JPH09115136A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it difficult to forge or alter a medium by forming a fixation pattern of the same materials as the magnetic materials which constitute a magnetic layer for recording and reproducing variable information, and forming the both integrally. SOLUTION: On the entire surface or a part of the surface of a base body 2, 1st and 2nd magnetic layers 3A and 3B are laminated in order which are formed out of the same magnetic materials that enable magnetic recording and reproduction. At least, a part of the 2nd magnetic layer 3B, the unrewritable fixed pattern 4 is recorded which is formed under the effect of a magnetic field based upon a signal recorded in the 1st magnetic layer 3A, and an oriented magnetic field. This unrewritable fixed pattern 4 which is recorded in the 2nd magnetic layer 3B has parts 4A where magnetic particles exist densely and parts 4B where magnetic particles exist sparsely formed adjacently and alternately corresponding to the direction of the magnetism of the signal recorded in the 1st magnetic layer 3A. The figure shows a plan view of the magnetic recording medium and cross-section view of parts along X-X and Y-Y of the plan view.

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 such as a prepaid card which is required to have high security against forgery and alteration, and a method for producing the same, and in particular, the same magnetic coating is laminated. The present invention relates to a magnetic recording medium which is formed by coating and has a non-rewritable fixed pattern formed in a part of the magnetic layer, and a manufacturing method thereof.

[0002]

2. Description of the Related Art With the spread of magnetic cards such as prepaid cards that have rapidly spread in recent years, there is a strong demand for safety against illegal acts such as forgery and alteration. As a means for improving the safety of a magnetic card, it has been proposed to provide a fixed pattern, which is difficult to rewrite, as identification information peculiar to the medium, in a place different from the normal magnetic recording / reproducing area. Specifically, as disclosed in Japanese Patent Publication No. 49-37529, a method of providing a magnetic pattern by regularly changing the arrangement direction of the easy axis of magnetization of the needle-shaped magnetic powder with respect to the reading direction of the medium, As disclosed in Japanese Unexamined Patent Publication No. 50-79311, the orientation of magnetic particles dominated by information in the lower layer is obtained by applying a magnetic paint in which magnetic particles are dispersed under the action of a signal magnetic field magnetically recorded in a normal magnetic layer. To physically fix the slab, JP-A-7-
As disclosed in Japanese Patent No. 29157, by applying a magnetic paint in which magnetic particles having a coercive force of 100 Oe or less are dispersed on a magnetic layer on which magnetic recording is performed, the magnetic particles are concentrated on the magnetic reversal portion of the signal recording pattern. As described in Japanese Patent Application Laid-Open No. 5-318974, the information magnetically recorded in the ordinary magnetic layer is laminated on the magnetic layer to have a high coercive force of 4500 Oe or more. There is known a method of transferring information to a medium, which is difficult to be rewritten by a magnetic head which is normally used, by transferring the information to a magnetic layer having particles.

[0003]

However, the magnetic recording medium disclosed in Japanese Patent Publication No. Sho 49-37529 has a drawback that a sufficient read output cannot be obtained, and a special device for manufacturing or reading is used. Since it requires parts, it has the drawback of increasing the manufacturing cost and the cost of the reading device. On the other hand, in JP-A-50-79311, JP-A-7-29157 and JP-A-5-318974, the fixed pattern is formed in a low coercive force magnetic layer of 100 Oe or less or 4500 Oe or more in which magnetic recording / reproduction is difficult. Is formed in the high coercive force magnetic layer, and a magnetic layer having a coercive force different from that of the magnetic layer is laminated on the magnetic layer for magnetic recording and reproduction.

