JP3523300B2 - Magnetic recording media - 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 having a magnetic material having a high coercive force and a high Curie point, which is difficult to counterfeit or alter.

[0002]

2. Description of the Related Art A magnetic recording medium having a magnetic recording layer formed on one side or both sides of a substrate or in a stripe shape is
For example, prepaid card, commuter pass, ticket, admission ticket,
Car tickets, betting tickets, gift certificates, stock certificates, certificates, passbooks, magnetic tags and other cash vouchers, securities, ID cards, cash cards, credit cards, membership cards and other cards, magnetic tape,
Widely used as magnetic transfer tapes and magnetic labels. Conventionally, in such a magnetic recording medium, information is written in a magnetic recording layer at a high recording density so that the recorded information cannot be easily read from the outside.

However, because of the characteristics of the magnetic recording layer, the recorded information can be freely rewritten and erased, so that it can be forged and altered, and in recent years, it has been highlighted as a major social problem. In particular, since it is now easy to obtain a magnetic stripe, it is possible to manufacture a similar card. In addition, when the magnetic recording layer is exposed on the surface of the magnetic recording medium as in the current specifications. However, there is also a problem that magnetic recording information can be easily transferred to another magnetic recording layer by the magnetic transfer technique.

[0004]

In order to solve such a problem, a magnetic recording medium has been developed in which the magnetic material used for the magnetic recording layer has a high coercive force. By heating the magnetic recording layer to lower the coercive force of the magnetic material, this magnetic recording medium can be recorded and reproduced by a normal magnetic head that is easily available. Is difficult and cannot be forged or altered.

However, the above magnetic recording medium is different from the conventional magnetic recording medium only in that heating is required at the time of recording, and once this fact is clarified, high coercive force is obtained. After the regular magnetic recording information is erased by the permanent magnet, the illegal magnetic recording information can be recorded while heating the magnetic recording layer, and it is still not sufficient from the viewpoint of preventing forgery and alteration.

The present invention has been made in view of such circumstances, and it is possible to easily identify even if forgery or alteration is performed by erasing the legitimate magnetic record information and recording the illegal magnetic record information. It is an object of the present invention to provide a magnetic recording medium capable of achieving the above.

[0007]

In order to achieve such an object, the present invention constitutes a magnetic recording layer in a magnetic recording medium having a substrate and a magnetic recording layer on the substrate.
At least one of the magnetic materials has not been oriented.
A magnetic material having a high coercive force of 10000 Oe or more and a high Curie point of 300 ° C. or more, which constitutes the magnetic recording layer.
One of the magnetic materials has higher coercive force and lower curie than the other.
There is a relationship that becomes a point and the orientation treatment is applied.
The structure is such that two or more magnetic materials having a magnetic force of less than 10,000 Oe are used .

Further, in the present invention, in a magnetic recording medium having a substrate and a magnetic recording layer on the substrate, the magnetic recording layer is
It has a laminated structure and at least one layer is 10,000
High coercive force of Oe or more, magnetism of high Curie point of 300 ° C or more
A layer that has a conductive material and is not subjected to orientation treatment.
One layer of the other layers constituting the magnetic recording layer is
Magnetic material with higher coercive force and lower Curie point than the other layer
And the magnetic material is oriented.
It is a magnetic material with a coercive force of less than 10,000 Oe.
It is configured to have two or more layers such as eel . Further, the present invention provides a magnetic recording medium having a substrate and a magnetic recording layer on the substrate, wherein the magnetic recording layer has a laminated structure.
In addition, at least one layer has a high coercive force of 10,000 Oe or more,
Having a magnetic material with a high Curie point of 300 ° C or higher, and
The magnetic recording layer is a layer that has not been subjected to orientation treatment.
One of the other constituent layers has a higher coercive force and a lower coefficient than the other.
Has a relationship that is the Curie point, and has undergone orientation treatment.
Two or more magnetic materials with a coercive force of less than 10,000 Oe
It was configured to have a layer containing .

[0009]

The magnetic recording layer constituting the magnetic recording medium is made of two or more kinds of magnetic materials including at least a magnetic material having a high coercive force and a high Curie point which is not subjected to orientation treatment, or constitutes a magnetic recording medium. The magnetic recording layer has a laminated structure of two or more layers, and this magnetic recording layer is provided with a layer having a magnetic material having a high coercive force and a high Curie point, and since this layer is not subjected to orientation treatment, When reproducing the magnetic recording information recorded on the magnetic recording layer, a high coercive force,
There is no inhibition of reproduction by a magnetic material having a high Curie point, or reproduction inhibition by a layer having a magnetic material having a high Curie point or a high Curie point, but the magnetic recording information recorded in the magnetic recording layer is a permanent magnet having a high coercive force. When erased illegally by, a magnetic field is generated in the above-mentioned high coercive force, high Curie point magnetic material, or high coercive force, high Curie point magnetic recording layer,
Even if illegal magnetic recording information is recorded in the magnetic recording layer, the magnetic recording information has extremely high noise due to the magnetic field, and normal reproduction of the magnetic recording information is prevented.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view showing an example of a magnetic recording medium of the present invention having a magnetic recording layer having a multilayer structure.
In FIG. 1, a magnetic recording medium 1 includes a base 2 and a magnetic recording layer 3 provided on the base 2. The magnetic recording layer 3 is the first magnetic recording layer 3a located on the base 2 side.
And a second magnetic recording layer 3b and a third magnetic recording layer 3c sequentially formed on the first magnetic recording layer 3a. The magnetic materials contained in the first magnetic recording layer 3a and the second magnetic recording layer 3b have Curie points and coercive forces different from each other, and the third magnetic recording layer 3c
Is a layer having a magnetic material having a high coercive force and a high Curie point.

The substrate 2 has a heat resistance required as a substrate,
Considering strength, rigidity, hiding power, light opacity, etc., resin such as nylon, cellulose diacetate, cellulose triacetate, vinyl chloride, polystyrene, polyethylene, polypropylene, polyester, polyimide, polycarbonate, metal such as copper, aluminum, etc. It can be composed of a composite of materials appropriately selected from materials such as paper, impregnated paper and the like. The thickness of such a base 2 can be set to about 0.005 mm to 5 mm.

In the magnetic recording layer 3, as described above,
One of the magnetic materials contained in the first magnetic recording layer 3a constituting the magnetic recording layer 3 and the magnetic material contained in the second magnetic recording layer 3b has a higher coercive force and a lower Curie point T than the other.
have c. And, the magnetic recording medium of the present invention comprises the above-mentioned first magnetic recording layer 3a and second magnetic recording layer 3a which constitute the magnetic recording layer 3.
In addition to the magnetic recording layer 3b, it is characterized by further having a layer (third magnetic recording layer 3c) which contains a magnetic material having a high coercive force and a high Curie point and is not subjected to orientation treatment.

First, the first magnetic recording layer 3a and the second magnetic recording layer 3b constituting the magnetic recording layer 3 will be described.

Magnetic recording having high coercive force and low Curie point Tc
As the magnetic material forming the recording layer, for example, the Curie point
Low CrO₂ , AO · n {(Fe_1-XY Cr_X Zn_Y )
₂ O ₃ }, AO · n {(Fe_1-X Cr_X )₂ O₃ }, A
O · n {(Fe_1-X Al_X )₂ O₃ }, AO · n {(F
e_1-X Ga_X )₂ O₃ }, AO · n {(Fe_1-XYZG
a_X Cr_Y Al_Z )₂ O₃ }, AO · n {(Fe_1-XY 
Cr_X Ga_Y )₂ O₃} (In the above, A is Sr or
One or two of Ba, represented by n = 5 to 6)
Such Sr ferrite, Ba ferrites, Nd-Fe
-B-Mn, Nd-Fe-B-Mn-Al, Nd-Fe
-B-Mn-Cr, Nd-Fe-B-Mn-Al-Cr
Magnetic fine particles such as Nd-Fe-B based alloys.
It Then, the above-mentioned magnetic fine particles are made of an appropriate resin or resin.
Gravure the dispersion that is dispersed in the vehicle.
In accordance with known coating methods such as roll coating, roll coating, knife edge coating, etc.
Can be applied to form a magnetic recording layer.
Wear.

