JP2000357313A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the stability of adhesion of a lubricant to a protective film and to enhance traveling performance and durability by disposing the protective film top-coated with an aromatic alcohol on a magnetic layer formed on a nonmagnetic substrate and holding the lubricant containing an ester compound of a perfluoro-polyether and a long chain carboxylic acid and a long chain saturated fatty acid ester on the outermost layer. SOLUTION: The lubricant contains an ester compound of a perfluoro- polyether having hydroxyl groups at the ends and a long chain carboxylic acid represented by formula I and a long chain saturated fatty acid ester represented by formula II. In the formula I, Rf is a perfluoro-polyether chain and R1 is a hydrocarbon group or a fluorohydrocarbon group. In the formula II, RI and RII are each alkyl. The long chain saturated fatty acid ester may be octyl myristate or heptyl stearate. The aromatic alcohol may be 4- methylresorcinol. Since the surface of the protective film is treated with the aromatic alcohol, the adhesion of the lubricant to the protective film is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support by a vacuum thin film forming technique.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a magnetic coating comprising a ferromagnetic powder such as an oxide magnetic powder or an alloy magnetic powder, a binder, and an organic solvent is applied to a non-magnetic support. A so-called coating type magnetic recording medium in which a layer is formed is widely used.

On the other hand, as the demand for high-density recording and long-time recording has increased, Co, Co-Ni alloys, Co-
A ferromagnetic metal magnetic material such as a Cr alloy or Co-O is directly coated on a non-magnetic support such as a polyester film or a polyimide film by plating or a vacuum thin film forming technique (a vacuum deposition method, a sputtering method, an ion plating method, etc.). A magnetic recording medium of a so-called ferromagnetic metal thin film type, in which a magnetic layer is formed by being attached, has been used. And
Such a ferromagnetic metal thin film type magnetic recording medium is available in a consumer video format (8 mm Hi-8 format, DV format) or a professional video format (DV format).
CAM) and the like.

This ferromagnetic metal thin film type magnetic recording medium is
Compared to the coating type magnetic recording medium, it has excellent magnetic properties such as coercive force, squareness ratio, etc., and not only excellent electromagnetic conversion characteristics in the short wavelength region, but also enables extremely thin magnetic layer, Because the thickness loss during recording demagnetization and reproduction is extremely small, and there is no need to mix a binder, which is a nonmagnetic material, into the magnetic layer, it is possible to increase the packing density of the magnetic material. Has the advantage of

In general, a magnetic recording medium is subjected to high-speed relative movement with a magnetic head in the process of recording / reproducing a magnetic signal, and at that time, the running must be performed smoothly and in a stable state. . Also, it is better that the wear and damage due to contact with the magnetic head be as small as possible.

However, in the above-mentioned ferromagnetic metal thin film type magnetic recording medium, since the surface smoothness of the magnetic layer is extremely good, a substantial contact area with the magnetic head is increased. In other words, so-called cracking tends to occur, the coefficient of friction increases, and there are many shortcomings in durability, running properties, and the like.

Therefore, for example, a lubricant is applied to the magnetic layer of the magnetic recording medium, that is, the surface of the ferromagnetic metal thin film,
Attempts have been made to improve durability and running properties. As a lubricant used for such a purpose, for example, an organic fluorine compound is known to be effective.

[0008] In particular, Japanese Patent Application Laid-Open No. 05-194970 and the like disclose that a perfluoropolyether ester compound having a hydroxyl group or a carboxyl group at the terminal is used as a lubricant to provide a good lubricating effect under any use conditions. A magnetic recording medium that performs is disclosed.

[0009]

By the way, in the magnetic recording medium of the ferromagnetic metal thin film type, a technique for forming a carbon protective film on the ferromagnetic metal thin film has been established in order to secure more excellent durability. Have been. The ferromagnetic metal thin film type magnetic recording medium used in the above-mentioned consumer video format DVC tape or professional video format DVCAM tape, and also in the tape streamer application AIT tape, etc. Magnetic recording media in which a carbon protective film is formed on a ferromagnetic metal thin film have been put to practical use. With the practical use of such a carbon protective film, the durability is sufficiently ensured, and it is considered that the presence of the carbon protective film will be indispensable in a future ferromagnetic metal thin film type magnetic recording medium.

The above carbon protective film is made of diamond liquor (DLC).
ke carbon) film, magnetron sputtering method,
PVD (Physical Vapor D) such as ion beam sputtering
eposition) and CVD (Chemical Vapor Depositio)
n) It is formed by a method or the like.

Here, when the carbon protective film is formed by the CVD method, high-speed film formation is possible, the coverage is high, and power saving is achieved as compared with the case where the carbon protective film is formed by the PVD method. And has the advantage of energy saving. That is, by forming the carbon protective film by the CVD method, high-speed film formation becomes possible and productivity is improved. Further, the corrosion resistance and rust resistance of the magnetic thin film layer are improved due to the high coverage of the carbon protective film. Further, the effect on the global environment can be reduced by power saving and energy saving.

However, the surface energy of the carbon protective film formed by the CVD method is smaller than that of the carbon protective film formed by the PVD method. Therefore, as described above,
If a lubricant is used to improve the durability and running properties of the magnetic recording medium, the adsorbability between the lubricant and the carbon protective film is weak, and a stable and good lubricating effect is not exhibited.
Therefore, it is necessary to design a lubricant in consideration of the existence of the carbon protective film.

Accordingly, the present invention has been proposed in view of such circumstances, and uses a lubricant that maintains a lubricating effect for a long period of time and improves the adhesion stability between the protective film and the lubricant. Accordingly, it is an object of the present invention to provide a magnetic recording medium that achieves excellent running properties and durability.

[0014]

A magnetic recording medium according to the present invention comprises a non-magnetic support, a magnetic layer formed on the non-magnetic support, a magnetic layer formed on the magnetic layer, and a surface of which is aromatic. A protective film top-coated with an alcohol, comprising an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid represented by the following formula (5) and a long-chain saturated fatty acid ester represented by the following formula (6): It is characterized in that the contained lubricant is held in the outermost layer.

[0015]

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[0016]

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In the magnetic recording medium according to the present invention as described above, since the surface of the protective film is provided with the protective film top-coated with an aromatic alcohol, the adhesion between the protective film and the lubricant is improved. I do. Further, in the magnetic recording medium according to the present invention, since the lubricant containing the compound represented by the above formula (5) and the compound represented by the above formula (6) is held in the outermost layer, the adhesiveness can be maintained under any use conditions. And good lubricity are maintained, and good running properties and durability are secured over a long period of time.

