JPH10241136A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve running performance and durability of a magnetic recording medium and enhance reliability of a high density magnetic recording and reproducing system as a whole by including a compound of a particular glyceride structure into a lubricant agent layer. SOLUTION: A magnetic recording medium is formed by forming, to one main surface of a non-magnetic carrier, a metal thin film type magnetic recording layer, a hard carbon based protection layer and a lubricant agent layer 5 in this sequence. In this magnetic recording medium, the lubricant agent layer includes at least any one of the total weight of the compound having the glyceride structure indicated by expression I and a compound having the glyceride structure indicated by the expression II. However, in the expression I, R indicates saturated aliphatic alkyl group and at least a part of hydrogen in R may be replaced with fluorine. In the expression II, R' indicates unsaturated aliphatic alkyl group and at least a part of hydrogen in R' may be replaced with fluorine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal thin film type magnetic recording medium and a method of manufacturing the same, and more particularly, to a metal having a characteristic feature in a compound constituting a lubricant layer in order to obtain stable running and durability. The present invention relates to a thin-film magnetic recording medium and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a magnetic recording medium such as a magnetic recording tape used in a magnetic recording device associated with an audio device, a video device or a computer device, a thin film type and a coating type are mainly used. The thin film type sputters a ferromagnetic metal thin film such as Co on a non-magnetic support,
It is applied by a thin film forming technique such as vapor deposition or plating. Further, the coating type is formed by dispersing a magnetic powder, an organic binder and various additives in an organic solvent, applying a magnetic coating prepared by kneading, coating a non-magnetic support, drying and curing. This uses a magnetic recording layer.

In these various magnetic recording devices, in recent years, miniaturization and lightening, high image quality, long time, digital recording, and the like have progressed, and there has been a strong demand for high-density recording of magnetic recording media. It has become so. In order to meet this demand, in recent magnetic recording media, particularly metal thin film magnetic recording media, the surface of the magnetic recording layer is smoothed to a state close to a mirror surface, the gap between the magnetic head / magnetic recording layer is reduced, and the spacing is increased. There is a tendency to reduce losses as much as possible.

On the other hand, the magnetic recording tape runs while sliding on sliding members such as various guide pins due to its usage.
As an example, in the case of an 8 mm video tape recorder, a magnetic recording tape is wound around a magnetic drum through ten or more fixed guide pins made of stainless steel or the like, and a tape tension is about 20 g by a pinch roller, a capstan and a reel motor. , Running speed is 0.5cm / sec
The vehicle travels while being kept constant. In the running system of the magnetic recording tape recorder, when the frictional force between the sliding member and the magnetic recording tape increases, the magnetic tape causes tape squeal due to self-excited vibration called stick-slip, thereby causing distortion of the reproduction screen. In addition, the phenomenon of adhesion of the magnetic recording medium to the sliding member, that is, so-called sticking, is likely to occur. Further, since the relative speed between the magnetic head and the magnetic tape is as high as 3.8 m / sec, the durability, running property, and corrosion resistance are apt to be reduced due to friction and wear. As described above, the metal thin-film magnetic recording medium has problems to be solved in terms of running properties and durability.

In order to solve these problems, it is effective to provide a hard carbon-based protective layer, particularly a diamond-like carbon protective layer, on the surface of the metal thin film type magnetic recording layer in a mirror state. However, since this protective layer also causes a spacing loss between the magnetic head and the magnetic recording layer,
The thickness cannot be increased unnecessarily.
A thickness of 10 nm is employed. For this reason, it is difficult to obtain sufficient durability only with a carbon-based protective layer, and attempts have been made to provide a top coat layer. As the top coat layer, there is an example in which a fluorine-containing organic compound or a phosphorus-containing organic compound such as a phosphoric acid ester is formed by coating or vapor phase growth. As an example, a method in which a fluorine-containing carboxylic acid is vacuum-deposited on diamond-like carbon to a thickness of 3 to 4 nm is disclosed in JP-A-7-57254 and JP-A-6-1576-1.
No. 68436.

[0006]

However, it is expected that the smoothness of the surface of the magnetic recording layer will be required more in the future, and the durability under more severe driving conditions will be required. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a metal thin-film magnetic recording medium having a low coefficient of friction and stable running and durability, and a method of manufacturing the same.

