made of a cellulose derivative such as ethyl cellulose, cellulose nitrate, ethyl hydroxyethyl cellulose, cellulose acetate propionate or cellulose acetate; a styrene resin such as polystyrene or poly-α-methylstyrene, or a styrene copolymer resin;
Acrylic resin or methacrylic resin such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, polybutyl acrylate, etc. alone or copolymerized resin; rosin, rosin-modified maleic resin, rosin-modified phenolic resin, polymerized rosin, etc. Rosin ester resin; Add various pigments to binders such as polyvinyl acetate resin, coumarone resin, vinyl toluene resin, vinyl chloride resin, polyester resin, polyurethane resin, butyral resin according to the color to be colored, and if necessary Titanium oxide, alumina powder, microsilica, etc. are added to provide a magnetic head cleaning effect, and if necessary, plasticizers, stabilizers, waxes, greases, drying agents, drying aids, curing agents, thickeners Solvent or diluent is sufficient after adding the dispersant and dispersant Using a kneading was formed by colored paints or inks, conventional gravure method, a roll method, a knife edge method, the method or printing method for applying the offset method or the like, is formed.

Further, a protective layer for improving the protection and decoration effect may be formed on the concealing layer 40.

Next, the reading method of the present invention using the magnetic recording medium having the magnetic information of the recording pattern according to the first or second embodiment will be described.

First, the reading method (1) will be described.

Reading Method (1 ) The magnetic information for reading (for example, the state shown in FIG. 4) is read by scanning a reading magnetic head over the two-layer laminate of the magnetic recording section 20. Next, the hard magnetic layer 21
All of the magnetic information written in is erased by the erasing magnetic head (the state of FIG. 6). At this time, the recorded information written in the low Curie point / high coercive force magnetic layer 25 remains as it is. Thereafter, the remaining magnetic information is read by scanning the magnetic head for reading over the two-layer laminate of the magnetic recording unit 20 again. Then, the remaining magnetic information (the state shown in FIG. 6) is compared with the magnetic information read first before the erasure (the state shown in FIG. 4). As a result of such collation, the hard magnetic layer 2
If the contents of the magnetic information before and after the erasure of the magnetic information written in No. 1 are substantially the same and only the output level is different, the data written on this magnetic recording medium is unmodified. Data can be determined.

That is, in the case of the magnetic recording medium having the magnetic information of the recording pattern according to the second embodiment shown in FIGS. 4 and 6, the output level is reduced by the amount of erasing the magnetic information written in the hard magnetic layer 21. Increase. In the initial product state (unused state), the magnetization is reversed and the magnetic field is canceled, so that the initial output level is low, and the magnetic information in the hard magnetic layer 21 is erased. Is canceled. On the contrary,
In the case of the magnetic recording medium having the magnetic information of the recording pattern according to the first aspect shown in FIG. 3, the output level is reduced by the amount of erasing the magnetic information written in the hard magnetic layer 21. This is because one of the magnetic information of the same pattern is lost.

In order to facilitate understanding of the present invention, a case where all magnetic information written in the hard magnetic layer 21 is erased by an erasing magnetic head before collation with magnetic information has been described as an example. However, without being limited to this, after a part of the magnetic information written in the hard magnetic layer 21 is erased by the erasing magnetic head, the magnetic information read in this erasing area is the first magnetic information read before erasing. You may make it collate with magnetic information. This also makes it possible to determine the authenticity of the data written on the magnetic recording medium.

Next, the reading method (2) will be described.

Reading Method (2 ) The magnetic head for erasing is scanned over the two-layer laminated body of the magnetic recording section 20, and the magnetic information initially set (for example, FIG.
Of the magnetic information written in the hard magnetic layer 21 (for example, the region L shown in FIG. 7).
Then, the scanning magnetic head is again scanned,
By judging the output level change area, the remaining part that has not been erased can be recognized as an unerased area (for example, the remaining part of the area L shown in FIG. 7). More specifically, for example, it can be used so that the relationship between the used amount and the remaining used amount in the pre-bayed card can be recognized. That is, a part of the magnetic information written in the hard magnetic layer 21 is erased according to the used amount. At this time, the recorded information written in the low Curie point / high coercive force magnetic layer 25 remains as it is. Therefore, the relationship between the used amount and the remaining used amount is confirmed by scanning the magnetic head for reading again and judging the area where the output level changes. In this regard, an effect equivalent to a magnetic punch hole indicating that the magnetic card has been used can be exerted.

