JP2002269724A - Magnetic recording media - Google Patents

Abstract

(57) [Abstract] (Modified) [Problem] To achieve excellent running performance and durability by using a lubricant that has a long-lasting lubricating effect and improving the adhesion stability between the protective film and the lubricant. I do. SOLUTION: A non-magnetic support, a magnetic layer formed on the non-magnetic support, a protective film formed on the magnetic layer and having a surface treated in an inert gas plasma atmosphere. A lubricant containing an ester compound of a perfluoropolyether having a hydroxyl group at a terminal represented by the following formula 1 and a long-chain carboxylic acid and a long-chain saturated fatty acid represented by the following formula 2 is held in the outermost layer: Become.

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 commercial video format (D
VCAM) 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 a high-speed relative motion with a magnetic head in the process of recording / reproducing a magnetic signal, in which case 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.

In particular, Japanese Patent Application Laid-Open No. 05-93059 discloses a magnetic recording medium exhibiting a good lubricating effect under any use conditions by using an ester compound having a carboxyl group at a terminal as a lubricant. Have been. Japanese Patent Application Laid-Open No. 05-194970 discloses a magnetic recording medium exhibiting a good lubricating effect under any use conditions by using an ester compound having a hydroxyl group at a terminal as a lubricant.

[0009]

By the way, in the above-mentioned ferromagnetic metal thin film type magnetic recording medium, 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. And the tape for DVC which is the above-mentioned consumer video format,
Alternatively, as a magnetic recording medium of a ferromagnetic metal thin film type used for a DVCAM tape which is a business video format and an AIT tape which is a tape streamer application, a carbon protective film is formed on a ferromagnetic metal thin film. Magnetic recording media 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 future magnetic recording media of the ferromagnetic metal thin film type.

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 having a long-lasting lubricating effect and improves the adhesion stability between the protective film and the lubricant. It is an object of the present invention to provide a magnetic recording medium which realizes excellent running properties and durability.

[0014]

In order to achieve the above-mentioned object, a magnetic recording medium according to the present invention comprises a non-magnetic support,
A magnetic layer formed on the non-magnetic support; and a protective film formed on the magnetic layer and having its surface treated in an inert gas plasma atmosphere. And an ester compound of a perfluoropolyether having a hydroxyl group and a long-chain carboxylic acid and a lubricant containing a long-chain saturated fatty acid represented by the following formula (6) are retained in the outermost layer.

[0015]

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[0016]

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In the magnetic recording medium configured as described above, since the surface of the protective film is treated in an inert gas plasma atmosphere, the adhesion between the protective film and the lubricant is improved. Further, in the magnetic recording medium configured as described above, 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. In addition, good adhesion and lubricity are maintained, and good running properties and durability are ensured for a long period of time.

Further, 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 formed of an inert gas plasma. A protective film treated in an atmosphere, containing an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol represented by the following formula (7) and a long-chain saturated fatty acid represented by the following formula (8): Characterized by the fact that the lubricant that remains is retained in the outermost layer

[0019]

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[0020]

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In the magnetic recording medium configured as described above, since the surface of the protective film is treated in an inert gas plasma atmosphere, the adhesion between the protective film and the lubricant is improved. Further, in the magnetic recording medium configured as described above, 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. In addition, good adhesion and lubricity are maintained, and good running properties and durability are ensured for a long period of time.

[0022]

Embodiments of the present invention will be described below in detail.

<First Embodiment> FIG. 1 is a sectional view showing an example of a magnetic recording medium according to the present embodiment. As shown in FIG. 1, the magnetic recording medium 1 has a ferromagnetic metal thin film formed as a magnetic layer 3 on a nonmagnetic support 2 and a protective film 4 formed as an outermost layer on the magnetic layer 3. .

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 and 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 protrusion such as a mountain-like protrusion, a wrinkle-like protrusion, or a granular protrusion is formed on the surface to control the surface roughness.

More specifically, the mountain-like projections are formed by, for example, internally adding inorganic fine particles having a particle size of about 50 nm to 300 nm at the time of forming a polymer film, and having a height of 10 nm from the polymer film surface. 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-like 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 and 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
It is preferably 1 × 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
Resistance heating of the ferromagnetic metal material under a vacuum of × 10 ⁻⁶ Pa,
Evaporation is performed by high-frequency heating, electron beam heating, or the like to deposit an evaporated metal (ferromagnetic metal material) on the non-magnetic support 2. Generally, the above-described non-magnetic support 2 is used to obtain a high coercive force. Oblique deposition in which a ferromagnetic metal material is deposited obliquely 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.

