JP2002146375A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium implementing excellent movability and durability, preventing the abrasion of a head and the deterioration of magnetic properties under any working condition, and having excellent storage property by using a lubricant having excellent lubricating effect and protected from the occurrence of powder falling, and at the same time by increasing sticking stability between a protection film and a lubricant layer. SOLUTION: The magnetic recording medium has a magnetic layer 3 consisting of a ferromagnetic metal material, a protecting film 4 and a lubricant layer 6 on a nonmagnetic supporting body 2. The lubricant layer 6 contains, as a lubricant, a compound which is expressed by chemical formula 1 (wherein, Rf is a perfluoropolyether chain; and R1, R2, R3, R4, R5 and R6 are each H or a hydrocarbon group), and is obtained from bifunctional perfluoropolyether having a carboxy group at the terminal and an amine. The magnetic recording medium is used for a helical scanning magnetic record regenerative system using a magnetoresistance effect-type reproducing head. In the magnetic recording medium, an aromatic carboxylic acid-containing absorbing layer 5 is placed between the protecting film 4 and the lubricant layer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium having a magnetic layer made of a ferromagnetic metal material, a protective film, and a lubricant layer containing a lubricant on a nonmagnetic support.

[0002]

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

On the other hand, a ferromagnetic metal magnetic material is coated on a non-magnetic support such as a polyester film or a polyamide film by a vacuum thin film forming technique such as a vacuum evaporation method, a sputtering method, or an ion plating method, or by plating. A magnetic recording medium of a so-called ferromagnetic metal thin film type, in which a magnetic layer is formed by directly applying a magnetic layer, has been used with an increasing demand for high-density recording and long-time recording. Such a ferromagnetic metal thin film type magnetic recording medium has been widely put into practical use in a consumer video format (8 mm Hi-8 format, DV format) or a professional video format (DVCAM).

[0004] A magnetic recording medium of the ferromagnetic metal thin film type is superior in magnetic properties such as coercive force and squareness ratio to a coating type magnetic recording medium, and is superior in electromagnetic conversion characteristics in a short wavelength region. Further, the magnetic recording medium of the ferromagnetic metal thin film type has a very small thickness of the magnetic layer, so that the thickness loss at the time of recording demagnetization and reproduction is extremely small, and the magnetic layer contains a nonmagnetic material such as an organic binder. Since there is no need to mix a binder, there are many advantages such as a high packing density of the magnetic material.

[0005] In recent years, the size of magnetic recording / reproducing apparatuses has been reduced. Along with this, magnetic recording media used in miniaturized magnetic recording / reproducing devices are required to achieve a high recording capacity while at the same time miniaturizing the shape. Has been requested.

Japanese Patent Application Laid-Open No. H11-203652 discloses a magnetic recording medium compatible with such high-density recording.
Highly sensitive magnetoresistive read head (hereinafter simply referred to as MR
It is called a head. ) Discloses a ferromagnetic metal thin film type magnetic recording medium having a magnetic layer optimized for reproduction by the helical scan method.

In general, during traveling with a helical scan type magnetic recording / reproducing apparatus, the magnetic recording medium is constantly in contact with a sliding member such as a magnetic head while traveling at a high speed. And very susceptible to damage. Therefore, as shown in FIG. 2, a magnetic recording medium 101 of a ferromagnetic metal thin film type has a protective film 10 made of carbon or the like on a magnetic layer 103 formed on a nonmagnetic support 102.
4 and a structure having a lubricant layer 105 containing a lubricant on the protective film 104. The provision of the protective film 104 and the lubricant layer 105 can improve the running property and durability of the magnetic recording medium 101 of the ferromagnetic metal thin film type.

However, the protective film and the lubricant formed for the purpose of achieving good running performance and durability are shaved by the magnetic head during running, and the shavings of the shaved protective film and the lubricant, so-called powder fall-off. May occur. If this powder drop accumulates, there is a problem that a predetermined signal output cannot be obtained because spacing occurs between the magnetic recording medium and the magnetic head. Further, there is a problem that the magnetic head is worn due to the contact between the magnetic film and the portion where the protective film or the lubricant has been removed.

In recent years, in magnetic recording media of the ferromagnetic metal thin film type, it has been practiced to improve the surface smoothness by a surface smoothing process such as a super calendar process for the purpose of reducing spacing loss and improving electromagnetic conversion characteristics. Have been done. However, when the surface smoothness of the magnetic layer is extremely good,
The substantial contact area with the magnetic head increases, and the coefficient of friction with the magnetic head tends to be higher. Further, as the recording time increases, the sliding time with the magnetic head becomes longer, and the scanning speed tends to become faster. However, these tendencies promote powder generation.

[0010] For example, Japanese Patent Application Laid-Open No. 11-203652 discloses that a magnetic layer optimized according to the characteristics of an MR head is provided. A magnetic recording medium exhibiting an effect is disclosed. However, when perfluoropolyether was used as the lubricant, powder dropping could not be sufficiently prevented, and as a result, the level was reduced and the head was worn.

Therefore, in the field of magnetic recording, the magnetic head is generally physically polished using a so-called cleaning tape in order to remove powder dropout accumulated on the magnetic head. However, when the magnetic head is polished by a physical method, if the polishing force is too high, the magnetic head is polished more than necessary, and the characteristics of the magnetic head may be deteriorated.

In particular, the characteristics of an MR head and an inductive type thin film magnetic head mainly composed of a metal thin film formed by a thin film forming technique are easily deteriorated by wear. For this reason, a cleaning tape cannot be used for a magnetic head formed by a thin film forming technique, for example, an MR head, in order to remove powder drops accumulated in the MR head. That is, when powder dust has accumulated in the MR head, there is no means for removing the powder dust. Therefore, it is necessary to design a lubricant in which the occurrence of powder dropping itself is prevented.

[0013]

When a magnetic recording medium is running in a helical scan type magnetic recording / reproducing apparatus, not only the magnetic recording medium but also the magnetic head is contacted and slid between the magnetic recording medium and the magnetic head. Are also very susceptible to wear and damage. In particular, when an MR head is used as a reproducing head in a helical scan type magnetic recording / reproducing device, as described above,
In the head, the characteristic deterioration due to wear is remarkable as compared with the conventional inductive type head, and there is a possibility that the reproduction cannot be performed by using the head for a long time.

For this reason, the protective film of the magnetic recording medium used in the helical scan type magnetic recording / reproducing apparatus using the MR head has sufficient running property and durability, and the magnetic head has a good protection. It is required to have a strength that shows a small polishing force.

In recent years, it has been studied to form a protective film made of carbon or the like by a CVD method. CVD
The carbon protective film formed by the method has a soft and moderate strength as compared with the carbon protective film formed by the sputtering method, while reliably protecting the magnetic layer. For this reason, it exhibits excellent running properties and durability, and has a small polishing force for the magnetic head, and exhibits an optimum strength for a helical scan type magnetic recording / reproducing apparatus using an MR head.

Moreover, when the carbon protective film is formed by the CVD method, high-speed film formation is possible, the coverage is high, power saving is achieved, as compared with the case where the carbon protective film is formed by the sputtering method. It 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 layer are improved by 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 carbon protective film formed by the CVD method is different from the carbon protective film formed by the sputtering method.
Low surface energy. Therefore, as described above, when a lubricant is used to improve the durability and running properties of the magnetic recording medium, the adsorption between the lubricant and the carbon protective film is weak, and a stable and good lubricating effect is not exhibited. Further, since the adsorption stability between the carbon protective film and the lubricant is poor, there is a problem that the lubricating effect is easily deteriorated when the magnetic recording medium is stored for a long time.

Accordingly, the present invention has been proposed in view of such a conventional situation. The present invention uses a lubricant having an excellent lubricating effect and preventing generation of powder, and a protective film and a lubricant layer. The present invention provides a magnetic recording medium that achieves excellent running properties and durability under any use conditions, prevents head abrasion and deterioration of magnetic characteristics, and has excellent storage characteristics by increasing the adhesion stability with the recording medium. The purpose is to:

[0019]

In order to achieve the above object, a magnetic recording medium according to the present invention comprises a magnetic layer made of a ferromagnetic metal material, a protective film, and a lubricant on a nonmagnetic support. And a lubricant layer containing a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal and an amine represented by the following formula (4). The magnetic recording medium to be used is characterized in that an adsorption layer containing an aromatic carboxylic acid is provided between the protective film and the lubricant layer.

[0020]

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In the magnetic recording medium constructed as described above, the adsorbing layer containing an aromatic carboxylic acid is interposed between the protective film and the lubricant layer, so that the adhesion between the protective film and the lubricant layer is improved. Stability is improved. For this reason, deterioration of the lubricity when the magnetic recording medium is stored for a long time is suppressed. In addition, the magnetic recording medium according to the present invention uses a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal represented by the above formula (4) and an amine as a lubricant, so that it can be lubricated under any use conditions. The property is kept good, and the occurrence of powder drop is prevented.

