JPH103650A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the weatherability and reliability of a magnetic recording medium and to enable the long-term preservation of the magnetic recording medium by reforming the surface of a protective film by the plasma of silicon and fluorine and forming silicon-fluorine on the surface. SOLUTION: The magnetic recording medium 10 is formed with a magnetic layer 2 by a physical vapor growth PVD technique for evaporating ferromagnetic metallic materials, such as Fe and Co, by heating under vacuum to directly deposit this materials on one surface of a base film 1. The surface thereof is provided with the protective film 3 consisting of a gaseous mixture composed of gaseous siloxane and gaseous hydrogen carbonate as a raw material. Next, the surface thereof is subjected to the reforming of the surface of the protective film 3 by the plasma obtd. by converting silicon and fluorine to plasma to form a reformed part 4. The opposite surface of the base film 1 is provided with a back coating layer. The siliconfluorine are formed on the surface of the protective film obtd. by reforming the surface of the protective film consisting essentially of carbon with the silicon and fluorine in such a manner, by which the weatherability and reliability of the magnetic recording medium are improved and the utilization to the magnetic recording medium requiring long-term preservation is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium having a carbon protective film formed on a magnetic layer and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a powder magnetic material such as an oxide magnetic powder or an alloy magnetic powder has been coated on a non-magnetic support by a vinyl chloride-vinyl acetate copolymer, a polyester resin, a urethane resin, or a polyurethane. 2. Description of the Related Art A coating type magnetic recording medium produced by applying a magnetic paint dispersed in an organic binder such as a resin and drying the same is widely used.

On the other hand, with the growing demand for high-density magnetic recording, Co-Ni alloys, Co-Cr alloys,
-O or the like, a metal magnetic material is subjected to plating or vacuum thin film forming means (vacuum vapor deposition method, sputtering method, ion plating method, etc.) to form a polyester film or polyamide,
A so-called metal magnetic thin film type magnetic recording medium directly attached on a non-magnetic support such as a polyimide film has been proposed and attracted attention.

The magnetic recording medium of the metal magnetic thin film type is excellent in coercive force and squareness, and has a very small thickness of the magnetic layer. In addition to this, there are many advantages such as the fact that there is no need to mix the binder, which is a nonmagnetic agent, into the magnetic layer, so that the packing density of the magnetic material can be increased. That is, the magnetic recording medium of the metal magnetic thin film type is considered to be the mainstream of high-density magnetic recording due to its superior magnetic properties.

[0005] Further, in order to improve the electromagnetic conversion characteristics of this type of magnetic recording medium and to obtain a larger output, when forming the magnetic layer of the magnetic recording medium, the magnetic layer is inclined. The so-called oblique vapor deposition for vapor deposition has been proposed and put to practical use.

[0006] In the future, recording media tend to be smoothed in order to reduce spacing loss from the trend of higher density. With the smoothing of the recording medium, the frictional force between the magnetic head and the recording medium increases, and the shear stress generated on the recording medium increases. Under the situation where the demand for the sliding durability becomes strict, a technique for forming a protective film layer on the surface of the magnetic layer has been studied for the purpose of improving the durability.

As such a protective film, a carbon film,
Quartz (SiO ₂ ) films, zirconia (ZrO ₂ ) films and the like have been studied, and some hard disks have been put to practical use and produced. Especially recently in carbon films,
The formation of a film such as a so-called diamond-like carbon (DLC) film, which is a harder film, has also been studied, and is a protective film that is expected to become mainstream in the future. As a method for forming the DLC film, a sputtering method or a CVD method is used.

In the sputtering method, first, an inert gas such as an argon gas is ionized, that is, turned into a plasma using an electric field or a magnetic field. Further, by accelerating the ionized argon ions, the atoms of the target are repelled by their kinetic energy. Then, the ejected atoms are deposited on the opposing substrate to form a target thin film. The DLC film formed by this process is a forming means slightly inferior in productivity because its formation speed is generally slow.

On the other hand, the CVD method is a chemical process of forming a film by making a chemical reaction such as decomposition and synthesis of a base material as a raw material by using energy of plasma generated by using an electric or magnetic field. .

