JP3192633B2 - Magnetic recording medium and method for reproducing fixed information from magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic card such as a shopping card, a savings card, a commuter pass, a ticket, a coupon, a prepaid card, a cash card, a credit card, an identification card, a consultation ticket, a magnetic sheet, a magnetic sheet. The present invention relates to a magnetic recording medium used for roll paper and the like and a method for reproducing fixed information on the magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, the fields of use of magnetic recording media such as magnetic recording cards or magnetic roll paper have become more and more widespread. The basic structure of this type of magnetic recording medium is
A magnetic layer composed of a magnetic substance and a binder is formed on a base (substrate) composed of a non-magnetic substance, and recording is performed by magnetizing the magnetic layer. Such a magnetic recording medium,
Since recording / erasing can be repeatedly performed, it is widely used as a recording medium. However, such a magnetic recording medium can be illegally used by duplicating or falsifying magnetic information, and thus it is required to prevent this.

In such a background, a method widely used as a method for preventing forgery of a magnetic recording medium has hitherto been widely used.
There are two broad categories: methods that make recording and reproduction of magnetic recording information difficult, and methods that add authenticity determination information to the magnetic recording medium itself. The former is a method of hiding recorded legitimate information and making it difficult to write and read information, thereby making it difficult to copy or falsify with a normal magnetic recording device,
The latter is a method of preventing forgery or falsification by inserting identification information for determining whether or not a magnetic card is a legitimate one into the magnetic card itself.

[0004] More specifically, the former known as a measure for preventing unauthorized use by making recording and reproduction of magnetic recording information difficult is to provide a legitimate information by providing a multilayered magnetic recording layer. There is known a technique for concealing an ordinary magnetic recording / reproducing device so that it cannot be read by an ordinary magnetic recording / reproducing apparatus. In other words, if the dummy information is recorded by weighing the regular information, the regular information and the dummy information are read in an overlapping manner during reading by a normal magnetic recording / reproducing apparatus, so that it becomes difficult to analyze the regular information. . However, such a method has a disadvantage that a complicated magnetic recording / reproducing device is required. Also, once the details of the method of reading the legitimate information are known, if the user is familiar with magnetic recording, it becomes possible to read and analyze the information, thus preventing mass copying of the magnetic recording medium. Was not enough.

[0005] On the other hand, the latter magnetic recording medium is for applying authenticity determination information to a magnetic card itself. In this method, a large amount of duplication can be prevented because the medium itself has fixed information for determining whether the magnetic recording medium is legitimate. However, this method has a problem that it cannot cope with alterations such as rewriting fixed information of a regular medium.

[0006]

As an example of the latter magnetic recording medium, the present inventors disclosed in Japanese Patent Application No. 4-175930 a magnetic recording medium having a magnetic layer provided with a plurality of projections and a method of manufacturing the same. Has applied for a patent. This patent application 4
According to 175930, the base is 250-4000
A first magnetic layer made of a magnetic material having an Oersted coercive force;
A second magnetic layer made of a magnetic material having a coercive force of 00 Oe or less is laminated, and the recording pattern formed on the first magnetic layer is transferred to the second magnetic layer to form a plurality of convex portions on the second magnetic layer. By using the plurality of protrusions as fixed information for determining the authenticity of the magnetic recording medium using the magnetic recording medium thus formed, it is determined whether the magnetic recording medium is legitimate.

The present inventors have analyzed in detail in Japanese Patent Application No. 4-175930 the relationship between a plurality of protrusions formed on a second magnetic layer and a magnetization reversal pattern formed on a first magnetic layer. As a result, they have found that a magnetic recording medium with higher anti-counterfeit performance can be obtained, and have reached the present invention.

The present invention has been made in view of the above circumstances, and it is possible to easily add forgery prevention information that cannot be added or erased, and to prevent unauthorized use of magnetic information by duplication or falsification. It is an object of the present invention to provide a possible magnetic recording medium and a method for reproducing fixed information on the magnetic recording medium.

[0009]

In order to solve the above problems, the present invention employs the following constitution. 2. The magnetic recording medium according to claim 1, wherein a first magnetic layer made of a first magnetic powder having a coercive force of 250 to 4000 Oe and a second magnetic layer made of a coercive force of 100 Oe or less are formed on a base made of a non-magnetic material. At least a second magnetic layer made of powder,
A plurality of magnetization reversal patterns are formed on the first magnetic layer;
With the magnetization reversal pattern remaining, two boundaries sandwiching the magnetization reversal pattern are formed on one surface of the second magnetic layer.
It integrally said second magnetic powder densely respectively on the surface
At least one or more reversal protrusions formed on the magnetization reversal pattern by forming the second magnetic powder on a boundary surface between the two magnetization reversal patterns. It is characterized in that the above-mentioned boundary surface convex portion is formed so as to be mixed along the reading direction of magnetic recording.

According to a second aspect of the present invention, there is provided a magnetic recording medium comprising: a first magnetic layer made of a first magnetic powder having a coercive force of 250 to 4000 Oersted on a base made of a non-magnetic material; A second magnetic layer made of a second magnetic powder is laminated at least, a plurality of magnetization reversal patterns are formed on the first magnetic layer, and the magnetization reversal pattern is left on one surface of the second magnetic layer. the second magnetic powder two boundary plane sandwiching the magnetization reversal patterns their
The magnetization by which they are integrated with respectively densely
At least one or more inversion protrusions formed on the inversion pattern and at least one or more boundary surface protrusions in which the second magnetic powder is densely packed on the boundary surface between the two magnetization inversion patterns, The fixed information is recorded by being formed so as to be mixed along the reading direction of the recording, and the reproduction signal of the fixed information by the magnetic head has a signal waveform corresponding to the inverted convex portion and a signal waveform corresponding to the boundary convex portion. It is configured as a continuation of a corresponding signal waveform, and an output amount of the signal waveform corresponding to the inversion convex portion varies according to a change in polarity of a bias magnetic field applied to the magnetic head. Further, the output amount of the signal waveform corresponding to the inversion convex portion fluctuated due to a change in the polarity of the bias magnetic field.
When the, and wherein the small Kunar than the output of the signal waveform corresponding to the boundary surface protrusion. Further, the output amount of the signal waveform corresponding to the inversion convex portion includes an output derived from the inversion convex portion excited by the bias magnetic field applied to the magnetic recording medium and the magnetization inversion pattern below the inversion convex portion. Characterized by the fact that it fluctuates due to interference with the leakage magnetic flux.

