JPH0393034A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve signal-to-noise ratio of a magnetic recording medium for recording two or more signals of different wavelengths by constituting the magnetic layer of a multilayer structure in a manner that a layer of deeper side has larger coercive force than the surface layer side. CONSTITUTION:On a nonmagnetic substrate 3, there are formed a magnetic layer 5 of a multilayer structure comprising a surface side magnetic layer 7 and a deeper side magnetic layer 9. The magnetic material or compositions of these layers are selected so as to obtain larger coercive force in the layer 9 than in the layer 7. By this method, when data is recorded in the surface side, data in the deeper layer is hardly erased and thus, signal output in the surface side can be improved to increase the signal-noise ratio.

Description

【発明の詳細な説明】 ［産業上の利用分野コ 本発明は磁気記録媒体に関する。更に詳細には、本発明
は多層記録時の電磁変換特性が向上された磁気記録媒体
に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium. More specifically, the present invention relates to a magnetic recording medium with improved electromagnetic conversion characteristics during multilayer recording.

［従来の技術コ ビデオの長時間モードの出現とテレビ放送の音声多重化
がほぼ同時期に生じたため、長時間モード化による音質
低下と、録画する時の音声のハイファイ化という相反す
る要求がＶＴＲに生じた。[Conventional technology] The appearance of the long-duration mode in co-video and the multiplexing of audio in television broadcasting occurred at about the same time, so the conflicting demands of deteriorating sound quality due to the long-duration mode and high-fidelity audio when recording were created for VTRs. occured.

この要求を満たすために、第６図に示されるようなＶＨ
Ｓハイファイ方式による深層記録方式が開発された。こ
の方式によれば、非磁性基体１ｏＯの上面に磁性層１１
０が形成されている磁気記録媒体１２０の磁性層１１０
の深部に、最初に長波長の音声信号を広いギャップ長の
へッド１３０でアジマス角θ２で記録し、次に、磁性層
１１ｏの表層部に、短波長の映像信号を狭いギャップ長
のヘッド１４０でアジマス角θ１　（θ２〉θｌ）で２
段重ねのように記録する。従って、この方式では、最初
に記録した音声信号が非磁性基体側に残って深層記録と
なり、映像信号は表層記録となる。In order to meet this requirement, a VH as shown in FIG.
A deep recording method using the S Hi-Fi method was developed. According to this method, a magnetic layer 11 is formed on the upper surface of the nonmagnetic substrate 1oO.
0 is formed on the magnetic layer 110 of the magnetic recording medium 120.
First, a long wavelength audio signal is recorded in the deep part of the magnetic layer 11o at an azimuth angle θ2 using a head 130 with a wide gap length, and then a short wavelength video signal is recorded in the surface layer part of the magnetic layer 11o with a head 130 with a narrow gap length. 140 and azimuth angle θ1 (θ2>θl) is 2
Record in stacks. Therefore, in this method, the audio signal recorded first remains on the non-magnetic substrate side and becomes a deep layer recording, and the video signal becomes a surface layer recording.

このようなＶＨＳハイファイの音声信号の深層記録方式
の原理は、強い磁界で磁性体層の深くまで記録した後に
、それよりも小さな磁界で記録していくと、表面部分は
後から記録した信号になるが、深部は消し残りが生じる
ことを利用するものである。この「消し残り」をうまく
活用することにより、２種類の信号を同時に磁気記録媒
体一ヒに存在させることが可能となる。The principle behind the deep recording method for VHS high-fidelity audio signals is that if you record deep into the magnetic layer using a strong magnetic field and then record using a weaker magnetic field, the surface area will be affected by the later recorded signal. However, this method takes advantage of the fact that some areas remain unerased in the deep areas. By making good use of this "unerased data", it is possible to have two types of signals simultaneously exist on a magnetic recording medium.

一方、フロッピーディスク装置やハードディスク装置に
おいても大容量化を目指して深層にサーボ信号を記録し
ておいてトラックサーボを行う方式が提案されている。On the other hand, with the aim of increasing the capacity of floppy disk devices and hard disk devices, a method has been proposed in which servo signals are recorded deep in the disk and track servo is performed.

［発明が解決しようとする課題］ しかし、これらの方式においては信号を重ね書きしてい
るため深層側信号が小さい問題がある。[Problems to be Solved by the Invention] However, in these methods, there is a problem that the deep side signal is small because the signals are overwritten.