[0010]

However, while the sliding durability is remarkably improved by the carbon film formed by these methods, a problem remains in the environmental resistance, particularly the corrosion resistance. In a high-temperature and high-humidity environment or in a corrosive atmosphere such as SO ₂ gas, the magnetic properties of the magnetic layer decrease due to oxidation and sulfidation, and in the worst case, the properties as a magnetic recording medium are lost. Will be done. Therefore, the carbon protective film is required to have not only sliding resistance but also environmental resistance.

In order to solve the above problems, the present invention provides a magnetic recording medium suitable for long-term storage by improving the environmental resistance of a carbon protective film formed on a magnetic layer. is there.

[0012]

According to the present invention, a surface of a protective film containing carbon as a main component formed on a magnetic layer of a magnetic recording medium is modified with silicon and fluorine.

According to the configuration of the present invention described above, since the surface of the protective film is modified with silicon and fluorine,
The protective film has anticorrosion properties, and can improve the environmental resistance of the protective film in a high-temperature and high-humidity environment or a corrosive atmosphere such as SO ₂ gas.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In a magnetic recording medium according to the present invention in which a magnetic layer is provided on one surface of a non-magnetic support and a protective film containing carbon as a main component is formed on the magnetic layer, It is configured to be modified with silicon and fluorine.

Further, according to the present invention, in the above magnetic recording medium, carbon and silicon are contained in a material of the protective film.

Further, according to the present invention, in the above magnetic recording medium, as a material for the protective film, a mixture of a hydrocarbon-based material and a siloxane-based material is used, and the mixture is reformed with a fluorine compound plasma gas. And

Further, according to the present invention, in the above magnetic recording medium, the siloxane raw material is hexamethyldisiloxane or octamethylcyclotetrasiloxane.

The present invention also provides the magnetic recording medium, wherein the fluorine compound is CF ₄ , CHF ₃ , SF ₆ , N
The structure is at least one of F ₃ , BF ₃ , and C ₂ F ₄ .

Hereinafter, embodiments of a magnetic recording medium of the present invention and a method of manufacturing the same will be described with reference to the drawings. The magnetic recording medium 10 shown in FIG. 1 has a base film 1 as a non-magnetic support.
A magnetic layer 2 is formed on one surface of the base film 1, and a protective film 3 is formed on the magnetic layer 2 to protect the magnetic layer 2. On the side of the base film 1 opposite to the side on which the magnetic layer 2 is formed, And the back coat layer 5 is formed. Then, the surface of the protective film 3 is modified by silicon and fluorine to form the modified portion 4.

A ferromagnetic metal material is directly applied on the base film 1 to form a metal magnetic thin film on the magnetic layer 2.
The metal magnetic material is formed as
Any material may be used as long as it is used for a normal evaporation tape. For example, Fe, Co, Ni
Ferromagnetic metals such as Fe-Co, Co-O, Fe-Co-
Ni, Fe-Cu, Co-Cu, Co-Au, Co-P
t, Mn-Bi, Mn-Al, Fe-Cr, Co-C
r, Ni-Cr, Fe-Co-Cr, Co-Ni-C
r, a ferromagnetic alloy such as Fe-Co-Ni-Cr. These may be a single-layer film or a multilayer film. Further, an underlayer or an intermediate layer may be provided between the nonmagnetic support and the metal magnetic thin film, or in the case of a multilayer film, to improve the adhesion between the layers and to control the coercive force.

The means for forming the metal magnetic thin film constituting the magnetic layer 2 includes a vacuum evaporation method in which a ferromagnetic material is heated and evaporated under vacuum and deposited on a non-magnetic support, or a method in which the evaporation of the ferromagnetic metal material is performed by discharging. A so-called PVD (Physical Vapor Deposition) technique, such as an ion plating method performed in an atmosphere, a sputtering method in which glow discharge is caused in an atmosphere containing argon as a main component, and an atom on a target surface is beaten by argon ions generated. .

The protective film 3 contains carbon as a main component, and is formed on the magnetic layer 2 by the sputtering method or the CVD method as described above.

