JP4095203B2 - Magnetic recording medium and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic recording medium, in particular, a magnetic recording medium that is difficult to forge or alter, and a method for manufacturing the same.
[0002]
[Prior art]
The magnetic recording medium in which the magnetic recording layer is formed on one side or both sides of the base material or in a stripe shape is, for example, a prepaid card, commuter pass, boarding ticket, admission ticket, car ticket, horse ticket, gift certificate, stock certificate, certificate, passbook It is widely used as gold vouchers such as magnetic tags, securities, cards such as ID cards, cash cards, credit cards, and membership cards, and magnetic labels. Conventionally, in such a magnetic recording medium, digital data is written in a magnetic recording layer at a high recording density so that recorded information cannot be easily read from the outside.
[0003]
However, because of the characteristics of the magnetic recording layer, the recorded digital data can be rewritten and erased, so it can be forged and altered, and has recently been highlighted as a major social problem. In particular, since it is easy to obtain magnetic stripes at present, it is possible to manufacture similar cards, and furthermore, when the magnetic recording layer is exposed on the surface of the magnetic recording medium as in current specifications However, there is also a problem that digital data can be easily read and the digital data can be easily transferred to another magnetic recording layer by a magnetic transfer technique.
[0004]
In order to solve the problem based on the essential drawback of the reversibility of magnetic recording information, various methods for making it difficult to rewrite the magnetic recording information have been proposed. For example, magnetic recording in which magnetic information is hardly erased by using a high coercive magnetic material such as Ba ferrite or Sr ferrite, a magnetic material having a high coercive force low Curie point (high Hc low Tc), a magnetic material containing MnBi, etc. Media etc. are being developed.
[0005]
In addition, in order to make magnetic rewriting impossible, a magnetic recording medium having magnetic recording information by applying a physical change to the magnetic layer has been developed. For example, a magnetic recording medium provided with a magnetic barcode is printed. Examples thereof include a recording medium and a magnetic recording medium in which a magnetic layer is marked with a laser or the like.
[0006]
Further, a master magnetic layer containing a magnetic material having a relatively low coercive force is formed on the substrate, and after magnetic recording is performed on the master magnetic layer, a second magnetic layer containing a magnetic material having a high coercive force is applied and formed. Laminated magnetic recording media have also been developed. In this magnetic recording medium, since the magnetic recording pattern of the master magnetic layer is copied (so-called magnetic transfer) to the second magnetic layer, it is difficult to rewrite with a magnetic head for the purpose of forgery or alteration.
[0007]
Further, a system that prevents unauthorized use by intentionally using analog data instead of digital data as magnetic recording information has been proposed (Japanese Patent Laid-Open No. 8-315355).
[0008]
[Problems to be solved by the invention]
However, magnetic recording media that simply use a high coercive force magnetic material as described above can prevent erasure of magnetic recording information due to the influence of an external magnetic field, but this is not the case when writing information with a magnetic head. Has a new problem that it is difficult to be magnetized and can be limited to the writing device.
[0009]
In addition, a magnetic recording medium having a high Hc, low Tc magnetic material or an MnBi-containing magnetic material can be used for magnetic writing under the conditions by utilizing a sudden decrease in coercive force due to temperature. Since the recorded information cannot be erased or written, there is a problem that the apparatus becomes large.
[0010]
In addition, magnetic recording media with physical changes in the magnetic layer, such as magnetic barcodes, cannot erase magnetic recording information and write new information, and can easily recognize the presence of information. This was insufficient to prevent counterfeiting.
[0011]
Further, a magnetic recording medium having magnetic recording information magnetically transferred to the second magnetic layer has a problem that when a very strong magnetic field is applied, the magnetic recording of the second magnetic layer recorded by the magnetic transfer is erased. In addition, since it is difficult to efficiently perform magnetic transfer to the second magnetic layer containing the high coercive force magnetic material, there is a problem that a magnetic output necessary for reading cannot be obtained from the second magnetic layer.
[0012]
Furthermore, the system disclosed in the above-mentioned JP-A-8-315355 prevents unauthorized use using analog data obtained from magnetic fibers randomly dispersed in a magnetic recording medium. Since it cannot be changed, it is difficult to operate complex information, and there is a problem in that it is not easy to manufacture a magnetic recording medium.
[0013]
The present invention has been made in view of such circumstances, and has information that can be varied in various ways such that the output level and waveform cannot be obtained from normal digital magnetic information in reading by a magnetic head, It is an object of the present invention to provide a magnetic recording medium that can be reliably discriminated from other magnetic recording media and that can prevent illegal acts such as forgery and tampering, and a method of manufacturing the magnetic recording medium.