また、表層記録信号と深層記録信号の波長の差が小さく
なると、深層記録信号の出力低下が特に問題となる。波
長差が小さいということは、換言すれば、記録深さの差
が小さいということであり、最初に記録した音声信号が
後から記録された映像信号により消去される率が高まり
、「消し残り」晴が少なくなるので、笥声信号の抜き出
しが極めて困難になる。その結果、Ｓ／Ｎ比が低下し、
ＶＨＳハイファイ方式本来の効果が得られない。Furthermore, when the difference in wavelength between the surface recording signal and the deep recording signal becomes small, a decrease in the output of the deep recording signal becomes a particular problem. In other words, a small wavelength difference means a small difference in recording depth, which increases the chance that the first recorded audio signal will be erased by a later recorded video signal, resulting in "unerased" As the weather becomes less clear, it becomes extremely difficult to extract the whispering signal. As a result, the S/N ratio decreases,
The original effects of the VHS high-fidelity system cannot be obtained.

この発明は、上記従来製品が持っていた深層記録の出力
が小さいという欠点を解決することを目的とする。The purpose of this invention is to solve the drawback that the conventional products have a low output for deep recording.

［課題を解決するための千段］ 前記目的を達成するために、本発明では、非磁性基体上
に磁性層を有し、波長の異なる少なくとも２つ以上の信
号が重ね記録される磁気記録媒体において、前記磁性層
は少なくとも２層以．Ｌの積層構造を有し、磁性層の非
磁性基体寄り部分の保磁力が磁性層の表層寄り部分の保
磁力よりも高いことを特徴とする磁気記録媒体を提供す
る。[A thousand steps to solve the problem] In order to achieve the above object, the present invention provides a magnetic recording medium that has a magnetic layer on a non-magnetic substrate and in which at least two or more signals having different wavelengths are recorded in a superimposed manner. In this case, the magnetic layer has at least two layers. Provided is a magnetic recording medium having a laminated structure of L, and characterized in that the coercive force of the portion of the magnetic layer closer to the nonmagnetic substrate is higher than the coercive force of the portion of the magnetic layer closer to the surface layer.

積層構造磁性層の表層寄り部分の厚みは、該表層寄り部
分に記録される信号の波長の０．２〜０．３倍程度であ
ることが好ましい。The thickness of the surface-side portion of the laminated structure magnetic layer is preferably about 0.2 to 0.3 times the wavelength of the signal recorded on the surface-side portion.

また、積層構造磁性層全体の厚みは深層記録信号の波長
の１／３以上であることが好ましい。Further, it is preferable that the total thickness of the laminated structure magnetic layer is 1/3 or more of the wavelength of the deep recording signal.

［作用］ 前記のように、本発明の磁気記録媒体の磁性層は多層構
造を有し、深層側の保磁力が表層側の保磁力よりも高く
されている。このように、表層側よりも深層側の保磁力
を高くすると、表層側の信号を記録した時に、最初に記
録した深層側信号が消去されにくくなり、Ｓ／Ｎ比を高
くすることができる。[Function] As described above, the magnetic layer of the magnetic recording medium of the present invention has a multilayer structure, and the coercive force on the deep layer side is higher than the coercive force on the surface layer side. In this way, by making the coercive force higher on the deep layer side than on the surface layer side, when the surface layer side signal is recorded, the first recorded deep layer side signal is less likely to be erased, and the S/N ratio can be increased.

［実施例］ 以下、実施例により本発明を更に詳細に説明する。[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

第１図は本発明による磁気記録媒体の断面図である。磁
気記録媒体ｌは非磁性基体３上に磁性層５を形成した構
成であり、磁性層５は多層構造となっており、表層側の
第１磁性層７および深層側の第２磁性層９により構成さ
れる。FIG. 1 is a cross-sectional view of a magnetic recording medium according to the present invention. The magnetic recording medium 1 has a structure in which a magnetic layer 5 is formed on a non-magnetic substrate 3, and the magnetic layer 5 has a multilayer structure, with a first magnetic layer 7 on the surface side and a second magnetic layer 9 on the deep side. configured.

