JPS62236120A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the traveling property, wear resistance, and durability of the titled medium by forming a topcoat layer contg. the perfluoroalkyl ester of a carboxylic acid and an extreme-pressure agent on a ferromagnetic metallic thin film which is the magnetic layer. CONSTITUTION:A lubricant obtained by adding resinous extreme-pressure agents of all kinds into the perfluoroalkyl ester of a carboxylic acid which is the ester of an aliphatic carboxylic acid and a perfluoroalcohol exhibits an excellent lubricating effect over a wide temp. range. Accordingly, the ferromagnetic metallic thin film is formed on a nonmagnetic carrier, and the topcoat layer contg. the perfluoroalkyl ester of a carboxylic acid and the extreme-pressure agent is formed on the ferromagnetic metallic thin film. Consequently, the traveling property, durability, and wear resistance of the medium are improved.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to the production of ferromagnetic gold rsfl on a non-magnetic support by vacuum thin film forming techniques such as vacuum evaporation and sputtering.
The present invention relates to a so-called ferromagnetic metal thin film type magnetic recording medium in which an i-film is formed as a magnetic layer.

[Summary of the invention]

The present invention provides a magnetic recording medium in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support, and a top layer containing a carboxylic acid perfluoroalkyl ester and an extreme pressure agent on the ferromagnetic metal thin film as the magnetic layer. Forms a coating layer that provides excellent running performance under all conditions of use.

The objective is to provide a magnetic recording medium that exhibits wear resistance and durability.

[Conventional technology]

Conventionally, as a magnetic recording medium, r-
F6g03. r F ez O, containing co.

Fesoa containing Fe5Oe+Co, T-F
e Bertolide compound of zOx and Fe5O4, Co
Powder magnetic materials such as ferromagnetic powders such as ferromagnetic oxide powders such as Bertolide compounds and Crag, or alloy magnetic powders containing Fe, Co, Ni, etc. as main components are combined with vinyl chloride-vinyl acetate copolymers, polyester resins, and polyurethane. Coating-type magnetic recording media, which are manufactured by coating and drying a magnetic paint dispersed in an organic binder such as a side surface, are widely used.

On the other hand, with the increasing demand for high-density magnetic recording, ferromagnetic metal materials such as Co-Ni alloys have been made into polyester by plating or vacuum thin film formation technology (vacuum evaporation, sputtering, ion blating, etc.). A so-called ferromagnetic metal thin film type magnetic recording medium, which is directly deposited on a non-magnetic support such as a film or a polyimide film, has been proposed and is attracting attention. This ferromagnetic metal thin film magnetic recording medium not only has excellent coercive force and squareness, and excellent electromagnetic conversion characteristics at short wavelengths, but also has the ability to reduce the magnetic layer thickness by making it extremely thin. It has a number of advantages, including extremely low thickness loss during magnetization and reproduction, and the ability to increase the packing density of the magnetic material because there is no need to mix an organic binder, which is a non-magnetic material, into the magnetic layer. .

However, in the above-mentioned ferromagnetic metal thin film type magnetic recording medium, the surface smoothness of the magnetic layer is extremely good, so the substantial contact area is large, and adhesion phenomena (so-called sticking) are likely to occur. ! It has many shortcomings in terms of durability, running performance, etc., such as a large coefficient of friction, and improvement of these problems has become a major issue.

In general, a magnetic recording medium is subjected to high-speed relative motion with a magnetic head during the process of recording and reproducing magnetic signals, and during this time, it must run smoothly and stably. It is better to minimize wear and damage caused by contact with the head.

For example, attempts have been made to improve the durability and runnability by coating the magnetic layer of the magnetic recording medium, that is, the ferromagnetic metal thin film, with a lubricant to form a protective film.

[Problem that the invention seeks to solve]

By the way, when a protective film is formed by applying a lubricant as described above, this protective film is a ferromagnetic metal that is a magnetic layer.
It is required to exhibit good adhesion to 1 tla and to exhibit a high lubricating effect.

In addition, these adhesion properties and lubrication effects must be excellent both under hot and humid conditions, such as in tropical and subtropical regions, and under low-temperature conditions, such as in cold regions.

