JPH10143847A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the forgery of recording information and to improve a security characteristic by constituting a magnetic recording medium successively laminated with a hard magnetic layer, a soft magnetic layer and a concealing layer on a substrate and arraying plural rugged parts as magnetic information at the boundary between the hard magnetic layer and the soft magnetic layer along the scanning direction of a magnetic head. SOLUTION: A magnetic recording section 20 comprises a two-layered laminate formed by laminating the hard magnetic layer 21 and the soft magnetic layer 25 successively from the substrate 10 side. The plural rugged parts R are arrayed as the magnetic information at the boundary of the two-layered laminate along the scanning direction of the magnetic head. The plural rugged parts R are formed by partially removing the surface of the hard magnetic layer 21 first formed to a uniform thickness on the substrate 10. These parts are embedded by the material for forming the soft magnetic layer 25 thereon. The magnetic recording medium is provided with the rugged parts R as the magnetic information fixed at the boundary between the hard magnetic layer 21 and the soft magnetic layer 25, by which the direction of the bias currents for reproduction is changed. The discrimination of the authenticity of the magnetic recording information is made possible by output check of the signals of levels varying in two ways.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium represented by a magnetic card such as a prepaid card having magnetic information formed for preventing forgery.

[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. It is another object of the present invention to make it difficult to externally recognize a recording information pattern.

[0010]

In order to achieve the above object, the present invention provides a magnetic recording medium comprising a substrate, on which a hard magnetic layer, a soft magnetic layer, and a concealing layer are sequentially laminated, At the interface between the hard magnetic layer and the soft magnetic layer, a plurality of uneven portions as magnetic information are arranged along the scanning direction of the magnetic head, and the plurality of uneven portions as the magnetic information are
The hard magnetic layer formed on the substrate is partially physically removed.

The concave portions of the concave and convex portions are configured to have a plurality of types having the same depth and different lateral widths which are widths in the scanning direction of the magnetic head.

The projections of the projections and depressions are configured to have a plurality of types having the same height but different widths, which are widths in the scanning direction of the magnetic head.

The physical removal of the magnetic layer performed to form the plurality of uneven portions as the magnetic information is performed by irradiating a laser beam.

[0014]

Embodiments of the present invention will be described below in detail. FIGS. 1 to 4 show drawings for explaining an embodiment of the present invention.
FIG. 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 in FIG. 1. FIG. 3 schematically shows an example of data format settings, showing the correspondence between the concavo-convex pattern and the magnetic reproduction waveform, and FIG. 4 shows the correspondence between the concavo-convex pattern and the magnetic reproduction waveform shown in FIG. FIG.

As shown in FIGS. 1 and 2, the magnetic recording medium 1 of the present invention is formed by sequentially forming a hard magnetic layer 21, a soft magnetic layer 25, and a concealing layer 30 on a substrate 10. . In the present invention, the hard magnetic layer 21 and the soft magnetic layer 25
Thus, the magnetic recording section 20 is formed.

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.

As shown in FIG. 2, the magnetic recording section 20 is composed of a two-layer laminate in which a hard magnetic layer 21 and a soft magnetic layer 25 are sequentially laminated from the substrate 10 side. And 2
At the interface of the layered structure, a plurality of uneven portions R as magnetic information are arranged along the scanning direction of the magnetic head as shown in the figure. The plurality of uneven portions R have a predetermined length in the depth direction of the paper surface of FIG. 2 (this can be easily understood from FIG. 1). It can be said that the structure is adopted.

The plurality of concavo-convex portions R are formed by partially physically removing the surface of the hard magnetic layer 21 formed first on the substrate 10 to have a uniform thickness, that is, the plurality of concavities 21a to 21a.
is formed as the remainder by removing e.
The soft magnetic layer 25 is formed on the hard magnetic layer 21 having the plurality of irregularities R thus formed. At this time, the concave portions of the hard magnetic layer 21 are buried with the material for forming the soft magnetic layer 25.

When the hard magnetic layer 21 is formed by applying a so-called magnetic coating material, the hard magnetic layer 21 may be 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 .