Further, the magnetic recording medium according to the present invention comprises a non-magnetic support, a magnetic layer formed on the non-magnetic support, a top layer formed on the magnetic layer and having a surface coated with an aromatic alcohol. A lubricant comprising a protective film formed by the above method, and an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol represented by the following chemical formula 7 and a long-chain saturated fatty acid ester represented by the following chemical formula 8 Is held in the outermost layer.

[0019]

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[0020]

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In the magnetic recording medium according to the present invention as described above, since the surface is provided with the protective film whose top surface is coated with the aromatic alcohol, the adhesion between the protective film and the lubricant is improved. Furthermore, in the magnetic recording medium according to the present invention, the lubricant containing the compound represented by the above formula (7) and the compound represented by the above formula (8) is held in the outermost layer. And good lubricity are maintained, and good running properties and durability are secured over a long period of time.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the magnetic recording medium according to the present invention will be described in detail.

<First Embodiment> FIG. 1 is a sectional view showing an example of a magnetic recording medium according to the present embodiment.

In this magnetic recording medium 1, as shown in FIG. 1, a ferromagnetic metal thin film is formed as a magnetic layer 3 on a nonmagnetic support 2, and a protective film 4 is formed as an outermost layer on the magnetic layer 3. Be done.

Examples of the nonmagnetic support 2 include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, polyvinyl chloride, polyvinylidene chloride. And plastics such as polycarbonate, polyimide, polyamide and polyamide-imide; light metals such as aluminum alloys and titanium alloys; and ceramics such as glass. Further, the form of the nonmagnetic support 2 may be any form such as a film, a sheet, a disk, a card, and a drum.

The non-magnetic support 2 may be one in which at least one kind of projection such as a mountain-like projection, a wrinkle-like projection, or a granular projection is formed on the surface to control the surface roughness.

More specifically, the mountain-like projections are formed, for example, by adding inorganic fine particles having a particle size of about 50 nm to 300 nm at the time of forming a polymer film, and the height from the polymer film surface is 10 nm. １００100 nm, and the density is about 1 × 10 ⁴ pieces / mm ² to 1 × 10 ⁵ pieces / mm ² .
As the inorganic fine particles for forming the mountain-like projections, for example, calcium carbonate, silica, alumina and the like are preferable.

The wrinkle-shaped protrusions are formed, for example, by applying and drying a dilute solution of a resin using a specific mixed solvent, and have a height of 0.01 μm to 1 μm.
0 μm, preferably 0.03 μm to 0.5 μm, and the shortest interval between projections is 0.1 μm to 20 μm.

Examples of the resin for forming the wrinkle-like projections include polyester such as polyethylene terephthalate and polyethylene naphthalate, polyamide, polystyrene, polycarbonate, polyacrylate, polysulfone, polyvinyl chloride, polyvinylidene chloride and polyvinyl butyral. , Polyphenylene oxide, phenoxy resin, and the like, a simple substance, a mixture or a copolymer, and those having a soluble solvent are suitable. Then, these resins are added to the good solvent at a resin concentration of 1 ppm to 1000 ppm.
A solution obtained by adding a solvent which is a poor solvent for the resin and has a boiling point higher than that of the good solvent to the solution dissolved in the above by 10 times to 100 times the amount of the resin is applied to the surface of the polymer film and dried. By doing so, a thin film having very fine wrinkle-like projections can be formed.

The granular projections are formed by adhering organic ultrafine particles such as acrylic resin or inorganic fine particles such as silica or metal powder in a spherical or hemispherical shape. The height of the granular projections is 5 nm to 50 nm, and the density is 1 × 10 ^6.
Pieces / mm ^{2 to about} 5 × 10 ⁷ pieces / mm ² .

By forming at least one kind of these projections, it is possible to control the surface properties of the ferromagnetic metal thin film as the magnetic layer 3, but the effect is increased by combining two or more kinds. In particular, when wrinkle-like protrusions and granular protrusions are formed on the nonmagnetic support 2 provided with the mountain-like protrusions,
Durability and running properties are significantly improved. In this case, the height of the entire projection is preferably in the range of 10 nm to 200 nm, and the density thereof is 1 × 10 ⁵ / mm ² to 1
It is preferably × 10 ⁷ pieces / mm ² .

The ferromagnetic metal thin film serving as the magnetic layer 3 includes, for example, metals such as Fe, Co, and Ni,
Co-Ni alloy, Co-Pt alloy, Co-Ni-Pt alloy, Fe-Co alloy, Fe-Ni alloy, Fe-Co-N
An i-alloy, an Fe-Co-B alloy, a Co-Ni-Fe-B alloy, a Co-Cr alloy, or a ferromagnetic metal material containing a metal such as Cr or Al in these alloys may be used. In particular, when a Co—Cr alloy is used, a perpendicular magnetization film is formed.

The ferromagnetic metal thin film as the magnetic layer 3 is formed as a continuous film by a vacuum thin film forming technique such as a vacuum deposition method, an ion plating method, and a sputtering method.

The above-mentioned vacuum deposition method is performed in the range of 1 × 10 ⁻² Pa to 1 ×
The ferromagnetic metal material is evaporated under a vacuum of 10 ^-6 Pa by resistance heating, high-frequency heating, electron beam heating, or the like, and the evaporated metal (ferromagnetic metal material) is deposited on the nonmagnetic support 2. Non-magnetic support 2 to obtain high coercive force
In contrast, oblique evaporation in which the ferromagnetic metal material is obliquely evaporated is used. Further, the above-mentioned vapor deposition in an oxygen atmosphere to obtain a higher coercive force is also included.

The above-mentioned ion plating method is also a kind of the vacuum evaporation method, and causes a DC glow discharge and an RF glow discharge in an inert gas atmosphere of 1 × 10 ⁻² Pa to ¹ × 10 ⁻¹ Pa. In this, the magnetic metal material is evaporated.

In the above sputtering method, 1 × 10 ^-1 Pa
A glow discharge is caused in an atmosphere containing an argon gas as a main component of up to 1 × 10 Pa, and atoms of the target surface are knocked out by the generated argon gas ions. And a high-frequency sputtering method or a magnetron sputtering method using magnetron discharge. In the case of using this sputtering method, a base film such as Cr, W, and V may be formed.

