JP2002092857A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize good running property and durability and to prevent wear of a head or deterioration in magnetic characteristics by using a lubricant which maintains the lubrication effect and prevents powder dropout. SOLUTION: The medium has a nonmagnetic substrate, a magnetic layer consisting of a ferromagnetic metal material formed on the nonmagnetic substrate, and a protective film formed on the magnetic layer and is used for a helical scanning magnetic recording system which uses a magnetoresistive reproducing head. In the medium, a lubricant layer containing diesters having long-chain alkyl groups and partially fluorinated alkyl groups expressed by formula 1 is formed on the protective film. In formula, R1 represents an aliphatic alkyl group or aliphatic alkenyl group and R2 represents a fluoroalkyl group or fluoroalkenyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium in which a metal magnetic thin film is formed as a magnetic layer on a nonmagnetic support by a vacuum thin film forming technique.

[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.

In recent years, miniaturization of magnetic recording / reproducing apparatuses has been progressing. 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.

[0007]

Generally, the magnetic recording medium is always in contact with the magnetic head while traveling at a high speed when traveling in a helical scan type magnetic recording / reproducing apparatus. Very susceptible to wear and damage due to contact with the head. Therefore, in a magnetic recording medium of a ferromagnetic metal thin film type, a protective film made of carbon or the like, a lubricant layer, and the like are formed on a magnetic layer to improve running properties and durability.

However, the protective film and the lubricant formed for the purpose of realizing 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, and by using perfluoropolyether or the like as a lubricant, good lubrication is obtained under any use conditions. 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.

The present invention has been proposed in view of such a conventional situation, and the lubricating effect is maintained for a long period of time. It is another object of the present invention to provide a magnetic recording medium having good running properties and durability, and preventing head wear and deterioration of magnetic characteristics.

[0014]

In order to achieve the above-mentioned object, a magnetic recording medium according to the present invention comprises a non-magnetic support,
A helical scan magnetic recording system using a magnetoresistive read head, comprising: a magnetic layer formed on the nonmagnetic support and formed of a ferromagnetic metal material; and a protective film formed on the magnetic layer. In the magnetic recording medium to be used, a lubricant layer containing a diester having a long-chain alkyl group and a partially fluorinated alkyl group represented by the following formula 2 is formed on the protective film.

[0015]

Embedded image

In the magnetic recording medium according to the present invention configured as described above, the lubricant layer containing the compound represented by the above formula (2) is formed as the uppermost layer on the protective film. The lubricating property is well maintained also under, and the occurrence of powder drop is prevented.

[0017]

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

A magnetic recording medium 1 to which the present invention is applied has a structure shown in FIG.
As shown in FIG. 2, a magnetic layer 3 is formed on one main surface of the non-magnetic support 2.
A magnetic metal thin film made of a ferromagnetic metal material is formed, a protective film 4 is formed on the magnetic layer 3, and a lubricant layer 5 is formed on the protective film 4 as an uppermost layer.

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; plastics such as polycarbonate, polyimide, polyamide and polyamide imide; aluminum alloys and titanium alloys And other light metals, and ceramics such as glass.

When a rigid material such as an aluminum alloy plate or a glass plate is used as the non-magnetic support 2, the surface of the non-magnetic support 2 is subjected to alumite treatment or the like to form an oxide film, a Ni-P film, or the like. It may be formed so that the surface of the nonmagnetic support 2 is hardened.

The form of the non-magnetic support 2 may be any form such as a film, a sheet, a disk, a card, and a drum.

Further, as the non-magnetic support 2, there can be used a non-magnetic support in which at least one kind of projections among mountain-like projections, wrinkle-like projections, and granular projections is formed, and the surface roughness is controlled. .

In the magnetic recording medium 1, the surface property 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 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 to 200 nm.
And its density is 1 × 10 ⁵
It is preferable that the number is 1 × 10 ⁷ / mm ² .

