JP2001236628A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure superior running performance and durability by using a lubricant which sustains its lubricating effect over a long period of time and enhancing the stability of adhesion of the lubricant to a protective film. SOLUTION: The magnetic recording medium has a nonmagnetic substrate 2, a magnetic layer 3 formed on one principal force of the substrate 2, a protective film 4 formed on the magnetic layer 3 and a back coat layer 5 formed on the other principal face of the substrate 2. A 1st lubricative layer with an aromatic alcohol and an ester compound of a perfluoro-polyether having hydroxyl groups at the ends and a long chain carboxylic acid has been held on the protective film 4 and a 2nd lubricative layer with an ester compound of a perfluoro-polyether having hydroxyl groups at the ends and a long chain carboxylic acid has been held on the back coat layer 5.

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. . Further, it is better that the wear and damage due to the 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 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 an attempt is made to use a lubricant to improve the durability and running properties of the magnetic recording medium, the adsorptivity 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.

In view of such a situation, the present inventors formed a lubricant layer having an aromatic alcohol and a specific organic fluorine compound as a lubricant on a carbon protective film, thereby forming a lubricant and a carbon protective film. And Japanese Patent Application No. 11-33674.
No. 0 proposes.

However, such a magnetic recording medium is wound in a roll when stored in a cassette, and the carbon protective film is in contact with the back coat layer. Therefore, there is a problem that the lubricant on the carbon protective film moves to the back coat layer side by the transfer and the amount of the lubricant on the carbon protective film becomes smaller than a desired amount, so that the lubricating effect is reduced. .

Therefore, 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. Accordingly, it is an object of the present invention to provide a magnetic recording medium that achieves excellent running properties and durability and a method for manufacturing a magnetic recording medium that excels in productivity.

[0016]

A magnetic recording medium according to the present invention comprises a non-magnetic support, a magnetic layer formed on one main surface of the non-magnetic support, and a protective film formed on the magnetic layer. And a back coat layer formed on the other main surface of the non-magnetic support, wherein the protective film has, on the protective film, an aromatic alcohol and a perfluoro group having a hydroxyl group at a terminal represented by the following formula (3). A first lubricating layer having a polyether and an ester compound of a long-chain carboxylic acid is formed, and a perfluoropolyether having a hydroxyl group at a terminal represented by the following formula 3 and a long-chain carboxylic acid are formed on the back coat layer. A second lubricating layer having an ester compound is formed.

[0017]

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In the magnetic recording medium according to the present invention as described above, since the first lubricating layer contains an aromatic alcohol, the adhesion between the protective film and the compound represented by Chemical Formula 3 is reinforced by the aromatic alcohol. You. Thereby, in the magnetic recording medium, the adhesion between the protective film and the first lubricating layer is improved. Further, in the magnetic recording medium according to the present invention, the lubricant containing the compound represented by Chemical Formula 3 is held in the outermost layer, so that the adhesion and the lubricity are suitably maintained under any use conditions. . Further, in the magnetic recording medium according to the present invention, since the second lubricating layer is also provided on the back coat layer, even when the magnetic recording medium is wound, the lubricant on the protective film is applied to the back coat layer. This prevents the amount of the lubricant on the protective film from being reduced by moving to the side, thereby ensuring good running properties and durability over a long period of time.

The magnetic recording medium according to the present invention comprises a non-magnetic support, a magnetic layer formed on one main surface of the non-magnetic support,
In a magnetic recording medium comprising a protective film formed on a magnetic layer and a back coat layer formed on the other main surface of the non-magnetic support, an aromatic alcohol is formed on the protective film and A first lubricating layer having a perfluoropolyether having a carboxyl group at a terminal shown therein and an ester compound of a long-chain alcohol is formed, and a carboxyl group having a terminal represented by the following formula 4 is formed on the back coat layer. A second lubricating layer having an ester compound of a perfluoropolyether and a long-chain alcohol is formed.

[0020]

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In the magnetic recording medium according to the present invention as described above, since the first lubricating layer contains an aromatic alcohol, the adhesion between the protective film and the compound represented by Chemical Formula 4 is reinforced by the aromatic alcohol. You. Thereby, in the magnetic recording medium, the adhesion between the protective film and the first lubricating layer is improved. Further, in the magnetic recording medium according to the present invention, since the lubricant containing the compound represented by Chemical Formula 4 is held in the outermost layer, the adhesion and the lubricity are suitably maintained under any use conditions. . Further, in the magnetic recording medium according to the present invention, since the second lubricating layer is also provided on the back coat layer, even when the magnetic recording medium is wound, the lubricant on the protective film is applied to the back coat layer. This prevents the amount of the lubricant on the protective film from being reduced by moving to the side, thereby ensuring good running properties and durability 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 the magnetic recording medium 1, as shown in FIG. 1, a ferromagnetic metal thin film is formed as a magnetic layer 3 on one main surface of a non-magnetic support 2, and a protective layer is formed on the magnetic layer 3 as an outermost layer. A film 4 is formed, and a back coat layer 5 is formed on the other main surface of the nonmagnetic support 2.

