JPH11353640A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an excellent traveling property and durability by holding a lubricant mixture composed of a compd. of bifunctional perfluoropolyether having a carboxyl group at a terminal of a relatively large mol.wt. and amine and perfuoroalkyl carboxylate deriv. of a relatively small mol.wt. on the outermost layer. SOLUTION: The lubricant contg. the compd. of the bifunctional perfluoropolyether having the carboxyl group at the terminal expressed by formula I and the amine, and the perfluoroalkyl carboxylate deriv. expressed by formula II is used. In the formula I, Rf1 denotes a perfluoropolyether chain and R1 to R4 respectively denote hydrogen or hydrocarbon groups. In the formula II, R denotes 7-21C alkyl group; (m), (n) denote an integer of m+m>=8. A magnetic layer 2 is formed on a nonmagnetic base 1 and the lubricant is held in a protective film 3 which is the outermost layer and consists of SiO2 , silicon nitride, carbon nitride, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic recording medium having at least a magnetic layer formed on a non-magnetic support. Specifically, the lubricant held in the outermost layer is defined,
The present invention relates to a magnetic recording medium that ensures excellent running properties and durability.

[0002]

2. Description of the Related Art Conventionally, magnetic recording media include ferromagnetic powders such as oxide magnetic powders and alloy magnetic powders and binders such as vinyl chloride-vinyl acetate copolymers, polyester resins, urethane resins and polyurethane resins. A so-called coating type magnetic recording medium in which a magnetic layer is formed by applying a magnetic paint composed of an organic solvent on a non-magnetic support, 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).

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, Since the thickness loss at the time of recording demagnetization and reproduction is extremely small, and there is no need to mix a binder, which is a nonmagnetic material, in the magnetic layer, it is possible to increase the packing density of the magnetic material. Has advantages.

[0005] In general, a magnetic recording medium records and records magnetic signals.
During the reproduction process, the head must be moved under a high-speed relative motion with the magnetic head, and the running must be performed smoothly and stably. Also, it is better that the wear and damage due to contact with the magnetic head be as small as possible.

However, in the above-described ferromagnetic metal thin film type magnetic recording medium, the surface of the magnetic layer is extremely smooth, so that a substantial contact area is increased and an adhesion phenomenon (so-called chipping) occurs. There are many drawbacks in durability, running properties, etc., such as ease of use and increase in the coefficient of friction.

Therefore, for example, attempts have been made to improve durability and running properties by applying a lubricant to the surface of the magnetic layer of the magnetic recording medium, that is, the surface of the ferromagnetic metal thin film. It is known that an organic fluorine compound is effective as a lubricant used in such an application. In particular, JP-A-05-93
No. 059 discloses an excellent lubrication under any use conditions by using a compound of a perfluoropolyether and an amine having a terminal carboxyl group or a compound of a perfluoropolyether and a diamine having a terminal carboxyl group as a lubricant. A magnetic recording medium exhibiting an effect is disclosed.

[0008]

By the way, in the magnetic recording medium of the ferromagnetic metal thin film type, a technique for forming a carbon protective film on the ferromagnetic metal thin film has been established in order to secure more excellent durability. Have been. In the above-described ferromagnetic metal thin film type magnetic recording medium used for the DV tape which is a consumer video format, the DVCAM tape which is a business video format, and the AIT tape which is a tape streamer application, A technique for forming a carbon protective film on a ferromagnetic metal thin film has been put to practical use. Practical use of the carbon protective film has ensured sufficient durability, and it is considered that the presence of the carbon protective film will be indispensable in future ferromagnetic metal thin film type magnetic recording media.

However, as described above, when an attempt is made to use a lubricant in order to improve durability and running properties, the energy on the surface of the carbon protective film is smaller than that of a ferromagnetic metal thin film, and the lubricant and carbon Since the adsorptivity with the protective film is weak, it is necessary to design a lubricant in consideration of the presence of the carbon protective film. In particular, the above-mentioned compound of perfluoropolyether having a carboxyl group at the end and an amine or the compound of perfluoropolyether having a carboxyl group at the end and a diamine has a large molecular weight, and these lubricants alone can be used uniformly on the carbon protective film. It is difficult to make the lubricant exist in the oil.

Accordingly, the present invention has been proposed in view of the above-mentioned conventional circumstances, and is particularly suitable for a ferromagnetic metal thin film type magnetic recording medium having a carbon protective film formed thereon. Provide a lubricant that maintains the lubricity and lubricity and maintains the lubrication effect for a long time,
An object of the present invention is to provide a magnetic recording medium having excellent durability.

[0011]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have conducted intensive studies and have found that a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal having a relatively large molecular weight and an amine compound. It has been found that a mixture with a perfluoroalkyl ester derivative of a carboxylic acid having a relatively small molecular weight is a suitable lubricant for a ferromagnetic metal thin film type magnetic recording medium having a carbon protective film.

The present inventors have conducted intensive studies and found that a compound of a perfluoropolyether having a carboxyl group at a terminal having a relatively large molecular weight and an amine, a perfluoroalkyl ester derivative of a carboxylic acid having a relatively small molecular weight, and a perfluoroalkyl ester derivative having a relatively small molecular weight. Have been found to be suitable lubricants for ferromagnetic metal thin film type magnetic recording media having a carbon protective film.

Further, the present inventors have conducted intensive studies and as a result,
A mixture of a compound of a perfluoropolyether having a carboxyl group at a terminal with a relatively high molecular weight and a diamine and a perfluoroalkyl ester derivative of a carboxylic acid with a relatively low molecular weight is a ferromagnetic metal thin film type magnetic recording having a carbon protective film. It has been found that it is a suitable lubricant for the medium.

That is, the magnetic recording medium of the present invention comprises at least a magnetic layer formed on a non-magnetic support, and the outermost layer has a bifunctional perfluoropolyimide having a carboxyl group at a terminal represented by the following formula (7). A lubricant containing an ether-amine compound and a carboxylic acid perfluoroalkyl ester derivative represented by the following formula (8) is retained.

[0015]

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[0016]

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In the magnetic recording medium of the present invention, the mixing ratio of the compound of the bifunctional perfluoropolyether having a carboxyl group at the terminal with the amine and the perfluoroalkyl ester derivative of the carboxylic acid is 10% by weight. : 90 to 90:10.

Further, the magnetic recording medium of the present invention comprises a non-magnetic support having at least a magnetic layer formed thereon, the outermost layer comprising a perfluoropolyether having a terminal carboxyl group represented by the following formula (9): A lubricant containing an amine compound and a carboxylic acid perfluoroalkyl ester derivative represented by the following formula (10) is retained in the outermost layer.

