JPH1049855A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic recording medium, whose purity is increased, whose mechanical strength is enhanced and whose running property and durability are good, by method wherein a plasma polymerization film composed of spherical carbons to which hydrocarbon is added is formed on a magnetic layer of the magnetic recording medium. SOLUTION: Electrodes 10, 11 for plasma generation are arranged in parallel inside a reactor 1 so as to keep an interval of 30cm, and the electrode 10 on one side is connected to a plasma power supply 13 via an impedance matching device 12. In addition, a molybdenum port 14 for fullerene sublimation and a sample 15 are disposed between the electrodes 10, 11 with interval of 10cm. In addition, the molybdenum port 14 and the sample 15 are installed between the electrodes 10, 11 so as to be faced by keeping an interval of 10cm, and a DC power supply 16 is connected to the molybdenum port 14.

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 a method for manufacturing the same, and more particularly to an improvement in a protective layer.

[0002]

2. Description of the Related Art The third after diamond and graphite
The existence of fullerene, a spherical carbon compound, was revealed as the crystalline carbon of, and it was only in 1990 that the synthesis of macro amounts was established.

[0003] Fullerenes are a series of spherical carbon compounds consisting only of carbon (Higher Fullerness).
And includes 12 5-membered rings and 12 or more 6-membered rings. That is, 60, 70, 7
A spherical carbon in which 6 or 84 carbon atoms (the number of carbon atoms is selected from the numbers capable of geometrically forming a spherical structure) are spherically bonded to form a cluster, each of which is C ₆₀ , C ₇₀ , C ₇₆ or C ₈₄ .

For example, C ₆₀ has a polyhedral structure called “truncated icosahedron” in which all vertices of a regular icosahedron are cut off to form a regular pentagon, and as shown in FIG. This is a cluster in which all vertices are substituted with carbon atoms C, and has a molecular structure similar to an official soccer ball. In addition, C ₇₀ has a molecular structure similar to a rugby ball like that shown in FIG. 16, and C ₇₆ or C ₈₄ has a similar structure.

[0005]

The fullerenes described above have been studied in various fields for their uses, and one of the uses is considered as a raw material for a protective layer for a magnetic recording medium. I have.

Generally, in a magnetic recording medium, the surface on the side of the magnetic layer slides at a high speed with the magnetic head. Therefore, a protective layer is provided on the magnetic layer for the purpose of imparting durability to the sliding.

As the protective layer for the magnetic recording medium, a layer in which carbon atoms are distributed in an amorphous state has been used. This amorphous carbon protective layer has properties intermediate between graphite and diamond.

As a method for forming such a carbon protective layer, a sputtering method is generally used. In this sputtering method, ions of an inert gas such as Ar collide with a target such as graphite, and carbon atoms are released to the outside by the collision energy, and the released carbon atoms are deposited on the surface of the magnetic layer. A film is formed.

In this sputtering method, since the raw material consists only of carbon atoms, there is no contamination of the protective layer to be formed with impurities derived from the raw material. In addition, it has the advantages that the film quality is dense and the film can be formed relatively easily.
However, there is a drawback that the deposition rate is very slow,
There is a problem in productivity.

On the other hand, CVD (Chemical) has recently been attracting attention because of its high deposition rate.
Vapor Deposition) method.

In this CVD method, a mixed gas of a source gas containing a solid product element to be generated (in this case, for example, CH ₄ gas or the like is used to generate carbon) and a carrier gas, A reaction is caused by heat or plasma, and carbon atoms generated by the reaction are adhered to the surface of the magnetic layer to form a carbon protective layer.

The CVD method can obtain a film formation rate about 5 to 10 times that of the sputtering method, and is advantageous for increasing productivity. However, this CVD method also has some problems. For example, since the constituent element of the raw material gas is not only carbon, other elements such as hydrogen that have not been completely decomposed with carbon remain in the protective layer, and it is difficult to treat the exhaust gas. Further, since the carbon film formed by the CVD method has lower density than the carbon film formed by the sputtering method, the oxidation of the magnetic layer cannot be sufficiently prevented. Further, when a lubricant is held for the purpose of improving the running property of the medium, there is a disadvantage that the lubricant is easily lost from the surface.

At present, these two types of film forming methods are mainly used as a method for forming a protective layer, and thus each has advantages and disadvantages.

Therefore, as a solution to the problems in these film forming methods, the use of the fullerene described above is considered promising.

First, since fullerene is composed only of carbon atoms, elements other than carbon are hardly mixed into the formed protective layer.

Further, since only the van der Waals force acts between the spherical molecules of fullerene, it can be sublimated at a relatively low temperature of about 500 ° C. unlike graphite or the like. It is possible to adopt a simple heating method.

Further, fullerene is expected to exhibit lubricity since its surface is surrounded by π electrons.