The resin binder (or ink vehicle) in which the hard magnetic powder is dispersed includes butyral resin, vinyl chloride / vinyl acetate copolymer resin, urethane resin, polyester resin, cellulose resin, acrylic resin, styrene / maleic resin. 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.

The hard magnetic layer 21 is not limited to the above-described coating method, but may be formed by using the above-described magnetic material itself by a vacuum deposition method, a sputtering method, a plating method, or the like. Details of these specific manufacturing methods will be described later.

The soft magnetic layer 25 is formed directly on the hard magnetic layer 21 as described above. Soft magnetic layer 2
5 is a magnetic powder exhibiting soft magnetism (hereinafter, referred to as a hard magnetic layer 21) as a constituent material of the soft magnetic layer 25 when the hard magnetic layer 21 is formed by a method of applying a so-called magnetic paint. Simply referred to as “soft magnetic powder”) and a resin binder. As a material of the soft magnetic powder, Al,
Magnetic alloy materials composed of Si, Fe, etc., metal high permeability materials such as Permalloy, Sendust, Fe, ferrites such as Mn-Zn ferrite, Co-Zn ferrite, Ni-Zn ferrite, and metal amorphous materials can be given. . The resin binder and other additional components are as described for the hard magnetic layer 21. Soft magnetic layer 25
Can be formed by a vacuum evaporation method, a sputtering method, a plating method, or the like using the above magnetic material itself.

The magnetization direction of the soft magnetic layer 25 is reversed by the magnetic field generated in the read magnetic head to which the reproducing bias current is applied. The hard magnetic layer 21 is formed by the generated magnetic field. , Whose magnetization direction does not reverse. Generally, in order to reverse the magnetization direction of the magnetic layer, it is necessary to apply an external magnetic field that is about three times the coercive force (coercive force) of the magnetic layer. Therefore, the coercive force of the soft magnetic layer 25 in the present invention is smaller than the coercive force of the hard magnetic layer 21. For example, as the bias magnetic field, 30
For a magnetic head that generates a magnetic field of [Oe] strength,
A magnetic layer having a coercive force of 10 [Oe] or less as the soft magnetic layer 25,
As the hard magnetic layer 21, a magnetic layer having a coercive force of 100 [Oe] or more is preferable. In the present invention, at least two or more types of convex portions of the concave and convex portions R of the hard magnetic layer 21 forming the magnetic recording portion 20 have the same height and different widths (widths in the scanning direction of the magnetic head). The recesses 21a to 21e of the concavo-convex portion R forming the magnetic recording portion 20 have the same depth and have at least different widths (widths in the scanning direction of the magnetic head). It is configured with two or more types of width. This is for discriminating the difference between the read output waveforms into digital signal values of "0" and "1". In the former case, the digital signals of "0" and "1" are mainly detected from the difference in the width of the convex portion of the concave / convex portion R.
To 21e may be the same or different from each other. In the latter case, the digital signals of 0 and 1 are mainly detected from the difference in the width of the concave portions 21a to 21e. Good. Alternatively, both the above and the above may be combined for detection (FM
Record).

Thus, the hard magnetic layer 21 and the soft magnetic layer 2
By providing the uneven portion R as fixed magnetic information at the interface with 5, the same signal and signals having different output levels can be obtained. That is, in the magnetic recording medium of the present invention, when reading magnetic information, the obtained output level changes depending on the direction of the bias current flowing through the magnetic head. Accordingly, at least two times of signal reading are performed while applying a reproduction bias to the magnetic head, and when the direction of the reproduction bias current at the time of performing the first signal reading and the second signal reading is reversed, mutual reading is performed. The output level changes. This makes it easy to determine whether the pre-recorded fixed information has been tampered with. The specific operation will be described in detail with reference to FIG. It is assumed that the left edge side of the hard magnetic layer 21 in the drawing is an S pole and the right edge side is an N pole. Since the hard magnetic layer 21 shows hard magnetism, the polarity does not change due to the reproduction bias current of the magnetic head. On the other hand, since the soft magnetic layer 25 shows soft magnetism, the polarity changes according to the reproducing bias current of the magnetic head. Then, 1) consider the case where the left edge side of the soft magnetic layer 25 becomes the N pole and the right edge side becomes the S pole, respectively, due to the reproduction bias current. In this case, the left edge side of the soft magnetic layer 25 and the right edge side of the hard magnetic layer 21 correspond to the same position, and the right edge side of the soft magnetic layer 25 and the left edge side of the hard magnetic layer 21 correspond to the same position. .