[0014]
[Means for Solving the Problems]
In order to achieve such an object, the magnetic recording medium of the present invention has a base material and a magnetic recording layer provided on the base material, and the magnetic recording layer is a master magnetic layer in order from the base material side. And a coercive force of the magnetic material contained in the master magnetic layer is in the range of 300 to 6000 Oe, and the slave magnetic layer is formed by laminating two or more unit magnetic layers. Each unit magnetic layer contains magnetic materials in different density patterns In addition, among the unit magnetic layers that are in contact with each other in the stacking direction, at least one of the dense patterns of the unit magnetic layer having a high density of the dense / dense pattern is not located at the sparse / dense boundary portion of the unit magnetic layer having a low density of the dense / dense pattern. And the density ratio of the sparse / dense pattern of each unit magnetic layer excludes 0.5 and 2 The configuration is as follows.
[0015]
The magnetic recording medium of the present invention is configured such that the coercive force of the magnetic material contained in at least one of the unit magnetic layers is greater than or equal to the coercive force of the magnetic material contained in the master magnetic layer.
[0016]
The method for producing a magnetic recording medium of the present invention is a method for producing a magnetic recording medium comprising a magnetic recording layer in which a master magnetic layer and a slave magnetic layer comprising two or more unit magnetic layers are laminated on a substrate.
On substrate , The coercive force of the contained magnetic material is in the range of 300 to 6000 Oe After forming a master magnetic layer and performing desired magnetic recording on the master magnetic layer, a magnetic coating for the unit magnetic layer constituting the slave magnetic layer is applied on the master magnetic layer, and the magnetic coating film is in a predetermined direction. The magnetic material dense / dense pattern corresponding to the magnetic recording pattern of the master magnetic layer while performing the magnetic orientation treatment by the bias magnetic field, or after performing the magnetic orientation treatment, or without performing the magnetic orientation treatment. A first step of forming a first unit magnetic layer having fixed information, and a unit that performs new magnetic recording on the master magnetic layer and forms a slave magnetic layer on the unit magnetic layer that has already been formed Apply a magnetic coating for the magnetic layer and apply a magnetic orientation treatment to the magnetic coating film with a bias magnetic field in a predetermined direction, or after applying the magnetic orientation treatment, or A second step of performing at least one operation of forming a unit magnetic layer having fixed information consisting of a sparse / dense pattern of a magnetic material corresponding to the magnetic recording pattern of the master magnetic layer by drying it without any treatment. It was set as the structure which has.
[0017]
In the present invention as described above, the density patterns of the magnetic material in each of the unit magnetic layers constituting the slave magnetic layer are different from each other, and the magnetic recording layer having fixed information composed of these density patterns is formed by the magnetic head. The output waveform at the time of reading is an analog waveform in which each fixed information is superimposed.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing an example of an embodiment of the magnetic recording medium of the present invention, and FIG. 2 is a partially enlarged sectional view taken along line AA in FIG. 1 and 2, a magnetic recording medium 1 according to the present invention includes a base material 2 and a magnetic recording layer 3 provided on the base material 2. The magnetic recording layer 3 includes a master magnetic layer 4 and a slave. The magnetic layer 5 is laminated. The slave layer 5 constituting the magnetic recording layer 3 is formed by laminating a first unit magnetic layer 5a and a second unit magnetic layer 5b in this order from the master magnetic layer 4 side. The recording area 6 is set in a stripe shape.
[0019]
The substrate 2 constituting the magnetic recording medium 1 of the present invention is made of polyester such as PET, PET-G, PEN, vinyl chloride, polycarbonate, polyethylene in consideration of heat resistance, strength, rigidity, etc. required as a substrate. It is composed of a composite of a material selected appropriately from materials such as polypropylene, polystyrene, polylactic acid and the like, biodegradable resin, metal such as copper and aluminum, paper, impregnated paper, and synthetic paper. be able to. The thickness of the base material 2 can be about 100 μm to 1 mm, preferably about 150 to 250 μm.
[0020]
The master magnetic layer 4 constituting the magnetic recording layer 3 contains a magnetic material having a coercive force in the range of 300 to 6000 Oe. When the magnetic material has a coercive force of less than 300 Oe, when an orientation magnetic field is applied when the slave magnetic layer 5 is formed, the magnetic field has insufficient resistance to the orientation magnetic field, and when it exceeds 6000 Oe, stable recording by the magnetic head is possible. It becomes difficult and not preferable. It should be noted that a magnetic material having a coercive force exceeding 6000 Oe can be used if recording with a magnetic head can be performed stably.
[0021]
Examples of the magnetic material in the range of the coercive force 300 to 6000 Oe as described above constituting the master magnetic layer 4 include γ-Fe ₂ O _Three Co-coated γ-Fe ₂ O _Three , Fe _Three O _Four , CrO ₂ , Fe, Co, Ni, Fe—Co, Co—Ni, Fe—Ni, Ba ferrite, Sr ferrite and the like.