As a magnetic material forming the magnetic recording layer having a low coercive force and a high Curie point, for example, γ-Fe ₂
O ₃ , Co deposition γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Fe, F
e-Cr, Fe-Co, Co-Cr, Co-Ni, Ba
Magnetic fine particles such as ferrite, Sr ferrite, and CrO ₂ can be used.

A low coercive force is obtained by applying a dispersion obtained by dispersing the above magnetic fine particles in a suitable resin or ink vehicle according to a known coating method such as a gravure method, a roll method or a knife edge method. A magnetic recording layer having a high Curie point can be formed. Alternatively, it can be formed by a vacuum vapor deposition method, a sputtering method, a plating method, or the like.

The average particle diameter of the above magnetic material is 0.1.
When the thickness is less than or equal to μm, the infrared transmittance of the magnetic recording layer is improved, and when a light heating method using infrared rays is used together,
Irradiated infrared rays can pass through a magnetic recording layer (magnetic recording layer having a high Curie point) that does not require heating to heat a predetermined magnetic recording layer.

Here, whether the magnetic recording layer having a high coercive force and a low Curie point is the first magnetic recording layer 3a or the second magnetic recording layer 3b can be selected in consideration of the following effects. it can.

That is, the first magnetic recording layer 3a is a magnetic recording layer having a high coercive force and a low Curie point Tc.
When the magnetic recording layer 3b is a magnetic recording layer having a low coercive force and a high Curie point, the upper second magnetic recording layer 3b hides the lower first magnetic recording layer 3a. Therefore, the first magnetic recording layer 3 made of a magnetic material having a high coercive force and a low Curie point.
It is difficult for counterfeiters to notice the existence of a. Further, since the second magnetic recording layer 3b made of a magnetic material having a low coercive force is provided on the upper layer, troubles due to magnetic transfer hardly occur. Further, by setting the average particle diameter of the magnetic material forming the second magnetic recording layer 3b to be 0.1 μm or less, the infrared permeability of the second magnetic recording layer 3b is improved. For this reason,
When the light heating method using infrared rays is used, there is an effect that only the first magnetic recording layer 3a can be selectively heated even though the first magnetic recording layer 3a is hidden.

On the other hand, when the first magnetic recording layer 3a is a magnetic recording layer having a low coercive force and a high Curie point Tc, and the second magnetic recording layer 3b is a magnetic recording layer having a high coercive force and a low Curie point, Since the second magnetic recording layer 3b is the upper layer, it becomes easy to directly heat the second magnetic recording layer 3b, which is a high coercive force layer, by heating. Further, during magnetic recording while heating, the heat rise distribution is concentrated on the upper second magnetic recording layer 3b, which is a magnetic recording layer having a high coercive force and a low Curie point,
Since thermal diffusion to the lower magnetic recording layer 3a, which is the first magnetic recording layer 3a and has a high Curie point, is small,
The Curie point of the first magnetic recording layer 3a can be made relatively low, and heat damage can be reduced. Further, at the time of magnetic recording, the layer far from the magnetic head is a magnetic recording layer having a low coercive force, so that the magnetic field strength (write current value) can be reduced. Furthermore, since the upper layer is a high coercive force magnetic recording layer, it is difficult for a counterfeiter to notice the lower first magnetic recording layer 3a.

Next, the third magnetic recording layer 3c constituting the magnetic recording layer 3 will be described. The third magnetic recording layer 3c is a layer that contains a magnetic material having a high coercive force and a high Curie point and is not subjected to orientation treatment. The magnetic material used has a coercive force of 5000 Oe or more, preferably 10000 Oe or more. Further, those having a Curie point of 200 ° C. or higher, preferably 300 ° C. or higher can be mentioned. When the coercive force is less than 5000 Oe, a magnetic field is generated in the third magnetic recording layer 3c due to the recording of the magnetic recording information on the magnetic recording layer 3, which hinders the reproduction. If the Curie point is less than 200 ° C., the coercive force of the third magnetic recording layer 3c is lowered by heating when the magnetic recording layer 3 is heated to record magnetic recording information, and the above coercive force is low. Similarly to the case, the recording of the magnetic recording information on the magnetic recording layer 3 causes a magnetic field to be generated in the third magnetic recording layer 3c, which hinders the reproduction.

As the magnetic material which can be used for the third magnetic recording layer 3c, specifically, BaFe ₁₂ O ₁₉ (1
7 kOe), SrFe ₁₂ O ₁₉ (20 kOe), Na _0.5
Magnetoprambite-type compounds such as La _0.5 Fe ₁₂ O ₁₉ and BaFe ₁₁ GaO ₁₉ , Ce, Sm, Pr-based cobalt alloys (for example, trade name Hicorex 20 (9 kOe),
Examples include magnetic fine particles such as rare earth cobalt magnetic materials such as Hicorex 26 (10 kOe), MnBi magnetic materials, and MnAl magnetic materials.

Then, a dispersion obtained by dispersing the above-mentioned magnetic fine particles in a suitable resin or ink vehicle is applied according to a known application method such as a gravure method, a roll method or a knife edge method to obtain a high coercive force and a high coercive force. A magnetic recording layer having a Curie point can be formed. Alternatively, it can be formed by a vacuum vapor deposition method, a sputtering method, a plating method, or the like.

The magnetic recording layer 3 having such a structure is heated at a temperature lower than the Curie point Tc of the magnetic recording layer having the low Curie point Tc, so that the first magnetic recording layer 3a is heated.
And the saturation write current values of the second magnetic recording layer 3b are substantially the same or approaching each other, so that a specific write current set value of the magnetic material having a low coercive force (for example, 1.5 to 2.
The saturation current value of a magnetic material having a high coercive force is smaller than that of (0 times).

For example, the first magnetic recording layer 3a has a high coercive force,
When the second magnetic recording layer 3b is a magnetic recording layer having a low Curie point Tc and the second magnetic recording layer 3b is a magnetic recording layer having a high Curie point, the second magnetic recording layer 3b is heated at a temperature lower than the Curie point Tc to have a high coercive force magnetic recording. The coercive force of the first magnetic recording layer 3a, which is a layer, can be lowered, and the saturation write current value can be made substantially the same as or close to the saturation write current value of the second magnetic recording layer 3b. As a result, a specific write current setting value of the magnetic material having a low coercive force (for example, a saturation current value of 1.5 to 2.0) is set.
The saturation current value of a magnetic material having a high coercive force can be made smaller than that of the above. At this time, if the heating temperature is too low,
When the saturation write current value of the first magnetic recording layer 3a which is a high coercive force magnetic recording layer does not reach the same level as the saturation write current value of the second magnetic recording layer 3b, or when writing to the low coercive force magnetic recording layer At the write current value, saturation writing in the high coercive force magnetic recording layer cannot be performed, so it is preferable to set the lower limit of the heating condition to a temperature of about 1/2 of the low Curie point Tc. Further, if the Curie points of the two magnetic recording layers 3a and 3b are close to each other, the coercive force of the second magnetic recording layer 3b, which is a low-coercive-force magnetic recording layer, is also lowered. Therefore, it is preferable to set the difference between the Curie points of the two magnetic recording layers 3a and 3b to 100 ° C. or more to prevent the coercive force of the low coercive force magnetic recording layer from decreasing. Further, in order to prevent the magnetic recording on the first magnetic recording layer 3a and the second magnetic recording layer 3b from being influenced by each other, the coercive force difference between the two magnetic recording layers 3a and 3b should be set to twice or more. Is preferred.

