JPH0766539B2 - Magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention is a so-called magnetic thin film formed on a non-magnetic support as a magnetic layer by a technique such as vacuum thin film forming technology such as vacuum deposition or sputtering. The present invention relates to a ferromagnetic metal thin film type magnetic recording medium.

[Outline of Invention]

The present invention provides a magnetic recording medium comprising a ferromagnetic metal thin film formed as a magnetic layer on a non-magnetic support, wherein the ferromagnetic metal thin film as the magnetic layer is lubricated with a perfluoroalkylcarboxylic acid ester and a composite extreme pressure agent. The purpose of the present invention is to provide a magnetic recording medium which is adhered as an agent, exhibits excellent running properties, wear resistance, and durability under all conditions of use, and continues to have these lubricating effects.

[Conventional technology]

Conventionally, γ-Fe has been used as a magnetic recording medium on a non-magnetic support.
₂ O ₃ , containing Co γ-Fe ₂ O ₃ , Fe ₃ O ₄ , containing Co Fe ₃ O ₄ , γ-
Betride compound of Fe ₂ O ₃ and Fe ₃ O ₄ , Bertride compound containing Co, oxide ferromagnetic powder such as CrO ₂ or F
Apply and dry a magnetic paint in which a powder magnetic material such as alloy magnetic powder containing e, Co, Ni, etc. as the main component is dispersed in an organic binder such as vinyl chloride-vinyl acetate copolymer, polyester resin, polyurethane resin, etc. The coating type magnetic recording medium produced by the above method is widely used.

On the other hand, with the increasing demand for high-density magnetic recording, a ferromagnetic metal material such as Co-Ni alloy is coated with polyester by plating or vacuum thin film forming technology (vacuum evaporation method, sputtering method, ion plating method, etc.). Directly deposited on a non-magnetic support such as a film or polyimide film,
A so-called ferromagnetic metal thin film type magnetic recording medium has been proposed,
It is getting attention. This ferromagnetic metal thin film type magnetic recording medium is not only excellent in coercive force and squareness ratio and excellent in electromagnetic conversion characteristics at short wavelengths, but it is also possible to make the thickness of the magnetic layer extremely thin so that recording demagnetization is possible. Also, there are various advantages such as a remarkably small thickness loss at the time of reproduction and an increase in the packing density of the magnetic material because it is not necessary to mix an organic binder which is a specific magnetic material in the magnetic layer.

However, in the above-mentioned ferromagnetic metal thin film type magnetic recording medium, since the smoothness of the magnetic layer surface is extremely good, the substantial contact area becomes large, and the adhesion phenomenon (so-called sticking) easily occurs or friction The coefficient becomes large, etc.
There are many drawbacks in durability and runnability, and their improvement is a major issue. In general, a magnetic recording medium must be placed in a high-speed relative motion with a magnetic head in the process of recording / reproducing a magnetic signal, and at that time, the running must be performed smoothly and in a stable state. Further, it is preferable that wear and damage due to contact with the magnetic head be as small as possible.

Therefore, for example, it has been attempted to improve the durability and the running property by applying a lubricant to the surface of the magnetic layer of the magnetic recording medium, that is, the surface of the ferromagnetic metal thin film to form a protective film.

[Problems to be solved by the invention]

By the way, when the protective film is formed by applying the lubricant as described above, the protective film exhibits good adhesion to the ferromagnetic metal thin film which is the magnetic layer and exhibits a high lubricating effect. Is required. Further, these adhesion and lubricating effect must be excellent under high temperature and high humidity conditions such as in tropical regions and subtropical regions, and under low temperature conditions such as cold regions.

However, the operating temperature range of conventionally widely used lubricants is limited, and in particular, many of them solidify or freeze at a low temperature such as 0 to −5 ° C., so that the lubricating effect is sufficiently exerted. I couldn't make it work. Furthermore, there is a problem that the lubricant is gradually scraped off by the magnetic head due to the insufficient adhesion of the lubricant to the ferromagnetic metal thin film, and the effect is rapidly reduced.

Therefore, it is an object of the present invention to provide a magnetic recording medium that maintains adhesion and lubricity under any use conditions and that has a long-lasting lubrication effect.

[Means for solving problems]

As a result of earnest studies that the above-mentioned objects cannot be achieved, the present inventors have found that a long-chain alkyl group or an alkyl group having a double bond, or a branched alkyl group, in the ester portion of perfluoroalkylcarboxylic acid. By combining the perfluoroalkyl carboxylic acid ester with either introduced and the composite type extreme pressure agent, excellent lubricating action is exhibited as compared with the case where it is used alone, and at the same time, it is possible to expand the temperature range of use and sustainability. The present invention has been completed in the light of the fact that it is possible to improve the properties, and a ferromagnetic metal thin film is formed on a non-magnetic support, and a perfluoroalkylcarboxylic acid is formed on the ferromagnetic metal thin film. It is characterized in that a lubricant layer containing an ester and a composite type extreme pressure agent is applied.