According to a fifth aspect of the present invention, there is provided a method for recording and reproducing fixed information on a magnetic recording medium, wherein the fixed information recorded on the magnetic recording medium is reproduced by a magnetic head. The coercive force is 2 on the base consisting of
The first magnetic powder of 50 to 4000 Oersted
At least a magnetic layer and a second magnetic layer made of a second magnetic powder having a coercive force of 100 Oe or less are laminated, a plurality of magnetization reversal patterns are formed on the first magnetic layer, and one surface of the second magnetic layer is formed. , Two of which sandwich the magnetization reversal pattern
It said second magnetic powder on the boundary surface of these densely respectively
Integrated on the magnetization reversal pattern.
At least one or more inversion protrusions formed by the first magnetic field and at least one or more boundary surface protrusions in which the second magnetic powder is densely arranged on the boundary surface between the two magnetization reversal patterns are arranged in the magnetic recording reading direction. The fixed information is composed of the one or more inversion projections and the one or more boundary surface projections, and
The fixed information is reproduced by scanning the magnetic layer along the reading direction of the magnetic recording to obtain a reproduction signal,
The reproduction signal has a signal waveform corresponding to the inverted convex portion,
Changing the output amount of the signal waveform corresponding to the inversion projection by changing the polarity of the bias magnetic field applied to the magnetic recording medium at the time of reproduction. Features.

According to a sixth aspect of the present invention, there is provided a method for reproducing fixed information on a magnetic recording medium, comprising the steps of: changing a polarity of a bias magnetic field applied to the magnetic recording medium; By changing, the output amount of the signal waveform corresponding to the inverted convex portion is made smaller than the output amount of the signal waveform corresponding to the boundary surface convex portion. Further, a method for reproducing fixed information of a magnetic recording medium according to claim 7 is the method for reproducing fixed information of a magnetic recording medium according to the above, wherein the output amount of the signal waveform corresponding to the inverted convex portion is set to It is characterized in that it fluctuates due to interference between an output derived from the reversal protrusion excited by the bias magnetic field applied to the magnetic recording medium and a leakage magnetic flux of the magnetization reversal pattern below the reversal protrusion.

[0013]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a plan view of a magnetic recording medium 10 according to an embodiment of the present invention. This magnetic recording medium 1
Numeral 0 generally comprises a base 1 made of a card-type non-magnetic material, and a magnetic stripe T formed on the base 1 along the longitudinal direction of the base 1. FIG.
FIG. 3A is a cross-sectional view of the magnetic stripe T taken along the line XX of FIG. 3A, wherein the magnetic stripe T includes a first magnetic layer 2 formed on a base 1 and a second magnetic layer 3 covering the first magnetic layer 2. Are laminated. On the second magnetic layer 3, a coating layer (not shown) is laminated. The first magnetic layer 2 is formed by dispersing and fixing a first magnetic powder having a coercive force of 250 to 4000 Oersted with a binder, and the second magnetic layer 3 is formed of a second magnetic powder having a coercive force of 100 Oersted or less. It is obtained by dispersing and fixing with a binder.

The base 1 used here has a thickness of 150
A sheet-like non-magnetic material such as a polyester film, vinyl chloride film, synthetic paper, wood pulp paper, laminated paper or the like having a thickness of about 1 μm to 1 mm can be used, but any suitable material may be used according to the intended use. Therefore, a sheet or film made of the above-mentioned material, or a generally known base material for a magnetic recording medium, or a laminate thereof may be used.

Further, γ-iron oxide, cobalt-doped γ-iron oxide, chromium oxide, barium ferrite, strontium ferrite, etc. are applied to the magnetic material constituting the first magnetic powder having a coercive force of 250 to 4000 Oe. Carbonyl iron, manganese zinc ferrite, zinc ferrite, nickel, triiron tetroxide, permalloy, sendust, alpalm, etc. are applied to the magnetic material constituting the second magnetic powder having a coercive force of 100 Oe or less. it can.

In the first magnetic layer 2 and the second magnetic layer 3,
The binder for dispersing and fixing the first and second magnetic powders is used as a binder such as vinyl chloride, vinyl acetate copolymer, vinyl acetate, vinyl alcohol copolymer, polyurethane resin, polyester resin, epoxy resin, and polyisocyanate resin. And a small amount of an additive such as a pigment can be used. In addition, a known binder for a magnetic powder may be appropriately used. Incidentally, inorganic pigments such as silica and alumina, waxes, silicone oils and the like may be used as the additives. Further, the coating layer laminated on the second magnetic layer 3 includes (a) a colored layer containing aluminum powder and a white pigment for hiding the coloring of the second magnetic layer 3, and (b) a leuco dye type thermosensitive recording. Recording layer such as a discharge recording layer comprising a layer, a metal deposition layer of tin, aluminum, etc.,
(C) One or a plurality of layers of a protective layer made of an ultraviolet curable resin may be applied.

In FIG. 1B, the first magnetic layer 2 includes
The magnetization reversal patterns 61 and 62 having different lengths in the longitudinal direction of the magnetic stripe T are formed together. The length of the magnetization switching pattern 61 is shorter than the length of the magnetization switching pattern 62.