Therefore, if attention is paid to the left edge side of the soft magnetic layer 25 in H shown in FIG.
5 and the hard magnetic layer 21 both have N poles, and when the reproduction output is E1, E1 is [Br (hard) + Bs (sof
t)]. Here, Br (ha
rd) is the residual magnetic flux density of the portion b of the hard magnetic layer 21, Bs
(soft) indicates the saturation magnetic flux density of the portion a of the soft magnetic layer 25.

On the other hand, 2) consider the case where the direction of the reproduction bias current is changed and the right edge side of the soft magnetic layer 25 becomes the N pole and the left edge side becomes the S pole, respectively, contrary to the above 1). In this case, similarly to the above 1), when attention is paid to the left edge side of the soft magnetic layer 25 in H shown in FIG.
Pole and the hard magnetic layer 21 are N-pole, and the reproduction output is E2
Then, E2 becomes [| Br (hard) −Bs (soft) |].
Is established.

That is, in the magnetic recording medium of the present invention, the obtained magnetic output is 2 depending on the direction of the reproducing bias current.
Appear at street level. This is a feature unique to the magnetic recording medium of the present invention. By confirming these two levels, the authenticity of the card can be determined, and the falsified card can be eliminated. The reversal of the reproducing bias current of the magnetic head can be realized by a slight change in the circuit, and there is no problem in manufacturing a card reader for performing the operation of the magnetic recording medium of the present invention.

Next, an example of setting the data format of the uneven portion R forming the magnetic recording section 20 will be described with reference to FIG. 3, and the reproduced output corresponding to the actual uneven portion R will be described with reference to FIG. A specific example of the changing aspect will be described. As shown in FIG. 3, the data of the uneven pattern shown in the upper part is "1", and the data of the uneven pattern shown in the lower part is "0". The magnetic reproduction waveform has peaks in the boundary regions corresponding to the uneven shapes, respectively, and is displayed as shown in the figure.

FIG. 4 (a) shows the same drawing as FIG. 2, and FIGS. 4 (b) and 4 (c) show the concave and convex portions as the fixed magnetic information shown in FIG. 4 (a). R is a magnetic reproduction waveform when bias reading is performed by a magnetic head. 4B and 4C are different from each other in the direction of the bias current when performing the bias reading, and FIG. 4B shows a case where a high output level E1 is obtained (for example, indicated by a dotted line). FIG. 4C shows a case where a low output level E2 is obtained (for example, a magnetic pole at the boundary H indicated by a dotted line is a combination of N / S).

As shown in FIG. 4A, the upper surface of the two-layer laminate of the hard magnetic layer 21 and the soft magnetic layer 25 of the present invention (the upper surface of the soft magnetic layer 25 in the drawing) is attached to another layer. An uneven portion P may be formed as magnetic information. However, in this case, as shown in FIGS. 4B and 4C, the polarity changes by changing the direction of the bias current and the phase of the waveform is reversed, but the output levels E3 and E4 do not change. The relationship between the output levels is E2 <(E3, E4) <E1. The data of "0" and "1" are shown in FIG.
As shown below.

With such a layer structure of the present invention, by changing the direction of the reproduction bias current, the contents of the written information can be maintained without changing the fixed magnetic information which cannot be rewritten. Reproduction outputs of two or more levels can be obtained. Since such a method cannot be imitated by a magnetic method, a magnetic recording medium that is resistant to alteration and has high security can be obtained.