The perfluoroalkylcarboxylic acid ester used in the present invention has the general formula C _n F _{2n + 1} COOR (wherein n represents an integer of 6 to 10 and R represents a carbon number of 1).
Represents ~ 25 hydrocarbon groups. ) And can be easily synthesized by reacting a perfluoroalkylcarboxylic acid with a corresponding alcohol.

In the above perfluoroalkylcarboxylic acid ester, the carbon number n of the perfluoroalkylcarboxylic acid moiety is
It is preferably in the range of 6-10. This carbon number n is 6
When it is less than the above range, the lubricating effect is insufficient, and conversely, when the number of carbons exceeds 10, solidification occurs in the low temperature range, and therefore the lubricating effect under the low temperature condition deteriorates. The same applies to the number of carbon atoms of the hydrocarbon group of the ester portion, and in the above general formula, the number of carbon atoms of the hydrocarbon group R is preferably 1 to 25, more preferably 9 to 25. . If the number of carbon atoms in the hydrocarbon group R is less than 9, the lubricating effect will be insufficient, and if it exceeds 25, the lubricating effect at low temperatures will be lost. The hydrocarbon group R may be a long chain alkyl group, a branched alkyl group or an alkylene chain having a double bond.

On the other hand, the composite-type extreme pressure agent used in the present invention reacts with a metal surface by frictional heat generated when a metal contact is partially generated in the boundary lubrication region to form a reaction product film. It serves to prevent friction and wear.

Specifically, dialkylthiophosphate amines such as di-2-ethylhexylthiophosphate amine, propyl chloride phosphate, propyl bromide phosphate, propyl iodide phosphate, butyl chloride chloride, butyl bromide phosphate, butyl iodide phosphate, etc. Typical alkyl halide phosphates, chloronaphthazanate, etc., as well as general formula (However, in each general formula, R represents a hydrogen atom or an alkyl group, an alkenyl group, or an aryl group.) The thiophosphates represented by the general formula (However, in the formula, R represents a hydrogen atom or an alkyl group, an alkenyl group, or an aryl group.) The thiophosphites and the like are highly effective.

The mixing ratio of the above-mentioned perfluoroalkylcarboxylic acid ester and the complex type extreme pressure agent is preferably 30:70 to 70:30 by weight. In addition to the above-mentioned perfluoroalkylcarboxylic acid ester and composite type extreme pressure agent, conventionally known lubricants, other extreme pressure agents, rust preventives, etc. may be used in combination, if necessary.

As the lubricant used, a fatty acid or a metal salt thereof,
Fatty acid amide, fatty acid ester, aliphatic alcohol or alkoxide thereof, aliphatic amine, polyhydric alcohol,
Sorbitan ester, mannitan ester, sulfurized fatty acid, aliphatic mercaptan, modified silicone oil, perfluoroalkyl ethylene oxide, perfluoropolyethers, higher alkyl sulfonic acid or its metal salt, perfluoroalkyl sulfonic acid or its ammonium salt or its Examples thereof include metal salts, perfluoroalkylcarboxylic acids or metal salts thereof.

Examples of the extreme pressure agent include phosphorus-based extreme pressure agents, sulfur-based extreme pressure agents,
Halogen-based extreme pressure agents, organometallic extreme pressure agents, etc. can be used.

Specifically, examples of the phosphorus-based extreme pressure agent include tributyl phosphate, trioctyl phosphate, tri-2-ethylhexyl phosphate, trilauryl phosphate, trioleyl phosphate, dibutyl phosphate, dioctyl phosphate, di-2-ethylhexyl phosphate. , Phosphates such as dilauryl phosphate, dioleyl phosphate, tributyl phosphite, trioctyl phosphite, tri-2-ethylhexyl phosphite, trilauryl phosphite, trioleyl phosphite, dibutyl phosphite, dioctyl phosphite, dioctyl phosphite 2-Ethylhexyl phosphite, dilauryl phosphite, dioleyl phosphite and other phosphites, dibutyl phosphate butylamine salts, dibuty Phosphate octyl amine salt, dibutyl phosphate stearyl amine salt, dioctyl phosphate butyl amine salt, dioctyl phosphate octyl amine salt, dioctyl phosphate lauryl amine salt, dioctyl phosphate stearyl amine salt, di-2-ethylhexyl phosphate butyl amine salt, di-2-ethylhexyl phosphate octyl Amine salt,
Di-2-ethylhexyl phosphate lauryl amine salt, di-2-ethylhexyl phosphate stearyl amine salt, dilauryl phosphate butyl amine salt, dilauryl phosphate octyl amine salt, dilauryl phosphate lauryl amine salt, dilauryl phosphate stearyl amine salt, dioleyl phosphate Examples thereof include phosphate ester amine salts such as butyl amine salt, dioleoyl phosphate octyl amine salt, dioleoyl phosphate lauryl amine salt, and dioleoyl phosphate stearyl amine salt.

