JPH0312371B2 - - Google Patents
Info
- Publication number
- JPH0312371B2 JPH0312371B2 JP56085061A JP8506181A JPH0312371B2 JP H0312371 B2 JPH0312371 B2 JP H0312371B2 JP 56085061 A JP56085061 A JP 56085061A JP 8506181 A JP8506181 A JP 8506181A JP H0312371 B2 JPH0312371 B2 JP H0312371B2
- Authority
- JP
- Japan
- Prior art keywords
- magnetic
- magnetic layer
- layer
- powder
- recording
- 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.)
- Expired - Lifetime
Links
- 239000006247 magnetic powder Substances 0.000 claims description 21
- 229910017052 cobalt Inorganic materials 0.000 claims description 7
- 239000010941 cobalt Substances 0.000 claims description 7
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 6
- 239000000758 substrate Substances 0.000 claims description 5
- 239000010410 layer Substances 0.000 description 34
- 239000003973 paint Substances 0.000 description 7
- 239000011248 coating agent Substances 0.000 description 6
- 238000000576 coating method Methods 0.000 description 6
- 230000005415 magnetization Effects 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 230000004907 flux Effects 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 229910001566 austenite Inorganic materials 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229920000728 polyester Polymers 0.000 description 2
- TWJNQYPJQDRXPH-UHFFFAOYSA-N 2-cyanobenzohydrazide Chemical compound NNC(=O)C1=CC=CC=C1C#N TWJNQYPJQDRXPH-UHFFFAOYSA-N 0.000 description 1
- TUNFSRHWOTWDNC-UHFFFAOYSA-N Myristic acid Natural products CCCCCCCCCCCCCC(O)=O TUNFSRHWOTWDNC-UHFFFAOYSA-N 0.000 description 1
- 235000021360 Myristic acid Nutrition 0.000 description 1
- 239000000020 Nitrocellulose Substances 0.000 description 1
- 229920006311 Urethane elastomer Polymers 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- ULBTUVJTXULMLP-UHFFFAOYSA-N butyl octadecanoate Chemical compound CCCCCCCCCCCCCCCCCC(=O)OCCCC ULBTUVJTXULMLP-UHFFFAOYSA-N 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 150000001868 cobalt Chemical class 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000012948 isocyanate Substances 0.000 description 1
- -1 isocyanate compound Chemical class 0.000 description 1
- 239000006249 magnetic particle Substances 0.000 description 1
- 229920001220 nitrocellulos Polymers 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229910000889 permalloy Inorganic materials 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 229920006267 polyester film Polymers 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- XOOUIPVCVHRTMJ-UHFFFAOYSA-L zinc stearate Chemical compound [Zn+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O XOOUIPVCVHRTMJ-UHFFFAOYSA-L 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
- G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
- G11B5/716—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by two or more magnetic layers
Landscapes
- Magnetic Record Carriers (AREA)
- Paints Or Removers (AREA)
Description
この発明は磁気記録媒体に関し、さらに詳しく
は、磁性粉末の垂直成分を利用する高密度記録に
適した磁気記録媒体に関するものである。
一般に、磁気テープなどの磁気記録媒体は、磁
性層中の針状磁性粉末を磁性層の水平方向に配向
させるなどして磁気特性を向上させているが、こ
のように針状磁性粉末を水平方向に配向させたも
のでは記録密度の向に限度があり、磁気記録の高
密度化に充分に対応することができない。
このため、磁気記録の高密度化に充分に対応で
きるものとして、近年、スパツタ蒸着膜を用いた
垂直磁気記録方式が研究されており、たとえば、
基体上にパーマロイなどの高透磁率材料からなる
保磁力の非常に小さな磁性層を設け、さらにその
上に垂直方向に磁化容易軸を有する保磁力の大き
な磁性層を設けた垂直磁気記録用磁気記録媒体な
どが提案されている。
ところが、この種の垂直磁気記録用磁気記録媒
体は、波長0.1〜0.5ミクロンといつた高密度記録
に優れる反面、特殊ヘツドを用いなければならな