On the upper surface (one surface) 4 of the second magnetic layer 3, inverted protrusions 51 and boundary surface protrusions 52 coexist along the longitudinal direction of the magnetic stripe T (the reading direction of magnetic recording). It is formed so that. The reversal convex portions 51 project upward from the second magnetic layer 3, and are formed by densely packed second magnetic powder on the magnetization reversal pattern 61. The width of the reversal protrusion 51 is substantially equal to the length of the magnetization reversal pattern 61. Also, the boundary surface convex portions 52 are:
The protrusion 63 projects upward from the second magnetic layer 3, and is a boundary surface 63 between two adjacent magnetization reversal patterns 62, 62.
The second magnetic powder is densely formed thereon. The inversion protrusions 51 and the boundary surface protrusions 52 are formed densely so that the second magnetic powder contained in the second magnetic layer 3 rises. Inversion convex part 5
The second magnetic powder is densely aggregated in the portions 1 and the boundary surface convex portions 52 and in the vicinity thereof. Thus, the fixed information is recorded on the second magnetic layer 3 by forming the density of the second magnetic powder by the plurality of inversion protrusions 51 and the boundary surface protrusions 52.

Next, a method for manufacturing the magnetic recording medium 10 will be described. In the magnetic recording medium 10, the first magnetic layer 2 is formed on the base 1 by the first magnetic layer forming device 30 shown in FIG.
The first magnetic layer 2 is formed by the second magnetic layer forming device 31 shown in FIG.
It is manufactured by forming the second magnetic layer 3 thereon.

First, a method of forming the first magnetic layer 2 on the base 1 using the first magnetic layer forming apparatus 30 will be described. The first magnetic layer forming device 30 shown in FIG. 2 includes a sending reel 11 on which the long base 1 is wound, a first magnetic layer coating device 12, a magnetic field orientation device 15, and a drying part 16.
And a take-up reel 18 are connected in series to form a schematic structure.
The first magnetic layer passes through a coating device 12, a magnetic field orientation device 15, and a drying part 16.

First, the base 1 made of a non-magnetic material is sent out by the sending reel 11 and guided to the first magnetic layer coating device 12, and the base 1 is coated with the magnetic paint for the first magnetic layer 2. The coating device 12 stores a magnetic paint 12a including the first magnetic powder, the binder, and a solvent,
The magnetic paint 12a is applied to the base 1 by the coating head 13 in contact with the magnetic paint 12a. The base 1 to which the magnetic paint 12a has been applied is sent out to the magnetic field orientation device 15 via the roll 14. The magnetic field orientation device 15 is a magnetic paint 1
2a for orienting the first magnetic powder in the magnetic paint 12a using a magnet for orientation while the magnetic paint 12a is in an undried state.
Orient the magnetic powder. Further, the base 1 is dried with a part 16
And the solvent in the magnetic paint 12a is volatilized and dried. Thus, the first magnetic layer 2 is formed. Furthermore,
The base 1 is wound on a take-up reel 18 via a roll 17. The wound base 1 is an original 27 coated with only the first magnetic layer 2. It is preferable that the first magnetic layer 2 is magnetically oriented by the magnetic field alignment device 15, but it may be omitted.

Next, using the second magnetic layer forming apparatus 31,
A method of manufacturing the magnetic recording medium 10 by forming and laminating the second magnetic layer 3 on the first magnetic layer 2 of the material 27 will be described. The second magnetic layer forming apparatus 31 shown in FIG. 3 includes a sending reel 19 on which a long material 27 is wound and a recording magnetic head 20 for performing magnetic recording on the first magnetic layer 2.
A second magnetic layer coating device 21, a drying part 24,
A take-up reel 26 and a take-up reel 26 are arranged in series, and a schematic configuration is provided. A raw web 27 fed from a feed reel 19 passes through a recording magnetic head 20, a coating device 21 for a second magnetic layer, and a drying part 24. It has become. The delivery reel 19 is obtained by removing the take-up reel 18 in FIG. 2 from the first magnetic layer forming device 30 and attaching it to the second magnetic layer forming device 31.

First, the raw material 27 is sent out by the sending-out reel 19 and guided to the recording magnetic head 20, and magnetic recording is performed on the first magnetic layer 2. This magnetic recording may be performed from the front side or the back side of the first magnetic layer 2 by the recording magnetic head 20 in the same manner as in a normal magnetic recording system. As a result of magnetic recording,
A plurality of magnetization reversal patterns 61 and 62 shown in FIG. 1B are formed in the first magnetic layer 2 in a mixed manner. At this time, the length of the magnetization switching pattern 61 is made shorter than the length of the magnetization switching pattern 62.

Thereafter, the material 27 is guided to the second magnetic layer coating device 21, and the second magnetic layer 3 is formed on the first magnetic layer 2 of the material 27.
Apply magnetic paint for The coating device 21 includes the second
Magnetic paint 21 comprising magnetic powder, the binder and a solvent
The magnetic head 21 a is stored, and the coating head 22 in contact with the magnetic coating 21 a applies the magnetic coating 21 a to the material 27.

Immediately after the application of the magnetic paint 21a, in a state where the solvent of the magnetic paint 21a is still present, the second magnetic powder in the magnetic paint 21a is replaced with the magnetization reversal pattern 61 by magnetic recording on the first magnetic layer 2. . And the magnetization reversal patterns 62... (FIG. 1B). Two adjacent magnetization reversal patterns 6
In the vicinity of the boundary 63 between the second and the second, the dense second
The magnetic powder swells on the boundary surface 63 to form the boundary surface protrusion 52. In the vicinity of the boundary 64 between the magnetization reversal pattern 61 and the magnetization reversal pattern 62, the dense second magnetic powder swells on the boundary 64.
Is adjacent to another boundary surface 64 adjacent to the magnetization reversal pattern 61, so that the second magnetic powder raised on these two boundary surfaces is integrated to form the reversal convex portion 51.
The reversal convex portion 51 is formed on the magnetization reversal pattern 61, and has a width substantially equal to the length of the magnetization reversal pattern 61.
As described above, when the distance between two adjacent boundary surfaces is reduced, the second magnetic powder that is densely integrated there forms one projection.