Examples of the sulfur-based extreme pressure agents include sulfurized whale oil, mineral oils having unsaturated engagement such as sulfurized dipentene, sulfurized oils and fats produced by adding sulfur to oils and fats and fatty acids, and dibenzyl disulfide, Diphenyl sulfide, di-disulfide
t-butyl, di-sec-butyl disulfide, di-n-disulfide
Disulfides such as butyl, di-t-octyl disulfide, diethyl disulfide, benzyl sulfide, diphenyl sulfide, divinyl sulfide, dimethyl sulfide, diethyl sulfide, di-t sulfide
-Butyl, di-sec-butyl sulfide, mono-sulfides such as di-n-butyl sulfide, dimethyl trisulfide, disulfide tri-
Polysulfides such as t-butyl, di-t-nonyl polysulfide, and olefin polysulfide, general formula (However, in the formula, R represents a hydrocarbon group.), Thiocarbonates and elemental sulfur.

Examples of the halogen-based extreme pressure agent include bromine compounds such as allyl bromide, octadecyl bromide, cyclohexyl bromide, stearyl bromide and benzyl iodide, benzyl iodide, allyl iodide, butyl iodide, octadecyl iodide, and iodine. Iodine compounds such as cyclohexyl chloride, hexachloroethane, monochloroethane, chlorinated paraffin, chlorinated diphenyl,
Chlorinated compounds such as chlorinated oils and fats, methyltrichlorostearate, pentachloropentadienoic acid, esters of hexachloronaphthenic acid compounds, imide derivatives of hexachloronaphthenic acid compounds, and the like can be mentioned.

Examples of the organometallic extreme pressure agent include zinc diisobutyldithiophosphate, zinc isobutylpentyldithiophosphate, isopropyl-1-methylbutyldithiophosphoric acid, zinc isobutylnonylphenyldithiophosphate, isobutylheptylphenyldithiophosphoric acid, diheptylphenyldithiophosphoric acid, and diheptylphenyldithiophosphoric acid. Thiophosphates such as zinc nonylphenyldithiophosphate, molybdenum dithiophosphate, etc., zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc dimethyldithiocarbamate, dimethylthiocarbamine Thios such as copper acid, iron dimethyldithiocarbamate, selenium diethyldithiocarbamate, silver diethyldithiocarbamate, etc. Rubamin acid salts, molybdenum, metal alkyl dithiocarbamates, such as antimony, and the like.

As a method for adhering a lubricant layer containing these perfluoroalkylcarboxylic acid esters on the ferromagnetic metal thin film, a solution obtained by dissolving the above lubricant in a solvent is applied or sprayed on the surface of the ferromagnetic metal thin film. Alternatively, or conversely, the ferromagnetic metal thin film may be dipped in this solution and dried.

Here, the coating amount is preferably from ^{0.5mg / m 2 ~100mg / m 2} , and more preferably ^{1mg / m 2 ~20mg / m 2} .
If this coating amount is too small, the effects of lowering the friction coefficient and improving wear resistance and durability will not be manifested, while if it is too large, the sticking phenomenon will occur between the sliding member and the ferromagnetic metal thin film. On the contrary, the running performance becomes worse.

Alternatively, in addition to the above-mentioned lubricant and extreme pressure agent, a rust preventive agent may be used in combination if necessary.

In general, a ferromagnetic metal thin film is formed of a metal material, and is therefore easily rusted, and the corrosion resistance is greatly improved by using the rust preventive agent. Therefore, the durability of the magnetic recording medium can be improved in combination with the lubricating action of the lubricant containing the perfluoroalkylcarboxylic acid ester.

As the rust preventive agent that can be used, the following may be used as long as it is usually used as a rust preventive agent for magnetic recording media of this type, for example, phenols, naphthols, quinones, diaryl ketones, Examples thereof include a heterocyclic compound containing a nitrogen atom, a heterocyclic compound containing an oxygen atom, a heterocyclic compound containing a sulfur atom, a compound having a mercapto group, a thiocarboxylic acid or its salt, and a thiazole compound.
A specific example is as follows.

First, examples of the above-mentioned phenols include dihydric phenol, alkylphenol and nitrosophenol.

Examples of the dihydric phenol include pure phenols such as hydroquinone, resorcin, and catechol, and their alkylamino-, nitro-, and halogeno-substituted products, for example, 2-
Methylhydroquinone, 4-methylresorcinol, 5-methylresorcinol, 4-methylpyrocatechol, 2,5-dimethylhydroquinone, 4,6-dimethylresorcinol,
2,5-dimethylresorcinol, 2-isopropyl-5-
Examples thereof include methylhydroquinone, 2-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, 4-tert-butylcatechol, 2-aminoresorcinol, 2-resorcinol, and 2,5-dichlorohydroquinone. The above-mentioned alkylphenol refers to an alkyl-substituted product of monohydric phenol, for example, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, 2,3-dimethylphenol. , 2,5-Dimethylphenol, 2,6-Dimethylphenol, 3,4-Dimethylphenol, 3,5-Dimethylphenol, 2,4,6-Trimethylphenol, 2,4,5-Trimethylphenol, 5-Isopropyl -2-methylphenol, p-
tert-butylphenol, 2,6-di-tert-butyl-p-
Cresol, 4,4'-methylenebis2,6-di-tert-butylphenol, 2,6-dimethyl-4-tert-butylphenol, 2,4,6-tri-tert-butylphenol and the like can be mentioned.

