JPH1139604A - Magnetic recording medium and its production and use method - Google Patents
Magnetic recording medium and its production and use methodInfo
- Publication number
- JPH1139604A JPH1139604A JP20740097A JP20740097A JPH1139604A JP H1139604 A JPH1139604 A JP H1139604A JP 20740097 A JP20740097 A JP 20740097A JP 20740097 A JP20740097 A JP 20740097A JP H1139604 A JPH1139604 A JP H1139604A
- Authority
- JP
- Japan
- Prior art keywords
- magnetic
- magnetic layer
- magnetic field
- recording medium
- layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Digital Magnetic Recording (AREA)
- Recording Or Reproducing By Magnetic Means (AREA)
- Manufacturing Of Magnetic Record Carriers (AREA)
- Magnetic Record Carriers (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明はプリペイドカードに
使用するのに適した磁気カードに関するものであり、特
に磁気信号の改ざん、偽造による不正使用を困難にした
磁気カードに関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic card suitable for use in a prepaid card, and more particularly to a magnetic card which makes it difficult to tamper with a magnetic signal or to illegally use it by forgery.
【０００２】[0002]
【従来技術】最近の磁気カードにおいてはプリペイドカ
ードと呼ばれる前払い方式の磁気カードが広く普及して
きた。しかしこのプリペイドカードは市場において金券
同様に扱われるため、磁気信号の改ざん偽造による不正
使用を防止しなければならず、これまでに種々の考案が
なされている。そのうち、安全性の高い方法として、磁
気カードに真偽判定情報として固定パターンを利用する
ものがある。例えば実開昭５８−６５６４４号公報に開
示されたような磁性インキによる固定パターンを形成す
る方法がある。また、特開平６−２０３３６６号公報、
特開平７−２１０８５９号公報に開示されたような磁気
記録可能な第１の磁性層に磁気記録し、この上に第１の
磁性層に磁気記録した磁気パターンに対応した書換不能
な固定パターンを第２の磁性層に形成する方法がある。2. Description of the Related Art In recent magnetic cards, prepaid magnetic cards called prepaid cards have become widespread. However, since the prepaid card is treated like a cash voucher in the market, it is necessary to prevent unauthorized use due to falsification and forgery of a magnetic signal, and various ideas have been made so far. Among them, there is a method of using a fixed pattern as authenticity determination information in a magnetic card as a method with high security. For example, there is a method of forming a fixed pattern using magnetic ink as disclosed in Japanese Utility Model Laid-Open No. 58-65644. Also, JP-A-6-203366,
Japanese Patent Application Laid-Open No. 7-210859 discloses a magnetic recording on a magnetically recordable first magnetic layer, and a non-rewritable fixed pattern corresponding to the magnetic pattern magnetically recorded on the first magnetic layer. There is a method of forming the second magnetic layer.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら従来のこ
れらの方法は磁気信号の改ざん、偽造による不正使用を
防止するのに必ずしも十分とはいえない。例えば実開昭
５８−６５６４４号公報に開示されたような方法では、
磁性インキによる固定パターンをスクリーン印刷等の方
法で形成されるため、固定パターンの種類の数だけシル
ク版を準備する必要があり、一般に同一の固定パターン
をもつ大量の磁気カードが製造されてしまうという欠点
をもち、偽造されるおそれがある。これに対し特開平６
−２０３３６６号公報、特開平７−２１０８５９号公報
に開示されたような方法では、磁気記録可能な第１の磁
性層に磁気記録した磁気パターンに対応した固定パター
ンが第２の磁性層に形成されるため、個々の磁気カード
で異なった真偽判定情報を固定パターンとして形成でき
る利点がある。However, these conventional methods are not always sufficient to prevent tampering of the magnetic signal and unauthorized use by forgery. For example, in the method disclosed in Japanese Utility Model Application Laid-Open No. 58-65644,
Since the fixed pattern using magnetic ink is formed by a method such as screen printing, it is necessary to prepare silk plates for the number of types of the fixed pattern, and in general, a large number of magnetic cards having the same fixed pattern are manufactured. It has drawbacks and can be forged. On the other hand,
In the method disclosed in JP-A-203366 and JP-A-7-210859, a fixed pattern corresponding to the magnetic pattern magnetically recorded on the magnetically recordable first magnetic layer is formed on the second magnetic layer. Therefore, there is an advantage that different authenticity determination information can be formed as a fixed pattern in each magnetic card.
