JP3335690B2 - Recording method of magnetic recording medium - Google Patents

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 having a magnetic layer made of a plurality of magnetic materials having different magnetic properties on a substrate.

[0002]

2. Description of the Related Art Magnetic recording media in which a magnetic layer is provided on the surface of a base such as plastic are known as credit cards, cash cards, ID cards, tickets, commuter passes, and the like.
It is widely used as prepaid cards, gift certificates, magnetic tapes, and the like. Such a magnetic recording medium has an advantage that its recording density is high and recorded information cannot be easily read from the outside.

[0003]

On the other hand, in recent years, the problem of forgery and falsification has been highlighted as a major social problem due to the convenience of rewriting and erasing information recorded on a magnetic recording medium. For this reason, much research has been done on means for preventing forgery and falsification of magnetically recorded information, but at present, a simple and effective method for preventing forgery and falsification of magnetically recorded information has not yet been established. .

Accordingly, an object of the present invention is to provide a recording method of a magnetic recording medium and a reproducing method of the magnetic recording medium which can solve the problems of the prior art and can effectively prevent forgery or falsification of the magnetic recording medium. That is.

[0005]

In order to achieve the above object, the present invention provides a magnetic material A having a magnetic property having a Curie point of Tc on a substrate, a magnetic material having a higher Curie point and a lower Curie point than the magnetic material. A method for recording a magnetic recording medium having a magnetic layer containing a magnetic material B having magnetic properties of coercive force,
To heat the magnetic layer to a temperature below Tc
The saturation write current between the magnetic material A and the magnetic material B
And the saturation write current
The magnetic material A and the magnetic material
B is characterized in that magnetic recording is performed simultaneously . Below,
A magnetic material having a magnetic property whose T
It may be a magnetic material having a Lie point and a high coercive force.

[0006]

[0007]

[0008]

[0009]

[0010]

[0011]

[0012]

The magnetic recording on the magnetic material having a high coercive force is carried out in a state where the coercive force is lowered by heating to near the Curie point. At the same time, magnetic recording is performed on the low coercivity magnetic material. The magnetic output obtained when reading the magnetic recording in this state is:
It is the sum of the output obtained from the high coercivity magnetic material and the output obtained from the low coercivity magnetic material.

At room temperature, it is difficult to rewrite magnetic information in a high coercivity magnetic material, and only magnetic information in a low coercivity magnetic material can be rewritten. Even if new information is written to falsify and forge magnetic information, only the information in the low coercivity magnetic material is rewritten, and the information newly rewritten in the low coercivity magnetic material and the normal information recorded in the high coercivity magnetic material The information cannot be read, and the forgery can be determined.

Even if recording on a magnetic material with a high coercive force becomes possible, a higher coercive force generally requires a higher recording current for magnetic recording. At this time, the output of the low-coercivity magnetic material decreases due to its saturation characteristic when a recording current higher than a value at which the output is saturated is applied.
Reading becomes impossible, and a forgery prevention effect is obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a magnetic recording medium according to the present invention will be described below with reference to the drawings. A first embodiment of the present invention will be described with reference to FIG. In FIG. 1, a magnetic recording medium 1 has a sheet-like base 2 made of paper, plastic, or the like, a first magnetic layer 3 provided on the base 2, and a second magnetic layer 3 provided on the first magnetic layer 3. And a layer 4.

The first magnetic layer 3 and the second magnetic layer 4 form one laminated magnetic recording layer. These unit magnetic layers 3 and 4 are made of magnetic materials having different Curie points and coercive forces from each other, and the magnetic material forming the upper second magnetic layer 4 has a higher Curie point and a lower coercive force. Further, the magnetic recording layer is provided entirely or partially on the surface of the base 2.

FIG. 2 shows another embodiment of the magnetic recording medium according to the present invention. In FIG. 2, a magnetic recording medium 1 includes a base 2
On top, the second magnetic layer 4 and the first magnetic layer 3 are stacked in this order. That is, the magnetic recording medium shown in FIG. 2 is the same as the magnetic recording medium shown in FIG. 1 except that the order of lamination of the first magnetic layer 3 and the second magnetic layer 4 is reversed. Whether the position of the first magnetic layer 3 having a high coercive force and a low Curie point is one of the examples shown in FIGS. 1 and 2 can be selected in consideration of the following effects.

First, in the example shown in FIG.
Since the magnetic layer 4 conceals the lower first magnetic layer 3, the forger becomes less likely to notice the presence of the first magnetic layer 3 made of a magnetic material having a high coercive force and a low Curie point. Further, since the second magnetic layer 4 made of a magnetic material having a low coercive force is provided on the upper layer,
Trouble due to magnetic transfer hardly occurs. Further, the average particle diameter of the magnetic material forming the second magnetic layer 4 is set to 0.1 μm.
m or less, the transmittance of infrared rays in the second magnetic layer 4 is improved, and when the heating means using infrared rays is used as described later, the first magnetic layer 3 is concealed despite being hidden. There is an effect that only one magnetic layer 3 can be selectively heated.

In the example shown in FIG. 2, since the first magnetic layer 3 is an upper layer, the first magnetic layer, which is a high coercive force layer, is formed by a general heating means such as heating by heating rolls or heating by light. 3 can be easily heated directly. Further, when heated by the heating means, the heat rise distribution is concentrated on the magnetic layer having a high coercive force and a low Curie point, which is the upper first magnetic layer 3, and the low coercive force, which is the second magnetic layer 4 which is the lower layer. Since the heat diffusion to the magnetic layer having a high Curie point can be reduced, the Curie point of the second magnetic layer 4 can be relatively low, and damage due to heat is small. Further, at the time of magnetic recording, since the layer far from the magnetic head is a magnetic layer having a low coercive force, the magnetic field strength (write current value) can be reduced. Furthermore, since the upper layer is a magnetic layer having a high coercive force, there is an effect that it is difficult for a forger to notice the lower second magnetic layer 4.