The projections are formed when the nonmagnetic support 2 is formed.
It is formed by internally adding inorganic fine particles having a particle size of about 50 to 300 nm into the nonmagnetic support 2. The height of the projections is preferably 10 to 100 nm from the nonmagnetic support 2, and the density of the projections is about 1 × 10 ⁴ to
It is preferably 1 × 10 ⁵ / 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 to 1 μm, preferably 0.03 to 0.5 μm
Is more preferable. Further, the shortest interval between the wrinkle-like projections is preferably 0.1 to 20 μm.

Examples of the resin for forming the wrinkle-like projections include polyesters 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 such as 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 to 1000 ppm, a solvent which is a poor solvent of the resin and has a higher boiling point than the good solvent is added to the resin by 10 to 100%. By applying the double-added solution to the surface of the non-magnetic support 2 and drying it, a thin layer having very fine wrinkle-like projections can be formed.

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

The magnetic layer 3 is formed by a so-called physical vapor deposition (PVD) method 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 to 1 μm.

Examples of the ferromagnetic metal material forming the magnetic layer 3 include metals such as Fe, Co, and Ni; Co—Ni alloys; Co—Pt alloys; Co—Pt—Ni alloys;
-Co-based alloy, Fe-Ni-based alloy, Fe-Co-Ni-based alloy, Fe-Ni-B-based alloy, Fe-Co-B-based alloy,
Fe-Co-Ni-B-based alloys, Co-Cr-based alloys or alloys containing metals such as Pt and 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 thickness of the protective film 4 is preferably 2 to 100 nm, and 5 to 30 n.
m is more preferable. The thickness of the protective film 4 is 2 nm
If it is less than 10 mm, 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.

The lubricant layer 5 is formed by coating a lubricant paint obtained by dissolving a lubricant containing a diester having a long-chain alkyl group and a partially fluorinated alkyl group represented by the following formula 3 in a solvent on the protective film 4. It is formed by being applied to.

[0035]

Embedded image

In the lubricant layer 5, lubricant molecules, that is, an ester which is a polar group of a diester having a long-chain alkyl group and a partially fluorinated alkyl group, is adsorbed on the surface of the protective film 4, and the hydrophobic group of the lubricant molecule is formed. Is formed by the cohesive force between the long-chain hydrocarbon groups.

The ph of the carbon powder generated when the protective film 4 made of carbon is formed by the sputtering method is 2. That is, the protective film 4 made of carbon
Has been found to be strongly acidic. From this, it is expected that if the polar group of the lubricant is an acid having a strong acidity such as carboxylic acid, the adsorption to the carbon film is weak. On the other hand, the ester has a lower acidity than the carboxylic acid, and thus is considered to have better adsorptivity to the carbon film surface than the carboxylic acid. Therefore, the ester is strongly adsorbed on the surface of the carbon film, thereby reducing the friction coefficient and improving the durability.

As described above, the lubricant containing the compound represented by the structural formula (1) has a long-lasting lubricating effect and prevents generation of powder.

In the diester having a long-chain alkyl group and a partially fluorinated alkyl group represented by the structural formula (1), the aliphatic alkyl group or the aliphatic alkenyl group represented by R ¹ has 6 to 27 carbon atoms. Preferably, 1
More preferably, it is 0-18. The aliphatic alkyl group or the aliphatic alkenyl group represented by R ¹ has 6 to 6 carbon atoms.
By setting the ratio to 27, the solubility in the solvent becomes good, and the effect of lowering the friction coefficient and the effect of improving the wear characteristics and durability are surely exhibited.

When the aliphatic alkyl group or aliphatic alkenyl group represented by R ¹ has less than 6 carbon atoms, the length of the alkyl group is too short, and the effect of lowering the friction coefficient and improving the wear characteristics and durability is obtained. May not appear. On the other hand, when the number of carbon atoms exceeds 27, the solubility in a solvent is reduced, and it may be difficult to form a uniform lubricant layer 5.

