JP2805374B2 - Magnetic recording medium and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having a magnetic layer provided on a non-magnetic support and a method for producing the same, and more particularly, to magnetic recording in which a lubricant and a surface treatment are combined. The present invention relates to a medium and a method for manufacturing the medium.

[Conventional technology and its problems]

Recently, with the spread and generalization of devices such as VTRs, the demand for higher performance and higher characteristic recording has increased in magnetic recording media, and various materials have been improved, such as ferromagnetic powder, binders, etc. Or additives such as abrasives, lubricants, antistatic agents, etc., or improvements in production methods, for example, kneading methods, coating methods, and surface treatment methods.

In particular, it is known to lubricate the surface of the magnetic layer to improve the durability of the magnetic layer and reduce the wear of the magnetic head.

Further, the magnetic layer is a solvent, a binder, a ferromagnetic powder,
Not only the magnetic layer of the coating type magnetic recording medium formed by applying a magnetic paint in which additives are dispersed on a non-magnetic support but also a metal thin film provided by vapor deposition on the non-magnetic support may be used. Ferromagnetic thin-film magnetic recording media having a metal thin film have also been developed as next-generation media.

As a method of using the lubricant, a method of adding a lubricant to a magnetic layer coating solution, a method of applying a lubricant to the surface of a magnetic layer, and the like are known.

As a lubricant, a mineral oil, a silicone oil, a higher alcohol, a higher fatty acid, a fatty acid ester, a tallow, a whale oil, an animal oil such as a shark oil or a vegetable oil has been used.

For example, Japanese Patent Publication No. 41-18065 discloses that a fatty acid ester composed of a monobasic fatty acid having 2 to 18 carbon atoms (excluding the carbon atom of the carboxy group) and a monohydric alcohol having 14 or more carbon atoms has a binder content of 100% by weight. JP-A-54-124716 discloses an abrasive having a Mohs hardness of 6 or more, n-butyl stearate, dodecyl stearate, propyl palmitate. Coated magnetic recording media having higher fatty acid esters such as
JP-A-55-157131 discloses a magnetic recording medium having a higher fatty acid ester such as isocetyl stearate and isocetyl palmitate, and JP-A-59-186130 discloses a coating having an isocetyl stearate. Patent Document 1 discloses a magnetic recording medium of any type, which is said to be effective in improving the durability of a magnetic layer and suppressing head wear.

Further, U.S. Pat.No. 4,303,738 also discloses a coating type magnetic recording medium using tridecyl stearate, and the durability of the tape is superior to esters such as butoxyethyl stearate and isocetyl stearate. ,
It is described that the head abrasion is improved.

It is not easy to compare which of the lubricants disclosed in the above documents is the best lubricant. This is because the composition systems of the magnetic layers holding the lubricant are different from each other.

However, in general, what can be said about magnetic recording media in general is that when these lubricants are increased, the lubricating effect is usually increased, head wear is suppressed, and electromagnetic conversion characteristics are improved, but the mechanical strength of the magnetic coating film is increased. It weakens and reduces the durability of the coating, increasing dropout. Conversely, when the amount of the lubricant is reduced, the dropout is reduced, but there is a problem that the head wear is accelerated and the electromagnetic conversion characteristics are deteriorated.

On the other hand, as a measure to improve the durability of the magnetic layer,
For example, a method of adding a non-magnetic inorganic powder such as an abrasive (hard particles) to a magnetic layer has been proposed and implemented. However, unless a considerably large amount is added, the effect of the addition is difficult to appear and sacrifices head wear. Heads are likely to be clogged due to removal of abrasives, shavings, etc., and dropouts are likely to occur due to protrusions on the surface of the magnetic layer. In order to eliminate the adverse effects caused by the surface properties of the magnetic layer, various surface treatment means have been applied to the surface of the magnetic layer to improve the surface properties of the magnetic layer surface.

For example, JP-A-1-201824 discloses that the surface of a magnetic layer of a coating type magnetic recording medium containing α-alumina as a polishing agent and butyl stearate as a lubricant is mirror-finished with a super calendar, and then has a high hardness. Discloses a method of performing a polishing treatment by using a polishing wheel, and it is described that dropout is reduced and skew fluctuation is improved.

