【発明の詳細な説明】[Detailed description of the invention]
産業上の利用分野
本発明は蒸着法によつて製造された磁気記録媒
体に関するものである。
従来例の構成とその問題点
蒸着法による磁気記録媒体の製造法については
種々の研究が行われてきたが、最近特に注目され
ている製造法はCo系合金を酸素雰囲気中で冷却
されたキヤンに沿つて蒸着する方法である。薄膜
型磁気記録媒体では高い保持力Hcを得る方法が
問題となるが、古くから知られていた斜方蒸着法
は形状磁気異方性効果によつて保持力Hcを得て
いた。これに対しCo系合金を酸素中で蒸着する
方法では形状磁気異方性効果に加えて、Coのhcp
構造による結晶磁気異方性効果と、酸素導入によ
る飽和磁束密度Bs低下による保持力Hcの上昇効
果等により容易に保持力Hcを得ることができる。
古くから知られる斜方蒸着法では700O″e程度の
保持力を得る為には入射角は70°程度必要であつ
たが、Co系合金を酸素雰囲気中で蒸着する場合
の最低入射角は40゜程度で十分であり、蒸着効率
及び生産性は大幅に改善された。
磁気特性という面ではCo系合金を酸素雰囲気
中で蒸着する方法は十分に工業的なレベルに達し
ているが、磁気記録媒体として実用化されるには
種々な面での実用的特性を満たす必要がある。磁
気記録媒体として実用上必要とされる特性は使用
する磁気記録装置との問題で種々変化するが、耐
蝕性は磁気記録装置によらず磁気記録媒体には不
可欠な要件である。Co系合金を酸素雰囲気中で
蒸着する場合、耐蝕性に大きな影響を与えるの
は、薄膜の厚さ方向に対する酸素を成分比の分布
である。即ち蒸着膜の表面層に酸素を多く含む蒸
着膜は、蒸着膜中に均一に酸素を含む蒸着膜や蒸
着膜内部に酸素を多く含む蒸着膜や基板との界面
に酸素を多く含む蒸着膜より耐蝕性に秀れてい
る。表面層に酸素を多く含む蒸着膜を表面層から
深さ方向に対してエツチングしたオージエ分光法
による測定結果を従来例として第１図に示す。こ
のような蒸着膜中の酸素濃度分布は蒸着近傍での
酸素導入位置や酸素導入方法によつていある程度
変化させることが出来、連続蒸着の蒸着後端側に
酸素を導入することにより耐蝕性の秀れた蒸着膜
を作ることができる。このように酸素導入位置に
より蒸着膜の耐蝕性を改善することはできるが、
耐蝕性は磁気記録装置では殆んど補うことのでき
ない特性であり、磁気記録媒体の最も重要な特性
の一つである。磁気記録媒体は様々な環境下で使
用され、酸素導入位置の変化による耐蝕性の向上
だけでは極めて厳しい環境下では必ずしも十分で
はない。その為、Co系合金の酸素雰囲気中蒸着
膜の耐蝕性をさらに改善する必要があつた。
発明の目的
本発明はCo系合金の酸素雰囲気中蒸着膜の耐
蝕性を大幅に向上させ、劣悪な環境下での耐蝕性
を向上させ、磁気記録媒体としての実用特性を向
上させることを目的とするものである。
発明の構成
本発明の磁気記録媒体はCo系合金と酸素より
なる磁気薄膜を有し、前記薄膜の厚み方向に対
し、磁気薄膜の表面部に最も酸素の多い部分を有
し、且つ、前記薄膜の表面部と前記基板と接触す
る面との間に酸素の成分比が高くなる部分を有す
ることを特徴とする。
実施例の説明
本発明に係る酸素雰囲気中で形成した蒸着膜の
深さ方向の成分分布を第２図に示す。第２図は蒸
着膜を表面層から深さ方向に対してエツチングし
たオージエ分光法による測定結果である。第２図
から明らかなように蒸着膜の表面側には非常に高
い酸素濃度のピークが見られるが、内部にも２つ
目の酸素濃度のピークが見られる。
なお、さらに基板側で酸素濃度の上昇は、基板
に用いたポリエステルフイルムに含まれる酸素で
ある。
次に、本発明の実施例のCo系合金の酸素雰囲
気中蒸着膜の典型的な製造方法を第３図に示す。
Co系合金は蒸着源１から蒸発し、冷却キヤン３
上で連続的に蒸着される。この際酸素導入は蒸着
後端側２から導入される。ここで本発明の実施例
の蒸着膜の製造における特徴は加熱源７を用いる
ことである。従来の真空蒸着法の常識は蒸着源か
らの熱負荷を低減し、時に高分子基板を用いる場
合には基板のダメージを低減することに努力が払