FIG. 7 is a cross-sectional view showing the structure of a medium according to this conventional technique. The first magnetic layer 3 for magnetic recording / reproduction on the substrate 2 and the first magnetic layer 3 have a coercive force. Different second magnetic layers 6 are sequentially stacked, and the second magnetic layer 6 is provided with a non-rewritable fixed signal track 4 in which fixed information for identifying a medium is recorded. 3 is provided with a magnetic recording / reproducing track 5 for recording / reproducing variable information. In the above-mentioned medium according to the related art, the second magnetic layer 6 for forming the fixed pattern is
Since the first magnetic layer 3 is entirely provided on the first magnetic layer 3, the second magnetic layer 6 serves as a spacing for the first magnetic layer 3 and affects the recording / reproduction of variable information. Therefore,
There is a problem that the thickness of the second magnetic layer 6 cannot be increased, so that the read output of the fixed pattern cannot be sufficiently obtained. In order to avoid the magnetic recording / reproducing track 5 and to provide the second magnetic layer 6 only on the fixed signal track 4, the manufacturing method of the entire surface coating method as when forming the first magnetic layer 3 is used. Cannot be used, and it is necessary to add an extra step other than the step of manufacturing an ordinary magnetic recording medium, such as coating in a stripe shape or partial printing, which is a drawback that the manufacturing process becomes complicated. Further, since the presence of the fixed signal track 4 can be visually recognized, there is a problem in terms of safety. The present invention has been made in view of the above problems, and a magnetic recording medium in which an unrewritable fixed pattern is integrally formed in a magnetic layer capable of magnetic recording and reproduction by using the same material as the magnetic layer. And a method of manufacturing the same.

[0005]

In order to solve the above-mentioned problems, the present invention has first and second magnetic layers made of the same magnetic material capable of magnetic recording and reproduction on the whole or a part of a substrate. In a magnetic recording medium which is sequentially laminated and applied, at least a part of the second magnetic layer is a non-rewritable fixed pattern formed by the influence of a magnetic field and a magnetic field due to a signal recorded in the first magnetic layer. There is provided a magnetic recording medium characterized by being recorded. Such a non-rewritable fixed pattern is formed by alternately forming a dense portion and a sparse portion of the magnetic particles adjacent to each other in accordance with the magnetization direction of the signal recorded in the first magnetic layer. Can be recorded.

The present invention is also the method of manufacturing a magnetic recording medium as described above, wherein a first magnetic layer made of a magnetically recordable magnetic material is first formed on a substrate, and then a predetermined magnetic layer is formed on the first magnetic layer. A signal is recorded, and then a magnetic paint made of the same magnetic material as that of the first magnetic layer is applied. Before the magnetic paint is dried and solidified, the magnetic field strength is such that the signal recorded in the first magnetic layer is not attenuated. And subjecting the magnetic coating material to an orientation treatment with an orientation magnetic field whose direction is substantially parallel to and substantially constant with respect to the direction of the residual magnetization of the signal recorded in the first magnetic layer, and thereafter the magnetic coating material is dried and solidified. Thereby forming a second magnetic layer including at least a part of the non-rewritable fixed pattern formed by the influence of the magnetic field due to the signal recorded in the first magnetic layer and the orientation magnetic field. Made of medium To provide a method.

[0007]

In the present invention, the non-rewritable fixed pattern is formed in the second magnetic layer of the first and second magnetic layers made of the same magnetic material. For that purpose, first, a first magnetic layer is formed, and a signal for producing a fixed pattern, which is alternately magnetized with different polarities, is magnetically recorded therein. Then, the same magnetic coating material as that for the first magnetic layer is applied onto the first magnetic layer, and an orientation magnetic field in a predetermined direction is applied before drying. Where the direction of the signal magnetic field generated from the signal recorded in the first magnetic layer and the direction of the orientation magnetic field are the same, the two are added together to increase the strength of the magnetic field applied to the second magnetic layer, while At locations where the directions are opposite, the magnetic fields of the two cancel each other out, and the strength of the magnetic field applied to the second magnetic layer becomes weak. At that time, the magnetic particles in a fluidized state concentrate from a weak magnetic field to a strong magnetic field. When dried in this state, in the second magnetic layer, a portion where the magnetic particles are dense and a portion where the magnetic particles are sparse are alternately adjacent to each other in accordance with the direction of the magnetization of the signal magnetic field recorded in the first magnetic layer. It is formed. In this way, the signal pattern recorded in the first magnetic layer is reproduced as a fixed pattern due to the density of the magnetic particles in the second magnetic layer. Since this fixed pattern is formed as a difference in the physical structure of the magnetic layer, it cannot be erased or rewritten by a magnetic head or the like. On the other hand, the magnetic recording / reproducing track is formed in a portion other than the fixed pattern, but since the first magnetic layer and the second magnetic layer are formed of the same magnetic material, there is no problem in magnetic recording / reproducing. Absent. Since the reproduction output obtained from the fixed pattern portion depends on the thickness of the second magnetic layer, it is fixed by appropriately setting the ratio of the total thickness of the magnetic layer and the thickness of the first and second magnetic layers. The output of both the pattern and the magnetic recording / reproducing track can be properly determined.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a plan view showing an example of a magnetic recording medium used in the present invention. 2 is a sectional view of a portion taken along line XX of FIG. 1, and FIG. 3 is a sectional view of a portion taken along line YY. 1 to 3, a magnetic recording medium 1 is formed by sequentially stacking a first magnetic layer 3A and a second magnetic layer 3B made of the same magnetic material on a substrate 2. A fixed signal track 4 having a fixed pattern for identifying a medium is provided on a part of the second magnetic layer 3B, and on the first magnetic layer 3A and a part of the second magnetic layer 3B. A magnetic recording / reproducing track 5 for magnetic recording / reproducing is provided. On the fixed signal track 4, dense portions 4A and sparse portions 4B of magnetic particles are alternately formed with a predetermined length.