Further, the magnetic recording medium according to the present invention has a magnetic layer made of a ferromagnetic metal material, a protective film, and a carboxyl group at a terminal represented by the following formula (5) as a lubricant on a nonmagnetic support. A magnetic recording medium used in a helical scan magnetic recording / reproducing system using a magnetoresistive read head, comprising: a lubricant layer containing a compound of perfluoropolyether and an amine; And an adsorption layer containing an aromatic carboxylic acid.

[0023]

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In the magnetic recording medium constructed as described above, the adsorbing layer containing an aromatic carboxylic acid is interposed between the protective film and the lubricant layer, so that the adhesion between the protective film and the lubricant layer is improved. Stability is improved. For this reason, deterioration of the lubricity when the magnetic recording medium is stored for a long time is suppressed. In addition, the magnetic recording medium according to the present invention uses a compound of a perfluoropolyether having a carboxyl group at a terminal represented by the above formula (5) and an amine as a lubricant, and thus has lubricity under any use conditions. While keeping good, the occurrence of powder drop is prevented.

Further, the magnetic recording medium according to the present invention has a magnetic layer made of a ferromagnetic metal material, a protective film, and a carboxyl group at a terminal represented by the following formula (6) as a lubricant on a nonmagnetic support. A magnetic recording medium used for a helical scan magnetic recording / reproducing system using a magnetoresistive read head, comprising: a lubricant layer containing a compound of perfluoropolyether and a diamine; And an adsorption layer containing an aromatic carboxylic acid.

[0026]

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In the magnetic recording medium constructed as described above, the adsorbing layer containing an aromatic carboxylic acid is interposed between the protective film and the lubricant layer, so that the adhesion between the protective film and the lubricant layer is improved. Stability is improved. For this reason, deterioration of the lubricity when the magnetic recording medium is stored for a long time is suppressed. Further, the magnetic recording medium according to the present invention uses a compound of a perfluoropolyether having a carboxyl group at a terminal represented by the above formula (6) and a diamine as a lubricant, and thus has lubricity under any use conditions. While keeping good, the occurrence of powder drop is prevented.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetic recording medium according to the present invention will be described in detail with reference to the drawings.

<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 metal magnetic thin film is formed as a magnetic layer 3 on one main surface of a non-magnetic support 2, and a protective film 4 is formed on the magnetic layer 3. Then, an adsorption layer 5 is formed on the protective film 4, and a lubricant layer 6 is formed as an uppermost layer on the adsorption layer 5.

As the non-magnetic support 2, any one can be used as long as it is used as a non-magnetic support in an ordinary magnetic recording medium. Specifically, polyesters such as polyethylene terephthalate and polyethylene naphthalate; Polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, and plastics such as polycarbonate, polyimide, polyamide and polyamide imide can be used.

As the non-magnetic support 2, there can be used a non-magnetic support having at least one of projections, wrinkles, and granular projections formed on the surface thereof and having a controlled surface roughness. .

In the magnetic recording medium 1, the surface properties of the magnetic layer 3 can be controlled by forming at least one of the mountain-like projections, wrinkle-like projections, and granular projections on the non-magnetic support 2. The effect is increased by combining at least two or more of these projections. In particular, when wrinkled projections and granular projections are formed on the nonmagnetic support 2 on which the mountain-shaped projections are formed, the durability and running properties are significantly improved. You. In this case, the overall height of the protrusion is 10 nm to 200 n.
m, and the density is 1 × 10
^The number is preferably ⁵ / mm ² to 1 × 10 ⁷ / mm ² .

When the non-magnetic support 2 is manufactured,
It is formed by internally adding inorganic fine particles having a particle size of about 50 nm to 300 nm into the nonmagnetic support 2. The height of the ridge is 10 nm to 100 from the nonmagnetic support 2.
nm, and the density of the peaks is about 1 ×
It is preferable that the number is 10 ⁴ pieces / mm ² to 1 × 10 ⁵ pieces / mm ² . It is preferable to use calcium carbonate, silica, alumina, or the like as the inorganic fine particles to be internally added to the nonmagnetic support 2 when forming the mountain-like projections.

The wrinkle-like projections are formed by applying a dilute solution of a resin using a specific mixed solvent on the nonmagnetic support 2 and drying it. The height of the wrinkled protrusion is 0.0
1 μm to 1 μm, preferably 0.03 μm
More preferably, it is 0.5 μm. The shortest interval between the wrinkle-like projections is preferably 0.1 μm to 20 μm.

Examples of the resin for forming wrinkle-like projections include polyester such as polyethylene terephthalate and polyethylene naphthalate, polyamide, polystyrene, polycarbonate, polyacrylate, polysulfone, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, and polyphenylene. A simple substance, a mixture or a copolymer of an oxide and a phenoxy resin can be used, and those having a soluble solvent are 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 of the resin and has a boiling point higher than that of the good solvent is 10 times the amount of the resin. A thin layer having very fine wrinkle-like protrusions can be formed by applying the solution added in an amount of about 100 times to the surface of the non-magnetic support 2 and drying it.

The granular protrusions are formed by adhering organic ultrafine particles such as acrylic resin or inorganic fine particles such as silica or metal powder on the non-magnetic support 2 in a spherical or hemispherical shape. The height of the granular projections is preferably 5 nm to 50 nm, and the density of the granular projections is 1 × 10 ⁶ / mm ^2.
It is preferable to be 5 × 10 ⁷ pieces / mm ² .

The magnetic layer 3 is formed by a so-called physical vapor deposition method (PVD: Physical vapor deposition) such as plating, sputtering, or vacuum deposition.
It is formed by directly applying a ferromagnetic metal material on the non-magnetic support 2 by the technique of Vapor Deposition. That is, the magnetic layer 3 is a metal magnetic thin film made of a ferromagnetic metal material. The thickness of the magnetic layer 3 formed by such a method is preferably 0.01 μm to 1 μm.

The ferromagnetic metal material for forming the magnetic layer 3 includes:
For example, metals such as Fe, Co and Ni, Co-Ni alloys,
Co-Pt alloy, Co-Pt-Ni alloy, Fe-C
o-based alloy, Fe-Ni-based alloy, Fe-Co-Ni-based alloy, Fe-Ni-B-based alloy, Fe-Co-B-based alloy, F
An e-Co-Ni-B-based alloy, a Co-Cr-based alloy, or an alloy containing a metal such as Pt or Al can be used.

The metal magnetic thin film includes an in-plane magnetized film and a perpendicular magnetized film. In particular, when a Co—Cr alloy is used, the perpendicular magnetized film is formed.

When an in-plane magnetized film is formed, Bi, Sb, Pb, Sn, Ga, In, Ge,
It is preferable to previously form an underlayer made of a low-melting nonmagnetic material such as Si or Tl. When the metal magnetic material described above is deposited or sputtered from the vertical direction of the non-magnetic support 2 to form a metal magnetic thin film, by diffusing these low-melting non-magnetic materials, the orientation of the metal magnetic thin film is improved. This is eliminated to ensure in-plane isotropy and improve antimagnetism.

The protective film 4 is formed, for example, by depositing carbon on the magnetic layer 3 by chemical vapor deposition (CVD).
ion) or the like. The protective film 4 formed by the CVD method has a moderate strength which is softer than, for example, a carbon protective film formed by the sputtering method, and maintains a balance between the polishing force on the magnetic recording medium and the function of protecting the magnetic layer. Dripping.

The thickness of the protective film 4 is preferably 2 nm to 100 nm, more preferably 5 nm to 30 nm. If the thickness of the protective film 4 is less than 2 nm, the durability of the protective film 4 may be insufficient. On the other hand, if the thickness of the protective film 4 exceeds 100 nm, there is a possibility that sufficient output may not be obtained when performing short-wavelength recording.

In the magnetic recording medium 1 to which the present invention is applied, on the protective film 4, an adsorption layer 5 containing an aromatic carboxylic acid is formed. The details of the adsorption layer 5 will be described later.

The lubricant layer 6 is made of a lubricant coating obtained by dissolving a lubricant containing a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal and an amine represented by the following formula 7 in a solvent: It is formed by coating on the adsorption layer 5.

[0047]

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As described above, the lubricant containing the compound represented by Chemical Formula 7 has excellent lubricating properties and prevents powder dropping.

The compound of a bifunctional perfluoropolyether having a terminal carboxyl group and an amine represented by the above formula 7 can be obtained, for example, by mixing the bifunctional perfluoropolyether having a terminal carboxyl group with an amine. It is synthesized by heating at a temperature higher than the melting point of the amine. For example, when stearylamine is used as the amine, the mixture may be heated and mixed at 60 ° C.