[0007]

The magnetic recording medium of the present invention is proposed to solve the above-mentioned problems, and includes a metal thin film type magnetic recording layer on one main surface of a non-magnetic support, In a magnetic recording medium having a hard carbon-based protective layer and a lubricant layer in this order, the lubricant layer is composed of a compound having a glyceride structure represented by the following general formula (1) and a compound represented by the following general formula (2) Characterized in that it contains at least one of polymers of a compound having a glyceride structure.

Embedded image (However, in the general formula (1), R represents a saturated aliphatic alkyl group, and at least a part of hydrogen in R may be substituted with fluorine.)

Embedded image (However, in the general formula (2), R ′ represents an unsaturated aliphatic alkyl group, and at least a part of hydrogen in R ′ may be substituted with fluorine.)

Next, according to the method of manufacturing a magnetic recording medium of the present invention, a metal thin film type magnetic recording layer, a hard carbon-based protective layer, and a lubricant layer are formed in this order on one main surface of a nonmagnetic support. In the method for manufacturing a magnetic recording medium having a step of
The step of forming a lubricant layer includes a step of applying a lubricant containing at least a compound having a glyceride structure represented by the following general formula (1).

Embedded image (However, in the general formula (1), R represents a saturated aliphatic alkyl group, and at least a part of hydrogen in R may be substituted with fluorine.)

Another method for manufacturing a magnetic recording medium according to the present invention is as follows.
On one main surface of the non-magnetic support, a metal thin-film type magnetic recording layer,
In a method for manufacturing a magnetic recording medium having a step of forming a hard carbon-based protective layer and a lubricant layer in this order, the lubricant layer forming step has at least a glyceride structure represented by the following general formula (2). The method includes a step of applying a lubricant containing a compound and heat-treating the applied lubricant.

Embedded image (However, in the general formula (2), R ′ represents an unsaturated aliphatic alkyl group, and at least a part of hydrogen in R ′ may be substituted with fluorine.)

In the magnetic recording medium and the method of manufacturing the same according to the present invention, the carbon number in R in the general formula (1) and R ′ in the general formula (2) is determined by the ability to form a uniform thin film and the solvent of the coating solution. It is desirably 10 or more and 30 or less from the viewpoint of solubility or the like.

In the method for manufacturing a magnetic recording medium of the present invention, the thickness of the lubricant layer is not particularly limited, but is, for example, 0.2 nm or more and 3 nm or less. If the film thickness is less than 0.2 nm, sufficient durability and running stability cannot be obtained, and if it exceeds 3 nm, the durability also decreases, and the phenomenon of sticking to a magnetic drum or the like occurs. More preferably, the thickness of the lubricant layer is 0.5 nm or more and 1.5 nm or less.

The method of applying the lubricant is not particularly limited.
Various coating methods such as gravure coating and dip coating are applied. In the case of a compound having a glyceride structure having an unsaturated aliphatic alkyl group containing a double bond or a triple bond, it is desirable to have a step of heating in an oxidizing atmosphere such as air after applying this lubricant. . By this heat treatment, the polymerization reaction proceeds with oxidation, and a tough and durable lubricant layer is obtained. The heat treatment temperature is not particularly limited, but is not lower than the temperature at which oxidative polymerization is promoted, and is not higher than the temperature range at which the nonmagnetic support or the like is not thermally degraded, for example, 50 ° C to 120 ° C, preferably 55 ° C to 1 ° C.
00 ° C. or less is employed.

The hard carbon-based protective layer is made of diamond-like carbon (DLC).
arbon) is desirable. Diamond-like carbon is
As an example, chemical vapor deposition (CVD; Chemica)
l Vapor Deposition and physical vapor deposition (PVD) such as sputtering.
It can be formed by a Vapor Deposition method. The carbon-based protective layer may be formed as a single layer, or may be formed as a multilayer by providing another material below. Such other materials include SiO ₂ , Si ₃ N ₄ ,
SiON, SiC, Al ₂ O ₃ , AlN, TiO ₂ , C
r ₂ O ₃ , TiN, TiC, ZrO ₂ , MgO, BN,
CoO or a non-magnetic metal is exemplified.