FIG. 4 is a schematic view showing an example of a method of manufacturing the magnetic recording medium of the present invention. In the figure, 10 is an unwinding device for sending out the substrate 2 wound in a roll shape, 11
Is a first coating head, 12 is a magnetic paint for forming a first magnetic layer, 13 is a first aligning device for performing an alignment treatment on the first magnetic layer, and 14 is a first magnetic layer. Is a first drying device for drying and solidifying the liquid, 15 is a magnetic head for writing a signal for creating a fixed pattern on the first magnetic layer, 16 is a second coating head, and 17 is a second magnetic layer. A magnetic paint for forming a layer, 18 a second aligning device for forming a fixed pattern on the second magnetic layer, 19 a second drying device for drying and solidifying the second magnetic layer, 20 Is the first
And a winding device for winding the substrate coated with the second magnetic layer.

The magnetic recording medium 1 of the present invention can be manufactured by the following method. The first coating head 11 applies the magnetic coating material 12 to the base body 2 sent out from the unwinding device 10, and then, for example, a first orienting device 13 in which permanent magnets of the same polarity are closely arranged to face each other. Alignment treatment is performed, and then the first drying device 14 dries and solidifies the first
Magnetic layer 3A is formed. In the first magnetic layer 3A,
A predetermined signal is magnetically recorded by the magnetic head 15. Then the second
The magnetic coating material 16 is applied by the coating head 16 of the second alignment device 1, and immediately after that, the second orientation device 1 including, for example, a solenoid coil.
8, parallel to the direction of remanent magnetization of the signal recorded in the first magnetic layer 3A (in the case of FIG. 4, parallel to the coated surface)
Then, an orienting magnetic field in a substantially constant direction is applied. Then the second
When the magnetic coating material 17 is dried and solidified by the drying device 19, the second magnetic layer 3B is separated from a portion where the presence of magnetic particles becomes dense according to the direction and length of the magnetization of the signal recorded in the first magnetic layer 3A. Are formed alternately. Then the first
The substrate 2 on which the second magnetic layer is formed is the winding device 2
Wound to zero.