Examples of the nitrosophenol include 4-nitroso-2-methoxy-1-phenol and 4-nitroso-2-
Ethoxy-1-phenol, 6-nitroso-o-cresol, 4-nitroso-m-cresol, o-nitrosophenol, 2-nitrosophenol, 2-nitrosoresorcin, 4-
Nitrosoresorcin, p-nitrosophenol, etc. are mentioned.

Next, the naphthols include α-naphthol and β
-Naphthol, 1,2-naphthalene diol, 1,3-naphthalene diol, 1,4-naphthalene diol, 1,5-naphthalene diol, 1,7-naphthalene diol, 1,8-naphthale diol, 2,3- Pure naphthols such as naphthalenediol, 1,4,5-naphthalenetriol, 1,2,5,8-naphthalenetetraol, and nitro, nitroso, amino, halogeno-substituted naphthols such as 1-chloro-2-naphthol, 2,4
-Dichloro-1-naphthol, 1-nitro-2-naphthol, 1,6-dinitro-2-naphthol, 1-nitroso-2-
Naphthol, 2-nitroso-1-naphthol, 1-amino-
2-naphthol and the like can be mentioned.

The above-mentioned quinones include quinones having no substituent such as p-benzoquinone, o-benzoquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, 2,6-naphthoquinone, anthraquinone, 9,10-phenanthrenequinone and diphenoquinone. Methyl quinones such as methyl-p-benzoquinone, 2,3-dimethyl-p-benzoquinone, 2-methyl-1,4-naphthoquinone and 2-methylanthraquinone, 2,5-dihydroxy-p-
Benzoquinone, tetrahydroxy-p-benzoquinone, 5
-Hydroxy-1,4-naphthoquinone, 2,3-dihydroxy-1,4-naphthoquinone, 5,8-dihydroxy-1,4-naphthoquinone, 2-hydroxyanthraquinone, 1,2-dihydroxyanthraquinone, 1,2,3 -Hydroxyquinones such as trihydroxyanthraquinone, 1,2,4-trihydroxyanthraquinone, 1,2,5-trihydroxyanthraquinone, 1,2,6-trihydroxyanthraquinone, 1,2,7-trihydroxyanthraquinone, 2-aminoanthraquinone, 1,2-
Aminoquinones such as diaminoanthraquinone, nitroquinones such as 1-nitroanthraquinone and 1,5-dinitroanthraquinone, halogenoquinones such as 2,6-dichloro-p-benzoquinone, tetrachloro-p-benzoquinone and tetrabromo-p-benzoquinone, Alternatively, quinones having two or more kinds of substituents such as 2,5-dichloro-3,6-
Examples thereof include dihydroxy-p-benzoquinone and 1-methyl-2-hydroxy-1,4-naphthoquinone.

Examples of the diaryl ketone include benzophenone and its derivatives, for example, benzophenone, 4-methylbenzophenone, 3-methylbenzophenone, 3,4-dimethylbenzophenone, 4,4'-dimethylbenzophenone, 3,4 '.
-Dimethylbenzophenone, alkyl-substituted 4-ethylbenzophenone, 4-hydroxybenzophenone, 4,
4'-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2 ', 5,6'-tetrahydroxybenzophenone, 2,
Hydroxybenzophenones such as 3 ', 4,4', 6-pentahydroxybenzophenone, 4-aminobenzophenone, aminobenzophenones such as 4,4'-diaminobenzophenone, or benzophenones having two or more substituents, for example, 4-methoxy-2-hydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone and the like can be mentioned.

Examples of the heterocyclic compound containing a nitrogen atom include acridine, 2,2 ', 2 "-terpyridyl neocuproine and 2,2'-
In addition to dipyridylbenzotriazole, 5-methylbenzotriazole, bathophenanthroline, 1,10-phenanthroline, aldehyde collidine, benzylpyridine, phenylpyridine, quinazoline, 2-heptadecylimidazole and the like, compounds having a phenolic hydroxyl group, for example 4- Compounds having a carboxyl group such as (2-pyridylazo) -resorcin 1- (2-pyridylazo) -2-naphthol, 4-quinolinol, 4-methyl-2-quinolinol, 8-quinolinol, quinolinediol, for example, kynurenic acid, acridine Acid, attophan, kyrnazinic acid, cinchoninic acid, isonicotinic acid, 2,5-pyridinecarboxylic acid,
A compound having an amino group or an imino group such as quinic acid, for example, 2-aminobenzimidazole, 5-amino-1H-tetrazole, 5-amino-1H-1,2,4-triazole, adenine, guanine, luminol, 2- Compounds having a carbonyl group such as hydrazinoquinoline and thiamine, for example, riboflavin, theobromine, allantoin, alloxan, 2-thiobarbituric acid, violuric acid, isatin, hydantoin, mitin, barbituric acid, orotic acid, uracil, succinimide, creatinine 2,2-pyrrolidone and the like can be mentioned.

Examples of the heterocyclic compound containing an oxygen atom include tocopherol, morin, quercetin, ascorbic acid, anhydrous 1,8
-Naphthalic acid, resorufin, kojic acid, dehydroacetic acid, oxazole, 3-aminophthalimide, 4-aminophthalimide, uridine, thymidine, guanosine and isatoic anhydride.

