WO1998055962A1 - Support d'enregistrement magnetique et son procede d'utilisation - Google Patents
Support d'enregistrement magnetique et son procede d'utilisation Download PDFInfo
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- WO1998055962A1 WO1998055962A1 PCT/JP1998/002485 JP9802485W WO9855962A1 WO 1998055962 A1 WO1998055962 A1 WO 1998055962A1 JP 9802485 W JP9802485 W JP 9802485W WO 9855962 A1 WO9855962 A1 WO 9855962A1
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- Prior art keywords
- recording
- irreversible
- heating
- magnetic
- layer
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
- G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
- G06K19/06187—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code with magnetically detectable marking
- G06K19/06196—Constructional details
Definitions
- the present invention relates to a magnetic recording medium such as a magnetic card and a method for using the same.
- Japanese Patent Application Laid-Open No. H8-77662 discloses that an alloy having (saturation magnetization when crystalline) / (magnetization when amorphous) is 5 or more is a magnetic recording material.
- a magnetic recording medium having an irreversible recording layer has been proposed.
- This magnetic recording medium has an irreversible recording layer made of a recording material whose saturation magnetization changes irreversibly by heating. In this recording material, the saturation magnetization changes due to heating, but in order to return the saturation magnetization to the value before heating, it is necessary to heat the magnetic recording medium to the extent that deformation or melting occurs. Impossible and safe
- a first object of the present invention is to prevent falsification of data in a magnetic recording medium having an irreversible recording layer that generates an irreversible saturation magnetization change by heating.
- a second object of the present invention is to suppress the output fluctuation of the magnetic recording medium while achieving the first object.
- a third object of the present invention is to improve the confidentiality of recorded information while achieving the first object.
- a fourth object of the present invention is to make it possible to easily detect falsification of recorded information while achieving the first object.
- a fifth object of the present invention is to make it more difficult to falsify or forge a medium while achieving the first object.
- the first to fifth object of, r first aspect achieved respectively by the first to fifth aspect of the following
- At least a part of the substrate has an irreversible recording layer containing an irreversible recording material whose saturation magnetization changes irreversibly by heating, and fixed information of a medium is recorded on at least a part of the irreversible recording layer.
- a plurality of heating bars whose saturation magnetization is irreversibly changed are arranged almost in parallel with each other, and an arrangement pattern of the heating bars or a non-heating bar existing between adjacent heating bars.
- the irreversible recording layer comprises a soft magnetic material layer containing the soft magnetic material and an irreversible recording material layer containing the irreversible recording material.
- the irreversible recording layer contains a hard magnetic material, and the hard magnetic material has substantially no change in saturation magnetization due to heating, and has a higher coercive force than the irreversible recording material.
- the magnetic recording medium according to any one of (1) to (5), which is expensive.
- the irreversible recording layer comprises an irreversible recording material layer containing the irreversible recording material and a hard magnetic material layer containing the hard magnetic material.
- At least one track element having at least one recording track, in which heating bars are arranged in a barcode shape, is arranged at least two substantially in parallel to one recording track.
- the magnetic recording medium according to any one of (1) to (8), wherein at least a part of the recording track has an asymmetric region in which the arrangement pattern of the heating bars differs between at least two track elements.
- An irreversible recording layer is provided on at least a part of the substrate, and the irreversible recording layer is formed on a magnetic recording medium containing an irreversible recording material whose saturation magnetization changes irreversibly by heating.
- a magnetic recording medium that performs heating so that the arrangement pattern of the heating bars or the arrangement pattern of the non-heating bars existing between the adjacent heating bars is obtained by encoding the recording information by a frequency modulation method or a phase modulation method. How to use
- the magnetization direction of the irreversible recording layer is changed while applying a bias magnetic field whose direction is opposite to the one direction and does not reverse the magnetization of the hard magnetic material.
- a direction in which the direction is the one direction a process of detecting a change in magnetization of the irreversible recording layer while applying a bias magnetic field, and the hard magnetic material is magnetized in one direction.
- the direction is opposite to the one direction, and a process of detecting a change in magnetization of the irreversible recording layer while applying a bias magnetic field that does not reverse the magnetization of the hard magnetic material is performed. How to use the media.
- the magnetic recording medium has at least one recording track in the irreversible recording layer
- At least two track elements in which the heating bars are arranged in a barcode shape are arranged substantially parallel to each other to form one recording track, and at least a part of the recording track has at least two recording elements. Control the heating means at the time of recording so that there is an asymmetric region where the arrangement pattern of the heating bars differs between the track elements (11) ⁇ (15) Use of the magnetic recording medium according to any one of (1) to (5).
- FIG. 1 is a diagram for comparing and describing digital signal encoding methods.
- FIG. 2 is a plan view showing a configuration example of the magnetic recording medium according to the first embodiment.
- FIG. 3A is a plan view showing the relationship between the scanning direction of the heating means at the time of recording (at the time of heating) and the scanning direction of the reproducing head at the time of reproduction in the second mode
- FIG. 6 is a graph showing a reproduction output (differential output of magnetization) in the case of FIG.
- FIG. 4 (a) is a plan view showing the relationship between the scanning direction of the heating means at the time of recording (heating) and the scanning direction of the reproducing head at the time of reproduction according to the second mode, and FIG. It is a graph showing the reproduction output (differential output of magnetization) in that case.
- FIG. 5 (a) is a graph showing a reproduction output (magnetization differential output) in the embodiment of the second embodiment
- FIG. 5 (b) is a graph showing a reproduction output (magnetization differential output) of the comparative example. is there.
- FIG. 6 is a cross-sectional view illustrating a configuration example of a magnetic recording medium used in the third embodiment.
- FIGS. 7A and 7B are cross-sectional views illustrating a configuration example of a magnetic recording medium according to a third embodiment.
- Figure 8 is a graph showing the saturation magnetization M s of F e 58 A 1 alloy flat powder, the relationship between the heating temperature.
- FIG. 9 is a graph showing the relationship between the leakage output measured on the surface of the irreversible recording layer functioning as a magnetic shield layer and the thickness of the irreversible recording layer.
- FIG. 10 is a graph showing the relationship between the decay rate of the leakage output obtained from the results of FIG. 9 and the thickness of the irreversible recording layer.
- FIG. 11 is a sectional view showing a configuration example of a magnetic recording medium used in the fourth embodiment.
- FIGS. 12A and 12B are cross-sectional views showing a configuration example of the magnetic recording medium according to the fourth embodiment.
- FIG. 12A and 12B are cross-sectional views showing a configuration example of the magnetic recording medium according to the fourth embodiment.
- FIG. 13 is a cross-sectional view schematically showing a state where recording is performed by heating a part of the irreversible recording layer 4 in the fourth embodiment.
- Fig. 14 is a graph schematically showing the differential output when the irreversible recording layer 4 heated as shown in Fig. 13 is reproduced by applying a forward bias magnetic field, and (a) is irreversible.
- Fig. 15 is a graph schematically showing the differential output when the irreversible recording layer 4 heated as shown in Fig. 13 is reproduced by applying a reverse bias magnetic field.
- the differential output of the recording material layer 141, (b) is the differential output of the hard magnetic material layer 144, and (c) is the differential output of the entire irreversible recording layer 4.
- FIG. 16 is a cross-sectional view schematically showing a state in which a part of the irreversible recording layer 4 has been removed and data has been altered.
- FIG. 17 is a graph schematically showing the differential output when reproducing by applying a forward bias magnetic field to the irreversible recording layer 4 partially removed as shown in FIG.
- (a) is the differential output of the irreversible recording material layer 141
- (b) is the differential output of the hard magnetic material layer 144
- (c) is the differential output of the entire irreversible recording layer 4.
- FIG. 18 is a graph schematically showing the differential output when reproducing by applying a reverse bias magnetic field to the irreversible recording layer 4 partially removed as shown in FIG.
- (a) is the differential output of the irreversible recording material layer 141
- (b) is the differential output of the hard magnetic material layer 144
- (c) is the differential output of the entire irreversible recording layer 4.
- Fig. 19 (a) is a cross-sectional view showing the heating pattern of the irreversible recording layer and its removal pattern, and (b) the reproduction while applying a forward bias magnetic field to the irreversible recording layer of (a). (C) shows the differential output when reproduction is performed while applying a reverse bias magnetic field to the irreversible recording layer of (a). This is a graph.