The magnetic layers 3 and 4 having such a configuration are heated at a temperature lower than the Curie point Tc of the second magnetic layer 4 having a low Curie point Tc so that the first magnetic layer 3 and the second magnetic layer 4, the saturation write current value becomes substantially the same, or the saturation write current value approaches, so that a specific write current set value (for example, 1.5 to 2.0 of the saturation current value) of the magnetic material having a low coercive force is obtained. It is characterized in that the saturation current value of a magnetic material having a high coercive force is smaller than that of a magnetic material having a higher coercive force.

That is, the Curie point T of the second magnetic layer 4
c at a lower temperature than the first magnetic layer having a high coercive force.
By lowering the coercive force of the magnetic layer 3, the saturation write current value can be made substantially the same as or close to the saturation write current value of the second magnetic layer 4. Thereby, a specific write current set value (for example, 1.5 to less than the saturation current value) of the magnetic material having a low coercive force.
2.0 times), the saturation current value of the magnetic material having a higher coercive force can be made smaller. At this time, if the heating temperature is too low, the saturation write current value of the first magnetic layer 3, which is a high coercivity magnetic layer, does not become the same level as the saturation write current value of the second magnetic layer 4, or the low coercivity At the write current value when writing to the layer, the saturation write of the high coercive force magnetic layer cannot be performed, so that the lower limit of the heating condition is set to 1 at the low Curie point Tc.
It is preferable to set the temperature to about / 2. When the Curie points of the two magnetic layers 3 and 4 are close to each other, the coercive force of the second magnetic layer 4 which is a low coercive force magnetic layer also decreases. For this reason, it is preferable to set the difference between the Curie points of the two magnetic layers 3 and 4 to 100 ° C. or more to prevent the coercive force of the low coercive force magnetic layer from decreasing. Further, in order to prevent the magnetic recording on the first magnetic layer 3 and the magnetic recording on the second magnetic layer 4 from being influenced by each other, it is preferable to set the difference in coercive force between the two magnetic layers 3 and 4 to be twice or more.

In the above example, the magnetic layer has a two-layer structure of the first magnetic layer 3 and the second magnetic layer 4, but may have a laminated structure of three or more layers. Further, the magnetic layer may be made of three or more magnetic materials having different coercive forces and Curie points. As a magnetic layer having a three-layer structure, for example, (high coercive force / low Curie point) / (low coercive force / high Curie point) /
By setting (high coercive force / low Curie point), the write waveforms of the high coercive force layer and the low coercive force layer can be made more identical. Further, the coercive force is set to three levels, and further magnetic data is written to the intermediate coercive force layer, or the Curie point is set to 3 points.
By setting the heating temperature in two stages, a more sophisticated recording / reproducing system can be obtained.

As described above, the magnetic layer of the magnetic recording medium 1 of the present invention has a lower than the Curie point Tc because the first magnetic layer 3 and the second magnetic layer 4 have the above-described characteristics. By heating at a low temperature, particularly a temperature range of (Tc-1 / 2.Tc), to make the saturation write current values of both magnetic layers substantially the same or close to each other, a specific magnetic material having a low coercive force can be specified. The write current setting value (for example, the saturation current value of 1.
(5 to 2.0 times), the saturation current value of the magnetic material having a high coercive force is smaller, thereby enabling the first magnetic layer 3 and the second magnetic layer 4 to be written simultaneously.

However, it is difficult to simultaneously rewrite the magnetic information of the first magnetic layer 3 and the second magnetic layer 4 by a normal magnetic recording device. That is, in FIG. 1, the first magnetic layer 3 is a high coercivity magnetic layer and the second magnetic layer 4 is a low coercivity magnetic layer, so that the second magnetic layer 4 can be rewritten by a normal magnetic recording device. However, the illegally rewritten information of the second magnetic layer 4 and the information recorded on the first magnetic layer 3 are mixed, making it impossible to read out the information and facilitating forgery. Is determined.

When the first magnetic layer 3 can be rewritten by an ordinary magnetic recording apparatus, the saturation write current of the high coercivity magnetic layer is generally large, so that the second magnetic layer 4 which is a low coercivity magnetic layer is used. In this case, a write current higher than the output saturation value is given, the output of the second magnetic layer 4 is reduced, writing becomes insufficient, and simultaneous rewriting of both magnetic layers becomes impossible, and forgery is effectively prevented. Is done.

The saturation write current value includes the recording frequency in the magnetic recording apparatus, the transport speed during writing, the shape of the magnetic head, the coercive force and thickness of the magnetic layer, the filling ratio of the magnetic material, the magnetic layer and the magnetic head. , It is difficult to forge magnetic layers having the same saturation write current value, and it is extremely difficult to find the above-mentioned heating conditions and saturation write current value. For example, a shift of the heating temperature by 5 ° C. causes a variation of 10% or more in the saturation write current value.

FIG. 3 shows another embodiment of the magnetic recording medium according to the present invention. In FIG. 3, the magnetic recording medium 1 is
A mixed magnetic layer 5 is provided on the base 2. The mixed magnetic layer 5 is formed by mixing a plurality of magnetic materials having different Curie points and coercive forces. Also in this case, the same effect as in the case of the multilayer structure can be obtained, and further, since there are few constituent layers, there is an advantage that the distance between the lowermost part of the magnetic layer and the magnetic head can be reduced.