い。またアナログ記録を考えるならば長波長の低
周波領域の出力は期待できないという難点があ
り、この種の磁気記録媒体はむしろ、PCMのよ
うなデジタル分野に適した記録方式といえよう。
また、塗布型磁気テープで高記録密度を達成す
るために磁性層の磁性粉末の粒子配向を水平配向
ではなく、無配向とし、その垂直成分を短波長記
録のために有効利用をするという研究もなされて
おり、この場合、ギヤツプ長0.2ミクロンの短い
ヘツドが用いられる。ところが、この種の磁気記
録媒体も短波長記録には適しているものの長波長
の低周波領域の出力は、長手方向に配向されたテ
ープに比べて出力が出ないという欠点がある。
この発明者はかかる問題を克服するため種々検
討を行なつた結果、基体上に保磁力が350エルス
テツド以上の磁性粉末を角型で0.70以上となるよ
うに配向させて磁性粉末を基体に対し水平方向を
主体に配向させた第１の磁性層を形成し、さらに
その上に保磁力が650エルステツド以上の粒状の
コバルトエピタキシヤル磁性粉末を垂直方向の角
型で0.65以上となるようにした第２の磁性層を形
成し、しかも塗膜全厚を６ミクロン以下とし、第
２の磁性層の厚みが塗膜全厚の30％以下となるよ
うな塗膜を形成すると、このように２層に形成さ
れた磁性層を磁化する際、下層の第１の磁性層は
長波長の磁束が通り易くなり、大きな出力が期待
される。またその磁束が塗膜表面に出る際には上
層の第２の磁性層の垂直方向成分を通過し、表面
磁束の形態としては、理想的な磁力線分布を示
す。また、短波長記録に関しては、磁束は表面層
のみを通過するため第１層の水平方向成分の寄与
はごく僅かで十分である。その結果、従来の垂直
磁気記録用磁気記録媒体のように上層の磁性層に
残留磁化がなくて出力に影響を及ぼすということ
もなく、高密度記録に優れるとともに出力が充分
に向上された磁気記録媒体が得られることを見い
だし、この発明をなすに至つた。
この発明において下層となる第１の磁性層は、
その直上に形成される第２の磁性層の垂直磁化を
良好にするため磁性粉末を角型で0.70以上となる
ように垂直方向に配向させるのが好ましく、角型
が0.75以上となるように配向するのがより好まし
い。
また、上層となる第２の磁性層は高密度記録に
適した垂直磁化が良好に行なえるようにするた
め、たとえば、コバルトエピタキシヤル粒状粉末
を用いることにより配向に関係なく塗膜垂直方向
でも角型で0.7以上を得ることができる。本発明
で使用される粒状の磁性粉末としては、長軸と短
軸の比（軸比）が３：１〜１：１のコバルトエピ
タキシヤル磁性粉末が好適に使用される。このコ
バルトエピタキシヤル磁性粉末を使用する場合
は、塗布直後に垂直方向に磁場をかけることによ
り、垂直方向の角型を0.6以上となるように配向
させるのが好ましい。
第１の磁性層の形成は、ポリエステルフイルム
などの基体上に磁性粉末、バインダー、有機溶剤
およびその他の添加剤を含む磁性塗料を通常の手
段により塗布し、磁性粉末が基体に対し水平方向
に配向するように周知の対抗磁場を使用して配向
処理し、乾燥して形成すればよい。また、第２の
磁性層を形成する場合の配向処理としては棒磁
石、馬てい形磁石などを使用し、ベースフイルム
に対し垂直方向の磁界によつて垂直方向に磁性粒
子を配向する方法などが適用される。なお、粒状
磁性粉末の場合は配向の必要はない。この第２層
を形成する際、磁性塗料を塗布する場合に使用す
る磁性粉末は前述したように粒状のコバルトエピ
タキシヤル磁性粉末が好ましく使用され、具体例
としては、粒状のCo含有γ−Fe2O3粉末、粒状の
Co含有Fe3O4粉末などのコバルトエピタキシヤル
磁性粉末がいずれも好適なものとして使用され
る。
次に、この発明の実施例について説明する。
実施例
Co含有γ−Fe2O3磁性粉末（保磁力360エルステ
ツド、軸比約７：１の針状粉） 100重量部
粒状α−Fe2O3粉末 ４ 〃
カーボンブラツク ５ 〃
ステアリン酸亜鉛 0.5 〃
ニトロセルロース 10 〃
エスタン5702（米国グツドリツチケミカル社製、
ウレタンエラストマー） ９ 〃
コロネートＬ（日本ポリウレタン社製、イソシア
ネート化合物） 3.4 〃
ステアリン酸−ｎ−ブチル 0.8 〃
ミリスチン酸 0.5 〃
シクロヘキサノン 100 〃
トルエン 100重量部
この組成物をボールミルで50時間混合分散させ
て磁性塗料を調製し、この磁性塗料を9.5μのポリ
エステルベースフイルム上に塗布し、ベースフイ
ルム面に対し、表裏両面に配置された一対の棒磁
石によつてベースフイルムの長手方向に2000ガウ
スの対向磁場を加えて配向処理を施こし、乾燥し
て乾燥厚が4μの下層となる第１の磁性層を形成
した。ついでこの上に前記第１層を形成した磁性
塗料組成において磁性粉末として保磁力800エル
ステツド、軸比１：１の粒状Co含有γ−Fe2O3磁
性粉末120重量部を使用して調製した磁性塗料を
配向磁石を用いずに塗布し、乾燥後塗布厚が1μ
の上層となる第２の磁性層を重層形成し所定の幅
に裁断して磁気テープをつくつた。得られた磁気
テープの磁性層の保磁力は全体で450エルステツ
ドで、下層の第１の磁性層の水平方向の角型は
0.81、上層の第２の磁性層の角型は0.7であつた。
比較例
厚さ9.5μのポリエステルベースフイルムに前述
の実施例の第１の磁性層を形成するのに使用した
のと同一の塗料を乾燥後の塗布厚み5μとなるよ
うに塗布した。塗布時の配向磁場は2000ガウスと
した。
実施例および比較例で得られた磁気テープにつ
いて、テープ上での波長50μおよび2μでの再生出
力を測定し、比較例で得られた磁気テープの再生
出力を0dBとしてこれとの比較値で表わした。
下表はその結果である。
The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium suitable for high-density recording that utilizes the perpendicular component of magnetic powder. Generally, the magnetic properties of magnetic recording media such as magnetic tapes are improved by orienting the acicular magnetic powder in the magnetic layer in the horizontal direction of the magnetic layer. If the magnetic recording material is oriented in this direction, there is a limit to the direction of recording density, and it cannot sufficiently respond to the increase in the density of magnetic recording. For this reason, in recent years, perpendicular magnetic recording methods using sputter-deposited films have been studied as a method that can sufficiently respond to higher density magnetic recording.
