JP3022749B2 - Manufacturing method of magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a shopping card, a savings card,
Commuter pass, tickets, tickets, prepaid cards, cash cards, credit cards, identification, consultation ticket such as a magnetic card, a magnetic sheet, relates to a method of manufacturing a magnetic recording medium body to be used, such as a magnetic roll paper and, more particularly, it by also the determination information that can not be also formed in the coating step of the magnetic paint to erase, a process for producing a superior allowed the magnetic recording medium body anti-counterfeit added later.

[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 it can be repeatedly recorded and erased, 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 concealing recorded regular 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.

More specifically, the former known as a measure for preventing unauthorized use by making it difficult to record and reproduce magnetically recorded information, is to provide a multi-layered magnetic recording layer to provide legitimate information. 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. That is, if the dummy information is recorded while being superimposed on the regular information, it is difficult to analyze the regular information because the regular information and the dummy information are overlapped and read at the time of reading by a normal magnetic recording / reproducing apparatus. . 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, information that can be read and analyzed by anyone familiar with magnetic recording can be used. Was inadequate.

[0005] On the other hand, the latter magnetic recording medium is for applying authenticity determination information to a magnetic card itself. In this method, for example, a method is known in which a magnetic card is provided with a bar code that can be read magnetically, and the authenticity of the card is determined based on the bar code. In this method, since the medium itself has information for determining whether or not the magnetic recording medium is legitimate, it is possible to prevent a large amount of duplication. However, this method has a problem that it cannot cope with alterations such as rewriting magnetic information of a regular medium.

As another example of the latter magnetic recording medium, the present inventors have disclosed, for example, JP-A-63-9016.
As disclosed in Japanese Patent Application Laid-Open No. 63-9017, a method of forming a portion having a different orientation from the orientation of most of the magnetic recording medium by a method using a magnetic field, for example, JP-A-5-342567, JP-A-6-6
0372, JP-A-6-966443 and JP-A-6-9
As can be seen in, for example, Japanese Patent No. 6444, a method for producing a magnetic recording medium for forming an oriented portion different from most orientation directions or a non-oriented portion by a heat mode of a heat roll or a laser, A patent application has been filed for a magnetic recording medium having the obtained forgery prevention information.

[0007]

SUMMARY OF THE INVENTION These manufacturing methods are:
At the time of magnetic coating, forgery prevention information can be added at the same time, so the manufacturing process is simple.Forgery prevention information can be added only at the time of magnetic coating, so it can not be added or erased later, magnetic Since different forgery prevention information (fingerprint information) can be given to each of the final products of the recording medium, it has an excellent feature that it is inexpensive and has extremely high forgery prevention performance. However, in the above-described prior art, the problem that the interface between the forgery prevention information section and the normal orientation section cannot be clearly identified and the recording density of the forgery prevention information is 1 mm
There is a problem that it is difficult to form a fine pitch pattern as described below. The present invention has been made in view of the above circumstances, and can easily provide forgery prevention information that cannot be added or deleted, and can prevent unauthorized use due to duplication or falsification of magnetic information. and an object thereof is to provide a method for manufacturing a recording <br/> medium body.

[0008]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the conventional structure or method and provides a method of manufacturing a magnetic recording medium that is extremely difficult to use illegally.
The method of manufacturing a magnetic recording medium according to claim 1, wherein the high-coercivity magnetic powder having a coercive force of 250 to 5000 Oe and the low-coercivity magnetic powder having a coercive force of 100 Oe or less are formed on a base made of a nonmagnetic material. Applying a magnetic paint having a kind of magnetic powder to form an undried magnetic layer, and then applying a magnetic field to a part of the undried magnetic layer before the undried magnetic layer is dried, and then partially undried The magnetic layer is magnetized to form a magnetized portion composed of the high coercive force magnetic powder and the low coercive force magnetic powder, and the low coercive force magnetic powder is magnetized by the applied magnetic field and the magnetic field generated by the high coercive force magnetic powder. After being aggregated at a high density, the undried magnetic layer is dried and the magnetized portion is fixed so that a peak waveform output is obtained at the edge of the magnetized portion.