【０００４】しかし特開平６−２０３３６６号公報に開
示されたような方法では、固定パターンは第１の磁性層
に磁気記録した磁気パターンの磁束反転部に磁性粒子が
集まって形成されるため、磁気パターンの１回の磁束反
転に対し固定パターンは２回の磁束反転を有し、この２
回の磁束反転による信号波長は第１の磁性層に磁気記録
した記録波長に関係なく一定である。このため記録密度
がある程度高くなると単一波長の固定信号に近づき、Ｆ
２Ｆ方式のような周波数変調方式には対応できなくなる
という欠点をもつ。また特開平７−２１０８５９号公報
に開示されたような方法では、第２の磁性層を形成する
ときの配向処理により第一の磁性層に磁気記録した磁気
パターンと等しい信号波長の固定パターンを形成でき
る。しかし固定パターンの形成は磁性粒子の粗密により
形成されるものであり、従来技術に共通の欠点として、
印刷等で形成した固定パターンと同様の手段で読み取り
可能であること、また固定パターンは凹凸として形成さ
れるため読み取り信号と同様のパターンが目視可能であ
るという欠点をもつ。本発明者らはこのような問題点に
照らし、固定信号の読取方法による真偽判定性および視
認性を改善したさらに安全性の高い磁気記録媒体を提供
しようとするものである。However, according to the method disclosed in Japanese Patent Application Laid-Open No. 6-203366, the fixed pattern is formed by gathering magnetic particles in a magnetic flux reversal portion of the magnetic pattern magnetically recorded on the first magnetic layer. The fixed pattern has two flux reversals for one flux reversal of the pattern.
The signal wavelength resulting from the first magnetic flux reversal is constant irrespective of the recording wavelength magnetically recorded on the first magnetic layer. Therefore, when the recording density is increased to some extent, the signal approaches a fixed signal of a single wavelength, and F
It has a drawback that it cannot support a frequency modulation system such as the 2F system. In the method disclosed in Japanese Patent Application Laid-Open No. 7-210859, a fixed pattern having the same signal wavelength as the magnetic pattern magnetically recorded on the first magnetic layer is formed by the orientation treatment when forming the second magnetic layer. it can. However, the formation of the fixed pattern is formed by the density of the magnetic particles.
It has the drawback that it can be read by the same means as a fixed pattern formed by printing or the like, and that the fixed pattern is formed as unevenness, so that the same pattern as the read signal can be viewed. The present inventors have sought to provide a more secure magnetic recording medium with improved authenticity determination and visibility by a fixed signal reading method in view of such problems.
【０００５】[0005]
【課題を解決するための手段】本発明の磁気記録媒体
は、非磁性基体上に少なくとも１つの磁気記録可能な第
１の磁性層を形成し、さらに、少なくとも２つの保磁力
の異なる第２、第３の磁性層を積層して成る磁気記録媒
体であり、前記第２、第３の磁性層は前記第１の磁性層
に記録された信号による磁界並びに配向磁界の影響によ
り、磁気記録媒体の面内の同一線上に各々反転したパタ
ーンとして書換不能な固定信号が形成されている。各々
反転した固定パターンとは、前記第２、第３の磁性層に
形成された固定パターンが磁性粒子の粗密による凹凸と
して形成され、第２の磁性層の凸部には第３の磁性層の
凹部が、また第２の磁性層の凹部には第３の磁性層の凸
部がそれぞれ等しい信号ピッチで積層されていることで
ある（図１）。According to the magnetic recording medium of the present invention, at least one magnetically recordable first magnetic layer is formed on a non-magnetic substrate, and at least two second magnetic layers having different coercive forces are formed. A magnetic recording medium having a third magnetic layer laminated thereon, wherein the second and third magnetic layers are formed by a magnetic field due to a signal recorded on the first magnetic layer and an orientation magnetic field, and Non-rewritable fixed signals are formed as inverted patterns on the same line in the plane. Each of the fixed patterns that are inverted means that the fixed patterns formed on the second and third magnetic layers are formed as irregularities due to the density of the magnetic particles, and the convex portions of the second magnetic layer have the convex portions of the third magnetic layer. The concave portion is formed on the concave portion of the second magnetic layer, and the convex portion of the third magnetic layer is laminated on the concave portion of the second magnetic layer at the same signal pitch (FIG. 1).
【０００６】本発明の磁気記録媒体は次のように製造さ
れる。先ず非磁性基体上に磁気記録可能な磁性材料から
成る第１の磁性層を形成し、次いで前記第１の磁性層に
所定の信号を磁気記録し、その後第２の磁性層を形成す
る磁性塗料を塗布、乾燥、固化する。更に次いで前記第
２の磁性層と保持力の異なる磁性塗料を塗布、乾燥、固
化し、第３の磁性層を形成する。前記第２の磁性層を形
成するとき、前記磁性塗料が乾燥、固化する前に前記第
１磁性層の保磁力以下の磁界強度で、塗布方向に対し平
行な直流磁界を使用して直流配向処理をすることによ
り、前記第２の磁性層に前記第１の磁性層に磁気記録し
た信号と同じ固定信号を形成できる。前記第３の磁性層
を形成するとき、前記第２の磁性層を形成した直流配向
処理と逆極性の直流配向処理を行うことにより、前記第
１の磁性層に磁気記録した信号と逆パターン、つまり前
記第２の磁性層と反転したパターンの固定信号を形成で
きる。[0006] The magnetic recording medium of the present invention is manufactured as follows. First, a first magnetic layer made of a magnetic material that can be magnetically recorded is formed on a non-magnetic substrate, then a predetermined signal is magnetically recorded on the first magnetic layer, and then a second magnetic layer is formed. Is applied, dried and solidified. Next, a magnetic paint having a different coercive force from the second magnetic layer is applied, dried, and solidified to form a third magnetic layer. When the second magnetic layer is formed, before the magnetic paint is dried and solidified, a DC orientation treatment is performed using a DC magnetic field parallel to the coating direction with a magnetic field strength equal to or less than the coercive force of the first magnetic layer. Thus, the same fixed signal as the signal magnetically recorded on the first magnetic layer can be formed on the second magnetic layer. When forming the third magnetic layer, by performing a DC alignment process of a polarity opposite to that of the DC alignment process of forming the second magnetic layer, a pattern reverse to a signal magnetically recorded on the first magnetic layer, That is, it is possible to form a fixed signal having a pattern inverted from that of the second magnetic layer.