磁性層は磁性体とバインダの混合物を非磁性基体に塗布
するか、または磁性体を非磁性基体にベーパデボジシａ
冫法により被着させることにより形成することができる
。このような磁性層形成方法は何れも当業者に周知であ
る。本発明の多層構造磁性層は複数回塗布するか、また
は、複数回ベーパデボジシａンを繰り返すことにより作
製できる。The magnetic layer is formed by coating a mixture of a magnetic material and a binder on a non-magnetic substrate, or by vapor depositing a magnetic material onto a non-magnetic substrate.
It can be formed by applying it by a chemical method. All such magnetic layer forming methods are well known to those skilled in the art. The multilayer structure magnetic layer of the present invention can be produced by applying the coating multiple times or repeating vapor deposition a multiple times.

本発明の磁気記録媒体の磁性層の形成に使用できる磁性
体としては、ＣＯ％　Ｆｅｓ　Ｎｉ，Ｃｏ−Ｆｅ１Ｃｏ
−Ｎｉ１Ｆｅ−Ｎｉｓ　Ｆｅ−Ｒｈ，Ｆｅ−Ｃｕ１Ｆｅ
−Ａｕｔ　Ｃｏ−Ｃｕｘ　Ｃｏ−Ａ　ｕ　ｓ　Ｃ　ｏ　
−　Ｃ　ｒ　ｓ　Ｃ　ｏ　−　Ｐ　ｓ　Ｃ　ｏ　−　Ｙ
　ｓ　Ｃ　ｏ　−１，ａ％Ｇｏ−Ｍｎｓ　Ｆｅ−Ｃｏ−
Ｎｉｓ　Ｆｅ−Ｍｎｓ　Ｎｉ−Ｍｎ１Ｎｉ−Ｃｕｓ　Ｆ
ｅ−ＳｉｓＭｎ−Ｓｂｓ　Ｍｎ−Ａ，Ｉ２、Ｃｏ−Ｇａ
ｓ　Ｃｏ−Ｇｄ％Ｇｏ−　　Ｓｍｓ　Ｃｏ−Ｐｔｓ　Ｍ
ｎ−Ｂｉｓｙ−Ｆｅ２０ａ　ｓ　Ｃｏ−ｒ−Ｆ　ｅ２゜
０３、Ｆｅ３０４　、Ｃ　ｒ　０２などが挙げられる。Examples of magnetic materials that can be used to form the magnetic layer of the magnetic recording medium of the present invention include CO% Fes Ni, Co-Fe1Co
-Ni1Fe-Nis Fe-Rh, Fe-Cu1Fe
-Aut Co-Cux Co-A us Co
- C r s Co - P s Co - Y
s Co -1,a%Go-Mns Fe-Co-
Nis Fe-Mns Ni-Mn1Ni-Cus F
e-SisMn-Sbs Mn-A, I2, Co-Ga
s Co-Gd%Go- Sms Co-Pts M
Examples include n-Bisy-Fe20a s Cor-F e2°03, Fe304, Cr02, and the like.

その他の強磁性体も当然使用できる。Other ferromagnetic materials can of course also be used.

本発明で重要なことは、深層側磁外層と表層側磁性層と
の構成強磁性体材料が同一であってはならず、深層側磁
性層の保磁力のほうが、表層側磁性層の保磁力よりも高
くなるように各層の磁性体材料を選択しなければならな
い。合金にような複数の元素からなる磁性体材料の場合
には、その組成比を変化させることによっても前記の要
件を満たすことができる。また、磁性体の作製条件を変
えることにより別状比や粒径が変わり、前記の要ｅｔ＝
を満たすこともできる。従って、本明細書における“異
なる磁性体材料”という用語は、構成元素が全く異なる
！ｉｊ−．．−系または合金系磁性体材料の他、同じ構
成元素で異なる組成比の合金系磁性体材料または針状比
など磁性体の形状の異なる酸化物なども含む意味で使用
されている。What is important in the present invention is that the constituent ferromagnetic materials of the deep outer magnetic layer and the surface magnetic layer must not be the same, and the coercive force of the deep magnetic layer is higher than the coercive force of the surface magnetic layer. The magnetic material of each layer must be selected so that the height is higher than . In the case of a magnetic material made of a plurality of elements such as an alloy, the above requirements can also be met by changing the composition ratio. In addition, by changing the manufacturing conditions of the magnetic material, the separation ratio and particle size can be changed, and the above requirements et=
It is also possible to satisfy Therefore, the term "different magnetic materials" in this specification means that the constituent elements are completely different! ij-. ．． In addition to --based or alloy-based magnetic materials, the term is used to include alloy-based magnetic materials with the same constituent elements but different composition ratios, or oxides with different magnetic shapes such as acicular ratios.