[0009] In the manufacturing method of the magnetic recording medium of claim 2, coating direction or coating the undried magnetic layer according to claim 1, wherein
Orientation of the magnetic field in a direction deviated from the direction
A magnetic field is applied to a part of the undried magnetic layer before the conductive layer is still dried.
Change the magnetization state of the undried magnetic layer
To form a magnetized portion .

[0010]

[0011]

[0012]

According to the present invention, as described above, two types of magnetic powder having a high coercive force of 250 to 5000 Oe and a low coercive force having a coercive force of 100 Oe or less are provided on a base made of a nonmagnetic material. Applying a magnetic paint containing magnetic powder, before the magnetic layer dries, partially magnetizes a part of the magnetic layer by applying a magnetic field to a part of the undried magnetic layer to form a magnetized part, Thereafter, the undried magnetic layer is dried and the magnetized portion is fixed so that a peak waveform output is obtained from the edge of the magnetized portion. That is, the magnetic layer is partially magnetized by applying a magnetic field from the outside before coating and before drying. At this time, the high coercivity magnetic powder having a coercive force of 250 to 5000 Oe and the low coercivity magnetic powder having a coercive force of 100 Oe or less are magnetized and oriented by an externally applied magnetic field to form a magnetized portion. This state of magnetization is maintained from before the magnetic layer is dried until after it is dried. Also low
The coercive force magnetic powder has a low coercive force magnetic powder in the magnetized part due to the magnetic field generated by the magnetization of the high coercive force magnetic powder having a coercive force of 250 to 5000 Oe in the magnetic paint, in addition to the magnetic field partially applied from the outside. It is set as a portion having a high density
You.

[0013]

As described above, due to the partial magnetization of the undried magnetic layer, the magnetic layer after drying has a partially different orientation state.
Furthermore, the state of high density of the low coercive force magnetic powder is physically fixed. This state is maintained even if the entire magnetic layer is demagnetized by direct current or alternating current.For example, by reproducing the track portion on which the pattern is formed while applying a direct current bias magnetic field, the track portion has a peak corresponding to the pattern. Signal can be obtained. Then, the peak interval, the number, the position, and the like of this signal are digitized, and this value is inserted into the information recorded in the normal magnetic recording section performed on the normally oriented track portion of the magnetic recording medium. If
When this magnetic recording medium is used, the authenticity of the medium can be determined by collating the value of the identification information detected and the value of the identification information mixed into the magnetic information, thereby eliminating counterfeiting of the medium. You can do it. This identification information is recorded before the undried magnetic layer is dried during the coating process of the magnetic paint, and thereafter is fixed by drying the undried magnetic layer. It is impossible information.

Further, a magnetic recording medium, for example, a magnetic card manufactured by the manufacturing method of the present invention can have different forgery prevention information on each card. That is, fingerprint information can be provided. As a result, each card has its own judgment information that cannot be added or erased later, and by using this judgment information, mass duplication and data falsification are almost perfect. Can be prevented.