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, which has a soluble solvent is suitable. Then, in a solution obtained by dissolving these resins in a good solvent at a resin concentration of 1 ppm to 1000 ppm, a solvent which is a poor solvent for the resin and has a boiling point higher than that of the good solvent is 10 times the amount of the resin.
A thin film having very fine wrinkle-like projections can be formed by applying and drying the solution added in a 100-fold amount on the surface of the polymer film.

The granular protrusions 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 /
mm ^{2 to} 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 of Cr, W, V or the like 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 P
While maintaining the pressure at about a, a discharge is generated in the vacuum vessel to generate a plasma of a hydrocarbon gas, 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.

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.

On the surface of the protective film 4, a first lubricating layer (an ester compound of an aromatic alcohol and a perfluoropolyether having a hydroxyl group at a terminal represented by Chemical formula 5) and a long-chain carboxylic acid is used. (Not shown)).

[0044]

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The first lubricating layer is formed by applying a mixed solution obtained by mixing an aromatic alcohol and the compound shown in Chemical formula 5 to the protective film 4.
It may be formed by applying the solution on the top, or may be formed by applying a solution containing the aromatic alcohol and a solution containing the compound shown in Chemical formula 5 in this order. That is,
The first lubricating layer is formed by applying a mixed solution obtained by mixing an aromatic alcohol and a compound represented by Chemical formula 5 onto the protective film 4 (hereinafter, referred to as a “simultaneous application method”) or an aromatic alcohol. A solution having the compound shown in Chemical Formula 5 is applied on the top coat layer (hereinafter, referred to as a “sequential application method”) to form a top coat layer.

The aromatic alcohol can modify the surface of the protective film 4 and increase the adsorbing power of the compound represented by Chemical Formula 5. Specifically, the π electrons in the molecule of the aromatic alcohol and the π electrons in the protective film 4 attract each other, so that the aromatic alcohol is adsorbed on the surface of the protective film 4 and the hydroxyl groups of the aromatic alcohol are converted into And an adsorption site for the compound represented by Thereby, the adsorptive power of the compound represented by Chemical formula 5 is increased.

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.

The ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid shown in the above formula 5 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.

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 ( 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 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 above-mentioned 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, 5 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, 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, in this magnetic recording medium, the amount of the aromatic alcohol is specified to be equal to or more than the amount of the compound represented by Chemical Formula 5. If the amount of the aromatic alcohol is less than the amount of the compound represented by Chemical formula 5, the lubricating effect cannot be maintained for a long time. Accordingly, in the magnetic recording medium, since the amount of the aromatic alcohol is specified to be equal to or more than the amount of the compound represented by Chemical formula 5, the adhesion and lubricity are suitably maintained under any use conditions, and For a long time.

When the first lubricating layer is formed by the sequential coating method, the amount of the aromatic alcohol applied is preferably determined depending on the degree of oxidation on the surface of the protective film 4. The specific application amount is 0.05 mg / m ² to
It is preferably 100 mg / m ² , and more preferably 0.1 mg / m ² .
And more preferably ^{1mg / m 2 ~50mg / m 2} . When the first lubricating layer is formed by a sequential coating method,
The amount of the compound represented by Chemical formula 5 is 0.05 mg / m ²
１００100 mg / m ² , preferably 0.1 mg / m ²
m ² and more preferably to 50 mg / m ^2. If the coating amount is too small, the effect of lowering the friction coefficient and improving the abrasion resistance and the durability will not be exhibited, and if the coating amount is too large, the sliding member and the ferromagnetic metal thin film will not be effectively mixed. A cracking phenomenon occurs between the two, which results in poor running performance.

On the other hand, when the first lubricating layer is formed by the simultaneous coating method, the aromatic alcohol and the compound represented by Chemical formula 5 may be formed into a paint by using different solvents, respectively. It may be made into paint. Further, the total coating amount of aromatic alcohol and of 5 the compound represented by the in the range of 0.05mg / m ² ~100mg / m ² are ^{preferred, 0.1mg / m 2 ~50mg / m} 2 Is more preferred. If the coating amount is too small, the effect of lowering the friction coefficient and improving the abrasion resistance and the durability will not be exhibited, and if the coating amount is too large, the sliding member and the ferromagnetic metal thin film will not be effectively mixed. A cracking phenomenon occurs between the two, which results in poor running performance.