Examples of the heterocyclic compound containing a sulfur atom include sulfolane, 3-hydroxysulfolane, 3-methylsulfolane, sulfolene, 3-hydroxysulfolene, 3-methylsulfolene, rhodanine, 3-aminorhodanin, and thiazoline-4.
-Carboxylic acid, 4H-1,4-thiazine, biotin, 3,6-thioxanthenediamine, 3,6-thioxanthenediamine-1
0,10-dioxide and the like can be mentioned.

Examples of the compound having a mercapto group include 2-benzoxazolethiol, thiophenol, thiosalicylic acid, propanethiol, thiouracil, 2,3-quinoxalinedithiol, dithizone, thiooxine, 2-benzimidazolethiol, 6-thioguanine, 5-nitro. 2-benzimidazole thiol, 5-amino-1,3,4-thiazole-2-thiol and the like can be mentioned.

Examples of the thiocarboxylic acid or its salt include sodium diethyldithiocarbamate, ethanethioic acid, rubeanic acid, thioacetamide, ethanedithioic acid and the like.

The thiazole-based compound, bismuthiol II,
Diazo sulfide, azosulfime, 1,3,4-thiadiazole, bismuthiol, beazthiol, benzothiazole, 2-methylbenzothiazole, 2- (p-aminophenyl) -6-methylbenzothiazole, 2-mercaptobenzothiazole, benzothiazoline, Examples thereof include 2-benzothiazoline and benzothiazolone.

The rust inhibitor may be used as a mixture with the lubricant,
For example, it is highly effective if the rust preventive agent is first coated on the surface of the ferromagnetic metal thin film, and then the lubricant containing the perfluoroalkylcarboxylic acid ester is coated on the surface of the ferromagnetic metal thin film so that the coating is divided into two or more layers. .

In the case of coating in two layers as described above, the coating amount of the above-mentioned rust preventive agent is 0.5 mg / m ^{2 to} 100 m as in the case of the above lubricant.
is preferably from g / m ^2, and more preferably ^{1mg / m 2 ~20mg / m 2} . If the coating amount is too small, the effect of improving the corrosion resistance is insufficient, and conversely, if it is too large, problems such as running properties occur.

The magnetic recording medium to which the present invention is applied is one in which a ferromagnetic metal thin film is provided as a magnetic layer on a non-magnetic support. Here, as the material of the non-magnetic support, polyesters such as polyethylene terephthalate, Polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide and polyamideimide,
Examples include light metals such as aluminum alloys and titanium alloys, and ceramics such as alumina glass. The form of this non-magnetic support may be any of film, sheet, disk, card, drum and the like.

The surface roughness may be controlled by forming one or more kinds of protrusions such as mountain-like protrusions, wrinkle-like protrusions and granular protrusions on the surface of the non-magnetic support.

The mountain-shaped projections have a particle size of 50 when forming a polymer film, for example.
It is formed by internally adding about 0 to 3000Å inorganic fine particles, and the height from the polymer film surface is 100 to 1000Å,
The density is approximately 1 × 10 ⁴ to 10 × 10 ⁴ pieces / mm ² . Calcium carbonate (CaCO ₃ ), silica, alumina and the like are suitable as the inorganic fine particles used for forming the mountain-shaped projections.

The wrinkle-like protrusions are, for example, ridges formed by coating and drying a dilute solution of a resin using a specific mixed solvent, and the height thereof is 0.01 to 10 μm, preferably 0.03 to 0.5.
μm, and the shortest distance between protrusions is 0.1 to 20 μm. As the resin for forming the wrinkle-like protrusions, saturated polyester such as polyethylene terephthalate and polyethylene naphthalate, polyamide, polystyrene, polycarbonate, polyacrylate, polysulfone, polyether sulfone, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral. , Polyphenylene oxide, phenoxy resin, and various other resins, simple substances, mixtures, or copolymers, and those having a soluble solvent are suitable. Then, in a solution having a resin concentration of 1 to 1000 ppm in which these resins are dissolved in the good solvent, a poor solvent for the resin having a boiling point higher than that of the good solvent is added to the resin in an amount of 10 to 10 ppm.
Apply 0 times the amount of the solution added to the surface salt of the polymer film.
By drying, a thin layer having very fine wrinkle-like irregularities can be obtained.

The granular protrusions are formed by attaching organic ultrafine particles such as acrylic resin or inorganic fine particles such as silica or metal powder in a spherical or hemispherical shape. The height of this granular protrusion is
50 to 500Å, and the density is 1 × 10 ⁶ to 50 × 10 ⁶ pieces / mm ² .

The formation of at least one or more of these protrusions controls the surface properties of the co-magnetic metal thin film that is the magnetic layer, but the effect is increased by combining two or more thereof, and in particular, a wrinkle-like base film is provided. If the bumps are formed, the durability and the running property are significantly improved.

In this case, the total height of the protrusions is preferably in the range of 100 to 2000Å, and the density thereof is preferably 1 × 10 ⁵ to 1 × 10 ⁷ per 1 mm ^{2 on} average.

The ferromagnetic metal thin film that is the magnetic layer is formed as a continuous film by a vacuum thin film forming technique such as a vacuum deposition method, an ion plating method, and a sputtering method.