The compound of the bifunctional perfluoropolyether having a terminal carboxyl group and the amine represented by the above formula (7) is obtained by dissolving the bifunctional perfluoropolyether having a terminal carboxyl group and the amine in an organic solvent. After that, it can also be obtained by removing the solvent.

As the bifunctional perfluoropolyether having a terminal carboxyl group used in synthesizing the compound represented by the above formula 7, any commercially available product can be used. For example, HOOC-CF ₂ (OCC ₂ F _{4) p} (O
CF ₂ ) _q OCF ₂ —COOH or the like can be used. In addition,
P and q in the structural formula in the perfluoropolyether represent an integer of 1 or more.

The molecular weight of the bifunctional perfluoropolyether having a carboxyl group at the terminal is not particularly limited, but practically preferably about 600 to 5,000. If the molecular weight of the bifunctional perfluoropolyether having a carboxyl group at the terminal is too large, the effect of the terminal group as an adsorbing group is diminished and, at the same time, the perfluoropolyether chain is enlarged, and the solvent is dissolved in an existing hydrocarbon solvent There is a possibility that it becomes difficult to perform. Conversely, if the molecular weight of the bifunctional perfluoropolyether having a carboxyl group at the terminal is too small, the lubricating effect of the perfluoropolyether chain may be lost.

In the bifunctional perfluoropolyether having a carboxyl 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.

Further, as the amine used for synthesizing the compound represented by the chemical formula 7, any of primary amine, secondary amine and tertiary amine can be used, and quaternary ammonium compound can also be used. it can. The structure of the amine to be used is also arbitrary, and can be arbitrarily selected regardless of the branched structure, isomer structure, alicyclic structure, molecular weight, and presence or absence of an unsaturated bond. However, the amine preferably has an alkyl group, and particularly when the amine has an alkyl group having 10 or more carbon atoms, the effect is large.

When the amine is a quaternary ammonium compound, the compound of the bifunctional perfluoropolyether having a carboxyl group at the terminal represented by the above formula (7) and the amine is a metal salt of perfluoropolyether ( Sodium salt) and a quaternary ammonium salt (chloride, iodide, sulfate, etc.), and can be obtained by extraction with an organic solvent.

The lubricant layer 6 contains not only a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal shown in Chemical formula 7 and an amine but also a combination of a conventionally known lubricant. It is also possible.

The amount of the lubricant to be applied is 0.05 mg / m ² to
100 mg / m ² , preferably 0.1 mg / m ²
more preferably ^{m 2} ~50mg / m ^2. If the amount of the lubricant applied is too small, the effects of lowering the friction coefficient and improving the wear resistance and durability may not be sufficiently exhibited. On the other hand, if the amount of the applied lubricant is too large, a shearing phenomenon occurs between the sliding member and the magnetic layer 3, and the running property is rather deteriorated.

This lubricant layer 6 can contain a rust preventive. In this case, a rust inhibitor is added to the lubricant paint. As the rust inhibitor, known materials and the like which are usually used as a rust inhibitor for this type of magnetic recording medium can be used. Specifically, for example, phenols, naphthols, quinones,
A heterocyclic compound containing a nitrogen atom, a heterocyclic compound containing an oxygen atom, a heterocyclic compound containing a sulfur atom, and the like can be used.

Further, the rust preventive is not contained in the lubricant layer 6,
A rust preventive layer may be formed between the protective film 4 and the lubricant layer 6. By forming the rust preventive agent layer and the lubricant layer 6 separately in two layers, the rust preventive effect and the lubricating effect are further enhanced.

The magnetic recording medium 1 has a support reinforcing layer (not shown) and a back coat (not shown) on the other main surface of the nonmagnetic support 2 on which the magnetic layer 3 is formed. It is possible to form a layer.

The support reinforcing layer is made of Mg, Al, Si, Ti,
V, Cr, Fe, Co, Ni, Cu, Zn, Ge, Z
Metals such as r, Nb, Mo, W, etc., and alloys and oxides of these metals are preferable. As a method of forming the support reinforcing layer, a film forming method such as an evaporation method, a sputtering method, and an ion plating method can be applied. The thickness of the support reinforcing layer is preferably 20 nm to 500 nm.

The back coat layer is formed by applying a back coat paint in which a powder component and a binder are mixed and dispersed in an organic solvent to the non-magnetic support 2.

Examples of the powder component include carbon black for imparting conductivity, and inorganic powder added for controlling surface roughness and improving durability.

As the carbon black to be contained in the back coat layer, two types of carbon blacks having different average particle diameters, specifically, fine carbon black having an average particle diameter of 10 nm to 20 nm, and carbon black having an average particle diameter of 230 nm
It is preferable to use coarse-grain carbon black having a thickness of about 300 nm.

When particulate carbon black is added to the back coat layer, the surface electric resistance of the back coat layer is reduced and the light transmittance is reduced. There are many magnetic recording medium recording / reproducing devices that use the light transmittance of a tape for operation signals. In such a case, the addition of fine carbon black is particularly effective. Further, since the particulate carbon black is excellent in the holding power of the lubricant, when the lubricant is added to the back coat layer, it contributes to the reduction of the friction coefficient.

When coarse-grained carbon black is added to the back coat layer, fine projections are formed on the surface of the back coat layer, so that the contact area with the sliding member is reduced, and the friction coefficient is reduced. That is, the coarse carbon black has a function as a solid lubricant. But,
Coarse particle carbon black is likely to drop from the back coat layer due to tape sliding in a severe running system, and may cause an increase in the error ratio.

When two types of carbon blacks having different average particle diameters are added to the back coat layer, the addition ratio (weight ratio) between the fine carbon black and the coarse carbon black is 98: 2 to 75:25. Preferably,
The ratio is more preferably from 95: 5 to 85:15. The amount of carbon black (the total amount of fine particles and coarse particles when added) in the back coat layer is 30 parts by weight with respect to 100 parts by weight of a binder described later.
The amount is preferably from 80 to 80 parts by weight, more preferably from 45 to 65 parts by weight.

Specific examples of the particulate carbon black include RAVEN 2000 manufactured by Columbia Carbon Co., Ltd.
B (18 nm), RAVEN 1500B (17 nm),
BP800 (17 nm) manufactured by Cabot, PRINTEX 90 (14 nm) manufactured by Degussa, PRINTEX
95 (15 nm), PRINTEX 85 (16 nm),
PRINTEX 75 (17 nm), Mitsubishi Chemical Industry Co., Ltd.
# 3950 (16 nm) or the like can be used.

Specific examples of commercial products of coarse-grain carbon black include thermal black (270 nm) manufactured by Khancarb and RAVEN manufactured by Columbia Carbon.
MTP (275 nm) can be used.

On the other hand, as the inorganic powder contained in the back coat layer, it is preferable to use calcium carbonate and an inorganic powder having a Mohs hardness of 5 to 9. When an inorganic powder having a Mohs hardness of 5 to 9 is added to the back coat layer together with, for example, calcium carbonate or the above-described carbon black, the filler effect makes it difficult for the back coat layer to be repeatedly deteriorated even in sliding, and has a high strength. Becomes

When an inorganic powder having a Mohs hardness of 5 to 9 is contained in the back coat layer, an appropriate polishing force is generated on the surface of the back coat layer and adhesion to a tape guide pole or the like is reduced. In particular, when this inorganic powder and calcium carbonate are used in combination, the sliding characteristics of the magnetic recording medium 1 with respect to the guide pole having a rough surface are improved, and the friction coefficient of the back coat layer is stabilized.

The average particle size of the inorganic powder having a Mohs hardness of 5 to 9 is preferably 80 nm to 250 nm, and
More preferably, the thickness is from 00 nm to 210 nm. The amount of the inorganic powder having a Mohs hardness of 5 to 9 is preferably 3 to 30 parts by weight, and more preferably 3 to 20 parts by weight, per 100 parts by weight of the carbon black.

The Mohs hardness added to the back coat layer is 5
As the inorganic powders of No. 9 to No. 9, for example, α-iron oxide, α-alumina, and chromium oxide can be used, and among them, α-iron oxide or α-alumina is preferably used. The inorganic powder having a Mohs hardness of 5 to 9 may be added alone or in combination.

As the binder contained in the back coat layer, for example, a thermoplastic resin, a thermosetting resin, a reactive resin or a mixture thereof can be used.

As the thermoplastic resin, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acuric acid,
Acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene,
A polymer or a copolymer containing butadiene, ethylene, vinyl butyral, vinyl acetal, vinyl ether and the like as constituent units can be used.