Another method of manufacturing a magnetic recording medium according to the present invention is as follows.
A magnetic paint is applied on a non-magnetic base to form an undried magnetic layer, and then, while the magnetic layer is undried, the direction of travel of the base, that is, the magnetic recording direction (longitudinal direction) of the magnetic layer or the longitudinal direction Magnetic field orientation treatment in the direction deviated from the direction,
Then, while the magnetic layer is still wet, a magnetic field is applied by an electromagnet to disturb the orientation of a part of the wet magnetic layer,
Alternatively, a portion in a state close to this is formed, and a high density portion of the low coercivity magnetic material is formed in the magnetic layer by a magnetic field applied from the outside and a magnetic field due to the magnetization of the high coercivity magnetic powder. Thereafter, the non-dried magnetic layer is dried. The electromagnet used here may be a ring head-shaped electromagnet disposed on the back side of the base of the magnetic recording medium (the side on which the magnetic layer is not formed) so as not to come into direct contact with the undried magnetic layer. The electromagnets may be arranged so that the magnetic recording medium is sandwiched from both sides of the front side and the back side of the recording medium.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 shows an example of a manufacturing process of a magnetic recording medium according to the present invention. In this example, a high coercivity magnetic powder having a coercive force of 250 to 5000 Oe and a low coercivity magnetic powder having a coercive force of 100 Oe or less are applied to a base 2 made of a nonmagnetic material such as a white polyethylene terephthalate film sent from a reel 1. , And a magnetic paint obtained by adding a binder, a solvent and a trace amount of an additive thereto is applied by a coating head 3 of a coating machine to form an undried magnetic layer 4,
Next, the undried magnetic layer 4 is moved in the traveling direction of the base 2 by a magnetic field aligner 5 having a magnetic field generating ability of about 5K Oersted.
Is subjected to an orientation treatment. The magnetic field alignment device 5 is arranged at right angles to the direction of travel of the base 2 so that the magnetic layer 4 can be subjected to magnetic field orientation processing of the undried magnetic layer 4 in the direction of travel of the base 2. Other than, for example, 45
When the angle is changed to the degree, the magnetic field orientation processing can be performed in a direction having a 45 degree inclination with respect to the traveling direction of the base 2, that is, a direction deviated by 45 degrees from the application direction of the magnetic paint.

The nonmagnetic base 2 used here has a thickness of
A sheet-like non-magnetic material such as a polyester film, vinyl chloride film, synthetic paper, wood pulp paper, or laminated paper of about 150 μm to 1 mm can be used. Also, 250-
The magnetic material constituting the high coercivity magnetic powder having a coercive force of 5000 Oersted can be γ-iron oxide, cobalt-doped γ-iron oxide, chromium oxide, barium ferrite, strontium ferrite, or the like. The magnetic material constituting the low coercive force magnetic powder of coercivity is
Carbonyl iron, manganese zinc ferrite, nickel,
Iron trioxide, permalloy, sendust, alpalm and the like can be applied.

The compounding ratio of the magnetic powders having different coercive forces, that is, the value of (high coercive force magnetic powder having a coercive force of 250 to 5000 Oersted) :( low coercive force magnetic powder having a coercive force of 100 Oersted or less) , 50:50 to 95: 5, particularly preferably 80:20 to 90:10. If the mixing ratio is less than 50:50, the ratio of the high coercivity magnetic powder is too small, and the performance of the magnetic recording medium itself is reduced. If the mixing ratio is larger than 95: 5, the ratio of the low coercivity magnetic powder is low. It becomes too small to read the forgery prevention information. The binder is vinyl chloride
Known materials such as a vinyl acetate copolymer, a vinyl chloride / vinyl acetate / vinyl alcohol copolymer, a polyurethane resin, a polyester resin, an epoxy resin, and a polyisocyanate resin can be used, and a known solvent such as toluene or methyl ethyl ketone can be used. Can be used as appropriate.

Next, before the coating of the undried magnetic layer 4 made of a magnetic paint is dried, a rectangular wave-shaped current is intermittently applied to the ring-shaped electromagnets 6 as shown in FIG. A magnetic field is partially applied to the undried magnetic layer 4 by applying a magnetic field from the back side of the base 2 to form a pattern-like magnetized portion 9. Subsequent undried magnetic layer 4 is passed through the drying device 7 is dried and solidified is a magnetic layer 10, magnetic
The air fabric 11 is obtained and wound by the winding device 8. If the current applied to each of the electromagnets 6 is too small, the magnetic field generated by the electromagnets 6 is too weak to disturb the orientation sufficiently. On the other hand, if the current is too large, the generated magnetic field is too strong, and the undried undried magnetic layer 4 will have large irregularities. Further, if the gap G of the ring-shaped electromagnet 6 is too small, the reach of the generated magnetic field becomes short, and a sufficient magnetic field cannot be applied from the back side of the nonmagnetic film 2. Current must be passed, and the device becomes large-scale.
The electromagnets 6 for forming the forgery prevention information may be arranged in the width direction by the required number of tracks as shown in FIG.