That is, graphite, which is generally known as a solid lubricant, has a six-membered ring spread in a plane, which is π
Layers are formed by overlapping electrons. Graphite exhibits lubricity by π electrons spreading on this surface. However, graphite has low strength to be used as a protective layer of a medium, and is very difficult to form on a medium. For this reason, an amorphous carbon film formed by a sputtering method or the like as described above is used as the protective layer.

On the other hand, fullerene typified by C ₆₀ also has a surface surrounded by π electrons like graphite,
This is expected to show lubricity. When the protective layer has lubricity, the coefficient of friction with the magnetic head and various sliding members is reduced, which is advantageous in improving the running durability of the medium.

However, for example, when fullerene is simply formed as a vapor-deposited film, only van der Waals force acts between molecules of fullerene. For this reason,
Even if it has lubricity, peeling, film shaving and the like are likely to occur, and it is insufficient as a protective layer.

On the other hand, it is conceivable to cause plasma polymerization by sublimating fullerene in an inert gas plasma. Such a plasma-polymerized fullerene film has an additional bond between fullerenes and exhibits excellent mechanical properties. However, plasma polymerization of fullerene lowers the π-electron density, and tends to be inferior in lubricity as compared with, for example, graphite.

As described above, fullerene is promising as a protective layer for a magnetic recording medium, but a technique for achieving both mechanical strength and lubrication performance has not been established.

Accordingly, the present invention has been proposed in view of such conventional circumstances, and a protective layer having high purity, excellent mechanical strength, and lubricity is formed at a high film forming rate. It is an object of the present invention to provide a magnetic recording medium having excellent running properties and durability and excellent productivity, and a method for manufacturing the same.

[0024]

The inventors of the present invention have made intensive studies to achieve the above object, and as a result, have found that fullerene C
or sublimed in hydrocarbon gas plasma _n, or when the plasma treatment of a hydrocarbon gas into a plasma polymerization film of fullerene C _n, excellent mechanical strength, yet lubricity, plasma polymerized film having antistatic properties Has been obtained.

The magnetic recording medium of the present invention has been completed based on such findings.

That is, the magnetic recording medium of the present invention has at least a magnetic layer and a protective layer formed on a nonmagnetic support, and the protective layer is formed of C _n (where n is a geometrically spherical compound). is an integer which can form consists plasma polymer spherical carbons represented by.), at least a portion of the spherical carbons which constitute the plasma polymer, (C _a H _{b) c}
(However, a, b, and c are all integers.) A hydrocarbon is added.

In the method for producing a magnetic recording medium of the present invention, after forming a magnetic layer on a nonmagnetic support, C _n (where n is an integer capable of forming a geometrically spherical compound). ) Is characterized by forming a protective layer by performing plasma polymerization in the presence of a hydrocarbon gas using spherical carbons represented by the formula (1).

Further, after forming a magnetic layer on a non-magnetic support, a spherical carbon represented by C _n (where n is an integer capable of forming a spherical compound geometrically) is converted into a sublimation source. A plasma polymerization film is formed by performing plasma polymerization in the presence of an inert gas, and a protective layer is formed by performing plasma treatment of a hydrocarbon gas on the plasma polymerization film. .

[0029] A plasma polymer spherical carbons C _n, a protective layer at least partially on the hydrocarbon spherical carbons C _n constituting the plasma polymer is added bond,
It exhibits excellent mechanical strength by bridging structure by additional bond and the added hydrocarbon spherical carbons C _n together. In addition, the added hydrocarbon, particularly a hydrocarbon having a long chain, imparts lubricity and electric conductivity, and functions as a lubricant layer and an antistatic layer as well as a protective layer. Therefore, a magnetic recording medium on which such a protective layer is formed,
Good running performance and durability are obtained.

Such a protective layer is formed by subjecting spherical carbons C _n to a sublimation source and performing plasma polymerization in the presence of a hydrocarbon gas or by performing plasma polymerization in the presence of an inert gas. A polymer film is formed, and the plasma polymer film is formed by performing a plasma treatment with a hydrocarbon gas.

At this time, the spherical carbon C _{n as} a raw material is
Since only the Van der Waals force acts between the molecules, it easily sublimates, and a film formation rate equal to or higher than that of the CVD method can be obtained. Further, unlike the CVD method, there is no problem that elements other than carbon are mixed in the protective layer and there is no problem of exhaust gas treatment. Therefore, a high-purity protective layer is efficiently formed, and high productivity is obtained.

[0032]

Embodiments of the present invention will be described below.

The magnetic recording medium according to this embodiment, on a nonmagnetic support, a magnetic layer, a protective layer is formed in sequence, particularly the protective layer, the polymerization of the spherical carbon compound represented by C _n It is formed as a hydrocarbon-added fullerene polymer film in which hydrocarbon is added to the structure.