However, the operating temperature range of conventionally widely used lubricants is limited, and in particular, many of them solidify or freeze at low temperatures such as O to -5℃, so it is difficult to fully demonstrate their lubricating effect. I couldn't do that.

Therefore, the present invention provides (1) a top coat layer that maintains adhesion and lubricity under any usage conditions and maintains a lubricating effect over a long period of time; The object of the present invention is to provide a magnetic recording medium having excellent running properties and durability by forming the magnetic recording medium on a magnetic metal thin film.

[Failure to solve the problem]

As a result of intensive research, the present inventors have discovered that a lubricant containing various extreme pressure agents added to carboxylic acid perfluoroalkyl ester, which is an ester of aliphatic carboxylic acid and perfluoroalcohol, has been developed. The present invention has been completed by discovering that a good lubrication effect can be exhibited over a wide temperature range. It is characterized in that a top coat layer containing a carboxylic acid perfluoroalkyl ester and an extreme pressure agent is formed.

The carboxylic acid perfluorofurkyl ester used as a lubricant in the present invention has the general formula % (1) (However, in the above general formula, m≦2n+l.

j≧0. is ≧4. ) is a compound represented by Here, the alkyl group (-C, H,) of the carboxylic acid may be linear or monobranched, or may contain a double bond.

On the other hand, the number of carbon atoms in the perfluoroalkyl group (-CkFz*, +) is preferably 4 or more, and more preferably 6 or more.

Carboxylic acid perfluoroalkyl esters are easily synthesized, for example, by reacting a corresponding acid chloride with a fluorine-containing alcohol. The reaction formula is as follows.

C11ItlICOCR+ CbF□, +(Cut)t
OH base CIlIt-CoCl1It-Coo (CH+...+
The above acid chloride of formula 11 can be easily synthesized by chlorinating a commercially available aliphatic carboxylic acid with 1 g of phosphorus pentachloride PCl5 or thionyl chloride SOC. In particular, for aliphatic carboxylic acids with small carbon number n, thionyl chloride S
The 0 reaction formula that can be synthesized by chlorination with OC1z is as follows.

Cl5C,H,C0OH-Cl111. cOcl...(2)
Formula: On the other hand, fluorine-containing alcohol CJtk++ (Cut)
For 70H, perfluorocarboxylic acid obtained by the Simmons method etc. was mixed with dimethylformamide (DMF
) can be easily synthesized by chlorination in the presence of a compound, followed by reduction with a reducing agent.

The reaction formula is as follows.

OC1g DMF...Formula (3) And, in the present invention, in order to cope with more severe usage conditions and maintain the lubricating effect, the above carboxylic acid perfluoroalkyl ester is added at a weight ratio of 30?
An extreme pressure agent is used in combination at a blending ratio of about 70:30.

When the extreme pressure agent makes partial metal contact in the boundary lubrication area, it reacts with the metal surface due to the accompanying frictional heat, forming a reaction product film to prevent friction and wear. Among these, phosphorus-based extreme pressure agents, sulfur-based extreme pressure agents, halogen-based extreme pressure agents, metal-based extreme pressure agents, composite type extreme pressure agents, etc. are known.

Specifically, the phosphorus-based extreme pressure agents include tributyl phosphate, trioctyl phosphate, tri-2-ethylhexyl phosphate, trilauryl phosphate, trioleyl phosphate, dibutyl phosphate, dioctyl phosphate, and di-2-ethyl phosphate. Phosphate esters such as xyl phosphate, dilauryl phosphate, dioleyl phosphate, tributyl phosphite, trioctyl phosphite, tri-2-ethylhexyl phosphite, trilauryl phosphite, trioleyl phosphite, dibutyl phosphite, dioctyl phosphite , di-2-ethylhexyl phosphite, dilauryl phosphite, dioleyl phosphite and other phosphite esters, dibutyl phosphate butylamine salts.