In the magnetic recording medium of the present invention, after erasing the magnetic information written in the hard magnetic layer 21, it is extremely difficult to restore the state before the erasing, and the magnetic recording medium after use is completed. Would be impossible to reuse illegally. This is because it is almost impossible to write magnetic information of a pattern exactly the same as the recorded information written in the low Curie point / high coercive force magnetic layer 25 or a pattern whose magnetization is inverted. Even if similar magnetic information can be written, slight recording deviation causes interference between recording signals, and an appropriate output level cannot be obtained. Therefore, by demagnetizing the magnetic information written on the hard magnetic layer 21 after or during use, it is possible to prevent the prepaid card or the like from being altered to an unused state.

The magnetic recording section 20 provided in the magnetic recording medium of the present invention described above has been described by taking as an example the case where the low Curie point / high coercive force magnetic layer 25 is laminated on the hard magnetic layer 21. The order of lamination may be reversed without being limited to the order of lamination. Further, a new hard magnetic layer can be further laminated on the low Curie point / high coercive force magnetic layer 25 of the magnetic recording medium of the present invention described above.

The magnetic information initially set as the initial product state (unused state) of the magnetic recording medium is as follows:
It can be said that the recording pattern of the second embodiment is more preferable than the recording pattern of the first embodiment. This is because it is necessary to pay close attention to the technical aspect of making the temperature at the time of heating and writing in forming the recording pattern of the first embodiment uniform.

[0044]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention.

Example 1 First, in order to form a two-layer laminate of the hard magnetic layer 21 and the low Curie point / high coercive force magnetic layer 25, a magnetic paint 1 and a magnetic paint 2 having the following compositions were prepared. Got ready.

(Magnetic paint 1 for forming hard magnetic layer 21) Hard magnetic powder (Ba ferrite): 41 parts by weight Polyurethane resin: 7 parts by weight Toluene: 25 parts by weight Methyl ethyl ketone: 25 parts by weight Isocyanate-based Curing agent 2 parts by weight (magnetic coating 2 for forming low Curie point / high coercive force magnetic layer 25) CrO ₂ magnetic powder (Tc = 124 ° C) 41 parts by weight Polyurethane resin 7 parts by weight Toluene 25 Part by weight-Methyl ethyl ketone ... 25 parts by weight-Isocyanate-based curing agent ... 2 parts by weight Next, a card made of polyethylene terephthalate (thickness: 250 m) as a substrate (substrate) to be printed is prepared, and gravure coat printing is performed on the card. After applying the magnetic paint 1 in a stripe form and performing a magnetic alignment treatment, the magnetic paint 1 is left at room temperature. Was dried to form a hard magnetic layer 21 having a coating thickness of 10 μm, a coating width of 7 mm, and a coating length of 85 mm. Thereafter, a magnetic paint 2 for forming a low Curie point / high coercive force magnetic layer 25 is applied on the hard magnetic layer 21 to a coating thickness of 10 μm by a gravure coat printing method, and a magnetic orientation treatment and a drying treatment are performed. A magnetic card provided with a magnetic recording section 20 composed of a two-layer laminate was manufactured.

Next, magnetic information was written to the magnetic recording section 20 in the first mode of the recording pattern, thereby setting the initial product state (unused state) of the magnetic recording medium. That is, the magnetic card is heated to 130 ° C. using an infrared lamp, and magnetic information is written by a write magnetic head,
Thereafter, the magnetic card was cooled to room temperature. In this state, as shown in FIG. 3, the hard magnetic layer 21 and the low Curie point / high coercive force magnetic layer 25 are magnetized, and the magnetization pattern of each magnetic layer is as shown in FIG. It was confirmed that the same pattern of magnetic information was recorded on both layers.

Product state of this initial (unused state)
When the magnetic information was read by a read magnetic head, an output value A was obtained. Next, the magnetic information was subjected to DC demagnetization using a magnetic head for erasing. This state is shown in FIG.
As shown in FIG. 7, magnetic information remained only in the low Curie point / high coercive force magnetic layer 25. When this information was read by a magnetic head for reading, an output value B was obtained. As a result of this experiment, it was confirmed that the output value A> the output value B, and that the output ratio A / B was about 1.8.