As the non-magnetic support for forming the metal thin-film type magnetic recording layer, any of those used in ordinary thin-film type magnetic recording media can be used, such as polyethylene terephthalate and polyethylene-2,6-naphthalate. Polyolefins such as polyesters, polyethylene, and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; vinyl resins such as polyvinyl chloride; vinylidene resins such as polyvinylidene chloride; and organic polymers such as polycarbonate, polyamideimide, and polyimide. Molecules are exemplified. A base material layer made of an organic binder may be provided on the surface of the nonmagnetic support to improve the adhesiveness. Further, a filler such as SiO ₂ or latex may be contained in the base material layer or the non-magnetic support to form fine surface projections. These surface protrusions control the surface properties of the metal magnetic thin film and contribute to improving the running properties of the magnetic recording tape. Further, in the case of a magnetic recording medium such as a hard disk, a rigid substrate such as an Al-based metal, ceramics, or glass can be used as a nonmagnetic support.

The metal thin film type magnetic recording layer is formed by forming a ferromagnetic metal on a nonmagnetic support by a thin film forming technique such as vapor deposition, sputtering or plating. As the material of the ferromagnetic metal, a simple ferromagnetic metal such as Co, Fe or Ni, a Co-Ni alloy, a Co-Ni-Pt alloy, a Co-Cr alloy, a Co-Cr-Ta alloy, a Co-C
Co-based alloys such as r-Pt alloys, Fe-Co-Ni alloys,
Fe-Ni-B alloy, Fe-Co-B alloy, Fe-Co
Examples thereof include Fe-based alloys such as -Ni-B alloys, and those having a structure in which oxides, nitrides, carbides, and the like are precipitated in these ferromagnetic materials and at grain boundaries. In particular, in a thin-film magnetic recording medium using an in-plane magnetization mode, a magnetic layer is formed on the surface of a non-magnetic support by oblique deposition or the like, and the axis of easy magnetization is oriented substantially in the plane of the magnetic layer. Bi, Sb, P on non-magnetic support
A non-magnetic underlayer such as b, Sn, Ga, In, Ge, Si, or Ti may be formed, and a ferromagnetic metal may be deposited or sputtered on the non-magnetic underlayer in a direction perpendicular to the surface of the non-magnetic support. By interposing such a nonmagnetic underlayer, the nonmagnetic metal is diffused into the magnetic layer, the morphology of the magnetic layer is controlled to impart in-plane isotropic magnetization, and the coercive force is improved. be able to. The metal thin film type magnetic recording layer is used as a single layer or a multilayer. In the case of lamination, a non-magnetic layer may be interposed as an intermediate layer.

A coating type or thin film type back coat layer may be provided on the other surface of the non-magnetic support. The configuration of the back coat layer is not particularly limited. The coating back coat layer is a dispersion of non-magnetic particles in an organic binder,
Examples of the material of the nonmagnetic particles include hematite, boehmite, fused alumina, various aluminas such as α, β, γ-alumina, mica, kaolin, talc, clay, silica, magnesium oxide, titanium oxide (rutile and anatase),
Inorganic compounds such as zinc oxide, zinc sulfide, calcium carbonate, magnesium carbonate, barium carbonate, barium sulfate, lead sulfate, and tungsten sulfide; polymer resins such as polyethylene, polyvinyl chloride, polyimide, and polytetrafluoroethylene; starch; or Non-magnetic metals and the like are exemplified. The non-magnetic particles have an average particle size of 0.05 to 1 μm, preferably 0.1 to 0.7 μm,
It is usually added in the range of 1 to 20 parts by weight based on 100 parts by weight of the organic binder. Further, from the viewpoint of paint suitability and durability, it is preferable that the particles have an isotropic shape such as a substantially spherical shape and a substantially regular polyhedron.

