JPH08102044A - Magnetic recording medium and production thereof - Google Patents

Abstract

PURPOSE: To easily control the film properties such as surface roughness and hardness by forming a back coating layer comprising a carbon thin film by vapor depositing of carbon on the opposite side of a supporting body to the surface where a magnetic layer is vapor deposited. CONSTITUTION: A PTE film with a magnetic layer formed is set in the device shown in the figure and a diamond-like carbon thin film is formed by ECR plasma CVD method on the back surface of the PET film to form a back coating layer. By this method, the film forming rate of the back coating layer is improved, and even when a magnetic layer of a metal material having high rigidity such as cobalt is formed, a back coating layer having enough hardness corresponding to the magnetic layer can be easily formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium.

[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,
Further, a top coat layer is formed to have a function as a lubricant for smooth contact with the recording / reproducing head, or carbon black and ceramic powder (grains) are formed on the surface opposite to the magnetic layer. (Diameter 10 to 100 nm) is dispersed in a binder (a vinyl chloride type, a urethane type, a nitrified cotton type, etc. is used alone or as a mixture), and the thickness after drying is 0.4 by a gravure method, a reverse method or a die coating method. ~ 1.0 μ
It has been a common practice to apply a coating of m to form a backcoat layer.

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, when the backcoat layer is formed in vacuum by metal deposition, it is difficult to control the surface roughness of the backcoat layer, and it is particularly difficult to increase Ra.

Further, when a magnetic layer made of a metal material having excellent magnetic properties, for example, cobalt is formed with a thickness of about 2000Å to improve the performance, the back coat layer has a sufficient hardness to withstand this. Is required to have
It is difficult to form a back coat layer having such hardness by metal vapor deposition. Moreover, when trying to increase the film thickness in order to obtain sufficient hardness, the film formation rate decreases,
This leads to a decrease in productivity.

Therefore, an object of the present invention is to provide a method capable of easily controlling film quality such as surface roughness and film hardness in forming a back coat layer of a magnetic recording medium, and increasing a film forming speed to improve productivity. It is to be.

[0011]

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, when a back coat layer is formed on the surface of the support opposite to the magnetic layer deposition surface, carbon is deposited by vapor deposition on the opposite surface of the support to form a carbon thin film. The present invention provides a method for manufacturing a magnetic recording medium, which comprises forming a back coat layer.

In the method of manufacturing a magnetic recording medium according to the present invention, the carbon thin film is formed by vapor deposition of carbon by ECR plasma CV.
D method or arc discharge is used.

[ECR Plasma CVD Method] The ECR plasma CVD method is a method of applying a microwave to a gas serving as a carbon source in a high vacuum to convert the gas into a plasma to form a carbon thin film. In this method, a back coat layer made of a diamond-like carbon thin film is formed on the surface of the support opposite to the surface on which the magnetic layer is formed. 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 the back coat layer consisting of a carbon thin film is formed by ECR plasma CVD, the carbon source may be a lower hydrocarbon gas such as methane, ethane, propane, butane, or a mixture thereof with an argon gas or a hydrogen gas. The mixed gas described above can also be used.

First, the carbon source gas is ECR plasma CV
When the film is formed by the D method, the ECR plasma CVD method may be performed according to a known method for forming a carbon thin film, and usually the microwave wavelength is 2.45 GHz, the output is about 500 W, and the degree of vacuum is 10 ^-4. A carbon source gas is flowed so as to be about 10 ^-1 Torr.

After the carbon thin film is formed, it is desirable to etch the carbon thin film to adjust it to a desired film quality. Ion etching is preferable as the method for etching the carbon thin film. Specifically, the most convenient method is to ionize hydrogen gas or argon gas using a Kauffman type ion gun and irradiate this on the carbon thin film to etch the graphite part. is there. In this case as well, it may be carried out according to a known ion etching method, but hydrogen gas or argon gas as an ion source is flown so that the degree of vacuum is 10 ⁻⁶ to 10 ⁻⁴ Torr, and the output is about 300 to 2000 W. Is.

When a mixed gas of a carbon source gas and hydrogen or argon is used, a desired film quality can be obtained by adjusting the mixing ratio or flow rate. Also in this case, the graphite portion in the diamond-like carbon is etched by hydrogen ions or argon ions, and a film closer to diamond remains. In this case as well, the ECR plasma CVD method may be performed according to a known method.

[Arc Discharge] In the present invention, when the carbon thin film is formed by arc discharge, the arc discharge may be performed by using an ordinary apparatus for carbon film production. There are a method of using alternating current and a method of using alternating current for the arc discharge, and any of them can be applied. As an example of the implementation conditions, graphite is used as an electrode, the degree of vacuum is 10 ^-3 to 10 ^-7 Torr, the voltage between the electrodes is 10 to 200 V, the current is 100 A or less, and 50 to 100 A.
However, in the case of the DC method, the current is rather low.

Further, the carbon thin film can be formed by a low voltage arc discharge method using a crucible as an electrode. The low-voltage arc discharge method uses a low-voltage, large-current (for example, 200 V or less,
This is a method of forming a carbon thin film by causing an arc discharge of 30 A or more), focusing in a magnetic field parallel to the discharge axis, and heating and evaporating the evaporation material of the crucible (in this case, a carbon source such as graphite).

[Backcoat Layer] The backcoat layer formed of the carbon thin film according to the present invention may be a single layer or multiple layers. The thickness of the back coat layer is not limited, but 500 to
10000Å is preferred.

The surface roughness (Ra) of the back coat layer is
The target should be 10 to 30 nm and the friction coefficient (μ) should be about 0.1 to 0.5, but of course it may be outside this range.

[Magnetic Layer] In the present invention, the magnetic layer is formed by vacuum evaporation. Examples of the magnetic material forming the magnetic layer include ferromagnetic metal materials used in the production of ordinary metal thin film type magnetic recording media.For example, ferromagnetic metals such as Co, Ni and Fe, and Fe-Co, Fe-Ni, Co-Ni, Fe-Co
-Ni, Fe-Fh, Fe-Cu, Co-Cu, Co-Au, Co-Y, Co-
La, 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 present invention, the magnetic layer may be a single layer or a multi-layer. However, when forming a multi-layer magnetic layer by vapor deposition, the thickness of the magnetic layer is two, in the case of two layers, the thickness of the lower magnetic layer. Is 100-2000Å, the thickness of the upper magnetic layer is 50-1000Å
In the case of three layers, the thickness of the lower magnetic layer is 100 ~
It is preferable that the thickness of the magnetic layer in the middle is 2000Å, the thickness of the intermediate magnetic layer is 100 to 1000Å, and the thickness of the upper magnetic layer is 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.

[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.

[Production Method of the Present Invention] In the production method of the magnetic recording medium of the present invention, both the magnetic layer and the back coat layer are formed by vapor deposition in vacuum. In this case, it is possible to maintain the vacuum state during the process of forming each layer, or to break the vacuum once in the process of forming each layer, but from the viewpoint of productivity, it is possible to continue without breaking the vacuum. It is desirable to form both layers. Further, the order of forming each layer does not matter.

[Magnetic Recording Medium of the Present Invention] A magnetic recording medium of the present invention is formed on a magnetic layer formed on one surface of a support and on a surface opposite to the surface on which the magnetic layer is formed. In a magnetic recording medium having a back coat layer, the back coat layer is made of a carbon thin film. The thickness and type of the magnetic layer, the thickness of the back coat layer, the forming method and the like are as described above. The magnetic recording medium of the present invention has a hardness that can withstand a magnetic layer formed of a magnetic material having high rigidity such as cobalt.

[0028]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1 First, cobalt was deposited on a PET film having a thickness of 6.5 μm by a vacuum vapor deposition method to form a magnetic layer having a thickness of 1000 Å.

Next, the PET film on which the magnetic layer was formed was set in the apparatus shown in FIG. 1, and ECR plasma CVD was performed on the back surface of the PET film (the surface opposite to the surface on which the magnetic layer was formed).
A diamond-like carbon thin film was formed by the method to form a back coat layer. Such an apparatus has a chamber 1, an ECR plasma CVD apparatus 2, a cooling can 3 on which a support 6 having a magnetic layer formed thereon runs, an ion gun 4, an unwinding roll 5, and a winding roll 7. FIG.
Among them, A means a gas serving as a carbon source, B means a microwave, and C means hydrogen or argon gas. In this example, etching by an ion gun was not performed.

The thickness of the obtained back coat layer is 500Å
(Measured by Auger electron spectroscopy). ECR
The film forming conditions by the plasma CVD method are as follows. Microwave wavelength: 2.45 GHz Microwave power: 1 kW Working gas: C ₂ H ₆ gas 100 SCCM, H ₂ gas 40 SCCM Vacuum degree: 4 × 10 ^-3 Torr Film running speed: 0.5 m / min Furthermore, magnetic layer and back coat PET with the layer formed
The film was taken out into the air, and a 0.05 wt% solution of perfluoropolyether "FOMBLIN Z DOL" [alcohol-modified, Montecatini Co., Ltd.] was used on both sides of the film [solvent was a fluorine-based inert liquid "PF-5080"]. (Sumitomo 3M Co., Ltd.)] so that the thickness after drying is 15Å,
It was then dried at 100 ° C.

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.

<Performance Evaluation> Running durability, dropout, and average surface roughness (Ra) of the video cassette obtained above.
And the friction coefficient (μ) were measured. Table 1 shows the results.

Running Durability The video cassette was repeatedly reproduced and recorded 1,000 times, and the increase in jitter (screen shake) was measured by connecting a jitter meter to a commercially available Hi-8 VTR device.

Dropout For the measurement of dropout, a dropout counter was used, and a dropout of -16 dB output during 10 μs was taken as a dropout. The number of dropouts per minute is shown in the table.

Example 2 First, cobalt was deposited on a PET film having a thickness of 6.5 μm by a vacuum vapor deposition method to form a magnetic layer having a thickness of 1000 Å.

Next, the PET film having the magnetic layer formed thereon was set in the apparatus shown in FIG. 2, and a thickness of 800 was formed on the back surface of the PET film (the surface opposite to the surface on which the magnetic layer was formed) by arc discharge. A carbon thin film was formed so as to be Å (measured by Auger electron spectroscopy). The film forming conditions by arc discharge are as follows. Gas used: C ₂ H ₆ gas 100 SCCM Vacuum degree: 4 × 10 ⁻³ Torr Film running speed: 0.5 m / min The apparatus shown in FIG. 2 is a cooling system in which a chamber 1 and a support 6 on which a magnetic layer is formed run. It has a can 3, an ion gun 4, an unwinding roll 5, a winding roll 7, and a carbon rod 8. In FIG. 2, C means hydrogen or argon gas.

After that, a mixed gas of hydrogen gas and argon gas (1: 1, flow rate 120 SCCM) was applied to the Kauffman type ion gun 4.
Was used for ionization at an output of 800 W and an acceleration voltage of 1 kV to irradiate a carbon thin film.

The arc discharge is performed by an alternating current method, and the film forming conditions are as follows. In FIG. 2, a voltage of 150 V was applied to the graphite electrode 8 and a current of 50 A was applied to cause arc discharge to deposit graphite on the film.
The degree of vacuum of this discharge part was 5 × 10 ⁻⁴ Torr.

Further, the PET film having the magnetic layer and the back coat layer formed thereon was taken out into the air, and a perfluoropolyether "FOMBLIN Z DOL" was formed on both sides of the film.
0.05% by weight solution of [alcohol modified, Montecatini Co., Ltd.] [solvent is fluorine-based inert liquid "PF-5080"
(Sumitomo 3M Co., Ltd.)] was applied so that the thickness after drying would be 15Å, and then dried at 100 ° C.

After that, a video cassette was manufactured in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. Table 1 shows the results.

Example 3 A video cassette was manufactured in the same manner as in Example 1 and evaluated in the same manner as in Example 1. However, the formation of the back coat layer is
First, a diamond-like carbon thin film was formed by the ECR plasma CVD method, and then the diamond-like carbon thin film was ion-etched.

The film forming conditions by the ECR plasma CVD method are as follows. Microwave wavelength: 2.45 GHz Microwave power: 1 kW Working gas: C ₂ H ₆ gas 100 SCCM Vacuum degree: 4 × 10 ^-3 Torr Film running speed: 0.5 m / min The conditions of ion etching are as follows: . A mixed gas of hydrogen and argon (2: 1, flow rate 100 SCCM) was ionized with a Kauffman type ion gun at an output of 1 kW and an acceleration voltage of 1 kV to irradiate the film. The running speed of the film was 1 m / min. The results are shown in Table 1.

Comparative Example 1 A video cassette was manufactured in the same manner as in Example 1 and evaluated in the same manner as in Example 1. However, the back coat layer was formed by vapor-depositing a Cu-Al alloy (15/85 weight ratio) on the film to a thickness of 1000 liters. Table 1 shows the evaluation results.

[0045]

[Table 1]

[0046]

As described above, according to the present invention, even in a magnetic recording medium in which a magnetic layer having a high rigidity such as cobalt is formed, a back coat layer having a hardness that can sufficiently oppose this can be easily formed. Can be formed. Moreover, it is easy to control the film quality such as surface roughness other than hardness, and the running durability and the like are improved. Further, since the film forming speed at the time of forming the back coat layer is improved, the productivity and the quality can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an ECR plasma CVD apparatus used in the present invention.

FIG. 2 is a schematic diagram of an arc discharge device used in the present invention.

FIG. 3 is a chart showing the results of EELS analysis of the carbon thin films formed in the examples.

[Explanation of symbols]

 1 chamber 2 ECR plasma CVD equipment 3 cooling can 4 ion gun 8 carbon rod

 ─────────────────────────────────────────────────── ─── 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 (8)

[Claims] 1. When forming a backcoat layer on the surface of the support opposite to the magnetic layer deposition surface, carbon is deposited by vapor deposition on the opposite surface of the support to form a backcoat layer comprising a carbon thin film. Forming a magnetic recording medium. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the vapor deposition is performed by an ECR plasma CVD method. 3. The method of manufacturing a magnetic recording medium according to claim 1, wherein the vapor deposition is performed by arc discharge. 4. The method of manufacturing a magnetic recording medium according to claim 1, including a step of ion-etching the carbon thin film. 5. The method further comprising the step of forming a top coat layer by attaching a lubricant onto the back coat layer.
A method for manufacturing a magnetic recording medium according to any one of 1. 6. A magnetic recording medium having a magnetic layer formed on one surface of a support and a back coat layer formed on the surface opposite to the surface on which the magnetic layer is formed.
A magnetic recording medium, wherein the back coat layer comprises a carbon thin film. 7. The magnetic recording medium according to claim 6, wherein the carbon thin film is a diamond-like carbon thin film. 8. The magnetic recording medium according to claim 6, wherein the carbon thin film is a graphite thin film.