[0022]
The master magnetic layer 4 is formed by applying and drying a magnetic coating material obtained by dispersing the above magnetic fine particles in an appropriate resin or ink vehicle according to a known application method such as a gravure method, a roll method, a knife edge method, or the like. Can be formed. Moreover, the master magnetic layer 4 can also be formed by vacuum evaporation, sputtering, plating, or the like using the above magnetic material. For example, when formed by a coating method, the thickness of the master magnetic layer 4 can be 1 to 50 μm, preferably about 3 to 20 μm in terms of the film thickness after drying.
[0023]
The slave magnetic layer 5 constituting the magnetic recording layer 3 is a stack of a first unit magnetic layer 5a and a second unit magnetic layer 5b, and the first unit magnetic layer 5a is made of a predetermined magnetic material. The second unit magnetic layer 5b contains a magnetic material in a predetermined density pattern different from that of the first unit magnetic layer 5a, and each holds fixed information.
[0024]
Examples of magnetic materials constituting the first unit magnetic layer 5a and the second unit magnetic layer 5b include magnetic alloy materials made of Al, Si, Fe, etc., permalloy, sendust, Mn-Zn ferrite, Co -Zn ferrite, ferrite such as Ni-Zn ferrite, γ-Fe ₂ O _Three Co-coated γ-Fe ₂ O _Three , Fe _Three O _Four Such as iron oxide, Fe, Co, Ni, Fe-Cr, Fe-Co, Fe-Ni, Co-Cr, Co-Ni, CrO ₂ , Ba ferrite, Sr ferrite and other magnetic materials having a coercive force in the range of 1 to 10000 Oe. One of these magnetic materials is used, or a combination of two or more magnetic materials is appropriately selected. Can be used.
[0025]
In addition, at least one of the magnetic material contained in the first unit magnetic layer 5a and the magnetic material contained in the second unit magnetic layer 5b is a magnetic material whose coercive force is contained in the master magnetic layer 4. It can be the same as or larger than the coercive force. Thereby, in order to read only the variable information recorded on the master magnetic layer 4 for the purpose of alteration, the AC erasure is performed on the fixed information recorded on the first unit magnetic layer 5a and the second unit magnetic layer 5b. In this case, the magnetic information in the master magnetic layer 4 is also erased and reading is impossible.
[0026]
The first unit magnetic layer 5a is formed by applying a magnetic coating material in which the above magnetic material is dispersed in an appropriate resin or ink vehicle onto the master magnetic layer 4 on which desired magnetic recording has been performed, a gravure method, a roll method, a knife method. Apply according to a known coating method such as the edge method, and dry the magnetic coating film while performing a magnetic orientation treatment with a predetermined bias magnetic field, or after performing a magnetic orientation treatment, or without performing a magnetic orientation treatment. Can be formed.
[0027]
Then, after rewriting the magnetic information of the master magnetic layer 4 to new magnetic information, the second unit magnetic layer 5b is already provided with a magnetic paint in which the magnetic material is dispersed in an appropriate resin or ink vehicle. While applying according to a known application method such as gravure method, roll method, knife edge method, etc. on the first unit magnetic layer 5a having fixed information consisting of a dense pattern of magnetic material, and performing magnetic orientation treatment with a predetermined bias magnetic field Alternatively, it can be formed by drying the magnetic coating film after the magnetic orientation treatment or without the magnetic orientation treatment.
[0028]
In addition, as an alignment apparatus used for the alignment treatment, a solenoid type electromagnet alignment apparatus is preferable.
[0029]
The thickness of the first unit magnetic layer 5a and the second unit magnetic layer 5b is 1 to 50 μm, preferably about 3 to 20 μm, and the thickness of the slave magnetic layer 5 is 2 to 100 μm, preferably Can be about 6 to 40 μm.
[0030]
In the magnetic recording medium 1 of the present invention having such a configuration, the first unit magnetic layer 5a and the second unit magnetic layer 5b are magnetized when the recording area 6 of the magnetic recording layer 3 is read by the magnetic head. The obtained magnetic output level and waveform vary depending on the state, the presence / absence of a bias magnetic field, or its direction. For example, when normal non-bias reading without applying a bias magnetic field is performed in a state where the first unit magnetic layer 5a and the second unit magnetic layer 5b are magnetized, the density pattern of the first unit magnetic layer 5a is determined. An analog waveform obtained by synthesizing the obtained output waveform and the output waveform obtained from the second unit magnetic layer 5b is detected. This analog waveform is an output waveform that cannot be expressed by a normal magnetic recording medium.
[0031]
Further, when bias-free reading is performed after recording desired magnetic information on the master magnetic layer 4, an output waveform obtained from the master magnetic layer 4, an output waveform obtained from the dense pattern of the first unit magnetic layer 5a, and An analog waveform in which an output waveform obtained from the density pattern of the second unit magnetic layer 5b is superimposed is detected. Thereafter, even if the same magnetic information is overwritten on the master magnetic layer 4, the fixed information obtained from the first unit magnetic layer 5a and the fixed information obtained from the second unit magnetic layer 5b are completely in the same position. As described above, since magnetic information cannot be written into the master magnetic layer 4, the obtained analog waveform is different from the analog waveform before overwriting. Therefore, the information of the analog waveform obtained from the magnetic recording medium of the present invention is variable but irreversible, and is optimal for use in recording residual frequency data, for example.