On the other hand, the third magnetic recording layer 3c is made of a magnetic material having a high coercive force and a high Curie point, and is not subjected to orientation treatment with a high coercive force (for example, 6000 Oe) magnet. A magnetic field is not generated in the third magnetic recording layer 3c by the recording in the third magnetic recording layer 3a and the magnetic recording information recorded in the first magnetic recording layer 3a and the second magnetic recording layer 3b. The reproduction can be favorably performed without any influence of the third magnetic recording layer 3c.

Since the magnetic recording medium 1 of the present invention is provided with the magnetic recording layer 3 having the above-mentioned structure, the magnetic recording information recorded on the magnetic recording layer 3 is recorded by a high coercive force permanent magnet or the like. When erased illegally, a magnetic field is generated in the third magnetic recording layer 3c containing a magnetic material having a high coercive force and a high Curie point. Since the magnetic field generated in the third magnetic recording layer 3c can no longer be extinguished, the first magnetic recording layer 3a, the second magnetic recording layer 3c
Even if illegal magnetic recording information is recorded on the magnetic recording layer 3b, the magnetic recording information has extremely high noise due to the above magnetic field, which prevents normal reproduction of the magnetic recording information.

As the resin or ink vehicle used for forming the magnetic recording layer 3, butyral resin, vinyl chloride / vinyl acetate copolymer resin, urethane resin, polyester resin, cellulose resin, acrylic resin, styrene / Maleic acid copolymer resin etc. are used,
Rubber-based resin such as nitrile rubber or 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 a system in which Tg increases due to 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, or garbon is added to the dispersion obtained by dispersing the magnetic fine particles in the resin or the ink vehicle as described above. May be.

The thickness of the first magnetic recording layer 3a, the second magnetic recording layer 3b and the third magnetic recording layer 3c formed by using the above magnetic material, resin or ink vehicle is as follows.
When it is formed by a coating method, the thickness is about 1 to 100 μm, preferably about 5 to 20 μm. Also, the vacuum deposition method,
When formed by a sputtering method, a plating method or the like, the thickness is 100 Å to 1 μm, preferably about 500 to 2000 Å.

In the above example, the third magnetic recording layer 3c is the second
Although formed on the magnetic recording layer 3b, the third magnetic recording layer 3c is provided between the base material 2 and the first magnetic recording layer 3a, or between the first magnetic recording layer 3a and the second magnetic recording layer 3b. May be formed in. In the above example, the third magnetic recording layer 3c
Is formed on the entire surface of the second magnetic recording layer 3b, but the present invention is not limited to this and may have a bar pattern shape as shown in FIG. 2, for example. When the magnetic recording information of the magnetic recording layer 3 is erased by the permanent magnet having a high coercive force by providing the third magnetic recording layer 3c having such a bar pattern, as shown in FIG. A magnetic field was generated in the bar pattern, which means that the bar pattern was recorded for the first time. Therefore, as described above, the magnetic field of the third magnetic recording layer 3c acts as noise during reproduction, which obstructs reproduction, and the magnetic field from the third magnetic recording layer 3c can also be read as fixed magnetic information. Is. The bar pattern has a width of 10 nm to 100 μm.
m, and the thickness can be formed in the range of 1 to 50 μm.

In the above example, the magnetic recording layer (layers other than the high coercive force and high Curie point layer) for performing normal recording and reproduction in the magnetic recording layer 3 is the first magnetic recording layer 3a.
The second magnetic recording layer 3b and the second magnetic recording layer 3b may be three layers or more, and may be composed of three or more magnetic materials having different coercive forces and Curie points. . When the layers other than the high coercive force and high Curie point layers have a three-layer structure, for example, (high coercive force / low Curie point) /
By setting (low coercive force / high Curie point) / (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. In addition, the coercive force is set to 3 steps to write further magnetic data to the intermediate coercive force layer, or the Curie point is set to 3 steps and the heating temperature is set to 2.
By setting the stages, a more advanced recording / reproducing system can be realized.

The magnetic recording medium of the present invention is not provided with the magnetic recording layer having the laminated structure as described above, and at least one magnetic material having a high coercive force and a high Curie point which is not subjected to the orientation treatment. A magnetic recording layer having a single-layer structure as contained can be provided, and the same effect as that having a magnetic recording layer having a laminated structure can be obtained. That is, if the magnetic recording information recorded on the magnetic recording layer having the single-layer structure is illegally erased by a permanent magnet having a high coercive force,
A magnetic field is generated in a magnetic material having a high coercive force and a high Curie point.
Since this magnetic field can no longer be erased, even if illegal magnetic recording information is recorded in a magnetic material other than the high coercive force and high Curie point magnetic material in the magnetic recording layer, the magnetic field described above causes noise in the magnetic recording information. This is extremely high, which prevents normal reproduction of magnetic recording information.

FIG. 4 is a schematic sectional view showing another example of the magnetic recording medium of the present invention having a magnetic recording layer having a multilayer structure. In FIG. 4, the magnetic recording medium 11 of the present invention is a substrate 1.
2 and a magnetic recording layer 13, a diffraction grating and / or a hologram layer 14 provided on the base 12. The magnetic recording layer 13 has a first
The magnetic recording layer 13a, the second magnetic recording layer 13b, and the third magnetic recording layer 13c have a three-layer structure, and the first magnetic recording layer 3a, the second magnetic recording layer 3b, and the magnetic recording layer 3b of the magnetic recording medium 1 described above, Which corresponds to the third magnetic recording layer 3c,
The description here is omitted.

The diffraction grating and / or hologram layer 14 used in the magnetic recording medium 11 of the present invention is generally made of resin and may have either a single structure or a multi-layer structure. In the case of a multilayer structure, for example, a resin for forming a diffraction grating or a hologram is provided on a base film,
Alternatively, the resin itself for forming the diffraction grating or the hologram may have a laminated structure. Further, the entire area may be a diffraction grating layer or a hologram layer, or the diffraction grating layer and the hologram layer may be mixed.

The hologram layer may be either a plane hologram or a volume hologram. In the case of a plane hologram, a relief hologram is preferable in terms of mass productivity, durability and cost. In the case of a volume hologram, a Lippmann hologram is used for image reproducibility and image reproducibility. It is preferable in terms of mass productivity.

In addition, laser reproduction holograms such as full-nel holograms, Fraunhofer holograms, lensless Fourier transform holograms, and image holograms,
A white light reproduction hologram such as a rainbow hologram, a color hologram utilizing these principles, a computer hologram, a hologram display, a multiplex hologram, a holographic stereogram, a holographic diffraction grating, or the like can be used.

The diffraction grating layer may be formed of the holographic diffraction grating using the hologram recording means, but it is calculated based on calculation by mechanically forming the diffraction grating using an electron beam drawing device or the like. A diffraction grating that can obtain arbitrary diffracted light can be created. Photosensitive materials for forming diffraction gratings or holograms for recording interference fringes include silver salts, dichromated gelatin, thermoplastics, diazo-based photosensitive materials, photoresists, ferroelectrics, photochromic materials, and thermosensitive materials. Chromix materials, chalcogen glass, etc. can be used.