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, acrylate-styrene copolymer, methacrylate-acrylonitrile copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-styrene copolymer, vinylidene chloride-acrylonitrile copolymer Polymer,
Butadiene-acrylonitrile copolymer, styrene-butadiene copolymer, chlorovinyl ether-acrylate copolymer and the like can be used. Further, polyamide resins, cellulose resins such as cellulose acetate butyrate and cellulose diacetate, cellulose propionate and nitrocellulose, polyvinyl fluoride, polyester resins, polyurethane resins, various rubber resins, and the like can also be used.

Examples of the thermosetting resin or reactive resin include phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic-based reactive resin, formaldehyde resin, silicone resin, and epoxy-polyamide resin. A mixture of a polyester resin and a polyisocyanate prepolymer, a mixture of a polyester polyol and a polyisocyanate, and a mixture of a polyurethane and a polyisocyanate can be used.

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, benzene, toluene, aromatic hydrocarbon solvents such as xylene, Hexane,
Aliphatic hydrocarbon solvents such as heptane, methylene chloride, ethylene chloride, carbon tetrachloride, chloroform,
Chlorinated hydrocarbon solvents such as ethylene chlorohydrin and dichlorobenzene can be used.

Further, a lubricant can be used in combination with the back coat layer. In this case, there is a method in which a lubricant is internally added to the back coat layer, or a method in which the lubricant is retained on the back coat layer. As the lubricant, any of conventionally known lubricants such as fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, and silicone-based lubricants can be used.

As described above, in the magnetic recording medium 1 to which the present invention is applied, the adsorbing layer 5 containing an aromatic carboxylic acid is provided between the protective film 4 and the lubricant layer 6 as the uppermost layer. Is formed. The adsorption layer 5 is formed by applying an adsorption layer paint obtained by dissolving an aromatic carboxylic acid in a solvent on the protective film 4.

By forming the adsorbing layer 5 between the protective film 4 and the lubricant layer 6, the π electrons existing on the surface of the protective film 4 and the π electrons of the aromatic carboxylic acid molecules of the adsorbing layer 5 are reduced. It adsorbs by resonance, and the amino group of the aromatic carboxylic acid molecule of the adsorption layer 5 and the polar group of the lubricant molecule of the lubricant layer 6 are adsorbed. Since the adhesion stability between the protective film 4 and the lubricant layer 6 is improved by interposing the adsorption layer 5, the lubricity of the lubricant layer 6 is maintained even when the magnetic recording medium 1 is stored for a long period of time. Deterioration is suppressed. Therefore, the magnetic recording medium 1 maintains good running durability for a long period of time, and prevents head wear and deterioration of magnetic characteristics.

Specific examples of the aromatic carboxylic acids as described above include phthalic acid, terephthalic acid, isophthalic acid, benzoic acid, salicylic acid, gallic acid, galloyl gallic acid, opianic acid, vanillic acid, piperonyl acid, piperine Acid, carminic acid, hesperitic acid, benzenehexacarboxylic acid, 2-cyclohexene-1,2-dicarboxylic acid,
4-cyclohexene-1,2-dicarboxylic acid, 6-hydroxy-5-isopropyl-o-toluic acid, 4-hydroxy-3-methoxycinnamic acid and the like.

The magnetic recording medium 1 configured as described above
Is manufactured as follows.

First, a metal magnetic thin film is formed as a magnetic layer 3 on one main surface of the nonmagnetic support 2 by a vacuum thin film forming technique such as a vacuum deposition method, an ion plating method, or a sputtering method.

When the magnetic layer 3 is formed by a vacuum deposition method, the magnetic layer 3 is formed under a vacuum of 1 × 10 ⁻⁶ Pa to 1 × 10 ⁻² Pa.
The ferromagnetic metal material is evaporated 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. In the vacuum vapor deposition method, oblique vapor deposition is generally used in which the ferromagnetic metal material is obliquely vapor-deposited on the nonmagnetic support 2 in order to obtain a high coercive force.
In order to obtain an even higher coercive force, vacuum deposition may be performed in an oxygen atmosphere.

When the magnetic layer 3 is formed by an ion plating method, which is one type of vacuum evaporation, 1 × 10
D in an inert gas atmosphere of ⁻² Pa to ¹ × 10 ⁻¹ Pa
A C glow discharge or an RF glow discharge is caused, the ferromagnetic metal material is evaporated during the discharge, and the evaporated metal (ferromagnetic metal material) is deposited on the nonmagnetic support 2.

Further, when the magnetic layer 3 is formed by sputtering, glow discharge is caused in an atmosphere containing 0.1 Pa to 10 Pa of Ar gas as a main component, and the generated Ar gas ions strike out atoms on the target surface. ,
This atom is deposited on the non-magnetic support 2. Specific examples of the sputtering method include a DC two-pole, three-pole sputtering method, a high-frequency sputtering method, and a magnetron sputtering method using magnetron discharge.

Next, on this magnetic layer 3, for example, CVD
A protective film 4 is formed by a method.

In the case of forming the protective film 4 by the CVD method, for example, a hydrocarbon gas or a mixed gas of a hydrocarbon gas and an inert gas is introduced into a vacuum vessel, and a pressure of 10 Pa to 10 Pa is applied.
While maintaining the pressure at about 100 Pa, a discharge is made in the vacuum vessel to generate a hydrocarbon gas plasma, and the protective film 4 is formed on the magnetic layer 3.

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 magnetic layer 3 is formed, the hardness and adhesion of the protective film 4 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. .

Next, an adsorption layer paint is prepared by dissolving the aromatic carboxylic acid in a solvent, and the adsorption layer paint is applied on the protective film 4 to form the adsorption layer 5.

As a solvent used for preparing an adsorbent layer paint for forming the adsorbent layer 5, isopropyl alcohol or the like can be used.

Next, a lubricant paint is applied on the adsorption layer 5 to form a lubricant layer 6.

First, a lubricant containing a compound of a bifunctional perfluoropolyether having a carboxyl group at the terminal and an amine represented by Chemical formula 7 and an amine is dissolved in a solvent to prepare a lubricant coating. Next, the lubricant paint is applied to the adsorption layer 5.
The lubricant layer 6 is formed by being applied thereon.

As the solvent used for preparing the lubricant coating, any of a fluorine-based solvent and a hydrocarbon-based solvent such as toluene and acetone can be used.

The compound of a bifunctional perfluoropolyether having a carboxyl group at the terminal and an amine represented by Chemical formula 7 has a fluorine atom in the molecule, similarly to a conventional fluorine-containing lubricant. However, the conventional fluorine-containing lubricant dissolves only in a fluorine-based solvent, whereas the compound represented by Chemical formula 7 dissolves not only in a fluorine-based solvent but also in a hydrocarbon-based solvent such as toluene and acetone.

That is, when forming the lubricant layer 6 containing the compound shown in Chemical formula 7, the solvent of the lubricant paint is
It is possible to use a hydrocarbon-based solvent having a very small effect on the environment as compared with a fluorine-based solvent.

The amount of the aromatic carboxylic acid applied when forming the adsorption layer 5 is preferably equal to or more than the amount of the lubricant applied when forming the lubricant layer 6. If the amount of the aromatic carboxylic acid applied when forming the adsorbing layer is below the above-mentioned range, the aromatic carboxylic acid molecules are insufficient, so that the adsorbing power of the lubricant is weakened and the adhesion between the protective film and the lubricant layer is stable. May be insufficient.

In the magnetic recording medium 1 having the structure described above, since the adsorbing layer 5 containing an aromatic carboxylic acid is formed between the protective film 4 and the lubricant layer 6, the protective film 4 and the lubricant The adhesion stability with the layer 6 becomes very excellent, and the lubricity of the lubricant layer 6 can be maintained well even after long-term storage. Further, since the magnetic recording medium 1 is provided with the lubricant layer 6 containing a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal represented by Chemical formula 7 and an amine as a lubricant, the lubricating property is very high. It is excellent and prevents powder from falling, has good running properties and durability under any use conditions, and prevents head wear and deterioration of magnetic properties.

Therefore, under any conditions of use, it exhibits good running properties and durability, prevents powder dropping, prevents output reduction and head wear, and can maintain those effects for a long period of time. Recording medium 1
Is realized.