[0032]
In the present invention, the ratio of the residual magnetization of the first unit magnetic layer 5a to the residual magnetization of the second unit magnetic layer 5b is preferably in the range of 0.5-2. When the residual magnetization is in such a range, the magnetic output level depends on the magnetization state of the first unit magnetic layer 5a and the second unit magnetic layer 5b, the presence / absence of a bias magnetic field, or the direction thereof. And the change of the waveform becomes clear.
[0033]
In the present invention, arbitrary variable magnetic information can be recorded in the dense portion of the magnetic material of the first unit magnetic layer 5a and the dense portion of the magnetic material of the second unit magnetic layer 5b. Arbitrary variable magnetic information can be recorded in an area outside the recording area 6 of the layer 3.
[0034]
In the above magnetic recording medium of the present invention, the slave magnetic layer 5 has a two-layer structure of the first unit magnetic layer 5a and the second unit magnetic layer 5b. However, the unit magnetic layer has three or more unit magnetic layers. There may be. Even in such a case, the density patterns of the magnetic materials of the unit magnetic layers are different from each other.
[0035]
In the magnetic recording medium of the present invention described above, the magnetic recording layer 3 is formed on the entire surface of one side of the base material. However, the magnetic recording layer 3 is formed in a stripe shape on a part of the base material 2. It may be the configuration.
[0036]
In the present invention, a protective layer, a colored layer, and a pattern for providing protection, concealment, and decorative effects may be provided on the magnetic recording layer 3 of the magnetic recording medium 1.
[0037]
Protective layer, colored layer and pattern are cellulose derivatives such as ethyl cellulose, cellulose nitrate, ethyl hydroxyethyl cellulose, cellulose acetate propionate, cellulose acetate, styrene resins such as polystyrene and poly-α-methylstyrene, styrene copolymer resins, poly Acrylic resin such as methyl methacrylate, polyethyl methacrylate, polyethyl acrylate, polybutyl acrylate or methacrylic resin, or rosin such as rosin, rosin modified maleic resin, rosin modified phenolic resin, polymerized rosin Various pigments are added to binders such as ester resin, polyvinyl acetate resin, coumarone resin, vinyl toluene resin, vinyl chloride resin, polyester resin, polyurethane resin, butyral resin according to the color to be colored. Add titanium oxide, alumina powder, microsilica, etc. as necessary to have a magnetic head cleaning effect, and if necessary, plasticizer, stabilizer, wax, grease, desiccant, drying aid, After adding a curing agent, a thickener, and a dispersing agent, using a colored paint or ink that is sufficiently kneaded with a solvent or a diluent, applying a normal gravure method, roll method, knife edge method, offset method, etc. It can be formed in a desired portion by a method or a printing method.
[0038]
Next, an embodiment of a method for producing a magnetic recording medium of the present invention will be described with reference to FIGS. 3 and 4 taking the magnetic recording medium 1 as an example.
[0039]
First, as a first step, the master magnetic layer 4 is formed on the substrate 2, and desired magnetic recording is performed on the master magnetic layer 4 (FIG. 3A). As a result, magnetic patterns having different magnetization directions are formed on the master magnetic layer 4. The master magnetic layer 4 is formed by using a magnetic coating material obtained by dispersing a magnetic material having a coercive force range of 300 to 6000 Oe in an appropriate resin or ink vehicle, such as a gravure method, a roll method, or a knife edge method. It can be formed by applying and drying according to a known application method. As the resin or ink vehicle, butyral resin, vinyl chloride / vinyl acetate copolymer resin, urethane resin, polyester resin, cellulose resin, acrylic resin, styrene / maleic acid copolymer resin, etc. are used, and if necessary, nitrile A rubber-based resin such as rubber or a urethane elastomer is added. In consideration of heat resistance, a resin having a high glass transition temperature (Tg) such as polyamide, polyimide, or polyethersulfone, or a system in which Tg is increased by a curing reaction can be used. In the magnetic coating material in which a magnetic material is dispersed in the resin or ink vehicle as described above, a dispersant, a plasticizer, a curing agent, an antistatic agent, a pigment, and the like may be appropriately contained as necessary.
[0040]
The master magnetic layer 4 can also be formed by vacuum deposition, sputtering, plating, or the like using the above magnetic material.