FIGS. 5A to 5D are diagrams for explaining in detail the process of forming a non-rewritable fixed pattern on the magnetic recording medium according to the present invention. FIG. 5 (A)
FIG. 4 is a diagram showing a magnetization state of the first magnetic layer 3A and a read waveform thereof after recording a signal for producing a fixed pattern on the first magnetic layer 3A. This signal is magnetically recorded by using a magnetic head so that the direction of the residual magnetization is always inverted alternately as shown by the solid line arrow in the figure. The encoding method of the recording signal needs to be a method in which magnetization reversal always exists in a predetermined length for the reason described later, and FM, PM, MFM, etc. are generally used depending on the recording density. It When this recording signal is read by the ring type magnetic head, positive and negative pulses are alternately generated at the location where the magnetization of the recording signal is inverted as shown in the figure. FIG. 5B shows
Apply the magnetic paint 17 from above the first magnetic layer 3A,
It is the figure which showed typically the direction of the magnetic field added to the 2nd magnetic layer 3B when the orientation magnetic field of a predetermined direction (indicated by the arrow pointing to the right in the figure) is applied before drying. Reference number 4A '
At the point, since the direction of the orientation magnetic field and the direction of the signal magnetic field generated from the signal recorded in the first magnetic layer 3A coincide with each other, the two are added together to increase the magnetic field strength. At the reference numeral 4B ', the orientation magnetic field and the signal magnetic field have opposite directions, so that the respective magnetic fields cancel each other and the magnetic field strength applied to the second magnetic layer 3B becomes small. That is, in the second magnetic layer 3B, a strong magnetic field portion 4A 'and a weak magnetic field portion 4B' appear alternately according to the magnetization direction of the signal recorded in the first magnetic layer 3A. Magnetic particles in a flowing state concentrate from weak magnetic field to strong magnetic field.
As shown in FIG. 5C, the magnetic particles in the second magnetic layer move from the weak magnetic field portion 4B ′ to the strong magnetic field portion 4A ′, and as a result, the second magnetic layer 3B has the first magnetic particle Magnetic layer 3A
The dense and sparse portions of the magnetic particles are alternately formed according to the magnetization direction of the signal recorded in the above. In this state, the magnetic paint 17 is dried and solidified, and then the first magnetic layer 3A is formed.
When the signal recorded in No. 2 is erased, as shown in FIG. 5D, the second magnetic layer 3B having a fixed pattern due to the density of magnetic particles is formed. Since the lengths of the dense portion (4A) and the sparse portion (4B) are formed corresponding to the lengths of the magnetization directions of the signals recorded in the first magnetic layer 3A, respectively. The above-mentioned FM,
When PM, MFM, or the like is used, a fixed pattern encoded by the difference in length between the dense portion (4A) and the sparse portion (4B) is formed. As shown in FIG. 5D, the read waveform of this fixed pattern is dense to sparse and sparse to dense at the boundary between the portion (4A) where the magnetic particles are dense and the portion (4B) where the magnetic particles are dense. The positive and negative pulses are alternately generated according to. As is clear from the figure, the boundary between the dense portion (4A) and the sparse portion (4B) of the magnetic particles coincides with the magnetization reversal portion of the signal recorded in the first magnetic layer 3, so that this waveform is The waveform is substantially similar to the read waveform from the signal recorded in the first magnetic layer 3A shown in FIG. 5 (A).

As described above, the fixed pattern formed on the second magnetic layer 3B is determined by the strength of the combined magnetic field of the signal magnetic field recorded on the first magnetic layer 3A and the orientation magnetic field applied from the outside. Therefore, when the magnetization reversal interval of the signal recorded in the first magnetic layer 3A is wide, the signal magnetic field strength becomes weak at a position away from the magnetization reversal portion, and the recording signal when the orientation magnetic field is applied. The difference in the combined magnetic field strength due to the difference in the magnetization direction of is reduced. As a result, the magnetic particles concentrate only near the magnetization reversal portion. When the magnetization reversal interval is within 1 mm when the orientation magnetic field is applied, a significant difference in the composite magnetic field strength between the magnetization reversal portions and the position between the adjacent magnetization reversal portions appears remarkably at any place. Therefore, in the present invention, the magnetization reversal interval of the signal to be recorded in the first magnetic layer 3A, that is, the reading direction of the portion where the content of the magnetic particles formed in the second magnetic layer is dense and the portion where the magnetic particles are sparse The length is preferably within 1 mm.

As is clear from the above description, in the manufacturing method shown in FIG. 4, the second aligning device 18 used when applying the second magnetic layer 3B is aligned while passing through the device. It is desirable that the direction of the magnetic field is substantially parallel to the direction of the residual magnetization of the signal recorded in the first magnetic layer 3A and is substantially constant until it is dried and solidified. In the case of the parallel direction (longitudinal recording), it is preferable to use a solenoid coil. Also, the first
When the direction of the residual magnetization of the signal recorded in the magnetic layer 3A is perpendicular to the coated surface (perpendicular recording), or has a magnetization component in the perpendicular direction as well, the permanent magnets in which the different poles are closely arranged to face each other. Can be used. Furthermore, at least a part of the second orientation device 18 may be provided in the second drying device 19. In the above description, an example in which the first magnetic layer 3A and the second magnetic layer 3B are continuously formed by the magnetic recording medium manufacturing apparatus having two coating sections and two drying apparatuses has been described. However, the present invention is not limited to this, and the first magnetic layer 3A and the second magnetic layer 3B may be formed independently. In this case, when recording a signal on the first magnetic layer 3A, the first magnetic layer 3A is coated / coated.
It may be performed immediately after being dried, or may be performed immediately before applying the second magnetic layer 3B. Also, only the step of recording the signal may be provided independently.

