JP2500896B2 - Magnetic tape - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape for recording signals such as video, audio and data at a high density by using a ferromagnetic metal thin film as a recording film.

[0002]

2. Description of the Related Art As a recording medium for realizing high-density magnetic recording, a recording medium using a thin film of a ferromagnetic metal such as Co, Ni, Cr, and Fe has been noted and various practical studies have been made.

In magnetic recording, loss occurs when the gap between the recording film made of a ferromagnetic material and the magnetic head as an electromagnetic transducer is large. In particular, the loss is remarkable in the high signal frequency region, and this gap must be minimized in high density recording.

In recording and reproducing signals of video and audio, a magnetic tape as a recording medium is always in contact with a magnetic head.

When high reliability is required as in the case of recording a data signal, the magnetic head is used so as to float above the surface of the recording medium in a non-contact state. Even in this case, however, when rotating the recording medium, Many devices are configured so that they come into contact with each other when starting and stopping. However,
Even in the case of a data signal, the recording medium and the magnetic head are brought into contact with each other when the requirement for reliability is relatively gentle, such as with a floppy disk.

Considering further high density recording in the future, ideally, it is necessary that the recording medium and the magnetic head are in contact with each other and high reliability is ensured.

That is, in magnetic recording, there is a problem basically different from the optical recording method in that the recording medium and the magnetic head are in contact with each other.

In a recording medium having a ferromagnetic metal such as Co, Cr, Ni and Fe as a recording film, the recording film is contacted with the magnetic head when a protective film is not formed on the surface. The formation of an effective protective film is an important issue because it is damaged such as peeling off in a short time. In particular, as described above, this is an important issue for a magnetic tape in which recording / reproduction is performed by constantly contacting the magnetic head.

In a conventional magnetic recording medium in which magnetic powder is mixed with a binder and applied to a carrier, by adding a substance imparting wear resistance and lubricity to the binder, the magnetic recording medium is contacted with the magnetic head. Although the problems that have occurred have been avoided, in the case of a ferromagnetic metal thin film, if the recording film itself is required to have improved properties such as wear resistance, lubricity, and environmental resistance, the magnetic properties of the recording film Deterioration is inevitable.

Therefore, when these ferromagnetic metal thin films are used as the recording film, it is necessary to form a protective film on the surface to secure abrasion resistance and the like. However, such a protective film causes a gap with the above-mentioned magnetic head, and its thickness must be as small as possible.

However, conventionally, as a protective film of a ferromagnetic metal thin film, a film formed by coating or vacuum-depositing a lubricating material made of an organic substance has been attempted, but both have poor wear resistance and a long time. Could not stand the use of. Alternatively, a material such as graphite that forms an amorphous carbon film on the surface of a ferromagnetic metal by a method such as vacuum deposition and sputtering is considered, but this also improves lubricity but wear resistance. On the other hand, it is insufficient.

[0012]

When the above-mentioned materials are used as the protective film, the thickness of the protective film must be increased because of insufficient abrasion resistance. This increases the gap between the magnetic head and the head, resulting in a large loss.
Further, since these protective film materials are worn by the contact sliding of the magnetic head, the generated fine powder adheres to the surface of the magnetic head, and sometimes the reproduction signal output is significantly reduced.

Due to the above problems, the practical application of a high-density magnetic recording device using a ferromagnetic metal thin film as a recording film is extremely limited, and the original high-density recording cannot be achieved unless this problem is solved. it is conceivable that.

The present invention has been made in view of the above points, and provides a recording medium having a protective film excellent in abrasion resistance on a recording film made of a ferromagnetic metal.

[0015]

In order to solve the problems of the conventional protective film as described above, the magnetic tape of the present invention protects a diamond-like carbon film having a Vickers hardness of 2000 kg / mm ² or more. It is used as a film.

In this case, in particular, when the protective film is a protective film synthesized by chemical vapor deposition by accelerating at least ions in hydrocarbon gas plasma, it is a good quality protective film excellent in abrasion resistance. The function of is obtained. In such a case, the specific resistance of diamond-like carbon is 10 ⁷ to 10 ¹³ Ω.
・ In the range of cm, a more stable protective film can be obtained.