[0041]
Next, the first unit magnetic layer 5a is formed. First, a magnetic coating material in which a magnetic material is dispersed in an appropriate resin or ink vehicle is applied on a master magnetic layer 4 on which a desired magnetic recording has been performed, such as a gravure method, a roll method, or a knife edge method. Coating is performed according to the method to form a magnetic coating film 5'a, and then a magnetic field is applied by applying a bias magnetic field in a certain direction (FIG. 3B). As a result, the magnetic material moves and gathers at a position where the magnetization direction existing in the magnetic coating film 5'a and the direction of the bias magnetic field coincide with each other due to the lines of magnetic force generated from the master magnetic layer 4, and the undried magnetic coating film is collected. A dense portion of the magnetic material is formed in the film 5'a. The applied bias magnetic field is in the range of 150 to 3000 G, and can be appropriately set according to the magnetic material used so that the magnetic recording of the master magnetic layer 4 is not erased.
[0042]
Thereafter, the magnetic coating film 5'a is dried (may be applied with the bias magnetic field described above), so that the first information having fixed information composed of a dense pattern of magnetic material corresponding to the magnetic recording pattern of the master magnetic layer 4 is obtained. The unit magnetic layer 5a is formed (FIG. 3C). The above is the first step.
[0043]
Next, as a second step, the second unit magnetic layer 5b is formed. Here, first, new magnetic recording is performed on the master magnetic layer 4 (FIG. 4A). This magnetic recording preferably has a recording density different from the magnetic recording in the first step. With this new magnetic recording, a new magnetic pattern is formed in the master magnetic layer 4. Further, when the magnetic material contained in the first unit magnetic layer 5a has a coercive force that can be magnetized by the magnetic recording on the master magnetic layer 4, the first unit magnetic layer 5a is also magnetized at the same time. The
[0044]
Next, a magnetic paint in which a magnetic material is dispersed in an appropriate resin or ink vehicle is applied to the first unit magnetic layer 5a having a dense pattern of the magnetic material by a gravure method, a roll method, a knife edge method, or the like. Coating is performed according to a known coating method to form a magnetic coating film 5'b, and then a magnetic field is applied by applying a bias magnetic field in a certain direction (FIG. 4B). Due to the application of the bias magnetic field, the magnetic material moves and gathers at a site where the magnetization direction existing in the magnetic coating film 5 ′ b matches the direction of the bias magnetic field due to the magnetic field lines generated from the master magnetic layer 4, and is not dried. A dense portion of the magnetic material is formed in the magnetic coating film 5'b. The applied bias magnetic field is in the range of 150 to 3000 G, and can be appropriately set according to the magnetic material used so that the magnetic recording of the master magnetic layer 4 is not erased.
[0045]
Then, the second unit magnetism having fixed information consisting of a dense pattern corresponding to the magnetic recording pattern of the master magnetic layer 4 is obtained by drying the magnetic coating film 5'b (or while applying the bias magnetic field). The layer 5b is formed (FIG. 4C). As described above, when the first unit magnetic layer 5a is also magnetized by the new magnetic recording on the master magnetic layer 4, the fixed information of the second unit magnetic layer 5b is the first unit magnetic layer. This is a complicated one reflecting the influence of the fixed information 5a. The above is the second step.
[0046]
Next, a bias magnetic field that erases the magnetic recording of the master magnetic layer 4 is applied in a certain direction to erase the magnetic recording of the master magnetic layer 4, and the fixed information and the second information of the first unit magnetic layer 5a. The fixed information of the unit magnetic layer 5b is magnetized to obtain the magnetic recording medium 1.
[0047]
In the magnetic recording medium 1 of the present invention manufactured as described above, fixed information in the first unit magnetic layer 5a in the slave magnetic layer 5 of the magnetic recording layer 3 and fixed information in the second unit magnetic layer 5b are stored. Since the magnetic material is formed in a sparse pattern formed by moving the magnetic material in an undried magnetic coating film, it is not erased even when a strong magnetic field is applied. The magnetic output waveform when read by the magnetic head varies depending on the magnetization state of the first unit magnetic layer 5a and the second unit magnetic layer 5b, the presence or absence of a bias magnetic field, or the direction thereof. For example, in the state where the magnetic material contained in the first unit magnetic layer 5a and the magnetic material contained in the second unit magnetic layer 5b are uniformly magnetized, a normal non-bias without applying a bias magnetic field is applied. When reading is performed, an analog waveform obtained by synthesizing the output waveform obtained from the dense pattern of the first unit magnetic layer 5a and the output waveform obtained from the second unit magnetic layer 5b is detected.
[0048]
In the present invention, the fixed information in the first unit magnetic layer 5 a and the fixed information in the second unit magnetic layer 5 b are arbitrarily set for each magnetic recording medium by magnetic recording on the master magnetic layer 4. Therefore, it can be distinguished from other magnetic recording media.
[0049]
In the method for producing a magnetic recording medium of the present invention, in at least one of the first step and the second step, the magnetic coating film may be dried to form a slave magnetic layer without applying a magnetic orientation treatment. . In this case, in the undried magnetic coating film, the magnetic material moves and gathers at the boundary portion in the magnetization direction where the magnetic lines of force generated from the master magnetic layer 4 are dense, and thereby the magnetic material is dense in the magnetic coating film. A part is generated, and a dense pattern is formed.