Now, materials constituting the magnetic recording medium of the present invention will be described. As the substrate 2, known materials for magnetic cards and magnetic sheets such as polyethylene terephthalate (PET), hard vinyl chloride resin (PVC), plastic film and paper such as synthetic paper, resin-impregnated paper and the like can be used. The first magnetic layer 3A and the second magnetic layer 3B are made of the same magnetic material, and the magnetic particles in the paint are easily magnetized by the influence of the magnetic field and the orientation magnetic field generated from the signal recorded in the first magnetic layer 3A. ΓFe ₂ O
A magnetic paint prepared by dispersing a known recording magnetic material such as ₃ , Fe ₃ O ₄ , CrO ₂ , Co deposited γFe ₂ O ₃ , metal powder, barium ferrite, strontium ferrite in a polymer resin binder, Each layer is formed by a known method so that the film thickness after drying is about 4 to 15 μm. However, the coercive force of these magnetic materials is
It is necessary that the signal recorded in the first magnetic layer 3A is not attenuated or erased by the influence of the orientation magnetic field applied when forming the second magnetic layer 3B. But 20
Even in an orientation magnetic field of about 0 Oe, if the fluidity of the magnetic particles in the coating material is high, or if the orientation magnetic field is continuously applied for a sufficient time for the magnetic particles to move, the second magnetic layer 3B Since a fixed pattern can be formed by sparse and dense magnetic particles, it is possible to freely select a magnetic material having a coercive force of 250 Oe or more.

The output levels of the signals reproduced from the magnetic recording / reproducing track 5 are the same as those of the first magnetic layer 3A and the second magnetic layer 3.
Although it is determined by the total thickness of B (residual magnetic flux: φr), the output level of the signal reproduced from the fixed signal track 4 changes depending on the ratio of the thicknesses (residual magnetic flux) of both layers.
If the thickness of the first magnetic layer is thick, the magnetization of the fixed signal producing signal is increased, and if the thickness of the second magnetic layer is thick, the magnetic particles of the fixed signal portion are increased. Will increase. Therefore, it is necessary to set the thickness ratio of both layers so that the maximum fixed signal output level can be obtained in accordance with the required output level from the magnetic recording / reproducing track 5. In FIG. 6, the total thickness of both layers is 10 μm (φr =
1.2Mx / cm) and 16μm (φr = 2.0Mx
/ Cm) is a diagram showing the relationship between the ratio of the thickness of the second magnetic layer 3B to the total thickness of both layers and the output of the fixed pattern at that time. The fixed pattern output is shown as a relative value with each maximum value being 1. Second
A high output is obtained when the thickness of the magnetic layer 3B is 20 to 60% of the total thickness of both layers. Therefore, in the present invention, good characteristics can be obtained by selecting the thickness ratio of both layers within the above range.

The fixed pattern of the magnetic recording medium of the present invention is read by the following method. First, the fixed signal track 4 formed on the second magnetic layer 3B is saturation magnetized in one direction with a magnetic head capable of saturation recording on the first and second magnetic layers. At this time, the fixed pattern forming signal recorded in the first magnetic layer 3A is simultaneously DC erased. Next, when the fixed signal track 4 is scanned by the read head, the amount of magnetization changes at the boundary between the dense portion 4A and the sparse portion 4B of the magnetic particles in the second magnetic layer 3B. An output waveform proportional to the change in the amount of magnetization is generated. When reading the fixed pattern, the fixed signal track 4 may be scanned while generating an appropriate bias magnetic field from the reading head. In this way the second
The fixed pattern formed on the magnetic layer 3B at a predetermined position can be read. Moreover, since this fixed pattern is formed as a difference in the physical structure of the magnetic layer, it cannot be erased or rewritten by the magnetic head at all. On the other hand, the parts other than the fixed signal track 4 are the first and second parts.
The variable signal can be magnetically recorded / reproduced by the magnetic head capable of performing saturation recording on the magnetic layer.