Each lateral width of the concave and convex portions R as fixed magnetic information (width of concave and convex portions in the scanning direction of the magnetic head)
Is usually about 30 μm to 1 mm. The height and depth of the uneven portion R are usually 2 to 30 μm, preferably 5 to 20 μm according to coating by printing, and 100 to 1000 ° according to a vacuum evaporation method, a sputtering method, and a plating method. , Preferably 400 to 600 °.

An uneven portion R as fixed magnetic information is provided on a two-layer laminate (magnetic recording portion 20) provided at the interface between the hard magnetic layer 21 and the soft magnetic layer 25, and the pattern of the recorded information is recognized. A concealing layer 30 is formed to make it difficult. This concealing layer 30 also contributes to improvement in security.

The concealing layer 30 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 Add titanium oxide, alumina powder, micro silica, etc., and further, if necessary, plasticizer, stabilizer, wax, grease,
After adding a drying agent, a drying aid, a curing agent, a thickening agent, and a dispersing agent, knead well with a solvent or diluent, and then use a coloring paint or ink. It is formed by a coating method or a printing method such as an offset method or an offset method.

On such a concealing layer 30, a protective layer for further enhancing the protection and decoration effect may be provided.

Next, a specific method of manufacturing the above-described magnetic recording medium 1 of the present invention will be described with reference to FIG.

First, a substrate 10 on a sheet is prepared, and a hard magnetic layer 21 is formed on the substrate 10. The hard magnetic layer 21 may be formed by a known coating method such as a silk screen printing method, a gravure method, a roll method, a knife edge method or the like, or a magnetic material prepared in advance as described above. It may be formed by a vacuum deposition method, a sputtering method, a plating method, or the like.

Such a hard magnetic layer 21 may be formed on the entire surface of the substrate 10, but generally, in consideration of economy,
For example, only the parts necessary to make the magnetic recording unit 20 include
It is formed in a stripe shape. Of course, the hard magnetic layer 21
Is required to be formed to a uniform thickness, but if the above-mentioned known continuous coating method is used, a sufficient uniform thickness can be obtained.

Next, as shown in FIG. 2, the surface of a predetermined portion of the hard magnetic layer 21 formed to have a uniform thickness is partially physically removed so that a plurality of concave portions 21a to 21e (substrate 1) are formed.
(Which may or may not reach 0), and as a result, a plurality of uneven portions having a predetermined pattern are formed.

The method of physically removing the hard magnetic layer 21 partially includes, for example, a method of irradiating a laser beam to a position corresponding to the concave portions 21a to 21e, a method of irradiating an electron beam,
Destruction by electric discharge, routing (engraving) processing, and the like can be given.

When a laser beam is used, the type, laser wavelength, laser power, etc., of the laser to be used are determined in consideration of the physical properties of the hard magnetic layer 21 that is partially physically removed, the line width to be removed, and the like. What is necessary is just to set suitably.

As a gas laser, a He-Ne laser, a He-Cd laser, an argon laser (0.48
Rare gas ion laser such as 8 μm continuous oscillation, 0.1 to 20 W); carbon dioxide laser (10.6 μm continuous oscillation, 1
W to 10 kW); a metal vapor laser or the like can be used. As a solid laser, a ruby laser (0.6943 μm pulse oscillation, 10 to 1000 J),
Nd glass laser (1.06 μm pulse oscillation, 10 to 10
1000J), pulsed solid-state laser such as Nd: YAG laser; or ruby laser, Nd glass laser, Nd: YAG laser (continuous oscillation of 1.06 μm,
1 to 200 W), and a continuous excitation solid-state laser such as an Nd: YAlO ₃ laser can be used. As the liquid laser, a dye laser, a Raman laser, a chelate laser, an Nd ³⁺ liquid laser or the like can be used, and as the semiconductor laser, a GaAs diode laser or the like can be used.