- FIG. 20 (a) is a plan view of a magnetic card which is an example of a magnetic recording medium used in this embodiment.
- (B) is an enlarged view of a part of the recording track shown in (a), showing a plan view showing details of the heating bar arrangement pattern, and a reproduction differential output pattern of this area of the recording track.
- (C) is a plan view showing a state where the recording track shown in (b) is divided into two track elements.
- D) is a plan view when one of the track elements divided from the recording track in (c) is an independent recording track, and a reproduction differential output pattern of the recording track.
- (E) is a plan view when the other track element divided from the recording track in (c) is an independent recording track, and a reproduction differential output pattern of the recording track.
- 21A is a plan view showing a heating bar arrangement pattern in a recording track of the magnetic recording medium used in this embodiment.
- (B) is a reproduction differential output pattern of this recording track.
- (C) is a reproduction differential output pattern when the recording track shown in (a) is divided into two track elements, and the upper track element is made an independent recording track.
- (D) is a reproduction differential output pattern when the recording track shown in (a) is divided into two track elements and the lower track element is made an independent recording track.
- FIG. 22 (a) is a plan view showing a heating bar arrangement pattern in a recording track of the magnetic recording medium used in this embodiment.
- (B) is a reproduction differential output pattern of this recording track.
- (C) is a reproduction differential output pattern when the recording track shown in (a) is divided into two track elements, and the upper track element is made an independent recording track.
- (D) is a reproduction differential output pattern when the recording track shown in (a) is divided into two track elements and the lower track element is made an independent recording track.
- Fig. 1 schematically shows the modulation waveform when digital signals are recorded by various modulation methods on the irreversible recording layer, which causes irreversible saturation magnetization change by heating.
- Figure 1 shows an example where the saturation magnetization increases due to heating.
- Most of the methods shown in Fig. 1 use magnetization reversal, but the concept of magnetization reversal does not exist in the irreversible recording layer because the change in saturation magnetization due to the presence or absence of heating is used.
- by performing signal processing on the reproduced output from the irreversible recording layer decoding similar to that of a normal magnetic recording layer using magnetization reversal is possible.
- recording is performed on the irreversible recording layer by the FM (frequency modulation) method or the PV1 (phase modulation) method.
- the FM method is a method in which the waveform is inverted according to ⁇ 1 ⁇ , and the waveform is inverted once even between bits.
- the modulation method is ⁇ 1 ⁇ when the number of waveform inversions within the data-bit interval is 2, and ⁇ 0 ⁇ when the number of inversions is 1.
- the direction of waveform inversion is reversed between ⁇ 1 ⁇ and ⁇ 0 ⁇ . That is, the same sign corresponds to the rising force “1” and falling force '0 ⁇ of the pulse at the center of the data bit. Is followed by data / bit boundaries.
- waveform inversion always occurs in one bit, so if a new heating bar is added to the heating bar array coded by the FM method or the PM method by additional heat (append), the FM It does not become a signal or PM signal, and reading becomes impossible. Therefore, when the fixed information is recorded by the FM method or the PM method, the data cannot be falsified by additional recording.
- the pulse rises when moving from the non-heating bar (bar-shaped region existing between the heating bars) to the heating bar, and the pulse falls when moving from the heating bar to the non-heating bar.
- the effect of using the FM method or the PM method is similarly realized.
- FIG. 4A is a plan view showing a magnetic card having an irreversible recording layer 4 on a base 2.
- heating bars 41 are formed in the irreversible recording layer 4 in a bar code shape at equal intervals, and the area other than the heating bars 41 is a non-heating bar 42.
- the running direction of the thermal head during heating is the X direction in the figure.
- the magnetic head is scanned with a reproducing head to detect a change in magnetization of the irreversible recording layer.
- the scanning direction of the reproducing head is the X direction in the figure, which is the same as the scanning direction of the thermal head.
- a coating type irreversible recording layer containing a resin binder has poor thermal conductivity.
- the thermal head first heats the heat storage layer, and thereby heats the irreversible recording layer.
- the entire heating bar 41 is not uniformly heated, resulting in uneven heating. Therefore, when the scanning direction of the general head and the scanning direction of the reproducing head are coincident as shown in FIG. 4 (a), the heating bar 41 is shifted to the non-heating bar 42 as shown in FIG. 4 (b).
- the differential output at the time of transition from the heating bar 42 to the heating bar 41 becomes small. As a result, it is necessary to lower the threshold value of the reproduction output, and as a result, it becomes more susceptible to noise and causes an error.
- the heating means runs in a direction (Y direction) substantially perpendicular to the reading direction (X direction) during playback. Inspect and record. Therefore, the uneven heating generated in the scanning direction of the heating means does not affect the reproduction signal, and a uniform magnetization change signal (differential output) as shown in FIG. 3 (b) is obtained.
- the second mode is used for recording information (fixed information) recorded in advance at the time of shipping the magnetic recording medium. If applied, the fixed information can be reproduced without error by the effect of the second aspect.
- a normal magnetic recording layer is provided between the base and the irreversible recording layer, and the irreversible recording layer also functions as a magnetic shield layer.
- the magnetic permeability of the irreversible recording layer generally decreases by heating, so that the magnetic shielding effect also generally decreases.
- the magnetic shielding effect generally increases by heating.
- the used processing of the magnetic card can be performed by utilizing such a change in the magnetic shield effect. For example, when using an irreversible recording material whose saturation magnetization is reduced by heating, when the magnetic card has been used, the entire irreversible recording layer is heated so that the magnetic shielding effect is almost eliminated.
- a card reader Is set so that a magnetic force that is not magnetically shielded is determined to be unusable, the unauthorized use of a used magnetic card can be prevented.
- the irreversible recording layer shows a sufficient magnetic shielding effect, and the confidentiality of the information recorded on the magnetic recording layer is good.
- an irreversible recording material whose saturation magnetization increases by heating when used, when the magnetic card has been used, a process of heating the entire irreversible recording layer to produce a magnetic shielding effect is performed. If the card reader is set so as to determine that the magnetically shielded card cannot be used, the used processing can be performed.
- the irreversible recording material When only the irreversible recording material is used as the magnetic shielding material, a sufficient magnetic shielding effect can be obtained before heating (when the saturation magnetization decreases due to heating) or after heating (when the saturation magnetization increases due to heating). If not, either a soft magnetic material commonly used as a magnetic shield material is included in the irreversible recording layer, or an irreversible recording material layer containing an irreversible recording material and a soft magnetic material layer containing a soft magnetic material are laminated. Then, the irreversible recording layer may be formed. However, if the addition of the soft magnetic material ⁇ the lamination of the soft magnetic material layer always provides a magnetic shield effect of a certain level or more, the change in the magnetic shield effect due to heating will not be sufficient, and becomes impossible. Therefore, it is necessary to appropriately set the addition amount of the soft magnetic material ⁇ the thickness of the soft magnetic material layer and the like so that a sufficient change in the magnetic shielding effect can be obtained by heating.
- information recorded by heating the irreversible recording material in the irreversible recording layer is read out as follows. First, magnetic information is read from the magnetic recording medium without magnetically saturating the irreversible recording layer. At this time, the magnetic flux from the magnetic recording layer leaks according to the write pattern on the irreversible recording layer, and a reproduction signal corresponding to this leak is obtained. Next, reproduction is performed with the irreversible recording layer magnetically saturated. The difference between the reproduced signal obtained at this time and the reproduced signal obtained without magnetically saturating the irreversible recording layer is calculated. Then, the recording pattern (heating pattern) of the irreversible recording layer can be read. Since the information recorded in the irreversible recording layer is due to a change in the magnetization of the irreversible recording material, tampering is substantially impossible.
- the irreversible recording layer is mechanically damaged, for example, a false signal can be generated.
- a non-magnetic region can be formed by cutting off a part of the irreversible recording layer. Therefore, in a magnetic recording medium having an irreversible recording layer whose saturation magnetization decreases by heating, the cut-out region is written (heated). Can be mistaken for an area. Therefore, a magnetic recording medium having such an irreversible recording layer requires a reproducing method that can detect such tampering.
- a hard magnetic material is contained in the irreversible recording layer in addition to the irreversible recording material.
- a magnetic recording medium in which an irreversible recording layer 4 is formed by laminating a hard magnetic material layer 144 and an irreversible recording material layer 141 Take for example.