[0050]
Also, a magnetic recording medium having three or more unit magnetic layers constituting the slave magnetic layer can be manufactured by repeating the second step described above.
[0051]
A magnetic tape is obtained by using a resin film such as a polyethylene terephthalate film as a base material, and sequentially laminating a master magnetic layer and a slave magnetic layer on the base material by the manufacturing method as described above. The magnetic tape may be bonded to the entire surface or a part of the card substrate or the like to manufacture a magnetic recording medium.
[0052]
【Example】
Next, an Example is shown and this invention is demonstrated further in detail.
[0053]
Example 1
First, as a base material, 188 μm thick polyethylene terephthalate (E-22 manufactured by Toray Industries, Inc.) was prepared. It was applied and dried to form a master magnetic layer having a thickness of 10 μm.
[0054]
(Coating liquid for forming the master magnetic layer)
・ Ba ferrite (coercive force = 2000 Oe): 80 parts by weight
・ Vinyl chloride / vinyl acetate copolymer resin: 10 parts by weight
・ Urethane resin: 10 parts by weight
・ Methyl ethyl ketone: 50 parts by weight
・ Toluene: 50 parts by weight
・ Methyl isobutyl ketone: 50 parts by weight
・ Isocyanate curing agent: 3 parts by weight
[0055]
Next, magnetic recording D1 was performed on the master magnetic layer at a write current of 1000 mA. The recording density at this time was 200 bpi (FM recording).
[0056]
Next, a magnetic coating film was formed on the master magnetic layer by applying a magnetic coating material for forming a unit magnetic layer having the following composition by a gravure coating method.
[0057]
(Coating solution for unit magnetic layer formation)
・ Γ-Fe ₂ O _Three (Coercive force = 300 Oe) ... 80 parts by weight
・ Vinyl chloride / vinyl acetate copolymer resin: 10 parts by weight
・ Urethane resin: 10 parts by weight
・ Methyl ethyl ketone: 50 parts by weight
・ Toluene: 50 parts by weight
・ Methyl isobutyl ketone: 50 parts by weight
・ Isocyanate curing agent: 3 parts by weight
[0058]
Next, a magnetic orientation treatment was performed on the magnetic coating film by applying a DC bias magnetic field by a 1200 G solenoid in one direction along the recording direction of the master magnetic layer. Thereafter, the magnetic unit was dried to form a first unit magnetic layer having a thickness of 5 μm. This first unit magnetic layer had fixed information D1 ′ consisting of a dense pattern of magnetic material corresponding to the magnetic recording D1 of the master magnetic layer. (End of the first step)
[0059]
Next, magnetic recording D2 was performed on the master magnetic layer at a write current of 1000 mA. The recording density at this time was 170 bpi (FM recording). By the magnetic recording, the first unit magnetic layer is magnetized at the same time.
[0060]
Next, on the first unit magnetic layer, the magnetic coating material for forming the unit magnetic layer was applied by a gravure coating method to form a magnetic coating film.
[0061]
Next, a magnetic orientation treatment was performed on the magnetic coating film by applying a DC bias magnetic field by a 1200 G solenoid in one direction along the recording direction of the master magnetic layer. Thereafter, the magnetic unit was dried to form a second unit magnetic layer having a thickness of 4 μm. The second unit magnetic layer has fixed information (D2 + D1 ′) ′ composed of a dense pattern of magnetic material corresponding to the magnetic recording D2 of the master magnetic layer and the fixed information D1 ′ of the first unit magnetic layer. there were. (End of second step)
[0062]
As a result, a magnetic recording layer composed of a master magnetic layer and a laminate of a slave magnetic layer in which the first unit magnetic layer and the second unit magnetic layer were laminated was formed on the substrate.
[0063]
The base material on which the magnetic recording layer was formed as described above was punched into a card shape having a size of 86 mm × 54 mm to obtain the magnetic recording medium of the present invention.
[0064]
Next, a DC bias magnetic field of 15000 G by a solenoid is applied to the magnetic recording layer of the magnetic recording medium in one direction along the recording direction of the master magnetic layer to erase the magnetic recording D2 of the master magnetic layer, and the first Magnetization was performed on the fixed information D1 ′ portion composed of the density pattern of the magnetic material of the unit magnetic layer and the fixed information (D2 + D1 ′) ′ portion composed of the density pattern of the magnetic material of the second unit magnetic layer.
[0065]
As a result of reading this magnetic recording medium using a card reader without a bias magnetic field, an analog output waveform in which fixed information D1 ′ and fixed information (D2 + D1 ′) ′ are superimposed is obtained.
[0066]
From this, the fixed information of the first unit magnetic layer and the fixed information of the second unit magnetic layer constituting the slave magnetic layer of the magnetic recording medium of the present invention can be used as magnetic information that cannot be magnetically erased, and It was confirmed that the analog magnetic output on which the fixed information is superimposed cannot be expressed by a normal magnetic recording medium.