[0019]

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[0020]

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In the magnetic recording medium of the present invention, the mixing ratio of the compound of the perfluoropolyether having a carboxyl group at the terminal and the amine and the perfluoroalkyl ester derivative of the carboxylic acid is 1% by weight.
The ratio is preferably from 0:90 to 90:10.

Furthermore, the magnetic recording medium of the present invention comprises at least a magnetic layer formed on a non-magnetic support, and the outermost layer comprises a perfluoropolyether having a terminal carboxyl group represented by the following formula A lubricant containing a diamine compound and a carboxylic acid perfluoroalkyl ester derivative represented by the following formula (12) is retained in the outermost layer.

[0023]

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[0024]

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In the magnetic recording medium of the present invention, the mixing ratio of the compound of the perfluoropolyether having a carboxyl group at the terminal and the diamine and the perfluoroalkyl ester derivative of the carboxylic acid is 1% by weight.
The ratio is preferably from 0:90 to 90:10.

Further, in these magnetic recording media of the present invention, it is preferable that the magnetic layer is made of a ferromagnetic metal thin film.

Further, in these magnetic recording media of the present invention, it is preferable that a protective film is formed as an outermost layer on the magnetic layer, and the protective film is made of carbon.

The magnetic recording medium of the present invention comprises a non-magnetic support having at least a magnetic layer formed thereon.
A lubricant containing a compound of a bifunctional perfluoropolyether having a terminal carboxyl group and an amine and a perfluoroalkyl ester derivative of a carboxylic acid, or a compound of a perfluoropolyether having a terminal carboxyl group and an amine and a perfluorocarboxylic acid A lubricant containing an alkyl ester derivative, or a lubricant containing a compound of a perfluoropolyether having a carboxyl group at the end and a diamine and a perfluoroalkyl ester derivative of a carboxylic acid is retained. Since the adhesiveness and lubricity are maintained under any use conditions and the lubricating effect is maintained for a long period of time, good running properties and durability of the magnetic recording medium are ensured.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

The magnetic recording medium according to the present invention is a magnetic recording medium in which at least a magnetic layer is formed on a non-magnetic support. However, here, as shown in FIG. 1, a ferromagnetic metal thin film is formed as a magnetic layer 2 on a nonmagnetic support 1, and a protective film 3 is formed as an outermost layer on the magnetic layer 2. The recording medium will be described.

The magnetic recording medium of the present embodiment has a ferromagnetic metal thin film formed as a magnetic layer 2 on a non-magnetic support 1. Here, the material of the non-magnetic support 1 is polyethylene terephthalate, polyethylene Polyesters such as naphthalate, polyethylene, polyolefins such as polypropylene, cellulose triacetate, cellulose derivatives such as cellulose diacetate, polyvinyl chloride,
Examples thereof include vinyl resins such as polyvinylidene chloride, plastics such as polycarbonate, polyimide, polyamide, and polyamideimide; light metals such as aluminum alloys and titanium alloys; and ceramics such as glass. The form of the nonmagnetic support 1 may be any of a film, a sheet, a disk, a card, a drum, and the like.

The non-magnetic support 1 may be one in which at least one kind of protrusion such as a mountain-like protrusion, a wrinkle-like protrusion, or a granular protrusion is formed on the surface, and the surface roughness is controlled.

The mountain-like projections are formed, for example, by adding inorganic fine particles having a particle size of about 50 to 300 (nm) at the time of forming the polymer film, and have a height from the polymer film surface of 10 to 100 (nm). nm), the density is approximately 1 × 10
⁴ to 1 × 10 ⁵ (pieces / mm ² ). Calcium carbonate, silica, alumina, and the like are preferable as the inorganic fine particles used to form the mountain-like projections.

The wrinkle-like projections are projections formed by, for example, applying and drying a dilute solution of a resin using a specific mixed solvent, and have a height of 0.01 to 10 (μm).
m), preferably 0.03 to 0.5 (μm), and the shortest interval between the projections is 0.1 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, polyvinyl butyral, and polyphenylene. It is a simple substance, a mixture, or a copolymer of an oxide, a phenoxy resin, or the like, and those having a soluble solvent are suitable. And the resin concentration which dissolved these resins in the good solvent 1-1000 (ppm)
The solution of a poor solvent of the resin, a solvent having a boiling point higher than the good solvent is added 10 to 100 times the amount of the resin, by applying and drying the surface of the polymer film, A thin film having very fine wrinkle-like irregularities can be formed.

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

If at least one of these projections is formed, the surface property of the ferromagnetic metal thin film as the magnetic layer is controlled, but the effect is increased by combining two or more of them.
In particular, if the wrinkle-like protrusions and the granular protrusions are formed on the nonmagnetic support 1 provided with the mountain-like protrusions, the durability and running properties are extremely improved.

In this case, the overall height of the projection is 1
The density is preferably in the range of 0 to 200 (nm), and the density is preferably 1 × 10 ⁵ to 1 × 10 ⁷ (pieces / mm ² ).

The ferromagnetic metal thin film serving as the magnetic layer 2 may be made of a metal such as Fe, Co, Ni, etc.
i alloy, Co-Pt alloy, Co-Ni-Pt alloy, Fe
-Co alloy, Fe-Ni alloy, Fe-Co-Ni alloy,
Fe-Co-B alloy, Co-Ni-Fe-B alloy, Co
-Cr alloy or a ferromagnetic metal material containing a metal such as Cr, Al or the like. In particular, when a Co—Cr alloy is used, a perpendicular magnetization film is formed.

The ferromagnetic metal thin film as the magnetic layer 2 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 a range of 1 × 10 ⁻² to 1 × 10 ^−6.
A ferromagnetic metal material is evaporated under a vacuum of (Pa) by resistance heating, high-frequency heating, electron beam heating, etc., and an evaporated metal (ferromagnetic metal material) is deposited on a non-magnetic support. In order to obtain a magnetic force, oblique evaporation in which the ferromagnetic metal material is obliquely evaporated on the non-magnetic support 1 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 vacuum evaporation method, and causes DC glow discharge and RF glow discharge in an inert gas atmosphere of 1 × 10 ^-2 to 1 × 10 ^-1 (Pa). This is to evaporate the magnetic metal material during discharge.

The above sputtering method is performed in the range of 1 × 10 ⁻¹ to 1
Glow discharge is caused in an atmosphere containing argon gas as a main component at 10 × 10 Pa, and atoms of the target surface are knocked out by the generated argon gas ions. Method, a high-frequency sputtering method, a magnetron sputtering method using magnetron discharge, and the like. In the case of using this sputtering method, a base film such as Cr, W, and V may be formed.