JP-A-2-23521 also discloses that a magnetic layer surface of a coating type magnetic recording medium containing the same abrasive and lubricant as the above-mentioned publication is mirror-finished, and then a high-hardness grinding wheel such as diamond is used. Discloses a method of performing a polishing treatment by using the method described above, in which dropout is reduced, steel is improved, head wear is reduced, and damage to the magnetic layer is improved.

Further, as described in JP-A-63-259830, the present applicant also applied a polishing tape after subjecting a magnetic layer of a magnetic recording medium containing the same abrasive and lubricant as described above to mirror finishing using a super calendar. In this method, the durability of the magnetic layer, the dropout of the magnetic layer, and the clogging of the head have been improved by a method of polishing with a high-hardness blade or a rotating blade as necessary.

However, in the magnetic recording medium manufactured as described above, a problem has occurred in that electromagnetic conversion characteristics, particularly, Y S / N are deteriorated.

Therefore, if a new lubricant must be developed or a new binder must be developed and used to improve this problem, it is difficult to provide a magnetic recording medium at low cost. there were.

That is, it is ultimately difficult to obtain the durability of the magnetic layer using a conventionally known lubricant without sacrificing the electromagnetic conversion characteristics and head wear.

Therefore, the present inventor considers that the surface treatment of the magnetic layer is indispensable, and that if a super-hard material is used for this, the adverse effects due to surface properties can be improved to some extent even if other elements are ignored. Recognizing that the most necessary element for processing is a lubricant, re-examining the selection of this lubricant as a dependent element, and as a result of diligent examination, the present invention was found. Not a combination.

[Object of the invention]

That is, an object of the present invention is to provide a magnetic recording medium having good Y S / N characteristics in which dropout is reduced and head wear is suppressed / improved.

[Means for solving the problem]

An object of the present invention is to provide a magnetic recording medium in which a magnetic layer is provided on a nonmagnetic support, wherein the magnetic layer has the following general formula (I)
A magnetic recording medium containing a higher fatty acid ester having 24 or more carbon atoms represented by, and wherein the dried surface of the magnetic layer is subjected to a surface treatment with a superhard material, ^{R 1 COOR 2 ··· (I)} ( wherein, R ¹ represents a hydrocarbon group having 14 to 35 carbon atoms, R ² represents a branched alkyl group having 4 to 30 carbon atoms, and the number of carbon atoms in R ¹ The sum of the number of carbon atoms of R ^{2 and} the number of carbon atoms is 23 or more.) In the method for producing a magnetic recording medium having a magnetic layer provided on a non-magnetic support, after forming the magnetic layer on the non-magnetic support, A method for subjecting a dried surface of a magnetic layer to a surface treatment with a material, wherein the higher fatty acid ester is contained in the magnetic layer at least one of before and after the surface treatment. This is achieved by a method of manufacturing a medium.

The present invention provides a branched alkyl ester of higher fatty acids having 24 or more carbon atoms as described above (hereinafter, referred to as the compound of the present invention).
While containing an appropriate amount in the magnetic layer, the physical properties of the magnetic layer obtained by subjecting the magnetic layer to surface treatment with a super hard material, such as surface roughness, surface free energy, etc. It is presumed that, in harmony, dropout is reduced and head wear is suppressed to improve YS / N. That is, the surface treatment with the super hard material in the present invention can be realized only by selecting the compound of the present invention from known lubricants.

In the present invention, to contain the compound of the present invention in the magnetic layer, the compound of the present invention only inside the magnetic layer, only the surface,
It is meant to include the presence at only the slit end and both or all of them.

The treatment of the dried surface of the magnetic layer using the superhard material, which is performed in the present invention, may be performed after the compound of the present invention is contained in the magnetic layer, before, or both.