The rectangular-wave current flowing through the electromagnet 6 may be a random pattern or may be based on some rule. The same pattern of current may flow in each track, or a completely different pattern of current may flow. Also, as shown in FIG. 2, when a current having a completely different pattern is applied to each track, a magnetic recording medium, for example, a magnetic card obtained from the magnetic material 11 manufactured in this manner can be used for all magnetic cards. You will have different anti-counterfeit information. That is, it has fingerprint information. The fact that no other magnetic card has the same information makes it more difficult to forge the magnetic card. In this case, it is preferable that the portions where the orientation is disturbed are arranged on a certain track when punched into a magnetic card shape.

FIG. 3 shows an example of how to apply a magnetic field when forming the magnetized portions 9 in a pattern in the above-described manufacturing method. In this example, the whole of the undried magnetic layer 4 is simultaneously and uniformly magnetized in one direction by the magnetic field alignment device 5. It is magnetized in the opposite direction. FIG.
An example of the planar arrangement of the magnetized portions 9 magnetized in the opposite directions as described above is shown below. In this example, since the magnetic paint in which the low-coercivity magnetic powder and the high-coercivity magnetic powder are mixed is used, the magnetized portion 9 is mainly formed of the high-coercivity magnetic powder, and the magnetized portion 9 is surrounded by the low-coercivity magnetic powder as indicated by hatching. There is formed a portion 9 ′ in which the coercive force magnetic powder is gathered and configured as a high-concentration portion.

FIG. 5 shows an example of an arrangement structure of a magnetic head for performing partial magnetization in a direction opposite to the magnetization direction oriented by the magnetic field orientation device 5. As shown in FIG. 5A, a ring head type magnetic head 6 may be installed on the side opposite to the coating surface to apply a magnetic field to the undried magnetic layer 4, or as shown in FIG. 5B. Ring head type magnetic head 6, 6 '
May be installed on both sides of the non-magnetic tape 2 so as to sandwich the application surface from above and below. Also, as shown in FIG. 5 (c), bar-shaped electromagnets 6 ″ and 6 ″ are applied so as to give opposing magnetic fields of the same polarity.
May be arranged.

FIG. 6 shows a card-shaped magnetic recording medium punched out from a magnetic raw material including a magnetized portion 9 which is magnetized in a direction opposite to the magnetization by the orientation of the magnetic field orienting device 5 as described above. Using a magnetic recording / reproducing apparatus equipped with a recording / reproducing magnetic head while applying a DC bias current to a track on which the magnetized portions 9 are arranged, reproduction is performed, and the result is displayed on a synchroscope. It is shown. As shown in FIG. 6, a pulse-like output can be detected at the edge of the magnetized portion 9. Such output waveforms are information that cannot be added or erased after the card is manufactured. If the number of outputs, intervals, etc. are quantified and used as card ID information, the authenticity of the card can be determined. It is possible to do. Moreover, since this waveform is a peak waveform, detection is easy and magnetic information due to the presence of the magnetized portions 9 can be detected with high sensitivity.

FIG. 7 shows a cross-sectional structure of a magnetic depletion obtained by the method shown in FIG. 3 and FIG. In the magnetic layer 10 shown in FIG.
Are formed in a large number. This is a portion in which the concentration of the low coercive force magnetic powder is increased is formed in a convex shape, and corresponds to the portion 9 'in FIG.