本発明の磁気記録媒体に使用される非磁性基板としては
、ポリイミド，ポリエチレンテレフタレート等の高分子
フィルム，ガラス類，セラミック，アルミ，陽極酸化ア
ルミ，黄銅などの金属板，Ｓｉ　ｌ−結晶板，表面を熱
酸化処理したＳｆｌｉ結晶板などがある。この非磁外基
体は必要に応じて　ｉＦ而研磨やテクスチャリング加工
を行うためのニッケル●リン系合金層やアルマイト処理
層等のド地研磨層を設けることもできる。Non-magnetic substrates used in the magnetic recording medium of the present invention include polymer films such as polyimide and polyethylene terephthalate, glasses, ceramics, aluminum, anodized aluminum, metal plates such as brass, Si l-crystal plates, and surfaces. There are Sfli crystal plates that are thermally oxidized. This non-magnetic substrate may be provided with a ground polishing layer such as a nickel-phosphorus alloy layer or an alumite treatment layer for iF polishing or texturing processing, if necessary.

また、磁気記録媒体としては、ポリエステルフィルム、
ポリエチレンテレフタレートフィルム、ポリイミドフィ
ルムなどの合成樹脂フィルムを基体とする磁気テープや
磁気ディスク、合成樹脂フィルム、アルミニウム板およ
びガラス板等からなる円盤やドラムを基体とする磁気デ
ィスクや磁気ドラムなど、磁気ヘッドと摺接する構造の
種々の形態を包含する。In addition, as magnetic recording media, polyester film,
Magnetic tapes and magnetic disks based on synthetic resin films such as polyethylene terephthalate film and polyimide film, magnetic disks and magnetic drums based on disks and drums made of synthetic resin films, aluminum plates, glass plates, etc. It includes various forms of sliding contact structures.

下記の実施例において、各層の磁気特性の測定は、深層
側を塗布した後に、磁性層厚みおよび磁気特性を測定し
ておき、表層側の塗布後に表層と深層を合わせた測定値
より表層および深層単独の磁気特性を調べた。また、電
磁変換特性は市販のＳ−ＶＨＳ用ビデオデッキを使用し
て、最初にギャップ長１．１μｍのフエライトヘッドで
長波長側の信号（波長３．６μｍ）を記録し、この−Ｌ
にギャノブ長０．８μｍのフエライトヘッドで短波長側
信号（波長２．４μｍ）を記録して行った。In the examples below, the magnetic properties of each layer are measured by first measuring the magnetic layer thickness and magnetic properties after coating the deep layer, and then determining the surface and deep layers from the combined measurement values after coating the surface layer. The individual magnetic properties were investigated. In addition, the electromagnetic conversion characteristics were determined by using a commercially available S-VHS video deck, first recording a signal on the long wavelength side (wavelength 3.6 μm) with a ferrite head with a gap length of 1.1 μm, and then recording the -L
The short wavelength signal (wavelength 2.4 μm) was recorded using a ferrite head with a Ganob length of 0.8 μm.

Ｌ息撚上 磁性粉としてコバルト含有γ一酸化鉄を用いて第２図に
示されるような、保磁力（ＨＣＩ　）が９０００ｅで、
飽和磁束密度が１８００Ｇの表屓（第１磁性層）７と、
保磁力（Ｈｃ２　）が８００−１０５００ｅで、飽゛和
磁東密度が１８００Ｇ一定の深洲（第２磁性雇）９とか
らなる磁性崩５を有する磁気記録媒体１を作製した。表
層と深層の保磁力はＣｏとγ一酸化鉄の組成比を変化さ
せることにより所望の値に調整した。表層と深層の合計
厚みを２．４μｍ一定とし、表層の厚み（ｔ１）が０．
６μｍまたは０．９μｍの２種類の媒体を作製した。各
表層厚み（ｔｘ）における深層保磁力（Ｈｃ２）を８　
０　００ｅ〜１　０　５　００ｅの範囲内で変化させた
場合の各屓の規格化出力を測定した。結果を第３図に要
約して示す。Using cobalt-containing γ-iron monoxide as the L-breath twisted magnetic powder, the coercive force (HCI) is 9000e as shown in Figure 2.
A surface (first magnetic layer) 7 having a saturation magnetic flux density of 1800G,
A magnetic recording medium 1 having a magnetic deformation 5 consisting of a Fukashu (second magnetic material) 9 having a coercive force (Hc2) of 800-10500e and a saturation magnetic east density of 1800G was produced. The coercivity of the surface layer and the deep layer was adjusted to a desired value by changing the composition ratio of Co and γ iron monoxide. The total thickness of the surface layer and deep layer is constant at 2.4 μm, and the thickness of the surface layer (t1) is 0.
Two types of media were prepared: 6 μm or 0.9 μm. The deep coercive force (Hc2) at each surface layer thickness (tx) is 8
The normalized output of each scale was measured when changing within the range of 0 00e to 1 0 500e. The results are summarized in Figure 3.