In the present invention, the magnetic layer of the magnetic recording medium has
A light absorbing layer may be provided in order to improve the efficiency of heating by light as described later. The light-absorbing layer can be formed as a resin layer to which a light-absorbing dye such as a cyanine-based, phthalocyanine-based, dithiol-nickel complex-based, quinone-based dye, or carbon black is added. Examples of the resin used include the resins used for forming the above-mentioned colored layer.

FIG. 4 shows an embodiment of a transfer laminate for forming the magnetic recording medium of the present invention. In the transfer laminate, a release layer 6, a second magnetic layer 4, a first magnetic layer 3, and an adhesive layer 7 are stacked in this order on a transfer substrate 2 '.

FIG. 5 shows an embodiment of an adhesive laminate for forming the magnetic recording medium of the present invention. The laminated body to be adhered is composed of the second magnetic layer 4 and the first magnetic layer 3 on the adhered substrate 2 ″.
Are stacked in this order.

Next, the method of manufacturing the magnetic recording medium according to the present invention and the materials used will be described. The magnetic recording medium 1 according to the present invention comprises a magnetic layer 3, 4 or a mixed magnetic layer 5, a coloring layer, a concealing layer, a protective layer,
Alternatively, the adhesive layer can be provided by a printing method or a coating method and formed by a direct method.

If necessary, for example, a protective layer, a coloring layer, a concealing layer, an adhesive layer, and the like are provided on the transfer substrate with a release layer 6 interposed therebetween. Transfer laminate 2 in which a melt adhesive layer 7 is laminated in this order
1. The hot melt adhesive layer of this laminate was
The magnetic recording medium 1 according to the present invention can be formed by a transfer method in which the transfer substrate is adhered onto the surface of the substrate and the transfer substrate is removed by the release layer.

Further, an adhesive laminate 31 in which the magnetic layers 3, 4 or 5 are laminated on the adhesive substrate is prepared, an adhesive layer is provided on the back surface of the laminate, and the substrate is interposed via the adhesive layer. The magnetic recording medium 1 according to the present invention can be formed by a sticking method in which the laminate and the sticking laminate can be integrally bonded.

The substrate 2 has a sheet shape or a plate shape. Examples of the substrate 2 include plastics such as nylon, cellulose diacetate, cellulose triacetate, polystyrene, polyethylene, polypropylene, polyester, polyimide, polycarbonate, copper, and aluminum. Metal, paper, impregnated paper, etc. can be used alone or in combination as a composite. Physical properties required as a base material, strength, rigidity, concealing property, light impermeability, especially when performing magnetic recording with heating, in consideration of heat resistance, a suitable material may be appropriately selected from the above materials. I just need. In addition, the thickness of the base material 2 is about 0.005 to 5 mm.

The magnetic material used for the magnetic layers 3, 4, 5
In particular, as a high coercive force magnetic material with a low Curie point
Is CrO_Two, AO · n ｛(Fe_1-XYCr_XZn_Y)
_TwoO _ThreeＡ, AO · n ｛(Fe_1-XCr_X)_TwoO_Three｝, A
On ・ n ｛(Fe_1-XYZGa _XCr_YAl_Z)
_TwoO_ThreeＡ, AO · n ｛(Fe_1-XAl_X)_TwoO_Three｝, A
On ・ n ｛(Fe_1-XGa_X)_TwoO_ThreeＡ, AO ・ n ｛(F
e_1-XYCr_XGa_Y)_TwoO_Three｝ (A is Sr or Ba
One or two of n = 5 to 6)
Sr ferrite, Ba ferrites, Nd-Fe-B
-Mn, Nd-Fe-B-Mn-Al, Nd-Fe-B
-Mn-Cr, Nd-Fe-B-Mn-Al-Cr, etc.
Nd-Fe-B-based alloys. Forming method and
For this purpose, the magnetic fine particles are each
The dispersion, which is dispersed in the millet vehicle, is gravure
Conventional coating methods such as the roll method, the roll method, and the knife edge method
It can be formed on the base material 2 by the method
Forming by vapor deposition, sputtering, plating, etc.
Can also.

As a magnetic material constituting a magnetic layer having a low coercive force and a high Curie point, 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-Ni, B
a Fine particles of magnetic particles such as a ferrite, Sr ferrite, and CrO ₂ . A magnetic layer can be formed by applying a dispersion obtained by dispersing the above magnetic fine particles in an appropriate resin or ink vehicle according to a known coating method such as a gravure method, a roll method, or a knife edge method. it can. Further, Fe, Fe-Cr, Fe-Co,
It can also be formed using a metal or alloy such as Co-Cr, or an oxide thereof by a vacuum evaporation method, a sputtering method, a plating method, or the like.

The average particle size of the above magnetic material is set to 0.1
When the thickness is not more than μm, the permeability of the magnetic layer to infrared rays is improved, and when the heating means for the magnetic layer described below is infrared rays, the irradiated infrared rays pass through the magnetic layer that does not require heating and are irradiated with the desired magnetic layer. Can be heated.

When the magnetic layers 3, 4 and 5 are formed by a coating method, the thickness of the layers is 1 to 100 μm, preferably 5 to 100 μm.
It is about 20 μ. When the unit magnetic layer is formed by a vacuum deposition method, a sputtering method, or a plating method, the layer thickness is about 100 to 1 μm, and preferably about 500 to 2000 °.

Examples of the resin or ink vehicle in which the magnetic fine particles are dispersed include butyral resin, vinyl chloride / vinyl acetate copolymer resin, urethane resin, polyester resin, cellulose resin, acrylic resin, styrene /
A maleic acid copolymer resin or the like is used, and a rubber-based resin such as a nitrile rubber or a urethane elastomer is added as necessary. In consideration of heat resistance, a resin having a high glass transition temperature (Tg), such as polyamide, polyimide, or polyether sulfone, or Tg by a curing reaction.
Can be used. If necessary, a pigment such as a surfactant, a silane coupling agent, a plasticizer, a wax, a silicone oil, and a garbon is added to the dispersion of the magnetic fine particles dispersed in the resin or the ink vehicle as described above. You may.