In any of the above methods, Bi, Sb, Pb, Sn, Ga, I
By forming a base metal layer such as n, Cd, Ge, Si, Tl, etc. in advance and forming the film in a direction perpendicular to the surface of the nonmagnetic support 2, there is no orientation of magnetic anisotropy. The magnetic layer 3 having excellent in-plane isotropy can be formed, which is suitable when the magnetic recording medium 1 is, for example, a magnetic disk. The thickness of the ferromagnetic metal thin film formed by such a method is preferably 0.01 μm to 1 μm.

The protective film 4 is made of carbon and has a magnetic layer 3
Is formed on the ferromagnetic metal thin film. In particular, the protective film 4
A preferable example is a material made of diamond-like carbon having relatively high hardness.

This protective film 4 is formed by a CVD method or the like. When the protective film 4 is formed by the CVD method,
For example, a hydrocarbon gas or a mixed gas of a hydrocarbon and an inert gas is introduced into a vacuum vessel, and 10 Pa to 100 Pa.
With the pressure maintained at about Pa, a discharge is generated in the vacuum vessel to generate a hydrocarbon gas plasma, and the protective film 4 is formed on the ferromagnetic metal thin film.

The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency can be experimentally determined. Further, an electrode disposed on the nonmagnetic support 2 side on which the ferromagnetic metal thin film is formed has a voltage of 0 to -3 kV.
By applying the voltage, the hardness of the protective film 4 can be increased and the adhesion can be improved.

As the above-mentioned hydrocarbon used as the material of the protective film 4, for example, methane, ethane, propane, butane, pentane, hexane, heptane, octane, ethylene, acetylene, propene, butene, pentene, benzene and the like can be used. it can.

The protective film 4 has a thickness of about 3 nm to 15 nm, particularly 5 nm to 1 nm, so that the spacing loss is reduced and the effect of preventing abrasion of the ferromagnetic metal thin film is obtained.
It is preferably about 0 nm.

The surface of the protective film 4 is top-coated with an aromatic alcohol. Specifically, examples of the aromatic alcohol include phenols and / or naphthols.

As the phenols, dihydric phenols,
Examples thereof include alkylphenol and nitrosophenol.

Examples of the dihydric phenol include pure phenols such as hydroquinone, resorcinol and catechol, and alkylamino, nitro and halogeno-substituted products thereof, for example, 2-methylhydroquinone, 4-methylresorcinol, 5-methylresorcinol, 4-methylresorcinol and 4-methylresorcinol. Methylpyrocatechol, 2,5-dimethylhydroquinone, 4,6-dimethylresorcinol, 2,5-dimethylresorcinol, 2-isopropyl-5-methylhydroquinone,
-Tert-butylhydroquinone, 2,5-di-te
rt-butylhydroquinone, 4-tert-butylcatechol, 2-aminoresorcinol, 2-resorcinol, 2,5-dichlorohydroxyquinone and the like.

The above-mentioned alkylphenol refers to an alkyl-substituted monohydric phenol, for example, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, 2,3 -Dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, 2,
4,6-trimethylphenol, 2,4,5-trimethylphenol, 5-isopropyl-2-methylphenol, p-tert-butylphenol, 2,6-di-t
tert-butyl-p-cresol, 4,4'-methylenebis-2,6-di-tert-butylphenol, 2,
6-dimethyl-4-tert-butylphenol, 2,
4,6-tri-tert-butylphenol and the like.

Examples of the above nitrosophenol include 4-nitroso-2-methoxy-1-phenol,
-Nitroso-2-ethoxy-1-phenol, 6-nitroso-o-cresol, 4-nitroso-m-cresol, o-nitrosophenol, p-nitrosophenol, 2-nitrosoresorcin, 4-nitrosoresorcin and the like. .

The naphthols include α-naphthol, β-naphthol, 1,2-naphthalenediol,
1,3-naphthalene diol, 1,4-naphthalene diol, 1,5-naphthalene diol, 1,7-naphthalene diol, 1,8-naphthalene diol, 2,3-naphthalene diol, 1,4,5-naphthalene triol Naphthols such as 1,1,2,5,8-naphthalenetetraol and nitro, nitroso, amino, halogeno-substituted naphthols, for example, 1-chloro-2-naphthol, 2,4-dichloro-1-naphthol, 1 -Nitro-
2-naphthol, 1,6-dinitro-2-naphthol,
1-nitroso-2-naphthol, 2-nitroso-1-naphthol, 1-amino-2-naphthol and the like can be mentioned.

It is preferable that the amount of the aromatic alcohol to be applied is determined depending on the degree of oxidation on the surface of the protective film 4. As a specific application amount,
Is preferably ^{0.05mg / m 2 ~100mg / m 2} , further more preferably ^{0.1mg / m 2 ~50mg / m 2} .

In particular, in the magnetic recording medium 1, a perfluoropolyether having a hydroxyl group at a terminal represented by the following formula 9 is formed on the protective film 4 as the outermost layer via a top coat made of an aromatic alcohol. A lubricant containing an ester compound with a chain carboxylic acid and a long-chain saturated fatty acid ester represented by the following formula 10 is retained.

[0051]

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[0052]

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The compound represented by Chemical formula 9 and Chemical formula 1
The lubricant having the compound represented by No. 0 has properties such that the adhesion and the lubricity are suitably maintained under any use conditions and the lubricating effect is maintained for a long time.

The ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid shown in the above-mentioned chemical formula 9 can be obtained, for example, by mixing a perfluoropolyether having a hydroxyl group at a terminal with a long-chain carboxylic acid chloride in toluene. By reacting with a base as a catalyst.

The perfluoropolyether having a hydroxyl group at the terminal is preferably one having a hydroxyl group at both terminals. For example, HO-CH ₂ CF ₂ (OC
_{2 F 4) p (OCF 2} ) q OCF 2 CH 2 -OH ( Here, p in the formula, q represents an even integer of 1 or more either.), And the like. The above-mentioned perfluoropolyether having a hydroxyl group at the terminal is, of course, not limited to these.

The molecular weight of the above-mentioned perfluoropolyether having a hydroxyl group at the terminal is not particularly limited, but practically preferably about 600 to 5000.
If the molecular weight is too large, the effect of the terminal group as an adsorptive group is diminished, and at the same time, the perfluoropolyether chain becomes large, so that it becomes difficult to dissolve in existing hydrocarbon solvents. Conversely, if the molecular weight is too small, the lubricating effect of the perfluoropolyether chain will be lost.