第３図において一点鎖線で示された表層信号の出力特性
曲線から明らかなように、表層信号の出力は、表層厚み
および深層保磁力が変化してもさほど影響を受けない。As is clear from the surface signal output characteristic curve indicated by the dashed line in FIG. 3, the surface signal output is not significantly affected by changes in the surface layer thickness and deep coercive force.

これに対して、第３図において実線で示された深層信号
の出力は、表層厚みが０．６μｍの場合、深層保磁力が
増大するにつれて深層信号出力も高くなるが、表層厚み
が０．９μｍの場合には、深層保磁力が表層保磁力と同
じ９０００ｅの値を超える頃から逆に減少してしまう。On the other hand, when the surface layer thickness is 0.6 μm, the deep layer signal output increases as the deep coercive force increases, but the deep layer signal output shown by the solid line in FIG. In this case, the deep coercive force starts to decrease when it exceeds the same value of 9000e as the surface coercive force.

なお、表層出力が最大になったときの表層記録電流は０
．８ＡＴｐ−ｐであり、深層出力が最大になったときの
深層記録電流は２．ＯＡＴｐ−ｐであった。Note that the surface recording current when the surface layer output reaches its maximum is 0.
．． 8ATp-p, and the deep recording current when the deep output is maximum is 2. It was OATp-p.

また、深層保磁力を１０５００ｅ一定とし、かつ、積層
構造磁性層の全体厚みを２．４μｍ一定として、表層の
厚みを０．５〜０．９μｍの範囲内で変化させた場合の
表層と深層の山力の変化を測定した。結果を第４図に示
す。In addition, when the deep coercive force is constant at 10500e and the overall thickness of the laminated magnetic layer is constant at 2.4 μm, the thickness of the surface layer is varied within the range of 0.5 to 0.9 μm. Changes in mountain power were measured. The results are shown in Figure 4.

第４図において−・点鎖線で示された表層信号の出力は
表層厚みが０．７μｍを超えると殆ど増加せず、一方、
表層厚みが０．５μｍ未満の場合には減少が著しくなる
。一方、実線で示された深層信号出力は表層厚みの増大
につれて減少し続けるが、表層厚みを０．７μｍ以下に
薄くすると、深層信号の出力は従来の単層構造の磁気記
録媒体に比べて向上する。しかし、表層の厚みを薄くし
すぎると、表層の信号の低下が大きくなるので表層厚み
を０．５μｍ以上とする必要がある。従って、表層信号
出力と深層信号出力の兼ね合いを考慮して、表層厚みは
表層記録信号の波長の０．２倍〜０．３倍の範囲内に設
定することが好ましい。また、表層信号磁化の厚み分布
は自己減磁作用から、表層信号の記録波長に比例すると
考えられるので、この点からも表層の厚みを表層信号の
記録波長に対して０．２〜０．３倍とすることが好まし
い。In Fig. 4, the output of the surface layer signal indicated by the dotted chain line hardly increases when the surface layer thickness exceeds 0.7 μm;
When the surface layer thickness is less than 0.5 μm, the decrease becomes significant. On the other hand, the deep signal output shown by the solid line continues to decrease as the surface layer thickness increases, but when the surface layer thickness is reduced to 0.7 μm or less, the deep signal output improves compared to conventional single-layer magnetic recording media. do. However, if the thickness of the surface layer is made too thin, the signal of the surface layer will be greatly reduced, so the thickness of the surface layer must be 0.5 μm or more. Therefore, in consideration of the balance between the surface layer signal output and the deep layer signal output, the surface layer thickness is preferably set within a range of 0.2 to 0.3 times the wavelength of the surface layer recording signal. In addition, the thickness distribution of the surface layer signal magnetization is considered to be proportional to the recording wavelength of the surface layer signal due to the self-demagnetization effect, so from this point of view as well, the thickness of the surface layer is 0.2 to 0.3 with respect to the recording wavelength of the surface layer signal. It is preferable to double the amount.