In the present invention, as a magnetic recording medium having a magnetic layer to which the compound of the present invention can be applied, typically, a binder such as a resin is dissolved in an organic solvent together with a ferromagnetic powder and coated on a non-magnetic support. (Hereinafter abbreviated as a coating type magnetic recording medium) or a magnetic layer provided with a metal thin film on a non-magnetic support by vapor deposition or the like (hereinafter abbreviated as a metal thin film type magnetic recording medium). The metal thin film may be any of those known in the art, and is not particularly limited, and includes those obtained by physically or chemically treating the surface of the metal thin film.

In the present invention, a non-magnetic layer (hereinafter, referred to as a back layer) can be provided on the other surface of the non-magnetic support on which the magnetic layers of both types of magnetic recording media are provided. In particular, when a back layer is provided, the present invention is effective for reducing dropout.

As a method of including the compound of the present invention in the magnetic layer,
A method of adding the compound of the present invention to a magnetic layer and a method of applying a top coat on the surface (a method of dissolving the compound of the present invention in an organic solvent and applying or spraying the solution on a substrate, followed by drying; A method in which a substrate is immersed in a solution in which the compound of the present invention is dissolved in an organic solvent to allow the material to be adsorbed on the substrate surface, a Langmuir-Blodgett method or the like), a method using both of them, and the like.

The amount of the compound of the present invention added to the coating type magnetic recording medium is as follows:
The binder resin to be used, the type of the ferromagnetic powder, and the like are appropriately selected depending on the amount used. Similarly, the addition amount of the compound of the present invention to the metal thin-film magnetic recording medium is appropriately selected depending on the surface condition of the metal thin film. However, usually, it can be selected from the following range.

The content of the compound of the present invention is 0.1 to 3.0 g, preferably 1.5 to 2.5 g, per 100 parts by weight of the ferromagnetic powder in the coating type magnetic recording medium. In the case of a metal thin film type magnetic recording medium, the amount is 0.1 to 3.0 g, preferably 0.5 to 1.5 g, per 100 parts by weight of the metal thin film.

If the amount used exceeds this range, the compound of the present invention present on the surface becomes excessive, which may cause sticking and failure such as moisture absorption. However, there is a problem that the durability is rather lowered due to the action of plasticizing the binder and the like.

If the amount used falls below this range, the surface amount is naturally insufficient and the effect cannot be obtained.

The compound of the present invention can be represented by the following formula (I).

R ¹ COOR ² (I) wherein R ¹ is a hydrocarbon group having 14 to 35 carbon atoms, preferably an aliphatic hydrocarbon group, more preferably a straight-chain alkyl group, for example, Octadecyl group, hexadecyl group,
Tetradecyl group, heptadecyl group, nanodecyl group, tetracosyl group, hexacosyl group, octacosyl group, etc., R
² is a branched alkyl group having 4 to 30 carbon atoms, for example, isohexyl, isoheptyl, isotridecyl, 2-ethylhexyl, 2-butyloctyl, 2-hexyldecyl, 2-octyldodecyl, 2-decyl tetradecyl group, R ^1, R ² is the carbon number ≧ number of carbon +1 + R ² R ¹ 24, preferably, 35 ≧ R appropriately from the relation of the number of carbon atoms ≧ 24 carbon atoms +1 + R ² of ¹ Selected.

The superhard material used in the present invention has a Mohs hardness of 7
Although inorganic materials of up to 10 can be used, for example, there are tungsten carbide, titanium carbide, tantalum carbide, vanadium carbide, chromium carbide, silicon carbide, and the like, preferably, cobalt-containing tungsten carbide (Co5 to tungsten carbide). 30w
t, preferably 7 to 15 wt%), and cobalt-containing tungsten carbide-titanium carbide.

As a surface treatment method of the magnetic layer using the cemented carbide material in the present invention, the blade is in contact with the magnetic layer,
In a coating type magnetic recording medium, a ferromagnetic powder, an abrasive,
In the case of protrusions of inorganic powder such as an antistatic agent, and in the case of a metal thin film type magnetic recording medium, a blade method for cutting metal protrusions or the like, a diamond wheel (rotary blade), or the like is used.

The blade is preferably formed by sintering powder of the above-mentioned superhard material, preferably one having a particle size of 0.1 to 1.5 μm.

