JPH11161947A - Production of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a medium by subjecting a thin film surface to irradiation with ions right after the formation of the thin, thereby forming a hard thin film at the time of forming a protective layer of a carbon thin film on a magnetic layer. SOLUTION: The film 3 which is formed with the magnetic layer and travels on a cooling can 2 in a vacuum vessel 1 is irradiated with the active species in plasma in the divergent magnetic field generated by a coil 4, by which the carbon thin film is formed on the surface of the magnetic layer. At this time, a power source 15 is connected to a feed roll 14 and voltage is impressed on the traveling film 3 to accelerate the plasma particles and to form the harder thin film. The thin film surface deposited by a plasma CVD method is uniformly irradiated ions by a Kaufman type ion gun 13 as dry etching after the deposition of the thin film. The etching of the soft component in the thin film is made possible by this irradiation with the ions without exertion of influence on the film formed by the ions in raw material gases and, therefore, the formation of the hard thin film is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a magnetic recording medium including a step of forming various thin films such as a carbon thin film on a magnetic layer by a plasma CVD method.

[0002]

2. Description of the Related Art A so-called metal thin film type magnetic recording medium in which a metal is deposited on a support in a vacuum in a vacuum or the like can increase the density of the magnetic material because the magnetic layer contains no binder at all. Is promising for high-density recording.

However, the magnetic layer of the metal thin-film type magnetic recording medium has poor corrosion resistance and durability as it is because the metal is only deposited on the support. It has been practiced to apply an acid-based or fluorine-based lubricant or to provide a protective layer of a non-magnetic metal on a magnetic layer.

Furthermore, today, as a protective layer on a magnetic layer,
2. Description of the Related Art Formation of carbon thin films such as diamond-like carbon and thin films composed of various carbides, nitrides, and oxides such as silicon carbide, boron nitride, silicon nitride, silicon oxide, and aluminum oxide have been performed. Above all, a carbon thin film such as diamond-like carbon is particularly excellent in hardness and sliding characteristics, and is attracting attention as a protective thin film of a magnetic recording medium. For example, Japanese Patent Application Laid-Open No. 53-143206 discloses a magnetic disk having a surface provided with a film containing carbon as a main component.

As a method of forming a carbon thin film such as diamond-like carbon, for example, ion beam evaporation, ion beam sputtering, RF sputtering, RF glow discharge, DC-discharge, microwave plasma CVD
Methods, a hot filament CVD method, a hot plasma CVD method and the like are known.
Method D is suitable as a method for forming a protective layer of a magnetic recording medium because film formation can be performed at a relatively low substrate temperature.

Among the plasma CVD methods using microwaves, the ECR (Electron Cyclotron Resonance) plasma CVD method uses a microwave (2.45 GHz) from a microwave source as a waveguide in a plasma excitation chamber. In this method, the source gas introduced into the plasma excitation chamber is dissociated, and a target substance is deposited on the substrate as active species. The ECR plasma CVD method uses a magnetic field and microwaves to satisfy ECR conditions, and thus can generate stable high-density plasma. for that reason,
Various thin films can be formed at a low pressure (high vacuum) without lowering the plasma density as compared with conventional high-frequency plasma or microwave plasma. This ECR plasma CVD method
As a technique for forming a carbon thin film such as diamond-like carbon on a base material, attention has been paid to a more useful method.

[0007]

Generally, when a protective film made of a carbon thin film is formed on a magnetic layer, it is intended to form a carbon film having higher hardness. For example, in the ECR plasma CVD method, a gas such as argon or nitrogen is mixed into a raw material gas to generate ions thereof, and soft components such as graphite in a carbon thin film and a polymer derived from the raw material gas are formed by an ion assist effect. Is etched to form a thin film having a large amount of hard components.

However, if another gas is mixed with the source gas, the ions of the source gas contributing to film formation collide with the ions of the other gas before reaching the substrate, lose energy, and deposit on the substrate. The amount decreases and a dense thin film cannot be obtained. As a result, it becomes difficult to impart sufficient durability to the magnetic recording medium.

[0009]

Means for Solving the Problems The present inventors have developed a method for obtaining a more durable magnetic recording medium when a protective layer such as a carbon thin film is formed on a magnetic layer by ECR plasma CVD. Various studies have been conducted to provide the thin film. By irradiating the surface of the thin film with ions immediately after the formation of the thin film, the soft component can be etched without affecting the film formation by the ions of the raw material gas. It was found that a thin film was formed and a magnetic recording medium having excellent durability was obtained, and the present invention was completed.

That is, the present invention relates to a method for manufacturing a magnetic recording medium including a step of forming a thin film on a magnetic layer formed on a support by a plasma CVD method, wherein the surface of the thin film is irradiated with ions immediately after the formation of the thin film. And a method of manufacturing a magnetic recording medium.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a thin film is formed on a magnetic layer formed on a support by a plasma CVD method.
Such a plasma CVD method includes ECR plasma CV
Method D is particularly preferred. The ECR plasma CVD method is performed by, for example, an apparatus as shown in FIG. In FIG. 1, 1
Is a vacuum container, 2 is a cooling can, 3 is a film, 4 is EC
R electromagnet, 5 is a plasma excitation chamber, 6 is a rectangular waveguide, 7
Is a microwave power supply, 8 is a quartz window, 9 is a power monitor, 10 is an isolator, 11 is a matching device (three stub tuner), and 12 is a gas flow controller. Microwave A is generated by a microwave power source 7,
The rectangular waveguide 6 advances in the direction shown. Then, it is introduced into the plasma excitation chamber 5 through the quartz window 8 and contributes to the generation of plasma. The inside of the vacuum vessel 1 is 1.2 × 10 ⁻¹ to 1.2 × ¹ by a vacuum exhaust system (not shown).
The degree of vacuum is maintained at about 0 ^-6 Torr.

The apparatus shown in FIG. 1 is an example of an apparatus for forming a carbon thin film as a protective layer of a vapor-deposited magnetic recording medium, and a film 3 on which a magnetic layer running on a cooling can 2 in a vacuum vessel 1 is formed. A carbon thin film is formed on the magnetic layer. FIG.
In, a diverging magnetic field is formed from the plasma excitation chamber 5 toward the vacuum vessel 1 by the ECR electromagnet (coil) 4. The 2.45 GHz microwave (A in the figure) guided by the rectangular waveguide 6 connected to the plasma excitation chamber 5 is:
It is introduced into the plasma excitation chamber 5 through a quartz window 8. The reaction gas (B in the figure) introduced into the plasma excitation chamber 5 is collided with the electromagnet and electrons accelerated by the microwave at a high speed (the electrons are accelerated at a high speed by the resonance of the cyclotron motion and the microwave vibration in the magnetic field). , High-density, highly active active ion species. Here, as the gas serving as the carbon source, saturated hydrocarbons such as methane and ethane, unsaturated hydrocarbons such as ethylene and acetylene, and aromatic hydrocarbons such as benzene and toluene can be used, as long as the reaction is not impaired. Aromatic hydrocarbons having a functional group such as benzaldehyde can also be used. From the viewpoint of film quality, it is particularly preferable to use one or more of unsaturated hydrocarbons or aromatic hydrocarbons. These are because the raw material gas is efficiently decomposed because of having an unsaturated bond, and a hard carbon protective film is easily obtained. Alternatively, a solution obtained by dissolving a hydrocarbon at room temperature such as naphthalene or anthracene in a suitable solvent such as benzene or toluene may be used as a gas. Due to the diverging magnetic field generated by the coil 4, active species in the plasma are drawn out toward the vacuum vessel 1 and irradiated toward the film 3 in the vacuum vessel 1, and adhere to the surface of the magnetic layer of the film 3 to form a carbon thin film. It is formed.

In the present invention, ECR plasma CVD
In the method, it is preferable to apply an accelerating voltage to the support. In this method, since the plasma particles are accelerated and reach the support, a harder thin film can be formed. Specifically, as shown in FIG. 1, when a voltage is applied by connecting the power supply 15 to the feed roll 14, the voltage is also applied to the support 3 running on the can roll 2. Acceleration voltage is 1
It is preferably 00 to 400 V, and its frequency is preferably 20 kHz or less (including direct current).

The present invention is characterized in that the surface of the thin film is dry-etched after the formation of the thin film. Dry etching is a method in which etching gas is discharged and decomposed, and etching is performed using generated radicals and ions. A physical method (sputter etching, ion beam etching) using a sputtering effect by ion bombardment, and a method of etching with a material to be etched. Chemical methods by generating volatile compounds through chemical reactions (cylindrical plasma etching, plasma-separated microwave plasma etching), and physicochemical methods using the interaction of ions and radicals with the material to be etched (reaction Reactive etching, microwave plasma etching, high-density plasma etching, and reactive ion beam etching). In the present invention, a physical method using a method by ion irradiation is particularly preferable. Specifically, ion irradiation using an ion gun is preferable.

In the present invention, ions are irradiated on the surface of the thin film as dry etching after the formation of the thin film. Here, “after film formation” usually means immediately after film formation, but from the viewpoint of production efficiency, it is preferable to perform ion irradiation between film formation and winding.

Irradiation with ions may be performed according to the so-called physical dry etching method described above, but it is preferable to use an ion gun. As the ion gun, a Kauffman-type ion gun is preferable. In the apparatus of FIG. 1, irradiation of thermoelectrons by a Kauffman-type ion gun 13 is performed. FIG. 2 shows an example of the configuration of a Kauffman-type ion gun. The ion gun shown in FIG. 2 has a gas nozzle 28 into which nitrogen gas or the like is introduced.
And a cathode filament 22 that emits thermoelectrons in the discharge chamber 21. The cathode filament 22 is generally made of tungsten. The thermoelectrons emitted from the cathode filament 22 are accelerated by the anode 23 and collide with the gas introduced from the gas nozzle 28 to ionize gas molecules. When nitrogen gas is used, the thus ionized nitrogen ions having a positive charge are focused by the screen grid 24 to which a positive potential is applied, extracted and accelerated by an accelerator grid 25 to which a negative potential is applied, and are accelerated to a thin film. Pointed at. In FIG. 2, reference numeral 26 denotes a magnet for efficiently maintaining a plasma in the discharge chamber 21, and 27 denotes a nutrizer, which is a space charge of an ion beam due to thermoelectrons emitted from a filament. This is for achieving convergence by suppressing the effect.

When a Kauffman-type ion gun is used, the operating conditions are not limited, but examples of a gas serving as an ion source include nitrogen gas, argon gas, and oxygen gas.
The current applied to the filament is 3 to 24 A, and the acceleration voltage is 1
00 to 400 V, and the discharge voltage is 10 to 100 V.

Preferably, the ions are uniformly irradiated on the surface of the thin film formed by the plasma CVD method. The soft component in the thin film is etched by the ion irradiation, so that a hard thin film can be formed.

The thickness of the thin film formed on the magnetic layer is
In the case of a carbon thin film, the thickness is about 5 to 20 nm, and it is desirable to select the conditions of the ECR plasma CVD method, the raw material compound, the traveling speed, and the like according to this.

The magnetic layer formed on the support is preferably a metal thin film type magnetic layer. Examples of the magnetic material for forming the metal thin film type magnetic layer include ferromagnetic metal materials used in the manufacture of ordinary metal thin film type magnetic recording media, for example, ferromagnetic metals such as Co, Ni, and Fe, Fe-C
o, Fe-Ni, Co-Ni, Fe-Co-Ni, Fe
-Cu, Co-Cu, Co-Au, Co-Y, Co-L
a, Co-Pr, Co-Gd, Co-Sm, Co-P
t, Ni-Cu, Mn-Bi, Mn-Sb, Mn-A
1, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co
Ferromagnetic alloys such as -Cr and Ni-Co-Cr; Further, nitrides, carbides, and oxides of these metals or metal alloys are also preferable.

For high-density recording, the magnetic layer of the magnetic recording medium is preferably formed on a support by oblique evaporation. The method for oblique deposition is not particularly limited, and follows a conventionally known method. The degree of vacuum at the time of vapor deposition is 10 ^-4 to 10 ^-7 Torr
It is about. The magnetic layer formed by vapor deposition may have either a single layer structure or a multilayer structure. In particular, by introducing an oxidizing gas to form an oxide on the surface of the magnetic layer, the durability can be improved.

In the present invention, the magnetic layer may be a single layer or a multilayer. When the number of magnetic layers is one, the thickness is preferably 10 to 300 nm. In the case of forming a multilayer magnetic layer, the thickness of the lower magnetic layer is 10 to 200 nm and the thickness of the upper magnetic layer is 5 to 200 n in two layers.
m is preferable, and the thickness of the lower magnetic layer is 10 to 10 in the three layers.
Preferably, the thickness of the intermediate magnetic layer is 200 nm, and the thickness of the upper magnetic layer is 5 to 100 nm. Also,
Although the number of magnetic layers may be large, two to five layers are considered suitable as a practical range.

As the support, polyethylene terephthalate (PET), polyethylene naphthalate (P
Polyesters such as EN); polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonates; polyvinyl chloride; polyimides; The thickness of these supports is about 3 to 50 μm.

Further, a back coat layer may be formed on the surface of the support opposite to the surface on which the magnetic layer is formed. The back coat layer may be a coating type back coat layer having a thickness of about 0.2 to 1.0 μm containing carbon black or a binder as a main component, or a vapor deposition method, a DC sputtering method, an AC sputtering method, a high frequency sputtering method, A metal thin film type back coat layer formed by depositing a metal or metalloid on a support in a vacuum by a plating means such as a DC magnetron sputtering method, a high-frequency magnetron sputtering method, or an ion beam sputtering method may be used. In the latter case, various metals may be attached as the back coat layer, but Al, Cu, Zn, Sn,
Ni, Ag, Co and the like and alloys thereof are used.
1, Co and Cu-Al alloys are preferred. Further, ceramics such as an oxide film and a carbonized film which have been subjected to an oxidation reaction, a carbonization reaction, and the like at the time of vapor deposition are also suitable. Further, as the semimetal forming the back coat layer, Si, Ge, A
s, Sc, Sb, etc. are used, and Si is preferred. It is preferable to further dope an additive to improve the conductivity. The thickness of the metal thin film type back coat layer is set to 0.1.
It is about 0.5 to 1.0 μm.

In the present invention, it is preferable that after forming a thin film on the magnetic layer by ECR plasma CVD, a lubricant layer made of a suitable lubricant is formed on the thin film. As the lubricant, a paint of a fluorine-based lubricant such as perfluoropolyether is particularly preferable, and the thickness of the lubricant layer is about 5 to 100 nm. As the fluorine-based lubricant, for example, HOOC-CF ₂ (OC ₂
Carboxyl-modified perfluoropolyether such as F ₄ ) _p (OCF ₂ ) _q -OCF ₂ COOH, F- (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ CF ₂ COOH, HO
An alcohol-modified perfluoropolyether such as CH ₂ -CF ₂ (OC ₂ F ₄ ) _p (OCF ₂ ) _q -OCF ₂ -CH ₂ OH,
Alternatively, a saturated hydrocarbon group such as an alkyl group, an unsaturated hydrocarbon group, an aromatic hydrocarbon group, or a group partially attached with another functional group may be used. Molecular weight 50
Those having 0 to 50,000, particularly 500 to 4000, are preferred. Specifically, the product name “FOMB” of Montecatini
LIN Z DIAC "and the product name" FOMBLIN Z
DOL ", a brand name of Daikin Industries, Ltd." Demnum SA "
Etc. In the present invention, the above lubricant layer may be formed on the back coat layer.

The manufacturing method of the present invention uses the ECR plasma CV
Except for irradiating the surface of the thin film with ions after the formation of the thin film by the method D, it is possible to conform to a normal method for manufacturing a magnetic recording medium.

The present invention includes a step of forming a thin film on a magnetic layer by a plasma CVD method and then increasing the hardness of the thin film surface. As a specific means, the thin film surface is irradiated with ions or the like. Is etched.

[0028]

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

Examples 1 to 5 and Comparative Examples 1 to 2 A magnetic layer made of Co was formed on a 6.0 μm thick PET film by a continuous vacuum oblique deposition method (film thickness: 1).
80 nm). Next, a 12 nm thick DLC (diamond-like) was formed on the magnetic layer by using an ECR-CVD method using a microwave using the apparatus shown in FIG. A protective layer composed of a (carbon) thin film was formed. At this time, the surface of the DLC thin film was irradiated with ions under the conditions shown in Table 1 immediately after the formation of the DLC thin film (Examples 1 to 5). In Comparative Examples 1 and 2, ion irradiation was not performed. In Examples 3 to 5 and Comparative Example 2, a bias voltage was applied to the support under the conditions shown in Table 1.

A back coat layer made of carbon black and a binder is formed on the surface of the PET film opposite to the surface on which the magnetic layer is formed, by applying a coating having a thickness of 0.5 μm,
Further, a 4 nm-thick lubricating layer made of a fluorine-based lubricant (trade name “FOMBLIN Z DOL”, manufactured by Montecatini Co.) was formed on the protective layer. The obtained film was cut into a width of 8 mm, and was loaded into a cassette case.
mm cassette tape was obtained. The still durability of this 8 mm cassette tape was evaluated by the following method. Table 2 shows the results.

<Still Durability> The still durability was determined by using a commercially available 8 mm VTR (model EV-S900, manufactured by Sony Corporation) and measuring the time required for the output to decrease by 3 dB from the initial value.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

According to the present invention, a hard thin film can be formed on a magnetic layer without impairing the film forming property by the plasma CVD method, so that a more durable magnetic recording medium can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a schematic sectional view showing the structure of a Kaufman-type ion gun.

[Explanation of symbols]

 1: vacuum container 2: cooling can 3: film 4: electromagnet for ECR 5: plasma excitation chamber 6: rectangular waveguide 7: microwave power supply 11: matching device (three stub tuner) 13: Kaufman type ion gun A: micro Wave B: Raw material gas

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshio Yamazaki 2606 Akabane, Kaiga-cho, Haga-gun, Tochigi Pref.

Claims (6)

[Claims] 1. A method for manufacturing a magnetic recording medium, comprising: forming a thin film on a magnetic layer formed on a support by a plasma CVD method, wherein the thin film surface is dry-etched after the thin film is formed. Of manufacturing a magnetic recording medium. 2. A method for manufacturing a magnetic recording medium, comprising a step of forming a thin film on a magnetic layer formed on a support by a plasma CVD method, wherein the surface of the thin film is irradiated with ions after the formation of the thin film. A method for manufacturing a magnetic recording medium. 3. The method for manufacturing a magnetic recording medium according to claim 2, wherein the ion irradiation is performed by an ion gun. 4. A plasma CVD method by applying a voltage to a support.
4. The method for manufacturing a magnetic recording medium according to claim 2, wherein the method is performed. 5. The method according to claim 1, wherein the plasma CVD method is an ECR plasma CV.
The method for producing a magnetic recording medium according to claim 1, wherein the method is D method. 6. The method for manufacturing a magnetic recording medium according to claim 1, wherein the thin film is a carbon thin film.