実１０残二一 次に、この効果を最大限に引き出すため、表層は実施例
ｌと同じくコバルト含有γ一酸化鉄を用いて保磁力９０
００ｅ，飽和磁束密度１８００Ｇとし、深層にα一Ｆｅ
磁性粉を用いて保磁力１４０Ｑ　Ｏｅ１飽和磁束密度２
５００Ｇ、表層厚み０．６μｍとして、同様の実験を行
った。この場合、深層出力は従来の単層構造の磁気記録
媒体に比べて１．５倍に増大した。Next, in order to maximize this effect, the surface layer is made of cobalt-containing γ iron monoxide with a coercive force of 90 as in Example 1.
00e, saturation magnetic flux density 1800G, and α-Fe in the deep layer.
Coercive force 140Q Oe1 Saturation magnetic flux density 2 using magnetic powder
A similar experiment was conducted using 500G and a surface layer thickness of 0.6 μm. In this case, the deep output was increased by 1.5 times compared to a conventional single-layer magnetic recording medium.

実１号』ユ 次に、この実験結果に基づき、本発明をＶＴＲに応用し
た。ＶＴＲの音声信号の品質向上を目的に、従来の映像
信号とＦＭｇ−声信号の間にＰＣＭ変調した音声信号の
記録を行った。第５図に各信号の周波数−！汗域を示す
。各信号用の磁気ヘッドとしては、それぞれギャップ長
が０．３μｍ１０．８ｕｍｓ　１．ｌμｍで、コア材料
がＭｎ−Ｚｎフェライトのものを使用した。ここで、３
つの信号のうち、ＰＣＭ音声信号とＦＭ音声信号は・ｊ
ＩＦ域が接近しているため、ＦＭ音声信号の低下が問題
となる。そこで、本発明による磁性層の多層化をＰＣＭ
音声信号とＦＭ音声信号の間で試みた。Next, based on the results of this experiment, the present invention was applied to a VTR. In order to improve the quality of VTR audio signals, we recorded an audio signal that was PCM-modulated between a conventional video signal and an FMg-voice signal. Figure 5 shows the frequency of each signal -! Shows sweat area. The magnetic head for each signal has a gap length of 0.3 μm and 10.8 ums. 1. 1 μm, and the core material used was Mn-Zn ferrite. Here, 3
Of the two signals, the PCM audio signal and FM audio signal are ・j
Since the IF ranges are close together, deterioration of the FM audio signal becomes a problem. Therefore, the multilayering of the magnetic layer according to the present invention is
I tried between audio signal and FM audio signal.

すなわち、磁性層全体の厚みが２．４μｍの磁気記録媒
体において、表面から０．６μｍの厚み（表層記録信号
であるＰＣＭ音声信号の波長２．４μｍの０．２５倍）
の表層をＧｏ含有γ一酸化鉄（保磁力９０００ｅ）で形
成し、深層をα一Ｆｅで形成し、保磁力をｌ０５００ｅ
とした。飽和磁束密度は両層とも１８００Ｇとした。こ
れにＦＭ音声信号、ＰＣＭ音声信号および映像信号の３
つの信号を重ね書きした。この結果、実施例１と同様に
、従来の単層媒体に比べて、ＦＭ音声信号の出力が１．
２倍にまで増大したが、この時、ＰＣＭ音声信号および
ＦＭ音声信号の劣化は認められなかった。That is, in a magnetic recording medium in which the total thickness of the magnetic layer is 2.4 μm, the thickness is 0.6 μm from the surface (0.25 times the wavelength of 2.4 μm of the PCM audio signal, which is the surface recording signal).
The surface layer is formed of Go-containing γ-iron monoxide (coercive force 9000e), and the deep layer is formed of α-Fe, with a coercive force of 10500e.
And so. The saturation magnetic flux density was 1800G for both layers. In addition to this, FM audio signal, PCM audio signal and video signal are added.
Two signals were overwritten. As a result, as in the first embodiment, the output of the FM audio signal is 1.
However, no deterioration of the PCM audio signal and FM audio signal was observed at this time.

