JPS5857630A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To keep all bands at a high level of reproduced output and to reduce noises, by selecting the specific surface area, the coercive force, etc. for the magnetic powder of the upper and lower magnetic layers which have magnetic metallic thin films on the surface, respectively. CONSTITUTION:The 1st magnetic layer 4 containing the magnetic powder of at least one of Co-coated iron oxide or CrO2 of 20-30m<2>/g specific surface area and obtained by a BET process is formed on a nonmagnetic substrate 1 along with the 2nd magnetic layer 5 containing the magnetic powder of at least one of the Co-coated iron oxide or CrO2 of 30-50m<2>/g specific area and obtained by a BET process. Then a magnetic metallic thin film layer 7 of Co, etc. is formed on the surface of the layer 5 by an oblique vapor deposition process, etc. At the same time, the coercive force of the layer 5 is set larger than the layer 4. And the coercive force of the layer 7 is set larger than that of the layer 5.

Description

【発明の詳細な説明】 本発明は多層の磁性層を有する磁気記録媒体に関するも
のである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium having multiple magnetic layers.

従来の磁気記録媒体、例えば単一のγ−Ｆｅ２Ｏ３−Ｃ
。Conventional magnetic recording media, e.g. a single γ-Fe2O3-C
.

被着磁気テープ（磁性粉末の比表面積２０１１１２／ｇ
程度）は抗磁力及び残留磁束密度とも大きく、全帯域に
わたって再生出力が大きくなるが逆にバイアスノイズも
大きくなるという欠点を有していた。Adhering magnetic tape (specific surface area of magnetic powder 201112/g
The coercive force and the residual magnetic flux density are large, and although the reproduced output becomes large over the entire band, the bias noise also becomes large.

そこで、この欠点を改善するために種々検討がなされ、
磁気テープの磁性層に比表面積の大きい磁性粉末を分布
させるとバイアスノイズが低減されることが判明した。Therefore, various studies have been made to improve this shortcoming.
It has been found that bias noise can be reduced by distributing magnetic powder with a large specific surface area in the magnetic layer of a magnetic tape.

しかし、磁性粉末の比表面積を大きくすると結合剤と分
散したときの分散性の劣化等によりバイアスノイズは低
減するものの、目的とする再生出力が９１すられないと
いう欠点がある。However, if the specific surface area of the magnetic powder is increased, bias noise is reduced due to deterioration of dispersibility when dispersed with a binder, etc., but there is a drawback that the intended reproduction output is not even 91.

本発明は、上述の点に鑑み全帯域で優れた再生出力及び
低雑音（バイアスノイズ）を有する磁気記録媒体を提供
するものである。In view of the above points, the present invention provides a magnetic recording medium having excellent reproduction output and low noise (bias noise) in all bands.

即ち、本発明は磁気記録媒体における磁性層をＣＯ被被
着酸酸化鉄磁性粉末びＣｒＯ２磁性粉末の少くとも一方
の磁性粉末の塗布により第１及び第２の磁性層を形成し
、この上に少くとも一層の磁性金属薄膜層を形成した多
層構造となし、第１及び第２の磁性層の磁性粉末の比表
面積、各磁性層の抗磁力Ｈｅ等を選定して構成し、全帯
域を高再生出力に保ちつつバイアスノイズを低減せしめ
るようにしたものである。That is, the present invention forms a magnetic layer in a magnetic recording medium by coating at least one of a CO-adhered oxidized iron oxide magnetic powder and a CrO2 magnetic powder to form the first and second magnetic layers, and then forms the first and second magnetic layers thereon. It has a multilayer structure with at least one magnetic metal thin film layer formed, and the specific surface area of the magnetic powder of the first and second magnetic layers, the coercive force He of each magnetic layer, etc. are selected to make the entire band high. This is designed to reduce bias noise while maintaining the reproduction output.

以下、実施例を参照しながら本発明による磁気記録媒体
を詳述する。Hereinafter, the magnetic recording medium according to the present invention will be described in detail with reference to Examples.

実施例 １、比表面積２０ｍ２／ｇ、抗磁力６２００ｅのｒ　−
ＦｅＯ３−Ｃ。Example 1, specific surface area 20 m2/g, coercive force 6200e r −
FeO3-C.