It should be noted that the present invention is not limited to the above-mentioned example, and the second
A colored hiding layer, a printing layer, a protective layer and the like may be appropriately provided on the magnetic layer 3B, and a printing layer may be provided as necessary. Further, the first magnetic layer 3A and the second magnetic layer 3B do not have to be bonded to each other, and a non-magnetic intermediate layer having a thickness within the range in which the gist of the present invention can be utilized may be provided therebetween. The present invention can also be applied to a magnetic recording medium in which a magnetic layer having a coercive force different from that of the first and second magnetic layers is laminated as an upper layer or a lower layer. Further, a protective layer, a concealing colored layer, etc. are laminated on a substrate coated with a release agent such as silicon, if necessary, and a second magnetic layer and a non-rewritable fixed pattern are formed by the above-mentioned method. The present invention can also be applied to a card transfer tape in which the magnetic layer is formed and an uppermost layer is coated with an adhesive, and a manufacturing method thereof.

[0018]

EXAMPLES The case where the magnetic recording medium according to the present invention is applied as a magnetic card will be described in detail below with reference to more specific examples. Example 1 Barium ferrite magnetic powder having a coercive force of 2750 Oe was mixed and dispersed with a binder resin, a dispersant, a curing agent, and other additives and a solvent on one entire surface of a white polyester film substrate having a thickness of 188 μm. The produced magnetic coating material was applied by a gravure coating method to obtain a first magnetic layer having a thickness after drying of 7 μm. Next, at a predetermined position of the first magnetic layer,
An FM-modulated signal having a recording density of 210 bpi was saturated-recorded in the longitudinal direction. Further, the same magnetic paint as that of the first magnetic layer is applied from above the signal-recorded first magnetic layer by the gravure coating method and passed through the solenoid coil before drying so that the maximum magnetic field strength is 1200 Oe. Magnetic field orientation is applied, and then it is dried and solidified, and the recording density is 210 bpi.
A second magnetic layer having a thickness of 5 μm having a fixed signal track on which the fixed pattern was recorded. In this way, a magnetic sheet having a coercive force of 2750 Oe, a total thickness of the magnetic layer of 12 μm, and a partially non-rewritable fixed pattern formed was obtained.

Example 2 A cobalt-containing γF having a coercive force of 650 Oe was formed on the entire surface of one side of a white polyester film substrate having a thickness of 188 μm.
The magnetic paint prepared by mixing and dispersing e ₂ O ₃ magnetic powder with a binder resin, a dispersant, a curing agent, and other additives and a solvent is applied by the gravure coating method, and the thickness after drying is 7 μm. A magnetic layer was obtained. Next, a signal, which was FM-modulated with a recording density of 210 bpi, was saturated-recorded in the longitudinal direction at a predetermined position on the first magnetic layer. Further, the same magnetic coating material as that of the first magnetic layer is applied on the first magnetic layer on which the signal is recorded by the gravure coating method, and is passed through the solenoid coil before being dried so that the maximum magnetic field strength is 400 Oe. Magnetic field orientation is applied and then dried and solidified, recording density is 210bp
A second magnetic layer having a thickness of 5 μm having a fixed signal track on which a fixed pattern i was recorded was formed. In this way, a magnetic sheet having a coercive force of 650 Oe, a total thickness of the magnetic layer of 12 μm, and a part of which a non-rewritable fixed pattern was formed was obtained.

The magnetic sheets produced in Examples 1 and 2 were made into 86
A magnetic card having a size of 54 mm was punched out. With a reader / writer equipped with a magnetic head capable of saturation-writing a magnetic medium having a coercive force of 2750 Oe, the fixed signal track of the magnetic card manufactured in Example 1 was saturated and magnetized,
The signal recorded on the first magnetic layer was DC erased. Next, a fixed current was applied to a read head with a bias coil attached to the same reader / writer, and a fixed signal track was scanned while generating a bias magnetic field of about 1000 Oe from the front gap of the head to read a fixed pattern. Then, with the same reader / writer, 210 bpi is applied to a portion other than the fixed signal track of the card of the first embodiment.
Saturation-recording the FM-modulated signal of, and then scanning the same portion without applying a bias current to the reading head,
The signal recorded by the head was read. Next, the coercive force is 650
With a reader / writer equipped with a magnetic head capable of saturation-writing an Oe magnetic medium, the fixed signal track of the magnetic card produced in Example 2 was saturated and magnetized, and the signal recorded in the first magnetic layer was DC erased. . Next, a fixed current was applied to a read head with a bias coil attached to the same reader / writer, and a fixed signal track was scanned while generating a bias magnetic field of about 500 Oe from the front gap of the head to read a fixed pattern. Next, a 210 bpi FM-modulated signal was saturated-recorded by the same reader / writer on a portion other than the fixed signal track of the card of Example 2, and then the same portion was scanned without applying a bias current to the reading head. , Read the signal recorded by the head. As a result, in both the cards of Examples 1 and 2, the F of 210 bpi recorded in the fixed signal track was recorded.
The M signal is 210 recorded by saturation recording other than the fixed signal track.
A reproduced waveform having the same shape as that of the bpi signal was obtained, and each could be read at a sufficient output level. In particular, with the fixed pattern of each card, an output of 20 to 30% was obtained at a relative level with respect to the saturated output level recorded on each head, and a sufficient SN ratio was secured.