The hydrocarbon addition fullerene polymer film is deposited by sublimation of spherical carbons C _n hydrocarbon gas plasma. When sublimation of spherical carbons Cn hydrocarbon gas plasma, and the polymerization is spherical carbons C _n together with causing hydrocarbons addition reaction with spherical carbons C _n,
Is polymerized structure hydrocarbon spherical carbons C _n polymerized film having a structure added is deposited.

At this time, in the addition reaction between the spherical carbons C _n and the hydrocarbon, the double bond of the spherical carbons C _n is broken, and the hydrocarbon is added at this position. There are various addition reaction products generated by this addition reaction. As specific examples, C ₆₀ and C ₂
The addition reaction of H _{6 and} the addition reaction between C ₆₀ and C ₂ H ₂ will be described.

First, C ₂ H ₆ is a saturated hydrocarbon, and this hydrocarbon and C ₆₀ produce an addition reaction product as shown in FIGS. C ₂ H ₆ of these, FIG. 1 to C ₆₀ 1 molecule
Is intended but with the addition, C 2 molecule Figures 2-4 C _60
2 H ₆ is added. The one C ₂ H ₆ in the two molecules were added, FIG. 2, the case where C ₂ H ₆ 2 molecules as shown in FIG. 3 is added directly to C _60, respectively, added to the C ₆₀ as shown in FIG. 4 In some cases, another C ₂ H ₆ is added to the end of the C ₂ H ₅ thus formed to form a long chain.

The most frequent occurrence of these reactions is shown in FIG.
It has been found that this is an addition reaction of the type shown in FIG. The hydrocarbon having a long chain thus plays a role similar to that of a general hydrocarbon-based lubricant, and contributes to a reduction in friction on the film surface.

In addition, as shown in FIG. 5, in the addition reaction between C ₆₀ and C ₂ H ₆ , it was confirmed that a bridge structure of C ₂ H ₂ was formed between two C _60s. I have. The crosslinked structure is also relatively stable, contributing to the degree of polymerization improvement of C _60, increasing the strength of the film.

Next, C ₂ H ₂ is an unsaturated hydrocarbon, and this hydrocarbon and C ₆₀ are accompanied by addition reaction products and desorption of hydrogen H ₂ as shown in FIGS. An addition reaction product as shown in FIG. 9 results. According to the calculation results of the heat of reaction by the semi-empirical molecular orbital method, it is clear that the most likely of these reactions is the addition reaction of the type shown in FIG. Also, the ends of the hydrocarbon appended to spherical carbons C _n, added another hydrocarbon, may form a long chain. The hydrocarbon thus added plays a role similar to that of a general hydrocarbon-based lubricant, and contributes to reduction of friction on the film surface.

In addition, as shown in FIG. 10, in the addition reaction of C ₆₀ and C ₂ H ₂ , it has been confirmed that a bridge structure of C ₂ is formed between two C _60s . The crosslinked structure is also relatively stable, contributing to the degree of polymerization improvement of C _60, increasing the strength of the film.

On the other hand, the hydrocarbon gas plasma, with these additional reactions occur, the polymerization reaction occurs to be added to each other at a plurality of the fullerene C _n is at least one place, the basic skeleton of the polymer film is formed.

The basic skeleton is (C _{n + j} ) _x (where n is 6
0, 70, 76, 84, etc., is an integer capable of forming a geometrically spherical shape, j is a multiple of −10 to 10;
x is an integer. ). Where j
Represents the number of carbons missing or added from Cn alone. That is, by lack or addition of carbon from C _n, C58, C56, · · · or C62 or the like is obtained, because they polymerize, the Cn polymerized structure necessarily a skeleton of integral multiple polymer C _n Not necessarily.

[0043] Such C _n polymeric structure may take a variety of forms, the following applies for the case of a dimer of C _60, another structure of the C _120, as shown in FIG. 11, the missing carbon the resulting structure like the C _116, as shown in structure or FIG. 13, the C _118, as shown in FIG. 12 is present. Those having a higher degree of polymerization are considered to have a mixture of these bond forms.

The protective layer may be formed only of these C _n polymerized structures, but in this case, it is presumed that the C _n polymerized structure is spread over the whole network by covalent bonds. Further, if it has a C _n polymerized structure partially, the C _n polymerized structure distributed in amorphous, the portion not polymerized is presumed that are bound together by van der Waals forces . Incidentally, in this protective layer, together with the C _n polymerized structure, C _n single molecules of C ₆₀ or the like as a raw material may be mixed. Further, the hydrocarbon may be added to all of the spherical carbons constituting the C _n polymerized structure, or may be added to some of the spherical carbons.