被着磁性粉末・・・・・・・・・・・・・４００重量部
熱可塑性ポリウレタン樹脂・・・・・　５０重量部（ニ
スタン５７０２　　Ｂ、Ｆ、グツドリッチ社製）塩化ビ
ニル−酢酸ビニル共重合体・・・　５０重量部（ＶＡＧ
ＨＵ、Ｃ，Ｃ，社製） レシチン　・・・・・・・・・・・・・・・　４重量部
メチルエチルケトン　・・・・・・・・７００重葉部シ
クロヘキサノン　・・・・・・・・・　５０重量部上記
組成を加えボールミルにて２４時間の分散処理を施して
後、ポリイソシアネート（デスモジュールＬ−７５バイ
エル社製）を２０重量部加え２時間の高速剪断分散を行
い磁性塗料を得２、比表面積２０ｍ２／ｇ、抗磁力６２
００ｅのｒ　−Ｐｅ２０３−　Ｃ。Magnetic powder: 400 parts by weight Thermoplastic polyurethane resin: 50 parts by weight (Nistan 5702 B, F, manufactured by Gutdrich) Vinyl chloride-vinyl acetate copolymer Combining... 50 parts by weight (VAG
(manufactured by HU, C, C, Inc.) Lecithin 4 parts by weight Methyl ethyl ketone 700 parts by weight Cyclohexanone 4 parts by weight - After adding 50 parts by weight of the above composition and subjecting it to dispersion treatment in a ball mill for 24 hours, 20 parts by weight of polyisocyanate (Desmodur L-75 manufactured by Bayer AG) was added and high-speed shear dispersion was carried out for 2 hours to obtain a magnetic paint. 2. Specific surface area 20m2/g, coercive force 62
00e r-Pe203-C.

被着磁性粉末　、、、、、、、、、、、、　４００重量
部熱可塑性ポリウレタン樹脂、　、　、　、　、　３３
．３重世部塩化ビニル−酢酸ビニル共重合体、　、　、
　３３．３重量部レシチン　・・・・・・・・・・・・
・・・・　４重量部メチルエチルケトン　、、、、、、
、、６５０重量部シクロヘキサノン・・・・・・・・・
・・５０重量部上記組成を加え、以下第１実施例の磁性
塗料（Ａ）と同じ工程により磁性塗料を得た。これを磁
性塗料（Ｂ）とする。Magnetic powder 400 parts by weight Thermoplastic polyurethane resin 33
．． Triple polyvinyl chloride-vinyl acetate copolymer, , ,
33.3 parts by weight lecithin ・・・・・・・・・・・・
...4 parts by weight methyl ethyl ketone
,,650 parts by weight cyclohexanone...
...50 parts by weight of the above composition was added, and a magnetic paint was obtained by the same process as the magnetic paint (A) of the first example. This is referred to as magnetic paint (B).

３、比表面１２０ｍ２／ｇ、抗磁力６２００６のｒ　−
Ｆｅ２Ｏ３−Ｃ。3. Specific surface 120 m2/g, coercive force 62006 r −
Fe2O3-C.

被着磁性粉末　・・・・・・・・・・・・４００重量部
熱可塑性ポリウレタン樹脂、、、、、、２５ｍ１部塩化
ビニル−酢酸ビニル共重合体、　、　、　、　２５重量
部レシチン　、０．、、、、、、、、、、、、．４重量
部メチルエチルケトン　、、、、、、、、６２５重量部
シクロヘキサノン・・・・・・・・・・・５０重量部上
記組成を加え、以下第１実施例の磁性塗料（Ａ）と同じ
工程により磁性塗料を得た。これを磁性塗料（Ｃ）とす
る。Magnetic powder: 400 parts by weight Thermoplastic polyurethane resin, 25 ml 1 part Vinyl chloride-vinyl acetate copolymer, 25 parts by weight Lecithin, 0. ,,,,,,,,,,,,. 4 parts by weight Methyl ethyl ketone 625 parts by weight Cyclohexanone 50 parts by weight Add the above composition and follow the same process as the magnetic paint (A) of Example 1. A magnetic paint was obtained. This is called magnetic paint (C).

４、第１実施例の磁性塗料（Ａ）のｒ　−Ｆｅ　２０３
−　Ｃ。4. r-Fe 203 of the magnetic paint (A) of the first example
-C.