- the magnetic information to be reproduced is recorded by heating the irreversible recording material into a predetermined pattern.
- the hard magnetic material layer 144 needs to be in a state of being magnetized in one direction.
- a force for detecting a change in magnetization while applying a bias magnetic field (hereinafter referred to as a forward bias magnetic field) whose direction is the one direction to the irreversible recording layer 4 ⁇
- a bias having a direction opposite to the direction of the forward bias magnetic field (hereinafter referred to as a reverse bias magnetic field).
- the irreversible recording material layer 141 is magnetized in the direction of each bias magnetic field by application of a forward bias magnetic field or a reverse bias magnetic field.
- FIG. 14 shows a case where reproduction is performed on the medium shown in FIG. 13 while applying a forward bias magnetic field
- FIG. 15 shows a case where reproduction is performed while applying a reverse bias magnetic field.
- the irreversible recording material layer 141 has a saturation magnetization that is reduced (substantially disappears) by heating.
- (A) of each figure is a differential output when it is considered that the irreversible recording material layer 141 exists alone, and (b) of each figure shows a differential output of the hard magnetic material layer 144 alone. This is the differential output when it is considered to exist.
- (C) of each figure is a differential output of the irreversible recording layer 4 which is a laminate of both layers.
- the hard magnetic material layer 144 is magnetized in one direction, and since the hard magnetic material does not change its saturation magnetization by heating, the hard magnetic material layer 144 is differentiated as shown in (b) of each part. The output is zero. Therefore, the differential output of the irreversible recording layer 4 reflects the magnetization change pattern of the irreversible recording material layer 141 and the direction of the bias magnetic field. However, the magnitude of the differential output of the irreversible recording layer 4 (absolute Is affected by the magnitude of the magnetization of the hard magnetic material layer 144, and the magnitude and direction of the bias magnetic field.
- FIG. 16 shows an example in which the recorded information is falsified and falsified by partially removing the irreversible recording layer 4 with a force cutter knife or the like.
- the hard magnetic material layer 144 is magnetized in one direction with this modified medium, and the reproduction is performed by applying a forward bias magnetic field or a reverse bias magnetic field, the irreversible recording material layer 141 becomes single.
- the differential output when it is considered to exist is shown in Fig. 17 (a) and Fig. 18 (a), which is the same as in the case of normal heating recording without alteration. Therefore, data tampering cannot be detected only with the irreversible recording material layer 141.
- the differential output is as shown in (b) of each figure, which is different from the case where normal heating recording is performed. Since the hard magnetic material layer 144 is partially removed, a magnetization change occurs at the end of the removed region, and the magnetization of the hard magnetic material layer 144 is reversed bias magnetic field. As shown in the figure, the differential output of (b) in both figures has the same pattern of polarity change, as a result, and as a result, the differential output of the entire irreversible recording layer 4 becomes (c) of each figure. It becomes what is shown in. That is, as shown in Fig. 17 (c) and Fig. 18 (c), the differential output (absolute value) differs greatly depending on the direction of the bias magnetic field, so that tampering can be easily detected by comparing the two.
- the present invention is effective in discovering alteration by removing a heated region.
- the irreversible recording layer 4 is separated into the hard magnetic material layer 144 and the irreversible recording material layer 141 has been described as an example.
- the recording layer 4 has a single-layer structure and includes both an irreversible recording material and a hard magnetic material, it is possible to detect data tampering by the completely same operation.
- a single layer of irreversible recording layer containing both irreversible recording material and hard magnetic material is used, it becomes impossible to remove only the irreversible recording material, and thus the authenticity determination by the above-described reproduction method is performed. Will be more reliable.
- information may be recorded in the hard magnetic material layer 144 as well.
- the information recorded in the hard magnetic material layer 143 is temporarily held in a semiconductor memory or the like, and then the hard magnetic material layer 143 is magnetized in one direction as described above to perform reproduction. After that, after the reproduction, the held information may be written back to the hard magnetic material layer 144.
- a magnetic stripe on which data is recorded in a bar code shape is divided into two in the longitudinal direction, and each of the divided pieces is read by another card or a force-shaped base reading area.
- the value information such as the amount information, issue number, store number, expiration date, etc. and the sign information at the time of card issuance are copied as they are, so the loss to the force issuer is large.
- the present invention is based on the first aspect. And if necessary, at least one of the second to fifth aspects is combined. Hereinafter, details of each embodiment will be described.
- FIG. 2 shows a configuration example of the magnetic recording medium of this embodiment.
- This magnetic recording medium has an irreversible recording layer 4 and a magnetic recording layer 3 on the surface of a substrate 2.
- the irreversible recording layer 4 is a layer containing an irreversible recording material described later, and whose saturation magnetization changes irreversibly by heating.
- the irreversible recording layer 4 When recording on the irreversible recording layer 4, the irreversible recording layer 4 is heated in a predetermined pattern by scanning with a heating means such as a thermal head and a laser beam. At the time of reproduction, a normal ring-type magnetic head and a reproducing head such as a magnetoresistive (MR) magnetic head are used. A change in the magnetization according to is detected, and a reproduction signal is obtained. During reproduction, the irreversible recording layer 4 After applying the field, the magnetization change pattern is detected, or the magnetization change pattern is detected while applying a DC magnetic field.
- a heating means such as a thermal head and a laser beam.
- a normal ring-type magnetic head and a reproducing head such as a magnetoresistive (MR) magnetic head are used.
- a change in the magnetization according to is detected, and a reproduction signal is obtained.
- the irreversible recording layer 4 After applying the field, the magnetization change pattern is detected, or the magnetization change pattern is detected while applying a DC
- the portion heated at the time of recording is not magnetized or has a small magnetization, so that at the time of reproduction, a magnetization pattern corresponding to the heating pattern at the time of recording can be detected.
- the saturation magnetization of the recording material increases due to heating, it is possible to detect a magnetization pattern corresponding to the heating pattern during recording during reproduction.
- the irreversible recording layer 4 is heated in advance to form a fixed information recording area.
- the fixed information recording area is an area in which a plurality of heating bars 41 whose saturation magnetization changes irreversibly are arranged in a bar code shape, and a non-heating bar 42 exists between adjacent heating bars. ing. And these multiple heating bars 41 or non-heating bars
- the array pattern of 42 is generated by coding fixed information by the FM method or the PM method as shown in FIG.
- the fixed information recording area extends over the entire surface of the irreversible recording layer 4 and coincides with each other.
- the fixed information recording area may be formed only on a part of the irreversible recording layer 4.
- the type of fixed information recorded in the fixed information recording area is not particularly limited, but is preferably, for example, value information or sign information. Specific examples of such information include, for example, information on the amount of money issued when a magnetic card is issued, an issue number, a store number, an expiration date, and the like, and an encrypted version thereof.
- FIGS. 1 and 2 are for a medium having an irreversible recording layer whose saturation magnetization increases by heating.
- the effects of the present invention can be similarly realized even with a medium having In this case, the array pattern encoded by the recorded information may be that of a heated bar or that of a non-heated bar, but in the former case, the direction of the bias magnetic field applied during reproduction must be reversed. There is.
- information may be additionally recorded on the irreversible recording layer 4.
- the arrangement of the heating bar or the non-heating bar that carries the information to be additionally written may be coded by the FM method or the PM method, like the above-described arrangement pattern relating to the fixed information.
- the irreversible recording layer is heated from the surface side by a heating source such as a thermal head.
- a heating source such as a thermal head.
- the heating area isothermal area
- the layer is too thick, in a region far from the heating source (deep region), an insufficient heating region is generated between adjacent heating dots.
- the reproduced output since a change in magnetization caused by the region where the temperature is not sufficiently increased is detected as noise, the reproduced output itself does not change much, but the SN ratio of the reproduced signal tends to be low.
- the thickness of the irreversible recording layer is preferably set to 1 ⁇ or less.
- the lower limit of the thickness of the irreversible recording layer is not particularly limited because it greatly varies depending on the method for forming the irreversible recording layer. It is about 1 ⁇ , preferably about 0.1 im. If these layers are too thin, the output will be insufficient or it will be difficult to form a homogeneous layer.
- the surface roughness (R a) of the surface of the irreversible recording layer is preferably 1 m or less. If the surface roughness is large, the S / N ratio will be significantly lower.
- the surface roughness (R a) is specified in JIS B0601.