The organic binder material used for the coating backcoat layer is not particularly limited, but any of conventionally used thermoplastic resins, thermosetting resins, and reactive resins can be used. It is desirable that the thermoplastic resin be used in combination with a thermosetting resin, a reactive resin, or the like. The resin preferably has an average molecular weight of 5,000 to 200,000, and 10,000.
To 100,000 are more preferred. As the thermoplastic resin, for example, vinyl chloride resin, vinyl acetate resin, vinyl fluoride resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, Vinyl chloride-acrylonitrile copolymer, vinylidene chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinyl chloride-
Vinylidene chloride copolymer, methacrylic acid ester-vinyl chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-ethylene copolymer, acrylonitrile-butadiene copolymer, styrene-butadiene copolymer, polyurethane Resin, polyester polyurethane resin, polyester resin, polycarbonate polyurethane resin, polycarbonate resin, polyamide resin, polyvinyl butyral resin, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butadiene Copolymers, polyester resins, amino resins, various synthetic rubbers and the like can be mentioned. Examples of thermosetting resins and reactive resins include phenolic resins, epoxy resins,
Polyurethane curing resin, urea formaldehyde resin,
Melamine resin, alkyd resin, silicone resin, polyamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of polyester polyol and polyisocyanate, mixture of low molecular weight glycol, high molecular weight diol and isocyanate, and the mixture of these resins Is exemplified. Among these resins, it is preferable to use a polyurethane resin, a polycarbonate resin, a polyester resin, an acrylonitrile-butadiene copolymer, which is considered to impart flexibility. These resins are
In order to improve the dispersibility of non-magnetic particles, -SO ₃ M, -O
SO ₃ M, —COOM, or —PO (OM ′) ₂
(Where M represents H or an alkali metal such as Li, Ka, or Na, and M ′ represents H or an alkali metal such as Li, Ka, or Na, or an alkyl group). Other polar functional groups include -NR ₁ R
₂ , -NR ₁ R ₂ R ₃ ⁺ X ⁻ side chain type having a terminal group, and> NR ₁ R ₂ ⁺ X ⁻ main chain type (here, R ₁ , R ₂ , R ₃ is a hydrogen atom or a hydrocarbon group, X ^- represents fluorine, chlorine, bromine, halogen ion or an inorganic iodine, the organic ions). In addition, a polar functional group such as —OH, —SH, —CN, or an epoxy group may be used. The content of these polar functional groups is 10 ^-1 to 1
0 ^-8 mol / g, preferably 10 ^-2 to 10 ^-6 mo
1 / g. These organic binders can be used alone or in combination of two or more. The amount of these organic binders in the applied back coat layer is 1 to 200 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the nonmagnetic particles.

As a curing agent for crosslinking and curing the above-mentioned organic binder, for example, polyisocyanate or the like can be added. As the polyisocyanate, an adduct of trimethylolpropane and 2,4-tolylene diisocyanate (TDI) (for example, trade name Coronate L-5)
Although 0) is generally used, an adduct of an alkylene diisocyanate such as 4,4-diphenylmethane diisocyanate (MDI) or hexane diisocyanate (HDI) may be used. In addition, polyglycidylamine compounds such as tetraglycidyl metaxylenediamine, tetraglycidyl-1,3-bisaminomethylcyclohexane, tetraglycidylaminodiphenylmethane, triglycidyl-p-aminophenol, and 2-dibutylamino-
Polythiol compounds such as 4,6-dimercapto-substituted triazines, epoxy compounds such as triglycidyl isocyanurate, mixtures of epoxy compounds and isocyanate compounds, mixtures of epoxy compounds and oxazoline compounds,
A mixture of an imidazole compound and an isocyanate compound,
Any conventionally known compounds such as methylnadic anhydride can be used. The mixing ratio of these curing agents to the organic binder is 5 to 80 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the organic binder.

A lower coating backcoat layer may be formed between the coating backcoat layer and the nonmagnetic support for the purpose of improving the adhesiveness of the coating backcoat layer. The lower coating backcoat layer is formed by dissolving an organic binder alone or a carbon powder and, if necessary, other nonmagnetic powder and an organic binder in a solvent to form a coating, coating this on a nonmagnetic support, and drying. Is done.

Solvents used in the coating for forming the coating backcoat layer include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, alcohols such as methanol, ethanol, propanol and butanol, methyl acetate, ethyl acetate, and the like. Esters such as propyl acetate, butyl acetate, ethyl lactate, ethylene glycol monoacetate, ethers such as diethylene glycol dimethyl ether, glycol monoethyl ether, dioxane, tetrahydrofuran, aromatic hydrocarbons such as benzene, toluene, xylene, methylene chloride, ethylene Halogenated hydrocarbons such as chloride, carbon tetrachloride, chloroform and dichlorobenzene are used.