Further, since the magnetic recording medium 1 is prevented from falling off the powder and has an increased adsorbing force of the lubricant by interposing the adsorbing layer 5, a protective film having a small surface energy, for example, a CVD method is used. It becomes possible to use a carbon protective film formed by such a method. Therefore, the magnetic recording medium 1 to which the present invention is applied is most suitable for use in a helical scan magnetic recording / reproducing system using an MR head. <Second Embodiment> Next, a second embodiment of the present invention will be described. The magnetic recording medium according to the present embodiment is a magnetic recording medium 1 according to the first embodiment shown in FIG.
Similarly, a ferromagnetic metal thin film as a magnetic layer on a non-magnetic support, a protective film on the magnetic layer, an adsorption layer containing an aromatic carboxylic acid on the protective film, and a lubricant containing a lubricant on the adsorption layer The layers are sequentially formed. In the magnetic recording medium according to the present embodiment, a compound of perfluoropolyether having a carboxyl group at a terminal and an amine represented by the following formula 8 is used as a lubricant for the lubricant layer.

[0103]

Embedded image

As described above, the lubricant containing the compound represented by Chemical Formula 8 has excellent lubricating properties and prevents powder from falling off.

The magnetic recording medium using the lubricant represented by Chemical Formula 8 has substantially the same configuration as the magnetic recording medium 1 shown in FIG. 1, and the lubricant held in the outermost layer Only different examples, other magnetic layers, protective films,
The adsorption layer and the like have the same configuration. Therefore, in the following description,
Only the lubricant will be described.

The compound of a perfluoropolyether having a carboxyl group at a terminal and an amine represented by the above formula 8 is, for example, a mixture of a perfluoropolyether having a carboxyl group at a terminal and an amine, and the melting point of the amine used. It is synthesized by heating at a temperature higher than the temperature.
For example, when stearylamine is used as the amine, the mixture may be heated and mixed at 60 ° C.

The compound of perfluoropolyether having a carboxyl group at a terminal and an amine represented by the above formula 8 is obtained by dissolving a perfluoropolyether having a carboxyl group at a terminal and an amine in an organic solvent, and then dissolving the solvent in an organic solvent. Can also be obtained by removing

As the perfluoropolyether having a carboxyl group at the terminal used for synthesizing the compound represented by the above formula 8, any of commercially available products can be used.
For example, F (CF ₂ CF ₂ CF ₂ O) _m CF ₂ CF ₂ C
OOH or CF ₃ [OCF (CF ₃ ) CF ₂ ] _j (OC
F ₂ ) _k COOH or the like can be used. In addition, m, j, k, in the structural formula in the said perfluoropolyether
p and q represent an integer of 1 or more.

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

Incidentally, in the perfluoropolyether having a carboxyl 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.

As the amine used in synthesizing the compound represented by Chemical formula 8, any of a primary amine, a secondary amine and a tertiary amine can be used, and a quaternary ammonium compound can also be used. it can. The structure of the amine to be used is also arbitrary, and can be arbitrarily selected regardless of the branched structure, isomer structure, alicyclic structure, molecular weight, and presence or absence of an unsaturated bond. However, the amine preferably has an alkyl group, and particularly when the amine has an alkyl group having 10 or more carbon atoms, the effect is large.

In the case where the amine is a quaternary ammonium compound, the compound of the perfluoropolyether having a carboxyl group at the terminal and the amine represented by the above formula (8) is a metal salt of perfluoropolyether (sodium salt). And the like, and a quaternary ammonium salt (chloride, iodide, sulfate, etc.) and extracting with an organic solvent.

The lubricant layer contains not only a compound of perfluoropolyether having a carboxyl group at a terminal at the terminal represented by Chemical formula 8 and an amine but also a combination of a conventionally known lubricant. It is.

The method for retaining the lubricant in the outermost layer is the same as that for the lubricant in the magnetic recording medium 1 described above. There is a method in which a lubricant paint obtained by dissolving a lubricant containing a compound with an amine in a solvent is applied on the adsorption layer.

The amount of the lubricant applied was 0.05 mg.
/ M ^{2 to} 100 mg / m ² , preferably 0.1 mg / m ^{2 to} 100 mg / m ² .
And more preferably ^{1mg / m 2 ~50mg / m 2} . If the amount of the lubricant applied is too small, the effects of lowering the friction coefficient and improving the wear resistance and durability may not be sufficiently exhibited. On the other hand, if the amount of lubricant applied is too large,
A shearing phenomenon occurs between the sliding member and the magnetic layer, and the running performance is rather deteriorated.

In the magnetic recording medium having the above-described structure, since the adsorption layer containing the aromatic carboxylic acid is formed between the protective film and the lubricant layer, the adhesion between the protective film and the lubricant layer is stable. The lubricity of the lubricant layer can be maintained well even after long-term storage. Further, since this magnetic recording medium is provided with a lubricant layer containing a compound of a perfluoropolyether having a carboxyl group at a terminal and an amine represented by Chemical Formula 8 as a lubricant, the lubricating property is extremely excellent and powder is dropped. Is prevented, good running properties and durability are obtained under any use conditions, and head wear and deterioration of magnetic properties are prevented.

Therefore, the magnetic material can exhibit good running properties and durability under any use conditions, prevent powder dropping, prevent output reduction and head wear, and maintain its effects for a long period of time. A recording medium is realized.

Further, in this magnetic recording medium, powder falling is prevented, and the adsorbing force of the lubricant is increased by interposing an adsorbing layer. Therefore, a protective film having a small surface energy, such as a CVD method, is used. The use of the formed carbon protective film becomes possible. Therefore, the magnetic recording medium to which the present invention is applied is most suitable for use in a helical scan magnetic recording / reproducing system using an MR head.

<Third Embodiment> Next, a third embodiment of the present invention will be described. The magnetic recording medium according to the present embodiment has a ferromagnetic metal thin film as a magnetic layer on a nonmagnetic support and a magnetic layer on a magnetic layer, similarly to the magnetic recording medium 1 of the first embodiment shown in FIG. A protective film, an adsorption layer containing an aromatic carboxylic acid on the protective film, and a lubricant layer containing a lubricant are sequentially formed on the adsorption layer. The magnetic recording medium according to the present embodiment uses a compound of a perfluoropolyether having a terminal carboxyl group and a diamine represented by the following chemical formula 9 as a lubricant used for the lubricant layer.

[0120]

Embedded image

As described above, the lubricant containing the compound represented by the above formula 9 has excellent lubricating properties and prevents powder from falling off.

The magnetic recording medium using the lubricant represented by the above chemical formula 9 has substantially the same configuration as the magnetic recording medium 1 shown in FIG. 1, and the lubricant held in the outermost layer Only different examples, other magnetic layers, protective films,
The adsorption layer and the like have the same configuration. Therefore, in the following description,
Only the lubricant will be described.

The compound of the perfluoropolyether having a carboxyl group at the terminal and the diamine represented by the above formula 9 is, for example, a mixture of the perfluoropolyether having a carboxyl group at the terminal and the diamine, and the melting point of the diamine used. It is synthesized by heating at a temperature higher than the temperature.

As the perfluoropolyether having a carboxyl group at the terminal used for synthesizing the compound represented by the above formula 9, any of commercially available products can be used.
For example, F (CF ₂ CF ₂ CF ₂ O) _m CF ₂ CF ₂ C
OOH or CF ₃ [OCF (CF ₃ ) CF ₂ ] _j (OC
F ₂ ) _k COOH or the like can be used. In addition, m, j, k, in the structural formula in the said perfluoropolyether
p and q represent an integer of 1 or more.

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 of the perfluoropolyether having a carboxyl group at the terminal is too large, the effect of the terminal group as an adsorbing group is diminished, and at the same time, the perfluoropolyether chain becomes large, so that it is difficult to dissolve in existing hydrocarbon solvents There is a risk of becoming. Conversely, if the molecular weight of the perfluoropolyether having a terminal carboxyl group is too small, the lubricating effect of the perfluoropolyether chain may be lost.

Incidentally, in this perfluoropolyether having a carboxyl 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.

The diamine used in synthesizing the compound represented by the chemical formula 9 may have any structure and the like, regardless of the branched structure, isomer structure, alicyclic structure, molecular weight, and presence or absence of an unsaturated bond. It can be arbitrarily selected.

The lubricant layer contains not only a compound of perfluoropolyether having a carboxyl group at a terminal at the terminal represented by Chemical formula 9 and a diamine but also a combination of a conventionally known lubricant. It is.

The method for retaining the lubricant in the outermost layer is the same as that for the lubricant in the magnetic recording medium 1 described above. There is a method in which a lubricant paint obtained by dissolving a lubricant containing a compound with a diamine in a solvent is applied on the adsorption layer.

Here, the amount of the lubricant applied is 0.05 mg.
/ M ^{2 to} 100 mg / m ² , preferably 0.1 mg / m ^{2 to} 100 mg / m ² .
And more preferably ^{1mg / m 2 ~50mg / m 2} . If the amount of the lubricant applied is too small, the effects of lowering the friction coefficient and improving the wear resistance and durability may not be sufficiently exhibited. On the other hand, if the amount of lubricant applied is too large,
A shearing phenomenon occurs between the sliding member and the magnetic layer, and the running performance is rather deteriorated.