In the diester having a long-chain alkyl group and a partially fluorinated alkyl group represented by the structural formula (1), the fluoroalkyl group or fluoroalkenyl group represented by R ² has 6 to 27 carbon atoms. It is preferably, and more preferably 6 to 18. By setting the carbon number of the fluoroalkyl group or fluoroalkenyl group represented by R ² to 6 to 27, the solubility in the solvent becomes good, and the effect of reducing the friction coefficient, the effect of improving the wear characteristics and the durability is improved. Will surely appear.

When the fluoroalkyl group or fluoroalkenyl group represented by R ² has less than 6 carbon atoms, the alkyl group length is too short, and the effects of lowering the friction coefficient and improving the wear characteristics and durability appear. There is a possibility that there is no. On the other hand, when the fluoroalkyl group or fluoroalkenyl group represented by R ² has more than 27 carbon atoms, the solubility in a solvent may be low, and it may be difficult to form a uniform lubricant layer 5.

The lubricant layer 5 contains not only a diester having a long-chain alkyl group and a partially fluorinated alkyl group represented by the structural formula (1) but also a combination of a conventionally known lubricant. Is also possible.

The amount of the lubricant paint applied was 0.5 mg / m ²
Is preferably ^{~100mg / m 2, 1mg / m} 2
More preferably, it is で 20 mg / m ² . If the amount of the lubricant paint applied is too small, the effects of lowering the friction coefficient, improving wear resistance and durability may not be sufficiently exhibited. On the other hand, if the application amount of the lubricant paint 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 5 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 5,
A rust preventive layer may be formed between the protective film 4 and the lubricant layer 5. By forming the rust preventive layer and the lubricant layer 5 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 non-magnetic 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, a fine carbon black having an average particle diameter of 10 to 20 nm and a carbon black having an average particle diameter of 230 ~ 300
It is preferable to use coarse-grained carbon black having a diameter of nm.

When carbon black in the form of fine particles 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 carbon black in the form of coarse particles 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 tends to fall off the backcoat 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 Kahncarb and RAVEN manufactured by Columbia Carbon.
MTP (275 nm) can be used.

On the other hand, as the inorganic powder to be 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 to 250 nm, and 100 to 250 nm.
More preferably, it is 210 nm. The amount of the inorganic powder having a Mohs' hardness of 5 to 9 is preferably 3 to 30 parts by weight, more preferably 3 to 20 parts by weight, per 100 parts by weight of 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,
Polymers or copolymers 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, 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.

As the thermosetting resin or the reactive resin,
For example, phenolic resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic reaction resin, formaldehyde resin, silicone resin, epoxy-polyamide resin, a mixture of polyester resin and polyisocyanate prepolymer, polyester polyol and Mixtures of polyisocyanates, mixtures of polyurethanes and polyisocyanates 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,
Ester solvents such as 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; and 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 lubricants, fatty acids,
Any conventionally known lubricants such as fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, silicone-based lubricants, etc. can be used.

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, and a sputtering method. Next, a protective film 4 is formed on the magnetic layer 3 by a PVD method such as sputtering or a CVD method.
To form Next, the structural formula (1) is formed on the protective film 4.
The magnetic recording medium 1 is obtained by forming a lubricant layer 5 by applying a lubricant paint containing the compound shown in FIG. It is needless to say that a back coat layer or the like may be formed as necessary.

First, a method of forming a metal magnetic thin film as the magnetic layer 3 will be specifically described.

When the magnetic layer 3 is formed by a vacuum deposition method, the ferromagnetic metal material is evaporated under a vacuum of 1 × 10 ⁻⁶ to 1 × 10 ⁻² Pa by resistance heating, high frequency heating, electron beam heating or the like. Then, an evaporated metal (ferromagnetic metal material) is deposited on the non-magnetic 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. Furthermore, vacuum deposition may be performed in an oxygen atmosphere to obtain a higher coercive force.