The coating method for forming the coating back coat layer on the non-magnetic support is not particularly limited, and may be air doctor coat, blade coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, gravure Any of the conventional methods such as coat, kiss coat, cast coat, extrusion coat, and spin coat can be adopted. The coated back coat layer formed on the non-magnetic support is dried with heated air or the like to remove the organic solvent, and is subjected to a curing treatment if necessary.

Materials used for the thin film back coat layer include, for example, carbon, graphite, diamond-like carbon, SiO ₂ , Si ₃ N ₄ , SiON, SiC,
Al ₂ O ₃ , AlN, TiO ₂ , Cr ₂ O ₃ , TiN,
TiC, ZrO ₂ , MgO, BN, CoO, a nonmagnetic metal, or the like is used alone or as a composite film. Further, an organic polymer to which a vacuum thin film forming technique can be applied, such as polyparaxylylene (trade name: parylene) or fluororesin, can also be used. These materials may be used in a single layer or a laminate.

The thin film back coat layer can be formed by various sputtering methods such as a vacuum thin film forming method, ie, DC sputtering method, RF sputtering method, ion beam sputtering method, magnetron sputtering method, reactive sputtering method, vapor deposition method, and reactive sputtering method. An evaporation method, an ion plating method, or the like is employed. Plasma CVD or E
A CR plasma CVD method, a reduced pressure CVD method, or the like may be employed. In the case of an organic polymer thin film, it can be formed by an evaporation method or plasma polymerization of a raw material gas. In either method, it is desirable to form the non-magnetic support and the like while cooling the non-magnetic support and the like so as not to thermally deform the non-magnetic support and the coating backcoat layer provided thereon.

A lubricant layer may be formed on these back coat layers. Above all, when a thin film-type back coat layer, particularly a diamond-like carbon is adopted, a magnetic recording medium having stable running properties and durability can be provided by providing a lubricant layer containing the compound having a glyceride structure of the present invention on this surface. Can be obtained.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic recording medium of the present invention and the method of manufacturing the same will be described in detail with reference to a metal thin film type magnetic recording tape using Co metal for a magnetic recording layer as an example and comparative examples. Add.

First, FIG. 1 shows a schematic sectional view of an example of the magnetic recording medium of the present invention. On one surface of the nonmagnetic support 1, an undercoat layer 2, a metal thin-film magnetic recording layer 3, a hard carbon-based protective layer 4, and a lubricant layer 5 are formed. A back coat layer 6 is formed on the other surface of the non-magnetic support 1 to form a metal thin film magnetic tape for digital video cassettes.

Next, an example of a method for manufacturing the magnetic recording medium shown in FIG. 1 will be described. PE with a thickness of 7 μm and a width of 150 mm
An emulsion solution in which a water-soluble latex containing an acrylate ester as a main component is dispersed is applied to one surface of a nonmagnetic support 1 made of a T (polyethylene terephthalate) film, and surface protrusions having a particle density of 10 ⁷ / mm ² are formed. An undercoat layer 2 having the same was formed. Next, the metal thin film type magnetic recording layer 3 was formed on the undercoat layer 2 by using a reel-to-reel continuous winding deposition apparatus. An example of the evaporation conditions is shown below. Ingot for vapor deposition: pure cobalt Incident angle 45 to 90 ° Traveling speed 0.17 m / sec Oxygen introduction amount 3.3 to 4.0 × 10 ⁻⁶ m ³ / sec Vacuum degree during vapor deposition 7 × 10 ⁻² Pa film Thickness: 200 nm The magnetic characteristics of the metal thin-film type magnetic recording layer 3 are determined by introducing coercive force Hc = 110 k by introducing oxygen into the deposition chamber.
A / m and residual magnetic flux density Br were adjusted to 0.45T.