(Embodiment 2) First, a magnetic card before magnetic information was inserted was produced in the same manner as in Embodiment 1 above.

Next, magnetic information was given to the magnetic recording portion in the second mode of the recording pattern to obtain the initial product state (unused state) of the magnetic recording medium. That is, first, magnetic information was written to the hard magnetic layer 21 by the write magnetic head as shown in FIG. 5 (at this time, the low Curie point / high coercive force magnetic layer 25 is not magnetically recorded at room temperature). Next, using an infrared lamp, the magnetic card is
After heating to ℃, the magnetic card was cooled to room temperature. In this state, as shown in FIG. 4, the hard magnetic layer 21 and the low Curie point / high coercive force magnetic layer 25 were magnetized. That is, the magnetic card is moved to the Curie point Tc.
By heating as described above, it was confirmed that the magnetic information previously contained in the hard magnetic layer 21 was transferred to the low Curie point / high coercive force magnetic layer 25 side. As shown in FIG. 4, it was confirmed that the magnetic pattern of each magnetic layer recorded the magnetic information of the pattern in which both layers were magnetization reversed (the magnetic pattern of the magnetic layer 25 was the magnetic information of the magnetic layer 21). Since it is a copy, the magnetization is reversed during transfer).

Product state of this initial (unused state)
When the magnetic information (state in FIG. 4) was read by a read magnetic head, an output value C was obtained. Next, the magnetic information was subjected to DC demagnetization using a magnetic head for erasing.
In this state, as shown in FIG. 6, magnetic information remains only in the low Curie point / high coercive force magnetic layer 25. When this information was read by a magnetic head for reading, an output value D was obtained. As a result of this experiment, output value C <output value D
It was confirmed that the output ratio C / D was about 0.2.

Example 3 In Example 1, the order of lamination of the hard magnetic layer 21 and the low Curie point / high coercive force magnetic layer 25 was changed, and the low Curie point / high coercive force magnetic layer 25 and the hard magnetic layer 21 were stacked. They were laminated in order. Otherwise, in the same manner as in Example 1, a sample of Example 3 was produced. When the magnetic information was written, the magnetic information was erased, and the magnetic information was read (reproduced) in the same manner as in the first embodiment, the same experimental results as in the first embodiment were obtained.

Embodiment 4 Embodiments 1 and 2 above
The magnetic layer 25 having a low Curie point and high coercive force after demagnetization.
Magnetic information is written to the hard magnetic layer 21 using a commercially available read / write (R / W) head for a state in which magnetization remains only in the card, that is, in a state shown in FIGS. As shown in FIGS. 3 and 4, it was confirmed whether the state could be returned to the state before demagnetization (the initial product state).

As a result, even when the same magnetic information as that of the low Curie point / high coercive force magnetic layer 25 is written by the magnetic head, the waveform peaks of the hard magnetic layer 21 and the low Curie point / high coercive force magnetic layer 25 do not completely match. As a result, the two waveforms become interference waveforms, and the entire waveform does not show a uniform output level and swells. This is because all peaks do not completely match due to slight unevenness in the transport speed,
It was confirmed that it was practically impossible to return to the state before erasing using the magnetic head.

[0055]

The effects of the present invention are clear from the above results. That is, the present invention relates to a magnetic recording medium including a substrate and a magnetic recording unit formed on the substrate,
The magnetic recording section includes a two-layer laminate of at least a hard magnetic layer and a low Curie point / high coercive force magnetic layer containing a magnetic powder having a Curie point Tc of 200 ° C. or less. The magnetic information of the same pattern or a pattern whose magnetization is inverted with respect to each other is recorded in the magnetic layer.

Therefore, in this medium, a sufficient output difference can be obtained before and after demagnetization of the magnetic information of the hard magnetic layer, and it is possible to express the use condition of the medium by demagnetization of the hard magnetic layer. Also,
It is extremely difficult to return to the state before demagnetization, that is, the initial product state (unused state) of the magnetic recording medium using the magnetic head. If the present invention is applied to a prepaid card or the like, extremely high security is achieved. It becomes a magnetic recording medium and can prevent forgery of the card.