In the present invention, as a material for forming the diffraction grating layer and the hologram layer, polyvinyl chloride, acrylic such as methylmethacrylate, thermoplastic resin such as polystyrene and polycarbonate, unsaturated polyester, melamine, epoxy, polyester ( (Meth) acrylate,
A cured product of a thermosetting resin such as urethane (meth) acrylate, epoxy (meth) acrylate, polyether (meth) acrylate, polyol (meth) acrylate, melamine (meth) acrylate or triazine acrylate, or the above heat Mixtures of plastic resins and thermosetting resins can be used.

Further, as a material for forming the diffraction grating layer and the hologram layer, a thermoformable substance having a radical polymerizable unsaturated group can be used, and there are the following two types. (1) A polymer having a radically polymerizable unsaturated group in a polymer having a glass transition point of 0 to 250 ° C. More specifically, examples of the polymer obtained by polymerizing or copolymerizing the compounds shown in the following to have a radically polymerizable unsaturated group introduced by the methods (a) to (d) described below are mentioned. it can.

Monomers having hydroxyl groups: N-methylolacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2
-Hydroxybutyl methacrylate, 2-hydroxy-
3-phenoxypropyl methacrylate, 2-hydroxy-3-phenoxypropyl acrylate and the like.

Monomers having a carboxyl group: acrylic acid, methacrylic acid, acryloyloxyethyl monosuccinate and the like.

Monomers having an epoxy group: glycidyl methacrylate and the like.

Monomer having aziridinyl group: 2-
Aziridinyl ethyl methacrylate, allyl 2-aziridinyl propionate and the like.

Monomers having amide groups: acrylamide, methacrylamide, diacetone acrylamide, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate and the like.

Monomers having sulfone groups: 2-acrylamido-2-methylpropanesulfonic acid, etc.

Monomer having isocyanate group:
Diisocyanates such as 1 mol to 1 mol adduct of 2,4-toluene diisocyanate and 2-hydroxyethyl acrylate, and adducts of radical-polymerizable monomers having active hydrogen.

In order to control the glass transition point of the above copolymer or the physical properties of the cured film, the above compound and the following monomer copolymerizable with this compound are copolymerized. It can also be polymerized. Copolymerizable monomers include methyl methacrylate, methyl acrylate,
Ethyl methacrylate, ethyl acrylate, propyl methacrylate, propyl acrylate, butyl methacrylate, butyl acrylate, isobutyl methacrylate, isobutyl acrylate, t-butyl methacrylate, t-butyl acrylate, isoamyl methacrylate, isoamyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, 2-ethylhexyl methacrylate , 2-ethylhexyl acrylate and the like.

Next, the polymer obtained as described above is reacted by the following methods (a) to (d) to introduce a radically polymerizable unsaturated group, whereby a resin for forming a diffraction grating or a hologram. A forming resin can be obtained.

(A) In the case of a polymer or copolymer of a monomer having a hydroxyl group, a monomer having a carboxyl group such as acrylic acid or methacrylic acid is subjected to a condensation reaction.

(B) In the case of a polymer or copolymer of a monomer having a carboxyl group or a sulfone group, the above monomer having a hydroxyl group is subjected to a condensation reaction.

(C) In the case of a polymer or copolymer of a monomer having an epoxy group, an isocyanate group or an aziridinyl group, the above-mentioned monomer having a hydroxyl group or a monomer having a carboxyl group is subjected to an addition reaction. Let

(D) In the case of a polymer or copolymer of a monomer having a hydroxyl group or a carboxyl group, a monomer having an epoxy group or a monomer having an aziridinyl group, a diisocyanate compound and a hydroxyl group-containing acrylic acid An addition reaction of 1: 1 mole of the ester monomer is carried out.

In order to carry out the above reaction, it is preferable to add a small amount of a polymerization inhibitor such as hydroquinone and to carry out the drying air.

(2) A compound having a melting point of 0 to 250 ° C. and a radically polymerizable unsaturated group. Specific examples include stearyl acrylate, stearyl methacrylate, triacryl isocyanurate, cyclohexanediol diacrylate, cyclohexanediol dimethacrylate, spiroglycol diacrylate, and spiroglycol dimethacrylate.

Further, as the diffraction grating forming resin or the hologram forming resin in the present invention, the above (1),
(2) can be mixed and used, and a radically polymerizable unsaturated monomer can be added to them. This radically polymerizable unsaturated monomer improves the crosslink density and the heat resistance upon irradiation with ionizing radiation, and in addition to the above monomers, ethylene glycol diacrylate and ethylene glycol dimethacrylate. , Polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, pentaerythritol tetraacrylate, Pentaerythritol tetramethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipenta Risuri hexaacrylate, dipentaerythritol hexa methacrylate,
Ethylene glycol diglycidyl ether diacrylate, ethylene glycol diglycidyl ether dimethacrylate, polyethylene glycol diglycidyl ether diacrylate, polyethylene glycol diglycidyl ether dimethacrylate, propylene glycol diglycidyl ether diacrylate, propylene glycol diglycidyl ether dimethacrylate, polypropylene glycol Diglycidyl ether diacrylate, polypropylene glycol diglycidyl ether dimethacrylate, sorbitol tetraglycidyl ether tetraacrylate, sorbitol tetraglycidyl ether tetramethacrylate, etc. can be used. Such a monomer is preferably used in a proportion of 0.1 to 100 parts by weight based on 100 parts by weight of the solid content of the copolymer mixture. Further, although the above can be sufficiently cured by electron beam, when cured by ultraviolet irradiation, benzoquinone as a sensitizer, benzoin, benzoin ethers such as benzoin methyl ether, halogenated acetophenones It is also possible to use those that generate radicals by irradiation with ultraviolet rays, such as bisacyl, and the like.

Further, in order to efficiently heat the magnetic recording layer described later, the diffraction grating layer 14 or the hologram layer 1
It is preferable that 4 has high thermal conductivity. Here, the thermal conductivity κ of the above-mentioned resin constituting the diffraction grating layer 14 or the hologram layer 14 is 0.1 to 0.3 (Joule
/ M · sec · k), which is low. For this reason, additives having a thermal conductivity κ of 10 (Joule / m · sec · k) or more, for example, plasticizers such as ethylene glycol, glycerin, and dioctyl phthalate (κ is several hundred (Joule / m · sec · k)
k)), an oxidizing agent (κ is several tens to several hundreds (Joule / m · sec · k)) such as TiO ₂ , BeO or SiO ₂ is preferably contained in the diffraction grating layer 14 or the hologram layer 14.

Diffraction grating layer 14 or hologram layer 14
Can be formed by a conventionally known method. For example, when the hologram is a relief hologram, the hologram master on which interference fringes are recorded in the form of concavo-convex is used as a press mold, the hologram forming resin sheet is placed on this hologram master, and both are formed by means of a heating roll or the like. The hologram layer 14 having a relief forming surface can be obtained by a method of heating and pressing and heating the resin sheet for hologram formation to duplicate the uneven pattern of the hologram master plate. When the hologram is a volume hologram, it can be wound and duplicated by coating a photopolymer or the like on a substrate, superimposing it on a hologram original plate that has been created in advance, and irradiating it with a slit-shaped laser beam. it can.
Thereafter, processing such as heat development may be performed. In any case, it is possible to prepare a large number of duplicate plates or to make a random pattern so that each recording medium can hold an individual reproduced image as much as possible.

As shown in FIG. 5, the magnetic recording medium of the present invention may have a thin film layer 15 between the above-mentioned diffraction grating layer 14 or hologram layer 14 and the magnetic recording layer 13. . The thin film layer 15 may be any one as long as it exhibits a diffraction or hologram effect more effectively, and a general reflective metal thin film is usually used. Further, when the hologram is a transparent hologram, it may be any material as long as it does not hide the colored layer or the pattern on the magnetic recording layer 13 as described later,
For example, a transparent material having a refractive index different from that of the diffraction grating layer 14 or the hologram layer 14 and a reflective metal thin film layer having a thickness of 200 Å or less can be used.