われた。Co系合金の酸素雰囲気中蒸着の場合に
は、(1)蒸着母合金のCoが高融点金属であり熱輻
射が非常に大きく、(2)磁気記録媒体の中でも磁気
テープに最も適しているので、ポリエステルフイ
ルム等耐熱性の低い高分子材料を基板とすること
が多いという２つの理由から特に熱負荷を低減す
ることに努力が払われた。本実施例においては熱
負荷を増大させることによつてCoと酸素が反応
しない状態を作り出し、熱負荷の効果がない場合
は第１図のように深さ方向に単調な酸素濃度を持
つが、熱負荷の効果により蒸着時に酸素が存在し
ても蒸着膜中に酸素があまり取り込まれない領域
が出来、第２図のように蒸着膜の厚み方向に対し
酸素濃度分布は表面部と内部の２つのピークを持
つことを可能ならしめる。
実施例 １
直径500mmの水冷されたキヤンを用いてCo（重
量比65％）Ni（重量比10％）Cr（重量比25％）の
真空蒸着を行つた。基板には幅150mm厚み15μｍ
の芳香族ポリイミドフイルムを用い、最低入射角
50゜、走行速度５ｍ／minで1200Åの膜厚に蒸着
した。真空槽１×10-5Torrまで排気後、蒸着後
端側より200c.c.／minの酸素を導入し、サンプル
Ａを得た。次にサンプルＡと同じ条件で蒸発源側
にMoのヒーターを置き、10V、200A、の電流を
流し加熱しながら蒸着を行い、サンプルＢを得
た。サンプルＡ、ＢのＢ―Ｈ特性及び、温度60
℃、湿度90％で１カ月放置後のBsδ、Hcの変化
を表１にまとめる。
INDUSTRIAL APPLICATION FIELD The present invention relates to a magnetic recording medium manufactured by a vapor deposition method. Structures of conventional examples and their problems Various studies have been conducted on methods of manufacturing magnetic recording media by vapor deposition, but a manufacturing method that has recently received particular attention is a method in which a Co-based alloy is cooled in an oxygen atmosphere. This method involves vapor deposition along the following lines. In thin-film magnetic recording media, the problem is how to obtain a high coercive force Hc, and the oblique evaporation method, which has been known for a long time, obtains a coercive force Hc by the effect of shape magnetic anisotropy. On the other hand, in the method of vapor depositing Co-based alloys in oxygen, in addition to the shape magnetic anisotropy effect, the h cp of Co
The coercive force Hc can be easily obtained due to the magnetocrystalline anisotropy effect due to the structure and the effect of increasing the coercive force Hc due to the decrease in the saturation magnetic flux density Bs due to the introduction of oxygen.