Dibutylphosphate octylamine salt, dibutylphosphate-1-stearylamine salt, dioctylphosphate butylamine salt, dioctylphosphate octylamine salt, dioctylphosphate laurylamine salt, dioctylphosphate stearylamine salt, di-2-ethylhexylphosphate butylamine salt, di-2-ethylhexylphosphate butylamine salt, 2-Ethylhexylphosphate octylamine salt, di-2-
Ethylhexylphosphate laurylamine salt, G2
-Ethylhexylphosphate stearylamine salt, dilaurylphosphate butylamine salt.

dilauryl phosphate octylamine salt, dilauryl phosphate traurylamine salt, dilauryl phosphate stearylamine salt, dioleyl phosphate butylamine salt, dioleyl phosphate octylamine salt,
Examples include phosphate ester amine salts such as dioleyl phosphate lauryl amine salt and dioleyl phosphate stearyl amine salt.

The above-mentioned sulfur-based extreme pressure agents include mineral oils with unsaturated bonds such as sulfurized whale oil and sulfurized dipentene, sulfurized oils and fats produced by adding sulfur to fats and oils and fatty acids, and heating them, dibenzyl disulfide, and disulfide. Diphenyl, di-monobutyl disulfide, di-5ec-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
- Monosulfides such as butyl, di-5ec-butyl sulfide, di-n-butyl sulfide, polysulfides such as dimethyl trisulfide, di-t-butyl trisulfide, di-1-nonyl polysulfide, and olefin polysulfide, general formula % Examples include thiocarbonates represented by the formula %( ) (wherein R represents a hydrocarbon group), elemental sulfur, and the like.

The halogen-based extreme pressure agent is allyl bromide.

Bromine compounds such as octadecyl bromide, cyclohexyl bromide, stearyl bromide, benzyl bromide, iodine compounds such as benzyl iodide, allyl iodide, butyl iodide, octadecyl iodide, cyclohexyl iodide, hexachloroethane, monochloroethane.

Examples include chlorine compounds such as chlorinated paraffin, chlorinated diphenyl, chlorinated oil and fat, methyl trichlorostearate, pentachloropentadienoic acid, ester of hexachloronaphthenic acid compound, and imide VA conductor of hexachloronaphthenic acid compound.

Examples of the organometallic extreme pressure agents include zinc diisobutyldithiophosphate, zinc isobutylpentyldithiophosphate, isopropyl-1-methylbutyldithiophosphate, zinc isobutylnonylphenyldithiophosphate, isobutylheptylphenyldithiophosphate, diheptylphenyldithiophosphate, Zinc nonylphenyl dithiophosphate, thiophosphates such as molybdenum dithiophosphate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc dimethyldithiocarbamate, dimethyldithiocarbamate Examples include copper, thiocarbamates such as iron dimethyldithiocarbamate, selenium diethyldithiocarbamate, and silver diethyldithiocarbamate, and metal alkyldithiocarbamates such as molybdenum and antimony.

Examples of the composite extreme pressure agent include dialkylthiophosphate amines such as di-2-ethylhexylthiophosphate amine, propyl chloride, propyl bromide phosphate,
In addition to phosphoric acid esters of alkyl halides such as propyl iodide, butyl chloride, butyl bromide, butyl iodide, etc., chloronaphsasanthate, etc., general formulas (however, in each general formula, R represents a hydrogen atom or an alkyl group, an alkenyl group, or an aryl group); thiophosphates represented by the formula -a (wherein R represents a hydrogen atom or an alkyl group, an alkenyl group, or an aryl group) Thiophosphites, etc., are highly effective.

The above-mentioned extreme pressure agents may be used alone, but it is also possible to use a mixture of two or more types.

In addition to the above-mentioned carboxylic acid perfluoroalkyl ester and extreme pressure agent, a conventionally known lubricant may be used in combination to further expand the usable temperature range.

The lubricants used include fatty acids or their metal salts;
Fatty acid amide, fatty acid ester, fatty alcohol or its alkoxide, fatty amine, polyhydric alcohol,
Vine and tan esters, manniratan esters, sulfurized fatty acids, aliphatic mercaptans, modified silicone oils, perfluoroalkyl ethylene oxides, perfluoropolyethers, higher alkyl sulfonic acids or their metal salts, perfluoroalkyl sulfonic acids or their ammonium salts Examples include metal salts thereof, perfluoroalkylcarboxylic acids or metal salts thereof, and perfluoroalkylcarboxylic acid esters.