In the former case, the refractive index of the transparent material may be larger or smaller than that of the diffraction grating layer 14 or the hologram layer 14, but the difference in refractive index is 0.1 or more, preferably 0.5 or more. The refractive index value is preferably 1.0 or more. As described above, by providing the transparent thin film layers having different refractive indexes, the diffraction or hologram effect can be exhibited, and further, the effect of not coloring the lower layer or hiding the pattern can be obtained.

In the case of the latter, although it is a reflective metal thin film, since the thickness is 200 Å or less, the transmittance of light waves is large, so that the function of producing the diffraction or hologram effect and the effect of non-concealment of the display section are exhibited. To do. That is, when a light wave passes through the reflective metal thin film, its amplitude sharply decreases at exp (-2πK) per wavelength, so that the transmittance becomes considerably small when the film thickness exceeds 200Å. Therefore, by setting the film thickness to 200 Å or less, the transmittance becomes sufficient and the diffraction or hologram effect can be exhibited. Further, by setting the film thickness to 200 Å or less, it is possible to eliminate the discomfort in appearance due to the high brightness of silver white which has been conventionally observed.

The following materials (1) to (6) are mentioned as materials used for forming the thin film layer 15 as described above. (1) A transparent continuous thin film having a refractive index larger than that of a diffraction grating layer or a hologram layer. There are a transparent continuous thin film in the visible region and a transparent continuous thin film in the infrared or ultraviolet region. Is Table 2
Are shown respectively. In the table, n represents the refractive index (hereinafter,
The same applies to (2) to (6)).

[0063]

[Table 1]

[0064]

[Table 2] (2) Transparent ferroelectric material having a refractive index larger than that of the diffraction grating layer or hologram layer Table 3 shows examples of the above-mentioned transparent ferroelectric material.

[0065]

[Table 3] (3) Transparent continuous thin film having a smaller refractive index than the diffraction grating layer or the hologram layer Table 4 shows examples of the transparent continuous thin film.

[0066]

[Table 4] (4) Reflective metal thin film having a thickness of 200Å or less The reflective metal thin film has a complex refractive index, and the complex refractive index n * is represented by n * = n−iK. Here, n is a refractive index and K is an absorption coefficient.

The materials of the reflective metal thin film that can be used in the present invention are shown in Table 5 together with the above-mentioned values of n and K.

[0068]

[Table 5] In addition to the materials listed in Table 5 above, Sn, In, T
e, Ti, Fe, Co, Zn, Ge, Pb, Cd, B
Metals such as i, Se, Ga and Rb can be used. Furthermore, oxides and nitrides of the above metals can also be used,
Further, the metal, its oxide, the nitride, etc. may be used alone or in combination of two or more kinds. (5) The resin diffraction grating layer or hologram layer having a different refractive index from the diffraction grating layer or hologram layer may have a larger or smaller refractive index. Examples of these are shown in Table 6.
Shown in.

[0069]

[Table 6] In addition to the resins listed in Table 6 above, general synthetic resins can be used, but resins having a large difference in refractive index from the diffraction grating layer or hologram layer are particularly preferred. (6) Laminated body obtained by appropriately combining the materials shown in (1) to (5) The combination of the materials described in (1) to (5) is arbitrary, and the vertical positional relationship of each layer in the layer structure is arbitrary. Can be arbitrarily selected.

Of the above thin film layers (1) to (6),
The thickness of the thin film layer of (4) is preferably 200 Å or less,
The thickness of the thin film layer of (1) to (3) and (5), (6) may be in the range where the thin film layer can maintain transparency, and can be appropriately set depending on the material used, and is generally 10 to 10000Å, preferably 100 to 5000
It is about Å.

As a method for forming a thin film layer using the materials shown in the above (1) to (4), a vacuum deposition method, a sputtering method, a reactive sputtering method, an ion plating method, an electroplating method. A general thin film forming means such as the above can be used. When the thin film layer is formed using the material as shown in (5) above, a general coating method or the like can be used. Further, when the thin film layer is formed by using the material as shown in the above (6), the above means, methods and the like can be appropriately combined and used.

When the material as shown in the above (5) is used, the material may not be a thin film as long as it is a transparent material.
A resin layer having a thickness of 0.5 μm or more, preferably 1.0 to 3.0 μm may be formed. In particular, by using a transparent type, it is possible to determine at a glance that the magnetic recording layer and the pattern layer are laminated. Further, at the time of optical heating, the light directly reaches the magnetic recording layer, which is more effective.

As described above, the magnetic recording medium 11 of the present invention.
Then, the presence of the diffraction grating layer 14 or the hologram layer 14 on the magnetic recording layer 13 prevents the magnetic recording layer from being exposed, and the information written in the magnetic recording layer is directly transferred to the magnetic stripe of another card. Transferring magnetic transfer becomes difficult. Then, the diffraction grating layer 14 or the hologram layer 14
Is beautiful in appearance, is not easy to manufacture by itself, and is difficult to produce a similar product. The magnetic recording medium of the present invention having such a structure is a magnetic recording medium that is more difficult to forge or alter.

The magnetic recording medium of the present invention may have a protective layer on the diffraction grating layer 14 or the hologram layer 14. The protective layer can be formed on the diffraction grating layer 14 or the hologram layer 14 by laminating a synthetic resin film, by an extrusion coating method, or by coating a synthetic resin paint. The resin constituting the protective layer may be the same as the synthetic resins used in forming the above-mentioned colored layer in consideration of durability, heat resistance, adhesion to other layers, etc., A UV / electron beam curable resin having high physical properties is more preferable.

As the ionizing radiation curable resin for forming the protective layer, a mixed resin composition of a prepolymer, an oligomer, and / or a monomer having a weight unsaturated bond or an epoxy group in the molecule is used. . Specific examples of the above prepolymers and oligomers include unsaturated polyesters such as condensation products of unsaturated dicarboxylic acids and polyhydric alcohols, and methacrylates such as polyester methacrylate, polyether methacrylate, polyol methacrylate, and melamine methacrylate. Acrylates such as polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate, polyol acrylate, and melamine acrylate. Further, specific examples of the monomer include styrene,
Acrylic ester such as styrene monomer such as α-methylstyrene, methyl acrylate, 2-ethylhexyl acrylate, methoxyethyl acrylate, butoxyethyl acrylate, butyl acrylate, methoxybutyl acrylate, phenyl acrylate, etc. , Methyl methacrylate, ethyl methacrylate, propyl methacrylate, methoxyethyl methacrylate, ethoxymethyl methacrylate, phenyl methacrylate, and other methacrylic acid esters, 2- (N, N-diethylamino) ethyl acrylate, methacrylic acid -2- (N, N-dimethylamino) ethyl, acrylic acid-2- (N, N-dibenzylamino)
Substituted amino alcohol esters of unsaturated acids such as ethyl, 2- (N, N-dimethylamino) methyl methacrylate, and 2- (N, N-diethylamino) propyl acrylate, unsaturated such as acrylamide and methacrylamide. Carboxamide, ethylene glycol diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate and other diacrylate compounds, dipropylene glycol diacrylate, Polyfunctional compounds such as ethylene glycol acrylate, propylene glycol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane trithioglycollate , Trimethylolpropane thio propylate, a polythiol compound having two or more thiol groups in the molecule such as pentaerythritol thioglycolate and the like are used. When the protective layer is formed of the ionizing radiation-curable resin as described above, in consideration of the coating suitability of the coating agent of the ionizing radiation-curable resin, usually 5 to 5 of the above-mentioned prepolymers or oligomers is used.
A mixed composition of 95 wt% with 95 to 5 wt% of the monomer and / or polythiol compound is utilized. Further, in the coating agent of the ionizing radiation curable resin, when the coating agent is cured by irradiation of ultraviolet rays, for example, acetophenones, benzophenones, Michler benzoyl benzoate, α-amyloxime ester, tetramethylmeuram Monosulfide,
It goes without saying that a photopolymerization initiator such as thioxanthone and the like and a photosensitizer such as n-butylamine, triethylamine, tri-n-butylphosphine and the like may be added if necessary.