- the recording on the irreversible recording layer may be either in-plane magnetic recording using magnetization in the in-plane direction of the layer or perpendicular magnetic recording using magnetization in the direction perpendicular to the layer.
- Irreversible recording materials are materials whose saturation magnetization changes irreversibly by heating.
- the rate of change of the saturation magnetization 4 ⁇ Ms of the irreversible recording material that is, (4 ⁇ Ms after heating / 4Ms before heating) or (4 ⁇ s before heating, 4 ⁇ s after heating) is preferable.
- the above-mentioned saturation magnetization is in a normal ambient temperature range (for example, 10 to 40 C). Further, in this specification, the irreversible change of the saturation magnetization due to heating means that when applied to a magnetic card or the like, the temperature can be reused after heating (for example, about 500 ° C, preferably 400 ° C). It means that the saturation magnetization changes irreversibly when heated up to about C).
- the temperature at which the irreversible recording material starts to show a saturation magnetization change when the temperature is raised is preferably 50 to 500 ° C, more preferably 100 to 500 ° C, and still more preferably 150 to 400 ° C. It is desirable that the above-described saturation magnetization change rate be obtained in such a temperature range. If the temperature at which the change in saturation magnetization starts to appear is too low, it becomes unstable with respect to heat and reliability is reduced. In addition, the vicinity of the heated area is easily affected, making accurate recording difficult. If the temperature at which the saturation magnetization starts to change is too high, the heating temperature required for recording becomes high, so that it is difficult to use a resin having low heat resistance for the base, and the recording device becomes expensive. I will.
- a thermal head or the like is used for heating the irreversible recording layer.
- the surface temperature of the thermal head is about 400 ° C, and it is possible to raise the temperature of the irreversible recording layer to about 300 ° C by bringing it into contact with a magnetic recording medium.
- the temperature at a position at a depth of about 10 ⁇ from the surface of the irreversible recording layer rises to about 100 to 140 ° C.
- the heating time for recording is not particularly limited, but usually, the saturation magnetization changes sufficiently with heating of 3 ms or less, and a sufficient saturation magnetization change is realized with heating of 2 ms or less.
- the lower limit of the heating time depends on the temperature reached, but is usually about 0.5 ms.
- the Curie temperature of the irreversible recording material is not particularly limited, and may be any Curie temperature at which irreversible recording and reproduction thereof are possible.
- the form of the irreversible recording material is not particularly limited, and may be, for example, any of a ribbon shape, a thin film shape, and a powder shape.
- a thin ribbon of a recording material is prepared by a liquid quenching method such as a single roll method, and this is affixed to the substrate surface, or a thin film forming method such as a sputtering method or a vapor deposition method.
- a thin film of a recording material is formed on the surface, or a powder obtained by pulverizing a ribbon of the recording material, or a powder produced by a water atomizing method, a gas atomizing method, etc.
- a medium stirring mill has a fixed grinding container and a stirring shaft (also called an agitator) inserted therein.
- the grinding container is filled with a grinding medium (balls, beads, etc.) together with a material to be ground.
- This is a device that crushes the material to be ground by rotating the stirring shaft at high speed to generate frictional shearing force between the crushing media.
- a shear force acts on the particles.
- irregular phase progresses, and higher saturation magnetization can be obtained.
- the flat particles are used, the surface properties of the coating film are improved, and the magnetic recording / reproducing characteristics and the thermal conductivity during heating are improved.
- the specific composition of the irreversible recording material is not particularly limited, the following materials are preferably used.
- Ni-based alloy In this alloy, the composition in which the saturation magnetization increases by heating and crystallizing the amorphous state is selected.
- Ni-based alloys include M (M is at least one element selected from the group consisting of B, C, Si, P and Ge) as a metalloid element in addition to Ni Are preferred. By containing these elements, it is easy to change from amorphous to crystalline, and it is easy to keep the crystallization temperature within a preferable range.
- M is preferably at least one of B, C and P, and more preferably B and Z or C.
- alloys containing B and C are preferable because of their high saturation magnetization and low temperature required for crystallization.
- Elements other than the above include, for example, Fe, Co, Y, Zr, Gd, Cu, Sn, Al, and Cr.
- Fe and Co are included in the form of substituting a part of Ni, and these substitutions increase the crystallization temperature slightly and increase the saturation magnetization.
- the Ni content in the Ni-based alloy is preferably 65 to 90 atoms. /. It is more preferably 73 to 83 atomic%. If the amount of Ni is too small, the crystallization temperature will be high, and 4 ⁇ s when heated to make it crystalline will be low. On the other hand, if the amount of Ni is too large, it becomes difficult to make the material amorphous during the production of the irreversible recording material. When the Ni-base alloy contains B and C, the saturation magnetization during crystallization generally increases with the increase in the amount of C.However, if the amount of C is too large, the crystallization temperature rises. B + C) is preferably less than 0.45. When a part of Ni is replaced by Fe and / or Co, it is preferable that Fe + Co in the alloy is not more than 10 atomic%. The saturation magnetization at the time of the crystal quality increases.
- Mn—M_ (metalloid) _ based alloy In this alloy, the composition in which the saturation magnetization increases by heating and crystallizing the amorphous state is selected.
- This alloy contains at least one metalloid element M in addition to Mn.
- the metalloid element M at least one element selected from the group consisting of Ge, A1, B, C, Ga, Si and Cr is preferable.
- the inclusion of the element M facilitates the change from amorphous to crystalline, and also facilitates setting the crystallization temperature within a preferred range.
- Ge or A1 of M the saturation magnetization is increased, and the use of Ge is preferable, because the crystallization temperature is lowered.
- a 1 and / or Si are added in addition to Ge, extremely high saturation magnetization is obtained.
- the addition of A1, Z, or Si significantly reduces the saturation magnetization before heating. Therefore, these additions contribute to an increase in the ratio of the saturation magnetization before and after heating.
- addition amount of A 1 + Si there is no particular lower limit on the addition amount of A 1 + Si. Normally, it is preferably 0.1 atomic% or more. Further, the addition amount of A 1 is preferably 6 atomic% or less, and the addition amount of Si is preferably 10 atoms. /. It is preferable that A 1 + Si not exceed 12 atomic%. If the amount of A 1 or Si added is too large, the saturation magnetization after heating will be rather low.
- the crystallization mechanism of the Mn-M alloy is not particularly limited, it is generally considered that crystallization is caused by the precipitation of a compound of Mn and another element, thereby increasing the saturation magnetization.
- a compound of Mn and another element For example, when Ge is included, at least a ferromagnetic M n 5 Ge phase is precipitated.
- at least a ferromagnetic M n “A 1 phase is precipitated.
- the preferred range of the Mn content in the alloy depends on the type of M contained in the alloy, and may be appropriately determined so as to achieve the function and effect of the irreversible recording material. If it is 0 atomic%, the main component is iVI n and Ge, for example, Mn—Ge alloy, Mn—Ge—A1 alloy, Mn—Ge—S ⁇ alloy M
- the Mn content is preferably 40 to 80 atoms. /. More preferably, it is 45 to 75 atomic%, and the Mn content in the case of the Mn-A1 alloy is preferably 45 to 60 atomic%. /. More preferably, 50 to 55 atoms 0 /. It is.
- This alloy is an alloy containing iMn and Sb.
- the Mn content in the alloy may be appropriately determined so as to achieve the function and effect of the irreversible recording material, but is preferably 40 to 75 atomic%, more preferably 44 to 66 atomic%, More preferably, 58 atom% to 66 atom. /. Most preferably 60-66 atoms. /. It is. If the Mn content is too low, the saturation magnetization before and after heating will both be small, and the change ratio of the saturation magnetization will also be small. On the other hand, when the Mn content is high, the saturation magnetization usually increases due to heating, but when the Mn content is too high, the saturation magnetization after heating does not increase so much, making it difficult to read recorded information. .
- the alloy may contain the metalloid element M described above in addition to Mn and Sb.
- the addition of the element M generally allows the crystallization temperature to be lowered, thus facilitating recording.
- an antiferromagnetic element such as Cr
- the magnetization before heating decreases, and as a result, the change ratio of the saturation magnetization increases. Since the saturation magnetization decreases with the addition of M, the M content is usually preferably 15 atomic% or less.