In the perfluoropolyether having a hydroxyl group at the terminal, the perfluoropolyether chain may be partially hydrogenated. That is, a part (50% or less) of the fluorine atoms of the perfluoropolyether chain may be replaced with a hydrogen atom. In this case, a partially hydrogenated perfluoropolyether may be used as the perfluoropolyether.

On the other hand, as the long-chain carboxylic acid chloride, either a commercial product or a synthetic product can be used. Thus, an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid, which is synthesized by reacting a perfluoropolyether having a terminal hydroxyl group with a long-chain carboxylic acid chloride, 9 is a compound.

The long-chain carboxylic acid, that is, the carboxylic acid portion of the long-chain carboxylic acid chloride of the synthetic material may have any structure having a carboxylic acid group, for example, a branched structure, an isomer structure, or an alicyclic structure. , Regardless of the presence or absence of unsaturated bonds. Also, this long-chain carboxylic acid is
The molecular weight is also arbitrary, but it is preferable that at least the alkyl group has 10 or more carbon atoms because it becomes difficult to dissolve in a general hydrocarbon-based organic solvent as the molecular weight decreases.

As described above, the lubricant used in the present invention includes, in addition to the compound represented by the above formula (9),
0 long-chain saturated fatty acid ester is contained.

As the long-chain saturated fatty acid ester, those having a total of 15 to 35 carbon atoms in two alkyl groups are preferable. Specifically, hexyl laurate (C ₁₁ H ₂₃ C
OOC ₆ H ₁₃ ), heptyl laurate (C ₁₁ H ₂₃ COO)
C ₇ H ₁₅ octyl laurate (C ₁₁ H ₂₃ COOC ₈ H
₁₇ ), decyl laurate (C ₁₁ H ₂₃ COOC ₁₀ H ₂₁ ),
Heptyl myristate (C ₁₃ H ₂₇ COOC ₇ H ₁₅ ), octyl myristate (C ₁₃ H ₂₇ COOC ₈ H ₁₇ ), decyl myristate (C ₁₃ H ₂₇ COOC ₁₀ H ₂₁ ), butyl palmitate (C ₁₅ H ₃₁₎ COOC ₄ H ₉ ), heptyl palmitate (C ₁₅ H ₃₁ COOC ₇ H ₁₅ ), decyl palmitate (C ₁₅ H ₃₁ COOC ₁₀ H ₂₁ ), butyl stearate (C ₁₇ H ₃₅ COOC ₄ H ₉ ), stearic acid Pentyl (C ₁₇ H ₃₁ COOC ₅ H ₁₁ ), heptyl stearate (C ₁₇ H ₃₅ COOC ₇ H ₁₅ ), octyl stearate (C ₁₇ H ₃₅ COOC ₈ H ₁₇ ), decyl stearate (C
₁₇ H ₃₅ COOC ₁₀ H ₂₁ ).

It is preferable that the total number of carbon atoms of R ^I and R ^II in the long-chain saturated fatty acid ester shown in Chemical formula 10 is 15 to 35. The total number of carbon atoms of R ⁱ and R ^II is 1
If it is less than 5, the lubricating effect is poor and there is no effect on the still durability. If the total number of carbon atoms of R ^I and R ^II exceeds 35, the solubility in the organic solvent becomes small and the uniform lubricant coating layer is formed. Is difficult to form.

It is important that the fatty acid ester is selected from saturated fatty acid esters. Saturated fatty acid esters can maintain the initial lubricating properties even during long-term storage.

Here, the lubricant used for the magnetic recording medium 1 includes an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid as shown in Chemical formula 9 and a long-chain saturated compound as shown in Chemical formula 10. The mixing ratio with the fatty acid ester is preferably from 10:90 to 90:10 by weight. Exceeding the above range makes it difficult to obtain the effects of the present invention.

As a method for retaining the lubricant in the outermost layer in the magnetic recording medium 1, there is a method in which the lubricant is top-coated on the surface of the protective film 4. Here, the coating amount is preferably from ^{0.05mg / m 2 ~100mg / m 2} , and more preferably ^{0.1mg / m 2 ~50mg / m 2} . If this amount is too small,
The effect of lowering the coefficient of friction, improving wear resistance and durability is not exhibited, and if this coating amount is too large, a shearing phenomenon occurs between the sliding member and the ferromagnetic metal thin film,
On the contrary, the running performance deteriorates.

As described above, the magnetic recording medium 1 according to the present embodiment specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity as described above. Therefore, good running performance and durability are ensured.

Further, in the magnetic recording medium 1, a protective film 4 made of carbon is formed as the outermost layer, and the surface thereof is top-coated with an aromatic alcohol. Adhesion with the protective film 4 is improved, and better durability can be realized.

Further, in the magnetic recording medium 1, since the magnetic layer 3 is formed of a ferromagnetic metal thin film, it can sufficiently cope with high-density recording and long-time recording.

Further, in the magnetic recording medium 1 of the present invention, a so-called backcoat layer may be formed on the surface of the nonmagnetic support 2 opposite to the surface on which the magnetic layer 3 is formed. This back coat layer is formed by applying a back coat paint in which a binder resin and a powder component are mixed and dispersed in an organic solvent to the non-magnetic support 2.

The binder resin used in the backcoat paint includes, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic Acid ester-acrylonitrile copolymer, thermoplastic polyurethane elastomer, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, polyester resin, phenol resin, epoxy resin, polyurethane-curable resin , Melamine resin, alkyd resin, silicone resin, epoxy-polyamide resin,
Nitrocellulose-melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of methacrylate copolymer and diisocyanate prepolymer, mixture of polyester polyol and polyisocyanate, urea formaldehyde resin, low molecular weight glycol / high molecular weight diol / Triphenylmethane triisocyanate, polyamine resins, and mixtures thereof.

Alternatively, a binder resin having a hydrophilic polar group may be used in order to improve the dispersibility of the powder component.

On the other hand, examples of the powder component include a carbon-based fine powder for imparting conductivity and an inorganic pigment added for controlling surface roughness and improving durability. Examples of the carbon-based fine particles include furnace carbon, channel carbon, acetylene carbon, thermal carbon, and lamp carbon.
As the inorganic pigment, α-FeOOH, α-Fe
₂ O ₃ , Cr ₂ O ₃ , TiO ₂ , ZnO, SiO, SiO ₂ ,
_{SiO 2 · 2H 2 O, Al} 2 O 3, CaCO 3, MgCO 3,
Sb ₂ O _{3 and the} like.