The carbon number n of the spherical carbons C _n used as the raw material is preferably 60 from the viewpoint of the availability of the raw material and the strength of the film. Although it is possible to form a polymer film with other spherical carbons, for example, the number of carbon atoms is _n
There polymerized film deposited by high-order spherical carbon such as 70,76,84, the mechanical strength is inferior to the polymerization film formed by C _60. Spherical carbons other than C ₆₀ are
The production yield is greatly reduced and disadvantageous. As the raw material, 1 be used types of spherical carbons C _n alone may be used in combination of plural kinds of spherical carbons C _n.

The hydrocarbon for generating the hydrocarbon gas plasma may be a saturated hydrocarbon such as C ₂ H ₆ ,
_It may be an unsaturated hydrocarbon such as ₂ H ₂ .

The saturated hydrocarbon is represented by C _x H _{2x + 2} (where x is a positive number), and in addition to C ₂ H ₆ exemplified above,
It is easy to handle gaseous ones under normal pressure such as H ₄ and C ₃ H ₈ . In the case of a hydrocarbon having a relatively large number of carbon atoms, which is in a liquid state at normal pressure, it can be used by reducing the pressure in the reactor.

On the other hand, as the unsaturated hydrocarbon, any of those having a double bond such as C ₂ H ₄ and those having a triple bond such as C ₂ H ₂ may be used. However, from the viewpoint of reactivity, it is desirable to use a compound having a triple bond such as C ₂ H ₂ .

These saturated hydrocarbons and unsaturated hydrocarbons are also shown in FIG. 1 to FIG.
~ Addition reaction product is produced according to FIG. One type of hydrocarbon may be used alone, or a plurality of types may be used in combination. Further, it may be used by being mixed with another gas such as an inert gas.

The hydrocarbon-added fullerene polymer film is formed by sublimating the spherical carbons C _n in a hydrocarbon gas plasma as described above.
_After sublimating _n in an inert gas plasma to form a fullerene polymer film, the fullerene polymer film is also subjected to plasma treatment with a hydrocarbon gas.

When the fullerene polymer film is subjected to a plasma treatment with a hydrocarbon gas, the double bond of fullerene is broken at the outermost surface of the fullerene polymer film, and hydrocarbon is added to this portion to form a hydrocarbon-added fullerene polymer film. Is done.

In this case, any of the above-listed examples of the spherical carbon C _n used as a raw material and the hydrocarbon for subjecting the fullerene polymerized film to gas plasma treatment can be used.

As described above, in the present invention, the spherical carbon represented by C _n is subjected to plasma polymerization as a sublimation source, and a protective layer is formed by adding a hydrocarbon.

Here, the greatest advantage of using spherical carbons C _n as a sublimation source is that only van der Waals forces act between molecules of C _n , such as graphite or graphite. Unlike this, sublimation can be performed at a relatively low temperature of about 500 ° C. Therefore, a strong plasma polymerized film can be formed in a short time.

[0055] Moreover, the order spherical carbons C _n is causing easy addition reaction, it is possible to have a lubricating property and the electrical conductivity by an addition of such hydrocarbons.

Thus, a protective layer having mechanical properties, lubricating properties and antistatic properties can be obtained.

[0057] The discharge system of plasma generation for causing plasma polymerization spherical carbons C _n, a known DC discharge,
Various methods such as low-frequency discharge, high-frequency discharge, microwave discharge, etc. can be adopted. Type, electrodeless oscillation type, and the like.

There is no problem in polymerization as long as the discharge condition is a range in which Paschen's law indicating the relationship between gas pressure, distance between electrodes, and voltage is satisfied in DC discharge, and a dischargeable range in AC discharge. The gas pressure is preferably below 13 Pascal (100 mT).

The magnetic recording medium of the present invention is provided with the protective layer as described above. Other materials constituting the magnetic recording medium, such as a non-magnetic support and a material of the magnetic layer, are usually used. Any of them can be used.

For example, non-magnetic supports include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polyethylene and polypropylene; cellulose triacetate;
Cellulose derivatives such as cellulose diacetate and cellulose triacetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonates, polymer materials represented by polyamideimides, aluminum alloys, titanium alloys and the like Metal plate,
Examples of the support include a support formed of alumina glass, ceramics, and the like. The form is not limited at all, and may be any form such as a tape form, a sheet form, and a drum form.

As the magnetic layer, for example, a metal magnetic thin film is provided. This metal magnetic thin film can be formed as a continuous film by a PVD (physical vapor deposition) technique such as plating, sputtering, or vacuum vapor deposition. For example, Fe, Co, N
i, Co-Ni alloy, Co-Pt alloy, Co-Pt
-Ni-based alloy, Fe-Co-based alloy, Fe-Ni-based alloy,
Fe-Co-Ni alloy, Fe-Ni-B alloy, Fe
A metal magnetic thin film made of a -Co-B-based alloy, an Fe-Co-Ni-B-based alloy, or the like. In this case, the thickness of the metal thin film is desirably about 50 nm to 200 nm.