When recording is performed by heating to near the Curie point to reduce the coercive force of the high coercive force magnetic material, the coercive force of the low coercive force magnetic material is also reduced. Is preferably at least 100 ° C. as described above.

The difference in coercive force is preferably at least twice as long as it does not affect the magnetic recording on the magnetic materials. In addition, the magnetic layers 3, 4, and 5 are not limited to only one surface of the base 2, and may be provided on each surface of the base 2.

The magnetic recording medium of the present invention may be provided with a colored layer or a picture for providing a concealment / decoration effect on the magnetic layer. Colored layers and patterns are made of cellulose derivatives such as ethylcellulose, cellulose nitrate, ethylhydroxyethylcellulose, cellulose acetate propionate and cellulose acetate, styrene resins such as polystyrene and poly-α-methylstyrene or styrene copolymer resins, and polymethyl methacrylate. , Polyethyl methacrylate, polyethyl acrylate, acrylic resin or methacrylic resin such as polybutyl acrylate alone or copolymerized resin, rosin, rosin modified maleic resin, rosin modified phenolic resin, rosin ester resin such as polymerized rosin, Various pigments are added to binders such as polyvinyl acetate resin, coumarone resin, vinyl toluene resin, vinyl chloride resin, polyester resin, polyurethane resin and butyral resin according to the color to be colored. And, further optionally, plasticizers, stabilizers, wax, grease, drying agents,
After adding a drying aid, a curing agent, a thickener, and a dispersing agent, use a coloring paint or ink that is sufficiently kneaded with a solvent or a diluent, and use a normal gravure method, a roll method, a knife edge method, an offset method. It can be formed at a desired portion by a coating method such as a method or a printing method.

In the magnetic recording medium of the present invention, a protective layer may be provided on the magnetic recording layer and the coloring layer provided as required. The protective layer can be formed by laminating a synthetic resin film, by an extrusion coating method, or by applying a synthetic resin paint. As the synthetic resin for forming the protective layer, those similar to the synthetic resins used for forming the colored layer can be widely used in consideration of the application or the adhesion to other layers. In particular, the use of a thermosetting synthetic resin is advantageous in terms of surface hardness and prevention of contamination, and the use of a paint containing a UV-curable synthetic resin is preferable because curing after application can be performed instantaneously. . Also, the surface can be made releasable by adding silicone or the like to the protective layer.

In the transfer laminate for forming the magnetic recording medium of the present invention, the release layer can also serve as a protective layer. The release layer enhances the releasability of the transfer layer, for example, using a cellulose resin, a polyvinyl butyral resin, an epoxy resin, a phenol resin, a polyester resin, a polyurethane resin, an acrylic resin, a melamine resin, and a mixture of these resins. , As appropriate, a fluororesin,
It is formed by adding release agents such as various waxes and silicones.

The adhesive layer is made of vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, vinyl chloride / propionic acid copolymer, rubber resin, cyanoacrylate resin, cellulose resin, ionomer resin, polyolefin resin. To a binder such as a copolymer, if necessary, after adding a plasticizer, a stabilizer, a curing agent, and the like, use a coating for an adhesive layer that is sufficiently kneaded with a solvent or a diluent, using a gravure method, a roll. It can be formed on a desired portion on the substrate by a coating method such as a method or a knife edge method. In particular, when an adhesive layer is provided on the magnetic layer, it is preferable that a thermoplastic resin be emulsified and applied and dried to form a heat-sealable adhesive layer in order to prevent re-dissolution of the magnetic layer.

Next, the recording method of the magnetic recording medium of the present invention,
The reproduction method will be described. A recording method for a magnetic recording medium according to the present invention is characterized in that magnetic recording is performed while heating the magnetic layer of the magnetic recording medium as described above. That is, by heating the magnetic layer, the saturation write current value of the high coercivity magnetic material constituting the magnetic layer can be substantially the same as or close to the saturation write current value of the low coercivity magnetic material. The saturation current value of the magnetic material having a high coercive force is smaller than a specific write current setting value (for example, 1.5 to 2.0 times the saturation current value) of the magnetic material having a coercive force, and the magnetic layer is formed. Writing is performed on all the magnetic materials at the same time.

More specifically, as shown in FIG.
When the first magnetic layer 3 is a magnetic layer having a high coercive force and a low Curie point, and the second magnetic layer 4 is a magnetic layer having a low coercive force and a high Curie point, when the magnetic layer is heated, a high coercive force is first obtained. At the same time, the coercive force of the first magnetic layer 3 having a low Curie point decreases, and the output saturation characteristic also shifts toward a low write current value, so that the optimum write current region of the first magnetic layer 3 has a low coercive force and high curie. The optimum write current region of the second magnetic layer 4 having a point substantially coincides. The heating conditions in such a state are the heating conditions of the magnetic recording medium recording method of the present invention. As a result, stable writing of the entire magnetic layer becomes possible, the waveform at the time of reproduction is stabilized, and good reproduction with a small fluctuation rate becomes possible.