In the magnetic recording medium having the above-described structure, since the adsorption layer containing the aromatic carboxylic acid is formed between the protective film and the lubricant layer, the adhesion between the protective film and the lubricant layer is stable. The lubricity of the lubricant layer can be maintained well even after long-term storage. Further, since this magnetic recording medium is provided with a lubricant layer containing a compound of a perfluoropolyether having a carboxyl group at a terminal represented by Chemical Formula 9 and a diamine as a lubricant, it has excellent lubricity and powder Is prevented, good running properties and durability are obtained under any use conditions, and head wear and deterioration of magnetic properties are prevented.

Therefore, the magnet exhibits good running properties and durability under any use conditions, prevents powder dropping, prevents output reduction and head wear, and can maintain those effects for a long period of time. A recording medium is realized.

In addition, since the magnetic recording medium is prevented from powder falling and has an increased adsorption force of the lubricant by interposing an adsorption layer, a protective film having a small surface energy, such as a CVD method, is used. The use of the formed carbon protective film becomes possible. Therefore, the magnetic recording medium to which the present invention is applied is most suitable for use in a helical scan magnetic recording / reproducing system using an MR head.

[0134]

EXAMPLES Specific examples to which the present invention is applied will be described below based on experimental results.

Experimental Example 1 In this experimental example, the effect of the adsorbing layer was confirmed when a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal represented by the above formula and an amine was used as a lubricant. .

[Preparation of Lubricant] First, a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal and an amine was synthesized as follows.

First, as a bifunctional perfluoropolyether having a terminal carboxyl group, H having a molecular weight of 4000 was used.
OOCCF ₂ (OC ₂ F ₄ ) _p (OCF ₂ ) _q OC
20 g of F ₂ COOH (where p and q each represent an integer of 1 or more) were placed in a round bottom flask, and 3.6 g of octadecylamine was added. Next, this was heated to 50 ° C. to dissolve it, sufficiently stirred and homogenized, and then cooled to obtain a perfluoropolyetheramine salt. The perfluoropolyetheramine salt obtained here is referred to as Compound 1.

Further, by a synthesis method similar to that of Compound 1 described above, a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal and an amine having a structure different from that of Compound 1 and an amine as shown in Table 1 were obtained. Four kinds of compounds having a fluoropolyether chain, an alkyl group, and a molecular weight were synthesized to obtain Compounds 2 to 5. Table 1
Wherein p and q each represent an integer of 1 or more.

[0139]

[Table 1]

[Preparation of Tape] A magnetic recording medium of a ferromagnetic metal thin film type having a lubricant layer containing a lubricant prepared as described above was prepared as follows.

First, Co was applied to a non-magnetic support on a film of polyethylene naphthalate having a thickness of 5.0 μm by oblique evaporation to form a magnetic layer having a thickness of 80 nm.
Was formed.

Next, a DC voltage of -1.2 kV was applied to the raw material of the magnetic recording medium using a high frequency plasma of a mixed gas of ethylene and argon as a counter electrode, and discharge was performed. A 15 nm carbon protective film was formed on the metal magnetic thin film.

Next, a 0.5 μm thick back coat layer containing carbon black and polyurethane resin was formed on the surface of the non-magnetic support opposite to the surface on which the metal magnetic thin film was formed.

Next, an adsorbent coating prepared by dissolving the aromatic carboxylic acids shown in Table 2 below in isopropyl alcohol was prepared. The coating amount of the aromatic carboxylic acids on the carbon protective film was shown in Table 2 below. The coating layer was applied so that the amount of application was such that an adsorbed layer was formed.

Next, a lubricant paint was prepared by dissolving the compounds shown in Table 2 in toluene as a lubricant, and the lubricant paint was applied so that the amount of the lubricant applied on the adsorption layer was 5 mg / m ^2. Was applied to form a lubricant layer, and 20 types of magnetic recording media were produced.

Finally, the obtained magnetic recording medium was filled with 6.35.
The resulting tape was cut into mm width to obtain tapes of Sample 1 to Sample 20.

However, the tapes of Sample 1, Sample 5, Sample 9, Sample 13 and Sample 17 did not form an adsorption layer.

The aromatic carboxylic acids and lubricants used in the tape are shown in Table 2 below.

[0149]

[Table 2]

The tapes of Samples 1 to 20 produced as described above were subjected to the following various measurements to evaluate the running property and durability.

These series of measurements were carried out under two different conditions, that is, environmental conditions of a temperature of 40 ° C. and a humidity of 30% and a temperature of -5 ° C.

<Measurement of Coefficient of Friction> The running property was evaluated by frictionally running the tape on a stainless steel guide pin for 100 passes in a thermostatic chamber controlled under the above-mentioned environmental conditions, and performing the friction coefficient at the 100th pass of the friction running. Was measured.

<Measurement of Shuttle Durability> The shuttle durability was evaluated in a constant temperature bath controlled under the above-mentioned environmental conditions.
Using a commercially available digital video camcorder (manufactured by Sony Corporation, model name: VX-1000), shuttle playback for each tape is repeated for 2 minutes each time, and the number of shuttles until the playback output is reduced by 3 dB from the initial output is measured. It was done by doing.

<Powder drop and wear of MR head>
In order to evaluate the durability, a commercially available digital video camcorder (manufactured by Sony Corporation, model name: VX-1000) was first modified in a thermostat controlled under the above-mentioned environmental conditions, and M
Using a recording / reproducing apparatus in which the R head was usable, reproduction for 30 minutes for each tape was repeated 50 times. Next, the MR head after repeated running was observed using an optical microscope, and the powder adhering to the MR head and the wear amount of the MR head were measured.

The level of powder erosion adhering to the MR head was evaluated on a four-point scale. The level at which powder erosion was hardly observed was rated as ◎. The level at which powder dropping was 50% or less of the head area and affected the output was rated as Δ, and the level at which powder dropping exceeded 50% of the head area or at which clogs occurred during running was rated as x.

As the wear amount of the MR head, a difference between the height of the initial MR head and the height of the MR head after repeating reproduction for 30 minutes 50 times was measured as the wear amount of the MR head.

These evaluations were performed on the tape immediately after completion and on the tape after storage for 30 days in an environment of a temperature of 45 ° C. and a humidity of 80%. Table 3 shows the measurement results of the running property, durability, dusting, and head wear of the tape immediately after completion, and the running property, durability, dusting, and head wear of the tape after storage for 30 days. Table 4 shows the measurement results of the amounts.

[0158]

[Table 3]

[0159]

[Table 4]

From Table 3, regarding the tape immediately after completion,
Regardless of the presence or absence of an adsorption layer, the type of aromatic carboxylic acid, the amount of aromatic carboxylic acid applied, and the amount of lubricant applied, the coefficient of friction is small under various operating conditions such as high temperature, low humidity or low temperature, and shuttle durability. And good results were obtained in which powder fall was prevented and head wear was small.

By the way, from the results in Table 4, even after long-term storage, Samples 2 to 4 having an adsorption layer
Sample 6 to Sample 8, Sample 10 to Sample 1
2, sample 14 to sample 16, and sample 18 to
Under the various use conditions such as high temperature and low humidity or low temperature, the sample 20 provided good results such as a low coefficient of friction, good shuttle durability, prevention of powder falling, and little head abrasion.

However, Sample 1, Sample 5, Sample 9, Sample 13 and Sample 17, which are not provided with an adsorbent layer, have deteriorated coefficient of friction and shuttle durability under any use conditions, and do not prevent powder dropping. And the MR head was abraded greatly, and good results could not be obtained.

From the above, it can be seen that the provision of the adsorption layer improves the adhesion stability between the protective film and the lubricant layer.
Even when stored for a long period of time, it is possible to obtain a magnetic recording medium that maintains excellent effects of a compound of a bifunctional perfluoropolyether having a terminal carboxyl group and an amine represented by Chemical Formula 7 as a lubricant and an amine. I understood.

When, for example, phthalic acid is used as the aromatic carboxylic acid and Compound 1 is used as the lubricant, Samples 3 and 4 in which the applied amount of phthalic acid is equal to or larger than the applied amount of the lubricant are phthalic acid. Compared with Sample 2 in which the amount of the applied acid was less than the amount of the applied lubricant, the friction coefficient and the wear amount of the MR head were significantly reduced.

In Table 4, samples 5 to 20
From the results, even if the type of the aromatic carboxylic acid and the type of the lubricant are different, similarly to the results of Samples 1 to 4, the tape in which the coating amount of the aromatic carboxylic acid is equal to or larger than the coating amount of the lubricant is It was found that the results showed excellent results as compared with a tape in which the amount of the aromatic carboxylic acid applied was less than the amount of the lubricant applied.