The above sputtering method uses 1 × 10 ^-1 P
A glow discharge is caused in an atmosphere containing argon gas of a to 1 × 10 Pa as a main component, and the generated argon gas ions strike out atoms on the target surface.
Depending on the method of glow discharge, DC two-pole, three-pole sputtering,
There is a high frequency sputtering method, a magnetron sputtering method using magnetron discharge, or the like. 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. Further, 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,
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, 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.

This protective film 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 the wear of the ferromagnetic metal thin film is obtained.
It is preferably about 0 nm.

The protective film 4 is plasma-treated by exposing its surface to a plasma atmosphere of an inert gas. By performing the plasma treatment on the surface of the protective film 4, the adhesion between the protective film 4 and the lubricant held on the protective film 4 is improved, and the lubricating effect of the lubricant can be maintained for a long period of time. it can.

As a method of plasma-treating the surface of the protective film 4, for example, a magnetic recording medium on which the protective film 4 is formed is placed in a vacuum chamber, and evacuated by a rotary pump or the like until a predetermined degree of vacuum is reached. An inert gas is evenly supplied on the surface of the magnetic recording medium, and the degree of vacuum in the vacuum chamber is reduced to 15
The pressure is set to about 0 Pa. Thereafter, the treatment can be performed by applying a power of several tens of watts and applying a high frequency of, for example, about 13.56 MHz to generate plasma.

A point to be noted in this processing is to minimize the deterioration of the metal thin film type magnetic recording medium due to the plasma processing. From this point, an inert gas such as Ne, Ar, or Kr is used for plasma generation, but a nitrogen gas or the like that hardly causes a reaction accompanied by deterioration of the magnetic recording medium can be used.

Gas pressure of inert gas during this plasma processing
Is preferably 1 Pa to 3000 Pa, more preferably
Is 10 Pa to 300 Pa. At this time,
If the flow rate of the gas is such that it reaches the above gas pressure,
No problem, its value depends on the equipment used, but true
Vacancy volume is 20,000cm³In the case of about 50cm
³/ Min STP ~ 100cm³/ Min STP is preferred
No.

As the plasma generating source, those commonly used as plasma generating sources such as high-frequency discharge, microwave discharge, DC discharge, AC discharge, corona discharge and the like can be used. The degree of vacuum during plasma polymerization is 1 Pa to 300 P
a is preferred.

The electric power applied in the plasma treatment may be in a dischargeable region, but is preferably 20 watts to 150 watts, and more preferably 50 watts to 100 watts.

In particular, in the magnetic recording medium 1 to which the present invention is applied, the protective film 4 serving as the outermost layer is formed by forming an ester of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid represented by the following formula (9). Compound and
A lubricant containing a long-chain saturated fatty acid represented by the formula (1) is retained.

[0049]

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[0050]

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The compound represented by Chemical formula 9 and Chemical formula 1
The lubricant having the compound represented by 0 has properties such that the adhesion and 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 represented by the above-mentioned chemical formula 9 can be obtained, for example, by adding a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid chloride to toluene In a reaction using a base as a catalyst.

Here, 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 (provided that
P and q in the chemical formulas each represent an integer of 1 or more. ) 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 5,000.
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, A compound represented by No. 9.

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, and 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.

Further, as described above, the lubricant used in the present invention contains a long-chain saturated fatty acid represented by the above formula 10 in addition to the ester compound represented by the above formula 9.

[0059] Here, the long chain saturated fatty acid represented by the chemical formula 10, it is preferable number of carbon atoms of the formula in which ^{R 2} is 11 to 19. Specific examples include lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, and arachiic acid.

The carbon number of R ² in the long-chain saturated fatty acid represented by the above 10 is preferably 11 to 19.
When the carbon number of R ² is 10 or less, the lubricating effect is poor and there is no effect on the still durability. When the carbon number of R ² exceeds 19, the solubility in the organic solvent becomes small and the uniform lubricant coating layer is formed. May be difficult to form.

It is important that the fatty acids are selected from saturated fatty acids. By including a saturated fatty acid in the lubricant, excellent initial lubricating properties can be maintained even during long-term storage.