The blade angle of the cemented carbide material in the blade method is 5 to 18
0 degrees, preferably 5 to 90 degrees, and when the magnetic recording medium is a tape, as shown in FIG. 1, the blade angle α of the super hard material 1 is 0.1 to 180 degrees, preferably 30 to 100 degrees. Degrees, more preferably 60 to 90 degrees, the wrap angle β is 60 to 170 degrees, preferably 80 to 170 degrees, the wrap angle δ is 0 to 90 degrees, the pressing force against the tape is 1 to 100 g, and the tape tension T _1. Is 1 to 300
g, preferably 50-250 g, tape speed v is 60-1200 m / m
in, preferably in the range of 200 to 500 m / min.

The surface of the magnetic layer treated with the superhard material according to the present invention has a Ra value (Cut off value of 0.08 mm) of 0.1 to 15 nm, preferably 0.1 to 10 nm, and fine protrusions of 1 × 10 at 10 to 100 nm. ³ to
It is preferably 1 × 10 ⁹ pieces / mm ² .

In the present invention, the surface roughness of the magnetic layer is preferably in the range of 1 to 10 nm for a coating type magnetic recording medium and 0.1 to 6 nm for a metal thin film type magnetic recording medium.

The resin used for the magnetic layer of the coating type magnetic recording medium of the present invention, and further the back layer (including the case of a metal thin film type magnetic recording medium) provided as desired, may be a conventionally known thermoplastic resin, thermosetting resin, Reactive resins can be used.

For example, condensation resins such as polyester resin, polyurethane resin, cellulosic resin, epoxy resin, polyamide resin and phenol resin, (meth) acrylate, styrene, acrylonitrile, butadiene, vinyl ester, acrylamide, vinyl chloride, chloride There is a polymerization or copolymer such as vinylidene.

Further, in order to improve the durability, it is also possible to include a curable resin having various molecular weights, for example, a thermosetting resin such as a polyisocyanate compound, a polyepoxy compound or a low-molecular compound. (Crosslinking agent, etc.)
And an ultraviolet / electron beam curing reaction type resin or a low molecular weight compound (such as a crosslinking agent) containing an unsaturated double bond.

Examples of the polyisocyanate compound include isocyanates such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and isophorone diisocyanate; products of the isocyanates and polyalcohols; and polyisocyanates formed by condensation of isocyanates. Can be used. Commercially available trade names of these polyisocyanates include Coronate 2030, Millionate MR (Nippon Polyurethane Co., Ltd.)
And Takenate D-102 (manufactured by Takeda Pharmaceutical Co., Ltd.), and these can be used alone or in combination of two or more utilizing the difference in curing reactivity.

These thermoplastic resin, thermosetting resin, reactive resin,
Carboxylic acid, sulfinic acid, sulfenic acid, sulfonic acid, sulfuric acid, phosphonic acid, as a functional group other than the main functional group
Acid groups such as phosphinic acid, boric acid, sulfate ester group, phosphate ester group, and alkyl ester group thereof (these acid groups may be in the form of Na salt); amino acids, aminosulfonic acids, sulfuric acid of amino alcohol Or an amphoteric group such as a phosphoric ester or an alkyl betaine type; an amino group, an imino group, an imide group, an amide group, an epoxy group, or the like; or a hydroxyl group, an alkoxyl group, a thiol group, a halogen group,
It can have a silyl group or a siloxane group, and a functional group can be appropriately selected for various purposes.

As the ferromagnetic powder used in the present invention, γ-Fe ₂ O ₃ , C
O-containing fine powders such as Fe-containing Fe ₂ O ₃ , γ-Fe ₃ O ₄ , Co-containing γ-Fe ₃ O ₄ , CrO ₂ , hexagonal magnetite brambite type ferrite, Fe, Co, Ni, etc. Various known ferromagnetic powders such as metal or alloy fine powders can be used.

The mixing ratio of the ferromagnetic powder and the binder in the magnetic layer is preferably in the range of 8 to 25 parts by weight of the binder per 100 parts by weight of the ferromagnetic powder. If the amount of the binder is small, the dispersibility and durability are poor, and if the amount of the binder is too large, the degree of filling of the magnetic layer is undesirably reduced.