Magnetic recording for perpendicular magnetic recording in which a magnetic layer with a very low coercive force made of a high magnetic permeability material such as permalloy is provided on a substrate, and a magnetic layer with a large coercive force having an axis of easy magnetization in the perpendicular direction is further provided on top of the magnetic layer. Various media have been proposed. However, although this type of magnetic recording medium for perpendicular magnetic recording is excellent in high-density recording at a wavelength of 0.1 to 0.5 microns, it requires the use of a special head. Furthermore, when considering analog recording, there is a drawback in that output in the long wavelength and low frequency range cannot be expected, so this type of magnetic recording medium can be said to be a recording method suitable for digital fields such as PCM. In addition, in order to achieve high recording density in coated magnetic tapes, research is being conducted on making the grain orientation of the magnetic powder in the magnetic layer non-oriented instead of horizontal, and effectively using the vertical component for short wavelength recording. In this case, a short head with a gap length of 0.2 microns is used. However, although this type of magnetic recording medium is suitable for short wavelength recording, it has the disadvantage that it outputs less output in the long wavelength and low frequency region than a tape oriented in the longitudinal direction. As a result of various studies to overcome this problem, the inventor has oriented magnetic powder with a coercive force of 350 oersted or more on a substrate in a rectangular shape with a coercive force of 0.70 or more. A first magnetic layer is formed which is mainly oriented in the direction of the magnetic field, and a second magnetic layer is formed on the first magnetic layer, in which granular cobalt epitaxial magnetic powder having a coercive force of 650 oersted or more is formed in a rectangular shape in the vertical direction to have a coercive force of 0.65 or more. If you form a magnetic layer with a total thickness of 6 microns or less, and the thickness of the second magnetic layer is 30% or less of the total thickness of the coating, it will form two layers like this. When the formed magnetic layer is magnetized, long-wavelength magnetic flux easily passes through the lower first magnetic layer, and a large output is expected. Further, when the magnetic flux exits to the surface of the coating film, it passes through the vertical component of the upper second magnetic layer, and the form of the surface magnetic flux exhibits an ideal distribution of lines of magnetic force. Furthermore, for short wavelength recording, since the magnetic flux passes only through the surface layer, a very small contribution from the horizontal component of the first layer is sufficient. As a result, unlike conventional magnetic recording media for perpendicular magnetic recording, there is no residual magnetization in the upper magnetic layer, which does not affect the output, resulting in magnetic recording that is superior in high-density recording and has sufficiently improved output. They discovered that a medium could be obtained and came up with this invention. In this invention, the first magnetic layer serving as the lower layer is:
In order to improve the perpendicular magnetization of the second magnetic layer formed directly above the magnetic powder, it is preferable to orient the magnetic powder in the perpendicular direction so that the square shape has a magnetization of 0.70 or more. It is more preferable to do so. In addition, in order to achieve good perpendicular magnetization suitable for high-density recording, the second upper magnetic layer is made of, for example, cobalt epitaxial granular powder, which is angular even in the direction perpendicular to the coating film, regardless of orientation. You can get 0.7 or more with type. As the granular magnetic powder used in the present invention, cobalt epitaxial magnetic powder having a long axis to short axis ratio (axial ratio) of 3:1 to 1:1 is preferably used. When using this cobalt epitaxial magnetic powder, it is preferable to apply a magnetic field in the vertical direction immediately after application to orient the square shape in the vertical direction to 0.6 or more. The first magnetic layer is formed by applying a magnetic paint containing magnetic powder, a binder, an organic solvent, and other additives onto a substrate such as a polyester film by a conventional method, and then aligning the magnetic powder horizontally with respect to the substrate. It may be formed by performing orientation treatment using a well-known countermagnetic field and drying. In addition, for the orientation treatment when forming the second magnetic layer, there is a method of using a bar magnet, a horse-shaped magnet, etc., and orienting the magnetic particles in the perpendicular direction with a magnetic field perpendicular to the base film. Applicable. Note that orientation is not necessary in the case of granular magnetic powder. When forming this second layer, as described above, granular cobalt epitaxial magnetic powder is preferably used as the magnetic powder used when applying the magnetic paint, and a specific example is granular Co-containing γ-Fe 2 O3 powder, granular
Any cobalt epitaxial magnetic powder such as Co-containing Fe 3 O 4 powder is preferably used. Next, embodiments of the invention will be described. Example Co-containing γ-Fe 2 O 3 magnetic powder (acicular powder with coercive force of 360 oersted and axial ratio of about 7:1) 100 parts by weight granular α-Fe 2 O 3 powder 4 Carbon black 5 Zinc stearate 0.5 〃 Nitrocellulose 10 〃 Estan 5702 (manufactured by Gutsudoritsuchi Chemical Company, USA)
(urethane elastomer) 9 Coronate L (manufactured by Nippon Polyurethane Co., Ltd., isocyanate compound) 3.4 n-butyl stearate 0.8 myristic acid 0.5 cyclohexanone 100 toluene 100 parts by weight This composition was mixed and dispersed in a ball mill for 50 hours to make it magnetic. A paint is prepared, this magnetic paint is applied onto a 9.5μ polyester base film, and a 2000 Gauss opposing magnetic field is applied to the base film in the longitudinal direction of the base film using a pair of bar magnets placed on both the front and back sides. was added to perform orientation treatment, and dried to form a first magnetic layer serving as the lower layer with a dry thickness of 4 μm. Next, in the magnetic paint composition on which the first layer was formed, a magnetic powder was prepared using 120 parts by weight of granular Co-containing γ-Fe 2 O 3 magnetic powder with a coercive force of 800 oersted and an axial ratio of 1:1. The paint is applied without using an orientation magnet, and the coating thickness after drying is 1μ.
