JPH08102051A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To improve the running durability of a vapor deposited magnetic recording medium. CONSTITUTION: At least one magnetic layer 2, 3 is formed on one side of a substrate 1. A diamondlike carbon layer 4 is disposed on the magnetic layer, a back coating layer 6 of a metal or metalloid is formed on the other side of the substrate 1 and a diamondlike carbon layer 7 is further disposed on the top of the back coating layer 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal vapor deposition type magnetic recording medium, and more particularly to a metal vapor deposition type magnetic recording medium having improved running durability.

[0002]

2. Description of the Related Art Magnetic recording media, such as magnetic tape,
There are coating tapes made by applying a magnetic paint in which magnetic powder is dispersed in a binder on a film that is a support, and vapor deposition tapes made by vapor-depositing a metal on a film and containing no binder at all. . The vapor-deposited tape is promising for high-density recording because the magnetic layer does not contain a binder and thus the density of the magnetic material can be increased.

The vapor-deposited tapes currently on sale or under development have a magnetic layer formed by vapor-depositing a metal on a support such as PET (polyethylene terephthalate), polyimide or aramid using a vacuum vapor deposition method. Furthermore, protect the magnetic layer,
In addition, a top coat layer is formed to have a function as a lubricant for smooth contact with the recording / reproducing head, or carbon black (particle size 10 to 10 100 nm) is dispersed in a binder (a vinyl chloride type, a urethane type, a nitrification type, etc. is used alone or as a mixture), and the thickness after drying is 0.4 to 1.0 μm by the gravure method, the reverse method or the die coating method. It has been generally practiced to form a back coat layer by applying the above method.

However, when the backcoat layer is first applied and then the magnetic layer is vacuum-deposited, degassing (generated from the solvent of the binder) is generated from the backcoat layer in a vacuum system, and the degree of vacuum is lowered. There is a problem that does not work, conventionally, after depositing the magnetic layer in vacuum,
The back coat layer is applied after the tape is taken out into the atmosphere.

However, even with this method, in the step of applying the back coat layer, the magnetic layer becomes dirty or dust is attached, and a dropout inspection (a magnetic tape is put in a cassette deck for inspection and a certain signal is recorded). In the inspection to detect the dropout where the reproduction signal is missing due to scratches on the tape surface or adhesion of foreign matter).
There was a problem of increasing the number of dropouts.

Further, although carbon black has good conductivity, there is a problem in that since the binder is added, the conductivity is lowered and the antistatic effect is lowered.

In order to solve the above problems, a back coat layer which has been conventionally formed by coating in air is formed by metal vapor deposition in vacuum.

[0008]

However, the magnetic tape having a back coat layer formed by metal vapor deposition is deformed in a wavy manner at the end thereof (so-called "wakame" phenomenon occurs), so that the running durability is deteriorated. There was a problem of doing.

Therefore, an object of the present invention is to improve running durability from the surface of the back coat layer in a metal vapor deposition type magnetic recording medium.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, completed the present invention.

That is, according to the present invention, at least one magnetic layer formed on one surface of the support, a first diamond-like carbon layer formed on the magnetic layer, and the other surface of the support are provided. A magnetic recording medium having a formed backcoat layer made of a metal or a semimetal, and a second diamond-like carbon layer formed on the surface opposite to the surface where the backcoat layer contacts the support. Is.

The magnetic recording medium of the present invention comprises a magnetic layer comprising at least one metal thin film formed on a support by a method such as vapor deposition, and a magnetic layer of the support opposite to the surface on which the magnetic layer is formed. A backcoat layer made of a metal or a semimetal is formed, and a diamond-like carbon layer is formed on each of the magnetic layer and the surface opposite to the surface where the backcoat layer contacts the support.

[Magnetic Layer] Examples of the magnetic material for forming the magnetic layer include ferromagnetic metal materials used in the manufacture of ordinary metal thin film type magnetic recording media. For example, ferromagnetic metal such as Co, Ni, Fe , Fe-Co, Fe-Ni, Co-Ni, Fe-Co-
Ni, Fe-Fh, Fe-Cu, Co-Cu, Co-Au, Co-Y, Co-L
a, Co-Pr, Co-Gd, Co-Sm, Co-Pt, Ni-Cu, Mn-B
i, Mn-Sb, Mn-Al, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co
Examples include ferromagnetic alloys such as -Cr and Ni-Co-Cr. As the magnetic layer, a thin film of iron or a thin film of a ferromagnetic alloy containing iron as a main component is preferable, and at least one selected from a ferromagnetic alloy containing iron, cobalt, nickel as a main component and nitrides or carbides thereof is preferable. .