【０００７】前記磁気記録媒体の使用方法としては、先
ず磁気ヘッドで所定の極性のバイアス磁界を印加しなが
ら、または印加後に前記磁気記録媒体を読み取ったとき
の出力レベルと所定の極性と逆極性のバイアス磁界を印
加しながら、または印加後に前記磁気記録媒体を読み取
ったときの出力レベルとを比較し、その出力レベルの差
を認識することができる。例えば第２の磁性層の保磁力
が第３の磁性層の保磁力より大きく、所定のバイアス磁
界が第２の磁性層を磁化できず、第３の磁性層を十分に
磁化できる関係にあるとき、まず磁気記録媒体の固定パ
ターン上を第１、第２、第３の磁性層が十分に磁化でき
る直流磁界をかけながら磁気ヘッドを走査し、次にこれ
と同じ極性の所定のバイアス磁界を流しながら再生出力
を読み取る。このとき第２の磁性層と第３の磁性層の固
定パターンは同一方向に磁化されているため再生出力は
ほとんど得られない（図３）。As a method of using the magnetic recording medium, first, while applying a bias magnetic field of a predetermined polarity with a magnetic head, or after applying the bias magnetic field, the output level when the magnetic recording medium is read and a polarity opposite to the predetermined polarity are read. By comparing the output level when reading the magnetic recording medium with or after applying the bias magnetic field, the difference between the output levels can be recognized. For example, when the coercive force of the second magnetic layer is larger than the coercive force of the third magnetic layer, a predetermined bias magnetic field cannot magnetize the second magnetic layer, and the third magnetic layer is sufficiently magnetized. First, the magnetic head is scanned while applying a DC magnetic field capable of sufficiently magnetizing the first, second, and third magnetic layers on the fixed pattern of the magnetic recording medium, and then a predetermined bias magnetic field having the same polarity as this is applied. While reading the playback output. At this time, since the fixed patterns of the second magnetic layer and the third magnetic layer are magnetized in the same direction, almost no reproduction output is obtained (FIG. 3).
【０００８】次に前記の極性と逆極性の所定のバイアス
磁界を流しながら再生出力を読み取る。このとき第２の
磁性層と第３の磁性層の固定パターンは逆方向に磁化さ
れているため磁化反転が生じ十分な再生出力が得られる
（図２）。Next, the reproduced output is read while a predetermined bias magnetic field having a polarity opposite to the above-mentioned polarity is passed. At this time, since the fixed patterns of the second magnetic layer and the third magnetic layer are magnetized in opposite directions, magnetization reversal occurs and a sufficient reproduction output is obtained (FIG. 2).
【０００９】本発明の効果としては、まず第２の磁性層
と第３の磁性層に形成された２つの固定パターンで１つ
の固定信号を形成しているため非常に偽造しにくく、バ
イアス磁界の極性を変えることにより２つの固定パター
ンの磁化方向を同一方向と逆方向に変化させられる。こ
のとき再生出力の差は従来にない本発明の磁気記録媒体
に特有のバイアス依存性である。さらに第２の磁性層と
第３の磁性層の固定パターンは磁気記録媒体の面内の同
一線上に各々反転したパターンとして形成されているた
め、第２の磁性層と第３の磁性層の固定パターンの凹と
凸または凸と凹が重なり合う。このため外観上の固定パ
ターンは平坦なものとなり、視認性が悪く、目視での確
認が困難である。よって本発明の磁気記録媒体は極めて
偽造、変造しにくく、不正使用防止効果が高い。As an effect of the present invention, first, since one fixed signal is formed by the two fixed patterns formed on the second magnetic layer and the third magnetic layer, it is extremely difficult to forge, and the bias magnetic field is reduced. By changing the polarity, the magnetization directions of the two fixed patterns can be changed in the same direction and opposite directions. At this time, the difference between the reproduction outputs is a bias dependency peculiar to the magnetic recording medium of the present invention, which has not existed conventionally. Further, since the fixed pattern of the second magnetic layer and the third magnetic layer is formed as inverted patterns on the same line in the plane of the magnetic recording medium, the fixed pattern of the second magnetic layer and the third magnetic layer is fixed. Concave and convex or convex and concave of the pattern overlap. For this reason, the fixed pattern on the external appearance is flat, the visibility is poor, and it is difficult to confirm it visually. Therefore, the magnetic recording medium of the present invention is extremely difficult to forge or falsify, and has a high effect of preventing unauthorized use.