Further, examples of the organic solvent for the back coat paint include acetone, methyl ethyl ketone,
Methyl isobutyl ketone, ketone solvents such as cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, ester solvents such as glycol acetate monoethyl ether, glycol dimethyl ether, glycol monoethyl ether, glycol ether solvents such as dioxane, Aromatic hydrocarbon solvents such as benzene, toluene, and xylene; aliphatic hydrocarbon solvents such as hexane and heptane; chlorinated carbonization such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene A general-purpose solvent such as a hydrogen-based solvent can be used.

Further, a lubricant may be used in combination with the back coat layer. In this case, there is a method of internally adding a lubricant to the back coat layer, or a method of applying a lubricant on the back coat layer. In any case, the lubricants include fatty acids, fatty acid esters, fatty acid amides,
Metal soaps, fatty alcohols, silicone lubricants, etc.
Conventionally known lubricants can be used.

The magnetic recording medium 1 according to the present embodiment as described above is manufactured as follows.

First, a ferromagnetic metal thin film serving as the magnetic layer 3 is formed on the nonmagnetic support 2 by, for example, a vacuum evaporation method.
Thereafter, a protective film 4 is formed on the magnetic layer 3 by, for example, a plasma CVD method. Further, the surface of the protective film 4 is top-coated with an aromatic alcohol.
Then, the above-described lubricant is applied on the protective film 4 to hold the lubricant on the protective film, and the magnetic recording medium 1 is obtained. It is needless to say that a back coat layer or the like may be formed as necessary.

More specifically, as a vacuum deposition apparatus for forming the magnetic layer, there is a continuous winding type vacuum deposition apparatus as shown in FIG.

This vacuum vapor deposition apparatus is configured for so-called oblique vapor deposition, and is cooled to, for example, about −20 ° C. in a vacuum chamber 11 in which the inside is evacuated to, for example, about 1 × 10 ⁻³ Pa. The cooling can 12 rotates counterclockwise as shown by an arrow A, and the evaporation source 13 for a ferromagnetic metal thin film is disposed to face the cooling can 12.

Further, in this vacuum evaporation apparatus, a supply roll 14 rotating in a counterclockwise direction in the drawing and a winding roll 15 rotating in a counterclockwise direction in the drawing are also arranged in the vacuum chamber 11. The non-magnetic support 16 is unreeled from the supply roll 14 in the direction indicated by the arrow B in the drawing, travels along the peripheral surface of the cooling can 12, and
5 is wound up.

Note that guide rollers 17 and 18 are disposed between the supply roll 14 and the cooling can 12 and between the cooling can 12 and the take-up roll 15, respectively. A predetermined tension is applied to the non-magnetic support 16 running from the cooling can 12 according to the take-up roll 15, and the non-magnetic support 16
Is designed to run smoothly.

The evaporation source 13 is a container such as a crucible or the like in which a ferromagnetic metal material such as Co is stored. In this vacuum evaporation apparatus, the ferromagnetic metal material of the evaporation source 13 is heated and evaporated. Is also provided. In other words, the ferromagnetic metal material of the evaporation source 13 is acceleratedly irradiated with the electron beam 20 from the electron beam source 19, and the ferromagnetic metal material is heated and evaporated as shown by the arrow C in the figure. Then, the ferromagnetic metal material is deposited on the nonmagnetic support 16 running along the peripheral surface of the cooling can 12 facing the evaporation source 13, and a ferromagnetic metal thin film is formed on the nonmagnetic support 16. It will be.

In the above-mentioned vacuum vapor deposition apparatus, a deposition-preventing plate 21 is provided between the vapor deposition source 13 and the cooling can 12, and a shutter 22 is provided on the deposition-preventing plate 21 so as to be adjustable in position.
Only the vapor-deposited particles incident on the non-magnetic support 16 at a predetermined angle are passed. Thus, the ferromagnetic metal thin film is formed by the oblique deposition method.

Further, during the deposition of such a ferromagnetic metal thin film, an oxygen gas is supplied to the vicinity of the surface of the nonmagnetic support 16 through an oxygen gas inlet (not shown), whereby the magnetic properties and It is preferable to improve durability and weather resistance. In addition, in order to heat the evaporation source, known means such as a resistance heating means, a high-frequency heating means, and a laser heating means can be used in addition to the above-described heating means using an electron beam.

Here, an example in which a ferromagnetic metal thin film made of Co is formed by the oblique evaporation method has been described.
A conventionally known thin film forming method such as a vertical vapor deposition method or a sputtering method can be applied, and as a material of the ferromagnetic metal thin film, Ni, Fe, or an alloy thereof can be used in addition to Co. At this time, the thickness of the ferromagnetic metal thin film is preferably about 0.01 μm to 1 μm.

Next, a method for forming the protective film 4 will be described. The protection film 4 is formed by a CVD method or the like.

In the case of forming the protective film 4 by the CVD method, first, a hydrocarbon gas or a mixed gas of a hydrocarbon and an inert gas is introduced into a vacuum vessel, and 10 Pa to 1 Pa.
While maintaining the pressure at about 00 Pa, discharge is performed in the vacuum vessel to generate a plasma of hydrocarbon gas, and the protective film 4 is formed on the ferromagnetic metal thin film. As a discharge type,
Either the external electrode method or the internal electrode method may be used, and the discharge frequency can be experimentally determined. Also,
By applying a voltage of 0 to -3 kV to the electrode disposed on the nonmagnetic support 2 side on which the ferromagnetic metal thin film is formed, the hardness of the protective film 4 can be increased and the adhesion can be improved.

As the above-mentioned hydrocarbon used as the material of the protective film 4, for example, methane, ethane, propane, butane, pentane, hexane, heptane, octane, ethylene, acetylene, propene, butene, pentene, benzene and the like can be used. it can.

The protective film 4 has a thickness of about 3 nm to 15 nm, particularly 5 nm to 5 nm, so that the spacing loss is reduced and the effect of preventing the ferromagnetic metal thin film from being worn is obtained.
Preferably, the thickness is about 10 nm.

Here, an example in which the protective film is formed by the CVD method has been described. However, as a method of forming the protective film 4, in addition to this method, magnetron sputtering, ion beam sputtering, ion beam plating, and the like. And the like.

Then, the surface of the protective film 4 is top-coated with an aromatic alcohol. By top-coating the surface of the protective film 4 with an aromatic alcohol, the adhesion between the protective film 4 and the lubricant applied on the protective film 4 can be improved.