被着磁性粉末を比表面積３０ｍ２／ｇ、抗磁力６２００
ｅのγ−Ｆｅ　２０３−　Ｃｏ被着磁性粉末に置き換え
て（他は同じとして）磁性塗料（Ａ）と同じ工程により
磁性塗料を得た。これを磁性塗料（Ｄ）とする。The magnetic powder has a specific surface area of 30 m2/g and a coercive force of 6200.
A magnetic paint was obtained by the same process as the magnetic paint (A) except that the γ-Fe 203-Co magnetic powder of e was replaced (other things being the same). This is called a magnetic paint (D).

５、第３実施例の磁性塗料（Ｃ）のｒ　−Ｆｅ　２０３
−　Ｃ。5. r -Fe 203 of the magnetic paint (C) of the third example
-C.

被着磁性粉末を比表面積３０ｍ２／ｇ、抗磁力６２００
ｅのγ−Ｆｅ２Ｏ３−Ｃｏ被着磁性粉末に置き換えて（
他は同じとして）第１実施例の磁性塗料（Ａ）と同じ工
程により磁性塗料を得た。これを、磁性塗料（Ｅ）とす
る。The magnetic powder has a specific surface area of 30 m2/g and a coercive force of 6200.
By replacing e with γ-Fe2O3-Co magnetic powder (
A magnetic paint was obtained by the same process as the magnetic paint (A) of the first example (assuming that everything else was the same). This is called magnetic paint (E).

６、第１実施例の磁性塗料（Ａ）のｒ　−Ｆｅ２Ｏ３−
Ｃ。6. r -Fe2O3- of the magnetic paint (A) of the first example
C.

被着磁性粉末を比表面積４０ｍ２／ｇ、抗磁力６２００
ｅ及び８２００ｅのγ−Ｆｅ２Ｏ３−Ｃｏ被着磁性粉末
に置き換えて（他は同じとして）磁性塗料（Ａ）と同じ
工程により磁性塗料を得た。これを夫々（Ｆ）及び（Ｇ
）とする。The magnetic powder has a specific surface area of 40 m2/g and a coercive force of 6200.
A magnetic paint was obtained by the same process as the magnetic paint (A) except that the γ-Fe2O3-Co magnetized powder of e and 8200e was replaced (other things being the same). These are (F) and (G
).

７、比表面積２０ｍ２／ｇ、抗磁力６２００ｅのＣｒｏ
　２磁性粉末・・・・・・・・・・・・・・・・・・４
００重量部熱可塑性ポリウレタン樹脂　　　　　２５重
量部塩化ビニル−酢酸ビニル共重合体　　　　２５重量
部レシチン　　　　　　　　　　　　　４重量部メチル
エチルケトン　　　　　　　　６２５重量部シクロヘキ
サノン　　　　　　　　　　５０重量部上記組成を加え
、以下第１実施例の磁性塗料（Ａ）と同じ工程により磁
性塗料を得た。これを磁性塗料（Ｃ′）とする。7. Cro with specific surface area 20m2/g and coercive force 6200e
2 Magnetic powder・・・・・・・・・・・・・・・4
00 parts by weight Thermoplastic polyurethane resin 25 parts by weight Vinyl chloride-vinyl acetate copolymer 25 parts by weight Lecithin 4 parts by weight Methyl ethyl ketone 625 parts by weight Cyclohexanone 50 parts by weight The above composition was added, and the magnetic coating material (A) of Example 1 and the following were prepared. A magnetic paint was obtained by the same process. This is referred to as a magnetic paint (C').

上記磁性粉末の比表面積、抗磁力Ｈｅは出発原料の針状
酸化鉄磁性粉末の比表面積、軸比及び被着する化合物の
闇、熱処理温度等によってコントロールすることができ
る。また磁性粉末の比表面積はＢＥＴ法による比表面積
とする。The specific surface area and coercive force He of the above-mentioned magnetic powder can be controlled by the specific surface area and axial ratio of the acicular iron oxide magnetic powder as the starting material, the darkness of the compound to be deposited, the heat treatment temperature, etc. Further, the specific surface area of the magnetic powder is determined by the BET method.