【００１０】[0010]
【発明の実施の形態】次に本発明の磁気記録媒体を実施
例により説明する。図１は本発明の一実施例としての磁
気記録媒体の断面図である。この実施例においては、非
磁性基体１上に第１の磁性層２を形成し、第１の磁性層
２上に第２の磁性層３が固定信号として形成してある。
さらに第２の磁性層３上に第３の磁性層４が第２の磁性
層３の固定信号と逆パターンの固定信号として形成し、
第２の磁性層３と第３の磁性層４の固定信号は磁気記録
媒体の面内の同一線上に各々反転したパターンとして形
成してある。非磁性基体１にはプラスチック、紙、また
は非磁性金属板であっても良いが、特にプラスチックを
用いる場合にはポリエチレンテレフタレートが好まし
い。第１の磁性層２はγ−Ｆｅ2 Ｏ3 、Ｃｏ被着γ−Ｆ
ｅ2 Ｏ3 、Ｂａフェライトなどの磁性粉と適当な結合
剤、添加剤よりなる通常用いられる磁気記録層であって
良い。第２の磁性層３は第１の磁性層２と同様の通常の
磁気記録層であって良く、またはカルボニル鉄粉、Ｆｅ
−Ａｌ合金、Ｆｅ−Ｎｉ合金、Ｆｅ−Ａｌ−Ｓｉ合金、
Ｍｎ−Ｚｎフェライト、Ｎｉ−Ｚｎフェライトなどの軟
磁性粉と適当な結合剤、添加剤よりなる磁性層であって
良い。第３の磁性層４は第２の磁性層３と同様であって
良い。ただし、第２の磁性層３とは保磁力が異なること
が好ましい。Next, the magnetic recording medium of the present invention will be described with reference to examples. FIG. 1 is a sectional view of a magnetic recording medium according to one embodiment of the present invention. In this embodiment, a first magnetic layer 2 is formed on a non-magnetic substrate 1, and a second magnetic layer 3 is formed on the first magnetic layer 2 as a fixed signal.
Further, a third magnetic layer 4 is formed on the second magnetic layer 3 as a fixed signal having a pattern opposite to the fixed signal of the second magnetic layer 3, and
The fixed signals of the second magnetic layer 3 and the third magnetic layer 4 are formed as inverted patterns on the same line in the plane of the magnetic recording medium. The non-magnetic substrate 1 may be plastic, paper, or a non-magnetic metal plate, but when plastic is used, polyethylene terephthalate is preferred. The first magnetic layer 2 is made of γ-Fe 2 O 3 ,
It may be a commonly used magnetic recording layer comprising magnetic powder such as e 2 O 3 , Ba ferrite and suitable binders and additives. The second magnetic layer 3 may be a normal magnetic recording layer similar to the first magnetic layer 2, or may be carbonyl iron powder, Fe
-Al alloy, Fe-Ni alloy, Fe-Al-Si alloy,
The magnetic layer may be composed of a soft magnetic powder such as Mn-Zn ferrite or Ni-Zn ferrite and a suitable binder and additive. The third magnetic layer 4 may be similar to the second magnetic layer 3. However, it is preferable that the coercive force differs from that of the second magnetic layer 3.
【００１１】[0011]
【実施例】図１の実施例により具体的に説明する。 （実施例１）まず、厚さ１８８μｍの白色ポリエチレン
テレフタレートの非磁性基体１上に保磁力２７５０ Ｏ
ｅのＢａフェライト粉と樹脂、分散剤、硬化剤、その他
添加剤とを溶剤中で均一に混合した磁性塗料をグラビア
塗布し、厚さ５μｍの第１の磁性層２を形成した。次に
第１の磁性層２の所定の領域に１５０ ＢＰＩのＦＭ信
号を飽和記録した。第１の磁性層２上に保磁力が９５０
ＯｅのＢａフェライトと樹脂、分散剤、硬化剤、その
他添加剤とを溶剤中で均一に混合した磁性塗料をナイフ
塗布し、厚さ５μｍの第２の磁性層３を形成した。この
とき磁性塗料が乾燥固化する前にソレノイドコイル配向
装置を用い磁界強度１２００ Ｏｅの直流配向処理を行
い、第１の磁性層２の所定の領域に記録した１５０ Ｂ
ＰＩのＦＭ信号に等しい固定信号を形成した。第２の磁
性層３上に保磁力が２０ Ｏｅのカルボニル鉄粉と樹
脂、分散剤、硬化剤、その他添加剤とを溶剤中で均一に
混合した磁性塗料をナイフ塗布し、厚さ３μｍの第３の
磁性層４を形成した。このとき磁性塗料が乾燥固化する
まえにソレノイドコイル配向装置を用い磁界強度６００
Ｏｅで、第２の磁性層３を形成したときと逆極性の直
流配向処理を行い、第１の磁性層２の所定の領域に記録
した１５０ ＢＰＩのＦＭ信号と反転した、逆パターン
の固定信号を形成した。これをカードサイズに打ち抜い
た。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment will be described more specifically with reference to FIG. Example 1 First, a coercive force of 2750 O was applied on a non-magnetic substrate 1 of white polyethylene terephthalate having a thickness of 188 μm.