From these facts, in particular, when the coating amount of the aromatic carboxylic acid is equal to or more than the coating amount of the lubricant, the adhesion stability between the protective film and the lubricant layer is further improved. Even if it did, it was found that the friction coefficient and the wear amount of the MR head could be significantly reduced.

Experimental Example 2 In this experimental example, the effect of the adsorption layer was confirmed when a compound of perfluoropolyether having a terminal carboxyl group and an amine was used as the lubricant represented by Chemical formula 8 above.

[Preparation of Lubricant] First, a compound of a perfluoropolyether having a carboxyl group at a terminal and an amine was synthesized as follows.

First, as a perfluoropolyether having a terminal carboxyl group, F (C
_{F 2 CF 2 CF 2 O)} m CF 2 CF 2 COOH ( provided that, m takes.) 20 g which represents an integer of 1 or more to a round bottom flask was added octadecylamine 3.2 g. Next, this was heated to 50 ° C. to dissolve it, sufficiently stirred and homogenized, and then cooled to obtain a perfluoropolyetheramine salt. The perfluoropolyetheramine salt obtained here is referred to as Compound 6.

Further, by a synthesis method similar to that of the above-mentioned compound 6, a compound of a perfluoropolyether having a structure different from that of the compound 6 and having a carboxyl group at a terminal and an amine is prepared as shown in Table 5 Four kinds of compounds having an ether chain, an alkyl group and a molecular weight were synthesized to obtain Compounds 7 to 10. In Table 5,
j, k, and m each represent an integer of 1 or more.

[0171]

[Table 5]

[Preparation of Tape] First, a ferromagnetic metal thin film serving as a magnetic layer and a protective film made of carbon were formed on a nonmagnetic support by a plasma CVD method in the same manner as in Experimental Example 1 described above. A layer was also formed.

Next, in the same manner as in Experimental Example 1 described above, an adsorbing layer paint was prepared by dissolving an aromatic carboxylic acid shown in Table 6 below in isopropyl alcohol on the surface of the protective film. An adsorption layer was formed by applying the adsorption layer paint such that the application amount of the aromatic carboxylic acid became the application amount shown in Table 6 below on the film.

Next, a lubricant paint was prepared by dissolving the compounds shown in Table 6 in toluene as a lubricant, and the lubricant paint was applied on the adsorption layer so that the amount of the lubricant applied was 5 mg / m ^2. Was applied to form a lubricant layer, and 20 types of magnetic recording media were produced.

Finally, the obtained magnetic recording medium was filled with 6.35.
The resulting tape was cut into mm width to obtain tapes of Samples 21 to 40.

However, the tapes of Sample 21, Sample 25, Sample 29, Sample 33 and Sample 37 did not form an adsorption layer.

The aromatic carboxylic acids and lubricants used in the tape are shown in Table 6 below.

[0178]

[Table 6]

The samples 21 to 21 produced as described above
For the tape of the sample 40, the friction coefficient was measured under two different conditions, that is, the environmental conditions of a temperature of 40 ° C. and a humidity of 30% and a temperature of −5 ° C. as in the experimental example 1 described above. Durability measurement, powder drop and MR
The amount of head wear was measured.

These evaluations were carried out in the same manner as in Experimental Example 1 above, except that the tape immediately after completion was compared with a tape at 45 ° C. and 80% humidity.
And after the tape was stored for 30 days in the environment described above. Tables 7 and 30 show the measurement results of the runnability, durability, powder fall, and head wear of the tape immediately after completion.
Table 8 shows the measurement results of the running property, durability, powder dropout, and head wear of the tape after storage for a period of days.

[0181]

[Table 7]

[0182]

[Table 8]

From Table 7, regarding the tape immediately after completion,
Regardless of the presence or absence of an adsorption layer, the type of aromatic carboxylic acid, the amount of aromatic carboxylic acid applied, and the amount of lubricant applied, the coefficient of friction is small under various operating conditions such as high temperature, low humidity or low temperature, and shuttle durability. And good results were obtained in which powder fall was prevented and head wear was small.

Incidentally, from the results shown in Table 8, even after long-term storage, Samples 22 to 2 having an adsorption layer
4. Samples 26 to 28, Samples 30 to 32, Samples 34 to 36, and Samples 38 to 40 have a low coefficient of friction and a low shuttle durability under various use conditions such as high temperature and low humidity or low temperature. Good results were obtained, that is, powder dropping was prevented and head wear was small.

However, Sample 21, Sample 25, Sample 29, Sample 33, and Sample 37, which are not provided with an adsorbent layer, have deteriorated friction coefficient and shuttle durability under any use condition, and powder drop is not prevented. , M
The abrasion of the R head was large, and good results could not be obtained.

From the above, it can be seen that the provision of the adsorption layer improves the adhesion stability between the protective film and the lubricant layer.
It has been found that even when stored for a long period of time, it is possible to obtain a magnetic recording medium that maintains excellent effects of a perfluoropolyether having a terminal carboxyl group and an amine represented by Chemical Formula 8 as a lubricant.

By the way, for example, when phthalic acid is used as the aromatic carboxylic acid and Compound 6 is used as the lubricant, Samples 23 and 24 in which the applied amount of phthalic acid is equal to or more than the applied amount of the lubricant are phthalic acid. Compared with Sample 22 in which the amount of the applied acid was less than the amount of the applied lubricant, the friction coefficient and the wear amount of the MR head were significantly reduced.

In Table 8, Sample 25 to Sample 4
From the result of No. 0, even when the type of the aromatic carboxylic acid and the type of the lubricant are different, the tape in which the coating amount of the aromatic carboxylic acid is equal to or more than the coating amount of the lubricant as in the results of Samples 21 to 24. Was found to show excellent results as compared with a tape in which the amount of the aromatic carboxylic acid applied was less than the amount of the lubricant applied.

From these facts, in particular, when the coating amount of the aromatic carboxylic acid is equal to or more than the coating amount of the lubricant, the adhesion stability between the protective film and the lubricant layer is further improved. Even if it did, it was found that the friction coefficient and the wear amount of the MR head could be significantly reduced.

Experimental Example 3 In this experimental example, the effect of the adsorbing layer was confirmed when a compound of perfluoropolyether having a terminal carboxyl group and a diamine was used as the lubricant represented by the above formula (9).

[Preparation of Lubricant] First, a compound of a perfluoropolyether having a carboxyl group at a terminal and a diamine was synthesized as follows.

First, as a perfluoropolyether having a carboxyl group at a terminal, F (C
_{F 2 CF 2 CF 2 O)} m CF 2 CF 2 COOH ( provided that, m takes.) 20 g which represents an integer of 1 or more to a round bottom flask was added 1,4-diaminobutane 0.52 g.
Next, this was heated to 50 ° C. to dissolve it, sufficiently stirred and homogenized, and then cooled to obtain a perfluoropolyetherdiamine salt. The perfluoropolyether diamine salt obtained here is referred to as Compound 11.

Further, by a synthesis method similar to that of the above-mentioned compound 11, a compound of a perfluoropolyether having a structure different from that of the compound 11 and having a carboxyl group at a terminal and a diamine is a perfluoropolyether as shown in Table 9 Four kinds of compounds having an ether chain, an alkyl group and a molecular weight were synthesized to obtain Compounds 12 to 15. In Table 5, j, k, and m each represent an integer of 1 or more.

[0194]

[Table 9]

[Preparation of Tape] First, a ferromagnetic metal thin film serving as a magnetic layer and a protective film made of carbon were formed on a nonmagnetic support by a plasma CVD method in the same manner as in Experimental Example 1 described above. A layer was also formed.

Next, in the same manner as in Experimental Example 1 described above, an adsorbing layer paint was prepared by dissolving an aromatic carboxylic acid shown in Table 10 below in isopropyl alcohol on the surface of the protective film. An adsorption layer was formed by applying the adsorption layer paint such that the application amount of the aromatic carboxylic acid became the application amount shown in Table 10 below on the film.

Next, a lubricant paint was prepared by dissolving the compounds shown in Table 10 in toluene as a lubricant, and the lubricant paint was prepared such that the amount of the lubricant applied on the adsorption layer was 5 mg / m ^2. To form a lubricant layer,
Various kinds of magnetic recording media were produced.

Lastly, the obtained magnetic recording medium was filled with 6.35.
The tape was cut into mm width to obtain tapes of Samples 41 to 60.

However, for the tapes of Sample 41, Sample 45, Sample 49, Sample 53 and Sample 57, no adsorption layer was formed.

The aromatic carboxylic acids and lubricants used in the tape are shown in Table 10 below.