When the magnetic layer 3 is formed by an ion plating method, which is one type of vacuum deposition, 1 × 10 ^-2
A DC glow discharge or an RF glow discharge is caused in an inert gas atmosphere of about 1 × 10 ⁻¹ Pa, and 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 the sputtering method, glow discharge is caused in an atmosphere containing 0.1 to 10 Pa of argon gas as a main component, and the generated argon 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, a method for forming the protective film 4 will be described.

When the protective film 4 is formed by the CVD method,
First, a hydrocarbon gas or a mixed gas of a hydrocarbon gas and an inert gas is introduced into a vacuum vessel.
While maintaining the pressure at about 100 Pa, discharge is performed in a vacuum vessel to generate plasma of a hydrocarbon gas, 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 determined experimentally. Further, the electrodes arranged on the non-magnetic support 2 side on which the magnetic layer 3 is formed
By applying a voltage of -3 kV, the hardness of the protective film 4 can be increased, and the adhesion can be improved.

The hydrocarbon gas used as the material of the protective film 4 includes methane, ethane, propane, butane, pentane, hexane, heptane, octane, ethylene, acetylene,
Propene, butene, pentene, benzene and the like can be used.

Next, a method for forming the lubricant layer 5 will be described.

First, a lubricant containing a diester having a long-chain alkyl group and a partially fluorinated alkyl group represented by the structural formula (1) is dissolved in a solvent to prepare a lubricant coating. Next, the lubricant paint is applied on the protective film 4 to form the lubricant layer 5.

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 diester having a long-chain alkyl group and a partially fluorinated alkyl group represented by the structural formula (1) has a fluorine atom in the molecule similarly to a conventional fluorine-containing lubricant. However, while the conventional fluorine-containing lubricant dissolves only in a fluorine-based solvent, the compound represented by the structural formula (1) is not only used in a fluorine-based solvent but also in a hydrocarbon-based solvent such as toluene and acetone. Dissolve.

That is, when forming the lubricant layer 5 containing the diester having a long-chain alkyl group and a partially fluorinated alkyl group represented by the structural formula (1), the solvent for the lubricant paint is compared with the fluorine-based solvent. Thus, a hydrocarbon solvent having a very small effect on the environment can be used.

As described above, the magnetic recording medium 1 to which the present invention is applied is extremely excellent in terms of lubricity, and has the lubricant layer 5 containing a lubricant in which powder is prevented from falling off. It has good running properties and durability, and prevents head wear and deterioration of magnetic properties.

[0082]

EXAMPLES Hereinafter, specific examples of the present invention will be described in detail based on experimental results.

First, a diester having a long-chain alkyl group and a partially fluorinated alkyl group as a lubricant was synthesized as shown below.

[Synthesis of Diester Having Long Chain Alkyl Group and Partially Fluorinated Alkyl Group] First, 9-decene-1
15.6 g of all (CH ₂ ＣＨCH (CH ₂ ) ₈ OH)
And perfluorooctyl iodide (F (CF ₂ ) ₈
I) 54.6 g was charged into a flask and nitrogen was bubbled.

Next, AIBN (2,2'-Azobis-isobutyr
Onitrile (0.05 g) was added, and the mixture was heated under reflux and reacted for 8 hours. After completion of the reaction, the raw materials are distilled off under reduced pressure,
F (CF ₂ ) ₈ CH ₂ CHI (CH ₂ ) ₈ OH as residue
Was obtained in an amount of 56 g.

Then, 56 g of F obtained as a residue were obtained.
(CF ₂ ) ₈ CH ₂ CHI (CH ₂ ) ₈ OH was dissolved in 400 cc of ethanol, and 40 cc of concentrated hydrochloric acid was added thereto, followed by heating. Then, 6 g of zinc powder was added little by little, and the mixture was refluxed for 2 hours. Further, 20 cc of concentrated sulfuric acid was added, and the mixture was refluxed for 1 hour. After completion of the reaction, the solution was filtered while it was still hot, and the obtained filtrate was concentrated.