In the above example, the same magnetic data is written in the first magnetic layer 3 and the second magnetic layer 4 constituting the magnetic layer. However, the recording method of the present invention is not limited to this. The magnetic data written to the first magnetic layer 3 and the magnetic data written to the second magnetic layer 4 may be different. In this case, first, the same magnetic data is written into the first magnetic layer 3 and the second magnetic layer 4 while heating as described above, and then another magnetic data is written at room temperature. Can be rewritten only to By writing different magnetic data in the first magnetic layer 3 and the second magnetic layer 4 in this way, if the two layers of the first magnetic layer 3 and the second magnetic layer 4 are read as they are, Only by obtaining a composite signal of magnetic data, accurate reading cannot be performed, and the forgery prevention effect can be further enhanced.

The above-mentioned heating is preferably performed only on the first magnetic layer 3 having a high coercive force and a low Curie point, and more preferably only on the writing area of the first magnetic layer 3. If the layer has sufficient heat resistance, the entire magnetic recording medium may be heated.

As a means for heating the magnetic recording medium, a heating roller, an infrared lamp, laser heating, heating by a magnetic head, and the like are used. The heating roller preferably has a peripheral surface covered with a soft member such as silicon rubber so as not to damage the surface of the magnetic layer or the protective layer. Further, it is preferable that the roller diameter is set so that the entire heating area can be heated in one round, and that uneven heating caused by the difference between the surface temperature in the first round and the surface temperature in the second round is preferably prevented. For example, when heating over the entire length of a card having a length of 85 mm, one heating roller having a diameter of 25 mm or more can be used, or a heating roller having a plurality of rollers having a diameter of 5 mm or less arranged in the rotation direction can be used. Rollers can also be used. The surface temperature of such a heating roller is 50 to 300 ° C.
And the speed of the heating roller is 10 to 200
mm / sec.

It is desirable that the heating section is as close as possible to the magnetic head, and it is desirable that the heating section reaches the magnetic head before the temperature of the medium drops. In addition, the heating temperature by heating,
When the temperature of the magnetic head itself is different, it is necessary to accurately maintain the temperature increase, the feed rate, the temperature of the magnetic head, and the like so that the medium temperature is always constant during writing.

More specifically, a plurality of heating sections are used, the roll hardness is fixed, the heating time of the medium is made accurate, the transfer belt is made of a heat-resistant Kepler from a rubber belt, or the belt is made a caterpillar type or a chain type. In order to make the transport speed accurate and keep the magnetic head at a constant temperature,
It is also desirable to add cooling means or to perform heating and cooling by a sensor. Of course, a plurality of sensors may be installed in the apparatus, and the detection data may be fed back to the above conditions. Furthermore, radiant heat from the heating section,
A shielding plate or a heat insulating material for blocking conduction heat may be used.

In order to use the heating unit together with an ordinary magnetic recording apparatus, the heating unit may be easily moved and shut off. Of course, usually, if the magnetic layer has a high Curie point, the same device can be used as it is. As the heat source, a method such as resistance heating, induction heating (low frequency, high frequency), and dielectric heating can be used.

The heating by the infrared lamp is, for example, 150
The irradiation can be performed by irradiating a W halogen lamp to a predetermined magnetic recording width by condensing and irradiating the magnetic layer, and arbitrarily heating the magnetic layer in the writing region within a range of 50 to 300 ° C. According to the heating by the infrared lamp, only the magnetic layer can be heated without thermally damaging the diffraction grating layer or the hologram layer. Further, by setting the focal point near the magnetic layer at the time of condensing, the magnetic layer can be heated more efficiently.

Laser heating can be performed using a gas laser device, a solid laser device, a semiconductor laser device, or the like. Among them, a gas laser such as a helium-neon laser, an argon gas laser, and a carbon dioxide gas laser, and a solid laser such as a YAG laser are particularly preferable, and the laser power is about 10 to 1000 W.

Further, in the case of optical heating, a beam is often formed, and it is considered that the cross section is circular and non-uniform in the direction perpendicular to the medium scanning direction. Therefore, the beam is converted into an optical beam using a combination of a cylindrical lens and the like. Depending on the system, the cross section can be made rectangular or slit-shaped, and at the same time a uniform output distribution can be obtained. Further, the above object can be achieved by dividing one beam by a plurality of fibers and arranging them in a line or bundling them in a rectangle.
When optical means is used, it is possible to bring the magnetic head as close as possible with a mirror, a fiber, or the like. Of course, if the substrate is transparent, it can be heated from the substrate side.

The heating by the magnetic head is performed by setting the magnetic head to 5
It can be performed by heating to about 0 to 120 ° C. The magnetic head can be heated by, for example, energizing a nichrome wire wound around a ring head constituting the magnetic head, or heating the magnetic head using an infrared lamp. Of course, the above-described heating methods may be used in combination.

Here, writing to all the magnetic materials constituting the magnetic layer at the same time by heating the magnetic layer is the same as in the above-described example. Lasers, infrared rays, and the like can be used as the optical means as the heating means.

In the method of reproducing a magnetic recording medium of the present invention, a low coercive force layer (second magnetic layer 4) constituting a magnetic layer is used.
Alternatively, there is a method of reading after erasing magnetic data written in the high coercivity layer (first magnetic layer 3).

That is, when different magnetic data is written to the first magnetic layer 3 and the second magnetic layer 4 as described above,
When the two layers of the magnetic layer 3 and the second magnetic layer 4 are read as they are,
Just by obtaining a composite signal of two different magnetic data,
An accurate reading cannot be made.

In the former case, first, the magnetic data of the second magnetic layer 4 having a low coercive force is erased, and thereafter, only the magnetic data of the first magnetic layer 3 having a high coercive force is read.
In the latter case, the magnetic layer is heated to lower the output level of the magnetic data written in the first magnetic layer 3 as much as possible so that the magnetic data of the second magnetic layer 4 having a low coercive force can be accurately obtained. To read. In this case, when the reading of the magnetic data is completed and the heating state is released, the output level of the magnetic data written in the first magnetic layer 3 returns to the original state, and the output level of the first magnetic layer 3 and the second magnetic layer 3 remain unchanged. When the two magnetic layers 4 are read, only a composite signal of two different magnetic data is obtained.