For high density recording, the magnetic layer of the magnetic recording medium is preferably formed on the substrate by oblique vapor deposition. The method of oblique vapor deposition is not particularly limited and is based on a conventionally known method. The degree of vacuum during vapor deposition is about 10 ⁻⁴ to 10 ⁻⁷ Torr. The magnetic layer formed by vapor deposition may have either a single-layer structure or a multi-layer structure, and in particular, the durability can be improved by introducing an oxidizing gas to form an oxide on the surface of the magnetic layer.

In the case of two layers, the thickness of the lower magnetic layer is 100 to 2000Å, and the thickness of the upper magnetic layer is 50 to 10
00Å is preferable, and in the case of three layers, the thickness of the lower magnetic layer is 10
The thickness of the intermediate magnetic layer is preferably 0 to 2000Å, the thickness of the intermediate magnetic layer is 100 to 1000Å, and the thickness of the upper magnetic layer is preferably 50 to 1000Å. Further, the number of magnetic layers is preferably as large as possible for high frequency recording, but it is considered that two to five layers are suitable as a practical range.

[First Diamond-Like Carbon Layer]
The magnetic recording medium of the present invention has a diamond-like carbon layer formed on the magnetic layer, and the diamond-like carbon layer is preferably formed by the ECR plasma CVD method.

The ECR plasma CVD method is a method for forming a carbon thin film by applying a microwave to a gas serving as a carbon source in a high vacuum to convert the gas into a plasma. In the present invention, a layer composed of a diamond-like carbon thin film is formed between the magnetic layers of the support. The diamond-like carbon thin film is an amorphous carbon film and is considered to have a structure in which graphite bonds and diamond bonds are mixed.

When diamond-like carbon is formed by ECR plasma CVD, as a carbon source, a lower hydrocarbon gas such as methane, ethane, propane and butane is used alone, or a mixed gas thereof is mixed with argon gas or hydrogen gas. It can also be used.

The ECR plasma CVD method may be carried out according to a known method for forming a carbon thin film. Usually, the microwave wavelength is 2.45 GHz, the output is about 500 W, and the degree of vacuum is 10 ^-1 to 10 -10.
^It suffices to determine the flow rate of the carbon source gas so that it becomes ^-4 Torr.

The thickness of the first diamond-like carbon layer formed by the present invention is not limited, but may be 20-200.
Å is preferred.

[Backcoat Layer] The magnetic recording medium of the present invention is a backcoat layer formed by adhering a metal or a semimetal to the surface of the support opposite to the surface on which the magnetic layer is formed in vacuum. Have. Here, the method of depositing the metal or semi-metal in vacuum is not limited, but physical vapor deposition
(PVD), in particular, a thermal evaporation method and a sputtering method can be mentioned.

In addition, since the surface of the back coat layer may be too smooth and running stability may be deteriorated by simply adhering a metal or a semi-metal, in such a case, the friction coefficient of the back coat layer is controlled. Therefore, an oxidizing gas is introduced at the time of attachment to roughen the surface due to the oxidizing action. Examples of the oxidizing gas include oxygen, air and ozone.

Here, when the surface electric resistance of the back coat layer uses a metal, it is 5 to 10 ⁵ Ω / □, particularly 10 ² to 10 ³ Ω.
It is desirable to set the amount of oxidizing gas introduced so that it becomes / □. When using a semi-metal, 10 ⁵ to 10 ⁸ Ω /
It is desirable to set the amount of oxidizing gas introduced so that it is □, especially 10 ⁶ to 10 ⁷ Ω / □.

That is, when an oxidizing gas such as oxygen is introduced, the bond between the metal or the semimetal is weakened and the conductivity is lowered. Therefore, the surface electric resistance value is determined and the amount of the oxidizing gas introduced is determined. Regulate.

