JPH09293226A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE: To improve moisture resistance and durability by incorporating silicon and oxygen into a ferromagnetic metal film on a nonmagnetic base body. CONSTITUTION: This magnetic recording medium is produced by forming a ferromagnetic metal film on a nonmagnetic base body. When the ferromagnetic metal film is formed, a silicon-based source material and oxygen are incorporated into the film. The ferromagnetic metal film consists of Co or a Co-Ni alloy. When the ferromagnetic metal film is formed by vapor deposition on the nonmagnetic base body, vapor deposition of the ferromagnetic metal film is performed while introducing oxygen as a plasma gas and a silicon gas. The silicon gas used in the production of the magnetic recording medium contains silicon in the molecule and is preferably controlled to 10<-5> Torr pressure. The ferromagnetic film is preferably formed by fusing Co or a Co-Ni alloy with electron beams and then depositing the vapor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having a ferromagnetic metal film as a magnetic recording layer, and more particularly to an improved magnetic recording medium having a rustproof effect and improved moisture resistance and durability.

[0002]

2. Description of the Related Art A technique relating to a magnetic recording medium using a ferromagnetic metal thin film such as Co-Ni, Co-Cr or the like as a magnetic recording layer is used for high recording density such as video recording, digital recording and high-definition recording, or a recording / reproducing apparatus. It has been widely researched and put into practical use in order to reduce its size and improve its performance. However, the metal thin film medium has a problem in that a metal such as iron or cobalt is directly formed on the substrate, so that oxidation occurs due to moisture in the atmosphere and rust occurs. In order to solve this, for example, Japanese Patent Laid-Open No. 2-132
It has been proposed to solve rust prevention by forming a protective film as disclosed in JP-A No. 623 and JP-A-3-224132.
However, in this method, after the deposition process of the magnetic layer,
You have to go through the rust prevention process again,
The cost is high. In some cases, after forming the magnetic layer in vacuum, the magnetic layer is once taken out into the atmosphere, and the protective film is formed again in vacuum. Oxygen and moisture adhere to the magnetic surface and Even if the protective film is formed, there is a problem that the film peels off in an atmosphere of high temperature and high humidity (60 ° C., 90% RH, etc.) (normal atmosphere, eg, 40 ° C.).
There is no problem such as peeling at 20% RH, etc.), which is not practical.

[0003]

Ferromagnetic metal thin films are generally oxidized under the influence of moisture in the atmosphere to generate rust,
Since the electromagnetic conversion characteristics are easily deteriorated, a protective film for rust prevention is formed. For example, inorganic oxides, carbides, nitrides and the like or diamond-like films are formed, and heat treatment is performed to firmly form an oxide layer on the metal surface. However, the process is complicated and the cost is high. In addition, when the original fabric is cut to the required width, the end face is not protected at all, and rust progresses, which affects the electromagnetic conversion characteristics. Since the tape without any protective film usually starts to deteriorate from this end face, rust is generated only with the upper protective layer on this end face regardless of the presence or absence of the protective film. The present invention is intended to reduce costs by omitting steps and prevent deterioration of rust-preventive properties by depositing a vapor deposition film from the vacuum layer, which is conceivable at the time of forming a protective film, into the air atmosphere, and prevent rusting due to exposure of end faces in the cutting process. To provide a method.

[0004]

According to the present invention, in a magnetic recording medium having a ferromagnetic metal film formed on a non-magnetic substrate, a silicon-based raw material and oxygen are contained when the ferromagnetic metal film is formed. It is a characteristic magnetic recording medium. The present invention is also a method for producing a magnetic recording medium by forming a ferromagnetic metal film on a non-magnetic substrate, wherein the ferromagnetic metal film is formed while introducing oxygen and a silicon-based gas. And provide a method.