[0021]

In the magnetic recording medium according to the present invention, a non-rewritable fixed pattern is recorded on a part of the magnetic layer capable of magnetic recording and reproduction, and the layer on which the fixed pattern is recorded has variable information as in the prior art. It does not affect recording and reproduction. Further, the fixed pattern is made of the same material as the magnetic material forming the magnetic layer for recording / reproducing the variable information, and since both are integrally formed, it is impossible to scrape off only the fixed pattern. It is difficult to recognize the existence of a fixed pattern even by analyzing the material composition of both.
Therefore, if the fixed pattern is used as identification information for identifying the medium, it is possible to provide a magnetic recording medium with extremely high safety against forgery or alteration of the medium.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a magnetic recording medium used in the present invention.

FIG. 2 is a sectional view of a portion taken along line XX in FIG.

FIG. 3 is a sectional view of a portion taken along line YY.

FIG. 4 is a schematic view showing an example of a method for manufacturing a magnetic recording medium of the present invention.

FIG. 5 is a diagram for explaining a process of forming a non-rewritable fixed pattern on the magnetic recording medium according to the present invention.

FIG. 6 shows a total thickness of the first and second magnetic layers of 10 μm.
(Φr = 1.2Mx / cm) and 16 μm (φr =
It is a figure which shows the relationship of the ratio of the thickness of a 2nd magnetic layer with respect to the total thickness of both layers at the time of (2.0 Mx / cm), and the output of a fixed pattern at that time.

FIG. 7 is a cross-sectional view showing the structure of a medium according to the related art.

[Explanation of symbols]

 1: Magnetic recording medium 2: Substrate 3A: First magnetic layer 3B: Second magnetic layer 4: Fixed signal track 4A: Part where magnetic particles are dense 4B: Part where magnetic particles are sparse 10: Unwinding device 11: First coating head 12: Magnetic paint 13: First orienting device 14: First drying device 15: Magnetic head 16: Second coating head 17: Magnetic paint 18: Second for fixed pattern formation Orienting device 19: Second drying device 20: Winding device

Claims (3)

[Claims] 1. A first magnetic layer and a second magnetic layer made of the same magnetic material capable of magnetic recording and reproduction are sequentially laminated on the whole or a part of a substrate, and at least one of the second magnetic layers is formed. A magnetic recording medium characterized in that a non-rewritable fixed pattern formed by the influence of a magnetic field due to a signal recorded in the first magnetic layer and an orientation magnetic field is recorded in the portion. 2. The non-rewritable fixed pattern recorded on the second magnetic layer is sparse in a portion where magnetic particles are dense in correspondence with the direction of magnetization of a signal recorded in the first magnetic layer. The magnetic recording medium according to claim 1, wherein the portions and the portions are adjacent to each other and are alternately formed. 3. A first magnetic layer made of a magnetically recordable magnetic material is formed on a substrate, and then a predetermined signal is recorded on the first magnetic layer, after which the same magnetic material as the first magnetic layer is formed. A magnetic coating material having a magnetic field strength such that the signal recorded in the first magnetic layer is not attenuated before the magnetic coating material is dried and solidified, and the direction is recorded in the first magnetic layer. Magnetic field orientation treatment that is substantially parallel to and substantially constant with respect to the remanent magnetization direction of the magnetic field, and then by drying and solidifying the magnetic paint, a magnetic field generated by a signal recorded in the first magnetic layer and A method of manufacturing a magnetic recording medium, which comprises forming a second magnetic layer, at least a part of which includes a non-rewritable fixed pattern formed under the influence of an orientation magnetic field.