In the case of a metal back coat layer, the surface electric resistance value is 5 to 10 ⁵ Ω / □ when the surface electric resistance value is 5 Ω.
When it is lower than / □, the amount of oxygen is small and the friction coefficient of the back coat layer becomes too low. Surface electric resistance value is 10
If it is higher than ⁵ Ω / □, the friction coefficient will be too high, and the conductivity will be too low, which may lead to the attachment of dust. The target should be approximately 10 ² to 10 ³ Ω / □.
The center line average roughness corresponds to Ra = 4 to 20 nm.

Various metals can be considered as the metal deposited as the back coat layer, but Al, Cu, Zn, Sn, Ni, Ag, etc., and alloys thereof are used. However, Al and Cu are the most suitable in terms of price, deposition rate, and stability after oxidation. Further, as the semi-metal forming the back coat layer, Si, G
e, As, Sc, Sb, etc. are used. In particular, Si is most suitable in terms of price, adhesion speed, and the like.

The back coat layer has a thickness of 0.05 to 1.0 μm.
It is a degree. The degree of vacuum when performing the thermal evaporation method or the sputtering method for forming the back coat layer is 10 ^-2 to 10 ^-7 Torr.
It is about 10 ^-3 to 10 ^-6 Torr.

[Second Diamond-Like Carbon Layer]
The second diamond-like carbon layer formed on the back coat layer side is also formed by the ECR plasma CVD method like the above-mentioned first diamond-like carbon layer.
The film thickness and the like are also as described above.

[Lubricating Layer] In the magnetic recording medium of the present invention, a lubricating layer made of a lubricant may be formed on the first diamond-like carbon layer. Further, a lubricating layer may be provided on the surface opposite to the surface where the second diamond-like carbon layer contacts the back coat layer.

The lubricating layer may be prepared by dissolving a suitable lubricant in a solvent and coating it in the air by a conventional method, or by spraying the lubricant in a vacuum.

In the method of spraying the lubricant in a vacuum, the lubricant is preferably sprayed on the magnetic layer formed on the support by a sprayer equipped with an ultrasonic oscillator (hereinafter referred to as an ultrasonic sprayer). More specifically, the ultrasonic atomizer includes a lubricant supply unit, a unit for applying ultrasonic waves to the lubricant supplied from the supply unit to atomize the lubricant (ultrasonic oscillator), and the atomized lubricant. And a nozzle for spraying. Further, a nozzle type spraying device may be used. As the nozzle type spraying device, a device generally called a one-fluid nozzle can be used.

By spraying a lubricant as fine particles using an ultrasonic atomizer, it is weak at high temperatures (200 ° C. or higher) and has a low vapor pressure. Therefore, it is conventionally used for forming a lubricating layer by coating in air. It is now possible to spray a fluorine-based lubricant such as perfluoropolyether in a vacuum.

As the perfluoropolyether, those having a molecular weight of 2000 to 5000 are suitable, and for example, "FOMBLIN Z
DIAC "[carboxyl group modified, Montecatini Co., Ltd.
Commercially available], "FOMBLIN Z DOL" (alcohol-modified, Montecatini Co., Ltd.) can be used. Since these have a hydroxyl group or a carboxyl group at the terminal, they can enhance the binding between the lubricant and the magnetic layer.
It is particularly preferably used in the present invention.

In addition to these, it is also possible to use a fluorine-based lubricant containing a benzene ring, a double bond, a branched chain, etc., a fatty acid-based lubricant, or another lubricant. However, since the fluorine-based lubricant improves not only the durability but also the corrosion resistance as compared with the fatty acid-based lubricant, it is particularly preferably used in the present invention.

In spraying the lubricant, the lubricant may be a fluorine-based inert solvent (for example, perfluorocarbon such as "Florinato" manufactured by Sumitomo 3M Ltd., perfluoropolyether such as "Galden" manufactured by Montecatini Co., Ltd.). ), Dissolved in an appropriate solvent such as an alcohol solvent
It is preferably used as a solution of about 0.001 to 10% by weight, particularly 0.02 to 2.0% by weight. When perfluoropolyether is used as the lubricant, perfluorocarbon can be used as the solvent, and the concentration in that case is about 0.001 to 1.0% by weight, preferably 0.05 to 0.2% by weight.

In the method for producing a magnetic recording medium of the present invention, it is desirable that the fine particles of the lubricant (lubricant solution) to be sprayed be as fine as possible, and the frequency of ultrasonic waves applied depends on the type and viscosity of the lubricant. It is determined, but is generally selected from the range of 10kHz to 5MHz.