As a method for forming a ferromagnetic metal film on the surface of a non-magnetic substrate, there is an electron beam evaporation method. In this method, Co stored in a crucible by an electron beam in a vacuum is used.
And / or a magnetic metal or alloy such as a Co-Ni alloy is irradiated and melted, and this is vapor-deposited on a long non-magnetic substrate film such as polyethylene terephthalate moving along the surface of the rotating drum at a constant speed. To do. Generally, in this electron beam evaporation method, oxygen is introduced at the final stage of evaporation to oxidize the surface of the magnetic metal film to form an oxide layer, thereby increasing the surface hardness and durability. .

[0006] The present inventors have found that when a silicon compound which is gasified in a vacuum is introduced at the same time as the introduction of oxygen and the silicon and oxygen are bonded to the ferromagnetic metal vapor deposition film by using the plasma state. It was confirmed that the rust effect was significantly improved. Silicon oxide forms silicon oxide on the surface and inside of the ferromagnetic metal film to increase the surface hardness, and at the same time coats vapor-deposited particles along the column direction. The plasma discharge here means that the electrode is provided in parallel with the CAN for forming the magnetic layer and the discharge is generated by a power source having an appropriate frequency, or the film-forming space is usually formed by an electron beam. The energy generated into plasma may be used. Silicon gas is introduced at the same time as oxygen if it is gaseous at room temperature and atmospheric pressure. If the silicon raw material is liquid at room temperature and normal pressure, it is introduced into the vapor deposition device using a liquid gasifier (the liquid is evacuated and heated), or a silane-based liquid is contained as oxygen gas. It is introduced by bubbling the inside of the container and vaporizing it simultaneously with oxygen gas. In general, the method of introducing in this way is adopted, but the method may be other than the above method as long as it is introduced into the vapor deposition chamber. In the present invention, oxygen and silicon-based molecules are introduced at the same time, and a film is formed by using plasma discharge. Therefore, surface hardening and rust prevention can be carried out at the same time by one film formation, which is different from the conventional method. The process can be significantly shortened and the manufacturing cost can be significantly reduced. Further, it is possible to obtain the same or more rustproofing effect as that of the conventional separately formed film, and the rustproofing effect of the cut edge portion is improved.

As the silicon compound to be introduced, a compound which can be gasified in a gaseous state or a vacuum (about 10 ^-5 torr) is used. As such a gas, S ₂ H ₄ , trimethylsilane, tetramethylsilane, trimethoxysilane, tetramethoxysilane or the like can be used. The amount of oxygen and the amount of silicon-based gas introduced are 30 to 500 SCCM of oxygen per 1 m ^{2 of} vapor deposition tape, and the amount of silicon-based gas is 10 to 2
00SCCM is desirable. However, the appropriate amount depends on the device and may be determined experimentally. The introduction of the silicon-based gas and oxygen is carried out at the same time as the formation of the ferromagnetic metal film, but there is no effect on the magnetic properties of the ferromagnetic metal film. Further, in order to increase the hardness or wear resistance of the magnetic recording medium of the present invention, a known diamond-like carbon film may be formed on the surface side by an ionization vapor deposition method or the like. Alternatively, the lubricating layer may be formed after forming the silicon oxide film on the uppermost layer. In addition, SiO _x as a base layer (x = 1.5~1.9)
If a layer having a high moisture barrier property is provided, the rust prevention effect is further enhanced.

As the material of the ferromagnetic metal film, Co, Co--
Ni, Co-Ti, Co-O, Co-Mo, Co-Ni
-O, Co-Cr, Co-Cr-Ni, etc. can be used, but especially Co-Ni (weight ratio 70-95: 30-5).
Is common. In the following examples, Co80 weight-Ni
20% by weight was used. The structure of the magnetic layer is a single layer,
Any multilayer (two or more layers) may be used, and the effect is not particularly affected. Further, the multilayer does not have to have the same composition for each layer, and is designed to have the best electromagnetic conversion characteristics. Conventionally known plastic substrates such as polyamide and polyester can be used as the non-magnetic substrate, but polyethylene terephthalate is used in the following examples.