[0067]
(Example 2)
In the same manner as in Example 1, a magnetic recording layer composed of a master magnetic layer and a laminate of a slave magnetic layer in which a first unit magnetic layer and a second unit magnetic layer are laminated is formed on a substrate. The magnetic recording medium of the present invention was obtained by punching into a card shape having a size of 86 mm × 54 mm.
[0068]
Next, a DC bias magnetic field of 15000 G by a solenoid is applied to the magnetic recording layer of the magnetic recording medium in one direction along the recording direction of the master magnetic layer to erase the magnetic recording D of the master magnetic layer, and the first Magnetization was performed on the fixed information D1 ′ portion consisting of the density pattern of the magnetic material of the unit magnetic layer and the fixed information (D2 + D1 ′) ′ portion consisting of the density pattern of the magnetic material of the second unit magnetic layer.
[0069]
Next, another magnetic recording D3 was performed on the master magnetic layer on the same track at a write current of 1000 mA. The recording density at this time was 140 bpi (FM recording). As a result of reading this magnetic recording medium using a card reader without a bias magnetic field, an analog output waveform P in which fixed information D1 ′, fixed information (D2 + D1 ′) ′, and magnetic recording D3 are superimposed is obtained.
[0070]
Next, magnetic recording D3 was performed again on the master magnetic layer on the same track under the same conditions as described above. As a result of reading this magnetic recording medium using a card reader without a bias magnetic field, an analog output waveform P ′ in which fixed information D1 ′, fixed information (D2 + D1 ′) ′, and magnetic recording D3 are superimposed is obtained. This is different from the analog output waveform P described above.
[0071]
From this, it was confirmed that the information of the analog waveform obtained from the magnetic recording medium of the present invention is variable but irreversible, and is optimal for use in recording residual frequency data, for example.
[0072]
(Example 3)
First, a master magnetic layer was formed in the same manner as in Example 1, and magnetic recording D1 was performed on the master magnetic layer at a write current of 1000 mA. The recording density at this time was 200 bpi (FM recording).
[0073]
Next, a magnetic coating film was formed by applying a magnetic paint for forming a first unit magnetic layer having the following composition on the master magnetic layer by a gravure coating method.
[0074]
(Coating liquid for forming the first unit magnetic layer)
・ Γ-Fe ₂ O _Three (Coercive force = 300 Oe) ... 80 parts by weight
・ Vinyl chloride / vinyl acetate copolymer resin: 10 parts by weight
・ Urethane resin: 10 parts by weight
・ Methyl ethyl ketone: 50 parts by weight
・ Toluene: 50 parts by weight
・ Methyl isobutyl ketone: 50 parts by weight
・ Isocyanate curing agent: 3 parts by weight
[0075]
Next, the above-mentioned magnetic coating film was dried to form a first unit magnetic layer having a thickness of 5 μm. The first unit magnetic layer has fixed information D1 ″ consisting of a dense pattern of magnetic material corresponding to the magnetic recording D1 of the master magnetic layer (the first step).
[0076]
Next, magnetic recording D2 was performed on the master magnetic layer at a write current of 1000 mA. The recording density at this time was 170 bpi (FM recording). By the magnetic recording, the first unit magnetic layer is magnetized at the same time.
[0077]
Next, a magnetic coating film was formed by applying a magnetic paint for forming a second unit magnetic layer having the following composition on the first unit magnetic layer by a gravure coating method.
[0078]
(Coating solution for forming the second unit magnetic layer)
・ Ba ferrite (coercive force = 5000 Oe): 80 parts by weight
・ Vinyl chloride / vinyl acetate copolymer resin: 10 parts by weight
・ Urethane resin: 10 parts by weight
・ Methyl ethyl ketone: 50 parts by weight
・ Toluene: 50 parts by weight
・ Methyl isobutyl ketone: 50 parts by weight
・ Isocyanate curing agent: 3 parts by weight
[0079]
Next, a magnetic orientation treatment was performed on the magnetic coating film by applying a DC bias magnetic field by a 1200 G solenoid in one direction along the recording direction of the master magnetic layer. Thereafter, the magnetic unit was dried to form a second unit magnetic layer having a thickness of 4 μm. The second unit magnetic layer has fixed information (D2 + D1 ″) ′ composed of a dense pattern of magnetic material corresponding to the magnetic recording D2 of the master magnetic layer and the fixed information D1 ″ of the first unit magnetic layer. there were. (End of second step)
[0080]
Thus, a magnetic recording layer composed of a master magnetic layer and a laminate of the slave magnetic layer in which the first unit magnetic layer and the second unit magnetic layer were laminated was formed on the substrate.
[0081]
The base material on which the magnetic recording layer was formed as described above was punched into a card shape having a size of 86 mm × 54 mm to obtain the magnetic recording medium of the present invention.