The back coat layer 5 is formed on the main surface of the nonmagnetic support 1 opposite to the surface on which the metal magnetic film 2 is formed. The back coat layer 5 is formed mainly by applying a back coat paint in which an inorganic powder component and a binder resin are mixed and dispersed in an organic solvent to a non-magnetic support.

The back coat layer 5 preferably contains carbon black. Further, it is preferable that calcium carbonate and an inorganic powder having a Mohs hardness of 5 to 9 are contained as the inorganic powder.

In the back coat layer 5, it is preferable to use two types of carbon black having different average particle sizes. In this case, the average particle size is 10
It is preferable to use fine-grained carbon black having a particle size of 20 to 20 nm and coarse-grained carbon black having an average particle size of 230 to 300 nm.

In general, the surface electric resistance of the back coat layer 5 can be set low and the light transmittance can be set low by adding the above-mentioned fine particle carbon black.
Some magnetic recording devices use the light transmittance of the tape and use it as an operation signal. In such a case, the addition of fine carbon black is particularly effective.

In addition, since fine carbon black particles generally have excellent holding power to a lubricant, a lubricant can be used in combination, and as a result, the coefficient of friction can be reduced.

On the other hand, coarse carbon black having a particle size of 230 to 300 nm has a function as a solid lubricant and forms fine projections on the surface. It is possible to reduce the coefficient of friction. However, coarse carbon black
In a severe running system, the tape may slide off from the back coat layer 5 easily, which may lead to an increase in the error ratio.

Specifically, the following can be cited as examples of the particulate carbon black. RAVEN2
000B (18 nm), RAVEN 1500B (17n
m) (above, manufactured by Columbia Carbon Co., Ltd.), BP800
(17 nm) (Cabot), PRINTEX90
(14 nm), PRINTEX95 (15 nm), PR
INTEX85 (16 nm), PRINTEX75 (1
7 nm) (all manufactured by Degussa), # 3950 (16 n
m) (Mitsubishi Chemical Industries, Ltd.). Thermal black (270 nm) is used as coarse carbon black.
(Manufactured by Khancarb), RAVEN MTP (275n
m) (manufactured by Columbia Carbon Co., Ltd.).

In the case of using two types having different average particle sizes in the back coat layer 5, 10 to 20 n
m of the fine carbon black and the coarse carbon black of 230 to 300 nm (weight ratio) is as follows: fine carbon black: coarse carbon black =
The ratio is preferably from 98: 2 to 75:25, and more preferably from 95: 5 to 85:15. Further, the content of carbon black (in the case of adding fine particles and coarse particles, the total amount thereof) in the back coat layer 5 is usually in the range of 30 to 80 parts by weight with respect to 100 parts by weight of a binder described later. And preferably in the range of 45 to 65 parts by weight.

On the other hand, inorganic powders having a Mohs hardness of 5
The use of one of Nos. 1 to 9 makes it possible to provide the magnetic recording medium with repeated running durability and to strengthen the back coat layer 5. When these inorganic powders are used together with the above-described carbon black and calcium carbonate, the back coat layer 5 becomes less strong against repeated sliding and becomes a strong back coat layer 5 due to its filler effect.

When the inorganic powder used in the back coat layer 5 has a relatively high Mohs hardness of 5 to 9, an appropriate polishing force is generated on the surface of the back coat layer 5 and the surface of the back coat layer 5 adheres to guide poles and the like. Is reduced. As a magnetic recording medium, when calcium carbonate and an inorganic powder are used in combination for the back coat layer 5, the sliding characteristics against a guide pole having a rough surface are improved, and the friction coefficient of the back coat layer 5 is stabilized. Can also be achieved. The inorganic powder preferably has an average particle size of 80 to 250 nm, more preferably 100 to 210 n.
m.

Examples of the inorganic powder include α-iron oxide, α-alumina, and chromium oxide (Cr ₂ O ₃ ). These inorganic powders may be used alone or in combination. Among these, α-iron oxide or α-alumina is preferred. The content of the inorganic powder having a Mohs hardness of 5 to 9 is usually 3 to 30 parts by weight with respect to 100 parts by weight of carbon black,
Preferably, it is 3 to 20 parts by weight. In particular, it is preferable that the back coat layer 5 contains two types of carbon black having different average particle sizes, calcium carbonate having the above particle size, and the inorganic powder having the specific Mohs hardness.

The binder resin used for the back coat layer 5 includes, for example, a thermoplastic resin, a thermosetting resin, a reactive resin, and a mixture thereof.