[0062]

EXAMPLES Hereinafter, examples to which the present invention is applied will be described in detail based on specific experimental results. Needless to say, the present invention is not limited by this embodiment.

Plasma Polymerization Apparatus In the present invention, various plasma polymerization apparatuses can be used for forming the protective layer. Here, the configuration of the parallel plate electrode type capacitively coupled plasma polymerization apparatus used in this embodiment is described. explain.

FIG. 14 shows a parallel plate electrode type capacitively coupled plasma polymerization apparatus used in this embodiment.

This plasma polymerization apparatus includes a reactor 1 having a capacity of about 20 liters, and the reactor 1 is provided with gas supply pipes 2 and 3. Also, at the bottom of the reactor 1,
The oil diffusion pump 4 is provided with an exhaust port 9 connected to a vacuum exhaust system composed of rotary pumps 5 and 6, liquid nitrogen traps 7 and 8, and the like.

In the reactor 1, plasma generating electrodes 10, 11 are arranged in parallel with a spacing of 30 cm.
One electrode 10 is connected to a plasma power supply 13 via an impedance matching device 12. Also, the upper electrode 1
From 0, gas is introduced between these electrodes 10 and 11 in a shower-like manner.

Further, a molybdenum boat 14 for fullerene sublimation and a sample 15 are provided between the electrodes 10 and 11.
The molybdenum boat 14 is connected to a direct-current power supply 16 at a distance of 0 cm.

The output of the plasma power supply 13 is 13.5 AC.
It is a radio wave of MHz. Here, this output is 10W
To 100 W, and a hydrocarbon-based gas (or an inert gas) set at 13.5 Pascal was generated in a constant flow rate system. In this plasma, fullerene in a molybdenum boat 14 was sublimated to perform plasma polymerization. . In addition,
The film thickness during the polymerization was continuously monitored by the sensor 17.

Fullerene as a raw material was obtained from soot produced by generating a DC arc discharge in a He atmosphere using a carbon graphite rod as an electrode. The conditions for producing soot are an applied voltage of 60 V, a discharge current of 200 A, and a He gas pressure of 100 Torr.

From the soot thus formed, Cn was extracted by extraction with an organic solvent such as benzene or toluene.
Is obtained. The mixture of Cn was applied to a silica gel column using benzene or toluene as a developing solvent to separate C60 or C70. Then, each separated extract was dried to obtain a raw material for plasma polymerization.

Example 1 A 10 μm thick polyethylene terephthalate film was
A Co—Ni-based alloy is deposited by oblique deposition,
A 00 nm ferromagnetic metal thin film was formed and cut into a length of 20 cm and a width of 8 mm.

Next, on the surface of the metal magnetic thin film, a hydrocarbon-added fullerene polymer film (protective layer) was formed to a thickness of 10 nm by the above-mentioned plasma polymerization apparatus to prepare a sample tape. Here with C ₆₀ fullerene alone sublimation source, polymerization was performed under C ₂ H ₆ gas plasma. The output of the plasma power supply is 20W.

Examples 2 to 5 Sample tapes were prepared in the same manner as in Example 1 except that the output of the plasma power supply was changed as shown in Table 1 when forming the hydrocarbon-added fullerene polymer film. .

Examples 6 to 9 The same procedures as in Example 1 were carried out except that the saturated hydrocarbon shown in Table 1 was used as the plasma gas and the output of the plasma power supply was 60 W when forming the hydrocarbon-added fullerene polymer film. A sample tape was produced in the same manner.

Example 10 When forming a hydrocarbon-added fullerene polymer film, C
_{The same} procedure as in Example 1 was performed except that a mixture (C ₆₀ / C ₇₀ fullerene) obtained by mixing ₆₀ and C ₇₀ at a ratio of 5: 5 (molar ratio) was used as a sublimation source and the output of the plasma power supply was changed to 60 W. To prepare a sample tape.

Example 11 When forming a hydrocarbon-added fullerene polymer film, C
_A sample tape was produced in the same manner as in Example 1 except that ₇₀ fullerene alone was used as a sublimation source, and the output of the plasma power supply was changed to 60 W.

Example 12 When forming a hydrocarbon-added fullerene polymer film, C
_{The same} procedure as in Example 1 was carried out except that a mixture (C ₆₀ / C ₇₆ fullerene) obtained by mixing ₆₀ and C ₇₆ at a ratio of 5: 5 (molar ratio) was used as a sublimation source and the output of the plasma power supply was changed to 60 W. To prepare a sample tape.

Example 13 When forming a hydrocarbon-added fullerene polymer film, C
A mixture was prepared in the same manner as in Example 1 except that a mixture (C ₆₀ / C ₈₄ fullerene) obtained by mixing ₆₀ and C ₈₄ at a ratio of 5: 5 (molar ratio) was used as a sublimation source, and the output of the plasma power supply was changed to 60 W. To prepare a sample tape.