<Second Embodiment> Next, a second embodiment of the present invention will be described. The magnetic recording medium according to the present embodiment, like the magnetic recording medium 1 according to the first embodiment shown in FIG. 1, has a ferromagnetic metal thin film as a magnetic layer on a non-magnetic support and a protective layer as an outermost layer. Films are sequentially formed. The magnetic recording medium according to the present embodiment has, in particular, an outermost protective film, an ester compound of a perfluoropolyether having a carboxyl group at a terminal represented by the following formula 11 and a long-chain alcohol, A lubricant containing a long-chain saturated fatty acid ester represented by Chemical formula 12 is retained.

[0092]

Embedded image

[0093]

Embedded image

The lubricant containing the compound represented by the chemical formula (11) and the compound represented by the chemical formula (12) can maintain good adhesion and lubricity under any use conditions and can maintain the lubricating effect for a long period of time. It has the following characteristics.

The magnetic recording medium using the lubricant shown in Chemical formulas 11 and 12 has substantially the same structure as the magnetic recording medium 1 shown in FIG. 1, and is held in the outermost layer. This is an example in which only the lubricant is different, and the other magnetic layers, protective films, and the like have the same configuration. Therefore, in the following description, only the lubricant will be described.

The ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol represented by the above formula 11 is, for example, a compound of perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol.
It is obtained by reacting in anhydrous toluene using p-toluenesulfonic acid, concentrated sulfuric acid or the like as a catalyst.

The perfluoropolyether having a carboxyl group at the terminal is preferably a compound having a carboxyl group at both terminals.
_{C-CF 2 (OC 2 F} 4) m (OCF 2) j OCF 2 -COO
H (however, m and j in the above chemical formulas each represent an integer of 1 or more). The above-mentioned perfluoropolyether having a terminal carboxyl group is, of course, not limited to these.

The molecular weight of the perfluoropolyether having a carboxyl group at the terminal is not particularly limited, but is practically preferably about 600 to 5000. If the molecular weight is too large, the effect of the terminal group as an adsorbing group is diminished, and the perfluoropolyether chain becomes large, so that it becomes difficult to dissolve in an existing hydrocarbon solvent. On the other hand, if the molecular weight is too small, the lubricating effect of the perfluoropolyether chain will be lost.

In the perfluoropolyether having a carboxyl group at the terminal, the perfluoropolyether chain may be partially hydrogenated. That is, a part of the fluorine atoms of the perfluoropolyether chain (50%
Below) may be replaced by a hydrogen atom. In this case, a partially hydrogenated perfluoropolyether may be used as the perfluoropolyether.

On the other hand, as the long-chain alcohol, either a commercial product or a synthetic product can be used. In addition, it is preferable that at least one of the alkyl groups has 6 or more carbon atoms because the molecular weight of the alkyl group becomes difficult to dissolve in an ordinary organic solvent as the molecular weight decreases.

Further, as described above, the lubricant used in the present embodiment contains a long-chain saturated fatty acid ester represented by Chemical Formula 12 in addition to the compound represented by Chemical Formula 11. As the long-chain saturated fatty acid ester shown in Chemical formula 12, the same as the long-chain saturated fatty acid ester described in the first embodiment can be used.

Here, in the lubricant used in the magnetic recording medium of the present invention, an ester compound of perfluoropolyether having a carboxyl group at a terminal shown in Chemical formula 11 and a long-chain alcohol is used. The mixing ratio with the chain saturated fatty acid ester is 10:90 to 90:10 by weight.
It is preferred that Exceeding the above range makes it difficult to obtain the effects of the present invention.

The method of retaining the lubricant in the outermost layer is the same as that of the lubricant in the magnetic recording medium 1 described above, and includes a method of top-coating the lubricant on the surface of the protective film. Here, the coating amount is 0.05
is preferably from ^{mg / m 2 ~100mg / m 2} , 0.
1 mg / m ² and more preferably to 50 mg / m ^2.
If the coating amount is too small, the effect of lowering the coefficient of friction and improving wear resistance and durability will not be exhibited, and if the coating amount is too large, the sliding member and the ferromagnetic metal thin film will not have the same effect. A cracking phenomenon occurs between the two, which results in poor running performance.

As described above, the magnetic recording medium according to the present embodiment specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity as described above. Thus, good running performance and durability are ensured.

Further, in this magnetic recording medium, since the surface of the protective film made of carbon is top-coated with aromatic alcohol, which is formed as the outermost layer, the adhesion between the lubricant used and the protective film is improved. Thus, it is possible to improve the durability.

Further, in this magnetic recording medium, since the magnetic layer is formed of a ferromagnetic metal thin film, high density recording,
It can be used for long time recording.

[0107]

EXAMPLES Examples of the present invention will be described below based on specific experimental results. In this example, a magnetic recording medium was actually manufactured and its characteristics were evaluated.

Experimental Example 1 In this experimental example, the effects of using an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid and a lubricant containing a long-chain saturated fatty acid ester were as follows. I confirmed it.

(Preparation of Sample) Synthesis of ester compound of perfluoropolyether having a hydroxyl group at a terminal and long-chain carboxylic acid First, as a perfluoropolyether having a hydroxyl group at a terminal, HOCH ₂ CF ₂ having a molecular weight of 2000 (OC ₂ F)
₄ ) _p (OCF ₂ ) _q OCF ₂ CH ₂ OH (where p and q each represent an integer of 1 or more in the chemical formula)
Triethylamine, which is twice the molar ratio of this perfluoropolyether, is dissolved in an organic solvent, and stearic acid chloride, which is twice the molar ratio, is further added to the solution.
It was added dropwise over 0 minutes.

After completion of the dropwise addition, the mixture was stirred for 1 hour, and then heated under reflux for 30 minutes. And after cooling, it wash | cleaned in order of distilled water and dilute hydrochloric acid aqueous solution, and wash | cleaned again with distilled water until the washing | cleaning liquid became neutral. Subsequently, the organic solvent was removed, and the obtained compound was purified using silica gel column chromatography to obtain an ester compound. Here, this ester compound is referred to as Compound 1.

Next, four kinds of compounds 2 to 5 which are ester compounds of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid as shown in Table 1 were synthesized by the same synthesis method as that of the above-mentioned compound 1. Synthesized. In Table 1, p, q, and n each represent an integer of 1 or more.