Further, in the method of manufacturing a magnetic recording medium of the present invention, the amount of spray or the amount of lubricant applied may be appropriately determined in consideration of the application of the magnetic recording medium, the type of lubricant, etc. The thickness of the lubricating layer is preferably adjusted to be about 10 to 200 Å. The degree of vacuum at the time of spraying the lubricant is about 5 × 10 ^{-4 to} 5 × 10 Torr, preferably 5 × 10 ^-1 to
It is 5 × 10 ^-2 Torr.

[Support] In the method for producing a magnetic recording medium of the present invention, the support includes polyester such as polyethylene terephthalate and polyethylene naphthalate; polyolefin such as polyethylene and polypropylene; cellulose such as cellulose triacetate and cellulose diacetate. Derivatives; polycarbonate; polyvinyl chloride; polyimide; plastics such as aromatic polyamide are used. The thickness of these supports is 3-50 μm
It is a degree.

An example of the magnetic recording medium of the present invention described above is shown in FIG. FIG. 1 is a schematic diagram showing the structure of a magnetic recording medium having two magnetic layers. In FIG. 1, 1 is a support, 2 is a first magnetic layer, 3 is a second magnetic layer, 4 is a first diamond-like carbon layer, 5 is a lubricating layer, 6 is a backcoat layer made of metal or semimetal, Reference numeral 7 is a second diamond-like carbon layer, and 8 is a lubricating layer.

[0040]

Embodiments of the present invention will be described below. However, the invention is not limited to these examples.

Example 1 (i) Magnetic Recording Medium Manufacturing Apparatus FIG. 2 is a schematic view showing an example of an apparatus for manufacturing the magnetic recording medium of the present invention. In FIG. 2, 21 is a first chamber, 22 is a second chamber, 23 is a third chamber, 24 is a support, and 25,2.
5'is an ion gun, 26,26 'is a crucible, 27,27' is an oxygen gas inlet pipe, 28,28 ', 28''is a cooling can, 29,29' is an ECR plasma CVD device, 30 is an unwind roll, 31 is a winding roll.

The support 24 runs from the unwinding roll 30 onto the cooling can 28, and the metal or semimetal or its alloy in the crucible 26 is vaporized by the ion beam emitted from the ion gun 25 and adheres to the support. . Thereby, the back coat layer is formed. Next, the carbon source turned into plasma is irradiated from the ECR plasma CVD apparatus 29, and a second diamond-like carbon layer is formed on the surface of the back coat layer opposite to the surface in contact with the support.

Next, the support 24 is transferred to the chamber 22, a first magnetic layer is formed on the surface opposite to the surface on which the back coat layer is formed, and then the second magnetic layer is formed on the first magnetic layer. A layer is formed. A magnetic metal such as cobalt is contained in the crucible 26 '.

Next, the support 24 is conveyed to the chamber 23, and a second diamond-like carbon layer is formed on the second magnetic layer by the ECR plasma CVD apparatus 29 ', after which the support 24 is wound by the winding roll 31. Taken.

The apparatus comprises a support, a back coat layer, and
A device for forming a second diamond-like carbon layer, first and second magnetic layers on the side opposite to the back coat layer, and a first diamond-like carbon layer on the second magnetic layer in this order, and the inside is not shown. A vacuum is maintained by vacuum means.

(Ii) Manufacture of magnetic recording medium A PET film (thickness: 6.5 μm) was set in the apparatus shown in FIG. 2, and the Al in the crucible 26 from the ion gun 25 was set in the chamber 21.
A Cu alloy (85:15) was irradiated with an ion beam to form a back coat layer on the film. Then ECR plasma
A second diamond-like carbon layer was formed by the CVD device 29.

Next, first and second magnetic layers made of cobalt are formed on the surface of the chamber 22 opposite to the surface on which the back coat layer is formed, and the first magnetic layer is further formed on the second magnetic layer in the chamber 23. A diamond-like carbon layer was formed.

The film forming conditions by the ECR plasma CVD method are as follows. Microwave wavelength: 2.45 GHz Microwave power: 1 kW Working gas: CH ₄ gas 100 SCCM, hydrogen gas 100 SCCM Also, the degree of vacuum in chambers 21 and 23 is 4 × 10 ^-3 Torr, and the degree of vacuum in chamber 22 is 2 × 10 ⁻⁵ Torr, the running speed of the film was 0.5 m / min.