Next, a back coat layer 6 was formed on the other surface (back surface) of the PET film. The paint for the back coat layer 6 had the following composition as an example. 100 parts by weight of carbon particles (Carbon black # 60 manufactured by Asahi Carbon Co.) 100 parts by weight of organic binder (mainly composed of polyurethane) Solvent 250 parts by weight (methyl ethyl ketone / toluene / cyclohexanone =
2/2/1) This composition was mixed with a ball mill, and 5 parts by weight of a curing agent (Coronate L) was added immediately before coating. This paint was applied by a gravure coater so that the dry coating thickness was 0.6 μm.

Next, a hard carbon-based protective layer 4 was formed on the metal thin film type magnetic recording layer 3. FIG. 2 shows an example of a CVD apparatus for forming the hard carbon-based protective layer 4 using a plasma CV.
1 shows a schematic sectional view of a device D. A web 11 having an undercoat layer 2, a metal thin-film type magnetic recording layer 3 formed on one side of a non-magnetic support 1, and a back coat layer 6 formed on the other side is supplied from an unwinding roll 13, and is supplied to a guide roll. The film is run via the film forming roll 19, the film forming roll 19 and the guide roll 12, and is wound on a winding roll 14. A reaction tube 15 having an upper opening is provided on the entire length of the film forming roll 19 in the axial direction. A gas inlet 18 is connected to a lower portion of the reaction tube 15, and a reaction gas mainly composed of a hydrocarbon-based gas is introduced from the gas inlet 18. +5 from the DC power supply 17
A mesh-shaped electrode 16 to which a DC voltage of 00 to 2000 V is applied is housed, and a film-forming roll 19 having a ground potential is provided.
A plasma of a hydrocarbon-based gas is generated between the substrate and the carbon-based protective layer on the surface of the running target web 11. These components are housed in a vacuum chamber 22, and the inside of the chamber can be controlled to a desired degree of vacuum by an exhaust system 21.

A hard carbon protective layer 4 was formed on the previously formed metal thin film type magnetic recording layer 3 by the plasma CVD apparatus shown in FIG. An example of the plasma CVD conditions is shown below. Introduced gas: toluene diluted with carrier gas Reaction pressure 10 Pa DC voltage 1.5 kV Carbon-based protective layer thickness 10 nm A long sample having the hard carbon-based protective layer 4 formed as described above was prepared and lubricated. Example 1 by applying the agent layer 5
5 and Comparative Examples 1 and 2 were manufactured.

Example 1 Among the compounds having a glyceride structure represented by the general formula (1), those in which R = C ₁₇ H ₃₅ (stearyl group) are dissolved in toluene at a concentration of 1.0% by weight to form a coating solution. Was prepared and applied on the hard carbon-based protective layer 4 by a direct gravure method. In the drying process after coating,
A heating step was added by a dryer under a temperature condition of 70 ° C. The long sample on which the lubricant layer 5 was formed was cut into a 6.35 mm width, and then housed in a cassette to complete the magnetic recording medium of Example 1.

Example 2 As a compound having a glyceride structure represented by the general formula (1), a saturated partially fluorinated alkyl group represented by R = (CH ₂ ) ₁₀ (CF ₂ ) ₉ CF ₃ was employed.
The magnetic recording medium of Example 2 was manufactured according to Example 1 described above.

Example 3 As a compound having a glyceride structure represented by the general formula (2), R ′ = (CH ₂ ) ₇ CH ＝ CHCH ₂ CH ＝ CH (C
A magnetic recording medium of Example 3 was manufactured in accordance with Example 1 except that an unsaturated aliphatic alkyl group represented by H ₂ ) ₄ CH ₃ was employed.

Example 4 As a compound having a glyceride structure represented by the general formula (2), R ′ = (CH ₂ ) ₇ CH ＝ CHCH ₂ —CH ＝ CH—
A magnetic recording medium of Example 4 was manufactured in accordance with Example 1 except that an unsaturated aliphatic alkyl group represented by CH ₂ CH ＝ CHCH ₂ CH ₃ was employed.

Example 5 Among the compounds having a glyceride structure represented by the general formula (1), R = C ₁₇ H ₃₅ (stearyl group) and the compound having a glyceride structure represented by the general formula (2) include R '= (CH ₂ ) ₇ CH = CHCH ₂ -CH = CH--
The magnetic recording medium of Example 5 was modified in accordance with Example 1 except that a mixture of unsaturated aliphatic alkyl groups represented by CH ₂ CH = CHCH ₂ CH ₃ at a weight ratio of 1: 1 was employed. Manufactured.