上述の各磁性塗料（Ａ）〜（Ｇ）及び（Ｃ′）の特性を
まとめて下記の表に示す。但し”／Ｂは磁性粉末（Ｐ）
に対するバインダー（Ｂ）の比を示す。The properties of each of the above-mentioned magnetic paints (A) to (G) and (C') are summarized in the table below. However, "/B" is magnetic powder (P)
The ratio of binder (B) to

しかして、上記各実施例における各磁性塗料（Ａ）〜（
Ｆ）及び（Ｃ′）を使用し、第１図に示すように非磁性
基体（例えば厚さ１２μのポリエチレンテレフタレート
フィルム）（１）上に磁性塗料を塗布し、磁場配向処理
を行い、乾燥した後にスーパーカレンダーロール処理し
て単一の磁性層（２）を形成して成る磁気記録媒体（３
）を作製する。Therefore, each magnetic paint (A) to ((
Using F) and (C'), as shown in Figure 1, a magnetic paint was applied onto a non-magnetic substrate (for example, a 12μ thick polyethylene terephthalate film) (1), subjected to magnetic field orientation treatment, and dried. A magnetic recording medium (3) is formed by subsequent supercalender roll treatment to form a single magnetic layer (2).
).

また、同様の磁性塗料（Ｂ）〜（Ｆ）及び（Ｃ′）を用
いて第２図に示すように上記と同じ工程により硬化して
から同じ工程で異なる磁性塗料によって第２磁性層（５
）を形成して中間体（６）を作製した後、第３図に示す
ように第２磁性層（５）の表面に磁性金属薄膜層（力を
１層又は複数層形成して成る本発明に係る多層磁気記録
媒体（８）を作製する。Further, similar magnetic paints (B) to (F) and (C') are cured in the same process as above as shown in Figure 2, and then a second magnetic layer (5
) to produce the intermediate (6), as shown in FIG. A multilayer magnetic recording medium (8) is produced.

この多層磁気記録媒体（８）は例えば真空度１０−４〜
１０　　Ｔｏｒｒとなした真空容器内において、金属磁
性材料（例えばＣｏ１００％）を電子ビームにより加熱
蒸発させて、上記の中間体（６）の第２磁性層（５）に
対し入射角６５°で斜め蒸着して半均膜厚１ｏｏｏＸの
磁性金属薄膜層（力を形成することにより作製される。This multilayer magnetic recording medium (8) has a vacuum degree of, for example, 10-4 to
In a vacuum container with a pressure of 10 Torr, a metal magnetic material (for example, 100% Co) is heated and evaporated with an electron beam, and is diagonally applied at an incident angle of 65° to the second magnetic layer (5) of the intermediate (6). A magnetic metal thin film layer (prepared by forming a force) with a semi-uniform thickness of 100X by vapor deposition.

なお、非磁性支持体に直接金属コバル）　（１００％）
を上記工程により蒸着した場合の磁気特性は抗磁力ＨＣ
””　１００００ｅ、残留磁束密度Ｂｒ　＝　１０００
０ガウス、角型比Ｒｓ　＝　０．９であった。(Metal cobal directly on the non-magnetic support) (100%)
The magnetic properties when deposited by the above process are coercive force HC
"" 10000e, residual magnetic flux density Br = 1000
0 Gauss, and the squareness ratio Rs = 0.9.

以上のように作製した単層磁気記録媒体（３）及び多層
磁気記録媒体（８）の磁気特性（残留磁束密度Ｂｒ、抗
磁力Ｈｅ　）、杏生出力（ＭＯＬ）及びバイアスノイズ
等を測定した。その結果を第４図乃至第６図に示す。The magnetic properties (residual magnetic flux density Br, coercive force He), Kyori output (MOL), bias noise, etc. of the single-layer magnetic recording medium (3) and multilayer magnetic recording medium (8) produced as described above were measured. The results are shown in FIGS. 4 to 6.

第４図は各磁性塗料（Ａ）〜（Ｆ）及び（Ｃ′）による
単一磁性層（２）の磁気記録媒体（３）の特性（単層例
（１）〜（２つ）、第５図は本発明に係る多層（本例で
は３層）磁気記録媒体（８）の特性（実施例（１１〜（
９））、第６図は多層磁気記録媒体（８）における下層
の磁性層（４）の厚みｔｌ及び中層の磁性層（５）の厚
みｔ２を変えたときの特性（実施例００）−〇７）、（
５′）〜（８’）　）である。Figure 4 shows the characteristics (single layer examples (1) to (2), single layer examples (1) to (2), Figure 5 shows the characteristics of the multilayer (three layers in this example) magnetic recording medium (8) according to the present invention (Examples (11 to (11)).
9)), Figure 6 shows the characteristics (Example 00) when the thickness tl of the lower magnetic layer (4) and the thickness t2 of the middle magnetic layer (5) in the multilayer magnetic recording medium (8) are changed. 7), (
5') to (8')).