[0112]

[Table 1]

[0113] 2. Preparation of Sample Tape Next, a magnetic tape was prepared as follows. First,
A ferromagnetic metal thin film serving as a magnetic layer is formed to a thickness of 180 nm on a 7.0 μm thick polyethylene terephthalate film, which is a nonmagnetic support, by oblique deposition using the above-described vacuum deposition apparatus. did.

Next, on the ferromagnetic metal thin film, high-frequency plasma of a mixed gas of ethylene and argon was used to form an electrode and a magnetic recording medium raw material itself as a counter electrode.
A DC voltage of 1.5 kV was applied to perform discharge, and a carbon protective film having a thickness of about 8 nm was formed on the ferromagnetic metal thin film.

Next, on the surface of the polyethylene terephthalate film opposite to the surface on which the ferromagnetic metal thin film is formed,
0.5 μm thickness of carbon and polyurethane resin
Was formed.

Next, a solution prepared by dissolving an aromatic alcohol shown in Table 2 below in isopropyl alcohol was applied on the carbon protective film so that the coating amount was 2 mg / m ² .

Next, each of the compounds shown in the following Table 2 dissolved in a hexane solvent was applied on the carbon protective film so that the coating amount was 5 mg / m ^2, and 18
Various types of magnetic recording media were obtained.

Then, these 18 types of magnetic recording media were cut to a width of 6.35 mm, respectively, to obtain 18 types of sample tapes of Examples 1 to 8 and Comparative Examples 1 to 10.

However, for the sample tapes of Comparative Examples 3 to 10, no aromatic alcohol was applied to the surface of the protective film. Further, with respect to the sample tapes of Comparative Examples 8 to 10, the protective film was formed not by the plasma CVD method as described above but by a magnetron sputtering method.

[0120]

[Table 2]

3. Evaluation of Characteristics Next, the above Examples 1 to 8 and Comparative Examples 1 to 10
The characteristics of the 18 types of sample tapes were evaluated. Here, the durability and running performance were evaluated, and specifically, the friction coefficient, still durability and shuttle durability were evaluated.
As environmental conditions for evaluating these, the inventors considered the conditions and adopted the conditions considered to be the most severe conditions.

(1) Method of measuring coefficient of friction The coefficient of friction was measured at a temperature of 40 ° C.
The humidity was controlled at 80% RH, and the measurement was carried out by running each sample tape for 100 passes in this thermostat. In addition, the numerical value of the 100th pass of friction running was defined as the friction coefficient.

(2) Still Durability Measurement Method Still durability evaluation was performed in a thermostat at -5 ° C., and a commercially available digital video camcorder (manufactured by Sony Corporation, model name:
Using DCR-VX1000), the time required for the reproduction output of each sample tape to drop by 3 dB was measured.

(3) Method of Measuring Shuttle Durability Shuttle durability is determined by measuring the environmental conditions in a thermostat at a temperature of 40 ° C.
The humidity is controlled at 20% RH, and a commercially available digital video camcorder (model name: DCR, manufactured by Sony Corporation) is controlled in this thermostat.
-VX1000), each sample tape was run for 100 pass shuttles, and after running for 100 passes, how many dB the reproduction output dropped from the initial output was measured and evaluated.

These evaluations were carried out immediately after the lubricant was applied, and at a temperature of 45 ° C. and a humidity of 80% R
The test was performed after storing for 30 days in an environment of H. Table 3 shows the measurement results of the initial durability and running properties immediately after the application of the lubricant, and Table 4 shows the measurement results of the durability and running properties after storage after storage for 30 days.

[0126]

[Table 3]

[0127]

[Table 4]

From the results shown in Tables 3 and 4, the surface of the protective film formed by the CVD method was top-coated with an aromatic alcohol, and as a lubricant, a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid were used. In Examples 1 to 8 using a lubricant in which an ester compound and a long-chain saturated fatty acid ester were combined, the friction coefficient and still durability under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature It was found that there was very little deterioration in the durability and shuttle durability, and very good results were obtained.

On the other hand, in Comparative Examples 1 and 2 using a lubricant containing only an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid,
Under various conditions of use, the coefficient of friction, still durability, and shuttle durability deteriorated significantly. Comparative Examples 3 to 3 in which the surface of the protective film was not coated with the aromatic alcohol
In Comparative Example 10, the friction coefficient, still durability, and shuttle durability deteriorated greatly under various use conditions, and good results were not obtained. Further, when the protective film is formed not by the CVD method but by the magnetron sputtering method which is the PVD method, sufficient durability cannot be obtained.

From the above results, the surface of the protective film was treated with an aromatic alcohol, and as a lubricant, an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid, and a long-chain saturated fatty acid ester were used. In combination, the lubricant maintains good adhesion and lubricity under any use conditions, and since the lubrication effect is maintained for a long period of time, it is possible to obtain good running properties and durability of the magnetic recording medium. all right.

Experimental Example 2 In this experimental example, the effect of using an ester compound of a perfluoropolyether having a carboxyl group at the terminal and a long-chain alcohol and a lubricant containing a long-chain saturated fatty acid ester will be described below. Confirmed as follows.

(Preparation of Sample) Synthesis of ester compound of perfluoropolyether having terminal carboxyl group and long-chain alcohol First, as a perfluoropolyether having terminal carboxyl group, HOOCCF ₂ (O
Using C ₂ F ₄ ) _p (OCF ₂ ) _q OCF ₂ COOH (where p and q each represent an integer of 1 or more), the molar ratio of this perfluoropolyether is twice equivalent. Stearyl alcohol was heated to reflux in anhydrous toluene using a small amount of p-toluenesulfonic acid and concentrated sulfuric acid as catalysts. At this time, the reaction was performed while removing generated water.

After completion of the reaction, toluene was removed, and the obtained compound was purified by silica gel column chromatography, and then the solvent was removed to obtain an ester compound. Here, this ester compound is referred to as Compound 6.

Next, four kinds of compounds 7 to 10 which are ester compounds of a perfluoropolyether having a terminal carboxyl group and a long-chain alcohol as shown in Table 5 were synthesized in the same manner as in the above-mentioned compound 6. Synthesized. In Table 5, p, q, and n each represent an integer of 1 or more.

[0135]

[Table 5]

[0136] 2. First, a ferromagnetic metal thin film to be a magnetic layer and a protective film made of carbon were formed on a nonmagnetic support by a plasma CVD method, and a back coat layer was formed in the same manner as in Experimental Example 1 described above. . Further, the surface of the protective film was coated with a solution prepared by dissolving an aromatic alcohol in isopropyl alcohol as shown in Table 6 below in an amount of 2 mg on the carbon protective film.
/ M ² .