Example 14 When forming a hydrocarbon-added fullerene polymer film, C
_A sample tape was prepared in the same manner as in Example 1 except that ₂ H ₄ was used as a plasma gas.

Examples 15 to 17 Sample tapes were prepared in the same manner as in Example 14 except that the output of the plasma power source was changed as shown in Table 2 when forming the hydrocarbon-added fullerene polymer film. .

Example 18 When forming a hydrocarbon-added fullerene polymer film, C
_A sample tape was produced in the same manner as in Example 1 except that ₂ H ₂ was used as a plasma gas.

Examples 19 to 21 Sample tapes were prepared in the same manner as in Example 18 except that the output of the plasma power supply was changed as shown in Table 2 when forming the hydrocarbon-added fullerene polymer film. .

Example 22 When forming a hydrocarbon-added fullerene polymer film, C
_A sample tape was prepared in the same manner as in Example 1 except that ₃ H ₆ was used as a plasma gas and the output of the plasma power supply was changed to 60 W.

Example 23 When forming a hydrocarbon-added fullerene polymer film, C
Same as Example 14 except that a mixture (C ₆₀ / C ₇₀ fullerene) obtained by mixing ₆₀ and C ₇₀ at a ratio of 5: 5 (molar ratio) was used as a sublimation source and the output of the plasma power supply was changed to 60 W. To prepare a sample tape.

Example 24 When forming a hydrocarbon-added fullerene polymer film, C
_A sample tape was prepared in the same manner as in Example 14, except that ₇₀ fullerene alone was used as a sublimation source, and the output of the plasma power supply was changed to 60 W.

Example 25 When forming a hydrocarbon-added fullerene polymer film, C
Example 14 was carried out in the same manner as in Example 14 except that a mixture (C ₆₀ / C ₇₆ fullerene) obtained by mixing ₆₀ and C ₇₆ at a ratio of 5: 5 (molar ratio) was used as a sublimation source, and the output of the plasma power supply was changed to 60 W. To prepare a sample tape.

Example 26 When forming a hydrocarbon-added fullerene polymer film, C
_{The same} procedure as in Example 14 was carried out except that a mixture (C ₆₀ / C ₈₄ fullerene) obtained by mixing ₆₀ and C ₈₄ at a ratio of 5: 5 (molar ratio) was used as a sublimation source and the output of the plasma power supply was changed to 60 W. To prepare a sample tape.

Example 27 A sample tape was prepared in the same manner as in Example 1 except that a hydrocarbon-added fullerene polymer film was formed as follows.

Using C ₆₀ fullerene alone as a sublimation source,
A fullerene plasma polymerized film was formed at an output of 60 W under Ar gas plasma. Subsequently, C was added to this plasma polymerized film.
A plasma treatment with ₂ H ₆ gas was performed at an output of 60 W, and a hydrocarbon was added to the plasma polymerized film to form a protective layer.

Example 28 A sample tape was produced in the same manner as in Example 27 except that He gas was used as a plasma gas when forming a fullerene polymer film.

Example 29 A sample tape was prepared in the same manner as in Example 27, except that hydrocarbon was added to the fullerene polymer film by performing plasma treatment with C ₂ H ₂ gas at an output of 60 W.

Example 30 A sample tape was prepared in the same manner as in Example 29 except that a He gas was used as a plasma gas when forming a fullerene polymer film.

Comparative Example 1 Instead of forming a hydrocarbon-added fullerene polymer film, C
_A sample tape was prepared in the same manner as in Example 1 except that a protective layer was formed by performing vapor deposition under vacuum of 10 ⁻³ Pascal using ₆₀ fullerene alone as a sublimation source.

[0094] Instead of forming the Comparative Example 2 hydrocarbon addition fullerene polymer film, using a C ₆₀ fullerene alone as sublimation source, under Ar gas plasma, except for forming a plasma polymerized film of fullerene in output 60W embodiment A sample tape was produced in the same manner as in Example 1.

Comparative Example 3 A carbon protective layer was formed by a sputtering method instead of forming a hydrocarbon-added fullerene polymer film.

Comparative Example 4 Instead of forming a hydrocarbon-added fullerene polymer film, C
A carbon protective layer was formed by the VD method.

[0097]

[Table 1]

[0098]

[Table 2]

[0099]

[Table 3]

With respect to the sample tape manufactured as described above, the friction coefficient, the still characteristics, and the scratching strength were measured. The results are shown in Tables 4 to 7. In addition, these measuring methods are as follows.

Coefficient of friction: The coefficient of friction of the sample tape against the stainless steel guide pin.
It shows the coefficient of friction at the 200th time when it is performed 0 times. The smaller the value, the lower the friction and the better the running performance.