The magnetic layer of the magnetic recording medium of the present invention may further contain a conventionally known lubricant, abrasive, or antistatic agent in addition to the compound of the present invention.

Examples of lubricants include silicone oils such as polysiloxane, inorganic fine powders such as carbon black, graphite, and molybdenum disulfide; plastic fine powders such as polyethylene and polytetrafluoroethylene; higher fatty acids; Fatty acid esters and fluorocarbons. These can be used alone or as a mixture. It is preferable to use these additives in the range of 0.2 to 20 parts by weight based on 100 parts by weight of the binder.

Examples of the abrasive include non-magnetic inorganic powders having a Mohs hardness of 5 or more, preferably 6 or more. Specifically, aluminum oxide (α-alumina, γ-alumina, fused alumina, corundum, etc.), oxidized Examples thereof include chromium (Cr ₂ O ₃ ), iron oxide (γ-Fe ₂ O ₃ ), oxides such as silicon dioxide and titanium dioxide, carbides such as silicon carbide and titanium carbide, and fine powders such as diamond. These average particle sizes are
0.05-1.0 μm is preferable, and 0.5-2
It can be added in the range of 0 parts by weight.

As an antistatic agent, conductive powders such as carbon black (especially those having an average particle size of 10 to 300 nm are preferable), graphite, carbon black graphite polymer, a nonionic surfactant, an anionic surfactant, and a cationic interface Activators and the like are used.

The magnetic layer is formed by immersing and dissolving the above-mentioned ferromagnetic powder, binder and the like in a solvent, dispersing with a disperser, and applying the dispersion on a non-magnetic support.

As the solvent, an organic solvent is preferable, and ketones such as methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; ethers such as cellosolve and tetrahydrofuran; aromatic hydrocarbons such as toluene; Solvents such as hydrogens can be mentioned.

For dispersion, various dispersers such as a sand mill can be used. For details, see TCPATTON (T.C.
(Patten) “Paint Flow and Pigment Dispersion” (Paint Flow and Pigment Dispersion), published in 1964 by John Wiley & Sons (John Wiley and Sons), can be used.

As a method for forming a magnetic layer on a non-magnetic support, a conventionally known method can be used, and specifically, a method described in a written book such as “Coating Engineering” (Asakura Shoten, 1971) is used. be able to.

Further, the magnetic layer thus formed on the support,
If necessary, a treatment for orienting the ferromagnetic powder in the magnetic layer is performed, followed by drying and a surface treatment such as a calendering treatment.

The surface treatment of the superhard material in the present invention is preferably
It is preferably performed after the calendaring process.

The thickness of the magnetic layer is 1 to 6 μm, preferably 2 to 5 μm
Is preferred.

In the present invention, as the ferromagnetic metal used for the metal thin film magnetic recording medium, iron, cobalt, nickel, other ferromagnetic metals, or alloys thereof, for example, Co
-Ni, Fe-Co, Fe-Co-Ni, Co-Ni-P and the like.

These ferromagnetic metals are provided on a non-magnetic support by a method such as electroplating, electroless plating, vapor phase plating, sputtering, or ion plating in a thickness of 0.02 μm to 2 μm, particularly 0.05 to 2 μm. Can be

When a metal thin film is formed, for example, by introducing oxygen into the above-described various ferromagnetic metal thin films by a method such as vapor deposition in an oxygen stream, the electromagnetic conversion characteristics and durability can be further improved. In addition to oxygen, N, Cr, Ga, As, Sr,
Zr, Nb, Mo, Rh, Pd, Sn, Sb, Te, Pm, Re, Os, Ir, A
u, Hg, Pb, Bi and the like may be contained.

When the compound of the present invention is top-coated on the metal thin film, the surface of the metal thin film can be modified with a surfactant such as a fatty acid or various coupling agents before providing the top coat layer. The top coat layer may be a single layer or a plurality of layers. Note that the above-described modification treatment, top coat layer structure, and the like can be applied to a coating type magnetic recording medium.