Next, in the same manner as in Experimental Example 1 described above, a solution in which a lubricant shown in Table 6 below was dissolved in a hexane solvent was applied to the surface of the protective film so that the coating amount was 5 mg / m ^2. To obtain 18 types of magnetic recording media.

Then, these 18 types of magnetic recording media were cut to a width of 6.35 mm, respectively.
18 and 18 types of sample tapes of Comparative Examples 11 to 20 were produced.

However, for the sample tapes of Comparative Examples 13 to 20, no aromatic alcohol was applied to the surface of the protective film. Further, with respect to the sample tapes of Comparative Examples 18 to 20, the protective film was formed not by the above-described plasma CVD method but by the magnetron sputtering method.

[0140]

[Table 6]

3. Evaluation of Characteristics Next, the characteristics of the 18 types of sample tapes of Examples 9 to 16 and Comparative Examples 11 to 20 were evaluated. Here, the durability and the running property were evaluated. Specifically, the friction coefficient, the still durability, and the shuttle durability were evaluated in the same manner as in Experimental Example 1.

These evaluations were performed immediately after the lubricant was applied in the same manner as in Experimental Example 1 and after each sample tape was stored for 30 days in an environment at a temperature of 45 ° C. and a humidity of 80% RH. Table 7 shows the results of the initial durability and running properties immediately after the application of the lubricant, and Table 8 shows the results of the durability and running properties after storage after storage for 30 days.

[0143]

[Table 7]

[0144]

[Table 8]

From the results shown in Tables 7 and 8, the surface of the protective film formed by the CVD method was top-coated with an aromatic alcohol, and as a lubricant, a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol were used. In Examples 9 to 16 using a lubricant in which an ester compound and a long-chain saturated fatty acid ester were combined,
In any case, under various conditions of use such as high temperature and high humidity, high temperature and low humidity, and low temperature, the friction coefficient, still durability and shuttle durability were extremely little deteriorated, and it was found that very good results were obtained.

On the other hand, in Comparative Examples 11 and 12 using a lubricant containing only an ester compound of a perfluoropolyether having a carboxyl group at the terminal and a long-chain alcohol, the friction coefficient and The deterioration of still durability and shuttle durability was extremely large.
Further, in Comparative Examples 13 to 20 in which the aromatic alcohol was not applied to the surface of the protective film, the friction coefficient, still durability, and shuttle durability greatly deteriorated under various use conditions, and good results were obtained. I couldn't. Further, when the protective film is formed not by the CVD method but by the magnetron sputtering method which is the PVD method, sufficient durability cannot be obtained.

From the above results, the surface of the protective film was top-coated with an aromatic alcohol, and further, as a lubricant, an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol, and a long-chain saturated fatty acid ester In combination, the lubricant maintains good adhesion and lubricity under any use conditions and maintains the lubricating effect for a long period of time, so that good running properties and durability of the magnetic recording medium can be obtained. I understood.

[0148]

As described above in detail, the magnetic recording medium according to the present invention specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity. Runability and durability can be improved. Also,
In the magnetic recording medium according to the present invention, the surface of the protective film made of carbon is formed as the outermost layer, and the surface of the protective film is treated with the aromatic alcohol. Properties can be improved, and more favorable durability can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a magnetic recording medium according to the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a vacuum evaporation apparatus used when forming a magnetic layer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Magnetic recording medium, 2 Non-magnetic support, 3 Magnetic layer, 4 Protective film

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroshi Yatakai 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F-term (reference) 4H104 BB32A BD07A CD04A LA20 PA16 5D006 AA01 AA02 AA06 BB01 EA03 FA02 FA05 FA06

Claims (14)

[Claims] A non-magnetic support, a magnetic layer formed on the non-magnetic support, and a protective film formed on the magnetic layer and having a surface top-coated with an aromatic alcohol, A lubricant containing an ester compound of a perfluoropolyether having a hydroxyl group at a terminal at the terminal represented by the following formula 1 and a long-chain carboxylic acid and a long-chain saturated fatty acid ester represented by the following formula 2 is retained in the outermost layer. A magnetic recording medium characterized by the above-mentioned. Embedded image Embedded image 2. An ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid,
The mixing ratio with the long-chain saturated fatty acid ester is 1 by weight.
The ratio is 0:90 to 90:10.
The magnetic recording medium according to the above. Wherein said R ^I of the long chain saturated fatty acid ester represented by the chemical formula 2, the total number of carbon atoms of R ^{I I} 15 to 35
The magnetic recording medium according to claim 1, wherein 4. The magnetic recording medium according to claim 1, wherein said magnetic layer is made of a ferromagnetic metal thin film. 5. The magnetic recording medium according to claim 1, wherein said protective film is made of carbon. 6. The magnetic recording medium according to claim 1, wherein said protective film is formed by a chemical vapor deposition method. 7. The magnetic recording medium according to claim 1, wherein the aromatic alcohol is a phenol and / or a naphthol. 8. A nonmagnetic support, a magnetic layer formed on the nonmagnetic support, and a protective film formed on the magnetic layer and having a surface top-coated with an aromatic alcohol, An ester compound of a perfluoropolyether having a carboxyl group at a terminal at the terminal represented by the following formula 3 and a long-chain alcohol and a lubricant containing a long-chain saturated fatty acid ester represented by the following formula 4 are retained in the outermost layer. A magnetic recording medium characterized by the above-mentioned. Embedded image Embedded image 9. The mixing ratio of the ester compound of a perfluoropolyether having a carboxyl group at the terminal to a long-chain alcohol and the long-chain saturated fatty acid ester is from 10:90 to 90:10 by weight. The magnetic recording medium according to claim 8, wherein: 10. The total number of carbon atoms of R ⁱ and R ^II of the long-chain saturated fatty acid ester represented by Chemical formula 4 is 15 to 3
9. The magnetic recording medium according to claim 8, wherein the number is 5. 11. The magnetic recording medium according to claim 8, wherein said magnetic layer is made of a ferromagnetic metal thin film. 12. The magnetic recording medium according to claim 8, wherein said protective film is made of carbon. 13. The magnetic recording medium according to claim 8, wherein said protective film is formed by a chemical vapor deposition method. 14. The magnetic recording medium according to claim 8, wherein the aromatic alcohol is a phenol and / or a naphthol.