In any of the above methods, Bi, Sb, Pb, Sn, Ga, In, C
By depositing a base metal layer of d, Ge, Si, Tl, etc. in advance and forming the film in a direction perpendicular to the surface of the nonmagnetic support 1, there is no orientation of magnetic anisotropy, A magnetic layer having excellent anisotropy can be formed, which is suitable for, for example, a magnetic disk.

The thickness of the ferromagnetic metal thin film formed by such a method is preferably 0.01 to 1 (μm).

The protective film 3 formed on the ferromagnetic metal thin film serving as the magnetic layer 2 is preferably made of carbon, particularly preferably diamond-like carbon having relatively high hardness. Examples of the protective film 3 include those made of SiO ₂ , silicon nitride, carbon nitride, ZrO ₂ , TiC, Al ₂ O _{3 and the} like.

Then, in the magnetic recording medium of this embodiment,
In particular, the protective film 3 serving as the outermost layer contains a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal and an amine represented by the following formula (13) and a perfluoroalkyl ester derivative of a carboxylic acid represented by the following formula (14). Lubricant is retained.

[0048]

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[0049]

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The compound of amine and a bifunctional perfluoropolyether having a carboxyl group at the terminal represented by Chemical formula 13 can be easily synthesized by the following method. For example, it can be synthesized by mixing a bifunctional perfluoropolyether and an amine and heating the mixture at a temperature equal to or higher than the melting point of the amine used. When stearylamine is used as the amine, for example, the mixture may be heated and mixed at 60 (° C.).

Further, it can also be obtained by dissolving both in an organic solvent and then removing the solvent. When the amine is a quaternary ammonium compound, a metal salt of perfluoropolyether (such as sodium salt) and a quaternary ammonium salt (such as chloride, iodide, sulfate, etc.) are mixed and extracted with an organic solvent. Obtainable.

As the bifunctional perfluoropolyether having a carboxyl group at the terminal, a commercially available product can be used, and HOOCCF ₂ (OCF ₂ CF) can be used.
₂ ) _p (OCF ₂ ) _q OCF ₂ COOH. The above-mentioned bifunctional perfluoropolyether having a terminal carboxyl group is, of course, not limited to these. In the above perfluoropolyether chemical formula, p and q each 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 5000, more preferably 1000 to 4000. . 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 diminished.

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.

One of the amines is a primary amine or a secondary amine.
Both amines and tertiary amines can be used, and quaternary ammonium compounds can also be used. 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.

Further, the above-mentioned chemical formula 14 contained in the above-mentioned lubricant is used.
Can be easily synthesized by reacting a partially fluorinated alcohol with a saturated fatty acid in substantially equimolar amounts. The number of carbon atoms of R in the carboxylic acid perfluoroalkyl ester derivative shown in Chemical formula 14 is 7 to 21.
It is preferred that When the number of carbon atoms is 6 or less, the lubricating effect is poor, and when the number of carbon atoms exceeds 21, the solubility in an organic solvent decreases. There is no particular limitation on m and n in the above formula 14, as long as m + n ≧ 8 is satisfied.

A specific reaction formula for synthesizing the perfluoroalkyl carboxylate derivative is as shown below. First, a partially fluorinated alcohol is synthesized as shown in Chemical formula 15.

[0058]

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Next, a partially fluorinated alcohol and a saturated fatty acid may be synthesized as shown in Chemical formula 16 to synthesize a carboxylic acid perfluoroalkyl ester derivative.

[0060]

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What is important here is that the carboxylic acid moiety of the perfluoroalkyl ester derivative of carboxylic acid is selected from an alkyl group containing no unsaturated bond. The ester derivative containing no unsaturated bond can maintain the initial lubricating properties even during long-term storage.

Further, in the lubricant used in the magnetic recording medium of the present example, the mixing ratio of the compound of the bifunctional perfluoropolyether having a carboxyl group at the terminal with the amine and the perfluoroalkyl ester derivative of the carboxylic acid is as follows. The weight ratio is preferably 10:90 to 90:10. Exceeding the above range makes it difficult to obtain the effects of the present invention.

Incidentally, in the magnetic recording medium of this embodiment,
As a method of retaining the lubricant in the outermost layer, a method of top-coating the lubricant layer on the surface of the magnetic layer 2 or the surface of the protective film 3 (here, the surface of the protective film 3) can be mentioned. here,
The application amount is 0.05 (mg / m ² ) to 100 (mg
/ M ² ), preferably from 0.1 (mg / m ² )
More preferably, it is 50 (mg / m ² ). If the coating amount is too small, the friction coefficient decreases,
The effect of improving the durability is not exhibited, and if the coating amount is too large, a shearing phenomenon occurs between the sliding member and the sliding portion, and the running performance is rather deteriorated.

Further, in the magnetic recording medium of this embodiment, a rust preventive may be used in combination, if necessary. As the rust inhibitor, any one can be used as long as it is generally used as a rust inhibitor for this type of magnetic recording medium, for example, phenols,
Examples include naphthols, quinones, heterocyclic compounds containing a nitrogen atom, heterocyclic compounds containing an oxygen atom, and heterocyclic compounds containing a sulfur atom.

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

The binder resin used in the backcoat paint includes, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid Ester-acrylonitrile copolymer, thermoplastic polyurethane elastomer, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative,
Polyester resin, phenolic resin, epoxy resin, polyurethane curable resin, melamine resin, alkyd resin, silicone resin, epoxy-polyamide resin, nitrocellulose-melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, methacrylate copolymer Examples thereof include a mixture of a coalesced diisocyanate prepolymer, a mixture of a polyester polyol and a polyisocyanate, a urea formaldehyde resin, a mixture of a low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate, a polyamine resin, and a mixture thereof.

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

On the other hand, examples of the powder component include carbon-based fine powder for imparting conductivity and inorganic pigments added for controlling surface roughness and improving durability. Examples of the carbon-based fine particles include furnace carbon, channel carbon, acetylene carbon, thermal carbon, and lamp carbon. Examples of the inorganic pigment include α-FeOOH, α-Fe ₂ O ₃ , and Cr _2.
O ₃ , TiO ₂ , ZnO, SiO, SiO ₂ , SiO ₂
・ 2H ₂ O, Al ₂ O ₃ , CaCO ₃ , MgCO
₃ , Sb ₂ O _{3 and the} like.