As another example of the reproducing method of the magnetic recording medium of the present invention, the first magnetic layer 3 and the second magnetic layer
When the same magnetic data is written in the magnetic layer 4, if the data is read as it is, the output level is set to a value exceeding the standard value, for example, 200%, and the first magnetic layer is heated. By lowering the output level of the magnetic data written in the layer 3, the standard value of 10
In some cases, reading can be performed at an output level of 0%. According to this reproducing method, for example, when a forger reads the magnetic layer as it is and knows that the output level is 200%, and creates a forged card corresponding to this output level, Is not of a two-layer structure, and when reading is performed according to the reproducing method of the present invention, reading is performed at an output level of 200% exceeding the standard value,
An error occurs.

As another example of the reproducing method of the magnetic recording medium of the present invention, reading is performed while heating the magnetic recording medium under heating conditions different from the heating conditions at the time of recording. In other words, by changing the heating conditions during regeneration,
The reading output level is changed, and the reading standard value can be set as appropriate. For this reason, unless both the heating conditions during recording and the heating conditions during reproduction are known, a forged magnetic recording medium cannot be produced.

Next, the magnetic recording medium of the present invention will be described in more detail with reference to experimental examples. (Experimental Example 1) A paint having the following composition was formed as a first magnetic layer 3 to a thickness of 10 µ on a 188 µ thick polyethylene terephthalate film by a gravure coating method.

Sr ferrite (Hc = 6000 Oe, Tc = 150 ° C.) 36 parts Urethane resin 12 parts Toluene 20 parts Methyl ethyl ketone 15 parts Methyl isobutyl ketone 15 parts Isocyanate-based curing agent 2 parts Next, on the first magnetic layer 3, A coating having the following composition was formed as the second magnetic layer 4 to a thickness of 5 μm by a gravure coating method.

R-Fe ₂ O ₃ (Hc = 300 Oe, Tc = 575 ° C.) 36 parts Urethane resin 12 parts Toluene 20 parts Methyl ethyl ketone 15 parts Methyl isobutyl ketone 15 parts Isocyanate-based curing agent 2 parts Next, the second magnetic layer 4 Was coated by a gravure coating method to form a protective layer having a thickness of 2 μm.

Polyvinyl butyral resin 10 parts Urethane resin 10 parts Tetrafluoroethylene powder 10 parts Ethyl acetate 30 parts Toluene 30 parts Methyl ethyl ketone 30 parts The sheet prepared as above was 86 mm × 54 mm.
Punched into a card of the size of
Magnetic data was recorded at a write current of 80 mA with the saturation write current value of the first magnetic layer 3 and the second magnetic layer 4 set to about 60 mA while heating at 20 ° C., and after cooling, the magnetic data was read. Magnetic data could be read well at the output.

Next, when another magnetic data was recorded at room temperature with a write current of 100 mA on the magnetic recording medium on which the above magnetic data was recorded, and then read, an output of about 700 to 900 mV was obtained. However, two types of magnetic data were mixed, and the magnetic data could not be read.

Further, the produced magnetic recording medium was heated at 70 ° C., and magnetic data was recorded at a write current of 90 mA. When the magnetic recording medium was cooled and read, the read output was about 400 mV, confirming that the recording of magnetic data on the first magnetic layer, which is a high coercivity magnetic recording layer, was insufficient. Was done. (Experimental Example 2) In the same manner as in Experimental Example 1, the first surface of a milk-white polyethylene terephthalate film having a thickness of 188 μm was
Magnetic layer (thickness 15 μm) and second magnetic layer (thickness 10 μm)
Was formed. Next, a coating solution having the following composition was applied on the second magnetic layer to form a protective layer (2 μm in thickness).

(Coating liquid for forming protective layer) Cellulose acetate resin: 5 parts by weight Methanol: 25 parts by weight Methyl ethyl ketone: 45 parts by weight Toluene: 25 parts by weight Methylolated melamine resin: 0.5 parts by weight -Paratoluenesulfonic acid: 0.05 parts by weight The sheet prepared as described above was punched into a card having a size of 86 mm x 54 mm to prepare a magnetic recording card.
When writing and reading were performed on this magnetic recording card in the same manner as in Experimental Example 1, the same results as in Experimental Example 1 were obtained. (Experimental Example 3) Each coating liquid having the following composition was applied to one surface of a milk-white polyethylene terephthalate film having a thickness of 188 µm by a gravure coating method, and a first magnetic layer (15 µm thick) and a second magnetic layer ( (Thickness: 10 μm).

(Coating solution for forming first magnetic layer) Sr ferrite (coercive force = 6000 Oe, Curie point = 140 ° C.): 33 parts by weight Urethane resin: 12 parts by weight Toluene: 20 parts by weight Methyl ethyl ketone 30 parts by weight ・ Isocyanate curing agent 2 parts by weight (coating liquid for forming the second magnetic layer) ・ Ba-ferrite (coercive force = 1700 Oe, Curie point = 450 ° C.) 36 parts by weight ・ Urethane resin 12 parts by weight Parts: toluene: 20 parts by weight; methyl ethyl ketone: 30 parts by weight; isocyanate-based curing agent: 2 parts by weight Next, a coating solution having the following composition is applied on the second magnetic layer to form a protective layer (2 μm in thickness). Formed.