Comparative Example 1 A magnetic recording medium of Comparative Example 1 was manufactured in accordance with Example 1 except that a commercially available perfluoropolyether was used as a lubricant.

Comparative Example 2 As a compound having a glyceride structure represented by the general formula (2), R ′ = (CH ₂ ) ₇ CH ＝ CHCH ₂ CH ＝ CH (C
An unsaturated aliphatic alkyl group represented by H ₂ ) ₄ CH ₃ is employed, and is dissolved in toluene at a concentration of 1.0% by weight to prepare a coating solution. The coating solution is formed on the hard carbon-based protective layer 4 by a direct gravure method. Applied. In the drying step after the application, air drying was performed under a temperature condition of 20 ° C. The long sample on which the lubricant layer 5 was formed was cut into a 6.35 mm width, and then housed in a cassette to complete the magnetic recording medium of Comparative Example 2.

For each of the seven types of magnetic recording media of each of the examples and comparative examples, a commercially available DVC camcorder (VCR manufactured by Sony Corporation) was used.
X-1000). Evaluation items are
There are three items: coefficient of friction, still characteristics, and shuttle characteristics. Hereinafter, the measurement evaluation method of each measurement item will be described.

Measurement of Coefficient of Friction FIG. 3 shows an outline of the measuring device. A guide pin D made of stainless steel is disposed horizontally, and the lubricant layer 5 side of the magnetic recording medium P is guided on the outer peripheral surface over an angle θ. A weight W is engaged with one end of the magnetic recording medium P, and a tension T1 is applied by the weight W. The other end of the magnetic recording medium P is engaged with a detecting end of a force measuring device M that moves at a constant speed V, and a tension T when the guide pin D slides on the magnetic recording medium P.
Perform the measurement of 2. At this time, the following relationship holds. T2 / T1 = exp (μ · θ) From this equation, the friction coefficient μ is obtained from the following equation. μ = (1 / θ) ln (T2 / T1) The actual measurement was performed in a constant temperature and high humidity chamber at 40 ° C. and 80% atmosphere.
Regarding the magnetic recording medium after the shuttle travel 00 times,
The measurement was performed under the measurement conditions of 25 ° C. and 50% RH under the conditions of W = 10 gf, θ = 90 °, and V = 20 mm / sec.

Shuttle Measurement After running the shuttle 200 times with an 8 mm VTR tester in a measurement evaluation environment of 40 ° C. and 80% RH, the reproduced output was compared with the initial reproduced output.

Still Measurement Still reproduction was performed in a thermostatic oven controlled at -5 ° C., and the time required for the reproduction output to drop by 3 dB from the initial reproduction output was measured.

The results of the above measurements are summarized in Table 1.

[0043]

[Table 1]

As is clear from Table 1, in Examples 1 and 2, all the evaluation items were improved by employing a compound having a glyceride structure having a saturated alkyl group or a partial fluoride thereof in the lubricant layer. However, it has a great effect on reducing the dynamic friction coefficient. In Examples 3 and 4, all evaluation items were improved by adopting a polymer of a compound having a glyceride structure having an unsaturated aliphatic alkyl group. Particularly, still and shuttle durability were improved. Has a great effect on the improvement of Further, in the case of the magnetic recording medium of Example 5, a great improvement is seen in any of the evaluation items due to the synergistic effect of both compounds.

On the other hand, the magnetic recording medium of Comparative Example 1 employing perfluoropolyether has a certain effect, but has not reached a satisfactory level. The magnetic recording medium of Comparative Example 2 uses the same compound having a glyceride structure having an unsaturated alkyl group as the lubricant as the lubricant of Example 3, but the evaluation result is divided by the presence or absence of heat treatment during drying. This is presumed to be due to the formation of a tough and durable lubricant layer due to the promotion of polymerization accompanying oxidation during the heat treatment.

Although the magnetic recording medium of the present invention and the method of manufacturing the same have been described above in detail, these are merely examples, and the present invention is not limited to these embodiments.