Further, examples of the organic solvent for the backcoat paint include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.
Ester solvents such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl ether;
Glycol ether solvents such as glycol dimethyl ether, glycol monoethyl ether and dioxane; aromatic hydrocarbon solvents such as benzene, toluene and xylene; aliphatic hydrocarbon solvents such as hexane and heptane; methylene chloride, ethylene chloride, carbon tetrachloride General-purpose solvents such as chlorinated hydrocarbon solvents such as chloroform, ethylene chlorohydrin and dichlorobenzene can be used.

Further, a lubricant may be used in combination with the back coat layer. In this case, there is a method of internally adding a lubricant to the back coat layer, or a method of applying a lubricant on the back coat layer. In any case, 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 the lubricant.

The magnetic recording medium of this embodiment has a non-magnetic support 1 having at least a magnetic layer 2 formed thereon, and a protective film 3 which is the outermost layer has a bifunctional perfluoropolyether having a carboxyl group at its terminal. And a lubricant containing an amine compound and a carboxylic acid perfluoroalkyl ester derivative. In this lubricant, adhesion and lubricity are maintained under any use conditions, and the lubricant is used for a long time. Since the lubrication effect is maintained, good running properties and durability of the magnetic recording medium are ensured.

Further, in the magnetic recording medium of this embodiment, since the magnetic layer 2 is formed of a ferromagnetic metal thin film, it can sufficiently cope with high-density recording and long-time recording, and is used as the protective film 3 as the outermost layer. Forming a material made of carbon ensures sufficient durability.

As a magnetic recording medium to which the present invention is applied,
The following are also examples. The magnetic recording medium of this example has substantially the same configuration as that of the magnetic recording medium of the above-described example, and differs only in the lubricant held in the outermost layer. Therefore, only the lubricant will be described.

That is, in the magnetic recording medium of this example, in particular, the protective film 3, which is the outermost layer, is composed of a compound of a perfluoropolyether having a carboxyl group at a terminal represented by the following formula (17) and an amine, and A lubricant containing the indicated perfluoroalkyl carboxylate derivative is retained.

[0075]

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[0076]

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The compound of a perfluoropolyether having a carboxyl group at a terminal and an amine represented by the above formula (17) can be easily synthesized by the following method. For example, it can be synthesized by mixing a monofunctional perfluoropolyether and an amine and heating the mixture at a temperature equal to or higher than the melting point of the amine used. When stearylamine is used as the amine, for example, the mixture may be heated and mixed at 60 (° C.).

Further, it can also be obtained by dissolving both in an organic solvent and then removing the solvent. When the amine is a quaternary ammonium compound, a metal salt of perfluoropolyether (such as sodium salt) and a quaternary ammonium salt (such as chloride, iodide, sulfate, etc.) are mixed and extracted with an organic solvent. Obtainable.

Here, as the perfluoropolyether having a carboxyl group at the terminal, a commercially available perfluoropolyether can be used, and F (CF ₂ CF ₂ CF ₂ O) _m CF ₂ C
F ₂ COOH or CF ₃ [OCF (CF ₃ ) CF ₂ ] _j
(OCF ₂ ) _k COOH and the like. Perfluoropolyether having a carboxyl group at the above terminal,
Of course, it is not limited to these. In the above perfluoropolyether chemical formula, m, j, and k each 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 is practically preferably about 600 to 5000, more preferably 1000 to 4000. 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 diminished.

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.

One of the amines is a primary amine or a secondary amine.
Both amines and tertiary amines can be used, and quaternary ammonium compounds can also be used. 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.

Further, the above-mentioned chemical formula 18 contained in the above-mentioned lubricant is used.
The carboxylic acid perfluoroalkyl ester derivative shown in (1) is as described above, and the description is omitted here.

Further, in the lubricant used in the magnetic recording medium of the present example, the mixing ratio of the compound of the perfluoropolyether having a carboxyl group at the terminal to the amine and the perfluoroalkyl ester derivative of the carboxylic acid is by weight. The ratio is preferably from 10:90 to 90:10. Exceeding the above range makes it difficult to obtain the effects of the present invention.

By the way, in the magnetic recording medium of this embodiment,
As a method of retaining the lubricant in the outermost layer, a method of top-coating the lubricant layer on the surface of the magnetic layer 2 or the surface of the protective film 3 (here, the surface of the protective film 3) may be mentioned. Here, the coating amount is 0.05 (mg / m ² ) to 100
(Mg / m ² ), preferably 0.1 (mg / m ² ).
m ² ) to 50 (mg / m ² ).
If the coating amount is too small, the effect of lowering the coefficient of friction and improving wear resistance and durability will not be exhibited, and if the coating amount is too large, the distance between the sliding member and the ferromagnetic metal thin film will not increase. As a result, a cracking phenomenon occurs, and the running performance is rather deteriorated.

The magnetic recording medium of this embodiment also has at least a magnetic layer 2 formed on a non-magnetic support 1 like the magnetic recording medium of the above-described example, and a protective film 3, which is the outermost layer,
A lubricant containing a perfluoropolyether having a carboxyl group at the terminal and a compound of an amine and a perfluoroalkyl ester derivative of a carboxylic acid is retained. Since the lubricating effect is maintained and the lubricating effect is maintained for a long period of time, good running properties and durability of the magnetic recording medium are ensured.

Also, in the magnetic recording medium of this embodiment, since the magnetic layer 2 is made of a ferromagnetic metal thin film, as in the magnetic recording medium of the above-described example, it can sufficiently cope with high-density recording and long-time recording. If a protective film 3 made of carbon is formed as the outermost layer, sufficient durability is ensured.

As a magnetic recording medium to which the present invention is applied,
The following are also examples. The magnetic recording medium of this example has substantially the same configuration as that of the magnetic recording medium of the above-described example, and differs only in the lubricant held in the outermost layer. Therefore, only the lubricant will be described.

That is, in the magnetic recording medium of this example, in particular, the protective film 3, which is the outermost layer, is composed of a compound of a perfluoropolyether having a carboxyl group at a terminal represented by the following formula and a diamine and a compound represented by the following formula: A lubricant containing the indicated perfluoroalkyl carboxylate derivative is retained.

[0090]

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[0091]

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The compound of a perfluoropolyether having a carboxyl group at the terminal and a diamine represented by the above formula 19 can be easily synthesized by the following method. For example, it can be synthesized by mixing a monofunctional perfluoropolyether and a diamine and heating the mixture at a temperature equal to or higher than the melting point of the diamine used.