The magnetic paint obtained by uniformly mixing the Ba ferrite powder of (e) with a resin, a dispersant, a curing agent, and other additives in a solvent was gravure coated to form a first magnetic layer 2 having a thickness of 5 μm. Next, an FM signal of 150 BPI was saturatedly recorded in a predetermined area of the first magnetic layer 2. A coercive force of 950 on the first magnetic layer 2
A magnetic paint in which Oe Ba ferrite and a resin, a dispersant, a curing agent, and other additives were uniformly mixed in a solvent was knife-coated to form a second magnetic layer 3 having a thickness of 5 μm. At this time, before the magnetic paint is dried and solidified, a direct current orientation treatment of a magnetic field strength of 1200 Oe was performed using a solenoid coil orientation device, and 150 B recorded in a predetermined area of the first magnetic layer 2 was recorded.
A fixed signal equal to the FM signal of PI was formed. A magnetic paint in which carbonyl iron powder having a coercive force of 20 Oe and a resin, a dispersant, a hardener, and other additives are uniformly mixed in a solvent is knife-coated on the second magnetic layer 3 to form a 3 μm-thick magnetic paint. The third magnetic layer 4 was formed. At this time, before the magnetic paint is dried and solidified, a magnetic field strength of 600
In Oe, a DC alignment process of a polarity opposite to that when the second magnetic layer 3 was formed was performed, and a fixed signal of an inverted pattern inverted from the 150 BPI FM signal recorded in a predetermined area of the first magnetic layer 2 Was formed. This was punched into a card size.
【００１２】次に実施例１の本発明をその使用方法によ
り詳細に説明する。まず第１の磁性層２に飽和記録でき
るライトヘッドを装着したリーダーライターで第１の磁
性層２に記録された信号を直流消去した。次に同じリー
ダーライターに装着されたバイアスコイル付きリードヘ
ッドで第２の磁性層３の飽和磁界以下、第３の磁性層４
の飽和磁界以上の磁界が発生する２０ｍＡのバイアス電
流を所定の極性で流しながら再生出力を読み取ったとこ
ろ、図２に示すように十分な出力レベルが得られた。さ
らに次にバイアスコイルに流れる電流の向きを逆にし、
２０ｍＡのバイアス電流を流しながら再生出力を読み取
ったところ、図３に示すように出力レベルが低く、信号
の再生は不可能であり、本発明の磁気記録媒体に特有の
バイアス依存性が得られた。また第２の磁性層３と第３
の磁性層４に形成された固定信号は信号パターンの凹凸
が反転しているため表面側が平坦となり固定信号の視認
性が悪く、目視で確認することは困難であった。Next, the present invention according to the first embodiment will be described in detail according to the method of use. First, the signal recorded on the first magnetic layer 2 was DC-erased by a reader / writer equipped with a write head capable of recording saturation on the first magnetic layer 2. Next, with the read head with the bias coil mounted on the same reader / writer, the third magnetic layer 4
When a reproduction output was read while a bias current of 20 mA at which a magnetic field equal to or higher than the saturation magnetic field was generated was passed at a predetermined polarity, a sufficient output level was obtained as shown in FIG. Next, reverse the direction of the current flowing through the bias coil,
When the read output was read while applying a bias current of 20 mA, the output level was low as shown in FIG. 3 and the signal could not be reproduced, and the bias dependency peculiar to the magnetic recording medium of the present invention was obtained. . The second magnetic layer 3 and the third magnetic layer 3
The fixed signal formed on the magnetic layer 4 was flat on the surface side because the unevenness of the signal pattern was inverted, the visibility of the fixed signal was poor, and it was difficult to visually confirm the fixed signal.
【００１３】（実施例２）実施例１の磁気記録媒体と同
様の製造方法で、第２の磁性層３に保磁力が２７０ Ｏ
ｅのγ−Ｆｅ2 Ｏ3 粉を用い、塗布方向に平行な６００
Ｏｅの直流配向処理を行い、厚さ５μｍで形成した。
次に第３の磁性層４に保磁力が９５０ ＯｅのＢａフェ
ライト粉を用い、第２の磁性層３を形成したときと逆極
性の１２００ Ｏｅの直流配向処理を行い、厚さ５μｍ
で形成した。実施例２について、実施例１と同様の評価
を行った。まず実施例１で使用したリーダーライダーで
第１の磁性層２に記録された信号を直流消去した。次に
第２の磁性層３の飽和磁界以上、第３の磁性層の飽和磁
界以下の磁界が発生する８０ｍＡのバイアス電流を所定
の極性で流しながら再生出力を読み取ったところ図２と
同様に十分な出力レベルが得られ、次にバイアスコイル
に流れる電流の向きを逆にして、８０ｍＡのバイアス電
流を流しながら再生出力を読み取ったところ、図３と同
様に出力レベルが低く、信号の再生は不可能であり、本
発明の磁気記録媒体に特有のバイアス依存性が得られ
た。また第２の磁性層３と第３の磁性層４に形成された
固定信号は信号パターンの凹凸が反転しているため表面
側が平坦となり固定信号の視認性が悪く、目視で確認す
ることは困難であった。(Embodiment 2) A coercive force of 270 O is applied to the second magnetic layer 3 by the same manufacturing method as that of the magnetic recording medium of Embodiment 1.
e using γ-Fe 2 O 3 powder, 600
DC orientation treatment of Oe was performed to form a film having a thickness of 5 μm.