In the above vacuum vapor deposition method, a ferromagnetic metal material is evaporated by resistance heating, high frequency heating, electron beam heating or the like under a vacuum of 10 ^-4 to 10 ^-8 Torr, and the evaporated metal (ferromagnetic metal material) is deposited on the disk substrate. In order to obtain a high coercive force, an oblique evaporation method in which the ferromagnetic metal material is obliquely evaporated on the substrate is adopted. Alternatively, the above vapor deposition is also included in order to obtain a higher coercive force.

The ion plating method is also a type of vacuum deposition method, and DC glow discharge or RF glow discharge is caused in an inert gas atmosphere of 10 ^-4 to 10 ^-3 Torr to evaporate the ferromagnetic metal material during discharge. It is to let.

The sputtering method is to cause a glow discharge in an atmosphere containing an argon gas of 10 ^-3 to 10 ^-1 Torr as a main component, and to knock out atoms on the target surface with the generated argon gas ions. Depending on the method, there are a direct current 2-pole and 3-pole sputtering method, a high frequency sputtering method, a magnetron sputtering method using magnetron discharge, and the like. When this sputtering method is used, a base film of Cr, W, V or the like may be formed.

In any of the above methods, a base metal layer such as Bi, Sb, Pb, Sn, Ga, In, Cd, Ge, Si, and Tl is previously formed on the substrate by depositing it on the substrate surface. By forming the film in the vertical direction, a magnetic layer having no magnetic anisotropy orientation and excellent in-plane isotropy can be formed, which is suitable for a magnetic disk, for example.

When forming a metal magnetic thin film by such a vacuum thin film forming technique, Fe, Co,
In addition to Ni and other metals, Co-Ni alloys, Co-Pt alloys, Co-Ni-Pt
Alloy, Fe-Co alloy, Fe-Ni alloy, Fe-Co-Ni alloy, Fe-Co-
Examples thereof include B alloys, Co-Ni-Fe-B alloys, Co-Cr alloys, and those containing metals such as Cr and Al. Particularly, when a Co-Cr alloy is used, a perpendicular magnetization film is formed.

The thickness of the magnetic layer formed by such a method is 0.04
It is about 1 μm.

A so-called back coat layer may be formed on the surface of the non-magnetic support opposite to the surface on which the magnetic layer is provided. The back coat layer is formed by applying a back coat coating material in which a binder resin and a powder component are mixed and dispersed in an organic solvent to the surface of the non-magnetic support.

Here, as the binder resin used in the coating material for the back coat, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile Copolymer, thermoplastic polyurethane elastomer, polyvinyl fluoride, vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, polyester resin, synthetic rubber resin such as polybutadiene, phenol resin , Epoxy resin, polyurethane curable resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, epoxy-polyamide resin, nitrocellulose-melamine resin, high molecular weight polyester resin and iso Anate prepolymer mixture, methacrylate copolymer and diisocyanate prepolymer mixture, polyester polyol and polyisocyanate mixture, urea formaldehyde resin, low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate And a mixture of polyamine resins and mixtures thereof.

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

Specifically, --SO ₃ M, --OSO ₃ M, --COOM, (In the formula, M represents a hydrogen atom or an alkali metal, and M '
Represents a hydrogen atom, an alkali metal or a hydrocarbon group. )
Polyurethane resin, polyester resin, vinyl chloride-vinyl acetate type copolymer, vinylidene chloride type copolymer, acrylic ester type copolymer, butadiene type copolymer, etc. having hydrophilic polar group selected from It is possible.

As a method for introducing the hydrophilic polar group, various methods are conceivable depending on the type of resin. For example, in order to introduce the hydrophilic polar group into a polyurethane resin or a polyester resin, the following method is used. Good.

(1) A method of previously introducing the hydrophilic polar group into a dibasic acid, a polyol or the like which is a raw material of polyurethane or polyester.

(2) Leave an OH group at the end or side chain,
A method of modifying the OH group with a compound having a hydrophilic polar group.

In the case of the method of (2), (2) -1 a compound containing a hydrophilic polar group and a halogen (for example, chlorine) in the molecule and a polyfunctional polyol as a raw material are used for the terminal or side chain of the polymer difference. Polyurethane resin or polyester resin with residual OH group is dissolved in a solvent such as dimethylformamide, dimethylsulfoxide, etc., in which both components are soluble, and amines such as pyridine, picoline, triethylamine, ethylene oxide, propylene oxide, etc. A method for introducing a hydrophilic polar group by a dehydrochlorination reaction between an OH group and chlorine in the presence of a dehydrochlorination agent such as an epoxy compound.

(2) -2 Reaction of a compound containing a hydrophilic group and an OH group in the molecule with a polyurethan resin or polyester resin having an OH group remaining at the terminal or side chain of the polymer chain via a diisocyanate compound How to make.

There is.

Further, in order to introduce a hydrophilic polar group into the copolymer binder resin, (3) a method using a compound having a hydrophilic polar group and a copolymerizable double bond as the copolymerization monomer.