Here, as the perfluoropolyether having a carboxyl group at the terminal, commercially available ones can be used, and F (CF ₂ CF ₂ CF ₂ O) _s CF ₂ C
F ₂ COOH or CF ₃ [OCF (CF ₃ ) CF ₂ ] _t
(OCF ₂ ) _u COOH and the like. Perfluoropolyether having a carboxyl group at the above terminal,
Of course, it is not limited to these. In the above perfluoropolyether chemical formula, s, t, and u each represent an integer of 1 or more.

The molecular weight of the perfluoropolyether having a carboxyl group at its terminal is not particularly limited, but is practically preferably about 600 to 5000, more preferably 1000 to 4000. 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 diminished.

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, the structure of the diamine is optional.
It can be arbitrarily selected regardless of a branched structure, an isomer structure, an alicyclic structure, a molecular weight, and the presence or absence of an unsaturated bond.

Further, the above-mentioned chemical formula 20 contained in the above-mentioned lubricant is used.
The carboxylic acid perfluoroalkyl ester derivative shown in (1) is as described above, and the description is omitted here.

Further, in the lubricant used for the magnetic recording medium of the present example, the mixing ratio of the compound of perfluoropolyether having a carboxyl group at the end and the diamine and the perfluoroalkyl ester derivative of carboxylic acid is as follows:
The weight ratio is preferably from 10:90 to 90:10.
Exceeding the above range makes it difficult to obtain the effects of the present invention.

By the way, in the magnetic recording medium of this example,
As a method of retaining the lubricant in the outermost layer, a method of top-coating the lubricant layer on the surface of the magnetic layer 2 or the surface of the protective film 3 (here, the surface of the protective film 3) may be mentioned. Here, the coating amount is 0.05 (mg / m ² ) to 100
(Mg / m ² ), preferably 0.1 (mg / m ² ).
m ² ) to 50 (mg / m ² ).
If the coating amount is too small, the effect of lowering the coefficient of friction and improving wear resistance and durability will not be exhibited, and if the coating amount is too large, the distance between the sliding member and the ferromagnetic metal thin film will not increase. As a result, a cracking phenomenon occurs, and the running performance is rather deteriorated.

The magnetic recording medium of the present embodiment also has at least a magnetic layer 2 formed on a nonmagnetic support 1 like the magnetic recording medium of the above-described example, and a protective film 3 as an outermost layer has
A lubricant containing a compound of a perfluoropolyether and a diamine having a carboxyl group at a terminal and a perfluoroalkyl ester derivative of a carboxylic acid is retained. Since the lubricating effect is maintained and the lubricating effect is maintained for a long period of time, good running properties and durability of the magnetic recording medium are ensured.

Also, in the magnetic recording medium of this embodiment, the magnetic layer 2 is made of a ferromagnetic metal thin film similarly to the magnetic recording medium of the above-mentioned example, so that it can sufficiently cope with high-density recording and long-time recording. If a protective film 3 made of carbon is formed as the outermost layer, sufficient durability is ensured.

The magnetic recording medium to which the present invention is applied as described above is manufactured as follows. That is, after forming a ferromagnetic metal thin film to be a magnetic layer on a non-magnetic support by, for example, a vacuum evaporation method, a protective film is formed by, for example, a magnetron sputtering method, and a predetermined lubricant is top-coated on the protective film. The lubricant is held on the protective film. Further, a back coat layer or the like may be formed as necessary.

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 evaporation apparatus is configured for so-called oblique evaporation, and is cooled to, for example, about -20 (° C.) in a vacuum chamber 11 in which the inside is evacuated to, for example, about 1 × 10 ⁻³ (Pa). The cooling can 12 rotates counterclockwise as indicated by an arrow A in the figure, and a vapor deposition 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 a counterclockwise direction in the figure and a winding roll 15 rotating in a counterclockwise direction in the figure are also arranged in the vacuum chamber 11. The non-magnetic support 16 is unreeled from the supply roll 14 in the direction indicated by the arrow B in the drawing, travels along the peripheral surface of the cooling can 12, and
5 is wound up.

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

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

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

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

In this embodiment, an example in which a ferromagnetic metal thin film made of Co is formed by an oblique evaporation method has been described. However, as a method of forming a ferromagnetic metal thin film, in addition to this example, a vertical evaporation method, a sputtering method, or the like may be used. A known thin film forming method can be applied. As a material of the ferromagnetic metal thin film, N
i, Fe, and alloys thereof can be used. The thickness of the ferromagnetic metal thin film is about 0.01 to 0.4 (μm), preferably about 0.1 to 0.2 (μm).

FIG. 3 shows a magnetron sputtering apparatus for forming the protective film.

In this magnetron sputtering apparatus, a cooling can 32 rotating counterclockwise as shown by an arrow D in the figure and a target 33 opposed to the cooling can 32 are provided in a chamber 31. It is.

A vacuum pump 34 for reducing the pressure in the chamber 31 is connected to the chamber 31 via a valve 35, and a gas supply pipe 36 for introducing a gas into the chamber 31 is connected to a gas supply unit 37. It is arranged with.

Therefore, the chamber 31 is evacuated by, for example, reducing the pressure of the valve 35 to about 10 ^-4 (Pa) by the vacuum pump 34 to the side of the vacuum pump 34 from the fully open state to 10 degrees. By reducing the speed and introducing Ar gas from the gas introduction pipe 36, the degree of vacuum is reduced to about 0.1.
8 (Pa). The cooling can 32 is cooled to, for example, about −40 ° C.

The target 33 is a material for a carbon protective film, and is supported by a backing plate 38 constituting a cathode electrode. On the back side of the backing plate 38, a magnet 3 for forming a magnetic field is provided.
9 are arranged.

In the chamber 31, a supply roll 40 rotating in a counterclockwise direction in the figure and a winding roll 41 rotating in a counterclockwise direction in the figure are also provided. The body 30 is moved from the supply roll 40 by an arrow E in FIG.
And travels along the peripheral surface of the cooling can 32, and is then wound up by a winding roll 41.

When a carbon protective film is formed by this magnetron sputtering apparatus, Ar gas is introduced from the gas introduction pipe 36, and a voltage of 3000 V is applied by using the cooling can 32 as an anode and the backing plate 38 as a cathode. A state in which a current of 4 A flows is maintained.

By applying this voltage, Ar gas is turned into plasma, and the ions of the ionized ions collide with the target 33, whereby the atoms of the target 33 are repelled.
At this time, a magnet 39 is provided on the back side of the backing plate 38, and a magnetic field is formed near the target 33.
Will be concentrated near.