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 carboxylic acid as shown in Chemical formula 10. The mixing ratio with the saturated fatty acid is preferably 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 of retaining the lubricant in the outermost layer in the magnetic recording medium 1, a method of top-coating the lubricant on the surface of the protective film 4 can be mentioned. Here, the coating amount ^is preferably ^{0.05mg / m 2 ~100mg / m 2} , 0.1mg / m 2 ~50mg / m 2
Is more preferable. If the coating amount is too small, the effect of lowering the friction coefficient and improving the abrasion resistance and durability will not be exhibited. A cracking phenomenon occurs between the two, which results in poor running performance.

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.

In the magnetic recording medium 1, a protective film 4 made of carbon is formed as the outermost layer, and the surface thereof is plasma-treated.
Adhesion between the used lubricant and 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.

The magnetic recording medium 1 according to the present embodiment
In the above, if necessary, a rust preventive may be used in combination.
Any rust preventive can be used as long as it is generally used as a rust preventive for this type of magnetic recording medium. Examples thereof include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, oxygen atoms. And heterocyclic compounds containing a sulfur atom.

In the magnetic recording medium 1 of the present invention, a so-called back coat 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, the powder component has conductivity.
Control of carbon fine powder and surface roughness
And inorganic pigments added to improve durability
It is. As the carbon-based fine particles, for example, fur
Nes carbon, channel carbon, acetylene carb
, Thermal carbon, lamp carbon, etc.
As the inorganic pigment, α-FeOOH, α-Fe₂O
₃, Cr₂O₃, TiO ₂, ZnO, SiO, Si
O₂, SiO₂・ 2H₂O, Al₂O₃, CaCO₃,
MgCO₃, Sb₂O₃And the like.

Further, as the organic solvent of the back coat paint, for example, 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, plasma processing is performed on the surface of the protective film 4. Then, the above-mentioned lubricant is top-coated on the protective film 4 so that the protective film holds the lubricant, whereby 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 the vacuum deposition apparatus for forming the magnetic layer, there is a continuous winding type vacuum deposition apparatus as shown in FIG.

This vacuum evaporation apparatus is configured for so-called oblique evaporation, 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.

In this vacuum evaporation apparatus, the supply shaft 1 rotating in the counterclockwise direction in the drawing is placed in the vacuum chamber 11.
4 and a take-up shaft 15 rotating in the counterclockwise direction in the figure are also provided, and the non-magnetic support roll 16 attached to the supply shaft 14 is fed out in the direction shown by the arrow B in the figure. After running along the peripheral surface of the cooling can 12, the support 17 is wound around a magnetic tape roll 18 mounted on a winding shaft 15.

Note that guide rollers 19 and 20 are disposed between the supply shaft 14 and the cooling can 12 and between the cooling can 12 and the take-up shaft 15, respectively.
A predetermined tension is applied to the non-magnetic support 17 running along the cooling can 12 from the cooling can 12 and the winding shaft 15 from the cooling can 12 so that the non-magnetic support 17 runs smoothly.

The evaporation source 13 is a container such as a crucible containing a ferromagnetic metal material such as Co. In this vacuum evaporation apparatus, the evaporation source 13 is used to heat and evaporate the ferromagnetic metal material of the evaporation source 13. Is also provided. That is, the ferromagnetic metal material of the evaporation source 13 is acceleratedly irradiated with the electron beam 22 from the electron beam source 21 and heated and evaporated as shown by the arrow C in the figure. Then, the ferromagnetic metal material is deposited on the nonmagnetic support 17 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 17. It will be.

In the above-described vacuum vapor deposition apparatus, a deposition-preventing plate 23 is provided between the vapor deposition source 13 and the cooling can 12, and a shutter 24 is provided on the deposition-preventing plate 23 so as to be adjustable in position.
Only the vapor-deposited particles that enter the non-magnetic support 17 at a predetermined angle are passed. Thus, the ferromagnetic metal thin film is formed by the oblique deposition method.

Further, at the time of depositing such a ferromagnetic metal thin film, oxygen gas is supplied to the vicinity of the surface of the nonmagnetic support 17 through an oxygen gas inlet (not shown), whereby the magnetic properties of the ferromagnetic metal thin film are reduced. 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 has been described in which a ferromagnetic metal thin film made of Co is formed by an oblique deposition method.
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. Further, the thickness of the ferromagnetic metal thin film at this time 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. Further, 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 which is 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.