FIG. 8 shows an example of a sectional structure of a magnetic card to which the structure shown in FIG. 7 is applied. In the structure of this example, a magnetic layer 10 is formed on a base 2 with an under layer 15 interposed therebetween, and a magnetic shielding layer 16 known as a silver coloring layer or a white layer is formed on the magnetic layer 10. A thermosensitive recording layer 17 of a leuco dye type or the like and a protective layer 18 are laminated.
The structure of this example corresponds to the structure of the magnetic card actually used, and the surface or the lower surface of the protective layer 18 is appropriately printed according to the purpose of use. The under layer 15 is used to prevent the magnetic paint from penetrating the base 2 when the base 2 is made of a material such as paper. In the present invention, a structure in which the heat-sensitive recording layer 17 is provided on the back surface side of the base 2, a structure in which only the protective layer 18 is provided on the magnetic layer 10, and only the concealing layer 16 and the protective layer 18 on the magnetic layer 10 are provided. Needless to say, the structure may be provided.

In the manufacturing method described above with reference to FIGS. 1 to 5, the wet magnetic layer 4 is
Are magnetized once in the longitudinal direction, and then the electromagnet 6 ...
The magnetized portions 9 are formed by the electromagnets 6 in a state where the magnetic field aligning device 5 is omitted and the whole of the undried magnetic layer 4 is not particularly subjected to the magnetic field orientation treatment. May be created. Even in the magnetic card obtained by preparing in this way, the output waveform of the peak-shaped <br/> shown in FIG. 6 is obtained.

[0028]

【Example】

 (Example 1) A magnetic paint having the following composition was prepared. Magnetic powder Barium ferrite Coercive force 2750 Oe 80 parts by weight Carbonyl iron powder Coercive force 10 Oe 20 parts by weight Carbon black 3 parts by weight Lecithin 1 part by weight Vinyl chloride / vinyl acetate / vinyl alcohol copolymer (Essrec A, manufactured by Sekisui Chemical Co., Ltd.) 20 20 parts by weight Polyurethane resin (Nipporan N-2304, manufactured by Nippon Polyurethane Industry) 5 parts by weight Polyisocyanate resin (Coronate L, manufactured by Nihon Polyurethane Industry) 5 parts by weight Toluene 60 parts by weight Methyl ethyl ketone 60 parts by weight Methyl isobutyl ketone 60 parts by weight

The magnetic paint having this composition was applied to a 188 μm-thick polyester film by the method shown in FIG. 1, and then a magnetic field was applied partially using a ring-shaped electromagnet. The configuration of the ring-shaped electromagnet and its driving conditions are described below.

A card is punched out of the magnetic raw material obtained in this manner, and a DC bias magnetic field is applied to a track including a portion to which a magnetic field is applied in a pattern by a recording / reproducing apparatus for a magnetic card using a recording / reproducing head. As a result, a pulse-like reproduction output could be detected at the position of the forgery prevention information section. This pulse-shaped output has a sufficient output level as forgery prevention information, and it was possible to prevent forgery of the card by using this information.

Example 2 Instead of the magnetic powder used in Example 1, a magnetic powder having a composition of magnetic powder barium ferrite coercive force 1750 Oe 80 parts by weight carbonyl iron powder coercive force 10 Oe 20 parts by weight was used. Other than that, the composition was the same as that of Example 1, the card was punched out from the magnetic raw material obtained under the same conditions as in Example 1, and the reproduction output was measured by the same measuring means. The same result was obtained.

(Example 3) In place of the magnetic powder used in Example 1, a magnetic powder having a composition of barium ferrite coercive force 1750 Oe 80 parts by weight magnetite powder coercive force 25 Oe 20 parts by weight was used. Is the same composition as in Example 1, the card was punched out from the magnetic raw material obtained under the same conditions as in Example 1, and the reproduction output was measured by the same measuring means. The same result could be obtained.

[0033]

As described above, the magnetic recording medium according to the manufacturing method of the first aspect of the present invention has a magnetized portion formed by drying and solidifying a magnetic paint comprising a high coercive force magnetic component and a low coercive force magnetic powder. Since the high-density portion of the low coercive force magnetic powder and the portion obtained by drying and solidifying the magnetic paint are all physically fixed, they cannot be erased or changed after drying. Since a peak waveform can be obtained from the edge of the portion, the output waveform from the edge becomes the forgery prevention information of the magnetic recording medium. Further, the magnetized portion is composed of two types of magnetic powder, a low coercive force magnetic powder and a high coercive force magnetic powder, which are present in the magnetized portion, and a high-density low coercive force magnetic powder, which is present at an edge around the magnetized portion. Since a unique magnetic output including the obtained peak waveform is generated, magnetic information due to the presence of the magnetized portion can be detected with high sensitivity.
Therefore, according to the first aspect of the invention, it is possible to manufacture a magnetic recording medium that cannot be forged or altered.