［発明の効果］ 以上説明したように、本発明によれば、磁性層を多層化
して、深層側の保磁力を表層側よりも高＜シ、表層厚み
を表層記録信号波長の０．２〜０．３倍の範囲内に設定
することにより、表層側の信号出力を低下することなし
に、深層側の信号出力を向上させ、その結果、Ｓ／Ｎ比
を高めることができる。[Effects of the Invention] As explained above, according to the present invention, the magnetic layer is multilayered, the coercive force on the deep layer side is higher than the surface layer side, and the surface layer thickness is set to 0.2 to 0.2 of the surface recording signal wavelength. By setting within the range of 0.3 times, the signal output on the deep layer side can be improved without reducing the signal output on the surface layer side, and as a result, the S/N ratio can be increased.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は本発明による磁気記録媒体の断面図であり、第
２図は実施例１における磁気記録媒体の部分断面図であ
り、第３図は実施例ｌにおける磁気記録媒体の表層信号
出力または深層信号出力と深層保磁力との関係を示す特
性図であり、第４図は実施例１における磁気記録媒体の
表層信号出力または深層信号出力と表層厚みとの関係を
示す特性図であり、第５図は実施例３における記録信号
の周波数帯域を示す波形図であり、第６図は従来の深層
記録方式を示す模式図である。 １・・・本発明の磁気記録媒体 ３・・・非磁性基体 ５・・・積層構造磁性層 ７・・・表層側磁性層 ９・・・深層側磁性層FIG. 1 is a cross-sectional view of the magnetic recording medium according to the present invention, FIG. 2 is a partial cross-sectional view of the magnetic recording medium in Example 1, and FIG. 3 is a partial cross-sectional view of the magnetic recording medium in Example I. FIG. 4 is a characteristic diagram showing the relationship between deep layer signal output and deep layer coercive force; FIG. 4 is a characteristic diagram showing the relationship between surface layer signal output or deep layer signal output and surface layer thickness of the magnetic recording medium in Example 1; FIG. 5 is a waveform diagram showing the frequency band of the recording signal in Example 3, and FIG. 6 is a schematic diagram showing the conventional deep recording method. 1...Magnetic recording medium of the present invention 3...Nonmagnetic substrate 5...Laminated structure magnetic layer 7...Surface side magnetic layer 9...Deep side magnetic layer

Claims (4)

【特許請求の範囲】[Claims] （１）非磁性基体上に磁性層を有し、波長の異なる少な
くとも２つ以上の信号が重ね記録される磁気記録媒体に
おいて、前記磁性層は少なくとも２層以上の積層構造を
有し、磁性層の非磁性基体寄り部分の保磁力が磁性層の
表層寄り部分の保磁力よりも高いことを特徴とする磁気
記録媒体。(1) In a magnetic recording medium that has a magnetic layer on a nonmagnetic substrate and in which at least two or more signals with different wavelengths are recorded in a superimposed manner, the magnetic layer has a laminated structure of at least two or more layers, and the magnetic layer A magnetic recording medium characterized in that the coercive force of a portion of the magnetic layer closer to the nonmagnetic substrate is higher than the coercive force of the portion of the magnetic layer closer to the surface layer. （２）積層構造磁性層の表層寄り部分の厚みは、該表層
寄り部分に記録される信号の波長の０．２〜０．３倍の
範囲内であることを特徴とする請求項１記載の磁気記録
媒体。(2) The thickness of the surface-side portion of the laminated structure magnetic layer is within the range of 0.2 to 0.3 times the wavelength of the signal recorded in the surface-side portion. magnetic recording medium. （３）積層構造磁性層の全体厚みは、磁性層の非磁性基
体寄り部分に記録される信号の波長の１／３以上である
ことを特徴とする請求項１記載の磁気記録媒体。(3) The magnetic recording medium according to claim 1, wherein the total thickness of the laminated structure magnetic layer is 1/3 or more of the wavelength of a signal recorded in a portion of the magnetic layer closer to the nonmagnetic substrate. （４）積層構造磁性層の表層寄り部分と非磁性基体寄り
部分とはそれぞれ異なる磁性体材料により構成されてい
ることを特徴とする請求項１記載の磁気記録媒体。(4) The magnetic recording medium according to claim 1, wherein the portion of the laminated structure magnetic layer closer to the surface layer and the portion closer to the nonmagnetic substrate are each made of different magnetic materials.