なお、測定に使用した磁気記録媒体（磁気テープ）は１
ｚ８インチ巾に裁断したオーディオ用テープである。ま
た、各特性の測定法は下記の通りである。The magnetic recording medium (magnetic tape) used for the measurement was 1
This is an audio tape cut to 8 inches wide. Moreover, the measurement method of each characteristic is as follows.

１、　　Ｂｒは外部磁場２００００ｅで測定した時の残
留磁束密度である。単位はガウス（ｇａｕｓｓ　）。1. Br is the residual magnetic flux density when measured with an external magnetic field of 20000e. The unit is gauss.

２、Ｈｃは外部磁場２００００ｅで測定した時の抗磁力
である。単位はエルステッド（Ｏｅ）。2. Hc is the coercive force when measured with an external magnetic field of 20,000e. The unit is Oersted (Oe).

３、ＭＯＬ（再生出力）は基準周波数（３１５Ｈｚ）と
高域周波数（１０ＫＨｚ　）が用いられ、前者は３１５
Ｈｚの出力信号が３９６ひずみとなる出力レベル、後者
は１０　ＫＩ４ｚ信号の最大飽和出力レベルである。3. For MOL (reproduction output), the reference frequency (315Hz) and high frequency (10KHz) are used, and the former is 315Hz.
The output level at which the Hz output signal has 396 distortion, the latter being the maximum saturation output level of the 10 KI4z signal.

４、バイアスノイズは聴感補正フィルターＡ（ＪＩ’Ｓ
）を使用した時のバイアスノイズである。単位はデシベ
ル（ｄｂ　）。4. For bias noise, use auditory correction filter A (JI'S
) is the bias noise when using. The unit is decibel (db).

５、　テープスピードは４．８”／ｓｅｃである。5. Tape speed is 4.8”/sec.

そしてＭＯＬ　（３１５Ｉ−１ｚ　、　　ｌ０ＫＩ］ｚ
　）及びバイアスノイズは第４図の単層例（１）を基準
（Ｏｄｂ）とした相対値（ｄｂ）で示す。and MOL (315I-1z, l0KI]z
) and bias noise are shown as relative values (db) with the single layer example (1) in FIG. 4 as the reference (Odb).

この第４図乃至第６図から中層の第２磁性層（５）の磁
性粉末の比表面積及び抗磁力を下層側の第１磁性層（４
）のそれより夫々大となし、さらに中層の上に磁性金属
薄膜層を形成した多層磁気記録媒体（８）が単層磁気記
録媒体（３）に比べて低バイアスノイズで且つ低域及び
高域の全帯域にわたって高再生出力を有することが認め
られる。From FIGS. 4 to 6, the specific surface area and coercive force of the magnetic powder of the middle second magnetic layer (5) are calculated from the lower first magnetic layer (4).
), and the multilayer magnetic recording medium (8) in which a magnetic metal thin film layer is formed on the middle layer has lower bias noise and higher low and high frequencies than the single layer magnetic recording medium (3). It is recognized that it has high reproduction output over the entire band.

以上の構成において、第１磁性層（４）の磁性粉末の比
表面積は２０〜３０ｍ２／ｇの範囲がよく、これを外れ
ると低域の再生出力が低下し、第２磁性層（５）の磁性
粉末の比表面積は３０〜５０ｍ２／ｇの範囲がよく、こ
れを外れるとバイアスノイズが低減されないことになる
。なお、第１磁性層（４）の厚さｔｌは２．０μ以上６
．０μ以下がよく、２．０μより薄くなると低域の再生
出力が低下し、６．０μより厚くなると低域の再生出力
のみが上り過ぎ低高域のバランスが悪くなる。In the above configuration, the specific surface area of the magnetic powder of the first magnetic layer (4) is preferably in the range of 20 to 30 m2/g, and if it deviates from this range, the low frequency reproduction output will decrease, and the specific surface area of the magnetic powder of the second magnetic layer (5) will decrease. The specific surface area of the magnetic powder is preferably in the range of 30 to 50 m2/g, and if it is outside this range, bias noise will not be reduced. Note that the thickness tl of the first magnetic layer (4) is 2.0 μ or more 6
．． A value of 0μ or less is good; if it is thinner than 2.0μ, the reproduction output in the low range decreases, and if it is thicker than 6.0μ, only the reproduction output in the low frequency range increases too much, resulting in poor balance between low and high frequencies.