Furthermore, according to the manufacturing method of the second aspect,
The undried magnetic layer consisting of the magnetic paint applied on the base
Field to form a magnetization orientation part, and then
Applying a magnetic field to a part of the magnetized orientation part to make it a magnetized part
A magnetic recording medium capable of obtaining a peak waveform output.
Can be manufactured.

[0035]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of an apparatus for performing a manufacturing method according to the present invention.

FIG. 2 is an enlarged perspective view showing an arrangement relationship between a magnetic field orientation device and a magnetic head provided in the device shown in FIG.

FIG. 3 is an explanatory view showing a state in which a part of the undried magnetic layer oriented by the magnetic field orientation device shown in FIG. 2 is oriented in the opposite direction by a magnetic head to form a magnetized portion.

4 (a) is a plan view showing an arrangement state of a magnetic part partially formed on an undried magnetic layer by the magnetic head shown in FIG. 3, and FIG. 4 (b) shows the same magnetic arrangement state It is an enlarged view.

FIG. 5 shows an arrangement of a magnetic head for applying a magnetic field to an undried magnetic layer on a non-magnetic substrate. FIG. 5 (a) shows an example in which a magnetic head is disposed on the back side of the non-magnetic substrate. FIG. 5B is an explanatory view showing an example in which a magnetic head is arranged above and below a non-magnetic substrate, and FIG. 5C is a diagram showing bar-shaped magnets arranged above and below a non-magnetic substrate. It is explanatory drawing which shows an example.

FIG. 6 is a diagram showing an output waveform obtained from one structural example of a magnetic recording medium obtained according to the present invention.

FIG. 7 is a sectional view showing an example of a magnetic card obtained by the manufacturing method of the present invention.

FIG. 8 is a sectional view showing another example of the magnetic card obtained by the manufacturing method of the present invention.

[Explanation of symbols]

 2 Base, 4 Undried magnetic layer, 5 Magnetic field alignment device, 6, 6 ', 6' 'magnetic head, 7 Drying device, 10 Magnetic layer, 11 Magnetic source,

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Izumiichi Yoshizawa 3-1 Yosoba-cho, Shizuoka-shi, Shizuoka Pref. Hamakawa Paper Mills Information Media Division (56) References JP-A-63-9016 (JP) JP-A-6-20264 (JP, A) JP-A-3-256799 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/80, 5/706, 5/845

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein the base is made of a non-magnetic material.
High coercivity magnetic powder with coercivity of ~ 5000 Oersted and 1
A magnetic paint having two magnetic powders of a low coercive force magnetic powder having a coercive force of not more than 00 Oersted is applied to form an undried magnetic layer, and then the undried magnetic layer is formed before the undried magnetic layer is dried. By applying a magnetic field to a part of the magnetic layer, the undried magnetic layer is partially magnetized to form a magnetized portion composed of a high coercive force magnetic powder and a low coercive force magnetic powder, and the applied magnetic field and the high coercive force magnetic powder of the magnetized portion are formed. After assembling the magnetic powder with a low coercive force at a high density by the magnetic field generated by the magnetic field, drying the undried magnetic layer and fixing the magnetized portion so that the peak waveform output is obtained at the edge of the magnetized portion A method for manufacturing a magnetic recording medium, comprising: 2. A magnetic field orientation of the undried magnetic layer in a coating direction or a direction deviated from the coating direction, and then applying a magnetic field to a part of the undried magnetic layer before the undried magnetic layer is still dried. 2. The method according to claim 1, wherein the magnetized portion is formed by partially changing the magnetization state of the undried magnetic layer.