The coating method for forming the protective layer is as follows: roll coat, curtain flow coat, wire bar coat, reverse coat, gravure coat, gravure reverse coat, air knife coat, kiss coat, blade coat, smooth coat, A known method such as comma coat can be used.

Further, the curing in the formation of the protective layer by the ionizing radiation curable resin is performed by irradiating ultraviolet rays from a light source such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a black light lamp, a metal halide lamp, or a cock loft. 100 to 10 by various electron beam accelerators such as walton type, handigraph type, resonance transformer type, insulating core transformer type, linear type, dynamitron type and high frequency type
Electron beam irradiation with an energy of 00 keV, preferably 100-300 keV is used.

In order to improve durability and heat resistance, the protective layer is a powder such as Teflon powder, preferably having a softening point of 100 ° C. or higher and a high transparency and a particle size of several μm.
Further, fine powder of submicron size may be contained. Further, silicone, polyethylene wax or the like may be added to the protective layer to give the surface releasability.

Incidentally, such a protective layer and the diffraction grating layer 14
Alternatively, in order to improve the adhesiveness between both layers and the hologram layer 14 and to enhance the durability of the diffraction grating layer 14 or the hologram layer 14, a curable acrylic resin, a cellulose resin, a vinyl resin, or the like is used. An overprint layer may be provided. In addition, the thin film layer 15 and the magnetic recording layer 1 described above.
An anchor layer made of a vinyl chloride / vinyl acetate copolymer, an acrylic resin, a urethane resin, or the like may be provided between the adhesive layer 3 and the adhesive layer 3 in order to enhance the adhesiveness of both layers.

The magnetic recording medium of the present invention may be provided with an adhesive layer between each layer, if necessary. In this case, the adhesive layer is a vinyl chloride / vinyl acetate copolymer, ethylene /
Vinyl acetate copolymer, vinyl chloride / propionic acid copolymer, rubber-based resin, cyanoacrylate resin, cellulose-based resin, ionomer resin, polyolefin-based copolymer and other binders, if necessary, a plasticizer, a stabilizer, a stabilizer, It can be formed by adding a curing agent or the like and then applying it with a coating material for an adhesive layer which is sufficiently kneaded with a solvent or a diluent. The coating of the adhesive layer is applied by the gravure method,
It can be performed by a coating method such as a roll method or a knife edge method. Especially when an adhesive layer is provided on the magnetic recording layer,
In order to prevent the magnetic recording layer from being redissolved, it is preferable that a thermoplastic resin is emulsified and applied, and dried to form a heat-sealing type adhesive layer.

In the present invention, the concealment / decoration effect is provided on the magnetic recording layer 3 of the magnetic recording medium 1, on the magnetic recording layer 13 of the magnetic recording medium 11, or as shown in FIGS. You may provide a coloring layer and a pattern for holding.

The magnetic recording medium 11 shown in FIG. 6 has a hologram layer 1 recorded by a relief hologram method.
4 and the thin film layer 15 made of the above-mentioned transparent material having a refractive index different from the refractive index of the material forming the hologram layer 14, which is a transparent hologram. Then, the adhesive layer 17 is present between the magnetic recording layer 13 and the thin film layer 15, and the pattern 16 is formed. Even if the pattern 16 is in contact with the magnetic recording layer 13 as shown in FIG.
May be in contact with, and may be in the adhesive layer 17. As described above, when the pattern 16 is provided under the thin film layer 15, the pattern 16 is reproduced as a hologram by observing the magnetic recording medium 11 from the angle at which the reproduced image of the hologram can be seen due to the angle dependence of the hologram illumination light and the observer. If the image 16 is hidden by the image and is observed from an angle different from the above angle, the pattern 16 can be observed without being hidden by the hologram reproduction image.

In the example shown in FIG. 7, the magnetic recording medium 11
The colored layer 18 is formed between the hologram layer 14 and the magnetic recording layer 13 which are recorded by the method of the Lippmann hologram which is a volume hologram. The hologram layer 14 made of a Lippmann hologram is substantially transparent, and it is preferable that the colored layer 18 is composed of a dark colored paint from the viewpoint of the visibility of the reproduced hologram image and the concealment of the magnetic recording layer. In addition, because the Lippmann hologram has wavelength selectivity of reflected reproduction light,
Considering the decorative property, the colored layer 18 may be formed of a colored paint having a reflection wavelength different from the wavelength of the reflected reproduction light, or a colored paint having a complementary color relationship with the color of the hologram reproduction image by the reflected reproduction light may be used. preferable. Similar effects can be obtained by mixing a colored paint into the adhesive to form a colored adhesive.

In the example shown in FIG. 8, the magnetic recording medium 11
The pattern 16 is formed on the diffraction grating layer 14 on which the diffraction grating is recorded by mechanically drawing with an electron beam drawing apparatus, or between the diffraction grating layer 14 and the thin film layer 15 made of a reflective metal. ing. In this way, when the pattern layer 16 is formed on the thin film layer 15, the pattern 16 can be constantly observed with the light reflected by the thin film layer 15 as the background.
When the pattern 16 is formed on the diffraction grating layer 14, the protective layer 19 as described above is provided in order to prevent the pattern 16 from disappearing due to rubbing such as scanning of the magnetic head during recording / reproducing. Is preferred.

Colored layers and patterns include cellulose derivatives such as ethyl cellulose, cellulose nitrate, ethyl hydroxyethyl cellulose, cellulose acetate propionate and cellulose acetate, styrene resins such as polystyrene and poly-α-methylstyrene, or styrene copolymer resins,
Acrylic resins or methacrylic resins such as polymethylmethacrylate, polyethylmethacrylate, polyethylacrylate, polybutylacrylate, etc., homo or copolymer resins, rosins, rosin-modified maleic acid resins, rosin-modified phenolic resins, polymerized rosins, etc. Add various pigments to the binder such as rosin ester resin, polyvinyl acetate resin, coumarone resin, vinyltoluene resin, vinyl chloride resin, polyester resin, polyurethane resin, butyral resin, etc. according to the color to be colored. Accordingly, after adding a plasticizer, a stabilizer, a wax, a grease, a desiccant, a drying aid, a curing agent, a thickener, and a dispersant, a colored paint or an ink is prepared by sufficiently kneading with a solvent or a diluent. Using the usual gravure method, roll method, knife edge method, offset method, etc. The fabric method or printing method, can be formed in a desired portion.

The above-mentioned magnetic recording layer 13 and diffraction grating layer 1
4 and / or the hologram layer 14 is provided on the substrate 12, a magnetic transfer sheet is prepared, and an adhesive layer, a first magnetic recording layer, a second magnetic recording layer, and a third magnetic recording layer are prepared according to a conventionally known method. It is convenient to transfer the thin film layer and the diffraction grating and / or the hologram onto the substrate 12.