The atoms ejected from the target 33 adhere to the non-magnetic support 30 on which the ferromagnetic metal thin film running along the peripheral surface of the cooling can 32 arranged opposite to the target 33 is formed. Thus, a protective film made of, for example, carbon is formed.

This protective film has a thickness of about 3 to 15 (nm), particularly about 5 to 10 (nm), so as to reduce the spacing loss and obtain the effect of preventing the ferromagnetic metal thin film from being worn.
(Nm).

In this embodiment, an example in which the protective film is formed by magnetron sputtering has been described. Other methods for forming the protective film include known thin films such as ion beam sputtering, ion beam plating, and CVD. A forming method can be used.

[0122]

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

Experimental Example 1 In this experimental example, the effect of using a lubricant containing a compound of a bifunctional perfluoropolyether having a terminal carboxyl group and an amine and a perfluoroalkyl ester derivative of a carboxylic acid as a lubricant was used. Was confirmed.

(Preparation of Sample) Synthesis of perfluoropolyetheramine salt compound First, a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal and an amine was synthesized.

First, a bifunctional perfluoropolyether HOOCCF ₂ (OC ₂
F ₄ ) _p (OCF ₂ ) _q OCF ₂ COOH (molecular weight: 4
000, provided that p and q in the chemical formula each represent an integer of 1 or more. 20) (g) was placed in a round bottom flask and 3.6 (g) of octadecylamine was added. Then 50
(° C.), and the mixture was sufficiently stirred and homogenized, and then cooled to obtain a perfluoropolyetheramine salt. This will be referred to as Compound 1 for convenience.

Next, in the same manner as in the above-mentioned compound 1, four kinds of compounds 2 to 5 of a bifunctional perfluoropolyether having a terminal carboxyl group and an amine were synthesized. Rf ₁ , R ₁ , R ₂ , R ₃ and R ₄ in the following formula 21 of the bifunctional perfluoropolyether having a carboxyl group at the terminal used in producing each compound are as shown in Table 1 below. It is assumed. Table 1 shows that Compound 1
Of the bifunctional perfluoropolyether having a terminal carboxyl group used in the production of
₁ , R ₁ , R ₂ , R ₃ and R ₄ are also shown. Table 1
P represents an integer of 1 or more.

[0127]

Embedded image

[0128]

[Table 1]

[0129] 2. Production of Sample Tape Next, a magnetic tape was produced as a magnetic recording medium. That is, first, Co is applied to a 7.0 (μm) -thick polyethylene terephthalate film, which is a nonmagnetic support, by an oblique evaporation method using the above-described vacuum evaporation apparatus, and a 180-nm-thick magnetic film is formed. A ferromagnetic metal thin film to be a layer was formed. Next, using the above-mentioned magnetron sputtering apparatus, about 8 mm of a protective film is formed on the ferromagnetic metal magnetic thin film.
A carbon protective film having a thickness of (nm) was formed.

Next, on the surface of the polyethylene terephthalate film opposite to the surface on which the ferromagnetic metal thin film was formed, a 0.5 (μ)
m) to form a back coat layer.

Next, as described above, the ferromagnetic metal thin film and the carbon protective film are formed on one main surface side, and the carbon protective film surface of the non-magnetic support having the back coat layer formed on the other main surface side, Each of the compounds shown in Table 2 below was dissolved in a hexane solvent, and applied in such a manner that the coating amount was 5 (mg / m ² ) to obtain 13 types of magnetic recording media. These one
Three types of magnetic recording media were cut to a width of 6.35 (mm), and 13 types of sample tapes of Examples 1 to 8 and Comparative Examples 1 to 5 were produced.

[0132]

[Table 2]

3. Evaluation of Characteristics Next, the characteristics of the 13 types of sample tapes of Examples 1 to 8 and Comparative Examples 1 to 5 were evaluated. Here, durability and running performance were evaluated, and specifically, the friction coefficient, still durability, and shuttle durability were evaluated. The environmental conditions at the time of these evaluations were determined to be the most severe conditions after the present inventors examined.

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

(2) Still Durability Measuring Method Still durability was evaluated in a constant temperature bath at -5 (° C.).
A commercially available digital video camcorder (manufactured by Sony Corporation, model name: DVC-VX1000) was used to measure the time until the reproduction output of each sample tape dropped by 3 (dB).

(3) Method of Measuring Shuttle Durability Shuttle durability is determined by measuring environmental conditions in a thermostat at a temperature of 40 ° C.
(° C.) and a humidity of 20 (% RH), using a commercially available digital video camcorder (manufactured by Sony Corporation, model name: DVC-VX1000) in this constant temperature bath, and running each sample tape for 100 pass shuttle. After running 100 passes, how much (dB) the reproduced output dropped from the initial output was measured and evaluated.

These evaluations were made immediately after the lubricant was applied and at a temperature of 45 ° C. and a humidity of 80 ° C. for each sample tape.
(% RH), after storage for one month. Table 3 shows the results of the initial durability and running properties immediately after the application of the lubricant, and Table 4 shows the results of the durability and running properties after storage after storage for one month.

[0138]

[Table 3]

[0139]

[Table 4]

From the results shown in Tables 3 and 4, Examples 1 to 4 using a lubricant in which a compound of a bifunctional perfluoropolyether having a carboxyl group at the terminal and an amine and a perfluoroalkyl ester derivative of a carboxylic acid were combined were used.
8, the friction coefficient and still durability under various use conditions such as high temperature and high humidity, high temperature and low humidity or low temperature,
It can be seen that the deterioration of shuttle durability was extremely small, and very good results were obtained.

On the other hand, a lubricant containing only a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal and an amine, or a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal and an amine and a carboxylic acid In Comparative Examples 1 to 5 using a lubricant in which a carboxylic acid perfluoroalkyl ester derivative containing an unsaturated bond in a part was combined, the friction coefficient and the friction coefficient under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature were all used. It can be seen that still durability and shuttle durability deteriorated greatly, and good results could not be obtained.

From these results, it was confirmed that the initial properties can be maintained even after long-term storage, particularly by using the perfluoroalkyl carboxylate derivative used in the present invention.

That is, when the present invention is applied and a lubricant containing a compound of a bifunctional perfluoropolyether having a terminal carboxyl group and an amine and a perfluoroalkyl ester derivative of a carboxylic acid is retained in the outermost layer, It has been confirmed that the lubricant maintains good adhesion and lubricity under any use conditions and maintains the lubricating effect for a long period of time, so that good running properties and durability of the magnetic recording medium are ensured. Was done.