A second magnetic layer serving as an upper layer was layered and cut into a predetermined width to produce a magnetic tape. The total coercive force of the magnetic layers of the obtained magnetic tape was 450 oersted, and the horizontal square shape of the lower first magnetic layer was
The squareness of the upper second magnetic layer was 0.81, and the squareness of the upper second magnetic layer was 0.7. Comparative Example A polyester base film having a thickness of 9.5 .mu.m was coated with the same paint used to form the first magnetic layer in the above-mentioned example so that the coating thickness after drying was 5 .mu.m. The orientation magnetic field during coating was 2000 Gauss. For the magnetic tapes obtained in the Examples and Comparative Examples, the playback output on the tape at wavelengths of 50 μ and 2 μ was measured, and the playback output of the magnetic tape obtained in the Comparative Example was set as 0 dB and expressed as a comparison value. Ta. The table below shows the results.
【表】
上表から明らかなように、この発明で得られた
磁気テープ（実施例）は従来の磁気テープ（比較
例）に比し短波長域の再生出力が高く、このこと
からこの発明によれば高密度記録に優れるととも
に出力が充分に向上された磁気記録媒体が得られ
るのがわかる。[Table] As is clear from the above table, the magnetic tape obtained by this invention (Example) has a higher reproduction output in the short wavelength range than the conventional magnetic tape (Comparative example), and from this, the present invention It can be seen that a magnetic recording medium with excellent high-density recording and sufficiently improved output can be obtained.
Claims (1)
性粉末を磁性層の水平方向に角型で0.70以上とな
るように配向させた第１の磁性層を形成し、さら
にその上に保磁力が650エルステツド以上で長軸
と短軸との比が３：１〜１：１の粒状のコバルト
エピタキシヤル磁性粉末を磁性層の垂直方向に角
型で0.65以上となるように配向させた第２の磁性
層を重層形成したことを特徴とする磁気記録媒
体。1 A first magnetic layer is formed on the substrate in which magnetic powder with a coercive force of 350 Oe or more is oriented in a square shape in the horizontal direction of the magnetic layer, and a coercive force of 650 Oe or more is formed on the first magnetic layer. The second magnetic layer is made of granular cobalt epitaxial magnetic powder having a long axis to short axis ratio of 3:1 to 1:1 and oriented in a rectangular shape perpendicular to the magnetic layer so as to have a ratio of 0.65 or more. A magnetic recording medium characterized by forming a multilayer structure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56085061A JPS57200936A (en) | 1981-06-03 | 1981-06-03 | Magnetic recording medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56085061A JPS57200936A (en) | 1981-06-03 | 1981-06-03 | Magnetic recording medium |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS57200936A JPS57200936A (en) | 1982-12-09 |
| JPH0312371B2 true JPH0312371B2 (en) | 1991-02-20 |
Family
ID=13848116
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP56085061A Granted JPS57200936A (en) | 1981-06-03 | 1981-06-03 | Magnetic recording medium |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS57200936A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5360204A (en) * | 1976-11-10 | 1978-05-30 | Mitsubishi Heavy Ind Ltd | Magnetic recording medium and its recording method |
| JPS5567940A (en) * | 1978-11-13 | 1980-05-22 | Hitachi Ltd | Magnetic recording medium and its manufacture |
-
1981
- 1981-06-03 JP JP56085061A patent/JPS57200936A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5360204A (en) * | 1976-11-10 | 1978-05-30 | Mitsubishi Heavy Ind Ltd | Magnetic recording medium and its recording method |
| JPS5567940A (en) * | 1978-11-13 | 1980-05-22 | Hitachi Ltd | Magnetic recording medium and its manufacture |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57200936A (en) | 1982-12-09 |
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