In this way, the second magnetic powder is densely swelled in accordance with the arrangement of the magnetization reversal patterns 61, 62,... Are formed so as to coexist with the boundary surface convex portions 52, and the inverted convex portions 51 and the boundary surface convex portions 52 are formed.
As a result, fixed information is recorded on the second magnetic layer 3.

Further, the raw material 2 coated with the magnetic paint 21a
7 is sent out to a drying part 24 via a roll 23. In the drying part 24, the solvent in the magnetic paint 21a is volatilized and dried. Thus, the second magnetic layer 3 is formed. Further, the web 27 is wound on a take-up reel 26 via a roll 25. Rolled web 27
Is a magnetic substrate on which the first magnetic layer 2 and the second magnetic layer 3 are formed. The magnetic material is punched into a JIS size magnetic card to obtain a magnetic recording medium 10. When the coating layer is provided, the coating can be easily formed by separately applying the coating material for the coating layer to the magnetic sheet using a coating device for the coating layer.

Next, a method of reproducing fixed information recorded on the second magnetic layer 3 of the magnetic recording medium 10 will be described. First, the second
The relationship between the inverted convex portions 51 formed on the magnetic layer 3 and the output amount of the signal waveform of the reproduced signal obtained by reproducing the fixed information will be described with reference to FIG. The first magnetic layer 2 of the magnetic stripe T shown in FIG.
2 and the magnetization reversal patterns 61 shorter in length than the magnetization reversal patterns 62 are alternately arranged.
Only the reversal convex portion 51 located on the magnetization reversal pattern 61 is formed, and fixed information is recorded. When the fixed information is reproduced by using a reproducing magnetic head while applying a bias magnetic field to the magnetic stripe T, and a reproduction signal of the fixed information is displayed on a synchroscope, FIGS. It is as shown in. The reproduction signal shown in FIG. 4 (b) was obtained by reproducing while applying a bias magnetic field to the reproducing magnetic head, and was reproduced using a special reproducing magnetic head capable of generating a bias magnetic field. . The reproduction signal shown in FIG. 4C is obtained when the polarity of the bias magnetic field applied by the magnetic head for special reproduction is reversed in the direction shown in FIG. 4B.

The reproduction signal 40 shown in FIG. 4 (b) is formed as a continuation of a plurality of pulse-like signal waveforms 41. Each of the signal waveforms 41 corresponds to the inverted convex portion 51. The output amount of the signal waveforms 41 shown here is V in absolute value. Also, the reproduced signal 45 shown in FIG. 4C is configured as a continuation of a plurality of pulse-like signal waveforms 46... As in the case of FIG. Corresponding to the parts 51. The output amount of the signal waveforms 46 shown here is V ′ in absolute value.

The magnitude relationship between the output amounts V and V 'of the signal waveforms 41 ... 46 becomes V>V'. By changing the polarity of the bias magnetic field applied by the magnetic head for special reproduction, the reproduction signal It can be seen that the output amount of the signal waveform fluctuates.

As described above, the cause of the variation in the output amount of the signal waveform depending on the polarity of the bias magnetic field of the magnetic head for special reproduction is not clear, but the direction of the leakage magnetic flux from the magnetization reversal pattern 61 of the first magnetic layer 2 is unknown. It is considered that the relationship between the direction and the direction of the bias magnetic field applied to the magnetic recording medium by the magnetic head for special reproduction has at least an influence. That is,
As shown in FIG. 8A, the direction of the bias magnetic field 71 applied to the magnetic recording medium by the magnetic head S for special reproduction is the same as the direction of the magnetic flux leaking from the magnetization reversal pattern 61 (the dotted arrow in the figure). If there is, the bias magnetic field 71 of the magnetic head S
Is considered to be amplified by the leakage magnetic field and the output amount of the reproduced waveform becomes V. On the other hand, as shown in FIG. 8B, the direction of the bias magnetic field 71 applied to the magnetic recording medium by the magnetic head S for special reproduction and the direction of the leakage magnetic flux (dotted arrow in the figure) from the magnetization reversal pattern 61 are different. If the direction is reversed, it is considered that the bias magnetic field 71 of the magnetic head S is canceled out by the leakage magnetic field, the output of the magnetic head S decreases, and the output amount of the reproduced waveform becomes V ′ (V> V ′).

Next, the relationship between the inverted protrusions 51 and the boundary protrusions 52 formed on the second magnetic layer 3 and the output amount of the signal waveform will be described with reference to FIGS. First,
A recording signal (where T ₂ > T ₁ ) having a pulse waveform in which the recording pitch T ₁ and the recording pitch T ₂ are alternately arranged as shown in FIG. 2
The magnetic recording is performed on the first magnetic layer 2 according to 0, the second magnetic layer 3 is formed, the magnetic material 27 is punched out, and a magnetic recording medium on which fixed information based on the recording signal is recorded is prepared. The cross section of the magnetic stripe T of the magnetic recording medium is a as shown in FIG. 5 (b), the magnetization reversal patterns 61 and the corresponding magnetization reversal in the recording pitch T ₂ corresponding to the recording pitch T ₁ in the first magnetic layer 2 Patterns 61 are alternately arranged, and only the reversal protrusions 51 located on the magnetization reversal pattern 61 are formed on the second magnetic layer 3 to record fixed information.

The reproduction signal of the fixed information is as shown in FIGS. 5C and 5D. The reproduction signal shown in FIG. 5C is applied to the magnetic recording medium by a special reproduction magnetic head. It is obtained by reproducing while applying a magnetic field,
The reproduction signal shown in FIG. 5D indicates the polarity of the bias magnetic field applied to the magnetic recording medium by the magnetic head for special reproduction.
This is obtained when the direction is reversed from the case of (c). In these reproduced signals, the output amounts of the respective signal waveforms are V and V '(where V>V'), as in FIGS. 4B and 4C.