Examples of the thermoplastic resin include vinyl chloride,
Polymer containing vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, and vinyl ether as constituent units Or a copolymer. Examples of the copolymer include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, and acrylate-vinylidene chloride copolymer. Polymer, acrylate-styrene copolymer, methacrylate-acrylonitrile copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-styrene copolymer, vinylidene chloride-acrylonitrile copolymer , Butadiene-
An acrylonitrile copolymer, a styrene-butadiene copolymer, and a chlorovinyl ether-acrylate copolymer can be exemplified. In addition to the above, polyamide resins, cellulose resins (cellulose acetate butyrate,
Cellulose diacetate, cellulose propionate, nitrocellulose, etc.), polyvinyl fluoride, polyester resin, polyurethane resin, various rubber resins and the like can also be exemplified.

Examples of the thermosetting resin or the reactive resin include phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acryl-based reactive resin, formaldehyde resin, silicon resin, epoxy resin -Polyamide resins, mixtures of polyester resins and polyisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, mixtures of polyurethane and polyisocyanates.

Further, examples of the organic solvent for the backcoat 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, on the surface of the back coat layer 5,
A second lubricating layer (not shown) having a perfluoropolyether having a hydroxyl group at a terminal and an ester compound of a long-chain carboxylic acid represented by Chemical Formula 5 is formed. Then, the second lubricating layer formed on the surface of the back coat layer contains the compound represented by Chemical Formula 5 described above.

In this magnetic recording medium, for example, when it is wound on a roll, the first lubricating layer and the second lubricating layer come into contact with each other. At this time, the compound represented by Chemical Formula 5 contained in the second lubricating layer migrates to the first lubricating layer. As a result, the amount of the compound represented by Chemical Formula 5 in the first lubricating layer becomes constant.

Therefore, in this magnetic recording medium, the amount of the compound represented by Chemical Formula 5 contained in the second lubricating layer is as follows:
It is preferable that the amount of the compound represented by Chemical Formula 5 contained in the first lubricating layer is twice or more. If the amount of the compound represented by Chemical Formula 5 contained in the second lubricating layer is less than twice the amount of the compound represented by Chemical Formula 5 contained in the first lubricating layer, the protective film 4 In some cases, it may be difficult to maintain an appropriate amount of the lubricant, and the lubricating effect may not be maintained for a long period of time. Therefore, in the magnetic recording medium, the amount of the compound represented by Chemical Formula 5 contained in the second lubricating layer is at least twice the amount of the compound represented by Chemical Formula 5 contained in the first lubricating layer. The lubricating property can be suitably maintained under any use conditions, and the lubricating effect can be maintained for a long period of time.

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

In the magnetic recording medium 1, the protective film 4 made of carbon is formed as the outermost layer, and the first lubricating layer contains an aromatic alcohol. Adhesion with the film 4 is improved, and good durability can be realized.

Further, in this magnetic recording medium 1,
Since the second lubricating layer is also provided on the back coat layer 5, the amount of the lubricant on the protective film 4 can be maintained at a desired amount, and good durability can be realized for a long time. .

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 as described above is manufactured as follows.

First, a ferromagnetic metal thin film serving as the magnetic layer 3 is formed on one main surface of the nonmagnetic support 2 by, for example, a vacuum evaporation method. After that, for example, the plasma C
The protection film 4 is formed by the VD method. Then, the back coat layer 5 is formed on the other main surface of the non-magnetic support 2 by coating. Then, a top coat with an aromatic alcohol is performed on the surface of the protective film 4. Then, the above-described lubricant is applied on the protective film 4 to hold the lubricant on the protective film. Further, a lubricant is applied on the surface of the back coat layer 5 and held, whereby the magnetic recording medium 1 is obtained.

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.

In this vacuum evaporation apparatus, a supply roll 14 rotating in the counterclockwise direction in the figure and a winding roll 15 rotating in the counterclockwise direction in the figure are also provided 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.

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 in which a ferromagnetic metal material such as Co is stored. In this vacuum evaporation system, 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-described 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, 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 16 through an oxygen gas inlet (not shown). 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 the 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 10 Pa.
While maintaining the pressure at about 0 Pa, discharge is performed 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 which is a 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 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, other than this method, a magnetron sputtering method, an ion beam sputtering method, an ion beam plating method may be used. And the like.

The back coat layer 5 is formed by preparing a back coat paint by mixing and dispersing a binder resin and a powder component in an organic solvent, and applying the back coat paint.

The coating for the back coat can be produced by using a kneader or a dilution disperser. Conventionally known mixers and dilution / dispersion machines can be used. Specifically, examples of the kneader include a continuous twin-screw kneader (extruder), a co-kneader, and a pressure kneader. Examples of the dilution / dispersion machine include a vertical sand mill, a horizontal sand mill, a spike mill, a pearl mill, and a double cylinder pearl mill.