第２磁性層（５）の厚さｔ２は０．２〜２，０μの範囲
がよ（，０，２μより薄くなるとバイアスノイズが減ら
ず、２．０μより厚くなると低域の再生出力が低下する
。また、第１磁性層（４）の抗磁力Ｈｃｌ及び残留磁束
密度Ｂｒ１は夫々５００〜１０００エルステツド及び１
０００〜２３００ガウスがよく、Ｂｒ１についてはこの
範囲を外れると低域の出力が低下する。第２磁性層（５
）の抗磁力Ｈｃ２も５００〜１０００エルステツドが好
ましく、この範囲を外れると高域がのびない。The thickness t2 of the second magnetic layer (5) is preferably in the range of 0.2 to 2.0μ (if it is thinner than 0.2μ, bias noise will not be reduced, and if it is thicker than 2.0μ, the low-frequency reproduction output will decrease). In addition, the coercive force Hcl and residual magnetic flux density Br1 of the first magnetic layer (4) are 500 to 1000 oersted and 1000 oersted, respectively.
000 to 2300 Gauss is good, and when Br1 is out of this range, the low frequency output decreases. Second magnetic layer (5
) The coercive force Hc2 is also preferably 500 to 1000 oersted, and if it is out of this range, the high frequency range will not be extended.

一方磁性金属薄膜層（７）の抗磁力Ｈｃ３は第２磁性層
（５）の抗磁力Ｈｃ２に対してそれ以上とするのがよく
、なおこの磁性金属薄膜層（力の厚さｔ３は５００〜１
５００．ｊ、残留磁束密度Ｂｒ３　〉６０００ガウスが
好期して本発明に於ては、上記特性結果等に基き、第３
図に示すように、第１磁性層（４）はＢ　ＪＵ　Ｔ法に
よる比表面積Ａｌ２Ｏ〜３０ｍ２／ｇのＣｏ被看形酸化
鉄磁性粉末及びＣｒＯ２磁性粉末の少くとも一方の磁性
粉末を、また第２磁性層（５）はＢＥＴ法による比表面
積Ａ２３０〜５０ｍ２／ｇのＣＯ被被着酸酸化鉄磁性粉
末びＣｒＯ２磁性粉末の少くとも一方の磁性粉末を、夫
々比表面積Ａｒ　＜比表面＆Ａ２の関係において塗布し
て形成し、その第１磁）１１：層（４）の抗磁力ＨＣ１
と第２磁性層（５）の抗磁力ｌ−ＩＣ２をＩ（ｃｌ　（
１（ｃ２に選定し、さらに第２磁性層（４）上に少くと
も一層の磁性金属薄膜層を形成し、その抗磁力Ｈｃ　３
を第２磁性層の抗磁力Ｈｃ２以上に選定するものである
。On the other hand, the coercive force Hc3 of the magnetic metal thin film layer (7) is preferably greater than the coercive force Hc2 of the second magnetic layer (5). 1
500. j, residual magnetic flux density Br3 > 6000 Gauss, and in the present invention, based on the above characteristic results etc., the third
As shown in the figure, the first magnetic layer (4) contains at least one magnetic powder of Co-embedded iron oxide magnetic powder and CrO2 magnetic powder having a specific surface area of Al2O to 30 m2/g by the B JUT method. The second magnetic layer (5) is made of at least one of a CO-adhered iron oxide magnetic powder and a CrO2 magnetic powder having a specific surface area A of 230 to 50 m2/g by the BET method, and the relationship of specific surface area Ar < specific surface & A2. Coating and forming the first magnetic layer (11): Coercive force HC1 of layer (4)
and the coercive force l-IC2 of the second magnetic layer (5) as I(cl (
1 (c2), and furthermore, at least one magnetic metal thin film layer is formed on the second magnetic layer (4), and its coercive force Hc 3
is selected to be greater than the coercive force Hc2 of the second magnetic layer.