Next, as shown in FIG. 6A, a recording signal having a pulse waveform in which the recording pitch T ₃ is repeated is recorded on the first magnetic layer 2 in the same manner as described above. A magnetic recording medium on which fixed information is recorded based on a recording signal is prepared. The cross section of the magnetic stripe T of the magnetic recording medium is as shown in FIG. 6B, and the magnetization reversal patterns 62 corresponding to the recording pitch T ₃ are formed continuously in the first magnetic layer 2. In the second magnetic layer 3, only the boundary protrusion 52 located on the boundary surface 63 of the magnetization reversal pattern 62 is formed, and fixed information is recorded.

The reproduction signal of the fixed information is as shown in FIGS. 6C and 6D. The reproduction signal shown in FIG. 6C is applied to the magnetic recording medium by a special reproduction magnetic head. It is obtained by reproducing while applying a magnetic field,
The reproduction signal shown in FIG. 6D indicates the polarity of the bias magnetic field applied to the magnetic recording medium by the magnetic head for special reproduction in FIG.
This is obtained when the direction is reversed from the case of (c). In these reproduced signals, the output amount of each signal waveform is V, and it is understood that the output amount of the signal waveform does not change even if the polarity of the bias magnetic field of the reproducing magnetic head is changed.

As described above, the reason why the output amount of the signal waveform corresponding to the interface 52 is not changed by the polarity of the bias magnetic field is as follows. It is considered that the positional relationship has at least affected. That is, as shown in FIG.
Since the boundary surface 53 of the magnetization reversal pattern 62 is located below the boundary surface convex portion 52, no leakage magnetic flux (dashed line in the drawing) of the magnetization reversal pattern 62 exists above the boundary surface convex portion 52. Bias magnetic field 71 by reproducing magnetic head S
Is not affected by the leakage magnetic flux, the output of the reproducing head becomes constant, and it is considered that the output amount of the signal waveform does not fluctuate.

As described above, in the magnetic recording medium of the present invention, the output amount of the signal waveform corresponding to the inverted convex portion 51 fluctuates depending on the polarity of the bias magnetic field by the magnetic head for special reproduction. Does not change even with the polarity of the bias magnetic field from the magnetic head for special reproduction. Utilizing this property,
It is possible to arbitrarily change the output amounts of a plurality of signal waveforms constituting the reproduction signal. This will be described below.

As shown in FIG. 7A, a recording having a pulse waveform in which different recording pitches T ₁ , T ₂ , and T ₃ (where T ₃ > T ₂ > T ₁ ) is randomly repeated. A signal is recorded on the first magnetic layer 2 in the same manner as described above to prepare a magnetic recording medium on which fixed information based on the recording signal is recorded. The reproduction signal of the fixed information recorded on the magnetic recording medium is as shown in FIGS. 7B and 7C. The reproduction signal shown in FIG. 7B is obtained by reproducing the magnetic recording medium by applying a bias magnetic field with a magnetic head for special reproduction, and the reproduction signal shown in FIG. 7B is obtained when the polarity of the bias magnetic field applied to the magnetic recording medium by the magnetic head for use is reversed from that in FIG. 7B.

In the reproduced signal shown in FIG. 7B, the output amount of each signal waveform is V.
In the reproduced signal shown in (c), a signal waveform whose output amount is V and a signal waveform whose output amount is V 'are mixed and continuous. As shown in FIGS. 7A and 7C,
On both sides of the signal waveform whose output amount is V, the recording pitch T ₃
Or another signal waveform is present at a T _2, the piece next to the signal waveform output amount is V ', another signal waveform at a recording pitch T ₁ is present. As described above, by adjusting the length of the recording pitch, the reproduced signal is converted into a signal waveform whose output amount is V, a signal waveform whose output amount is V ', or a continuation of a plurality of signal waveforms in which these are mixed. It becomes free.

In the above-described magnetic recording medium 10, the second
In the magnetic layer 3, at least one or more inversion protrusions 51 in which the second magnetic powder is densely packed on the magnetization switching pattern 61, and the second magnetic powder is densely packed on the boundary surface 63 between the two magnetization switching patterns 62,62. At least one or more boundary surface protrusions 52 are formed so as to coexist along the reading direction of magnetic recording, and fixed information is constituted by the inversion protrusions 51 and the boundary surface protrusions 52. The magnetic recording medium 10
, It becomes impossible to erase or write fixed information, and a plurality of magnetization reversal patterns 61... 62 formed on the first magnetic layer 2 are covered by the second magnetic layer 3. , Cannot be visually confirmed even when observed with a magnetic viewer or the like. Further, if a coating layer is formed on the second magnetic layer, the reversal convex by the naked eye can be observed. Since the observation of the portion 51 and the convex portion 52 at the boundary surface becomes impossible, forgery and falsification of the magnetic recording medium 10 can be prevented.

In the magnetic recording medium 10 described above, the reproduction signal of the fixed information by the magnetic head is configured as a continuation of a signal waveform corresponding to the inverted convex portion 51 and a signal waveform corresponding to the boundary convex portion 52. And the inverted convex portion 51
The output amount of the signal waveform corresponding to the above fluctuates due to the change in the polarity of the bias magnetic field applied to the magnetic recording medium. Further, a more complicated signal can be used as a reproduction signal of the fixed information, and the fixed information can be complicated to provide the magnetic recording medium 10 having a high security function. In particular, since the output amount of the signal waveform corresponding to the inverted convex portion 51 can be made smaller than the output amount of the signal waveform corresponding to the boundary convex portion 52, the fixed information is complicated and the security function is high. Magnetic recording medium 10
It can be.

The output amount of the signal waveform corresponding to the inversion convex portion 51 fluctuates due to interference between the bias magnetic field applied to the magnetic recording medium and the leakage magnetic flux of the magnetization reversal pattern 61 below the inversion convex portion 51. Therefore, the reproduction signal of the fixed information can be easily complicated, and the magnetic recording medium 10 having a high security function can be obtained.