FIG. 9 is a schematic sectional view showing an example of a magnetic transfer sheet that can be used for manufacturing the magnetic recording medium of the present invention. In FIG. 9, the magnetic transfer sheet 21 is the base material 2
A resin layer serving as a diffraction grating and / or a hologram is formed on the second layer via a peeling layer 23, and a diffraction grating or a hologram relief pattern is formed by the above-described method such as thermal pressure contact with a relief matrix to form the diffraction grating layer and the hologram grating. And / or the hologram layer 24. Next, a thin film layer 25 is formed on the diffraction grating layer and / or the hologram layer 24 by using a method such as reactive vapor deposition and sputtering, and the third magnetic recording layer 26c and the second magnetic recording layer are formed on the thin film layer 25. 26b and the magnetic recording layer 26 including the first magnetic recording layer 26a are printed,
It is formed by a coating method or the like. Further, the adhesive layer 27 is formed on the first magnetic recording layer 26a. In this case, the first magnetic recording layer and the second magnetic recording layer are subjected to orientation treatment with a high coercive force (for example, 6000 Oe) permanent magnet, and the third magnetic recording layer (high coercive force and high Curie point layer) is processed. Orientation processing is not performed. In such a magnetic transfer sheet 21, the diffraction grating layer and / or the hologram layer 2
4 to the adhesive layer 27 serve as a transfer layer.

The magnetic transfer sheet 21 manufactured in this way
Is thermocompression-bonded (eg, 150 ° C., 10 minutes, 100 kg / cm ² condition) so that the adhesive layer 27 comes into contact with the base 12, and then the release layer 23 is used to remove the base material 22.
The adhesive layer, the first
A magnetic recording layer, a second magnetic recording layer, a third magnetic recording layer, a thin film layer, a diffraction grating layer and / or a hologram layer can be provided.

The diffraction grating layer and / or hologram layer 24, the thin film layer 25 and the magnetic recording layer 26 constituting the magnetic transfer sheet 21 are the magnetic recording layer 13, the diffraction grating layer and / or the hologram constituting the above-mentioned magnetic recording medium. It can be formed in the same manner as the formation of the layer 14 and the thin film layer 15. The adhesive layer 27 is made of a known adhesive such as acrylic resin, vinyl resin, polyester resin, urethane resin, amide resin, epoxy resin, rubber resin, or ionomer resin. Can be formed. The thickness of the adhesive layer 22 can be 0.1 to 50 μm, preferably 1 to 10 μm. Of course, the above-mentioned protective layer may be formed between the peeling layer and the hologram layer.

Next, a method of recording on the magnetic recording medium of the present invention as described above will be described.

In the method of recording on the magnetic recording medium of the present invention, magnetic recording is performed while heating the magnetic recording layer of the magnetic recording medium as described above. That is, by heating the magnetic recording layer, the saturation write current value of the magnetic material having a high coercive force and a low Curie point forming the magnetic recording layer is made approximately the same as or close to the saturation write current value of the magnetic material having a low coercive force. Writing is simultaneously performed on all the magnetic materials constituting the magnetic recording layer. In such magnetic recording while heating, since the coercive force of the high coercive force and high Curie point magnetic recording layer forming the magnetic recording layer does not decrease, magnetic recording information is not recorded. It should be noted that the heating or recording conditions may be set in two kinds, or may be conditions unique to each magnetic recording medium (conditions different for each magnetic recording medium). By setting, it becomes more difficult to forge or falsify.

As the heating means for performing the above heating, a heating roller, a far infrared lamp, laser heating,
Heating by a magnetic head or the like is used.

The heating roller is preferably one whose peripheral surface is covered with a soft member such as silicon rubber so as not to damage the surface of the diffraction grating layer or the hologram layer. Further, it is preferable that the roller diameter is set to a size capable of heating the entire heating region in one round to prevent uneven heating due to the difference between the surface temperature of the first round and the surface temperature of the second round. For example, when heating the entire length of a card with a length of 85 mm, one heating roller with a diameter of 25 mm or more can be used, or a plurality of rollers with a diameter of 5 mm or less can be arranged in the rotating direction. A roller can also be used. The surface temperature of such a heating roller is 50 to 300 ° C.
The heating roller speed is 10 to 200
mm / sec. is preferable.

The heating by the far infrared lamp is, for example, 15
It can be performed by converging and irradiating a 0 W halogen lamp with a predetermined magnetic recording width, and optionally heating the magnetic recording layer in the writing area in the range of 50 to 300 ° C. By heating with the far infrared lamp, only the magnetic recording layer can be heated without causing thermal damage to the diffraction grating layer or the hologram layer. Furthermore, by setting the focal point near the magnetic recording layer during focusing, the magnetic recording layer can be heated more efficiently.

Laser heating can be performed using a gas laser device, a solid-state laser device, a semiconductor laser device, or the like. Among these, gas lasers such as helium-neon laser, argon gas laser, carbon dioxide gas laser, and solid-state lasers such as YAG laser are particularly preferable, and the laser power is about 10 to 1000 W. Also, as will be described later, the same laser can be used when reproducing the diffraction grating or hologram at the same time as heating. In order to prevent heat damage to the light receiving element, it is preferable to dispose a light attenuation filter or a beam slitter immediately before the light receiving element. Also,
A helium-neon laser or a semiconductor laser having a laser power of about 1 to 50 mW is preferable for reproduction of the diffraction grating or hologram.

For heating by the magnetic head, the
It can be performed by heating to about 0 to 120 ° C. For heating the magnetic head, for example, there is a method of energizing a nichrome wire wound around a ring head constituting the magnetic head, or heating the magnetic head using an infrared lamp.

Next, the magnetic recording medium of the present invention will be described in more detail with reference to experimental examples. (Experimental Example 1) A 188 μm thick polyethylene terephthalate film was coated on one side with a coating solution having the following composition by a gravure coating method to form a first magnetic recording layer (thickness 15 μm) and a second magnetic recording layer. (Thickness 5 μm) was formed. The first magnetic recording layer and the second magnetic recording layer were subjected to orientation treatment with a permanent magnet having a coercive force of 10,000 Oe.

(Coating liquid for forming the first magnetic recording layer) Sr ferrite (coercive force = 6000 Oe, Curie point = 140 ° C.) ... 36 parts by weight Urethane 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 (Coating liquid for forming the second magnetic recording layer) γ-Fe ₂ O ₃ (coercive force = 300 Oe, Curie) Point = 575 ° C.) 36 parts by weight Urethane 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 Second, A coating solution having the following composition was applied onto the magnetic recording layer by a gravure coating method to form a third magnetic recording layer (thickness 5 μm). The above orientation treatment was not applied to the third magnetic recording layer.

(Coating liquid for forming third magnetic recording layer) BaFe ₁₂ O ₁₉ magnetic powder (coercive force = 17 kOe, Curie point = 450 ° C.) ... 36 parts by weight Urethane resin ... 12 parts by weight Toluene ... 20 15 parts by weight Methyl ethyl ketone 15 parts by weight Methyl isobutyl ketone 15 parts by weight Isocyanate curing agent 2 parts by weight The sheet prepared as above is punched out into a card shape of 86 mm × 54 mm and shown in FIG. The magnetic recording medium of the present invention is as follows.

Next, the magnetic recording layer of this magnetic recording medium is heated to 120 ° C. by the heat roll method, and the saturation write current value of the first magnetic recording layer and the second magnetic recording layer is set to about 60 m.
210FRPI at a write current of 80mA in the state of A
Signal was recorded. When the magnetic recording medium was cooled and then read, signals could be read well with an output of about 500 mV.

However, after the signal recorded on the above magnetic recording medium was demagnetized by using a permanent magnet with a coercive force of 10000 Oe, the signal was recorded again under the same heating and recording conditions as above, and the magnetic recording medium was cooled. After that, when reading was performed, noise was large due to the magnetic field generated in the third magnetic recording layer, and it was difficult to read the signal. (Experimental Example 2) On one surface of a polyethylene terephthalate film having a thickness of 25 μm, a coating solution for forming a peeling layer having the following composition was applied by a gravure coating method, and then the solvent was removed to remove the peeling layer (thickness: 1 μm). Was formed.