[0017]

It has been found that the Vickers hardness is an important factor when a diamond-like carbon film is used as a protective film. That is, by using a diamond-like carbon film having a Vickers hardness of 2000 kg / mm ² or more as a protective film, the magnetic recording material is reliably protected in a magnetic tape in which the magnetic head is constantly contacted and frictionally slid, It is possible to realize a protective film that is thin enough not to deteriorate the magnetic recording characteristics.

Then, in order to form such a protective film for the diamond-like carbon film, the PI-CV invented by the present inventor is invented.
It is preferable to use the D method.

Conventionally, many reports have been made on the technique for forming a diamond thin film, as listed below.

(1) Yoshinori Namba: Research on low-pressure synthesis of diamond thin film, applied mechanical engineering, July 1984 (2) Seiichiro Matsumoto: Low-pressure synthesis of diamond, Genka Kagaku, September 1984 (3) Nobuo Setaka: Low-pressure synthesis of diamond, Japan Industrial Technology Promotion Association, Technical Material No. 138, Shown 59/6/20 However, all of them are still in the research stage, requiring high temperature heating of the substrate, and low deposition rate. Or, it has not been put to practical use because it is impossible to form a uniform film over a wide area.

We have developed a method for forming a carbon film of high hardness that exhibits characteristics similar to diamond (Kurokawa et al .: Formation and evaluation of a carbon film of high hardness by the plasma injection CVD method, Spring Meeting of the Seiki Society of 1985). Academic Proceedings, No.422).

According to the method developed by us, methane gas is made into plasma at a low pressure of 10 to 20 Pa, and at least ions in the plasma are jetted to the substrate by an accelerating electric field, so that the substrate is kept at room temperature without heating. A carbon film can be formed at a low temperature and at a high speed of about 5000 Å / min, and we call it a plasma injection CVD method (hereinafter abbreviated as PI-CVD method. Is the Chemical Vap
er Deposition (chemical vapor deposition). Further, for details of the PI-CVD method, in addition to the collection of scientific lectures of the Seiki Institute Spring Conference, see, for example, Japanese Examined Patent Publication 63.
-26195 (JP-A-61-130487) and JP-A-61-136678. ).

The carbon film formed by the PI-CVD method is amorphous with a bonding state close to diamond including the electron arrangement of SP ³ and a Vickers hardness of 2000 kg / mm ^2.
And has excellent wear resistance. In the measurement of the friction coefficient using a steel ball, a value of 0.1 or less is obtained, which is equal to or less than the friction coefficient of a magnetic tape or the like containing a lubricant. Furthermore, the thermal conductivity is about 0.6 cal / cm · sec · ° C, which is almost the same as metal,
It also excels in the dissipation of frictional heat.

In the PI-CVD method, there are two conditions for the material of the substrate on which a film can be formed. First, the substrate material has a specific resistance of 1
It is preferably about 0 ¹³ Ω · cm or less. 10 ¹³ Ω ・
Materials exceeding cm are generally good electrical insulators and
In the I-CVD method, ions are jetted onto the substrate,
The insulating material is charged and repels ions, so that a strong film cannot be formed. However, if a neutralizing means such as irradiation with an electron beam is added, this is not the limitation, but this is not preferable because it causes defects such as a complicated device configuration.

As the second condition, it is preferable that the substrate material has a strong chemical affinity with carbon and a strong bonding force between the atoms of the formed carbide.

Materials satisfying the above two conditions are Al and B.
e, Co, Cr, Fe, Mn, Ni, Zr, Hf, V, Nb, Ta, Mo, W
Such as metals, alloys containing them as the main component, and S
It is a semiconductor such as i, Ge, B, or SiC. In particular, Si, B and
Cr can form a strong bond with carbon such as a covalent bond.

The specific resistance of the high hardness carbon film formed by the PI-CVD method depends on the film forming conditions, but is approximately 10 ⁷ to 10 ¹³ Ω.
-It is in the range of cm, and naturally satisfies the first condition.

Ferromagnetic metals such as Co, Cr, Ni and Fe satisfy the above-mentioned conditions for forming a high hardness carbon film by the PI-CVD method, and a strong protective film is formed thereon. It becomes possible.

As described above, a high hardness carbon film can be formed by the PI-CVD method on a recording film made of a ferromagnetic metal such as Co, Cr, Ni and Fe. In the case of a Cr-based ferromagnetic metal thin film, it is known that a large amount of Cr is unevenly distributed on the surface, and a particularly strong film is formed.