In the long-known oblique evaporation method, an incident angle of about 70° was required to obtain a holding force of about 700 O″e, but when depositing Co-based alloys in an oxygen atmosphere, the minimum incident angle is 40°. degree is sufficient, and the deposition efficiency and productivity have been greatly improved.In terms of magnetic properties, the method of depositing Co-based alloys in an oxygen atmosphere has reached a sufficiently industrial level, but magnetic recording In order to be put to practical use as a medium, it is necessary to satisfy various practical characteristics.The characteristics required for practical use as a magnetic recording medium vary depending on the magnetic recording device used, but corrosion resistance, is an essential requirement for magnetic recording media regardless of the magnetic recording device.When depositing a Co-based alloy in an oxygen atmosphere, the corrosion resistance is greatly influenced by the oxygen component ratio in the thickness direction of the thin film. In other words, a vapor-deposited film containing a lot of oxygen in the surface layer of the vapor-deposited film, a vapor-deposited film that contains oxygen uniformly in the vapor-deposited film, a vapor-deposited film that contains a large amount of oxygen inside the vapor-deposited film, and a vapor-deposited film that contains oxygen at the interface with the substrate. It has superior corrosion resistance than a vapor deposited film containing a large amount of oxygen.As a conventional example, the results of measurement by Auger spectroscopy are shown in FIG. The oxygen concentration distribution in such a deposited film can be changed to some extent by changing the oxygen introduction position near the deposition and the oxygen introduction method. Corrosion resistance can be improved by introducing oxygen at the rear end of continuous deposition. It is possible to create an excellent deposited film.In this way, the corrosion resistance of the deposited film can be improved by changing the position of oxygen introduction, but
Corrosion resistance is a property that can hardly be compensated for in magnetic recording devices, and is one of the most important properties of magnetic recording media. Magnetic recording media are used in various environments, and improving corrosion resistance by changing the oxygen introduction position alone is not necessarily sufficient in extremely harsh environments. Therefore, there was a need to further improve the corrosion resistance of Co-based alloy films deposited in an oxygen atmosphere. Purpose of the Invention The purpose of the present invention is to significantly improve the corrosion resistance of a Co-based alloy film deposited in an oxygen atmosphere, improve the corrosion resistance in a poor environment, and improve the practical characteristics as a magnetic recording medium. It is something to do. Composition of the Invention The magnetic recording medium of the present invention has a magnetic thin film made of a Co-based alloy and oxygen, and has the most oxygen-rich portion on the surface of the magnetic thin film in the thickness direction of the thin film, and It is characterized by having a portion where the oxygen component ratio is high between the surface portion of the substrate and the surface that contacts the substrate. Description of Examples FIG. 2 shows the component distribution in the depth direction of a deposited film formed in an oxygen atmosphere according to the present invention. FIG. 2 shows the measurement results by Auger spectroscopy in which the deposited film was etched from the surface layer in the depth direction. As is clear from FIG. 2, a very high oxygen concentration peak can be seen on the surface side of the deposited film, but a second oxygen concentration peak can also be seen inside. Furthermore, the increase in oxygen concentration on the substrate side is due to oxygen contained in the polyester film used as the substrate. Next, FIG. 3 shows a typical manufacturing method of a Co-based alloy film deposited in an oxygen atmosphere according to an embodiment of the present invention.
The Co-based alloy is evaporated from the evaporation source 1 and cooled in the cooling can 3.
continuously deposited on top. At this time, oxygen is introduced from the rear end side 2 of the vapor deposition. Here, a feature of the production of the vapor deposited film according to the embodiment of the present invention is that a heating source 7 is used. The conventional wisdom in vacuum deposition methods is to reduce the heat load from the deposition source, and sometimes when a polymer substrate is used, efforts are made to reduce damage to the substrate. In the case of vapor deposition of Co-based alloys in an oxygen atmosphere, (1) Co, the vapor-depositing base alloy, is a high melting point metal and has very large thermal radiation, and (2) it is most suitable for magnetic tapes among magnetic recording media. In particular, efforts have been made to reduce the heat load for the two reasons that substrates are often made of polymeric materials with low heat resistance, such as polyester films. In this example, by increasing the heat load, a state where Co and oxygen do not react is created, and if the heat load has no effect, the oxygen concentration will be monotonous in the depth direction as shown in Figure 1, but Due to the effect of heat load, even if oxygen is present during vapor deposition, there is a region where very little oxygen is incorporated into the vapor deposited film, and as shown in Figure 2, the oxygen concentration distribution in the thickness direction of the vapor deposited film is divided into two areas: the surface area and the internal area. This makes it possible to have two peaks. Example 1 Co (65% by weight), Ni (10% by weight), and Cr (25% by weight) were vacuum-deposited using a water-cooled can with a diameter of 500 mm. The board has a width of 150 mm and a thickness of 15 μm.
using an aromatic polyimide film with a minimum angle of incidence of
The film was deposited to a thickness of 1200 Å at an angle of 50° and a traveling speed of 5 m/min. After the vacuum chamber was evacuated to 1×10 -5 Torr, oxygen was introduced at 200 c.c./min from the rear end of the vapor deposition to obtain sample A. Next, a Mo heater was placed on the evaporation source side under the same conditions as Sample A, and evaporation was performed while heating with a current of 10 V and 200 A, to obtain Sample B. B-H characteristics of samples A and B and temperature 60
Table 1 summarizes the changes in Bsδ and Hc after being left for one month at ℃ and 90% humidity.