- the saturation magnetization and coercive force of the alloy generally increase by heating, but when the Mn content is low, the saturation magnetization may decrease by heating. Also, depending on the type of element added in addition to Sb and the heating temperature, the saturation magnetization may be reduced by heating. However, since the change ratio of the saturation magnetization generally increases when the saturation magnetization is increased by the calorific heat, it is preferable to select the composition so as to show such a change in the saturation magnetization.
- This alloy is an alloy mainly composed of a force ⁇ F e, Mn and C mainly composed of F'e and Mn.
- the content of each element in the alloy mainly containing Fe and Mn is preferably Fe: 50 to 75 atoms 0 /. ,
- the saturation magnetization change rate before and after heating is low.
- the content of each element in the alloy mainly containing Fe, Mn and C is preferably
- the amount of C added is preferably 5 atomic% or more, and more preferably 10 atoms. /. Above. However, if the amount of C added is too large, the saturation magnetization change rate before and after heating will be low.
- the alloy may contain an element other than the above, for example, at least one of B, Si, A and Cr. However, if the content of these elements is too high, the rate of change in saturation magnetization before and after heating may be small. Therefore, the total content of these elements is usually preferably 30 atomic% or less. .
- the saturation magnetization of this alloy generally increases with heating, but when the C content is high, the saturation magnetization may decrease with heating.
- This alloy is a crystalline alloy, which undergoes an irreversible change in saturation magnetization with the irreversible transformation from disordered phase to ordered phase. Specifically, heating reduces saturation magnetization.
- This alloy contains 90 atomic% or more of Fe and A 1 in total, and preferably has an atomic ratio A 1 / (Fe + Al) representing the ratio of A 1 of 0.3 to 0.4. 5, more preferably 0.35 to 0.42.
- This alloy has a regular phase at equilibrium and exhibits almost no magnetization because it is paramagnetic.
- this alloy when this alloy is processed, that is, when it is quenched, for example, by a liquid quenching method ⁇ sputter method, vapor deposition method, or preferably further crushed, it becomes an irregular structure with lattice distortion, and the magnetism is dominated.
- the ferromagnetism changes because the environment of the Fe atom changes. Once the alloy has an irregular structure, the structure is relaxed by heating and the saturation magnetization is reduced, so that recording using the change in magnetization due to heating becomes possible.
- the equilibrium phase at room temperature of the Fe—A1 alloy in which A 1 Z (F e + A 1) is within the preferable range described above is a paramagnetic B 2 phase.
- the B 2 phase is composed of a combination of the B C C—F e lattice and the F e A 1 lattice of the C s C 1 structure, and the basic lattice has high symmetry.
- F e and A 1 are randomly substituted in atomic units according to the degree of processing, and vacancy ⁇ dislocations are introduced, losing the basic lattice regularity.
- the symmetry is remarkably reduced, and at the same time, magnetism develops.
- the basic lattice regularity is at least partially restored, and the saturation magnetization is reduced. However, it usually does not return to the state before processing.
- changing from an irregular phase to an ordered phase by heating means that the basic lattice regularity is restored at least partially by heating.
- the rule phase in this specification is a concept that includes not only the B2 phase in which no distortion is introduced but also the case where a part of the lattice asymmetry remains. The restoration of the basic lattice symmetry by heating can be confirmed by X-ray diffraction and electron beam diffraction.
- a 1 in this alloy is M ′ (M 1 is at least one of S i, G e, S n, S b, B i, Mo, W, Nb, T a, T i, Z r and H f Species).
- M 1 is at least one of S i, G e, S n, S b, B i, Mo, W, Nb, T a, T i, Z r and H f Species.
- F e of this alloy is, M '' (M 11 is, C o, N i, Mn , C r, at least one of V and C u) may be substituted with.
- M 11 is, C o, N i, Mn , C r, at least one of V and C u
- F e in M 11 improves the saturation magnetization change ratio.
- C r of the M 11 is extremely effective in improving corrosion resistance.
- the M 1 'content is too high, the initial saturation magnetization may be low, so the M''content in this alloy is 20 atoms. /. It is preferable to do the following.
- M 1 and M ′ 1 are treated as A 1 and Fe when calculating the above-described atomic ratio A iZ (F e + A 1).
- This alloy (Micromax '11 is, B, C, of at least one N and P) may be contained.
- M 111 when produced by the alloy quenching technique is likely to appear the disordered phase. It also acts to prevent the transition from the irregular phase to the ordered phase. Therefore, similarly to the M 1, showing the suppression obtain effects a decrease in the saturation magnetization during storage in a high-temperature environment. Moreover, almost no decrease in the initial saturation magnetization due to the addition of M ′ M is recognized. However, if the content of M 1 ′ 1 is too large, the rate of change in saturation magnetization will be low. Therefore, the content of M ′ ′′ is preferably set to 10 atomic% or less of this alloy.
- C of the M 111 is, for example, be incorporated dispersant (organic solvent) or al used when milling the alloy powder.
- this alloy usually contains oxygen as an unavoidable impurity in addition to the above elements. Oxygen is likely to be incorporated when grinding the alloy. In general, the content of oxygen is preferably suppressed to about 3 atomic% or less.
- the alloy should have a saturation magnetization of preferably 45 emu / g or more, more preferably 50 emu / g or more before heating. Desirably, the saturation magnetization is preferably reduced by 35 emu / g or more, more preferably 40 emu / g or more by heating.
- the saturation magnetization before heating and the decrease in saturation magnetization due to heating are within the above range, and the rate of change in saturation magnetization, that is, (saturation magnetization before heating Z saturation magnetization after heating), 2 or more, Preferably, if it is 3 or more, the SN ratio will be even better.
- the reproduction sensitivity can be improved by performing reproduction while applying a DC magnetic field as described above.
- the coercive force of this alloy is not particularly limited, and it may be a soft magnetic material.
- the above-mentioned saturation magnetization is in a normal ambient temperature range (for example, -10 to 40 ° C).
- This alloy is a type of Heusler alloy, is crystalline, and changes irreversibly from an antiferromagnetic phase to a ferromagnetic phase upon heating. In other words, it is an alloy whose saturation magnetization increases irreversibly by heating.
- composition (atomic ratio) of this alloy is the composition (atomic ratio) of this alloy.
- the magnetic recording layer 3 is a normal magnetic layer on which reversible recording is performed, and is provided as necessary.
- An example of how to use the magnetic recording layer is as follows. If the ID code of the magnetic card is recorded as fixed information on the irreversible recording layer, and other information is encrypted with this ID code and recorded on the magnetic recording layer, the contents of the magnetic recording layer of this magnetic force can be obtained. Even if the data is copied to the magnetic recording layer of another magnetic card having a different ID code, the other magnetic card cannot read regular information. In the irreversible recording layer, an ID code unique to each card can be recorded, and it is impossible to falsify the card.
- the magnetic recording layer When the magnetic recording medium of the present invention is used as a normal prepaid card, the magnetic recording layer records information such as the amount of money, the frequency, and other information generally required for the magnetic card. Of the information recorded on the magnetic recording layer, information that needs to be rewritten each time it is used, such as money or frequency, is recorded. That is, every time information is rewritten in the magnetic recording layer, it is additionally written in the irreversible recording layer. Even if the information in the magnetic recording layer has been tampered with, the information in the irreversible recording layer cannot be rewritten.
- the magnetic material included in the magnetic recording layer is not particularly limited, and may be appropriately selected from, for example, Ba ferrite / Sr ferrite. However, when the irreversible recording layer is heated, the magnetic recording layer is also heated. In the case of arrangement, it is preferable to use a magnetic material having high heat resistance.
- the magnetic recording layer may be provided separately from the irreversible recording layer. After forming the magnetic recording layer, an irreversible recording layer may be provided so as to overlap at least a part of the magnetic recording layer.
- the constituent material of the substrate on which the irreversible recording layer and the magnetic recording layer are formed is not particularly limited. Any of fat, metal, etc. may be used.
- a resin protective layer or an inorganic protective layer may be provided on the surface of the irreversible recording layer. Even when such a protective layer is provided, the above-mentioned limitation of the surface roughness (R a) of the irreversible recording layer is effective.
- FIG. 3A shows a configuration example of the magnetic recording medium according to the second embodiment.
- This magnetic recording medium has an irreversible recording layer 4 on the surface of a substrate 2.
- the scanning direction at the time of heating (the scanning direction of the heating means, the Y direction in the figure) is changed to the scanning direction at the time of reproduction (the scanning direction of the reproducing head, Direction).