Next, 200 cc of a 10% aqueous sodium hydroxide solution was added to the concentrated filtrate, followed by stirring to obtain a precipitate. Thereafter, the precipitate is filtered and dried to obtain F
37 g of (CF ₂ ) ₈ CH ₂ CH ₂ (CH ₂ ) ₈ OH were obtained.

Then, 37 g of F (CF ₂ ) ₈ CH ₂ CH ₂
(CH ₂ ) ₈ OH and 11 g of octadecylsuccinic acid were dissolved in 400 cc of toluene, concentrated sulfuric acid was added in a catalytic amount, and the mixture was refluxed for 3 hours.

Then, after allowing to cool, the reaction solution was washed with water, dried by adding magnesium sulfate, and concentrated. After removing the raw material by column chromatography (silica gel / toluene), the eluent was changed to ethyl acetate, and the desired product was collected. Finally, the ethyl acetate solution is concentrated to obtain a diester having a long-chain alkyl group and a partially fluorinated alkyl group as C ₁₈ H ₃₇ CH (COOC ₁₀ H ₂₀ C
₈ F ₁₇₎ to obtain 38g of _{CH 2 COOC 10 H 20 C 8} F 17. The diester having a long-chain alkyl group and a partially fluorinated alkyl group thus obtained is referred to as Compound 4.

By the same synthesis method as in the above-mentioned compound 4, the structure of the compound 4 is different from that of the compound 4. However, as diesters having a long-chain alkyl group and a partially fluorinated alkyl group, the four kinds of compound 1 shown in Table 1 below are used. ~ Compound 3 and Compound 5 were synthesized. Further, as lubricants other than diesters having a long-chain alkyl group and a partially fluorinated alkyl group, compounds 6 to 8 shown in Table 1 below were synthesized.
In Table 1, m, n, p, and q each represent an integer of 1 or more.

[0091]

[Table 1]

Next, a magnetic tape was manufactured as follows.

[Preparation of Sample Tape] <Example 1> First, Co was adhered to a film-like non-magnetic support made of polyethylene naphthalate having a thickness of 5.0 μm by oblique deposition to form a film as a magnetic layer. 80nm thick
Was formed.

Next, a DC voltage of -1.2 kV is applied to the raw material of the magnetic recording medium by using a high frequency plasma of a mixed gas of ethylene and argon as a counter electrode, and discharge is 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 is formed on the surface of the non-magnetic support opposite to the surface on which the metal magnetic thin film is formed. It was cut to 6.35 mm width.

Finally, a lubricant paint is prepared by dissolving Compound 1 as a lubricant in toluene at a ratio of 0.2 wt%, and this lubricant paint is uniformly applied on the protective film to form a lubricant layer. Then, a sample tape was obtained.

<Example 2> A sample tape was prepared in the same manner as in Example 1 except that Compound 2 shown in Table 1 was used as a lubricant.

<Example 3> A sample tape was prepared in the same manner as in Example 1 except that Compound 3 shown in Table 1 was used as a lubricant.

<Example 4> A sample tape was prepared in the same manner as in Example 1 except that Compound 4 shown in Table 1 was used as a lubricant.

<Example 5> A sample tape was prepared in the same manner as in Example 1 except that Compound 5 shown in Table 1 was used as a lubricant.

Comparative Example 1 A sample tape was prepared in the same manner as in Example 1 except that Compound 6 shown in Table 1 was used as a lubricant.

Comparative Example 2 A sample tape was prepared in the same manner as in Example 1 except that Compound 7 shown in Table 1 was used as a lubricant.

Comparative Example 3 A sample tape was prepared in the same manner as in Example 1, except that Compound 8 shown in Table 1 was used as a lubricant.

Comparative Example 4 A magnetic tape was produced in the same manner as in Example 1 except that no lubricant layer was formed.