Then, in another chamber, a perfluoropolyether “FOMBLIN Z DOL” was formed on the surface of the second diamond-like carbon layer on the backcoat layer side opposite to the surface in contact with the backcoat layer.
0.0 of [Alcohol modified, Montecatini Co., Ltd.]
5 wt% solution [solvent is fluorine-based inert liquid "PF-5080"
(Sumitomo 3M Co., Ltd.)] so that the thickness after drying is 15 Å (second lubricating layer), and the thickness after drying is applied on the first diamond-like carbon layer on the magnetic layer side. 16
Å Apply [first lubrication layer], then 100 ℃
And dried to obtain a magnetic tape.

After that, the magnetic tape was taken out into the atmosphere, and
Slit to a mm width and insert into an 8mm cassette,
A video cassette for Hi-8 was made.

The thickness of each layer of the magnetic tape thus obtained is as follows.・ First lubrication layer… 16Å ・ First diamond-like carbon layer… 70Å ・ Second magnetic layer… 1000Å ・ First magnetic layer… 1000Å ・ Backcoat layer… 1500Å ・ Second diamond-like carbon layer… 70Å ・ No. Second lubrication layer ... 15Å.

(Iii) Performance Evaluation The running durability of the video cassette obtained above was evaluated by the following method. Table 1 shows the results. Running durability Repeatedly recorded and played the video cassette 500 times or 1000 times to increase the jitter (screen shake) on the commercially available Hi-8 V
The measurement was performed by connecting a jitter meter to the TR device.

Comparative Example 1 A video cassette was manufactured by the apparatus shown in FIG. 2 in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. However, the second diamond-like carbon layer on the back coat layer side was not formed. The results are shown in Table 1.

Comparative Example 2 The same evaluation as in Example 1 was performed using a commercially available Hi-8 metal tape. The results are shown in Table 1. The tape used here had a magnetic layer (thickness 2000Å) consisting of a Co-Ni alloy (CO: Ni = 80: 20) on a PET film with a thickness of 6.5 μm.
Oxide protective layer formed on the magnetic layer (thickness 100Å)
And a lubricating layer (thickness 20Å) formed on the protective layer, and a coating type backcoat layer (thickness 5000Å) mainly composed of carbon black formed on the surface opposite to the magnetic layer. ing.

[0055]

[Table 1]

[0056]

As described above, according to the present invention,
A metal vapor deposition type magnetic recording medium having good running durability can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a magnetic recording medium of the present invention.

FIG. 2 is a schematic view showing an example of an apparatus for manufacturing a magnetic recording medium of the present invention.

[Explanation of symbols]

 1: Support 2: First magnetic layer 3: Second magnetic layer 4: First diamond-like carbon layer 5: First lubricating layer 6: Back coat layer 7: Second diamond-like carbon layer 8: Second Lubrication layer 21: First chamber 22: Second chamber 23: Third chamber 24: PET film 25,25 ': Ion gun 26,26': Crucible 27,27 ': Oxygen gas inlet pipe 28,28' , 28 '': Cooling can 29,29 ': ECR plasma CVD 30: Unwinding roll 31: Winding roll

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirohide Mizunoya 2606 Akabane, Kaigamachi, Haga-gun, Tochigi Prefecture Kao Corporation Information Science Research Institute (72) Inventor Akira Shiga 2606 Akabane, Kaiga-cho, Haga-gun, Tochigi Prefecture Hana Information Science Laboratory, Wang Co., Ltd.

Claims (3)

[Claims] 1. At least one magnetic layer formed on one surface of a support, a first diamond-like carbon layer formed on the magnetic layer, and formed on the other surface of the support. A magnetic recording medium comprising a backcoat layer made of a metal or a semimetal, and a second diamond-like carbon layer formed on a surface of the backcoat layer opposite to a surface in contact with the support. 2. The magnetic recording medium according to claim 1, further comprising a lubricating layer on the first diamond-like carbon layer. 3. The magnetic recording medium according to claim 1, wherein the second diamond-like carbon layer further has a lubricating layer on the surface opposite to the surface in contact with the back coat layer.