(4) A compound having active hydrogen and a double bond capable of copolymerization is used as a copolymerization monomer, and the above-mentioned active hydrogen is introduced into the side chain of the copolymer to prepare a hydrophilic polar group and the above-mentioned active hydrogen. A method of modifying with a compound having a reactive group.

(5) As the copolymerization monomer, a compound having a group capable of reacting with active hydrogen and a compound having a copolymerizable double bond is used, and the group capable of reacting with active hydrogen is introduced into the side chain of the copolymer. A method of modifying with a compound having a hydrophilic polar group and the above active hydrogen.

Etc.

On the other hand, examples of the powder component include carbon-based fine powder for imparting conductivity (for example, furnace carbon, channel carbon, acetylene carbon, thermal carbon, lamp carbon, etc., among which furnace carbon and thermal carbon are preferable. is preferred.), α-FeOOH to be added for the control of the inorganic pigment (surface roughness and improving _{durability, -Fe 2 O 3, Cr 2} O 3, TiO 2, ZnO, SiO, S
iO ₂ , SiO ₂・ 2H ₂ O, Al ₂ O ₃・ 2SiO ₂・ 2H ₂ O, 3MgO ・ 4SiO ₂・ H
_{2 O, MgCO 3 · Mg (} OH) 2 · 3H 2 O, Al 2 O 3, CaCO 3, MgCO 3, Sb 2 O 3
Etc.) can be mentioned.

Furthermore, as the organic solvent for the back coat paint,
Acetone, methyl ethyl ketone, methyl isobutyl ketone, ketone solvents such as cyclohexanone, methyl acetate,
Ester solvents such as ethyl acetate, butyl acetate, ethyl lactate, glycol monoethyl ether acetate, glycol dimethyl ether, glycol monoethyl ether, glycol ether solvents such as dioxane, aromatic hydrocarbon solvents such as benzene, toluene, xylene, Hexane,
Aliphatic hydrocarbon solvents such as heptane, methylene chloride, ethylene chloride, carbon tetrachloride, chloroform,
A general-purpose solvent such as a chlorinated hydrocarbon solvent such as ethylene chlorohydrin or dichlorobenzene can be used.

A lubricant may be used in combination with the above-mentioned back coat layer. In this case, there is a method of internally adding a lubricant into the back coat layer or a method of depositing a lubricant on the back coat layer. In any case, conventionally known lubricants such as fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, paraffins and silicones can be used as the lubricant.

Examples of these lubricants include fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, etc. Fatty acids can be used.

As the fatty acid ester, ethyl stearate, butyl stearate, amyl stearate, stearic acid monoglyceride, oleic acid monoglyceride and the like can be used.

As the fatty acid amide, caproic acid amide, capric acid amide, lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide,
Linoleic acid amide, methylebisstearic acid amide, ethylenebisstearic acid amide and the like can be used.

As the metal soap, Zn, Pb, Ni, Co, Fe, Al of the above fatty acids,
Salts with Mg, Sr, Cu, etc., or sulfonic acids such as lauryl sulfonic acid, palmityl sulfonic acid, myristyl sulfonic acid, stearyl sulfonic acid, behenyl sulfonic acid, oleyl sulfonic acid, linole sulfonic acid, linolene sulfonic acid and the above metals The salt and the like can be used.

As the aliphatic alcohol, cetyl alcohol, stearyl alcohol and the like can be used.

Saturated hydrocarbons such as n-nonadecane, n-tridecane, and n-docosane can be used as the parisine.

As the silicone, a polysiloxane in which hydrogen is partially substituted with an alkyl group or a phenyl group, and those obtained by modifying them with a fatty acid, an aliphatic alcohol, a fatty acid amide, or the like can be used.

Further, it contains a perfluoroalkylcarboxylic acid ester such as the same perfluoroalkylcarboxylic acid ester as the lubricant layer attached to the surface of the magnetic layer or a mixture of the perfluoroalkylcarboxylic acid ester and the complex type extreme pressure agent. A lubricant may be used.

[Action]

The lubricant layer containing the perfluoroalkylcarboxylic acid ester and the composite type extreme pressure agent adheres to the ferromagnetic metal thin film and exerts a good lubricating action to reduce the friction coefficient. In particular, perfluoroalkylcarboxylic acid ester exhibits a good lubricating effect even at low temperatures. On the other hand, the combined use of the composite type extreme pressure agent improves the adhesion to the ferromagnetic metal thin film and maintains the lubricity.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

First, a perfluoroalkylcarboxylic acid ester was synthesized according to the following synthesis example.

Synthesis Example 1. Nonadecafluorodecanoic acid isostearyl ester An ester reaction was carried out using isostearyl alcohol and nonadecafluorodecanoic acid in toluene and p-toluenesulfonic acid as a catalyst. That is, after heating under reflux for 1 hour, 3
Water was removed from the solvent over a period of time, and toluene was further removed under reduced pressure using an evaporator, followed by vacuum distillation for purification. (Note that isostearyl alcohol was synthesized by converting commercially available isostearic acid to n-butyl ester and then reducing it with lithium aluminum hydride.) The boiling point bp of the obtained fraction was 140 to 145 ° C / 0.2 mmHg. It was

In addition, the product was confirmed by infrared spectroscopy (IR), nuclear magnetic resonance analysis (NMR), and mass spectrometry (MASS). As a result, the absorption characteristic of the CF bond between 1210 and 1380 cm ⁻¹ , 17
Absorption of ester 80 cm ^-1, the absorption was observed by stretching vibration 2910cm ^-1 12CH, also in the mass spectrum by chemical ionization method, ⁺ molecular ion peak M from that seen in 765, to determine the structure.