According to the method for reproducing fixed information on the magnetic recording medium described above, the reproduced signal of the fixed information is converted into a signal waveform having an output amount of V, a signal waveform having an output amount of V ', or a plurality of mixed signal waveforms including these. Since the signal waveform can be made continuous, the fixed information can be complicated and the security function of the magnetic recording medium 10 can be enhanced. In addition, the inverted convex portion 5
The fixed information is complicated by making the signal waveform whose output amount fluctuates according to 1 a dummy signal waveform and the signal waveform whose output amount fluctuates corresponding to the boundary surface convex portion 52 as a regular signal waveform. And the security function of the magnetic recording medium 10 can be enhanced.

[0044]

Embodiments of the present invention will be described below. (Experimental Example 1) First, a magnetic paint for the first magnetic layer was prepared with the following composition. Barium ferrite _{(Ba0 · 6Fe 2 O 3)} ( coercive force 2750 Oe specific surface 8m ² / g) 100 parts by weight Carbon black 3 parts by weight of lecithin, 1 part by weight vinyl acetate-vinyl alcohol copolymer chloride polymer resin 20 parts by weight of polyurethane Resin 20 parts by weight Toluene 60 parts by weight Methyl ethyl ketone 60 parts by weight Methyl isobutyl ketone 60 parts by weight After dispersing the mixture having the above composition by a ball mill for 8 hours, 5 parts by weight of a polyisocyanate-based curing agent was added, and further dispersed for 1 hour. Then, a magnetic paint for the first magnetic layer was obtained.
The coating operation may be performed according to a normal method for manufacturing a magnetic recording medium. That is, as shown in FIG. 2, a magnetic paint 12a for a first magnetic layer is applied to a base 1 made of a white polyester film having a thickness of 188 μm with a coating head 13 and dried in a drying part 16 to be dried. A first magnetic layer having a thickness of 12 μm is formed and wound as a web 27. Immediately after the magnetic paint 12a for the first magnetic layer is applied, an orientation treatment is performed using the magnetic field orientation device 15.

Next, a magnetic paint for the second magnetic layer was prepared with the following composition. Carbonyl iron powder (coercive force 10 Oersted, specific surface area 1 m ² / g) 100 parts by weight Carbon black 3 parts by weight Lecithin 1 part by weight Vinyl chloride / vinyl acetate / vinyl alcohol copolymer resin 20 parts by weight Polyurethane resin 20 parts by weight Toluene 60 parts by weight Part: methyl ethyl ketone: 60 parts by weight: methyl isobutyl ketone: 60 parts by weight After dispersing the mixture having the above composition by a ball mill for 8 hours, 5 parts by weight of a polyisocyanate-based curing agent was added, and the mixture was further dispersed for 1 hour. Magnetic paint was obtained.

Next, as shown in FIG. 3, magnetic recording is performed on the first magnetic layer by the recording magnetic head 20 based on a predetermined recording signal, and a plurality of magnetization reversal patterns are formed on the first magnetic layer. did. The recording magnetic head 20 has a gap width of 5
The thing of 0 μm was used. Magnetic recording is performed by applying a pulse current that can sufficiently saturate the first magnetic layer.
The measurement was performed by the 00 bpi FM method. Detailed conditions for magnetically recording the recording signal on the first magnetic layer are as shown in 1 of Table 1, and the waveform of the actual recording signal was the same as the recording signal shown in FIG.

Next, as shown in FIG.
On the magnetic layer, a magnetic coating layer 21a for a second magnetic layer is applied by a coating head 22 and dried in a drying part 24 to form a second magnetic layer having a thickness of 6 μm, which is wound as a magnetic material. Was. The magnetic substrate obtained in this manner was punched out, and the cross section of the magnetic stripe T was JI as shown in FIG.
An S size card type magnetic recording medium was obtained. The magnetic recording recorded on the first magnetic layer was not erased. Next, the fixed information recorded on the second magnetic layer 3 was reproduced using a magnetic head for special reproduction while applying a bias magnetic field to the magnetic stripe T of the magnetic recording medium to obtain a reproduction signal. The regeneration conditions were the same as those in Table 2.

The reproduced signal obtained in this experiment is shown in FIG.
It was almost the same as the reproduced signal shown in (c), and the output amount of all signal waveforms was V.

[0049]

[Table 1]

[0050]

[Table 2]

(Experimental Example 2) While applying a bias magnetic field to the magnetic stripe T of the magnetic recording medium obtained in Experimental Example 1, the fixed information recorded on the second magnetic layer 3 was reproduced to obtain a reproduced signal. . Regeneration conditions were as shown in Table 2-2. The reproduced signal obtained in this experimental example was almost equivalent to the reproduced signal shown in FIG. 5D, and the output amounts of all signal waveforms were V ′ (where V> V ′).

(Experimental Example 3) The detailed conditions for magnetically recording a recording signal on the first magnetic layer are as shown in Table 1-2, and the waveform of the actual recording signal is the same as that of the recording signal shown in FIG. A magnetic recording medium was manufactured in the same manner as in Experimental Example 1, except for the following. The cross section of the magnetic stripe T of this magnetic recording medium was as shown in FIG. While applying a bias magnetic field to the magnetic stripe T of the magnetic recording medium, the fixed information recorded on the second magnetic layer 3 was reproduced to obtain a reproduced signal. The regeneration conditions were the same as those in Table 2. The reproduced signal obtained in this experimental example was almost equivalent to the reproduced signal shown in FIG. 6C, and the output amounts of all the signal waveforms were V.

(Experiment 4) While applying a bias magnetic field to the magnetic stripe T of the magnetic recording medium obtained in Experiment 3, fixed information recorded on the second magnetic layer 3 was reproduced to obtain a reproduction signal. . Regeneration conditions were as shown in Table 2-2. The reproduced signal obtained in this experimental example was almost equivalent to the reproduced signal shown in FIG. 6D, and the output amount of all signal waveforms was V.