- the intersection angle in both directions is most preferably 90 °, but may be any angle within an allowable range determined from the relationship between the setting of the reproduction output threshold value and the azimuth loss, for example, preferably 80 to 100 °. It is.
- a thermal head it is preferable to run in the Y direction by using a line head in which the heating dots are arranged in the X direction in the figure.
- FIGS. 6 and 7A and 7B An example of the configuration of the magnetic recording medium of this embodiment is shown in FIGS. 6 and 7A and 7B.
- These magnetic recording media have a magnetic recording layer 3 on the surface side of the substrate 2 and an irreversible recording layer 4 on the surface side of the magnetic recording layer 3.
- the irreversible recording layer 4 also functions as a magnetic shield layer.
- the irreversible recording layer 4 shown in FIG. 6 contains an irreversible recording material or contains an irreversible recording material and a soft magnetic material. Whether or not the soft magnetic material is added to the irreversible recording layer 4 and the amount of the soft magnetic material are determined so that an attenuation rate described later is preferably about 80% or more, more preferably about 90% or more. Good.
- the irreversible recording material described above Since the magnetic material generally has a lower magnetic permeability than permalloy or the like used as a magnetic shielding material, if the irreversible recording layer 4 contains only the irreversible recording material, the magnetic shielding effect generally tends to be insufficient. Therefore, it is generally preferable to add a soft magnetic material.
- the soft magnetic material / (irreversible recording material + soft magnetic material) in the irreversible recording layer is preferably 10% by weight or more, more preferably 20% by weight. %.
- the ratio of soft magnetic material / (irreversible recording material + soft magnetic material) is preferably 80% by weight or less, more preferably 60% by weight or less.
- the irreversible recording layer 4 shown in FIGS. 7A and 7B includes a soft magnetic material layer 142 and an irreversible recording material layer 141.
- the soft magnetic material layer 142 contains a soft magnetic material described later, and the irreversible recording material layer 144 contains the irreversible recording material described above.
- FIG. 7A the soft magnetic material layer 142 exists on the magnetic recording layer 3 side
- FIG. 7B the irreversible recording material layer 141 exists on the magnetic recording layer 3 side. In either case, a reproduced output can be obtained, but in order to increase the SN ratio when reproducing the information recorded in the irreversible recording material layer 141, irreversible as shown in Fig.
- the recording material layer 141 be present on the surface side of the medium. If the irreversible recording material layer 141 does not exist on the surface side of the medium, the heating of the irreversible recording material layer 141 becomes insufficient when heating from the medium surface side with a thermal head or the like. It is difficult to obtain an SN ratio.
- the thickness of the irreversible recording material layer 141 is preferably set to 1 ⁇ ⁇ ⁇ n ⁇ or less in order to secure the SN ratio of the reproduced signal.
- the soft magnetic material layer 142 may be formed by applying powder of a soft magnetic material together with a binder, or may be a thin film formed by a sputtering method or the like. Form.
- the thickness of the soft magnetic material layer may be appropriately determined so that a value of about 90% or more can be obtained as an attenuation factor described later, and is usually about 4 to 20 m, and preferably 5 to 10 ⁇ .
- the soft magnetic material is a soft magnetic metal whose saturation magnetization does not substantially change by heating, for example, a soft magnetic material whose change in saturation magnetization caused by heating to about 400 ° C and cooling is preferably 30% or less. It is composed of metal.
- the soft magnetic metal used in this embodiment is not particularly limited. That is, the one used for the conventional magnetic shield layer can be used, and for example, it may be appropriately selected from Fe—Si, Permalloy, Sendust and the like.
- FIGS. 11, 12 (a) and 12 (b) Examples of the configuration of the magnetic recording medium of this embodiment are shown in FIGS. 11, 12 (a) and 12 (b). These magnetic recording media have an irreversible recording layer 4 on the surface of a substrate 2.
- the irreversible recording layer 4 shown in FIG. 11 includes the irreversible recording material described above or includes an irreversible recording material and a hard magnetic material.
- the irreversible recording layer 4 shown in FIG. 12 includes a hard magnetic material layer 143 and an irreversible recording material layer 141.
- the hard magnetic material layer 143 includes a hard magnetic material described later, and the irreversible recording material layer 141 includes the irreversible recording material described above.
- FIG. 12A the hard magnetic material layer 143 exists on the base 2 side
- FIG. 12B the irreversible recording material layer 141 exists on the base 2 side.
- any of these configurations may be used.
- the configuration shown in FIG. 12 (a) can partially remove only the irreversible recording material layer 141. This makes it difficult to detect tampering. Therefore, preferably, FIG. 11 or FIG.
- the content of the hard magnetic material in the irreversible recording layer 4 may be appropriately determined so that tampering can be detected by the above-described operation.
- Material + hard magnetic material is 20-80 weight. /. It is preferred that If the content of the hard magnetic material is too small, Fig. 17 (b) and Fig. 18
- the thickness of the irreversible recording layer 4 in FIG. 11 and the thickness of the irreversible recording material layer 141 in FIG. 12 (a) are preferably set to 10 or less in order to secure the SN ratio of the reproduced signal.
- the hard magnetic material layer 143 may be formed by coating a hard magnetic material powder with a binder, or may be a thin film formed by a sputtering method or the like.
- the thickness of the hard magnetic material layer 143 is not particularly limited as long as tampering can be detected by the above-described action, and is usually 3 to 20 ⁇ . However, in the configuration shown in FIG. 12B, since the hard magnetic material layer 143 exists on the surface side of the irreversible recording material layer 141, the temperature of the irreversible recording material layer 141 is prevented from increasing during recording. It is preferable that the thickness be 15 ⁇ or less so as not to reduce the thickness.
- the hard magnetic material used in this embodiment is a material whose saturation magnetization does not substantially change by heating, for example, a hard magnetic material whose change in saturation magnetization caused by heating to about 400 ° C. and cooling is 30% or less. It is a magnetic material.
- the coercive force of the hard magnetic material may be higher than the coercive force of the irreversible recording material, and is preferably 30 Oe or more.
- the hard magnetic material may be appropriately selected from Ba ferrite, Sr ferrite, etc., but when the irreversible recording material is heated, the hard magnetic material is also heated. It is preferable that it has high property.
- the bias magnetic field used in this embodiment needs to be higher than the coercive force of the irreversible recording material, and the reverse bias magnetic field needs to be lower than the coercive force of the hard magnetic material.
- FIG. 20 (a) shows a plan view of an example of a magnetic card to which the fifth aspect is applied.
- This magnetic card has an irreversible recording layer 4, 14 on a substrate 2.
- FIG. 20 (b) is an enlarged view of a part of the asymmetric region 4100 shown in FIG. 20 (a).
- FIG. 20 (b) is an enlarged view of a part of the asymmetric region 4100 shown in FIG. 20 (a).
- the heating bar 41a, 42a, 43a exists in the truck element 40a
- the heating bar 41b, 42b, 43b exists in the truck element 40b.
- the two track elements are tightly integrated, but integration is not essential. As long as both track elements can be read by the magnetic head as a single recording track, a gap may exist between both track elements.
- FIG. 20 (c) is a plan view showing a state where the recording track is divided into two along with the base 2 in the length direction thereof, and the track element 40a and the track element 40b are separated.
- a heating bar 44a shorter than these heating bars is shown between the heating bars 42a and 43a of the track element 40a.
- a heating bar 44 b shorter than these heating bars is described between 41 b and 42 b.
- These short heating bars 44a and 44b are described in the sense that they may be formed incidentally when forming another heating bar, and are preferably not actually present. However, the presence of such a short heating bar does not affect magnetic reproduction.
- FIG. 20 (d) is a plan view showing a state in which one of the separated track elements 40a is attached to another card base to form an independent recording track.
- FIG. 20 (e) is a plan view showing a state in which the other track element 40b is attached to another card base to form an independent recording track.
- FIG. 20 (d) and FIG. 20 (e) also show the reproduced differential output pattern when each track element is magnetically reproduced.
- FIG. 20 (b) also shows the reproduced differential output pattern of the recording track 40, that is, the reproduced differential output pattern before the track element 40a and the track element 40b are separated.
- These regenerative differential output patterns have peaks corresponding to the edges of the heating bar.
- Comparison of Fig. 20 (d) and Fig. 20 (e) shows that both regeneration differential output It can be seen that the peak arrangements of the two patterns differ. Then, when the two reproduced differential output patterns are combined, the reproduced differential output pattern shown in FIG. 20 (b) is obtained.