This carbon film has characteristics similar to diamond, and can protect the recording film very effectively. Further, since the carbon is in an amorphous state, it has some flexibility and is effective as a protective film for a recording film on a flexible carrier such as PET.

Further, since the film has high strength and excellent wear resistance, the film thickness may be 1000 Å or less, the gap between the film and the magnetic head can be made small, and it is also suitable for high density recording. 50 if you pay attention to the contact state with the magnetic head
High reliability can be obtained even with a film thickness of 0 Å or less.

[0032] Although the specific resistance of the high-hardness carbon film by PI-CVD method is in the range of 10 ⁷ ~10 ¹³ Ω · cm, as described above, in the case of the degree of specific resistance, 10 ¹⁷ Ω · cm approximately Is less charged by static electricity than glass, etc. Therefore, when it is used as a surface protective film of a disk-shaped magnetic recording medium, electrostatic charge caused by sliding of a magnetic head or friction with air is reduced, and therefore, adhesion of minute dust or the like can be prevented.

[0033]

FIG. 1 shows an embodiment of the present invention. Reference numeral 1 denotes a tape-shaped carrier made of a non-magnetic material such as plastic. A recording film 2 made of a ferromagnetic metal such as Co, Cr, Ni or Fe is formed on this by means such as vacuum deposition and sputtering. This thickness is about 1000Å, and when used as a perpendicular magnetic recording film, for example, Co
Is a main component, and when Cr is added in an amount of 10 to 20%, a columnar structure of Co is formed and Cr is segregated at the boundary portion. Therefore, in this case, the surface layer of the recording film 2 is made of Cr.
It is rich. The surface of the carrier 1 opposite to the recording film 2 may be subjected to various surface treatments for the purpose of improving durability or reducing frictional resistance.

A protective film 3 made of high hardness carbon is formed on the recording film 2 by the PI-CVD method. This film thickness is 1000 Å or less, preferably 500 Å or less, but is appropriately determined according to the required reliability and the configuration of the magnetic recording / reproducing apparatus. The film formation rate by the PI-CVD method can be up to 5000 Å / min, and even the continuous sheet-shaped carrier 1 can be continuously subjected to in-line processing after the recording film 2 is formed. Further, when the film forming rate of the recording film 2 and the film forming rate of the protective film 3 are different, and the latter is slower, batch processing may be performed.

The specific resistance of the protective film 3 is 10 ⁷ to 10 ¹³ Ω · cm.
The degree is small compared to quartz glass (10 ¹⁷ Ω · cm) and the like, and troubles such as charging rarely occur even when the continuous sheet-shaped charge 1 is run inside a vacuum deposition apparatus or the like.

[0036]

EFFECT OF THE INVENTION A ferromagnetic metal is used as a recording film, on which P
By forming high hardness carbon by the I-CVD method as a protective film, the hardness of the protective film is high and the friction coefficient is small when recording / reproducing is performed with the magnetic head in contact with the surface of the protective film. Due to good thermal conductivity and chemical stability, the recording film 2 can be protected for a long period of time without damaging the magnetic head. Moreover, the thickness of the protective film is 1000Å, or 5
It can be set to 00 Å or less, and it hardly deteriorates the magnetic recording / reproducing characteristics.

Further, since the specific resistance is smaller than that of glass or the like, adhesion of dust and the like due to charging is prevented, and damage to the magnetic head and recording medium can be reduced.

As described above, the present invention is extremely useful for realizing a magnetic tape for high density recording using a magnetic recording medium having a ferromagnetic metal as a recording film.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a magnetic tape according to an embodiment of the present invention.

[Explanation of symbols]

 1 carrier 2 recording film 3 protective film

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Claims (3)

(57) [Claims] 1. A magnetic tape comprising a carrier made of a non-magnetic material, a recording film made of a ferromagnetic metal formed on the carrier, and a protective film formed on the recording film. The magnetic tape, wherein the protective film is a diamond-like carbon film having a Vickers hardness of 2000 kg / mm ² or more. 2. The magnetic recording according to claim 1, wherein the protective film comprises a diamond-like carbon thin film synthesized by chemical vapor deposition by accelerating at least ions in a hydrocarbon gas plasma. Medium. 3. The specific resistance of diamond-like carbon is 10 ⁷ to 1
The magnetic tape according to claim 2, wherein the magnetic tape has a resistance of 0 ¹³ Ω · cm.