For the sample tapes of Examples 1 to 5 and Comparative Examples 1 to 4 prepared as described above, the following various measurements were made immediately after completion of each sample tape, and The properties and durability were evaluated.

These series of measurements were carried out under the conditions of a temperature of 25.degree.
%, And a temperature of -5 ° C.

The running performance was evaluated by frictionally running the sample tape on a stainless steel guide pin for 100 passes in a thermostat controlled under the above-mentioned environmental conditions, and measuring the friction coefficient at the 100th pass of the friction running. went.

The evaluation of the shuttle durability was performed using a commercially available digital video camcorder (manufactured by Sony Corporation, model name: VX-1000) in a thermostat controlled under the above-mentioned environmental conditions. This was performed by repeating shuttle reproduction for two minutes and measuring the number of shuttles until the reproduction output decreased by 3 dB from the initial output.

In order to evaluate the durability, first,
A commercially available digital video camcorder (manufactured by Sony, model name: VX-1) is placed in a thermostat controlled under the above-mentioned environmental conditions.
000) was modified to enable the use of an MR head, and reproduction for 30 minutes was repeated 50 times for each sample tape. Next, MR after repeated running
The head was observed using an optical microscope, and the amount of 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 dropping was 50% or less of the head area and affected the output was Δ, and the level at which powder dropping exceeded 50% of the head area or clogging occurred during running was x.

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

The above measurement results are shown in Tables 2 and 3.

[0113]

[Table 2]

[0114]

[Table 3]

From Tables 2 and 3, it can be seen from Examples 1 to 3 that the lubricant layer containing the diester having the long-chain alkyl group and the partially fluorinated alkyl group represented by the structural formula (1) is formed on the protective film. The sample tape of Example 5 has a small friction coefficient and good shuttle durability under various use conditions such as high temperature and high humidity, high temperature and low humidity, and low temperature.
It was found that very good results were obtained in which powder dropping was prevented and head wear was small.

On the other hand, the sample tapes of Comparative Examples 1 to 3 using a lubricant other than the compound represented by the structural formula (1) have different coefficients of friction and shuttle durability under various use conditions. It was found that the MR head was deteriorated, powder falling was not prevented, and the MR head was greatly worn, and good results could not be obtained. It was also found that the sample tape of Comparative Example 4 having no lubricant layer did not provide good results under various use conditions. In particular, Comparative Examples 1 to 4
When the sample tape is used in an environment of -5 ° C, powder falls off on sliding members such as drums and fixed guides during shuttle running, and as a result, sticking phenomenon occurs and running becomes impossible. Was.

Therefore, by forming a lubricant layer containing a diester having a long-chain alkyl group and a partially fluorinated alkyl group represented by the structural formula (1) on the protective film as the uppermost layer, the lubricating layer can be formed under any usage conditions. It was also found that a magnetic recording medium was obtained in which the lubricating property was suitably maintained, powder generation was prevented, running performance and durability were excellent, and head wear and magnetic characteristics were prevented from deteriorating.

[0118]

As is apparent from the above description, in the magnetic recording medium according to the present invention, the lubricant layer containing a diester having a long-chain alkyl group and a partially fluorinated alkyl group represented by the following formula 4 is protected. Since it is formed on the film, it has excellent running properties and durability under any use conditions, and prevents head wear and deterioration of magnetic properties.

[0119]

Embedded image

[0120]

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing an example of a magnetic recording medium.

[Explanation of symbols]

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

Claims (1)

[Claims] 1. A magnetoresistive effect type comprising: a nonmagnetic support; a magnetic layer formed on the nonmagnetic support and made of a ferromagnetic metal material; and a protective film formed on the magnetic layer. In a magnetic recording medium used in a helical scan magnetic recording system using a reproducing head, a lubricant layer containing a diester having a long-chain alkyl group and a partially fluorinated alkyl group represented by the following formula 1 is formed on the protective film. A magnetic recording medium characterized by being performed. Embedded image