Synthesis Example 2. Pentadecafluorooctanoic acid isostearyl ester By the same method as in Synthesis Example 1 above, isostearyl alcohol and pentadecafluorooctanoic acid in toluene,
The reaction was performed using p-toluenesulfonic acid as a catalyst.

bp 120~134 ℃ (0.2mmHg) IR 1200~1400cm -1 1780cm -1 2920cm -1 M + 665 Synthesis Example 3. pentadecafluorooctanoic isononyl ester _{CF 3 (CF 2) 6 COOCH} 2 CH 2 CH (CH ₃ ) CH ₂ C (CH ₃ ) _{3 In} the same manner as in Synthesis Example 1 above, isononyl alcohol and pentadecafluorooctanoic acid were added to p-
The reaction was carried out using toluenesulfonic acid as a catalyst.

bp 94 ℃ (0.2mmHg) IR 1210~1390cm -1 1785cm -1 2850~2960cm -1 M + 539 Synthesis Example 4. pentadecafluorooctanoic acid linoleyl ester _{CF 3 (CF 2) 6 COO} (CH 2) 3 ( CH = CHCH ₂ ) ₂ (CH ₂ ) ₃ CH ₃ By the same method as in Synthesis Example 1 above, linoleyl alcohol and pentadecafluorooctanoic acid were added to p-
The reaction was carried out using toluenesulfonic acid as a catalyst.

bp 135~139 ℃ (0.2mmHg) IR 1210~1380cm -1 1780cm -1 2850~3020cm -1 M - is applied to Co by 663 Example 14μm thick oblique deposition polyethylene terephthalate film, a thickness of 1000Å strong A magnetic metal thin film was formed.

Next, on the surface of the ferromagnetic metal thin film, perfluoroalkylcarboxylic acid ester (synthesized in the previous synthesis example) shown in Table 1 and a composite type extreme pressure agent (weight ratio 1: 1) solvent (acetone: ethyl) were used. The solution diluted with ether = 1: 1) has a coating amount of 1
A sample tape was prepared by applying the solution so that the amount would be 0 mg / m ² and cutting it to a width of 1/2 inch. The trilauryl thiophosphate used here as the complex type extreme pressure agent is represented by the general formula (C ₁₂ H ₂₅ S) ₃ P, and diisopropyldithiophosphoric acid is represented by the general formula. It is represented by.

With respect to each of the prepared sample tapes, the dynamic friction coefficient and the shuttle durability under the conditions of a temperature of 25 ° C., a relative humidity (RH) of 50%, and −5 ° C. were measured. This dynamic friction coefficient is
This is a test using a guide pin made of stainless steel (SUS304) with a constant tension and a speed of 5 mm / sec. Further, the shuttle durability was evaluated by the number of shuttles until the output decreased by -3 dB after the shuttle traveled for 2 minutes each time. For still durability, the decay time of the output up to −3 dB in the paused state was evaluated. In addition, as a comparative example, a blank tape on which no lubricant was applied was also measured.

The results are shown in Table 2.

As is clear from this table, in each of the examples of the present invention, the coefficient of dynamic friction is small under normal temperature and constant temperature conditions, the running is extremely stable, and the tape surface is not damaged even after 100 round trips. I couldn't see it at all. Also, the durability was extremely good, and the output did not decrease by -3 dB even after 150 shuttles. On the other hand, in the tape of the comparative example having no lubricant layer, the coefficient of friction increased as the number of times of reciprocation was increased, the operation was unstable, the tape was worn, and the durability was poor.

〔The invention's effect〕

As is clear from the above description, in the present invention,
Since the perfluoroalkylcarboxylic acid ester and the composite type extreme pressure agent are used as the lubricant of the ferromagnetic metal thin film type magnetic recording medium, the dynamic friction coefficient can be made small under any temperature condition, and the running stability and A magnetic recording medium having excellent wear resistance can be obtained.

In particular, since the freezing point temperature of perfluoroalkylcarboxylic acid ester is low, the effect is great when used at low temperatures.

Furthermore, the combined use of the combined extreme pressure agent increases the adhesion to the ferromagnetic metal thin film, and the lubrication effect is maintained for a long period of time. It can be used well even under the conditions of use.

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Claims (2)

[Claims] 1. A ferromagnetic metal thin film is formed on a non-magnetic support, and a lubricant layer containing a perfluoroalkylcarboxylic acid ester and a composite extreme pressure agent is deposited on the ferromagnetic metal thin film. And a magnetic recording medium. 2. A perfluoroalkylcarboxylic acid ester having the general formula C _n F _{2n + 1} COOR (wherein n represents an integer of 6 to 10 and R represents a hydrocarbon group of 9 to 25 carbon atoms). )
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a compound represented by: