JPH1027329A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the corrosion resistance and durability of a magnetic recording medium and further, to improve the tacky adhesiveness of a magnetic layer and a protective layer by changing the ratio of the carbon-carbon σ bonds in the protective layer comprising a thin film in a range of 1 to 10nm. SOLUTION: The magnetic layer comprising Co and having 1,750Å is formed by a vapor deposition device on a PET film having 6.5μm thickness. Next, the protective layer comprising a diamond-like carbon thin film having 100Å thickness is formed by an ECR plasma CVD method on this magnetic layer. A gaseous mixture composed of benzene, CH4 and Ar is used for gaseous raw materials. The vacuum degree of this time is specified to 4×10<-3> Torr and ECR power to 500W. When the ratio of the formed protective layer is measured by EELS, the ratio of the σ bonds varies at a difference of at least 5% up to 55 to 85% while a spot of 1nm is moved 10nm. The ratio of the σ bonds over the entire part of the protective layer is 60% and the film thickness is 100Å. A lubricative layer is formed thereon.

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, and more particularly, to a protective layer comprising a thin film containing carbon as a main component and having excellent mechanical properties such as durability, corrosion resistance, binding property, and flexibility. The present invention relates to a magnetic recording medium on which is formed.

[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 only a metal adhered to the support, and as such, has poor corrosion resistance and durability. In order to improve this, a fluorine-based material such as perfluoropolyether is used. , A hydrocarbon-based lubricant, or a lubricant using them in combination, or providing a non-magnetic protective layer on a magnetic layer.

[0003] Today, as a protective layer on a magnetic layer,
Attention has been paid to a technique for forming a thin film made of carbon such as diamond-like carbon. It is considered that a diamond-like carbon (DLC) thin film has a structure in which graphite bonds and diamond bonds are mixed. As a method of forming the DLC thin film on the magnetic layer, a method by an RF plasma CVD method, an ECR plasma CVD method, or the like can be used. Among them, the ECR plasma CVD method is a method in which a microwave is applied to a raw material gas in a high vacuum to convert the gas into a plasma and form a thin film on a target object (on a magnetic layer).
It is widely used for forming thin films.

Conventionally, a carbon thin film-based protective layer has been formed mainly for the purpose of further improving the durability. Therefore, a thin film closer to diamond has been formed. That is, various attempts have been made for the purpose of enhancing the diamond bonding property of the DLC thin film, that is, improving the hardness by increasing the ratio of the sp ³ bond (σ bond) to the sp ² bond (π bond). .

[0005]

However, although a DLC thin film having a composition close to that of diamond is certainly excellent in durability, it has poor binding to a magnetic layer, and also causes excessive wear of a video head and poor corrosion resistance. This is sufficient, and the tension of the DLC thin film itself is large, so that the flexibility (flexibility) and running properties of the entire medium are deteriorated. Conversely, a DLC thin film having a composition close to that of graphite has good flexibility, but has poor durability.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, by forming a protective layer with a carbon thin film in which the ratio of σ bonds changes in the film, the durability is improved. It has been found that the binding property, corrosion resistance and flexibility can be improved while maintaining the above, and the present invention has been completed.

That is, the present invention relates to a magnetic recording medium having a support, a magnetic layer formed on the support, and a protective layer formed on the magnetic layer and comprising a thin film containing carbon as a main component. A magnetic recording medium characterized in that the ratio of carbon-carbon σ bonds in the protective layer varies in the range of 1 to 10 nm in the protective layer.

The magnetic recording medium of the present invention has a protective layer made of a thin film containing carbon as a main component formed on a magnetic layer formed on a support by a method such as vapor deposition. In the present invention, a thin film is formed in which the ratio of σ bonds in the thin film changes in the range of 1 to 10 nm in the protective layer. Here, “the ratio of the σ bond changes in the range of 1 to 10 nm” means that an arbitrary spot A in the thin film is selected,
When another spot B that is 1 to 10 nm away from the spot in a random direction is selected, the
This means that the ratio of the coupling is different from the ratio of the σ coupling in the spot B. In this case, from spot A to 1-1
It suffices if there is a spot in which the ratio of the σ bond changes in one place within the range of 0 nm. Further, in the present invention, when the ratio of the σ bond differs by 5% or more, it is determined that “the ratio of the σ bond is different”. For example, in an arbitrary spot A, the ratio of the σ bond is 90%, and in the spot B, the ratio of the σ bond is 10%.
% And the ratio of π bonds are 15%, it can be said that the ratio of σ bonds is different.

In the present invention, the ratio of σ bonds in the thin film can be measured by EELS (electron energy loss spectrum). That is, an arbitrary spot A in the thin film is determined as described above, the peak areas of the σ bond and the π bond at the spot A are measured by EELS, and the ratio (%) of the σ bond is calculated by the following equation.

[0010]

(Equation 1)

[0011] is calculated. Similarly from spot A to 1
EELS for any spot B 10 nm apart
The peak area of the σ bond is measured, and the ratio of the σ bond may be calculated and compared. The direction in which the ratio of the σ bond is measured does not matter. That is, an arbitrary spot is determined, and σ of another spot in an arbitrary direction in a range of 1 to 10 nm from the position is determined.
The ratio of binding may be measured and compared.

In the present invention, the change of the ratio of the σ bond in the thin film containing carbon as a main component may be such that the ratio of the σ bond in the range of 1 to 10 nm is not the same. The ratio of σ bond is
If there is a difference of 5% or more, it may be either increased or decreased.

The ratio between the σ bond and the π bond is an index for predicting the ratio between the diamond property and the graphite property of the DLC film. The DLC film of the present invention is characterized not only in that it has high diamond properties, but that its properties are microscopically changed in the film.

Further, the protective layer of the present invention has a σ
Although the ratio of the bond changes in the protective layer, the ratio of the σ bond preferably changes in the range of 50 to 90%. Further, as a ratio of the entire protective layer, the ratio (average value) of the σ bond is preferably in the range of 50 to 90%, more preferably 55 to 80%.

In the present invention, the thickness of the protective layer composed of a thin film containing carbon as a main component is preferably 50 to 200 °. The protective layer of the present invention is composed of a thin film containing carbon as a main component, and this thin film may contain about 3 to 50 atomic% of hydrogen derived from a raw material gas, and may contain trace amounts of other impurities. May be included.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic recording medium of the present invention
A magnetic layer such as cobalt is deposited on a support by vapor deposition or the like to form a magnetic layer, and a compound serving as a carbon source, for example, methane gas or ethane gas, is introduced into a plasma excitation chamber of an ECR plasma CVD apparatus to activate carbon species. Are generated and adhered on the magnetic layer, whereby the protective layer of the present invention is formed. Here, the ECR plasma CVD method is performed by, for example, an apparatus as shown in FIG. In FIG. 1, 1 is a vacuum vessel, 2 is a cooling can, 3 is a film, 4 is an electromagnet for ECR, 5 is a plasma excitation chamber, 6 is a rectangular waveguide, 7 is a microwave power supply, 8 is a quartz window, 9 Is the power monitor, 1
0 is an isolator, 11 is a three-stub tuner,
Reference numeral 12 denotes a gas flow controller, where A is a microwave and B is a source gas.

The apparatus shown in FIG. 1 is an example of an apparatus for forming a thin film containing carbon as a main component as a protective layer of a vapor deposition type magnetic recording medium. A thin film is formed on the magnetic layer of the formed film 3. In FIG. 1, a diverging magnetic field is formed by the ECR electromagnet (coil) 4 from the plasma excitation chamber 5 toward the vacuum vessel 1. The microwave (A in the figure) of 2.45 GHz guided by the rectangular waveguide 6 connected to the plasma excitation chamber 5 is introduced into the plasma excitation chamber 5 through the quartz window 8. The reaction gas (B in the figure) introduced into the plasma excitation chamber 5 absorbs microwave energy and generates high-density, highly active plasma. Due to the divergent magnetic field generated by the coil 4, ions in the plasma are extracted in the direction of the vacuum vessel 1, irradiated toward the film 3 in the vacuum vessel 1, adhere to the surface of the magnetic layer of the film 3, and contain carbon as a main component. Is formed.

In such an ECR plasma CVD method, a compound containing an element capable of forming a thin film to be formed is supplied to a plasma excitation chamber in a gaseous state. That is,
For example, when forming a thin film mainly composed of carbon, as a raw material compound, a gaseous compound such as methane at normal temperature and normal pressure is used, or a compound such as benzene and gasoline which is liquid at normal temperature and normal pressure. Is gasified by heating. Further, a method in which these are mixed can also be used.

The magnetic layer formed on the support may be of a coating type or a metal thin film type, but is particularly effective in the case of a metal thin film type. The metal thin film serving as the magnetic layer is formed by a usual method such as vapor deposition or sputtering. 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, F
e-Co, Fe-Ni, Co-Ni, Fe-Co-N
i, Fe-Cu, Co-Cu, Co-Au, Co-Y,
Co-La, Co-Pr, Co-Gd, Co-Sm, C
o-Pt, Ni-Cu, Mn-Bi, Mn-Sb, Mn
-Al, Fe-Cr, Co-Cr, Ni-Cr, Fe-
Ferromagnetic alloys such as Co-Cr and Ni-Co-Cr are exemplified. The magnetic layer is preferably an iron thin film or a cobalt thin film. Further, a ferromagnetic alloy mainly composed of one or more of iron, cobalt and nickel and at least one selected from nitrides or carbides thereof are preferable.

For high-density recording, the magnetic layer of the magnetic recording medium is preferably formed on a substrate 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. Although the thickness of the metal thin-film type magnetic layer is not limited, it is preferably 500 to 5000 °, particularly 800 to 30000.
000 ° is preferred. Further, the metal thin film type magnetic layer may have a single layer structure or a multilayer structure.

Further, a back coat layer can be further formed on the surface of the support opposite to the surface on which the magnetic layer is formed. The back coat layer is made of a coating material in which carbon black and / or ceramic fine particles and a binder are dispersed.
It may be formed by coating so as to have a thickness of about 0 μm (after drying), or may be formed by attaching a metal or semimetal to a support by vapor deposition or the like. Various metals can be attached as the back coat layer.
u, Zn, Sn, Ni, Ag and the like and alloys thereof are used, and a Cu-Al alloy is preferable. Furthermore, by performing oxidation, carbonization and nitridation at the time of vapor deposition, an oxide film,
Ceramics such as a carbonized film, a nitrided film and a composite thereof are particularly suitable. The semimetal forming the back coat layer includes Si, Ge, As, S
c, Sb, etc. are used, and Si is preferable. The thickness of the metal thin film type back coat layer is about 0.05 to 1.0 μm.

Further, in the magnetic recording medium of the present invention,
A lubricant layer made of a suitable lubricant may be formed on the protective layer. The lubricant layer may be formed by applying a solution obtained by dissolving a lubricant in an appropriate solvent, or may be formed by spraying the lubricant in a vacuum. When the lubricant is formed by spraying, it is preferable to spray the lubricant onto the magnetic layer formed on the support with a sprayer equipped with an ultrasonic oscillator (hereinafter, referred to as an ultrasonic sprayer). As the lubricant, in either case of application or spraying, a fluorine-based lubricant such as perfluoropolyether is preferable, and specifically, as the perfluoropolyether, one having a molecular weight of 2,000 to 5,000 is suitable. "FOMBLINZ DIAC"
(Carboxyl group modified, manufactured by Montecatini Co., Ltd.),
A commercially available product such as "FOMBLIN Z DOL" (alcohol-modified, manufactured by Montecatini Co., Ltd.) or "Demnum SA" (manufactured by Daikin Industries, Ltd.) can be used. The spray amount of the lubricant may be appropriately determined in consideration of the use of the magnetic recording medium, the type of the lubricant, and the like. The thickness of the formed lubricant layer is about 10 to 200 °.

In the present invention, the material of the support is
Polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonates; polyvinyl chloride; polyimides; The thickness of the support is about 6 to 50 μm.

[0024]

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

Example 1 (1) Production of Magnetic Tape <Formation of Magnetic Layer> A 6.5 μm thick PET film was coated with C
a thickness of 1750 ° [Hc = 1540 (Oe),
Bs = 6100 (G)]. here,
The Co magnetic layer was formed by the vapor deposition device shown in FIG. 2, 21 is a film, 22 is an unwinding roll, 23
Is a can roll, 24 is a take-up roll, 25 is a bombardment treatment means, 26 and 26 'are expander rolls, 27
Is an oxygen gas inlet tube, 28 is a shielding plate for regulating the region of metal vapor, 29 is an electron gun, and 30 is a crucible. These are arranged in a vacuum vessel (not shown), and the inside of the vacuum vessel is maintained at a degree of vacuum of about 1 × 10 ^{−4 to} 5 × 10 ⁻⁷ Torr. The film 21 is conveyed from the unwind roll 22 to the take-up roll 24 via the can roll 23 (running speed of the film 10 m / min). An electron beam is irradiated from an electron gun 29 onto Co contained in the crucible 30 to vaporize Co, and C is applied to the film 21 conveyed on the can roll 23.
A magnetic layer made of o was formed. Further, oxygen gas was introduced (300 SCCM) from the oxygen gas introduction pipe 27 into the deposition region to oxidize the Co surface.

<Formation of Protective Layer> Next, a diamond-like carbon (DLC) having a thickness of 100 ° was formed on the magnetic layer by ECR plasma CVD using the apparatus shown in FIG.
A protective layer composed of a thin film was formed. Source gas is benzene (25 SCCM), CH ₄ (5 SCCM), Ar (3S
CCM). At this time, the degree of vacuum was 4 × 10 ⁻³ Torr, and the ECR power was 500 W.
The ratio of the σ bond of the formed protective layer was measured by EELS.
The percentage of binding varied from 55 to 85% with a difference of at least 5%. The ratio (average value) of the σ bond in the entire protective layer was 60%, and the film thickness was 100 °.

<Formation of Lubricating Layer and Back Coat Layer> Further, a perfluoropolyether having a -OH group as a polar group (Demnum SA: manufactured by Daikin Industries) on the protective layer is adjusted to a thickness of 20 mm. To form a lubricant layer. A back coat layer was formed on the surface of the film opposite to the surface on which the magnetic layer was formed. The back coat layer is 2
A binder containing carbon having a diameter of 0 to 30 nm was applied to a film such that the thickness after drying became 0.5 μm, and the film was dried. The magnetic layer obtained above,
The film on which the DLC protective layer, the fluorine-based lubricating layer and the back coat layer were formed was cut into a width of 8 mm, and was loaded on a cassette case to obtain an 8 mm video tape.

(2) Performance Evaluation The 8 mm video tape obtained above was evaluated for durability and
The binding properties and corrosion resistance were evaluated by the following methods. Table 1 shows the results. Durability Durability was measured using a commercially available Hi8-VTR with the 8 m
m video tape was set, and the output was evaluated in terms of a decrease (dB) after being reproduced in the still mode for 10 hours. Binding Property The binding property was evaluated by a scratch test using a scratch tester (SST-101, manufactured by Shimadzu Corporation). The condition at this time is that the cartridge tip diameter is 10 μm.
m, full-scale load 196 mN, load speed 1 μm /
s, amplitude 50 μm, and feed rate 20 μm / s. Under this condition, when the film was scratched (scratched) under a constant instruction, the load until the film was broken was measured, and an average value of five measurements was obtained.

Corrosion resistance The corrosion resistance was measured by using the above-prepared 8 mm video tape for 70 minutes.
Evaluation was made based on the deterioration rate of the saturation magnetic flux density (Bs) after being left for one week under the condition of 85 ° C. and 85% RH.

Example 2 In Example 1, the source gases for forming the protective layer were gasoline (30 SCCM), CH ₄ (6 SCCM), Ar
(5SCCM) mixed gas and ECR plasma C
The degree of vacuum when performing the VD method is 8 × 10 ⁻³ Torr, and the ECR is
An 8 mm video tape was produced in the same manner except that the power was changed to 600 W, and the same evaluation as in Example 1 was performed. .
Table 1 shows the results. In the protective layer formed in this example, while moving the spot of 1 nm by 10 nm, the ratio of the σ bond varied from 50 to 90% with a difference of at least 5%. The ratio (average value) of the σ bond in the entire protective layer was 70%, and the film thickness was 150 °.

Example 3 <Formation of Magnetic Layer> Two magnetic layers each composed of Co [thickness of each layer = 1000 °, all magnetic layers] on a 4.5 μm thick PEN film using the apparatus of FIG. Hc of 160
0 (Oe), Bs of all magnetic layers = 5800 (G)]. At the time of vapor deposition, as in Example 1, an oxygen-oxygen gas was introduced into the vapor deposition region (300 SCCM) to oxidize the Co surface of each magnetic layer.

<Formation of Protective Layer> Next, an ECR plasma CVD method using the apparatus shown in FIG.
120mm thick diamond-like carbon (DL
C) A protective layer composed of a thin film was formed. The source gas is benzene (100 SCCM), and the degree of vacuum at this time is 1 × 1
0 ^-4 Torr and ECR power were set to 600W. When the ratio of the σ bond of the formed protective layer was measured by EELS, the ratio of the σ bond fluctuated by at least 5% from 55 to 75% while moving the 1 nm spot by 10 nm. Further, the ratio (average value) of the σ bond of the entire protective layer was 65%.

<Formation of Lubricating Layer and Backcoat Layer> Further, a perfluoropolyether having a -OH group which is a polar group (Demnum SA: manufactured by Daikin Industries, Ltd.) was formed on the protective layer to a thickness of 20 mm. To form a lubricant layer. A back coat layer was formed on the surface of the film opposite to the surface on which the magnetic layer was formed. The back coat layer is 2
A binder containing carbon having a diameter of 0 to 30 nm was applied to a film such that the thickness after drying became 0.5 μm, and the film was dried.

The two magnetic layers, DL, obtained as described above
The film on which the C protective layer, the fluorine-based lubricating layer and the back coat layer were formed was cut into a width of 8 mm, and was loaded into a cassette case to obtain an 8 mm video tape. The same evaluation as in Example 1 was performed using this 8 mm video tape. Table 1 shows the results.

Comparative Example 1 In Example 1, the source gas used when forming the protective layer was C
A mixed gas of H ₄ (40 SCCM) and H ₂ (10 SCCM) was used, and the degree of vacuum when performing ECR plasma CVD was 5
Example 1 An 8 mm video tape was prepared in the same manner as in Example 1 except that × 10 ^-2 Torr and ECR power were set to 400 W.
The same evaluation was performed. Table 1 shows the results. In addition,
In the protective layer formed in Comparative Example 1, a 1-nm spot
During the movement of 0 nm, the ratio of the σ bond was almost constant at 41 to 44%. The ratio of the σ bond in the entire protective layer was 42%, and the film thickness was 100 °.

Comparative Example 2 In Comparative Example 1, the source gas for forming the protective layer was C
₂ H ₂ (acetylene) gas (70 SCCM), base film heated to 80 ° C., and ECR plasma CVD
An 8 mm video tape was produced in the same manner as in Example 1 except that the degree of vacuum at the time of performing the method was 3 × 10 ⁻² Torr and the ECR power was 450 W, and the same evaluation as in Example 1 was performed. Table 1 shows the results. In the protective layer formed in Comparative Example 2, the ratio of the σ bond was almost constant at 68 to 72% while moving the spot of 1 nm by 10 nm. The ratio (average value) of the σ bond in the entire protective layer was 70%, and the film thickness was 150 °.

[0037]

[Table 1]

[0038]

As described above, according to the present invention, it is possible to obtain a magnetic recording medium which is excellent in durability and corrosion resistance and has good binding to a magnetic layer.

[Brief description of the drawings]

FIG. 1 shows an ECR plasma CV for forming a carbon thin film.
Schematic diagram showing an example of the D device

FIG. 2 is a schematic view showing an example of a vapor deposition apparatus for forming a magnetic layer.

[Explanation of symbols]

 2 Can roll 3 Film 4 Electromagnet for ECR 6 Rectangular waveguide 7 Microwave power supply 8 Quartz window A Microwave B Raw material gas 21 Film 23 Can roll 27 Oxygen gas inlet tube 28 Shielding plate 29 Electron gun 30 Crucible

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hirohide Mizunoya 2606 Kabane-cho, Akaga, Tochigi Pref.Katsumi Endo 2606 Kaiga-cho, Akabane, Haga-gun, Tochigi

Claims (6)

[Claims] 1. A magnetic recording medium comprising a support, a magnetic layer formed on the support, and a protective layer formed on the magnetic layer and comprising a thin film containing carbon as a main component. Ratio of carbon-carbon σ bond in the protective layer is 1
A magnetic recording medium characterized by being changed in a range of from 10 nm to 10 nm. 2. The method according to claim 1, wherein the ratio of the σ bond in the protective layer is 50 to 9
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium varies within a range of 0%. 3. The magnetic recording medium according to claim 1, wherein the ratio (average value) of the σ bond of the entire protective layer is 50 to 90%. 4. The magnetic recording medium according to claim 1, wherein said protective layer is formed by ECR plasma CVD. 5. The magnetic recording medium according to claim 1, wherein said protective layer has a thickness of 50 to 200 °. 6. The magnetic recording medium according to claim 1, wherein the magnetic layer is a metal thin film type magnetic layer.