This protective film 4 has a thickness of about 3 nm to 15 nm, especially 5 nm to 5 nm, so as to reduce the spacing loss and to obtain the effect of preventing the wear of the ferromagnetic metal thin film.
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, a magnetron sputtering method, an ion beam sputtering method, an ion beam plating method, or the like. And the like.

Then, the surface of the protective film 4 is subjected to a plasma treatment by exposing it to a plasma atmosphere of an inert gas. By performing the plasma treatment on the surface of the protective film 4, the adhesion between the protective film 4 and the lubricant applied on the protective film 4 can be improved.

To perform a plasma treatment on the surface of the protective film 4,
For example, first, the magnetic recording medium on which the protective film 4 has been formed is put in a vacuum chamber, and exhausted by a rotary pump or the like until a predetermined degree of vacuum is reached. Thereafter, an inert gas is uniformly supplied onto the surface of the magnetic recording medium, the degree of vacuum in the vacuum chamber is reduced to about 150 Pa, and a power of several tens of watts is applied to generate a high frequency of 13.56 MHz. The addition generates plasma. Then, the surface of the protective film 4 is subjected to plasma processing by exposing the protective film 4 to the plasma atmosphere of the inert gas.

Here, points to be noted in this processing are as follows.
An object of the present invention is to minimize deterioration of a metal thin-film magnetic recording medium due to plasma processing. From this point, an inert gas such as Ne, Ar, or Kr is used for plasma generation, but a nitrogen gas or the like that hardly causes a reaction accompanied by deterioration of the magnetic recording medium can be used.

The gas pressure of the inert gas during the plasma processing
Is preferably 1 Pa to 3000 Pa, more preferably
Is 10 Pa to 300 Pa. At this time,
If the flow rate of the gas is such that it reaches the above gas pressure,
No problem, its value depends on the equipment used, but true
Vacancy volume is 20,000cm³In the case of about 50cm
³/ Min STP ~ 100cm³/ Min STP is preferred
No.

As the plasma generating source, those commonly used as plasma generating sources such as high frequency discharge, microwave discharge, DC discharge, AC discharge, corona discharge and the like can be used.

The electric power applied in the plasma treatment may be in the dischargeable region, but is preferably 20 watts to 150 watts, and more preferably 50 watts to 100 watts.

<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 represented by Chemical formula 12 is retained.

[0096]

Embedded image

[0097]

Embedded image

The lubricant having 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 maintain a lubricating effect for a long time. It has characteristics.

The magnetic recording medium using the lubricant represented by Chemical Formulas 11 and 12 has substantially the same configuration 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) can be obtained, for example, by mixing a perfluoropolyether having a carboxyl group at a terminal with a long-chain alcohol with anhydrous toluene. It is obtained by reacting p-toluenesulfonic acid, concentrated sulfuric acid, or the like as a catalyst therein.

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 -
COOH (wherein, m and j in the above chemical formulas each represent an integer of 1 or more) and the like. The above perfluoropolyether having a carboxyl group at the terminal is, of course,
However, it is 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 5,000. 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.

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

Here, the lubricant used in the magnetic recording medium of the present invention includes an ester compound of a perfluoropolyether having a carboxyl group at a terminal represented by the following formula (11) and a long-chain alcohol; The mixing ratio with the long-chain saturated fatty acid 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 keeping the lubricant in the outermost layer
However, in the case of the lubricant in the magnetic recording medium 1 described above,
Same as above, and top coat the lubricant on the surface of the protective film.
Method. Here, the coating amount is 0.05
mg / m²~ 100mg / m ²Is preferably
0.1mg / m²~ 50mg / m²It is better to be
Good. If the coating amount is too small, the friction coefficient
The effects of lowering and improving wear resistance and durability are not shown.
If the coating amount is too large, the sliding member and ferromagnetic metal
A cracking phenomenon occurs between the thin film and the running property.
It becomes.

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 formed as an outermost layer and the surface of the protective film is plasma-treated, the adhesion between the lubricant used and the protective film is improved. Good durability can be realized.

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

The present invention is not limited to the above description, and can be appropriately modified without departing from the gist of the present invention.

[0112]

EXAMPLES Examples of the present invention will be described below based on specific experimental results.

Next, in order to confirm the effects of the present invention, a magnetic recording medium was actually manufactured and its characteristics were evaluated.

Experimental Example 1 In this example, the effect 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 was as follows. I checked it.