The surface treatment of the superhard material in the present invention is preferably performed before the topcoat treatment, after the formation of the magnetic layer, or after the topcoat treatment.

The thickness of the nonmagnetic support is preferably 4 to 50 μm. An underlayer may be provided on the support for improving the adhesion of the ferromagnetic thin film and improving the magnetic properties.

In order to improve running durability, it is effective to provide fine protrusions on the surface of the support before forming the metal thin film (as a result, appropriate irregularities are formed on the surface of the magnetic layer). The density of microprojections is 2 × 10 ⁶ to 2 × 10 ⁸ / mm ²
The height of one protrusion is 1 to 50 nm (nm: nanometer = 1)
It is preferred 0 ^-9 meters).

Polyethylene terephthalate is used as a substrate used for a coating type magnetic recording medium and a metal thin film type magnetic recording medium.
A plastic base such as polyimide, polyamide, polyvinyl chloride, cellulose triacetate, polycarbonate, polyethylene naphthalate, or polyphenylene sulfide, or Al, Ti, stainless steel, or the like is used.

The shape of the magnetic recording medium may be any of tape, sheet, card, disk, etc.
It is disk-shaped.

〔The invention's effect〕

The present invention, while containing the existing fatty acid ester having 24 or more carbon atoms in the magnetic layer as a compound of the present invention,
By applying a surface treatment to the magnetic layer with a super hard material, the dropout is reduced and the head wear is suppressed, and the
N can be improved, and the cost of the magnetic recording medium can be reduced.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to examples.
It will be readily understood by those skilled in the art that the components, ratios, operation orders, and the like formed here can be changed without departing from the spirit of the present invention.

Therefore, the present invention should not be limited to the following examples. Parts in Examples and Comparative Examples are parts by weight.

[Example 1] [I] of the following magnetic layer composition was put into a kneader and kneaded well, and then [II] was additionally added, and after mixing and dispersion, [III] was added and dispersed to prepare a magnetic coating solution.

Magnetic layer composition [I] Co-containing γ-Fe ₂ O ₃ powder (nitrogen adsorption specific surface area 50 m ² /
g, powder Hc = 750Oe) 100 parts carbon black (Asahi Carbon Co., Ltd., Asahi 7
0) 6 parts vinyl chloride vinyl acetate resin (manufactured by Zeon Corporation,
MR110) 12 parts polyurethane resin (Toyobo Co., Ltd., UR860
0) 6 parts Oleic acid 0.5 part Methyl ethyl ketone 48 parts [II] Abrasive (AKP20, manufactured by Sumitomo Chemical Co., Ltd.) 10 parts Polyurethane resin (C720, manufactured by Dainippon Ink Co., Ltd.)
9,) 2 parts Methyl ethyl ketone 20 parts [III] Polyisocyanate (Nippon Polyurethane Co., Ltd., Coronate 3040) 8 parts Myristic acid 1 part Fatty acid ester (described in Table 1) X part Methyl ethyl ketone 20 parts Viscosity of this magnetic layer coating solution After the adjustment, it is applied on polyethylene terephthalate having a thickness of 14 μm with a dry film thickness of 5.0 μm, and dried while a magnetic field is oriented in the application advancing direction by a 3,000 gauss counter magnet. Thereafter, the magnetic layer is continuously calendered, and then the following back composition [I] is kneaded and dispersed in a ball mill on the back side of the non-magnetic support provided with the magnetic layer, and then [II] is added and mixed and stirred. After adjusting the back solution, providing a back layer having a dry thickness of 0.5 μm and slitting it to 0.5 inch, as shown in FIG.
Degree of tungsten carbide (particle size 0.5μm, Co content 1
With superhard material 1 of 0 wt%), the wrap angle beta 90 degrees, 15 degrees wrap angle [delta], the pressing force against the tape 5g, the tape tension T ₁ 110g, the tape velocity v under the conditions of 360 m / min The magnetic layer was surface-treated and wound on a VHS reel by 250 m.