[0082]
Next, a DC bias magnetic field of 15000 G by a solenoid is applied to the magnetic recording layer of the magnetic recording medium in one direction along the recording direction of the master magnetic layer to erase the magnetic recording D2 of the master magnetic layer, and the first Magnetization was performed on the fixed information D1 ″ portion consisting of the density pattern of the magnetic material of the unit magnetic layer and the fixed information (D2 + D1 ″) ′ portion consisting of the density pattern of the magnetic material of the second unit magnetic layer.
[0083]
As a result of reading this magnetic recording medium using a card reader without a bias magnetic field, an analog output waveform in which fixed information D1 ″ and fixed information (D2 + D1 ″) ′ are superimposed is obtained.
[0084]
From this, the fixed information of the first unit magnetic layer and the fixed information of the second unit magnetic layer constituting the slave magnetic layer of the magnetic recording medium of the present invention can be used as magnetic information that cannot be magnetically erased, and Thus, it was confirmed that the analog magnetic output on which the fixed information is superimposed cannot be expressed by a normal magnetic recording medium.
[0085]
【The invention's effect】
As described above in detail, according to the present invention, the magnetic recording layer provided on the base material is obtained by laminating the master magnetic layer and the slave magnetic layer on the base material in this order, and constitutes the slave magnetic layer. Since the density patterns of the magnetic material in each unit magnetic layer above the layer are different from each other, the waveform of the magnetic output obtained by reading the magnetic recording layer having the fixed information composed of these density patterns with the magnetic head is as follows. The superposed analog waveform can be distinguished from other magnetic recording media, and the authenticity of the magnetic recording media can be reliably determined. Also, by recording variable information in the dense portion of the unit magnetic layer constituting the master magnetic layer and the slave magnetic layer, an analog waveform in which this variable information and the above fixed information are superimposed is obtained as an output waveform. The output waveform in this case is irreversible and cannot be reproduced when the variable information is overwritten, and can be used for recording the remaining frequency data.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of an embodiment of a magnetic recording medium of the present invention.
2 is a partially enlarged cross-sectional view taken along line AA in FIG.
FIG. 3 is a process diagram showing an example of an embodiment of a method for producing a magnetic recording medium of the present invention.
FIG. 4 is a process diagram showing an example of an embodiment of a method for producing a magnetic recording medium of the present invention.
[Explanation of symbols]
1 ... Magnetic recording medium
2 ... Base material
3 ... Magnetic recording layer
4. Master magnetic layer
5 ... Slave magnetic layer
5a: first unit magnetic layer
5b ... Second unit magnetic layer

Claims (3)

A base material and a magnetic recording layer provided on the base material, wherein the magnetic recording layer is formed by laminating a master magnetic layer and a slave magnetic layer in order from the base material side. The coercive force of the contained magnetic material is in the range of 300 to 6000 Oe, the slave magnetic layer is formed by laminating two or more unit magnetic layers, and each unit magnetic layer contains the magnetic material in different density patterns In addition, among the unit magnetic layers that are in contact with each other in the stacking direction, at least one of the dense patterns of the unit magnetic layer having a high density of the dense / dense pattern is not located at the sparse / dense boundary portion of the unit magnetic layer having a low density of the dense / dense pattern A magnetic recording medium characterized in that the density ratio of the density patterns of each unit magnetic layer is less than 0.5 and 2 .   2. The magnetic recording medium according to claim 1, wherein the coercive force of the magnetic material contained in at least one of the unit magnetic layers is equal to or greater than the coercive force of the magnetic material contained in the master magnetic layer. In a method for producing a magnetic recording medium comprising a magnetic recording layer in which a master magnetic layer and a slave magnetic layer composed of two or more unit magnetic layers are laminated on a substrate,
A master magnetic layer having a coercive force of a magnetic material contained in the range of 300 to 6000 Oe is formed on the substrate, and desired magnetic recording is performed on the master magnetic layer. Apply the magnetic coating for the unit magnetic layer that constitutes the slave magnetic layer, and apply the magnetic orientation treatment to the magnetic coating film with the bias magnetic field in the specified direction, or after the magnetic orientation treatment, or after the magnetic orientation treatment. A first step of forming a first unit magnetic layer having fixed information consisting of a dense pattern of magnetic material corresponding to the magnetic recording pattern of the master magnetic layer by drying without applying;
A new magnetic recording is performed on the master magnetic layer, and a magnetic coating for the unit magnetic layer constituting the slave magnetic layer is applied on the unit magnetic layer that has already been formed. Fixed information consisting of a dense pattern of magnetic material corresponding to the magnetic recording pattern of the master magnetic layer while being subjected to orientation treatment, or after being subjected to magnetic orientation treatment, or dried without being subjected to magnetic orientation treatment. And a second step of performing the operation of forming the unit magnetic layer having one or more times.

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