この様に構成される本発明によれば、全帯域にわたり高
再生出力を保ちつつバイアスノイズを低減させることが
できるものであり、従来の単層磁気記録媒体（例えばメ
タルチーブ等）に比して優れた磁気記録媒体を提供する
ことが出来る。According to the present invention configured in this way, it is possible to reduce bias noise while maintaining high reproduction output over the entire band, which is superior to conventional single-layer magnetic recording media (for example, metal chips, etc.). A magnetic recording medium can be provided.

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

第１図は従来の磁気記録媒体の断面図、第２図は本発明
による磁気記録媒体の作製工程中における第１．第２の
磁性層形成状態の中間体の断面図、第３図は本発明によ
る磁気記録媒体の断面図、第４図は単層磁気記録媒体の
各側の特性を人として示す図、第５図は本発明による多
層磁気記録媒体の各実施例の特性を表として示す図、第
６図は多層磁気記録媒体の下層及び中層の厚みと特性の
関係を表として示す図である。 図中（１）は非磁性基体、（４）は第１磁性層、（５）
は第２磁性層、ｃ力は磁性金属薄膜層である。 第１図 ） 第２図 第３図FIG. 1 is a cross-sectional view of a conventional magnetic recording medium, and FIG. 2 is a cross-sectional view of a magnetic recording medium according to the present invention. 3 is a sectional view of the intermediate body in a state where the second magnetic layer is formed; FIG. 3 is a sectional view of the magnetic recording medium according to the present invention; FIG. 4 is a diagram showing the characteristics of each side of the single-layer magnetic recording medium; The figure is a table showing the characteristics of each embodiment of the multilayer magnetic recording medium according to the present invention, and FIG. 6 is a table showing the relationship between the thickness of the lower layer and middle layer of the multilayer magnetic recording medium and the characteristics. In the figure, (1) is the non-magnetic substrate, (4) is the first magnetic layer, (5)
is the second magnetic layer, and c is the magnetic metal thin film layer. Figure 1) Figure 2 Figure 3

Claims (1)

【特許請求の範囲】[Claims] 非磁性体と、該基体上の第１の磁性層と、該第１の磁性
層上の第２の磁性層と、該第２の磁性層上の少くとも一
層の磁性金属薄膜層から成り、上記第１の磁性層はＢＥ
Ｔ法による比表面積Ａ１が２０〜３０ｍ２／ｇのＣＯ被
被着酸酸化鉄磁性粉末びＣｒＯ２磁性粉末の少くとも一
方の磁性粉末を塗布して形成され、上記第２の磁性層は
ＢＥＴ法による比表面積Ａ２が３０〜５０ｍ２／ｇのＣ
Ｏ被被着酸酸化鉄磁性粉末びＣｒＯ２磁性粉末の少くと
も一方を塗布して形成され、上記両磁性層の磁性粉末の
比表面積はＡＩ＜Ａ２であり、また抗磁力はＨｃｌ　（
Ｈｃ２の関係を有し、かつ上記磁性金属薄膜層の抗磁力
Ｈ’ｃ３は上記第２の磁性層の抗磁力Ｈｃ２以上である
ことを特徴とする磁気記録媒体。consisting of a non-magnetic material, a first magnetic layer on the base, a second magnetic layer on the first magnetic layer, and at least one magnetic metal thin film layer on the second magnetic layer, The first magnetic layer is BE
The second magnetic layer is formed by coating at least one of a CO-adhered acidic iron oxide magnetic powder and a CrO2 magnetic powder having a specific surface area A1 of 20 to 30 m2/g by the T method, and the second magnetic layer is formed by the BET method. C with a specific surface area A2 of 30 to 50 m2/g
It is formed by coating at least one of an iron oxide magnetic powder and a CrO2 magnetic powder to which O is deposited, and the specific surface area of the magnetic powder of both magnetic layers satisfies AI<A2, and the coercive force is Hcl (
A magnetic recording medium having a relationship Hc2, and wherein the coercive force H'c3 of the magnetic metal thin film layer is greater than or equal to the coercive force Hc2 of the second magnetic layer.