- the detection level is set so that a relatively low peak is also detected as a signal, and reproduction is performed.
- FIG. 20 (d) and FIG. 20 (e) in which the track element 40a and the track element 40b in the recording track 40 are each independently a recording track, both the peak arrangement patterns are shown in FIG. ), It is not possible to reproduce the correct information. Therefore, if the recording track is composed of two track elements as shown in FIG. 20 (b), it becomes impossible to alter or forge the magnetic card by dividing the recording track into two.
- all the recording tracks be asymmetrical areas, and one of the recording tracks may be selected according to the data arrangement of the recording tracks or the importance of the data when there are a plurality of recorded data. Only the part can be an asymmetric region. Note that a plurality of asymmetric regions may exist in one recording track.
- the asymmetric region in this case is a region where the arrangement pattern of the heating bars is different between at least two of the three or more track elements.
- the minimum peak decreases as the number of track elements increases, and sufficient output cannot be obtained. From the recording track.
- FIGS. 21 (a) and 22 (a) show other examples of the configuration of a recording track having an asymmetric area.
- Each of the recording tracks 40 shown in these figures is composed of two track elements 40a and 4Ob, and both have an asymmetric region 4 10 FIG. 21 (b) and FIG. 22 (b)
- the reproduction differential output pattern of the recording track 40 shown in FIG. 21 (a) and FIG. 22 (a), respectively, and FIG. 21 (c) and FIG. (c) is the reproduction differential output pattern of the upper track element 40a alone shown in Fig. 21 (a) and Fig. 22 (a), respectively, and Fig. 21 (d) and Fig. 22 (d) are These are reproduction differential output patterns of the lower track element 40b alone shown in FIGS.
- the pattern of FIG 2 (b) is, Q find that is obtained by combining the pattern of the pattern and 2 2 of FIG. 22 (c) (d)
- the heating bar of the track element 40a and the heating bar of the track element 40b do not overlap in position in the recording track length direction. If the heating bar is formed by heating the position corresponding to the heating bar of the other track element, a single bar code pattern similar to the conventional recording track will be obtained, so duplication by dividing the recording track into two is possible. Will be. Therefore, in order to make the safety 1 "life higher, as shown in the asymmetric region 4100 in Fig. 21 (a), the heating bars of both track elements should be partially overlapped in the recording track length direction. It is preferable to set an array pattern.
- the magnetic recording medium used for this measurement had a 8.8 rn / m thick irreversible recording layer on the surface of a polyimide substrate having a thickness of 5.5 rn.
- This irreversible recording layer is obtained by dispersing a flat powder made of a crystalline alloy (atomic composition: Fe ⁇ A l ") whose saturation magnetization decreases by heating in a binder, applying the powder to a substrate, and then drying. is there.
- the type of information recorded on a recording track having an asymmetric area is not particularly limited, and may be fixed information which is recorded when a magnetic card is issued or used for the first time, and is not additionally recorded thereafter. Additional information that is added when used Well ,.
- the fixed information include value information and sign information.
- Specific examples of the value information and the sign information include, for example, the amount information at the time of issuance of the magnetic card, the issue number, the store number, the expiration date, and the like, and an encrypted version thereof.
- the additional information includes, for example, balance information.
- the recording track 14 does not have an asymmetric area.
- the asymmetric area may be provided in the plurality of recording tracks as necessary. Of course.
- Forming the asymmetric area on a recording track includes, for example, a method of running a plurality of thermal heads in the recording track width direction, using a single thermal head, scanning and length in the recording track width direction. And scanning in various directions, and using a single thermal head to scan while controlling the position distribution of heat-generating parts in the recording track width direction over time. it can.
- a normal ring type magnetic head or magnetoresistive effect type When reproducing, use a normal ring type magnetic head or magnetoresistive effect type.
- MR Magnetic resonance
- the alloy powder obtained by the water atomizing method was pulverized by a medium stirring mill to produce a flat alloy powder having an average particle diameter of 8 ⁇ m.
- the saturation magnetization of this alloy powder is reduced by heating.
- the alloy powder was crystalline immediately after quenching and after heating to 40 CTC.
- the irreversible recording layer with a thickness of 5.5 ⁇ was formed by applying a paint in which the flat powder was dispersed on the surface of a polyimide substrate with a thickness of 18 ⁇ , and drying it.
- a heating bar was formed on the irreversible recording layer of this sample.
- the arrangement pattern of the heating bar was specified information coded by FM method or PM method. Next, after heating the non-heated bar between the heated bars in various patterns, reading was attempted, but in any case, reproduction was not possible.
- the alloy powder obtained by the water atomizing method was pulverized with a medium stirring mill to produce a Fe 58 A 2 alloy flat powder having an average particle size of 8 ⁇ m. This alloy powder was crystalline immediately after quenching and after heating to 400 ° C.
- a 5.5 xm-thick irreversible recording layer was formed by applying a coating material in which the flat powder was dispersed on the surface of a polyimide substrate with a thickness of 18 ⁇ , and drying it.
- the irreversible recording layer of this sample is heated by scanning with a line head, and has a pattern in which a square heating bar of 8 mm on a side and a non-heating bar of the same size are continuous. A heating zone was formed.
- Figure 5 shows the differential output of magnetization when scanning with the playback head in the direction perpendicular to the scanning direction of the line head [equivalent to Fig. 3 (a)].
- Fig. 5 (b) shows the differential output of magnetization when scanning with the reproducing head in the same direction as the scanning direction of the line head [corresponding to Fig. 4 (a)].
- the alloy powder obtained by a water atomizing method was triturated with medium stirring mill to produce the F e 5 8 A 1 "alloy flat powder having an average particle diameter of 8 m.
- Heating temperature dependence of the saturation magnetization M s of the powder First, the alloy powder was heated at a heating rate of 10 ° CZmin using an infrared image furnace, kept at the temperature to be measured for 1 second, cooled with gas, and cooled to room temperature.
- the Ms was measured at room temperature at a maximum applied magnetic field strength of 10.0 kOe using a VSM (sample vibration type magnetometer) The measurement results are shown in Fig. 8. From Fig. 8, this alloy powder was It can be seen that the saturation magnetization is reduced by heating
- the alloy powder was crystalline immediately after quenching and also after heating to 400.
- a magnetic card sample was prepared by the following procedure.
- a magnetic paint in which Ba ferrite powder (coercive force is 2750e) is dispersed on the entire surface of one side of a polyimide substrate having a thickness of 150 ⁇ is dried to a thickness of 12 ⁇ m. It was coated so as to be ⁇ , magnetically oriented, and dried to form a magnetic recording layer.
- the alloy powder obtained by the water atomizing method was pulverized with a medium stirring mill to produce a flat Fe-Si alloy powder having an average particle diameter of 12 ⁇ .
- a magnetic coating material in which this powder was dispersed was applied to the surface of the magnetic recording layer and dried to form a soft magnetic material layer. Table 1 shows the thickness of the soft magnetic material layer.
- the irreversible recording layer had a laminated structure of a soft magnetic material layer and an irreversible recording material layer, but for comparison, the irreversible recording layer was composed of the soft magnetic material layer alone or the irreversible recording material layer alone.
- the dependence of the shield characteristics on the thickness of the irreversible recording layer was examined.
- the measurement conditions were the same as those of the above samples.
- Fig. 9 shows the results. From FIG. 9, it can be seen that the irreversible recording material layer has a larger leakage output and lower shield characteristics than the soft magnetic material layer.
- Fig. 9 shows the leakage output when the irreversible recording layer was magnetically saturated.
- the decay rate of the leakage output of each irreversible recording layer was determined based on the leakage output when the magnetic saturation occurred.
- Figure 10 shows the irreversible recording layer thickness dependence of the decay rate of the leakage output.
- a soft magnetic material layer with a thickness of 5 ⁇ is formed using a paint in which Sendust flat powder is dispersed, and the Cun A1 alloy flat powder with an average particle size of about 16 ⁇ m flattened by medium stirring is dispersed.
- a magnetic card sample was prepared in the same manner as in Example 3-1 except that an irreversible recording material layer having a thickness of 7 m was formed using the paint thus prepared.