Experimental Example 2 In this experimental example, the effect of using a lubricant containing a compound of perfluoropolyether having terminal carboxyl groups and an amine and a perfluoroalkyl ester derivative of carboxylic acid as a lubricant was confirmed. It was decided to.

(Preparation of Sample) Synthesis of perfluoropolyether amine salt compound First, a compound of a perfluoropolyether having a carboxyl group at a terminal and an amine was synthesized.

First, perfluoropolyether F having a carboxyl group at a terminal (CF ₂ CF ₂ CF ₂ O) _m
CF ₂ CF ₂ COOH (molecular weight:. 1700, although, m in the formula represents an integer of 1 or more) taken 20 (g) in a round bottom flask was added octadecylamine 3.2 (g). Next, the mixture was dissolved by heating at 50 (° C.), sufficiently stirred to be uniform, and then cooled to obtain a perfluoropolyetheramine salt. This will be referred to as compound 6 for convenience.

Next, in the same manner as in the above-mentioned compound 6, four kinds of compounds 7 to 10 of a perfluoropolyether having a carboxyl group at a terminal and an amine were synthesized. The perfluoropolyether having a carboxyl group at the terminal used in the production of each compound has Rf ₂ , R
₁₁ , R ₁₂ , R ₁₃ and R ₁₄ are as shown in Table 5 below. In Table 5, Rf ₂ , R ₁₁ , R ₁₂ ,
R ₁₃ and R ₁₄ are also shown together. In Table 1, j, k, and m are 1
The above integers are respectively represented.

[0148]

Embedded image

[0149]

[Table 5]

2. Production of Sample Tape Next, a magnetic tape was produced as a magnetic recording medium. That is, a ferromagnetic metal thin film serving as a magnetic layer and a carbon protective film serving as a protective film were formed on a nonmagnetic support in the same manner as in Experimental Example 1, and a back coat layer was also formed.

Next, in the same manner as in Experimental Example 1 described above, each of the compounds shown in Table 6 below was dissolved in a hexane solvent on the surface of the carbon protective film so that the coating amount was 5 (mg / m ² ). To obtain 13 types of magnetic recording media. These 13 types of magnetic recording media are 6.35 (mm)
Examples 9 to 16 and Comparative Examples 6 to 10 were cut into widths.
13 sample tapes were produced.

[0152]

[Table 6]

3. Evaluation of Characteristics Next, the characteristics of the 13 types of sample tapes of Examples 9 to 16 and Comparative Examples 6 to 10 were evaluated. Here, durability and running performance 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 the above-mentioned Experimental Example 1, and each sample tape was stored for one month in an environment of a temperature of 45 (° C.) and a humidity of 80 (% RH). I went after. 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 one month.

[0155]

[Table 7]

[0156]

[Table 8]

From the results of Tables 7 and 8, it can be seen from Examples 9 to 16 that a lubricant in which a compound of a perfluoropolyether having a carboxyl group at a terminal at the terminal and an amine and a perfluoroalkyl ester derivative of a carboxylic acid were used was used. 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.

On the other hand, a lubricant containing only a compound of a perfluoropolyether having a carboxyl group at a terminal and an amine, or a compound of a perfluoropolyether having a carboxyl group at a terminal and an amine and an unsaturated compound having a carboxylic acid moiety Comparative Example 6 Using Lubricants Combined with Carboxylic Acid Perfluoroalkyl Ester Derivatives Containing Bonds
Nos. 10 to 10, the friction coefficient, still durability, and shuttle durability deteriorated greatly under various use conditions such as high temperature and high humidity, high temperature and low humidity, and low temperature, and it was found that good results could not be obtained.

From these results, it was confirmed that the initial properties can be maintained even after long-term storage, particularly by using the perfluoroalkyl carboxylate derivative.

That is, when the present invention is applied and a lubricant containing a compound of perfluoropolyether and amine having a carboxyl group at a terminal and a perfluoroalkyl ester derivative of carboxylic acid is held in the outermost layer, the above lubricant can be obtained. However, it is confirmed that the adhesiveness and lubricity are maintained under any use conditions and the lubricating effect is maintained for a long period of time, so that good running properties and durability of the magnetic recording medium are ensured. .

Experimental Example 3 In this experimental example, the effect of using a lubricant containing a compound of a perfluoropolyether having a carboxyl group at a terminal at the end and a diamine and a perfluoroalkyl ester derivative of a carboxylic acid was confirmed. It was decided to.

(Preparation of Sample) Synthesis of Perfluoropolyether Diamine Salt Compound First, a compound of a perfluoropolyether having a carboxyl group at a terminal and a diamine was synthesized.

First, a perfluoropolyether F having a carboxyl group at a terminal (CF ₂ CF ₂ CF ₂ O) _m
CF ₂ CF ₂ COOH (molecular weight:. 1700, provided that the m in Formula represents an integer of 1 or more) 20 (g) taken in a round bottom flask, 1,4-diamine knob Tan 0.52
(G) was added. Next, the mixture was heated and dissolved at 50 (° C.), sufficiently stirred to be uniform, and then cooled to obtain a perfluoropolyetherdiamine salt. For convenience, compound 11
Shall be referred to as

Next, in the same manner as in the above-mentioned compound 11, four kinds of compounds 12 to 15 of a perfluoropolyether having a carboxyl group at a terminal and a diamine were synthesized. Rf of perfluoropolyether having a carboxyl group at a terminal used in the production of each compound,
_{3, R 21, R 22,} R 23, R 24, R 25, R 26, R 31 are as shown in Table 9 below. Table 9 shows that the perfluoropolyether having a carboxyl group at the terminal used in the production of Compound 11 is
Rf ₃ , R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , R ₂₅ , R _{26 in 3} ,
R _{31 is} also shown. In Table 1, s, t, and u each represent an integer of 1 or more.

[0165]

Embedded image

[0166]

[Table 9]

2. Production of Sample Tape Next, a magnetic tape was produced as a magnetic recording medium. That is, a ferromagnetic metal thin film serving as a magnetic layer and a carbon protective film serving as a protective film were formed on a nonmagnetic support in the same manner as in Experimental Example 1, and a back coat layer was also formed.

Next, in the same manner as in Experimental Example 1 described above, each of the compounds shown in Table 10 below dissolved in a hexane solvent was applied to the surface of the carbon protective film so that the coating amount was 5 (mg / m ² ). To obtain 13 types of magnetic recording media. These 13 types of magnetic recording media are stored in 6.35 (m
m) Each was cut to a width, and Examples 17 to 24 and Comparative Example 1 were cut.
Thirteen types of sample tapes 1 to 15 were produced.