【表】
サンプルＡ、Ｂをオージエ分光法により分析し
たところ、サンプルＡは第１図の様に表面部のみ
に酸素濃度のピークが見られたのに対し、サンプ
ルＢは第２図の様に表面部と内部の２カ所に酸素
濃度のピークが見られた。
表１から明らかなように、サンプルＡ、サンプ
ルＢ共に初期的特性はBsδ、Brδ、Hc、Br／Bs
（Br：残留磁化、Hc：保持力、Bs：飽和磁束）
は共に殆んど同じであるが、温度60℃、湿度90％
で１カ月間放置後のBsδの変化はサンプルＡでは
6.1％であつたがサンプルＢでは1.9％であつた。
またHcの変化についてもサンプルＡでは30Oeで
あつたがサンプルＢでは10Oeしかなく、サンプ
ルＢはサンプルＡに較べ大幅に耐蝕性が改良され
ているのがわかる。
実施例 ２
直径500mmの水冷されたキヤンを用いてCo（重
量比80％）Ni（重量比20％）合金の真空蒸着を行
つた。基板には幅150mm厚み10μｍのポリエステ
ルフイルムを用い、最低入射角35゜、走行速度20
ｍ／minで1500Åの膜厚に蒸着した。蒸発源に第
４図ａに示すジルコニア製のルツボを用いて真空
槽を１×10-5Torrまで排気後、蒸着後端部より
200c.c.／min酸素を導入しサンプルＣを得た。次
にルツボを第４図ｂに示すジルコニア製のルツボ
に変更して同様の蒸着を行い、サンプルＤを得
た。サンプルＣ、ＤのＢ−Ｈ特性及び、60℃90％
１カ月放置後のBsδ、Hcの変化を表２にまとめ
る。[Table] When samples A and B were analyzed using Auger spectroscopy, sample A showed a peak in oxygen concentration only at the surface as shown in Figure 1, while sample B showed a peak in oxygen concentration as shown in Figure 2. Oxygen concentration peaks were seen at two locations: on the surface and inside. As is clear from Table 1, the initial characteristics of both sample A and sample B are Bsδ, Brδ, Hc, Br/Bs
(Br: residual magnetization, Hc: coercive force, Bs: saturation magnetic flux)
are almost the same, but the temperature is 60℃ and the humidity is 90%.
For sample A, the change in Bsδ after leaving it for one month is
It was 6.1%, but in sample B it was 1.9%.
Furthermore, regarding the change in Hc, sample A was 30 Oe, but sample B was only 10 Oe, indicating that sample B has significantly improved corrosion resistance compared to sample A. Example 2 A Co (80% by weight) and Ni (20% by weight) alloy was vacuum deposited using a water-cooled can with a diameter of 500 mm. A polyester film with a width of 150 mm and a thickness of 10 μm was used for the substrate, the minimum angle of incidence was 35°, and the running speed was 20°.
The film was deposited to a thickness of 1500 Å at a rate of m/min. Using the zirconia crucible shown in Figure 4a as the evaporation source, the vacuum chamber was evacuated to 1 x 10 -5 Torr, and then
Sample C was obtained by introducing oxygen at 200c.c./min. Next, the crucible was changed to a zirconia crucible shown in FIG. 4b, and the same vapor deposition was performed to obtain Sample D. B-H characteristics of samples C and D and 60℃90%
Table 2 summarizes the changes in Bsδ and Hc after being left for one month.