[0201]

[Table 10]

Samples 41 to 41 produced as described above
For the tape of the sample 60, the friction coefficient was measured under two different conditions, that is, a condition of a temperature of 40 ° C. and a humidity of 30% and a condition of a temperature of −5 ° C. as in the experimental example 1 described above. Durability measurement, powder drop and MR
The amount of head wear was measured.

These evaluations were made on the tape immediately after completion in the same manner as in the above-mentioned Experimental Example 1 and at a temperature of 45 ° C. and a humidity of 80%.
And after the tape was stored for 30 days in the environment described above. Tables 11 and 3 show the measurement results of the runnability, durability, powder fall, and head wear of the tape immediately after completion.
After storage for 0 days, the tape's runnability, durability,
Table 12 shows the measurement results of the powder drop and the head wear amount.

[0204]

[Table 11]

[0205]

[Table 12]

From Table 11, it can be seen that the tape immediately after completion has various properties such as high and low humidity or low temperature regardless of the presence or absence of an adsorption layer, the type of aromatic carboxylic acid, the amount of aromatic carboxylic acid applied, and the amount of lubricant applied. Under good use conditions, good results were obtained in which the coefficient of friction was small, the shuttle durability was good, powder drop was prevented, and head wear was small.

By the way, from the results in Table 12, even after long-term storage, Samples 42 to 44, Samples 46 to 48, Samples 50 to 52, Samples 54 to 56, and Samples having an adsorption layer were obtained. Under various use conditions such as high temperature and low humidity or low temperature, samples 58 to 60 exhibited good results in that the coefficient of friction was small, the shuttle durability was good, powder falling was prevented, and head wear was small. .

However, in Samples 41, 45, 49, 53 and 57 having no adsorbent layer, the friction coefficient and shuttle durability deteriorated under any use conditions, and powder dropping was not prevented. , M
The abrasion of the R head was large, and good results could not be obtained.

From the above, it can be seen that the provision of the adsorption layer improves the adhesion stability between the protective film and the lubricant layer.
It has been found that even when stored for a long period of time, it is possible to obtain a magnetic recording medium that maintains the excellent effects of the perfluoropolyether having a carboxyl group at the terminal represented by Chemical Formula 9 and the diamine even when stored.

By the way, for example, when phthalic acid is used as the aromatic carboxylic acid and Compound 11 is used as the lubricant, the samples 43 and 44 in which the applied amount of phthalic acid is equal to or more than the applied amount of the lubricant are phthalic acid. Compared with the sample 42 in which the amount of the applied acid is less than the amount of the applied lubricant, the friction coefficient and the wear amount of the MR head were significantly reduced.

In Table 12, from the results of Samples 45 to 60, even if the type of the aromatic carboxylic acid and the type of the lubricant were different, the results were the same as those of Samples 41 to 44. It was found that a tape having a coating amount of the lubricant of not less than the coating amount of the lubricant showed excellent results as compared with a tape having a coating amount of the aromatic carboxylic acid less than the coating amount of the lubricant.

From these facts, especially when the amount of the aromatic carboxylic acid applied is equal to or more than the amount of the lubricant applied, the adhesion stability between the protective film and the lubricant layer is further improved, and after long-term storage, Even if it did, it was found that the friction coefficient and the wear amount of the MR head could be significantly reduced.

[0213]

As is clear from the above description, the magnetic recording medium according to the present invention has an adsorbing layer containing an aromatic carboxylic acid between the protective film and the lubricant layer. The stability of adhesion to the lubricant layer is improved. Furthermore, the magnetic recording medium according to the present invention uses a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal represented by the above formula (7) and an amine as a lubricant, and thus has excellent lubricity, The occurrence of powder drop is prevented. Therefore, according to the present invention, good running properties and durability are exhibited under any use conditions, and head wear and deterioration of magnetic properties are prevented, and their effects are maintained even after long-term storage. It is possible to provide a magnetic recording medium that can be maintained. In particular, this magnetic recording medium is suitable for use in a helical scan magnetic recording / reproducing system using a magnetoresistive read head.

Further, since the magnetic recording medium according to the present invention has an adsorption layer containing an aromatic carboxylic acid between the protective film and the lubricant layer, the adhesion stability between the protective film and the lubricant layer is improved. I do. Furthermore, since the magnetic recording medium according to the present invention uses a compound of a perfluoropolyether having a carboxyl group at a terminal and an amine represented by the above formula (8) as a lubricant, it has excellent lubricity, Is prevented from occurring. Therefore, according to the present invention, it shows good running performance and durability under any use conditions,
In addition, it is possible to provide a magnetic recording medium in which head wear and deterioration of magnetic characteristics are prevented, and the effects can be maintained even after long-term storage. In particular, this magnetic recording medium is suitable for use in a helical scan magnetic recording / reproducing system using a magnetoresistive read head.

Further, since the magnetic recording medium according to the present invention has an adsorption layer containing an aromatic carboxylic acid between the protective film and the lubricant layer, the adhesion stability between the protective film and the lubricant layer is improved. I do. Further, since the magnetic recording medium according to the present invention uses a compound of a perfluoropolyether having a carboxyl group at a terminal represented by the above formula (9) and a diamine as a lubricant, it has excellent lubricity and powder Is prevented from occurring. Therefore, according to the present invention, good running properties and durability are exhibited under any use conditions, and head wear and deterioration of magnetic properties are prevented, and their effects are maintained even after long-term storage. It is possible to provide a magnetic recording medium that can be maintained. In particular, the magnetic recording medium is suitable for use in a helical scan magnetic recording / reproducing system using a magnetoresistive read head.

[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 sectional view showing a conventional magnetic recording medium.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Magnetic recording medium, 2 Non-magnetic support, 3 Magnetic layer, 4 Protective film, 5 Adsorption layer, 6 Lubricant layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C10N 30:00 C10N 30:00 Z 40:18 40:18 (72) Inventor Hiroshi Yatakai Shinagawa, Tokyo 6-7-35 Kita-Shinagawa, Ward Sony Corporation F-term (reference) 4H104 BB22A BB23A BB24A BD06A CD04A LA20 PA16 5D006 AA01 AA02 AA06 EA03 FA02 FA05

Claims (12)

[Claims] 1. A magnetic layer comprising a ferromagnetic metal material, a protective film, a bifunctional perfluoropolyether having a carboxyl group at a terminal represented by the following formula 1, and an amine on a nonmagnetic support. And a lubricant layer containing a compound of the formula (1), a magnetic recording medium used in a helical scan magnetic recording / reproducing system using a magnetoresistive read head, wherein an aromatic compound is provided between the protective film and the lubricant layer. A magnetic recording medium comprising an adsorption layer containing a carboxylic acid. Embedded image 2. The magnetic recording medium according to claim 1, wherein the amount of the aromatic carboxylic acid applied to the adsorption layer is larger than the amount of the lubricant applied to the lubricant layer. 3. The magnetic recording medium according to claim 1, wherein said protective film is made of carbon. 4. The magnetic recording medium according to claim 1, wherein said protective film is formed by a chemical vapor deposition method. 5. A magnetic layer comprising a ferromagnetic metal material, a protective film, and a compound of a perfluoropolyether having a carboxyl group at a terminal and an amine represented by the following formula (2) as a lubricant on a nonmagnetic support: And a lubricant layer containing: a magnetic recording medium used in a helical scan magnetic recording / reproducing system using a magnetoresistive read head, wherein an aromatic carboxylic acid is provided between the protective film and the lubricant layer. A magnetic recording medium comprising an adsorption layer containing: Embedded image 6. The magnetic recording medium according to claim 5, wherein the amount of the aromatic carboxylic acid applied to the adsorption layer is larger than the amount of the lubricant applied to the lubricant layer. 7. The magnetic recording medium according to claim 5, wherein said protective film is made of carbon. 8. The magnetic recording medium according to claim 5, wherein said protective film is formed by a chemical vapor deposition method. 9. A compound comprising a magnetic layer comprising a ferromagnetic metal material, a protective film, and a perfluoropolyether having a terminal carboxyl group represented by the following formula (3) and a diamine as a lubricant on a nonmagnetic support: And a lubricant layer containing: a magnetic recording medium used in a helical scan magnetic recording / reproducing system using a magnetoresistive read head, wherein an aromatic carboxylic acid is provided between the protective film and the lubricant layer. A magnetic recording medium comprising an adsorption layer containing: Embedded image 10. The magnetic recording medium according to claim 9, wherein the amount of the aromatic carboxylic acid applied to the adsorption layer is larger than the amount of the lubricant applied to the lubricant layer. 11. The magnetic recording medium according to claim 9, wherein said protective film is made of carbon. 12. The magnetic recording medium according to claim 9, wherein said protective film is formed by a chemical vapor deposition method.