[0169]

[Table 10]

[0170] 3. Evaluation of Characteristics Next, 13 of Examples 17 to 24 and Comparative Examples 11 to 15 described above.
The properties of the different sample tapes were evaluated. Here, durability and running performance were evaluated. Specifically, the friction coefficient, still durability, and shuttle durability were evaluated in the same manner as in Experimental Example 1 described above.

[0171] These evaluations were carried out immediately after the lubricant was applied in the same manner as in Experimental Example 1 above, and the sample tapes were stored for one month in an environment of a temperature of 45 (° C) and a humidity of 80 (% RH). I went after. Table 11 shows the results of the initial durability and running properties immediately after the application of the lubricant, and Table 12 shows the results of the durability and running properties after storage after storage for one month.

[0172]

[Table 11]

[0173]

[Table 12]

From the results of Tables 11 and 12, it can be seen from Example 17 that a lubricant in which a compound of a perfluoropolyether having a carboxyl group at a terminal at the end and a diamine and a perfluoroalkyl ester derivative of a carboxylic acid were combined was used.
~ 24, the deterioration of 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 was extremely small, and very good results were obtained. Recognize.

On the other hand, a lubricant containing only a compound of a perfluoropolyether having a terminal carboxyl group and a diamine, or a compound of a perfluoropolyether having a terminal carboxyl group and a diamine and an unsaturated compound having a carboxylic acid moiety In Comparative Examples 11 to 15 using a lubricant in which a carboxylic acid perfluoroalkyl ester derivative containing a bond was combined, the friction coefficient and still durability under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature were all used. It can be seen that the shuttle durability was greatly deteriorated and good results could not be obtained.

From these results, it was confirmed that the initial characteristics can be maintained even after long-term storage, particularly by using the perfluoroalkyl carboxylate derivative used in the present invention.

That is, when the present invention is applied and a lubricant containing a compound of a perfluoropolyether having a carboxyl group at a terminal at the end and a diamine compound and a perfluoroalkyl ester derivative of a carboxylic acid is held in the outermost layer, the lubricant However, it is confirmed that the adhesiveness and lubricity are maintained under any use conditions and the lubricating effect is maintained for a long period of time, so that good running properties and durability of the magnetic recording medium are ensured. .

[0178]

As described above, in the magnetic recording medium according to the present invention, at least a magnetic layer is formed on a nonmagnetic support, and the outermost layer has a bifunctional perfluoro group having a carboxyl group at a terminal. A lubricant containing a compound of a polyether and an amine and a perfluoroalkyl ester derivative of a carboxylic acid, or a lubricant containing a compound of a perfluoropolyether and an amine having a carboxyl group at a terminal and a perfluoroalkyl ester derivative of a carboxylic acid, or A lubricant containing a compound of perfluoropolyether and diamine having a carboxyl group at the terminal and a perfluoroalkyl ester derivative of carboxylic acid is held in the outermost layer.In these lubricants, under any use conditions, Adhesiveness and lubricity are maintained and for a long time Because lubricating effect lasts, good running properties and durability of the magnetic recording medium is ensured.

In the magnetic recording medium of the present invention, if the magnetic layer is made of a ferromagnetic metal thin film, it can sufficiently cope with high-density recording and long-time recording, and a protective film made of carbon can be formed as the outermost layer. In this case, sufficient durability is ensured.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a magnetic recording medium to which the present invention is applied.

FIG. 2 is a schematic cross-sectional view of a main part showing a configuration of a continuous winding type vacuum evaporation apparatus.

FIG. 3 is a schematic sectional view of a main part showing a configuration of a magnetron sputtering apparatus.

[Explanation of symbols]

 1 non-magnetic support, 2 magnetic layer, 3 protective film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10N 40:18

Claims (15)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support and at least a magnetic layer formed thereon, comprising a compound of a bifunctional perfluoropolyether having a carboxyl group at a terminal represented by the following formula (1) and an amine: A magnetic recording medium comprising a lubricant containing a carboxylic acid perfluoroalkyl ester derivative represented by Chemical formula 2 held in an outermost layer. Embedded image Embedded image 2. The mixing ratio between the compound of the bifunctional perfluoropolyether having a carboxyl group at the terminal and the amine and the perfluoroalkyl ester derivative of the carboxylic acid is 10:90 to 90:10 by weight. The magnetic recording medium according to claim 1, wherein: 3. The magnetic recording medium according to claim 1, wherein said magnetic layer is made of a ferromagnetic metal thin film. 4. The magnetic recording medium according to claim 1, wherein a protective film is formed as an outermost layer on said magnetic layer. 5. The magnetic recording medium according to claim 4, wherein said protective film is made of carbon. 6. A magnetic recording medium comprising at least a magnetic layer formed on a nonmagnetic support, comprising a compound of a perfluoropolyether having a carboxyl group at a terminal represented by the following formula (3) and an amine; A magnetic recording medium characterized in that a lubricant containing a carboxylic acid perfluoroalkyl ester derivative represented by the formula (1) is held in an outermost layer. Embedded image Embedded image 7. The mixing ratio of the compound of perfluoropolyether having a carboxyl group at a terminal to an amine and the perfluoroalkyl ester derivative of carboxylic acid is 10:90 to 90:10 by weight. 7. The magnetic recording medium according to claim 6, wherein: 8. The magnetic recording medium according to claim 6, wherein said magnetic layer is made of a ferromagnetic metal thin film. 9. The magnetic recording medium according to claim 6, wherein a protective film is formed as an outermost layer on the magnetic layer. 10. The magnetic recording medium according to claim 9, wherein said protective film is made of carbon. 11. A magnetic recording medium comprising at least a magnetic layer formed on a non-magnetic support, comprising: a compound of a perfluoropolyether having a carboxyl group at a terminal represented by the following formula (5) and a diamine; A magnetic recording medium characterized in that a lubricant containing a carboxylic acid perfluoroalkyl ester derivative represented by the formula (1) is held in an outermost layer. Embedded image Embedded image 12. The mixing ratio of the compound of perfluoropolyether having a carboxyl group at a terminal to a diamine and the perfluoroalkyl ester derivative of carboxylic acid is 10:90 to 90:10 by weight. The magnetic recording medium according to claim 11, wherein 13. The magnetic recording medium according to claim 11, wherein said magnetic layer is made of a ferromagnetic metal thin film. 14. The magnetic recording medium according to claim 11, wherein a protective film is formed as an outermost layer on said magnetic layer. 15. The magnetic recording medium according to claim 14, wherein said protective film is made of carbon.