Among them, a CO ₂ gas laser having a wavelength of 10.6 μm (output: 0.5 W to 20 W), an Ar gas laser having a wavelength of 0.488 μm (or 0.5145 μm) (output: 0.5 W to 20 W), 1.06 μm
Nd: YAG laser (output: 0.5 W to 20 W) is a preferred example. If the output of the laser is too large, damage to the substrate due to high temperatures or thermal shrinkage of the binder resin that constitutes the magnetic layer will result in poor pattern accuracy, while if the output is too low, sufficient pattern deletion will not occur. Can not.

The soft magnetic layer 25 is formed on the hard magnetic layer 21 in which the concave portions 21a to 21e are formed as described above. The formation of the soft magnetic layer 25 may be performed by a known coating method such as a silk screen printing method, a gravure method, a roll method, a knife edge method, or the like, using a magnetic paint prepared in advance similarly to the hard magnetic layer 21. The material itself may be formed by a vacuum evaporation method, a sputtering method, a plating method, or the like. When the soft magnetic layer 25 is formed, the recesses 21 a to 21 e formed in the hard magnetic layer 21 are completely buried with the material of the soft magnetic layer 25. As a result, the magnetic recording section 20 having the uneven portion R as the fixed magnetic information of the present invention is formed.

Further, if necessary, an uneven portion P may be formed on the surface of the soft magnetic layer 25 as other magnetic information as shown in the figure. This type does not change the output level by changing the direction of the bias current, but can be used as, for example, magnetic information similar to an ID number.

On such a magnetic recording portion 20, a concealing layer 30 is formed for the purpose of concealing the magnetic recording portion 20 and making the magnetic recording portion 20 inconspicuous from the outside. in this case,
It is necessary to appropriately adjust the method of forming the coating film and the thickness of the coating film so that the smoothness of the coating film surface can be ensured.

In the method of reading magnetic information recorded on a magnetic recording medium according to the present invention, a signal is read at least twice while applying a reproducing bias to a magnetic head.
The first signal reading and the second signal reading are performed by reversing the direction of the reproduction bias current.
Whether the information is true or false can be determined based on whether two types of waveforms having the same data and different output levels are obtained. Although the schematic configuration of the read head used in the present invention has already been described above, the configuration will be additionally described. The read head, at the gap,
A bias coil and a reading coil are provided. When reading the fixed information, a fixed signal (fixed information) is applied while applying a constant bias current to the bias coil of the head to generate a bias magnetic field from the gap.
Is scanned. At this time, since the magnetic resistance changes according to the fixed signal, the magnetic flux linked to the read coil changes, and an output waveform proportional to the change amount of the magnetic flux is generated at both ends of the read coil.

[0048]

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

Example 1 First, a magnetic paint 1 and a magnetic paint 2 having the following compositions were prepared in order to form a two-layer laminate of the hard magnetic layer 21 and the soft magnetic layer 25.

(Magnetic paint 1 for forming hard magnetic layer 21) Hard magnetic powder (Ba ferrite) 70 parts by weight Polyurethane resin 12 parts by weight Toluene 20 parts by weight Methyl ethyl ketone 15 parts by weight Methyl isobutyl Ketone: 15 parts by weight-Isocyanate curing agent: 2 parts by weight (magnetic coating material 2 for forming soft magnetic layer 25)-Soft magnetic powder (Permalloy): 70 parts by weight-Vinyl chloride-vinyl acetate copolymer resin ... 4 Parts by weight ・ Polyurethane resin ... 4 parts by weight ・ Organic benite ... 0.4 parts by weight ・ Organic solvent (isophorone / butyl carbitol acetate = 2/1) ... 21.6 parts by weight Next, polyethylene as a substrate (substrate) to be printed Prepare a card made of terephthalate (thickness 250 μm) and strike it on this card by silk screen printing. The magnetic paint 1 is applied in a lip shape, and then left at room temperature to dry the magnetic paint 1. The applied thickness is 10 μm, the applied width is 7 mm,
A hard magnetic layer 21 having a coating length of 85 mm was formed.