Back layer composition [I] Carbon black (manufactured by Cabot Corporation, Vulcan XC72) 100 parts Nitrocellulose (manufactured by Daicel Corporation) 5 parts Polyurethane polycarbonate resin (manufactured by Dainichi Seika Co., Ltd., FJ2) 45 parts Phenoxy resin (Union Carbide Co., Ltd.
15 parts Methyl ethyl ketone 300 parts [II] Polyisocyanate (Nippon Polyurethanes Co., Ltd.)
20 parts Abrasives (Sumitomo Chemical Co., Ltd., Hit100) 0.3 parts Lubricant (Shin-Etsu Chemical Co., Ltd., KF90) 0.1 parts Copper oleate 0.1 parts Methyl ethyl ketone 700 parts [Examples 2 to 6, Comparative Example 1 4) In Example 1, the types and amounts of the fatty acid esters are shown in Table 1.
Samples were prepared in the same manner as in Example 1 with the following changes, and their performances were evaluated. The results are shown in Table 1.

Evaluation method (1) Dropout (D.0): After storage at 60 ° C., 90% RH for 1 week, dropout of 15 μsec, −16 dB, 1 min. Was measured.

(2) Head wear: VTR after running for 50 hours at 25 ° C and 70% RH
The height (μm) of the head was measured.

(3) Y S / N: Y S / N was measured with a VHS VTR.

(4) YS / N deterioration: Y after repeated running at 20 ° C and 10% RH
The S / N was measured, and the deterioration from the first pass was displayed.

As shown in Table 1, Examples containing the compound of the present invention and having been subjected to surface treatment with the cemented carbide material of the present invention were:
Comparative Examples 1 and 2 in which R ² of the compound of the present invention was linear or the surface treatment was not performed on a superhard material using a lubricant having less than the number of carbon atoms of the compound of the present invention, Compared with Comparative Example 3 in which the surface treatment was not performed using a cemented carbide material, the dropout and head abrasion were smaller, and YS / N and YS were used.
It can be seen that the / N deterioration is excellent.

When a higher fatty acid ester having less than 24 carbon atoms is used as in Comparative Example 4, head wear is improved when the surface of the carbide blade is treated, but other performances are deteriorated and the present invention is degraded. Objective is not achieved.

[Brief description of the drawings]

FIG. 1 is a view for explaining a blade method which is one of the surface treatment methods using a hard material used in the present invention. DESCRIPTION OF SYMBOLS 1: superhard material, alpha: edge angle beta, [delta]: The wrap angle T _1: Tension

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tatsuya Ooguri 2-12-1, Ogimachi, Odawara City, Kanagawa Prefecture Inside Fuji Photo Film Co., Ltd. (56) References JP-A-62-172532 (JP, A) JP-A Sho 59-8131 (JP, A) JP-A-54-33003 (JP, A) JP-A-61-61234 (JP, A) JP-A-58-130435 (JP, A) (58) Fields investigated (Int. Cl ^6, DB name) G11B 5/62 -. 5/72 G11B 5/84 - 5/858 C09D 5/23

Claims (2)

(57) [Claims] 1. A magnetic recording medium having a magnetic layer provided on a nonmagnetic support, wherein the magnetic layer contains a higher fatty acid ester having 24 or more carbon atoms represented by the following general formula (I); A magnetic recording medium, wherein a dry surface of the magnetic layer is subjected to a surface treatment with a super hard material. ^{R 1 COOR 2 ··· (I)} ( wherein, R ¹ represents a hydrocarbon group having 14 to 35 carbon atoms, R ² represents a branched alkyl group having 4 to 30 carbon atoms, and the number of carbon atoms in R ¹ The sum with the carbon number of R ² is 23 or more.) 2. A method of manufacturing a magnetic recording medium having a magnetic layer provided on a non-magnetic support, comprising: forming a magnetic layer on the non-magnetic support; and applying a surface treatment to a dry surface of the magnetic layer with a superhard material. A method for producing a magnetic recording medium, wherein the higher fatty acid ester according to claim 1 is contained in a magnetic layer at least one of before and after the surface treatment.