(Coating solution for forming protective layer) Dipentaerythritol hexaacrylate 10 parts by weight Teflon powder 2 parts by weight Isopropyl alcohol 2 parts by weight Methyl ethyl ketone 2 parts by weight Toluene 2 parts by weight or more The sheet prepared as described above was punched into a card having a size of 86 mm x 54 mm to prepare a magnetic recording card.
The magnetic recording card was heated to 100 ° C. with a 300 W helium-cadmium laser to record magnetic data at a write current of 150 mA while setting the saturation write current of the first magnetic layer and the second magnetic layer to about 90 mA. Then, when reading was performed after cooling the magnetic recording medium, about 10
Magnetic data could be read favorably with an output of 00 mV. (Experimental Example 4) A magnetic recording card having a size of 86 mm x 54 mm was prepared in the same manner as in Experimental Example 3.

The magnetic recording card was irradiated with a 100 W carbon dioxide gas laser with an optical fiber, which was spread out so that the entire magnetic layer could be heated, and heated to 100 ° C. to saturate the first magnetic layer and the second magnetic layer. While keeping the value at about 90 mA,
Magnetic data was recorded at a write current of 150 mA. Then, when reading was performed after cooling the magnetic recording medium, magnetic data could be read satisfactorily with an output of about 1000 mV. (Experimental Example 5) Each coating solution having the following composition was applied to one surface of a milk-white polyethylene terephthalate film having a thickness of 188 μm by a gravure coating method to form a magnetic layer (thickness: 1).
5 μm).

(Coating solution for forming magnetic layer) Sr ferrite (coercive force = 6000 Oe, Curie point = 140 ° C.) 20 parts by weight Ba-ferrite (coercive force = 1700 Oe, Curie point = 450 ° C.) 20 parts by weight ・ Urethane resin… 12 parts by weight ・ Toluene… 20 parts by weight ・ Methyl ethyl ketone… 15 parts by weight ・ Isocyanate-based curing agent 2 parts by weight The sheet prepared as above is punched into a card having a size of 86 mm × 54 mm. A magnetic recording card was created.
In the same manner as in Experimental Example 4, 100
When the carbon dioxide laser of W was spread and irradiated with an optical fiber so that the entire magnetic layer could be heated, and heated to 100 ° C., the saturation write current value of the magnetic layer was reduced from 90 mA in the above example to 70 mA, and the write current was 120 mA. Could record magnetic data. That is, in the magnetic recording medium of the present invention prepared in Experimental Example 5, the magnetic layer was a single layer, the process could be simplified, and a low write current value could be achieved. (Experimental Example 6) A magnetic recording card was prepared in the same manner as in Experimental Example 3, except that the coating solution for forming the second magnetic layer was a coating solution having the following composition.

(Coating solution for forming second magnetic layer) Ba-ferrite (finely pulverized and classified, average particle size = 0.1 μm) (coercive force = 600 Oe, Curie point = 450 ° C.) 36 parts by weight -Urethane resin ... 12 parts by weight-Toluene ... 20 parts by weight-Methyl ethyl ketone ... 30 parts by weight-Isocyanate-based curing agent 2 parts by weight
The infrared light was able to directly heat the first magnetic layer by passing through the second magnetic layer. Due to the heating by the infrared rays, the saturation write current value of the first magnetic layer became 70 mA, which is almost the same as the saturation write current value of the second magnetic layer. That is, by using the fine powder magnetic material as the magnetic material constituting the second magnetic layer, the first magnetic layer can be efficiently heated by infrared rays, and unnecessary heat is supplied to the second magnetic layer. Can be prevented. (Experimental example 7) An ultraviolet-curable coating solution having the following composition was applied to one surface of a polyethylene terephthalate film having a thickness of 25 µm by a gravure coating method, and thereafter, the solvent was removed and ultraviolet irradiation was performed using a 120 W ultraviolet lamp. And cured to form a protective layer (2 μm thick).

(Coating liquid for forming protective layer) Dipentaerythritol hexaacrylate 10 parts by weight Teflon powder (softening point = 130 ° C.) 2 parts by weight Isopropyl alcohol 2 parts by weight Methyl ethyl ketone 2 parts by weight Toluene: 2 parts by weight A second magnetic layer was formed on this protective layer using the same coating liquid for forming the first magnetic layer and the second magnetic layer as used in Experimental Example 1. A layer (10 μm in thickness) and a first magnetic layer (15 μm in thickness) were formed in this order. Then, a coating liquid having the following composition is applied onto the magnetic layer to form an adhesive layer (thickness: 3 μm).
m) was formed to prepare a magnetic transfer sheet as a transfer laminate.

(Coating Liquid for Forming Adhesive Layer)-Vinyl chloride / vinyl acetate copolymer ... 20 parts by weight-Acrylic resin ... 10 parts by weight-Ethyl acetate ... 20 parts by weight-Toluene ... 50 parts by weight As described above The magnetic transfer sheet prepared above was slit to a width of 6 mm to form a magnetic transfer tape, and this magnetic transfer tape was used as a vinyl chloride laminated sheet (100 μm transparent vinyl chloride / 56 μm).
0μm milky white vinyl chloride / 100μm transparent vinyl chloride)
And a hot plate is pressed from the magnetic transfer tape side at a temperature of 170 ° C. and a pressure of 50 kg / cm ² , and the polyester film is peeled off. A stripe in which a magnetic layer, a second magnetic layer, and a protective layer were stacked in this order was provided.

When recording and reproduction were performed on the magnetic recording medium thus manufactured in the same manner as in Experimental Example 2, almost the same results as in Experimental Example 2 were obtained. Also, 500
Even when the reading was continuously performed 0 times, there was no change in appearance, and it was confirmed that the device had high durability. (Experimental Example 8) A magnetic recording medium was manufactured in the same manner as in Experimental Example 7, and the same magnetic data was written in the two-layered magnetic recording layer of this magnetic recording medium in the same manner as in Experimental Example 1 (write current: 90 mA). After writing, another magnetic data was written again without heating with a write current of 150 mA, and different magnetic data was recorded on the first magnetic layer and the second magnetic layer.