Next, using a Ba ferrite powder having a coercive force of 950 Oe for the third magnetic layer 4, a direct current orientation treatment of 1200 Oe having a polarity opposite to that of forming the second magnetic layer 3 was performed, and the thickness was 5 μm.
Formed. About Example 2, the same evaluation as Example 1 was performed. First, the signal recorded on the first magnetic layer 2 was DC-erased by the leader rider used in Example 1. Next, the reproduction output was read while a bias current of 80 mA, which generates a magnetic field equal to or higher than the saturation magnetic field of the second magnetic layer 3 and equal to or lower than the saturation magnetic field of the third magnetic layer, was read at a predetermined polarity. When the reproduced output was read while the current flowing through the bias coil was reversed and a bias current of 80 mA was passed, the output level was low as in FIG. 3 and the signal was not reproduced. It is possible, and the bias dependency peculiar to the magnetic recording medium of the present invention was obtained. Further, the fixed signal formed on the second magnetic layer 3 and the third magnetic layer 4 has a flat surface side due to the inversion of the unevenness of the signal pattern, and the visibility of the fixed signal is poor, so that it is difficult to visually confirm the fixed signal. Met.
【００１４】（実施例３）実施例２の本発明の磁気記録
媒体を用いて、以下のような読取方法を行った。まず実
施例１で使用したリーダーライターで第１の磁性層２に
記録された信号を直流消去した。次に８０ｍＡのバイア
ス電流を所定の極性で流し配向処理を行った。これをバ
イアス電流を流さずに再生出力を読み取ったところ、図
２と同様に十分な出力レベルが得られた。次にバイアス
コイルに流れる電流の向きを逆にして、８０ｍＡのバイ
アス電流を流し、逆向きに配向処理を行った。これをバ
イアス電流を流さずに再生出力を読み取ったところ、図
３と同様に出力レベルが低く、信号の再生は不可能であ
り、本発明の磁気記録媒体に特有のバイアス依存性が得
られた。(Embodiment 3) Using the magnetic recording medium of the present invention of Embodiment 2, the following reading method was performed. First, the signal recorded on the first magnetic layer 2 was DC-erased by the reader / writer used in Example 1. Next, an orientation process was performed by flowing a bias current of 80 mA with a predetermined polarity. When the reproduced output was read without flowing a bias current, a sufficient output level was obtained as in FIG. Next, the direction of the current flowing through the bias coil was reversed, a bias current of 80 mA was passed, and the orientation treatment was performed in the reverse direction. When the reproduced output was read without flowing a bias current, the output level was low as in FIG. 3 and the signal could not be reproduced. As a result, a bias dependency peculiar to the magnetic recording medium of the present invention was obtained. .
【００１５】（実施例４）実施例１の磁気記録媒体と同
様の製造方法で、第１の磁性層に保磁力が１９００ Ｏ
ｅのＢａフェライト粉を用い、厚さ５μｍの第１の磁性
層２を形成した。次に、第２の磁性層３に保磁力が２７
５０ ＯｅのＢａフェライト粉を用い、塗布方向に平行
な１０００ Ｏｅの直流配向処理を行い、厚さ５μｍで
形成した。次に第３の磁性層４に保磁力が２７０ Ｏｅ
のγ−Ｆｅ2 Ｏ3 粉を用い、第２の磁性層３を形成した
ときと逆極性の６００ Ｏｅの直流配向処理を行い、厚
さ５μｍで形成した。実施例４の本発明の磁気記録媒体
を以下のような読み取り方法で行った。まず実施例１で
使用したリーダーライターのライトヘッドを用い、第２
の磁性層３の飽和磁界以上が発生する４００ｍＡの電流
を所定の極性で流し配向処理を行った。これをバイアス
電流を流さずに再生出力を読み取ったところ、図３と同
様に出力レベルが低く信号の再生は不可能であった。次
にリードヘッドを用い、第２の磁性層の飽和磁界以下、
第３の磁性層４の飽和磁界以上が発生する所定の極性と
逆極性の８０ｍＡのバイアス電流を流し、逆向きに配向
処理を行った。これをバイアス電流を流さずに再生出力
を読み取ったところ、図２と同様に十分な出力レベルが
得られ、本発明の磁気記録媒体に特有のバイアス依存性
が得られた。また第２の磁性層３と第３の磁性層４に形
成された固定信号は信号パターンの凹凸が反転している
ため表面側が平坦となり固定信号の視認性が悪く、目視
で確認することは困難であった。(Embodiment 4) A coercive force of 1900 O is applied to the first magnetic layer by the same manufacturing method as that of the magnetic recording medium of Embodiment 1.
e, the first magnetic layer 2 having a thickness of 5 μm was formed using the Ba ferrite powder. Next, a coercive force of 27 is applied to the second magnetic layer 3.
Using a 50 Oe Ba ferrite powder, a DC orientation treatment of 1000 Oe parallel to the coating direction was performed to form a 5 μm thick film. Next, the coercive force of the third magnetic layer 4 is set to 270 Oe.