Next, the surface of the hard magnetic layer 21 is partially physically removed in a direction perpendicular to the longitudinal direction of the magnetic stripe using Nd: YAG laser light having a wavelength λ = 1.06 nm and an output of 5 W. Two types of concave portions having a line width of 85 μm and 170 μm (the depth was the same at 5 μm) were formed in a predetermined pattern. On the hard magnetic layer 21 thus processed, the magnetic paint 2 is applied by a silk screen printing method, and then left at room temperature to dry the magnetic paint 2 to a coating thickness of 10 μm.
The soft magnetic layer 25 having a thickness of m (the thickness at the place where the uneven portion is not formed) was formed. As a result, the uneven portion R of the fixed signal (fixed information) intended by the present invention was produced.

Next, at a predetermined position on the surface of the soft magnetic layer 25, an uneven portion P was formed as other magnetic information. Uneven part P
Was made with a size similar to the above-mentioned uneven portion R, and care was taken so that the mutual information did not overlap on the same track.

On the soft magnetic layer 25, a concealing layer ink composition having the following composition was further applied to a thickness of 3 μm by a silk screen method to form a concealing layer 30. A medium sample 1 was produced.

(Hidden layer ink composition) Aluminum powder 20 parts by weight Polyurethane resin 18 parts by weight Cyclohexanone 31 parts by weight Toluene 31 parts by weight Before reading operation, opposed magnets in the longitudinal direction of the card. Was used to magnetize the hard magnetic layer 21.

The recorded information on the magnetic recording medium thus manufactured was read twice while applying a reproducing bias to the magnetic head. Of course, the direction of the current of the reproduction bias in the first signal reading and the second signal reading was reversed. When the actually detected magnetic reproduction waveform was examined, as shown in FIG. 4, two types of waveforms having the same data and different output levels (output level E1,
It was confirmed that E2) was obtained.

Further, since the concealing layer 30 is formed, it becomes difficult to externally recognize the pattern of the recorded information.
It was also confirmed that security could be further improved.

[0057]

As described in detail above, the present invention relates to a magnetic recording medium in which a hard magnetic layer, a soft magnetic layer, and a concealing layer are sequentially laminated on a substrate. At the interface with the magnetic layer, a plurality of uneven portions as magnetic information are arranged along the scanning direction of the magnetic head, and the plurality of uneven portions as the magnetic information are hard magnetic layers formed on the substrate. The layer is formed by partially physically removing the layer.

Therefore, it is possible to read the signal at least twice while applying a reproducing bias to the magnetic head, and to reverse the direction of the reproducing bias current when performing the first signal reading and the second signal reading. Thus, two types of waveforms having the same data but different output levels can be obtained.
By confirming the change in the output level in advance, the authenticity of the information can be more reliably determined than before, and the forgery of the card can be prevented. Further, since the concealing layer 30 is formed, it becomes difficult to recognize the pattern of the recorded information from the outside, and the security is further improved.

[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 diagram showing an example of a data format setting.

FIG. 4 is a diagram showing a correspondence between the concavo-convex pattern shown in FIG. 2 and a magnetic reproduction waveform.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Substrate 20 ... Magnetic recording part 30 ... Concealment layer

Claims (4)

[Claims] 1. A magnetic recording medium in which a hard magnetic layer, a soft magnetic layer, and a concealment layer are sequentially laminated on a substrate, wherein an interface between the hard magnetic layer and the soft magnetic layer has magnetic information as magnetic information. A plurality of uneven portions are arranged along the scanning direction of the magnetic head, and the plurality of uneven portions as the magnetic information are formed by partially physically removing a hard magnetic layer formed on the substrate. A magnetic recording medium characterized by being formed. 2. The magnetic recording medium according to claim 1, wherein the concave portions of the concave and convex portions include a plurality of types having the same depth and different lateral widths, which are widths in the scanning direction of the magnetic head. . 3. The magnetic recording according to claim 1, wherein the projections of the projections and depressions include a plurality of types having the same height but different widths, which are widths in the scanning direction of the magnetic head. Medium. 4. The method according to claim 1, wherein the physical removal of the magnetic layer performed to form the plurality of uneven portions as the magnetic information is performed by irradiating a laser beam. The magnetic recording medium according to any one of the above.