Still characteristics: An 8 mm video deck modified for a durability test was used. The video deck for durability test has a rotating drum and a recording / reproducing system, and the output change of only the same portion of the sample tape is monitored. Using this deck, the time (minutes) required for the output to reach half the value of the first reproduction was measured. The larger the value, the better the durability. The measurement was performed for a maximum of 120 minutes.

Scratch strength: A protective layer was formed on a glass plate under the same conditions as those for forming a film on the sample tape. Then, the protective layer was rubbed with tweezers, and the state of the scratch on the protective layer at that time was visually observed. ◎: When scars are scarcely recognized, ○: Slight scratches are recognized but almost no problem, △: When scratches are slightly recognized,
X shows the case where many scratches are seen and becomes a problem in terms of durability.

[0104]

[Table 4]

[0105]

[Table 5]

[0106]

[Table 6]

[0107]

[Table 7]

First, the sample tapes of Examples 1 to 26 in which a hydrocarbon-added fuller polymerized film was formed by plasma polymerization under a hydrocarbon gas plasma were used in Comparative Example 1 in which a deposited film of fullerene was formed as a protective layer. Compared with the sample tape of Comparative Example 2 in which a sample tape or a plasma polymerized film is formed but no hydrocarbon is added to the polymerized film, a protective layer having higher strength is formed, and the durability is excellent. ing. Also, the coefficient of friction is low.
This is because in a fullerene vapor deposited film, only van der Waals force acts between fullerene molecules, whereas in the case of a fullerene plasma polymerized film, addition polymerization occurs between fullerene molecules and a strong film is formed. It is because it forms. Further, the lubricating property is imparted by the hydrocarbon added to the polymer film.

The hydrocarbon-added fullerene polymer film formed in each of Examples 1 to 26 is equivalent to the sputtered carbon film formed in Comparative Example 3 or the CVD carbon film formed in Comparative Example 4. It has strength and durability.

Here, the sputtering method has a low film forming rate, and the CVD method has a problem of low film purity and an exhaust gas treatment. On the other hand, in plasma polymerization of fullerene, C
A film formation rate equivalent to that of the VD method can be obtained, a high-purity polymer film can be formed in a short time, and the formed thin film has excellent strength and durability. In other words, it can be said that the fullerene plasma polymerized film is superior to the sputtered film and the CVD film in both the characteristics as a protective layer and the productivity.

In addition, looking at the experimental data in more detail,
Among those obtained by adding a saturated hydrocarbon to the plasma polymerized film, those having a saturated hydrocarbon having 2 or more carbon atoms have a significantly reduced friction coefficient. Further, among the plasma polymerized films obtained by adding unsaturated hydrocarbons, those obtained by adding C ₂ H ₂ having a triple bond (Examples 18 to 21) greatly reduced the friction coefficient. ing.

Further, as in the third to ninth embodiments, the sixteenth, the seventeenth, the twentieth and the twenty-first embodiments,
It can be seen that the polymer film formed with high plasma power has more excellent strength and durability.

[0113] Examples 10 to 13, Example 23 to Example 26, as a mixture of higher fullerenes such as C _70, C ₇₆ or C ₈₄ to C ₆₀ as a sublimation source, or these higher fullerenes Is used alone. These plasma polymerized films also have higher strength than the fullerene vapor-deposited film of Comparative Example 1 and the fullerene polymerized film of Comparative Example 2.
Compared to a plasma polymerized film formed using ₆₀ alone, still characteristics or scratch strength are inferior.
This has been confirmed experimentally in comparison with C ₆₀ C
_70, the higher fullerenes such as C ₇₆ or C ₈₄ because hardly occurs polymerization of fullerene molecules together. In addition, C ₇₀
Higher fullerenes have very low production yields.
It is disadvantageous from an industrial point of view. Therefore, it is desirable to use C ₆₀ as sublimation source from properties and industrial point of view.

On the other hand, in the case of Examples 27 to 30, the fullerene polymerized film was once formed under the inert gas plasma, and then the fullerene polymerized film was subjected to the plasma treatment with the hydrocarbon gas. . These sample tapes also have properties equivalent to those obtained by plasma polymerization under hydrocarbon gas plasma.

Therefore, as a method of adding a hydrocarbon to the fullerene polymerized film, a hydrocarbon gas may be introduced into the reactor in advance when polymerizing the fullerene, and the hydrocarbon is added to the once formed fullerene polymerized film. It is understood that a method of performing plasma treatment of gas may be used.

[0116]

As is clear from the above description, in the present invention, since a plasma-polymerized film of spherical carbons to which hydrocarbons are added is formed on the magnetic layer of the magnetic recording medium, the CVD method is used. A protective layer having excellent mechanical strength, lubricating performance, and antistatic property can be formed at a film forming rate equal to or higher than that. In addition, unlike the CVD method, the plasma polymerization does not cause impurities derived from raw materials to be mixed into the protective layer, and does not cause a problem of exhaust gas treatment.