The surface of the protective film 3 is modified by silicon and fluorine. More preferably, carbon and silicon are contained in the raw material of the protective film 3 in advance, and the surface is modified by using a gas containing fluorine.
In this case, as a material of the protective film 3, for example, a siloxane-based gas such as hexamethyldisiloxane or octamethylcyclotetrasiloxane, or a mixture of a hydrocarbon gas and a siloxane-based gas can be used.

Examples of the fluorine-containing gas include CF ₄ ,
CHF ₃ , SF ₆ , NF ₃ , BF ₃ , C ₂ F _{4 and the} like can be used. Then, the fluorine-containing gas is converted into, for example, plasma, and the surface of the protective film 3 can be modified by the plasma.

Next, the magnetic recording medium 10 having the structure shown in FIG. 1 was actually manufactured, and various characteristics were measured.

Example 1 First, a PET film having a thickness of 10 mm was prepared as the base film 1. Next, the base film 1 is coated with Co ₁₀₀ by oblique evaporation.
Was formed into a single layer having a thickness of 200 nm. The oblique deposition conditions at this time were as follows. Introduced gas: oxygen gas Degree of vacuum: 2 × 10 ^-2 Pa Incident angle: 45 to 90 °

Next, using the plasma processing apparatus 21 shown in FIG. 2, formation of the protective film 3 and its plasma processing were performed. The plasma processing apparatus 21 has a vacuum evacuation system 20 for evacuating the entire processing tank, and includes therein an unwinding roll 13 and a winding roll 14 for winding a film 11 to be processed, and a moving film 11. Rotary support 1 to support
2. A drum-shaped counter electrode 19 for supporting the film 11 when performing the process, a reaction tube 15 for forming the protective film 3 by the CVD method, and a plasma surface treatment chamber for performing a surface treatment on the formed protective film 3 with plasma. 22. Reaction tube 15
An electrode 16 is incorporated therein, and a potential of +500 V to 2000 V is applied to the electrode 16 by a DC power supply 17. A raw material gas containing hydrocarbon as a main component is introduced into the reaction tube 15 from the gas inlet 18. An electrode 23 is incorporated in the plasma surface treatment chamber 22, and a reaction gas is supplied into the plasma surface treatment chamber 22 from a gas introduction pipe 24.

In this plasma processing apparatus 21, surface treatment is performed as follows. First, the film 11 wound around the unwinding roll 13 is supplied to the counter electrode 19 via the rotating support 12. The film 11 is transferred along the counter electrode 19 in the form of a drum, and the protective film 3 is formed in the reaction tube 15. The film 11 on which the protective film 3 is formed is
Next, the gas containing fluorine supplied to the plasma surface treatment chamber 22 is supplied from the gas introduction pipe 24 to the electrode 23.
Is turned into plasma, and the film 1
The surface treatment is performed on one protective film 3. The film 11 having been subjected to the surface treatment is wound around a take-up roll 14 via a rotary support 12.

The formation of the protective film 3 on the magnetic layer 2 and the surface treatment of the protective film 3 were performed by the plasma processing apparatus 21 under the following conditions. 1) Formation of protective film Source gas: hexamethyldisiloxane Reaction pressure: 10 Pa Introduced power: DC 2.0 kV Protective film thickness: 8 nm 2) Surface treatment of protective film Surface treatment gas: CF ₄ gas pressure: 1 Pa Introduced power: DC2 0.0 kV Processing time: 1 second In this way, the magnetic recording medium 10 having the configuration shown in FIG. 1 was formed.

Example 2 A magnetic recording medium 10 having the structure shown in FIG. 1 was formed in the same manner as in Example 1 except that NF ₃ was used as a surface treatment gas when the surface treatment of the protective film 3 was performed.

(Example 3) In the same manner as in Example 1 except that the source gas used for forming the protective film 3 is a gas obtained by mixing ethylene and hexamethylenedisiloxane at a ratio of 1: 1. A magnetic recording medium 10 having the above configuration was formed.

Comparative Example 1 A magnetic recording medium 1 having the structure shown in FIG. 1 was manufactured in the same manner as in Example 1 except that the raw material gas for forming the protective film 3 was ethylene, and the surface treatment was not performed on the protective film 3.
0 was formed.

Comparative Example 2 A magnetic recording medium 10 having the structure shown in FIG. 1 was formed in the same manner as in Example 1 except that the source gas for forming the protective film 3 was ethylene.