【表】
サンプルＣ、Ｄのオージエ分光法により分析し
たところ、サンプルＣは第１図の様に表面部のみ
に酸素濃度のピークが見られたのに対し、サンプ
ルＤは第２図の様に表面部と内部の２カ所に酸素
濃度のピークが見られた。表２から明らかなよう
に、サンプルＣ、サンプルＤ共に初期的特性は
Bsδ、Brδ、Hc、Br／Bs共に殆んど同じである
が、60℃90％１カ月放置後のBsδの変化はサンプ
ルＣでは5.0％であつたがサンプルＤでは1.5％と
大幅に改良されている。またHcの変化について
もサンプルＣでは20Oeであつたがサンプルでは
0Oe、しかなく、サンプルＤはサンプルＣに較べ
大幅に耐蝕性が改良されているのがわかる
発明の効果
上記実施例から明らかな様に本発明のCo系合
金の酸素雰囲気中蒸着膜は従来のCo係合金の酸
素雰囲気中蒸着膜に較べ、磁気的特性は変化が認
められず耐蝕性に関しては大幅に改良された。こ
のように耐蝕性が大幅に改良される理由は熱負荷
により深さ方向に対し複雑な構造をとり内部の酸
化物層により腐食をうける層であるCo係合金属
が酸素高濃度層により分割され、一気にCo係合
金属が腐蝕されるのを酸素高濃度層が防いでいる
ものと考えられる。なお、本発明による蒸着膜の
製法は熱負荷によつてCo係合金の金属層を作る
ものであるが、熱負荷としては実施例１の様に他
の熱源を用いてもよいし、実施例２の様に蒸発源
近傍からの放熱を用いてもよい。[Table] When samples C and D were analyzed by Augier spectroscopy, the peak of oxygen concentration was observed only in the surface area of sample C, as shown in Figure 1, while the peak of oxygen concentration was observed in sample D, as shown in Figure 2. Oxygen concentration peaks were seen at two locations: on the surface and inside. As is clear from Table 2, the initial characteristics of both sample C and sample D are
Bsδ, Brδ, Hc, and Br/Bs are almost the same, but the change in Bsδ after being left at 60°C at 90% for one month was 5.0% for sample C, but was significantly improved to 1.5% for sample D. ing. Also, regarding the change in Hc, sample C was 20 Oe, but sample C was 20 Oe.
The effect of the invention is that the corrosion resistance of sample D is significantly improved compared to sample C.As is clear from the above examples, the coating of the Co-based alloy of the present invention deposited in an oxygen atmosphere is different from that of the conventional one. Compared to a Co-based alloy film deposited in an oxygen atmosphere, no change in magnetic properties was observed and corrosion resistance was significantly improved. The reason why the corrosion resistance is greatly improved is that the Co-engaged metal, which has a complex structure in the depth direction due to heat load and is subject to corrosion due to the internal oxide layer, is divided by the oxygen-rich layer. It is thought that the high oxygen concentration layer prevents the Co-coated metal from being corroded all at once. Note that although the method for producing a deposited film according to the present invention is to create a metal layer of a Co-based alloy by applying heat load, other heat sources may be used as the heat load as in Example 1, or as in Example 1. Heat radiation from the vicinity of the evaporation source may be used as in 2.
【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オージエ分光分
析結果を示す図、第２図は本発明の磁気記録媒体
のオージエ分光分析結果を示す図、第３図は本発
明の磁気記録媒体の製造装置の構成図、第４図
ａ，ｂはそれぞれ従来例および本発明の実施例で
用いるルツボの断面図である。
１……蒸発源、２……酸素導入口、３……冷却
キヤン、４……巻き出し軸、５……巻き取り軸、
６……基板、７……加熱用フイラメント。
FIG. 1 is a diagram showing the results of Auger spectroscopic analysis of a conventional magnetic recording medium, FIG. 2 is a diagram showing the results of Augier spectroscopic analysis of the magnetic recording medium of the present invention, and FIG. 3 is a diagram showing the manufacturing apparatus for the magnetic recording medium of the present invention. FIGS. 4a and 4b are cross-sectional views of crucibles used in the conventional example and the embodiment of the present invention, respectively. 1... Evaporation source, 2... Oxygen inlet, 3... Cooling can, 4... Unwinding shaft, 5... Winding shaft,
6...Substrate, 7...Heating filament.