For applying the coating for the back coat, conventionally known methods can be used. For example, a reverse roll, a gravure roll, an air doctor coater, a blade coater, an air knife coater, a squeeze coater, an impregnated coater, a transfer roll The coating can be performed using a coater, kiss coater, cast coater, spray coater, or the like.

After the formation of the back coat layer 5, a first lubricating layer and a second lubricating layer are formed.

In particular, when the first lubricating layer is formed by using the simultaneous coating method, the first lubricating layer can be formed by one coating step. Can be shortened. Therefore, according to the simultaneous coating method, a magnetic recording medium with good productivity can be manufactured.

<Second Embodiment> Next, a second embodiment of the present invention will be described.
An embodiment will be described. The magnetic recording medium according to the present embodiment has a ferromagnetic metal thin film as a magnetic layer on one main surface of a non-magnetic support, like the magnetic recording medium 1 according to the first embodiment shown in FIG. A protective film is sequentially formed as an outermost layer, and a back coat layer is formed on the other main surface of the nonmagnetic support. The magnetic recording medium according to the present embodiment has, in particular, an aromatic alcohol and a perfluoropolyether having a carboxyl group at a terminal represented by the following formula (6) and a long-chain alcohol on the surface of the protective film serving as the outermost layer. A first lubricating layer having a lubricant containing an ester compound is formed, and an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol represented by the following formula 6 is formed on the surface of the back coat layer. Having a second
Is formed.

[0105]

Embedded image

The lubricant having the compound represented by Chemical Formula 6 has characteristics that the adhesion and the lubricity are suitably maintained under any use conditions and the lubricating effect is maintained for a long period of time. .

The magnetic recording medium using the lubricant represented by Chemical Formula 6 has substantially the same structure as the magnetic recording medium 1 shown in FIG. This is an example in which only the agent and the lubricant held on the back coat layer are 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 terminal carboxyl group and a long-chain alcohol represented by the above formula 6 can be obtained, for example, by mixing a perfluoropolyether having a terminal carboxyl group with a long-chain alcohol in anhydrous toluene. And by reacting with p-toluenesulfonic acid or concentrated sulfuric acid as a catalyst.

The perfluoropolyether having a carboxyl group at the terminal is preferably one 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 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.

The method for holding the lubricant in the outermost layer as the first lubricating layer is the same as that for the lubricant in the magnetic recording medium 1 described above, and the simultaneous coating method or the sequential coating method is used. Can be. In particular, if a simultaneous coating method is used when forming the first lubricating layer, the first lubricating layer can be formed by one coating step.
The manufacturing process can be shortened as compared with the sequential coating method. Therefore, according to the simultaneous coating method, a magnetic recording medium with good productivity can be manufactured.

Here, the total coating amount of the aromatic alcohol and the compound represented by Chemical formula 6 is 0.05 mg / m ² to 1
Is preferably from ^{00mg / m 2, 0.1mg / m} 2 ~
More preferably, it is 50 mg / m ² . If the coating amount is too small, the effect of lowering the friction coefficient and improving wear resistance and durability will not be exhibited, and if the coating amount is too large, the distance between the sliding member and the ferromagnetic metal thin film will not be increased. In this case, a shearing phenomenon occurs, and on the contrary, the traveling performance deteriorates.

On the other hand, when a sequential coating method is used to form the first lubricating layer, the amount of the aromatic alcohol to be applied is preferably determined depending on the degree of oxidation on the surface of the protective film 4. . Specific application amount is preferably from ^{0.05mg / m 2 ~100mg / m 2} , further more preferably ^{0.1mg / m 2 ~50mg / m 2} . In the case of forming the first lubricant layer with sequential coating method, the coating amount of the compound represented by Formula 6 is preferably from ^{0.05mg / m 2 ~100mg / m 2} , 0.1mg / m 2 More preferably, it is ５０50 mg / m ² . If the coating amount is too small, the effect of lowering the friction coefficient and improving the abrasion resistance and the durability will not be exhibited, and if the coating amount is too large, the sliding member and the ferromagnetic metal thin film will not be effectively mixed. A cracking phenomenon occurs between the two, which results in poor running performance.

Further, this magnetic recording medium is, for example, wound in a roll in the same manner as in the first embodiment.
The first lubricating layer and the second lubricating layer come into contact with each other. At this time, the compound represented by Chemical Formula 6 contained in the second lubricating layer migrates to the first lubricating layer. As a result, the amount of the compound represented by Chemical Formula 6 in the first lubricating layer becomes constant.