(Experimental Example 5) Detailed conditions for magnetically recording a recording signal on the first magnetic layer are as shown in 3 of Table 1, and the waveform of the actual recording signal is the same as that of the recording signal shown in FIG. A magnetic recording medium was manufactured in the same manner as in Experimental Example 1, except for the following. While applying a bias magnetic field to the magnetic stripe T of the magnetic recording medium, the fixed information recorded on the second magnetic layer 3 was reproduced to obtain a reproduced signal. Table 2 shows the playback conditions.
The test was performed under the condition of 1. The reproduced signal obtained in this experimental example is
It was almost the same as the reproduced signal shown in FIG. 7B, and the output amount of all signal waveforms was V.

(Experimental Example 6) While applying a bias magnetic field to the magnetic stripe T of the magnetic recording medium obtained in Experimental Example 5, the fixed information recorded on the second magnetic layer 3 was reproduced to obtain a reproduced signal. . Regeneration conditions were as shown in Table 2-2. The reproduced signal obtained in this experimental example is substantially the same as the reproduced signal shown in FIG. 7C, and has a signal waveform whose output amount is V and an output amount of V ′ (where V> V ′). Signal waveforms were mixed and continuous.

[0056]

According to the magnetic recording medium of the present invention, the second
The magnetic layer has at least one or more inversion protrusions in which the second magnetic powder is densely arranged on the magnetization reversal pattern, and at least one or more inversion of the second magnetic powder on the boundary surface between the two magnetization inversion patterns. Boundary surface protrusions are formed so as to coexist along the reading direction of magnetic recording, and since fixed information is constituted by these inverted protrusions and boundary surface protrusions, after forming the magnetic recording medium, In this case, the fixed information cannot be erased or written, and the plurality of magnetization reversal patterns formed on the first magnetic layer are covered with the second magnetic layer. However, these magnetization reversal patterns cannot be visually confirmed. Further, if a coating layer is formed on the second magnetic layer, it becomes impossible to visually observe the reversal protrusions and the boundary surface protrusions. Forgery and alteration of media It is possible to prevent.

In the magnetic recording medium of the present invention,
The reproduction signal of the fixed information by the magnetic head is configured as a continuation of the signal waveform corresponding to the inverted convex portion and the signal waveform corresponding to the boundary convex portion, and the output amount of the signal waveform corresponding to the inverted convex portion is reduced. However, since the magnetic head fluctuates due to a change in the polarity of the bias magnetic field applied to the magnetic recording medium, a more complex signal can be generated than in the case of using a reproduction signal having a continuous signal waveform with a constant output amount as in the related art. It can be used as a reproduction signal of fixed information, and the fixed information can be complicated to provide a magnetic recording medium having a high security function. In particular, the output amount of the signal waveform corresponding to the inversion convex portion fluctuated due to a change in the polarity of the bias magnetic field.
When, since the output smaller than the amount Kunar signal waveform corresponding to the boundary surface protrusion may be a magnetic recording medium security features higher complicate the fixed information.

The output amount of the signal waveform corresponding to the inversion protrusion is determined by the output derived from the inversion protrusion excited by the bias magnetic field applied to the magnetic recording medium and the output of the magnetization reversal pattern below the inversion protrusion. Since the signal fluctuates due to interference with the leakage magnetic flux, the reproduction signal of the fixed information can be easily complicated, and a magnetic recording medium having a high security function can be provided.

According to the method for reproducing fixed information of a magnetic recording medium of the present invention, a reproduced signal of fixed information is output in accordance with a signal waveform whose output amount fluctuates corresponding to an inverted convex portion and a boundary surface convex portion. Since it is possible to freely set a signal waveform whose strength does not fluctuate or a plurality of signal waveforms in which these are mixed, the fixed information is complicated and the security function of the magnetic recording medium can be enhanced. In addition, a signal waveform whose output amount fluctuates according to the inverted convex portion is set as a dummy signal waveform, and a signal waveform whose output amount does not fluctuate corresponding to the boundary surface convex portion is set as a regular signal waveform. Information can be complicated and the security function of the magnetic recording medium can be enhanced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a magnetic recording medium according to an embodiment of the present invention, wherein (a) is a plan view of the magnetic recording medium,
(B) is sectional drawing in the XX line in (a).

FIG. 2 is a schematic view showing a first magnetic layer forming apparatus.

FIG. 3 is a schematic view showing a second magnetic layer forming apparatus.

4A and 4B are diagrams illustrating a magnetic recording medium and a reproduction signal of fixed information of the magnetic recording medium, wherein FIG. 4A is a diagram illustrating a cross section of the magnetic recording medium, and FIG. FIG. 3C is a diagram showing a reproduction signal of fixed information of a recording medium, wherein FIG.
FIG. 4 is a diagram showing a reproduction signal of fixed information of the magnetic recording medium shown in FIG.

5A and 5B are diagrams illustrating a magnetic recording medium, a recording signal and a reproduction signal of fixed information of the magnetic recording medium, and FIG. 5A is a diagram illustrating a recording signal magnetically recorded on a first magnetic layer;
(B) is a diagram showing a cross section of the magnetic recording medium obtained by recording the recording signal shown in (a) on the first magnetic layer, (c) is a diagram showing a reproduction signal of fixed information, d) is a diagram showing a reproduction signal of the fixed information.

6A and 6B are diagrams illustrating a magnetic recording medium, a recording signal and a reproduction signal of fixed information of the magnetic recording medium, and FIG. 6A is a diagram illustrating a recording signal magnetically recorded on a first magnetic layer;
(B) is a diagram showing a cross section of the magnetic recording medium obtained by recording the recording signal shown in (a) on the first magnetic layer, (c) is a diagram showing a reproduction signal of fixed information, d) is a diagram showing a reproduction signal of the fixed information.