Γ-Fe 2 O 3 powder was subjected to DC orientation treatment of 600 Oe having a polarity opposite to that of the second magnetic layer 3 to form a 5 μm thick film. The magnetic recording medium of the present invention of Example 4 was read by the following reading method. First, using the write head of the reader / writer used in Example 1, the second
A current of 400 mA, at which a magnetic field equal to or higher than the saturation magnetic field of the magnetic layer 3 is generated, flows with a predetermined polarity to perform orientation processing. When the reproduced output was read without flowing the bias current, the output level was low as in FIG. 3 and the signal could not be reproduced. Next, using a read head, the saturation magnetic field of the second magnetic layer or less,
A bias current of 80 mA having a polarity opposite to a predetermined polarity at which a magnetic field equal to or higher than the saturation magnetic field of the third magnetic layer 4 was generated, and the orientation treatment was performed in the opposite direction. When the reproduced output was read without flowing a bias current, a sufficient output level was obtained as in FIG. 2, and a bias dependency peculiar to the magnetic recording medium of the present invention was obtained. Further, the fixed signal formed on the second magnetic layer 3 and the third magnetic layer 4 has a flat surface side due to the inversion of the unevenness of the signal pattern, and the visibility of the fixed signal is poor, so that it is difficult to visually confirm the fixed signal. Met.
【００１６】（比較例１）実施例１と同様の製造方法で
第２の磁性層の製造工程を省略し、第１の磁性層上に第
３の磁性層による固定信号のみを形成し、同様の方法で
固定信号のバイアス依存性を確認した。図４、図５に示
すようにバイアス磁界の極性による出力レベルの変化は
見られなかった。(Comparative Example 1) A manufacturing method similar to that of the first embodiment is used, the manufacturing process of the second magnetic layer is omitted, and only a fixed signal by the third magnetic layer is formed on the first magnetic layer. The bias dependence of the fixed signal was confirmed by the method described above. As shown in FIGS. 4 and 5, no change in the output level due to the polarity of the bias magnetic field was observed.
【００１７】（比較例２、３、４）実施例１、２、４の
本発明の磁気記録媒体について、第２の磁性層３と第３
の磁性層４を形成するときの直流配向処理の方向を同極
にし、実施例１、２、３、４と同様の評価を行ったとこ
ろ、実施例と同様に本発明の磁気記録媒体と特有のバイ
アス依存性を示した。しかし、第２の磁性層３と第３の
磁性層４に同じ凹凸パターンの固定信号が重なって形成
されるため、表面からの視認性が良く、容易に目視可能
であった。(Comparative Examples 2, 3, and 4) Regarding the magnetic recording media of the present invention of Examples 1, 2, and 4, the second magnetic layer 3 and the third magnetic layer 3
The same evaluation was performed as in Examples 1, 2, 3, and 4 when the direction of the DC alignment treatment when forming the magnetic layer 4 was made the same polarity. Bias dependence. However, since the fixed signals of the same concavo-convex pattern were formed on the second magnetic layer 3 and the third magnetic layer 4 so as to overlap with each other, the visibility was good from the surface and easily visible.
【００１８】[0018]
【発明の効果】本発明によれば、磁気記録媒体の面内の
同一線上に各々反転したパターンの固定信号を形成した
少なくとも２つ以上の保磁力の異なる磁性層が積層して
形成されているため、本発明の磁気記録媒体に特有のバ
イアス依存性をもつ。また目視での固定パターンの確認
が困難である。このため、形成された固定信号と合わせ
て、バイアス依存性を利用することにより媒体を特定す
るための識別情報として使用すれば、偽造や変造に対し
極めて安全性の高い磁気記録媒体を提供できる。According to the present invention, at least two or more magnetic layers having different coercive forces, each forming a fixed signal having an inverted pattern, are formed on the same line in the plane of the magnetic recording medium. Therefore, the magnetic recording medium of the present invention has a bias dependency peculiar to the magnetic recording medium. Also, it is difficult to visually confirm the fixed pattern. For this reason, if it is used as identification information for specifying the medium by utilizing the bias dependency together with the formed fixed signal, it is possible to provide a magnetic recording medium with extremely high security against forgery and alteration.
【図面の簡単な説明】[Brief description of the drawings]
【図１】本発明の一実施例としての磁気記録媒体の断面
図である。FIG. 1 is a sectional view of a magnetic recording medium according to one embodiment of the present invention.
【図２】実施例１の磁気記録媒体を所定の極性でバイア
スリードしたときのエンベロープを示す。FIG. 2 shows an envelope when the magnetic recording medium of Example 1 is bias-read with a predetermined polarity.
【図３】実施例１の磁気記録媒体を所定の極性と逆極性
でバイアスリードしたときのエンベロープを示す。FIG. 3 shows an envelope when the magnetic recording medium of Example 1 is bias-read with a polarity opposite to a predetermined polarity.
【図４】比較例１の磁気記録媒体を所定の極性でバイア
スリードしたときのエンベロープを示す。FIG. 4 shows an envelope when the magnetic recording medium of Comparative Example 1 is bias-read with a predetermined polarity.