Therefore, also in this magnetic recording medium, the chemical compound contained in the second lubricating layer is used as in the first embodiment.
Is preferably at least twice the amount of the compound represented by Chemical Formula 6 contained in the first lubricating layer. When the amount of the compound represented by Chemical Formula 6 contained in the second lubricating layer is less than twice the amount of the compound represented by Chemical Formula 6 contained in the first lubricating layer, the protective film 4 In some cases, it may be difficult to maintain an appropriate amount of the lubricant, and the lubricating effect may not be maintained for a long period of time. Therefore, in the magnetic recording medium, the amount of the compound represented by Chemical Formula 6 contained in the second lubricating layer is set to be at least twice the amount of the compound represented by Chemical Formula 6 contained in the first lubricating layer. The lubricating property can be suitably maintained under any use conditions, and the lubricating effect can be maintained for a long period of time.

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

Further, in this magnetic recording medium, the surface of the protective film formed as the outermost layer and made of carbon is
Since the first lubricating layer having the aromatic alcohol and the compound represented by the chemical formula (6) is formed, the adhesion between the compound represented by the chemical formula (6) and the protective film is improved, and further excellent durability is realized. Can be.

Further, in the magnetic recording medium 1,
Since the lubricant layer is also formed on the back coat layer, the amount of the lubricant on the protective film can be maintained at a desired amount, and further excellent durability can be realized for a long period.

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.

[0122]

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 in order to examine a preferable amount of a lubricant applied to the back coat layer, and its characteristics were evaluated.

Experimental Example 1 In this experimental example, the effect of using a lubricant containing an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid was confirmed as follows. In Experimental Example 1, the first coating was performed using the sequential coating method.
This is an example in which a lubricating layer is formed.

(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 (wherein p and q each represent an integer of 1 or more), and triethylamine having a molar equivalent of 2 times the molar ratio of this perfluoropolyether is used. The resultant was dissolved in an organic solvent, and a twice-equivalent amount of stearic acid chloride in a molar ratio was further added dropwise to the solution over 30 minutes.

After completion of the dropwise addition, the mixture was stirred for 1 hour, and then heated and refluxed 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 terminal hydroxyl group 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.

[0127]

[Table 1]

[0128] 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 was 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 in isopropyl alcohol was applied to the surface of the carbon protective film so that the application amount was 10 mg / m ² .

Next, a solution of each of the lubricants shown in Table 2 below in a hexane solvent was applied to the surface of the carbon protective film so that the coating amount was 5 mg / m ^2, and the first
Was formed.

Further, a solution of each of the lubricants shown in Table 2 below in a hexane solvent was applied to the surface of the back coat layer in an amount of 5 mg / m ² and 10 mg / m ² respectively.
A ^second lubricating layer was formed by coating so as to have an m ² of 15 mg / m ² to obtain 15 types of magnetic recording media.

Then, each of these 15 types of magnetic recording media was cut into a 6.35 mm width to obtain 15 types of sample tapes of Examples 1 to 15.

[0135]

[Table 2]

[0136] 3. Evaluation of Characteristics Next, the characteristics of the 15 types of sample tapes of Examples 1 to 15 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 by setting the environmental conditions in a thermostat at a temperature of 40 ° C.
The humidity was controlled by controlling the humidity to 80% RH, and the measurement was carried out by running each sample tape in this constant temperature bath for 1000 passes. In addition, the numerical value of the 1000th 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 was 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 (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 application of the lubricant and at a temperature of 45 ° C. and a humidity of 80% R
The test was performed after storage for 90 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 90 days.

[0141]

[Table 3]

[0142]

[Table 4]

From the results shown in Tables 3 and 4, all of the sample tapes of Examples 1 to 15 were top-coated with an aromatic alcohol on the surface of the protective film formed by the CVD method.
Further, as a lubricant, a lubricant containing an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid is used, and the amount of the aromatic alcohol is set to the amount of the lubricant or more, and the surface of the back coat layer is formed. Because a lubricant containing an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid has been applied,
In each 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.

The sample tape was heated at a temperature of 45 ° C.
After storage for 90 days in an environment of a humidity of 80% RH, the amount of the ester compound of the perfluoropolyether having a terminal hydroxyl group and the long-chain carboxylic acid contained in the second lubricating layer is reduced to the first amount. Example 2, Example 3, Example 5, Example 6, Example in which the amount of the ester compound of the perfluoropolyether having a terminal hydroxyl group and the long-chain carboxylic acid contained in the lubricating layer is twice or more. 8, in Example 9, Example 11, Example 12, Example 14 and Example 15, the friction coefficient, still durability and shuttle durability 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 the properties was extremely small and very good results were obtained.