FIGS. 7A and 7B are diagrams showing a recording signal and a reproduction signal of fixed information of a magnetic recording medium, wherein FIG. 7A is a diagram showing a recording signal magnetically recorded on a first magnetic layer, and FIG. It is a figure which shows a reproduction signal, and (c) is a figure which shows the reproduction signal of fixed information.

8A and 8B are diagrams illustrating a state in which fixed information recorded on a magnetic recording medium is reproduced, wherein FIG. 8A is a schematic diagram illustrating a main part of an inverted protrusion and a reproducing magnetic head, and FIG. Is a schematic diagram showing a main part of a reversing convex portion and a reproducing magnetic head,
(C) is a schematic view showing a main part of the boundary convex portion and the reproducing magnetic head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2 1st magnetic layer 3 2nd magnetic layer 4 Surface (1 surface) of 1st magnetic layer 10 Magnetic recording medium 40, 45 Reproduction signal 41, 46 Signal waveform 51 Inversion convex part 52 Boundary surface convex part 61, 62 Magnetization inversion pattern

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-29157 (JP, A) JP-A-10-143846 (JP, A) JP-A-9-277767 (JP, A) JP-A-11- 39604 (JP, A) JP-A-7-29156 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/02 B42D 15/10 501 G11B 5/09 301 G11B 5 / 716 G11B 5/80

Claims (7)

(57) [Claims] 1. A first magnetic layer comprising a first magnetic powder having a coercive force of 250 to 4000 Oersted on a base made of a non-magnetic material, and a second magnetic layer comprising a second magnetic powder having a coercive force of 100 Oersted or less. A plurality of magnetization reversal patterns are formed on the first magnetic layer, and two magnetization reversal patterns sandwiching the magnetization reversal pattern are provided on one surface of the second magnetic layer while the magnetization reversal patterns remain . boundary
It integrally said second magnetic powder densely respectively on the surface
At least one or more reversal protrusions formed on the magnetization reversal pattern by forming the second magnetic powder on a boundary surface between the two magnetization reversal patterns. A magnetic recording medium characterized in that the above-mentioned boundary surface protrusions are formed so as to coexist along the magnetic recording reading direction. 2. A first magnetic layer made of a first magnetic powder having a coercive force of 250 to 4000 Oe on a base made of a non-magnetic material, and a second magnetic layer made of a second magnetic powder having a coercive force of 100 Oe or less. A plurality of magnetization reversal patterns are formed on the first magnetic layer, and two magnetization reversal patterns sandwiching the magnetization reversal pattern are provided on one surface of the second magnetic layer while the magnetization reversal patterns remain . boundary
It integrally said second magnetic powder densely respectively on the surface
At least one or more reversal protrusions formed on the magnetization reversal pattern by forming the second magnetic powder on a boundary surface between the two magnetization reversal patterns. The above-mentioned boundary surface convex portion is formed so as to be mixed along the reading direction of magnetic recording so that fixed information is recorded, and a reproduction signal of the fixed information by the magnetic head corresponds to the inverted convex portion. It is configured as a continuation of a signal waveform and a signal waveform corresponding to the boundary surface convex portion, and an output amount of the signal waveform corresponding to the inverted convex portion varies according to a change in polarity of a bias magnetic field applied to the magnetic head. A magnetic recording medium, characterized by being a medium. 3. An output amount of a signal waveform corresponding to the inverted convex portion fluctuates due to a change in polarity of the bias magnetic field.
When the magnetic recording medium of claim 2, wherein the small Kunar than the output of the signal waveform corresponding to the boundary surface protrusion. 4. An output amount of a signal waveform corresponding to the inverted convex portion, wherein an output derived from the inverted convex portion excited by a bias magnetic field applied to the magnetic recording medium and the output amount below the inverted convex portion. 3. The magnetic recording medium according to claim 2, wherein the magnetic recording medium fluctuates due to interference with a leakage magnetic flux of the magnetization reversal pattern. 5. The fixed information recorded on a magnetic recording medium,
A method for reproducing by a magnetic head, wherein the magnetic recording medium comprises a first magnetic layer made of a first magnetic powder having a coercive force of 250 to 4000 Oe on a base made of a non-magnetic material; at least it laminated and a second magnetic layer consisting of the second magnetic powder, a plurality of magnetization reversal pattern is formed on the first magnetic layer on one surface of the second magnetic layer, the magnetization reversal patterns
The second magnetic powders are densely arranged on the two boundary surfaces sandwiched therebetween, and are integrated with each other, so that the magnetization reversal pattern is formed.
At least one or more inverted protrusions formed on the upper surface;
At least one or more boundary surface protrusions formed by densely packed second magnetic powder are formed on a boundary surface between the two magnetization reversal patterns so as to be mixed along a reading direction of magnetic recording; The information is composed of the one or more inversion protrusions and the one or more boundary surface protrusions, and is fixed by scanning the magnetic head along the reading direction of the magnetic recording of the second magnetic layer. Reproducing information to obtain a reproduction signal, wherein the reproduction signal has a signal waveform corresponding to the inverted convex portion;
Changing the output amount of the signal waveform corresponding to the inversion projection by changing the polarity of the bias magnetic field applied to the magnetic recording medium at the time of reproduction. A method for reproducing fixed information from a magnetic recording medium. 6. An output amount of a signal waveform corresponding to the inversion convex portion is changed from an output amount of a signal waveform corresponding to the boundary surface convex portion by changing a polarity of a bias magnetic field applied to the magnetic recording medium. 6. The method for reproducing fixed information from a magnetic recording medium according to claim 5, wherein 7. An output amount of a signal waveform corresponding to the inverted convex portion, wherein an output derived from the inverted convex portion excited by a bias magnetic field applied to the magnetic recording medium and the output amount below the inverted convex portion. 6. The method according to claim 5, wherein the variation is caused by interference with the leakage flux of the magnetization reversal pattern.