[Brief description of the drawings]

FIG. 1 is a perspective view of a card-shaped magnetic recording medium which is an example of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1 and schematically illustrates a cross-sectional state in order to facilitate understanding of the present invention.

FIG. 3 is a cross-sectional view showing a state in which magnetic information of the same pattern is recorded on a magnetic recording unit having a two-layer configuration (note that hatching indicating a cross section is omitted to clearly indicate the state of magnetization). .

FIG. 4 is a cross-sectional view showing a state in which magnetic information of a pattern whose magnetization is reversed is recorded on a magnetic recording unit having a two-layer structure (note that hatching indicating a cross section is omitted to clearly indicate a state of magnetization; is there).

FIG. 5 shows a hard magnetic layer 2 as an original magnetic information source for magnetic transfer.
FIG. 2 is a cross-sectional view showing a state written in No. 1 (note that hatching indicating a cross section is omitted in order to clearly indicate a state of magnetization).

FIG. 6 is a cross-sectional view showing a state in which magnetic information written in the hard magnetic layer 21 has been erased from the state shown in FIG. 4 (note that hatching indicating a cross section is omitted in order to clearly indicate a state of magnetization). ).

7 is a cross-sectional view showing a state in which magnetic information written in the hard magnetic layer 21 is partially erased from the state of FIG. 4 (note that hatching indicating a cross section is omitted in order to clearly indicate a state of magnetization; Is).

8 is a cross-sectional view showing a state in which magnetic information written in the hard magnetic layer 21 has been erased from the state shown in FIG. 3 (note that hatching indicating a cross section is omitted in order to clearly indicate a state of magnetization). ).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Substrate 20 ... Magnetic recording part 21 ... Hard magnetic layer 25 ... Low Curie point / high coercive force magnetic layer 40 ... Concealment layer

Claims (7)

[Claims] 1. A magnetic recording medium comprising: a substrate; and a magnetic recording portion formed on the substrate, wherein the magnetic recording portion includes at least a hard magnetic layer, a magnetic material having a Curie point Tc of 200 ° C. or less. It has a two-layer laminate of a low Curie point and high coercive force magnetic layer containing powder, and the same pattern of magnetic information is recorded on the hard magnetic layer and the low Curie point and high coercive force magnetic layer. Magnetic recording medium. 2. The same pattern of magnetic information is simultaneously written on the low Curie point / high coercivity magnetic layer and the hard magnetic layer while heating the low Curie point / high coercivity magnetic layer to a temperature exceeding the Curie point Tc. 2. The magnetic recording medium according to claim 1, comprising: 3. A magnetic recording medium comprising: a substrate; and a magnetic recording portion formed on the substrate, wherein the magnetic recording portion includes at least a hard magnetic layer, a magnetic material having a Curie point Tc of 200 ° C. or less. It has a two-layer laminate of a low Curie point and high coercive force magnetic layer containing powder, and the hard magnetic layer and the low Curie point and high coercive force magnetic layer record magnetic information of patterns whose magnetizations are reversed with respect to each other. Characteristic magnetic recording medium. 4. Writing magnetic information on the hard magnetic layer in advance, and then heating the low Curie point / high coercive force magnetic layer to a temperature exceeding the Curie point Tc.
4. The magnetic recording medium according to claim 3, wherein magnetic information written on the hard magnetic layer is transferred to the low Curie point / high coercivity magnetic layer. 5. A method for reading magnetic information recorded on a magnetic recording medium according to claim 1, wherein the method comprises the steps of: The magnetic information is read in the erased area after scanning the magnetic head to read the initially set magnetic information and then erasing at least a part of the magnetic information written in the hard magnetic layer. A method for reading magnetic information, comprising: comparing the first magnetic information with the first magnetic information read before erasing. 6. A method for reading magnetic information recorded on a magnetic recording medium according to claim 1, wherein the method comprises the steps of: The magnetic head is scanned above, and a predetermined portion of the magnetic information written in the hard magnetic layer is erased from the magnetic information set first, and thereafter, the remaining portion that has not been erased is set as an unerased area. A method for reading magnetic information, characterized by recognition. 7. A method according to claim 1, wherein a predetermined portion of the magnetic information written in said hard magnetic layer is erased in accordance with the used amount, and thereafter, the remaining used amount is determined from a remaining unerased area which has not been erased. 6. The method for reading magnetic information according to item 6.