On the other hand, the amount of the ester compound of the perfluoropolyether having a hydroxyl group at the terminal contained in the second lubricating layer and the long-chain carboxylic acid is determined by the amount of the hydroxyl group at the terminal contained in the first lubricating layer. In Example 1, Example 4, Example 7, Example 10, and Example 13 in which the amount was the same as the amount of the ester compound of the perfluoropolyether and the long-chain carboxylic acid, comparison was made with Example 2 described above. Then, although slightly inferior, it was found that good results were obtained in the friction coefficient, still durability, and shuttle durability under various use conditions.

From the above results, the surface of the protective film was treated with an aromatic alcohol, and a lubricant was used as a lubricant by using an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid as a lubricant. Forming a second lubricating layer by forming a lubricating layer of 1 and applying a lubricant containing an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid to the surface of the back coat layer; The lubricating agent maintains adhesion and lubricity under any use conditions and maintains the lubricating effect.
It was found that good running properties and durability of the magnetic recording medium were obtained. Further, the amount of the ester compound of the perfluoropolyether having a terminal hydroxyl group and the long-chain carboxylic acid contained in the second lubricating layer is determined by the amount of the perfluoropolyether having a terminal hydroxyl group contained in the first lubricating layer. By setting the amount of the ester compound of the ether and the long-chain carboxylic acid to twice or more, the lubricating effect is maintained for a longer period of time.
Furthermore, it was found that good running properties and durability of the magnetic recording medium were obtained.

Experimental Example 2 In this experimental example, the effect of using a lubricant containing an ester compound of a perfluoropolyether having a carboxyl group at the terminal and a long-chain alcohol was confirmed as follows. Experimental Example 2 is an example in which the first lubricating layer was formed using a sequential coating method.

(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 ) _p (OCF ₂ ) _q OCF ₂ COOH (however,
In the chemical formula, p and q each represent an integer of 1 or more. ), Stearyl alcohol having a molar ratio twice as high 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 in the above-mentioned compound 6. Synthesized. In Table 5, p, q, and n each represent an integer of 1 or more.

[0151]

[Table 5]

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 above-mentioned protective film was prepared by dissolving an aromatic alcohol as shown in Table 6 below in isopropyl alcohol, and applied to the surface of the carbon protective film at 10 mg / m 2.
² was applied.

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 form a first lubricating layer.

Further, each of the lubricants shown in Table 6 below dissolved in a hexane solvent was applied on the surface of the back coat layer in an amount of 5 mg / m ² and 10 mg / m ² respectively.
A ^second lubricating layer was formed by coating so as to have an m ² of 15 mg / m ² to obtain 15 types of magnetic recording media.

Then, each of these 15 types of magnetic recording media was cut into a 6.35 mm width to prepare 15 types of sample tapes of Examples 16 to 30.

[0156]

[Table 6]

[0157] 3. Evaluation of Characteristics Next, the characteristics of the 15 types of sample tapes of Examples 16 to 30 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 90 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 90 days.

[0159]

[Table 7]

[0160]

[Table 8]

From the results shown in Tables 7 and 8, in all of the sample tapes of Examples 16 to 30, the surface of the protective film formed by the CVD method was top-coated with an aromatic alcohol, and further, as a lubricant, Using a lubricant containing an ester compound of a perfluoropolyether having a carboxyl group and a long-chain alcohol to make the amount of the aromatic alcohol equal to or more than the amount of the lubricant, the carbohydrate group having a carboxyl group at the terminal on the back coat layer surface. Lubricant containing ester compound of fluoropolyether and long-chain alcohol is applied, so all of them have friction coefficient, still durability and shuttle 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 extremely little deterioration, and very good results were obtained.

The sample tape was heated at a temperature of 45 ° C.
After storage for 90 days in an environment of a humidity of 80% RH, the amount of the ester compound of the perfluoropolyether having a terminal carboxyl group and the long-chain alcohol contained in the second lubricating layer is reduced to the first amount. Example 17, Example 18, Example 20, Example 21, wherein the amount of the ester compound of the perfluoropolyether having a terminal carboxyl group and the long-chain alcohol contained in the lubricating layer is twice or more.
In Example 23, Example 24, Example 26, Example 27, Example 29, and Example 30, the friction coefficient, still durability, and the like under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature were all used. It was found that the deterioration of shuttle durability was extremely small, and very good results were obtained.

On the other hand, the amount of the ester compound of the perfluoropolyether having a carboxyl group at the terminal contained in the second lubricating layer and the long-chain alcohol was determined by adding the carboxyl group to the terminal contained in the first lubricating layer. In Example 16, Example 19, Example 22, Example 25, and Example 28 in which the amount of the ester compound of perfluoropolyether and long-chain alcohol was the same as in Example 2 described above, etc. Then, although slightly inferior, it was found that good results were obtained in the friction coefficient, still durability, and shuttle durability under various use conditions.