Comparative Example 3 Comparative Example 1 was repeated except that the material gas for forming the protective film 3 was hexamethylenedisiloxane.
1 to form a magnetic recording medium 10 having the configuration shown in FIG.

An environmental resistance test was performed on each sample of these magnetic recording media. The inside of the thermostat maintained at a temperature of 30 ° C. and a relative humidity of 90% was further set to a 0.5 ppm concentration SO ₂ gas atmosphere environment. Each sample was stored in the thermostat for one day, and the saturation magnetization before and after the storage was measured. The change in Ms was measured. still,
The saturation magnetization was measured using a VSM (sample vibration type magnetometer).

From the measured values, the variation ΔMs of the saturation magnetization was determined by the following equation (1).

[0037]

ΔMs = {Ms ′ (after storage) −Ms (before storage)} / Ms (before storage)

Table 1 shows ΔMs obtained from the measurement results of the samples of the example and the comparative example.

[0039]

[Table 1]

As shown in Table 1, each example is different from the comparative example in that
It can be seen that the deterioration of the saturation magnetization is extremely small and the storage characteristics are greatly improved. As described above, it can be understood from the above-described examples that a magnetic recording medium having good storage characteristics can be formed by modifying the protective film with silicon and fluorine. This effect can be similarly obtained by using a conventionally used hydrocarbon-based gas, for example, ethylene, methane, toluene, benzene or the like as a raw material gas.

In the magnetic recording medium of the present invention, in addition to the above-described embodiments, for example, a back coat layer may be formed on the back surface of the non-magnetic support, if necessary, or a lower layer may be provided between the non-magnetic support and the magnetic layer. It is also possible to form a coating layer or a lubricant layer. In these cases, conventionally known materials can be used for the nonmagnetic pigment, resin binder, and lubricant contained in the back coat layer.

The magnetic recording medium of the present invention is not limited to the above-described example, but may take various other configurations without departing from the gist of the present invention.

[0043]

According to the present invention described above, silicon-fluorine is formed on the surface of the protective film by modifying the surface of the protective film containing carbon as a main component with silicon and fluorine. Has improved weather resistance.

Therefore, according to the present invention, it is possible to improve the reliability of a magnetic recording medium, and to configure a magnetic recording medium suitable for special uses such as a data streamer and a video library that need to be stored for a long time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram (cross-sectional view) of an embodiment of a magnetic recording medium according to the present invention.

FIG. 2 is a schematic configuration diagram of a plasma processing apparatus used for manufacturing a magnetic recording medium of the present invention.

[Description of Signs] 1 base film, 2 magnetic layer, 3 protective film, 4 modified section, 10 magnetic recording medium, 11 film, 12 rotating support, 13 unwind roll, 14 take-up roll, 15 reaction tube, 16 Electrode, 17 DC power supply, 18
Gas inlet, 19 Counter electrode, 20 Vacuum exhaust system, 2
DESCRIPTION OF SYMBOLS 1 Plasma treatment apparatus, 22 Plasma surface treatment chamber, 2
3 electrodes, 24 gas inlet tubes

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Seiichi Onodera 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (5)

[Claims] 1. A magnetic recording medium having a magnetic layer on one surface of a nonmagnetic support and a protective film containing carbon as a main component formed on the magnetic layer, wherein the protective film has a surface made of silicon and A magnetic recording medium characterized by being modified with fluorine. 2. The magnetic recording medium according to claim 1, wherein the material of the protective film contains carbon and silicon. 3. The method according to claim 2, wherein a material obtained by mixing a siloxane-based material with a hydrocarbon-based material is used as the material of the protective film, and the material is reformed with a plasma gas of a fluorine compound. The magnetic recording medium according to the above. 4. The magnetic recording medium according to claim 3, wherein the siloxane raw material is hexamethyldisiloxane or octamethylcyclotetrasiloxane. 5. The method according to claim 1, wherein the fluorine compound is CF ₄ , CHF ₃ ,
At least one of SF ₆ , NF ₃ , BF ₃ , C ₂ F ₄
4. The magnetic recording medium according to claim 3, wherein the number is at least one.