Therefore, the magnetic recording medium on which such a protective layer is formed can obtain good running properties and durability, and can obtain high productivity, which is very advantageous industrially. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an addition reaction product by an addition reaction between C ₆₀ and C ₂ H ₆ .

FIG. 2 is a schematic diagram showing another example of an addition reaction product by an addition reaction between C ₆₀ and C ₂ H ₆ .

FIG. 3 is a schematic diagram showing still another example of the addition reaction product obtained by the addition reaction between C ₆₀ and C ₂ H ₆ .

FIG. 4 is a schematic diagram showing still another example of an addition reaction product obtained by addition reaction between C ₆₀ and C ₂ H ₆ .

FIG. 5 is a schematic diagram showing a bridge structure of C ₂ H ₂ formed between two molecules of C ₆₀ .

FIG. 6 is a schematic diagram showing an example of an addition reaction product by an addition reaction between C ₆₀ and C ₂ H ₂ .

FIG. 7 is a schematic diagram showing another example of an addition reaction product obtained by the addition reaction between C ₆₀ and C ₂ H ₂ .

FIG. 8 is a schematic diagram showing still another example of the addition reaction product obtained by the addition reaction between C ₆₀ and C ₂ H ₂ .

FIG. 9 is a schematic diagram showing still another example of the addition reaction product obtained by the addition reaction between C ₆₀ and C ₂ H ₂ .

FIG. 10 is a schematic view showing a bridge structure by C ₂ formed between two molecules of C ₆₀ .

11 is a schematic diagram showing the structure of C _120.

12 is a schematic diagram showing the structure of C _118.

13 is a schematic diagram showing the structure of C _116.

FIG. 14 is a schematic sectional view showing one configuration example of a plasma polymerization apparatus.

15 is a schematic diagram showing the structure of a C ₆₀ fullerene.

16 is a schematic diagram showing the structure of a C ₇₀ fullerene.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location G11B 5/72 G11B 5/72 // C10N 40:18

Claims (13)

[Claims] 1. A magnetic recording medium comprising at least a magnetic layer and a protective layer formed on a nonmagnetic support, wherein the protective layer is formed of C _n (where n is a geometrically spherical compound). Which is an integer.), And at least a part of the spherical carbons constituting the plasma polymer has (C _a H _b ) _c (provided that:
a, b, and c are all integers. A magnetic recording medium comprising a hydrocarbon represented by the formula (1): 2. The magnetic material according to claim 1, wherein the plasma polymer has a structure in which a plurality of spherical carbons are polymerized by forming at least one additional bond between the spherical carbons. recoding media. 3. The magnetic recording medium according to claim 1, wherein the plasma polymer has a structure in which spherical carbons are distributed in an amorphous state. 4. After forming a magnetic layer on a non-magnetic support,
A protective layer is formed by performing plasma polymerization in the presence of a hydrocarbon gas using a spherical carbon represented by C _n (where n is an integer capable of forming a spherical compound geometrically). A method for manufacturing a magnetic recording medium. 5. The method according to claim 4, wherein two or more types of spherical carbons are used as a sublimation source when performing the plasma polymerization. 6. The method for producing a magnetic recording medium according to claim 4, wherein the plasma polymerization is performed in the presence of a mixed gas comprising two or more hydrocarbon gases. 7. The hydrocarbon gas used in the plasma polymerization,
The method for producing a magnetic recording medium according to claim 4, wherein the magnetic recording medium is a saturated hydrocarbon. 8. The hydrocarbon gas used in the plasma polymerization,
5. The method for producing a magnetic recording medium according to claim 4, wherein the method is an unsaturated hydrocarbon. 9. After forming a magnetic layer on a nonmagnetic support,
A plasma polymerized film is formed by performing plasma polymerization in the presence of an inert gas using spherical carbons represented by Cn (where n is an integer capable of geometrically forming a spherical compound). A method for manufacturing a magnetic recording medium, comprising forming a film and performing a plasma treatment of a hydrocarbon gas on the plasma polymerized film to form a protective layer. 10. The method of manufacturing a magnetic recording medium according to claim 9, wherein two or more types of spherical carbons are used as a sublimation source when performing the plasma treatment. 11. The method for manufacturing a magnetic recording medium according to claim 9, wherein the hydrocarbon gas used in the plasma processing is a mixed gas of two or more hydrocarbon gases. 12. The method according to claim 9, wherein the hydrocarbon gas used in the plasma processing is a saturated hydrocarbon. 13. The method according to claim 9, wherein the hydrocarbon gas used in the plasma processing is an unsaturated hydrocarbon.