(Preparation of Sample) Synthesis of ester compound of perfluoropolyether having a hydroxyl group at a terminal and long-chain carboxylic acid represented by Chemical formula 9 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 as much as the molar ratio of this perfluoropolyether, was dissolved in an organic solvent, and stearic acid chloride, which was twice as much as the molar ratio, was dropped into this solution over 30 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.

[0118]

[Table 1]

[0119] 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, a 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, the surface of the protective film was subjected to an argon gas pressure of 150 Pa, an applied voltage of 100 W and a frequency of 13.
It was exposed to high frequency plasma generated under the condition of 56 MHz for 10 seconds.

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 ,
Various types of magnetic recording media were obtained.

Then, these 21 types of magnetic recording media were cut to a width of 6.35 mm to obtain 21 types of sample tapes of Examples 1 to 8 and Comparative Examples 1 to 13.

However, for the sample tapes of Comparative Examples 3 to 10, the surface of the protective film was not exposed to high-frequency plasma. 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. Further, the fatty acids used in Comparative Examples 11 to 13 have a double bond in the alkyl group.

[0126]

[Table 2]

[0127] 3. Evaluation of Characteristics Next, the above Examples 1 to 8 and Comparative Examples 1 to 13
The characteristics of the 21 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 Friction Coefficient The friction coefficient was measured by setting the environmental conditions in a thermostat 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:
DVC-VX1000) to measure the time required for the reproduction output of each sample tape to drop by 3 dB.

(3) Method of Measuring Shuttle Durability Shuttle durability is measured 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 (manufactured by Sony Corporation, model name: DVC) is controlled in this constant temperature bath.
-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 application of the lubricant 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.

[0132]

[Table 3]

[0133]

[Table 4]

From the results shown in Tables 3 and 4, the surface of the protective film formed by the CVD method was treated in an inert gas plasma atmosphere, and a perfluoropolyether having a hydroxyl group at a terminal was used as a lubricant. In Examples 1 to 8 using a lubricant in which an ester compound with a carboxylic acid and a long-chain saturated fatty acid were combined, the friction coefficient under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature, It was found that deterioration of still durability and shuttle durability was extremely small, 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 no plasma treatment was performed on the surface of the protective film
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 by a magnetron sputtering method, which is a PVD method, instead of the CVD method, sufficient durability cannot be obtained. Furthermore, from the results of comparison between Example 1 and Comparative Examples 11 to 13, it was found that the use of long-chain saturated fatty acids having no unsaturated bond enables the initial properties to be maintained even after long-term storage. .

From the above results, the surface of the protective film formed by the CVD method was treated in a plasma atmosphere of an inert gas, and as a lubricant, a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid were used. By combining an ester compound and a long-chain saturated fatty acid, the lubricant maintains good adhesion and lubricity under any use conditions and maintains a lubricating effect for a long period of time. And durability was obtained.

EXPERIMENTAL EXAMPLE 2 In this experimental example, an ester compound of a perfluoropolyether having a carboxyl group at a terminal at the terminal represented by Chemical formula 11 and a long-chain alcohol and a lubricant containing a long-chain saturated fatty acid were used. Was confirmed as follows.

(Preparation of Sample) Synthesis of ester compound of perfluoropolyether having a terminal carboxyl group and long-chain alcohol First, as a perfluoropolyether having a terminal carboxyl group, HOOCCF ₂ (O
C ₂ F ₄ ) _m (OCF ₂ ) _j OCF ₂ COOH (provided that
M and j in the chemical formula each represent an integer of 1 or more. ), Stearyl alcohol having a molar ratio twice as much as that of the perfluoropolyether 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 by the same synthesis method as that of the above-mentioned compound 6. Synthesized. In Table 5, j, k, and m each represent an integer of 1 or more.

[0141]

[Table 5]

[0142] 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 treated with an inert gas plasma.

Next, in the same manner as in the above-mentioned Experimental Example 1, a solution in which a lubricant as 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 21 types of magnetic recording media.

Then, these 21 types of magnetic recording media were cut into 6.35 mm widths respectively.
6 and 21 types of sample tapes of Comparative Examples 14 to 26 were produced.

However, with respect to the sample tapes of Comparative Examples 16 to 23, the surface of the protective film was not exposed to high-frequency plasma. Further, with respect to the sample tapes of Comparative Examples 21 to 23, the protective film was formed by the magnetron sputtering method instead of the plasma CVD method as described above. Further, the fatty acids used in Comparative Examples 24 to 26 have a double bond in the alkyl group.