Next, an attempt was made to read the magnetic data as it was, but two types of magnetic data were mixed and normal magnetic data could not be reproduced. On the other hand, first, 15
After erasing the magnetic data of the low coercivity layer (second magnetic layer) with an erasing current of 0 mA, reading was performed, and the magnetic data written first could be reproduced. (Experimental Example 9) A magnetic recording medium was manufactured in the same manner as in Experimental Example 7, except that the thicknesses of the first magnetic layer and the second magnetic layer were doubled to 30 μm and 20 μm, respectively. (Write current: 90 mA), and magnetic data was written to the two-layered magnetic layer of the magnetic recording medium.

Next, when the magnetic data was read, reproduction was performed at twice the predetermined output (800 mV), and an error occurred. On the other hand, when reading was performed while heating at 130 ° C., reproduced data of approximately a predetermined output was obtained, and reading was possible. (Experimental Example 10) A magnetic recording medium was manufactured in the same manner as in Experimental Example 7, except that the thickness of the first magnetic layer was 30 μm and the thickness of the second magnetic layer was 10 μm. Current 9
0 mA), and magnetic data was written to the two-layered magnetic layer of the magnetic recording medium.

Next, when the magnetic data was read, reproduction was performed at an output 1.5 times the predetermined output (800 mV), resulting in an error. On the other hand, while heating at 80 ° C., the output of the high coercive force layer (first magnetic layer) was set to 50%,
When reading was performed so that a predetermined output was obtained by combining outputs of the first magnetic layer and the second magnetic layer, normal reading was possible. (Experimental Example 11) A magnetic recording medium was manufactured in the same manner as in Experimental Example 7, and in the same manner as in Experimental Example 1 (write current: 90 mA).
The same magnetic data is written to the two-layered magnetic recording layer of the magnetic recording medium, and then the write current is again increased to 150 mA.
, Another magnetic data was written without heating, and different magnetic data were recorded on the first magnetic layer and the second magnetic layer.

Next, when reading was performed with the output of the high coercivity layer (first magnetic layer) being 10% or less while heating at 130 ° C., normal magnetic data could be reproduced.

Next, after the normal reading was performed as described above, the magnetic recording medium was cooled to room temperature, and thereafter, an attempt was made to read the magnetic data. Magnetic data could not be reproduced.

In the above-mentioned heating at the time of reproduction, the heating temperature is set to the Curie point (140) of the high coercive force layer (first magnetic layer).
C.), the magnetic data recorded on the high coercivity layer (first magnetic layer) was erased, resulting in a single-layer magnetic card.

[0085]

As described above, according to the present invention, forgery and alteration can be easily and effectively prevented because the magnetic layer made of a magnetic material having a different Curie point and coercive force is provided on the substrate. can do.

When recording is performed on the magnetic recording medium of the present invention, the coercive force of the high coercive force magnetic material can be reduced by heating to reduce the energy required for recording, that is, the recording current. Therefore, forgery can be made more difficult by combining the temperature at the time of recording and the recording current value to vary the recording form. That is, since the coercive force of the magnetic material changes depending on the temperature at the time of recording, the saturation characteristic (read output with respect to the recording current) changes. In other words, even if recording is performed with the same recording current, the read output will vary depending on the temperature at the time of recording, and if the coercive force differs depending on the temperature during recording, the recording current must be reduced to obtain the same output. I have to change. Further, since there are a plurality of magnetic materials having different coercive forces and Curie points, various reading outputs can be obtained depending on the temperature and the recording current during recording.
By making a system that uses these various read outputs as forgery discrimination data and making it difficult to find appropriate conditions for reading, forgery becomes more difficult.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a magnetic recording medium according to the present invention.

FIG. 2 is a sectional view of another embodiment of the magnetic recording medium.

FIG. 3 is a sectional view of another embodiment of the magnetic recording medium.

FIG. 4 is a sectional view of an embodiment of the transfer laminate according to the present invention.

FIG. 5 is a cross-sectional view of an embodiment of the adhesive laminate according to the present invention.

FIG. 6 is a sectional view of another embodiment of the magnetic recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magnetic recording medium 2 ... Substrate 3 ... 1st magnetic layer 4 ... 2nd magnetic layer 5 ... Mixed magnetic layer 6 ... Release layer 7 ... Adhesive layer 8 ... Coloring layer 9 ... Protective layer 2 '... Transferring substrate 2 "... Adhering substrate 21 ... Transfer laminate 31 ... Adhering laminate

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-174360 (JP, A) JP-A-3-187017 (JP, A) JP-A-3-93033 (JP, A) JP-A-1- JP-A-216891 (JP, A) JP-A-64-52223 (JP, A) JP-A-63-34727 (JP, A) JP-A-4-10215 (JP, A) JP-A-57-78652 (JP, A) JP-A-3-260939 (JP, A) JP-A-3-102666 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/00 B42D 15/10 G06K 19/06

Claims (1)

(57) [Claims] 1. A magnetic layer comprising a magnetic material A having a magnetic property having a Curie point of Tc and a magnetic material B having a magnetic property having a higher Curie point and a lower coercive force than the magnetic material on a substrate. A method for recording a magnetic recording medium comprising: heating the magnetic layer to a temperature lower than Tc .
The saturation write current between the magnetic material A and the magnetic material B
And the saturation write current
The magnetic material A and the magnetic material
B. A method for recording on a magnetic recording medium, wherein magnetic recording is performed simultaneously on B.