- the surface roughness (R a) of the irreversible recording layer surface (irreversible recording material layer surface) is adjusted by changing the grinding time of the CUsMnA1 alloy powder by a medium stirring mill when preparing the sample. did. Table 2 shows the Ra of each sample.
- Table 2 shows that samples with a surface roughness (Ra) of more than 1 m have a significantly lower SN ratio and a lower decay rate, making them difficult to use.
- F e- S i by using a dispersion paint alloy flat powder to form a soft magnetic material layer having a thickness of 8 / xm, F e B1 Mn2 5 C alloy target with the thickness by RF sputtering 0.
- a magnetic force sample was prepared in the same manner as in Example 1 except that an irreversible recording material layer of 5 ⁇ was formed.
- Example 3-1 When the same measurement as in Example 3-1 was performed on this sample, the attenuation rate was 90% and the SN ratio was 1.9. This result indicates that a magnetic shield layer (irreversible recording layer) having a two-layer structure with excellent characteristics can be obtained even when the irreversible recording layer is formed by using the vacuum film forming method.
- the alloy powder obtained by the water atomization method was pulverized with a medium stirring mill to produce a flat alloy powder of Fe 5 » 2 which has an average particle size of 8 ⁇ m, and was used as an irreversible recording material.
- the alloy powder was crystalline immediately after quenching and after heating to 400 ° C.
- Co-coated ⁇ -Fe ”O powder (coercive force of about 7000e) was prepared.
- a magnetic paint containing the above irreversible recording material and the above hard magnetic material at a weight ratio of 1: 1 is applied to the surface of a polyimide substrate having a thickness of 188 m and dried to obtain an irreversible material having a thickness of 8 / xm.
- a recording layer was formed to obtain a magnetic recording medium sample.
- the irreversible recording layer 4 of the sample was heated by a thermal head to form a pattern in which heating regions of equal width were arranged at equal intervals.
- the irreversible recording layer 4 was cut by a cutter to form a removal area as shown in the figure.
- the width of each heating area was 1.25 mm (for 5 heating dots), and the width of the non-heating area between the heating areas was 0.75.
- the heating energy was 1.2 mJ / dot.
- Fig. 19 (b) shows the differential output when a forward bias magnetic field is applied
- Fig. 19 (c) shows the differential output when a reverse bias magnetic field is applied.
- the horizontal direction is time and one division is 2 ms
- the vertical direction is output and one division is 20 OmV. From these figures, it can be seen that the differentiated output caused by heating and the differentiated output caused by removal of the irreversible recording layer can be clearly distinguished both when the forward bias magnetic field is applied and when the reverse bias magnetic field is applied. By comparing these figures, it can be seen that data falsification due to irreversible recording layer removal can be found very easily.
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Description
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Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP98923131A EP0927951A4 (en) | 1997-06-04 | 1998-06-04 | MAGNETIC RECORDING MEDIUM AND METHOD OF USING THE SAME |
US09/244,437 US6029895A (en) | 1997-06-04 | 1999-02-04 | Magnetic recording medium and method of making the same |
Applications Claiming Priority (8)
Application Number | Priority Date | Filing Date | Title |
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JP9/161982 | 1997-06-04 | ||
JP9/161981 | 1997-06-04 | ||
JP9/161978 | 1997-06-04 | ||
JP16198197A JPH10340452A (ja) | 1997-06-04 | 1997-06-04 | 磁気記録媒体、その記録方法およびその製造方法 |
JP9/161979 | 1997-06-04 | ||
JP16197897A JPH10340448A (ja) | 1997-06-04 | 1997-06-04 | 磁気記録媒体 |
JP16198297A JPH10340416A (ja) | 1997-06-04 | 1997-06-04 | 磁気記録媒体およびその記録方法 |
JP16197997A JPH10340449A (ja) | 1997-06-04 | 1997-06-04 | 磁気記録媒体およびその記録再生方法 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1998055962A1 true WO1998055962A1 (fr) | 1998-12-10 |
Family
ID=27473766
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP1998/002485 WO1998055962A1 (fr) | 1997-06-04 | 1998-06-04 | Support d'enregistrement magnetique et son procede d'utilisation |
Country Status (4)
Country | Link |
---|---|
US (1) | US6029895A (ja) |
EP (1) | EP0927951A4 (ja) |
CN (1) | CN1228178A (ja) |
WO (1) | WO1998055962A1 (ja) |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0923046A4 (en) * | 1997-06-04 | 2001-04-18 | Tokyo Magnetic Printing | METHOD FOR USING A MAGNETIC RECORDING MEDIUM |
JPH11309967A (ja) * | 1998-04-27 | 1999-11-09 | Sony Corp | カード印刷装置 |
US6387530B1 (en) | 1999-08-27 | 2002-05-14 | Seagate Technology Llc | Patterned magnetic media via thermally induced phase transition |
US6612500B2 (en) * | 2000-06-12 | 2003-09-02 | Giesecke & Devrient America, Inc. | Separator card |
US6724674B2 (en) * | 2000-11-08 | 2004-04-20 | International Business Machines Corporation | Memory storage device with heating element |
WO2003089946A1 (en) | 2002-04-18 | 2003-10-30 | Seagate Technology Llc | Gmr spin valve structure using heusler alloy |
US8446684B2 (en) * | 2010-01-21 | 2013-05-21 | International Business Machines Corporation | Magnetic tape servo format allowing for increased linear tape density and systems thereof |
EP3681695A1 (en) | 2017-09-11 | 2020-07-22 | Raytheon Company | Magnetic encoding of physical objects in an additive manufacturing process |
US11635746B2 (en) | 2020-03-25 | 2023-04-25 | Raytheon Company | System and method for authenticating physical objects with randomized embedded information |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60209942A (ja) * | 1984-04-02 | 1985-10-22 | Canon Inc | 熱磁気記録媒体 |
JPS6228901A (ja) * | 1985-07-29 | 1987-02-06 | Omron Tateisi Electronics Co | 磁気記録再生方法 |
JPH06187636A (ja) * | 1992-10-22 | 1994-07-08 | Dainippon Printing Co Ltd | 磁気記録媒体及びその記録方法 |
JPH09128508A (ja) * | 1995-11-06 | 1997-05-16 | Tokyo Jiki Insatsu Kk | 磁気記録媒体および磁気記録再生方法 |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4188211A (en) * | 1977-02-18 | 1980-02-12 | Tdk Electronics Company, Limited | Thermally stable amorphous magnetic alloy |
US4239959A (en) * | 1977-03-23 | 1980-12-16 | General Kinetics Incorporated | Perpetuation of information in magnetically recorded medium |
FR2386080A1 (fr) * | 1977-03-31 | 1978-10-27 | Cii Honeywell Bull | Systeme de comptabilisation d'unites homogenes predeterminees |
US5471044A (en) * | 1993-02-08 | 1995-11-28 | Ricoh Company, Ltd. | Information recording card, and information recording and recognition methods using the card |
US5559247A (en) * | 1994-04-26 | 1996-09-24 | Mitsui Toatsu Chemicals, Inc. | Carboxylate and heat-sensitive recording material using same |
-
1998
- 1998-06-04 WO PCT/JP1998/002485 patent/WO1998055962A1/ja not_active Application Discontinuation
- 1998-06-04 CN CN98800757A patent/CN1228178A/zh active Pending
- 1998-06-04 EP EP98923131A patent/EP0927951A4/en not_active Withdrawn
-
1999
- 1999-02-04 US US09/244,437 patent/US6029895A/en not_active Expired - Fee Related
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60209942A (ja) * | 1984-04-02 | 1985-10-22 | Canon Inc | 熱磁気記録媒体 |
JPS6228901A (ja) * | 1985-07-29 | 1987-02-06 | Omron Tateisi Electronics Co | 磁気記録再生方法 |
JPH06187636A (ja) * | 1992-10-22 | 1994-07-08 | Dainippon Printing Co Ltd | 磁気記録媒体及びその記録方法 |
JPH09128508A (ja) * | 1995-11-06 | 1997-05-16 | Tokyo Jiki Insatsu Kk | 磁気記録媒体および磁気記録再生方法 |
Non-Patent Citations (1)
Title |
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See also references of EP0927951A4 * |
Also Published As
Publication number | Publication date |
---|---|
US6029895A (en) | 2000-02-29 |
CN1228178A (zh) | 1999-09-08 |
EP0927951A1 (en) | 1999-07-07 |
EP0927951A4 (en) | 2001-04-18 |
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