From the above results, the surface of the protective film was treated with an aromatic alcohol, and a lubricant was used as a lubricant by using an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol as a lubricant. Forming a second lubricating layer by forming a lubricating layer and applying a lubricant containing an ester compound of a perfluoropolyether having a terminal carboxyl group and a long-chain alcohol to the surface of the back coat layer; It has been found that the adhesion and lubricating properties are maintained and the lubricating effect is maintained under any use conditions of the lubricant, so that good running properties and durability of the magnetic recording medium can be obtained. Further, the amount of the lubricant containing the ester compound of the perfluoropolyether having a carboxyl group at the terminal and the long-chain alcohol contained in the second lubricating layer is changed to the amount of the terminal compound contained in the first lubricating layer. When the amount of the lubricant containing an ester compound of a perfluoropolyether having a carboxyl group and a long-chain alcohol is at least twice the amount of the lubricant, the lubricating effect is maintained for a longer period of time. It was found that running performance and durability were obtained.

[0165]

As described above in detail, the magnetic recording medium according to the present invention specifies and uses a lubricant having very excellent characteristics in terms of adhesion and lubricity, and therefore, the running performance is improved. And the durability can be improved.

In the magnetic recording medium according to the present invention, the surface of the protective film made of carbon, which is formed as the outermost layer,
A lubricant is retained on the protective film by being treated with a predetermined amount of aromatic alcohol, or is covered with a lubricant layer having a predetermined amount of aromatic alcohol and a predetermined lubricant. Adhesion with the protective film is improved, and better durability can be realized.

Further, in the magnetic recording medium according to the present invention, since the lubricating layer is also formed on the back coat layer, a predetermined amount of the lubricant can be held on the protective film, and the lubricating layer can be maintained for a long time. And good 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]

1 magnetic recording medium, 2 non-magnetic support, 3 magnetic layer, 4
Protective film, 5 back coat layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 5/735 G11B 5/735 // C10N 30:00 C10N 30:00 Z 40:18 40:18 (72 ) Inventor Yasumi Sato 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Hiroshi Yatakai 6-35-35 Kita-Shinagawa, Shinagawa-ku, Tokyo F-term inside Sony Corporation (reference) ) 4H104 BB05A CD04A LA20 PA16 4J038 BA041 BA08 CA001 CA021 CB021 CC021 CD021 CD091 CE021 CE051 CE061 CF031 CG031 CG131 CG161 DA061 DA131 DA221 DB001 DC001 DD001 DF002 DG001 GA02 HA066 HA166 JA02 NA02 A01 A03 A06 A02 A03 A02 CC

Claims (14)

[Claims] 1. A non-magnetic support, a magnetic layer formed on one main surface of the non-magnetic support, a protective film formed on the magnetic layer, and another main surface of the non-magnetic support A magnetic recording medium comprising a back coat layer formed thereon, an aromatic alcohol, an ester of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid represented by the following chemical formula: And a second lubricating layer having an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid represented by the following chemical formula on the back coat layer. A magnetic recording medium comprising a layer formed. Embedded image 2. The magnetic recording medium according to claim 1, wherein the amount of the aromatic alcohol is equal to or more than the amount of the compound represented by Chemical Formula 1 formed on the protective film. 3. The chemical formula 1 contained in the second lubricating layer.
2. The magnetic recording medium according to claim 1, wherein the amount of the compound represented by the formula (1) is at least twice the amount of the compound represented by the formula (1) contained in the first lubricating layer. 4. The magnetic recording medium according to claim 1, wherein said magnetic layer comprises 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 one main surface of the nonmagnetic support, a protective film formed on the magnetic layer, and another main surface of the nonmagnetic support. A magnetic recording medium comprising a back coat layer formed thereon, an aromatic alcohol, an ester of a perfluoropolyether having a carboxyl group at a terminal represented by the following chemical formula 2, and a long-chain alcohol, A first lubricating layer having a compound is formed on the back coat layer, and a second lubricating layer having an ester compound with a perfluoropolyether having a terminal carboxyl group and a long-chain alcohol represented by the following chemical formula (2) A magnetic recording medium comprising a lubricating layer formed thereon. Embedded image 9. The magnetic recording medium according to claim 8, wherein the amount of the aromatic alcohol is equal to or more than the amount of the compound represented by Chemical Formula 2 formed on the protective film. 10. The amount of the compound represented by Chemical Formula 2 contained in the second lubricating layer is twice or more the amount of the compound represented by Chemical Formula 2 contained in the first lubricating layer. 9. The magnetic recording medium according to claim 8, wherein: 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.