[0146]

[Table 6]

[0147] 3. Evaluation of Characteristics Next, the characteristics of the 21 types of sample tapes of Examples 9 to 16 and Comparative Examples 14 to 26 were evaluated. Here, the durability and the running property were evaluated. Specifically, the friction coefficient, still durability, and shuttle durability were evaluated in the same manner as in Experimental Example 1 described above.

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.

[0149]

[Table 7]

[0150]

[Table 8]

From the results shown in Tables 7 and 8, the surface of the protective film formed by the CVD method was treated in a plasma atmosphere of an inert gas, and a perfluoropolyether having a terminal carboxyl group was used as a lubricant. In Examples 9 to 16 using a lubricant in which an ester compound with a long-chain alcohol and a long-chain saturated fatty acid were combined, the coefficient of friction under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature, It was found that deterioration of still durability and shuttle durability was extremely small, and very good results were obtained.

On the other hand, in Comparative Examples 14 and 15 using a lubricant containing only an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol, the friction coefficient and the friction coefficient were changed under various use conditions. The deterioration of still durability and shuttle durability was very large.
Further, in Comparative Examples 16 to 23 in which the plasma treatment was not performed on the surface of the protective film, the friction coefficient, still durability, and shuttle durability were greatly deteriorated under various use conditions, and good results were obtained. I couldn't. Further, when the protective film is formed by a magnetron sputtering method, which is a PVD method, instead of the CVD method, sufficient durability cannot be obtained. Further, Example 9 and Comparative Examples 24 to 26
From the results of comparison with the above, it was found that the use of a long-chain saturated fatty acid having no unsaturated bond enables the initial properties to be maintained after long-term storage.

From the above results, the surface of the protective film formed by the CVD method was treated in a plasma atmosphere of an inert gas. Further, as a lubricant, a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol were used. By combining an ester compound and a long-chain saturated fatty acid, the lubricant maintains good adhesion and lubricity under any use conditions and maintains a lubricating effect for a long period of time. And durability was obtained.

[0154]

As described above, 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 as described above. , Running performance and durability can be improved.

Further, the magnetic recording medium according to the present invention is formed as the outermost layer, and the surface of the protective film made of carbon is plasma-treated, so that the lubricant held on the protective film, the protective film, Can be improved, and more excellent durability can be realized.

Further, in the magnetic recording medium according to the present invention, since the magnetic layer is made of a ferromagnetic metal thin film, it can sufficiently cope with high-density recording and long-time recording.

[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

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 CH051 EF056 GS01 4J005 BD02 BD04 5D006 AA01 AA06 BB01 EA03 FA02 FA05

Claims (12)

[Claims] 1. A non-magnetic support, a magnetic layer formed on the non-magnetic support, and a protective film formed on the magnetic layer, the surface of which is treated in a plasma atmosphere of an inert gas. A lubricant containing an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid represented by the following formula 1 and a long-chain saturated fatty acid represented by the following formula 2 is retained in the outermost layer. A magnetic recording medium comprising: 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 is 10:90 by weight.
2. The magnetic recording medium according to claim 1, wherein the ratio is up to 90:10. 3. The magnetic recording medium according to claim 1, wherein R ² in Chemical Formula ² has 11 to 19 carbon atoms. 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. A non-magnetic support, a magnetic layer formed on the non-magnetic support, and a protective film formed on the magnetic layer, the surface of which is treated in a plasma atmosphere of an inert gas. And a lubricant containing an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol represented by the following formula (3) and a long-chain saturated fatty acid represented by the following formula (4) is retained in the outermost layer: A magnetic recording medium comprising: Embedded image Embedded image 8. The mixing ratio of the ester compound of a perfluoropolyether having a carboxyl group at a terminal to a long-chain alcohol and the long-chain saturated fatty acid is 1 by weight.
8. The ratio is 0:90 to 90:10.
The magnetic recording medium according to the above. 9. The magnetic recording medium according to claim 7, wherein R ² in Chemical Formula 4 has 11 to 19 carbon atoms. 10. The magnetic recording medium according to claim 7, wherein said magnetic layer is made of a ferromagnetic metal thin film. 11. The magnetic recording medium according to claim 7, wherein said protective film is made of carbon. 12. The magnetic recording medium according to claim 7, wherein said protective film is formed by a chemical vapor deposition method.