For example, in addition to the glyceride compounds used in the examples, glyceride compounds having various saturated aliphatic alkyl groups and unsaturated aliphatic alkyl groups can be used.

In this embodiment, pure Co is used as the magnetic recording medium.
The magnetic recording layer made of Co-20% N
It can be applied to thin-film magnetic recording tapes having various alloy compositions such as i. Also, a hard disk type magnetic recording medium employing an Al-based metal, glass, ceramics, or the like as a non-magnetic support also has the durability of the magnetic recording layer.
SS (Contact Start and Sto)
p) It is possible to improve characteristics and reduce head crash and the like.

[0049]

As is apparent from the above description, according to the magnetic recording medium and the method of manufacturing the same of the present invention, the running property and durability of the magnetic recording medium can be reduced by using a compound having a specific structure in the lubricant layer. Can be improved. Therefore, by employing such a magnetic recording medium, the reliability of the entire high-density magnetic recording / reproducing system can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example in which a magnetic recording medium of the present invention is applied to a magnetic recording tape.

FIG. 2 is a schematic sectional view showing an example of a plasma CVD apparatus.

FIG. 3 is a diagram schematically showing a measurement device for a coefficient of friction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic support, 2 ... Undercoat layer, 3 ... Metal thin film type magnetic recording layer, 4 ... Hard carbon type protective layer, 5 ... Lubricant layer, 6
… Back coat layer, 11… web to be processed, 12… guide roll, 13… unwind roll, 14… take-up roll, 15… reaction tube, 16… electrode… 17… DC power supply
... gas inlet, 19 ... film forming roll, 21 ... exhaust system, 22
… Vacuum chamber

Claims (8)

[Claims] 1. A magnetic recording medium having a metal thin film type magnetic recording layer, a hard carbon-based protective layer, and a lubricant layer in this order on one main surface of a non-magnetic support, wherein the lubricant layer comprises: A magnetic recording medium comprising at least one of a compound having a glyceride structure represented by the following general formula (1) and a polymer of a compound having a glyceride structure represented by the following general formula (2) . Embedded image (However, in the general formula (1), R represents a saturated aliphatic alkyl group, and at least a part of hydrogen in R may be substituted with fluorine.) (However, in the general formula (2), R ′ represents an unsaturated aliphatic alkyl group, and at least a part of hydrogen in R ′ may be substituted with fluorine.) 2. The magnetic recording medium according to claim 1, wherein the number of carbon atoms in R and R ′ is 10 or more and 30 or less. 3. The magnetic recording medium according to claim 1, wherein the hard carbon-based protective layer is made of diamond-like carbon. 4. A method for manufacturing a magnetic recording medium, comprising the steps of forming a metal thin-film type magnetic recording layer, a hard carbon-based protective layer, and a lubricant layer on one main surface of a nonmagnetic support in this order. The method of manufacturing a magnetic recording medium, wherein the step of forming a lubricant layer includes a step of applying a lubricant containing at least a compound having a glyceride structure represented by the following general formula (1). Embedded image (However, in the general formula (1), R represents a saturated aliphatic alkyl group, and at least a part of hydrogen in R may be substituted with fluorine.) 5. The method according to claim 4, wherein the number of carbon atoms in R is 10 or more and 30 or less. 6. A method for manufacturing a magnetic recording medium, comprising the steps of forming a metal thin film type magnetic recording layer, a hard carbon-based protective layer, and a lubricant layer on one main surface of a nonmagnetic support in this order. The method of manufacturing a magnetic recording medium, wherein the step of forming the lubricant layer includes a step of applying at least a compound having a glyceride structure represented by the following general formula (2) and performing a heat treatment. Embedded image (However, in the general formula (2), R ′ represents an unsaturated aliphatic alkyl group, and at least a part of hydrogen in R ′ may be substituted with fluorine.) 7. The method according to claim 6, wherein the number of carbon atoms in R ′ is 10 or more and 30 or less. 8. The step of forming the hard carbon-based protective layer is a step of forming diamond-like carbon by one of a chemical vapor deposition method and a physical vapor deposition method. 7. The method for producing a magnetic recording medium according to 4 or 6.