[0009]

[Function] A silicon compound is introduced at the same time as the introduction of oxygen,
When silicon and oxygen are combined with the ferromagnetic metal vapor deposition film using plasma discharge, silicon oxide is formed on the surface and inside of the ferromagnetic metal film, which effectively blocks moisture in the air. To do. The silicon oxide or the metal oxide formed at the same time increases the surface hardness. Further, it is possible to prevent the invasion of water from the cut edge of the ferromagnetic metal film, but the magnetic characteristics are not affected.

[0010]

[Explanation of the embodiment]

Example 1 In a vacuum, an electron gun with a power of 5 kW was used to melt Co80-Ni20 (weight ratio) in a crucible and vapor deposition was performed on a polyethylene terephthalate (PET) substrate film. Simultaneously with the vapor deposition process, 50 SCCM oxygen and Table 1
Using silane as the silicon-based gas at the flow rate shown in
A ferromagnetic metal film is formed on the base film by plasmaizing it by plasma discharge using the conditions of 100 KHz and 100 W.
A film was formed at 000Å. Table 1 shows the saturation magnetic flux density Bm, the coercive force Hc, the squareness ratio, and the antirust effect of the obtained magnetic recording medium. The anticorrosive effect was stored in an environment of 60 ° C. and 80% RH for 1 week, and the reduction rate of the saturation magnetic flux density was measured. For comparison,
A magnetic recording medium (blank) into which only oxygen was introduced at the final stage of the formation of the ferromagnetic metal film and a magnetic recording medium having a ferromagnetic metal film and then a silicon oxide protective film formed thereon were manufactured. The results are shown in Table 1.

[0011]

[Table 1]

[0012]

[Effect] It is clear from Table 1 that among the samples labeled as simultaneous film formation, oxygen and silicon were introduced at the same time as the formation of the magnetic layer, but those in which silicon of 10 CSSM or more was introduced were formed separately ( A sample having a magnetic layer and a protective layer sequentially formed) shows moisture resistance equal to or higher than that of the sample. However, with respect to the cutting edge, the sample of the present invention is sufficiently protected, whereas the samples indicated as separate film formation are not protected, so that the sample of the present invention is excellent in the rust prevention effect. It is clear. Further, in the present invention, the flow rate is 10 even though oxygen and silicon are simultaneously introduced during the formation of the ferromagnetic metal film.
In the range of up to 200 SCCM, the magnetic characteristics are not substantially affected. From the above, in the present invention, since silicon and oxygen are combined with the ferromagnetic metal vapor deposition film by using plasma discharge, silicon oxide is formed on the surface and inside of the ferromagnetic metal film, and moisture in the air is removed. It can be effectively blocked.
The silicon oxide or the metal oxide formed at the same time increases the surface hardness. Further, it is possible to prevent the invasion of water from the cut edge of the ferromagnetic metal film, but the magnetic characteristics are not affected.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromichi Kanazawa 1-13-1, Nihonbashi, Chuo-ku, Tokyo TDK Corporation

Claims (5)

[Claims] 1. A magnetic recording medium having a ferromagnetic metal film formed on a non-magnetic substrate, wherein the ferromagnetic metal film contains a silicon compound and oxygen. 2. The magnetic recording medium according to claim 1, wherein the ferromagnetic metal film is Co or a Co—Ni alloy. 3. A method for producing a magnetic recording medium by depositing a ferromagnetic metal film on a non-magnetic substrate, wherein the ferromagnetic metal film is deposited while introducing oxygen and a silicon-based gas as plasma gas. A method of manufacturing a magnetic recording medium, comprising: 4. The silicon-based gas contains silicon in the molecule,
The method according to claim 3, wherein the gas is a gas at a pressure of 10 ^-5 torr. 5. The method according to claim 3, wherein the ferromagnetic metal film is deposited by melting Co or Co—Ni alloy with an electron beam.