【図５】比較例１の磁気記録媒体を所定の極性と逆極性
でバイアスリードしたときのエンベロープを示す。FIG. 5 shows an envelope when the magnetic recording medium of Comparative Example 1 is bias-read with a polarity opposite to a predetermined polarity.
１ 非磁性基体 ２ 第１の磁性層 ３ 第２の磁性層 ４ 第３の磁性層 DESCRIPTION OF SYMBOLS 1 Nonmagnetic substrate 2 1st magnetic layer 3 2nd magnetic layer 4 3rd magnetic layer
Claims (4)
力の異なる少なくとも２つの磁性層を含む３層以上の磁
性層を積層して成る磁気記録媒体において、前記磁性層
のうち前記少なくとも２つの磁性層は他の磁性層に記録
された信号による磁界並びに配向磁界の影響により形成
された書換不能な固定信号が、前記磁気記録媒体の面内
の同一線上に各々反転したパターンとして記録されてい
ることを特徴とする磁気記録媒体。1. A magnetic recording medium in which three or more magnetic layers including at least two magnetic layers having different coercive forces are laminated on the whole or a part of a non-magnetic substrate, wherein at least one of the magnetic layers is In the two magnetic layers, a non-rewritable fixed signal formed by the influence of the magnetic field and the orientation magnetic field due to the signal recorded on the other magnetic layer is recorded as an inverted pattern on the same line in the plane of the magnetic recording medium. A magnetic recording medium, comprising:
から成る第１の磁性層を形成し、次いで前記第１の磁性
層に所定の信号を磁気記録し、その後磁性塗料を塗布、
乾燥、固化して前記第２の磁性層を形成し、次いで第２
の磁性層とは保磁力の異なる磁性塗料を塗布、乾燥、固
化することにより第３の磁性層を形成することよりな
り、前記第２の磁性層は、前記磁性塗料が乾燥固化する
前に前記第１磁性層の保磁力以下の磁界強度で且つ一つ
の磁界極性で、塗布方向に対し平行な直流配向処理を受
け、次いで前記第３の磁性層は、前記磁性塗料が乾燥固
化する前に前記第１磁性層の保磁力以下の磁界強度で且
つ前記第２の磁性層に対する前記一つの磁界極性とは異
なった磁界極性で、塗布方向に対し平行な直流配向処理
を受けることを特徴とする磁気記録媒体の製造方法。2. A first magnetic layer made of a magnetic material capable of being magnetically recorded is formed on a non-magnetic substrate, a predetermined signal is magnetically recorded on the first magnetic layer, and a magnetic paint is applied thereafter.
Drying and solidifying to form the second magnetic layer;
The magnetic layer is formed by applying a magnetic paint having a different coercive force, drying, and solidifying to form a third magnetic layer. The second magnetic layer is formed before the magnetic paint is dried and solidified. With a magnetic field strength less than or equal to the coercive force of the first magnetic layer and with one magnetic field polarity, subjected to a DC orientation treatment parallel to the coating direction, and then the third magnetic layer is subjected to the magnetic coating before the magnetic paint is dried and solidified. A magnetic field which is subjected to a DC orientation treatment parallel to the coating direction at a magnetic field strength equal to or lower than the coercive force of the first magnetic layer and at a magnetic field polarity different from the one magnetic field polarity for the second magnetic layer. Manufacturing method of recording medium.
ッドで所定の極性の第１のバイアス磁界を印加しなが
ら、または印加後に前記磁気記録媒体を読み取ったとき
の出力レベルと、前記所定の極性とは逆極性の第２のバ
イアス磁界を印加しながら、または印加後に前記磁気記
録媒体を読み取ったときの出力レベルとを比較し、その
出力レベルの差を認識することを特徴とする磁気記録媒
体の使用方法。3. An output level when the magnetic recording medium according to claim 1 is read with or without applying a first bias magnetic field of a predetermined polarity with a magnetic head. And comparing the output level when the magnetic recording medium is read with or after applying a second bias magnetic field having a polarity opposite to the polarity of the magnetic field, and recognizing a difference between the output levels. How to use the recording medium.
録媒体を前記同一線に沿って前記バイアス磁界よりも大
きい一定の直流磁界で予め磁化することを特徴とする請
求項３の使用方法。4. The method according to claim 3, wherein the magnetic recording medium is magnetized in advance with a constant DC magnetic field larger than the bias magnetic field along the same line before reading by the magnetic head.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20740097A JP3760031B2 (en) | 1997-07-17 | 1997-07-17 | Magnetic recording medium and method for manufacturing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20740097A JP3760031B2 (en) | 1997-07-17 | 1997-07-17 | Magnetic recording medium and method for manufacturing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1139604A true JPH1139604A (en) | 1999-02-12 |
| JP3760031B2 JP3760031B2 (en) | 2006-03-29 |
Family
ID=16539125
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP20740097A Expired - Fee Related JP3760031B2 (en) | 1997-07-17 | 1997-07-17 | Magnetic recording medium and method for manufacturing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3760031B2 (en) |
-
1997
- 1997-07-17 JP JP20740097A patent/JP3760031B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP3760031B2 (en) | 2006-03-29 |
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