(Coating Liquid for Forming Release 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 Paratoluene sulfonic acid: 0.05 part by weight Onto this release layer, the same third layer as used in Experimental Example 1 was used.
The coating liquid for the magnetic recording layer, the coating liquid for the second magnetic recording layer, and the coating liquid for the first magnetic recording layer are applied by a gravure coating method to form a third magnetic recording layer (thickness 5 μm), A second magnetic recording layer (thickness 5 μm) and a first magnetic recording layer (thickness 15 μm) were sequentially formed. Furthermore, a coating solution for forming an adhesive layer having the following composition was applied on the first magnetic recording layer by a gravure coating method to form an adhesive layer (thickness: 5 μm) to prepare a transfer sheet.

(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 transfer sheet prepared in 1 was slit to a width of 12.7 mm to form a transfer tape, and this magnetic transfer tape was placed on polyvinyl chloride (Ohira Chemical Co., Ltd., thickness 100 μm).
The layers were superposed so that the adhesive layers were in contact with each other, and heated from the transfer tape side at 150 ° C. under the condition of 2 m / min for temporary transfer. Then, the polyester film of the transfer tape was peeled off to form a stripe in which the adhesive layer, the first magnetic recording layer, the second magnetic recording layer, and the third magnetic recording layer were laminated in this order.

Next, a hard vinyl chloride core having a thickness of 560 μm, on which characters and a pattern were previously printed by offset printing,
Thermo-compression bonding (150 ° C, 100 kg //) between the striped polyvinyl chloride film and the same striped polyvinyl chloride film as described above.
(cm ² for 10 minutes), integrated, punched out into a card shape of 86 mm × 54 mm to obtain a magnetic recording medium.

Then, the magnetic recording layer of this magnetic recording medium is heated to 120 ° C. by the heat roll method, and the saturation write current value of the first magnetic recording layer and the second magnetic recording layer is set to about 60.
210 FRP at 80 mA write current in mA
The I signal was recorded. Then, when the reading was performed after cooling the magnetic recording medium, a signal could be satisfactorily read at an output of about 400 mV.

However, after demagnetizing the signal recorded on the above magnetic recording medium using a permanent magnet with a coercive force of 10000 Oe, the signal is recorded again under the same heating / recording conditions as described above, and the magnetic recording medium is cooled. After that, when reading was performed, noise was large due to the magnetic field generated in the third magnetic recording layer, and it was difficult to read the signal. (Experimental Example 3) The third magnetic recording layer has a width of 1.0 mm and a thickness of 5 μm.
m, with a gap of 2.0 mm formed in a bar pattern,
A magnetic recording medium was prepared in the same manner as in Experimental Example 2.

Next, in the same manner as in Experimental Example 2, the magnetic stripe portion of the magnetic recording medium was heated to 120 ° C. by the heat roll method, and the saturation write current values of the first magnetic recording layer and the second magnetic recording layer were adjusted to about 120 ° C. Write current 80 at 60 mA
The signal of 210 FRPI was recorded in mA. Then, when the reading was performed after cooling the magnetic recording medium, about 40
The signal could be read well with an output of 0 mV.

However, after demagnetizing the signal recorded on the above magnetic recording medium using a permanent magnet having a coercive force of 10000 Oe, the signal is recorded again under the same heating and recording conditions as described above, and the magnetic recording medium is cooled. After that, when reading was performed, noise was large due to the magnetic field generated in the third magnetic recording layer, and it was difficult to read the signal. In this case, the magnetic field generated by the bar pattern-shaped third magnetic recording layer could be read as fixed magnetic information at an output of about 200 mV.

[0109]

As described above in detail, according to the present invention, at least one of the magnetic materials constituting the magnetic recording layer is a magnetic material having a high coercive force and a high Curie point which is not subjected to orientation treatment. Alternatively, since at least one of the magnetic recording layers having a laminated structure has a magnetic material having a high coercive force and a high Curie point and is not subjected to orientation treatment, the magnetic recording information of the magnetic recording layer has a high coercive force. When erased illegally using a magnet, a magnetic field is generated for the first time in the above high coercive force and high Curie point magnetic material, or a magnetic field is first generated in the high coercive force and high Curie point magnetic recording layer, and this magnetic field becomes noise. Therefore, it is possible to easily discriminate that the reproduction is not normally performed and the forgery or the alteration is performed.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a magnetic recording medium of the present invention.

FIG. 2 is a schematic cross-sectional view showing another example of the magnetic recording medium of the present invention.

FIG. 3 is a schematic cross-sectional view showing a magnetic field generation state of the magnetic recording medium of the present invention shown in FIG.

FIG. 4 is a schematic cross-sectional view showing another example of the magnetic recording medium of the present invention.

FIG. 5 is a schematic cross-sectional view showing another example of the magnetic recording medium of the present invention.

FIG. 6 is a schematic cross-sectional view showing another example of the magnetic recording medium of the present invention.

FIG. 7 is a schematic cross-sectional view showing another example of the magnetic recording medium of the present invention.

FIG. 8 is a schematic cross-sectional view showing another example of the magnetic recording medium of the present invention.

FIG. 9 is a schematic cross-sectional view showing an example of a magnetic transfer sheet that can be used for manufacturing the magnetic recording medium of the present invention.

[Explanation of symbols]

1, 11 ... Magnetic recording medium 2, 12 ... Base 3, 13 ... Magnetic recording layer 3a, 13a ... First magnetic recording layer 3b, 13b ... second magnetic recording layer 3c, 13c ... Third magnetic recording layer 14 ... Diffraction grating and / or hologram layer 15 ... Thin film layer

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 5/80 G11B 5/62

Claims (4)

(57) [Claims] 1. A magnetic recording medium having a substrate and a magnetic recording layer on the substrate, wherein at least one magnetic material constituting the magnetic recording layer has a high coercive force of 10,000 Oe or more, which is not subjected to orientation treatment, 300 ℃ or more of a magnetic material having a high Curie point, before
One of the other magnetic materials forming the magnetic recording layer is
They all have a high coercive force and a low Curie point, and
Coercive force of less than 10,000 Oe that has been oriented
A magnetic recording medium comprising at least one kind of magnetic material . 2. A magnetic recording medium having a substrate and a magnetic recording layer on the substrate, wherein the magnetic recording layer has a laminated structure and at least
One layer has a high coercive force of 10000 Oe or more and 300 ° C or more
It has a magnetic material with a high Curie point and is oriented.
Layer that is not included in the magnetic recording layer, and is another layer that constitutes the magnetic recording layer.
Has one layer with higher coercive force and lower Curie than the other layer.
And the magnetic material is in a relationship including a magnetic material that is a point
Is an orientation-treated coercive force of less than 10,000 Oe
Characterized by having two or more layers that are magnetic materials
Magnetic recording medium . 3. A magnetic recording medium having a substrate and a magnetic recording layer on the substrate, wherein the magnetic recording layer has a laminated structure and at least
One layer has a high coercive force of 10000 Oe or more and 300 ° C or more
It has a magnetic material with a high Curie point and is oriented.
Layer that is not included in the magnetic recording layer, and is another layer that constitutes the magnetic recording layer.
Has a higher coercive force and a lower Curie point than the other
Coercive force that is related and has been subjected to orientation treatment 10
Having a layer containing two or more magnetic materials of less than 000 Oe
A magnetic recording medium characterized by the above . 4. A high coercive force of the magnetic recording layer, the layer having a magnetic material having a high Curie point, according to claim 2 or 3, characterized in that formed in the bar pattern
The magnetic recording medium according to 1.