In particular, general formulas C, F! Perfluoroalkylcarboxylic acid esters represented by A-I COOR (where n represents an integer of 6 to 10 and R represents a hydrocarbon group having 1 to 25 carbon atoms) also have good low-temperature properties. Therefore, it is suitable for use in combination with the above carboxylic acid perfluoroalkyl ester.

Moreover, a rust preventive agent may be used in combination as necessary.

As the rust preventive agent that can be used, any rust preventive agent that is normally used as a rust preventive agent for this type of magnetic recording medium may be used, such as dihydric phenol.

Phenols such as alkylphenol or nitrosophenol, naphthols such as pure naphthol or nitro-, nitroso-, amino-, or halogeno-substituted naphthol, methylquinone, hydroxyquinone.

Quinones such as aminoquinone, nitroquinone or halogen quinone, diaryl ketones such as benzophenone and its derivatives hydroxyhemsiphenone and aminobenzophenone, acridine, 4-quinolitool, heterocyclic compounds containing a nitrogen atom such as kynurenic acid or riboflavin, tocopherol or Heterocyclic compounds containing an oxygen atom such as guanosine, heterocyclic compounds containing a sulfur atom such as sulfolane, sulfolene or bithione, compounds having a mercapto group such as thiophenol, dithizone or thiooxin, thiocarboxylic acids such as entathioic acid or rubeanic acid, or Salts thereof, diazosulfide, thiazole compounds such as benzothiazoline, etc. can be mentioned. The above-mentioned rust preventive agent may be used in combination with a lubricant, but for example, the above-mentioned rust preventive agent is first applied to the surface of a ferromagnetic metal thin film, and then a lubricant is applied thereto. It is more effective if applied separately.

A method for depositing a lubricant layer containing these carboxylic acid perfluoroalkyl esters on a ferromagnetic metal gIM is to apply or spray a solution obtained by dissolving the above lubricant in a solvent onto the surface of a ferromagnetic metal thin film. Alternatively, ferromagnetic gold 171mB may be immersed in this solution and dried.

Here, the coating amount is 0.5■/lyl to 100■/lyl
ITr is preferable, and 1■/- to 20■/d is more preferable. If this coating amount is too small, the effects of lowering the friction coefficient and improving wear resistance and durability will not be realized. On the other hand, if the amount is too large, a sticking phenomenon will occur between the sliding member and the ferromagnetic metal thin film, which will actually worsen running performance.

The magnetic recording medium to which the present invention is applied is one in which a ferromagnetic metal iWa is provided as a magnetic layer on a nonmagnetic support.
Examples of materials for the nonmagnetic support include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate, polyvinyl chloride,
Vinyl resins such as polyvinylidene chloride, plastics such as polycarbonate, polyimide, polyamideimide,
Examples include light metals such as aluminum alloys and titanium alloys, and ceramics such as alumina glass.

The forms of this non-magnetic support include film, sheet,
It may be a disk, card, drum, etc.

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

For example, the above-mentioned mountain-like protrusions have a particle size of 5 when forming a polymer film.
It is formed by internally adding inorganic fine particles of about 0.00 to 3000, and the height from the polymer film surface is 100 to 3000.
1000 individuals, density approximately lXl0' to toxto' individuals/2 fins. Calcium carbonate (CaCOs), silica, alumina, etc. are suitable as the inorganic fine particles used to form the mountain-like protrusions.

The wrinkle-like protrusions are undulations formed by applying and drying a dilute gI solution of resin using a specific mixed solvent, and the height thereof is 0.01 to 108 m, preferably 0.03 to 0.0 m. .5μm, the shortest distance between protrusions is O,1~2
011m. Examples of the resin for forming the wrinkled projections include saturated polyesters such as polyethylene terephthalate 8 polyethylene naphthalate, polyamides, polystyrene, polycarbonates, polyacrylates, polysulfones, polyethersulfones, polyvinyl chloride,
It is a single substance, a mixture, or a copolymer of various resins such as polyvinylidene chloride, polyvinyl butyral, polyphenylene oxide, and phenoxy resin, and those having a soluble solvent are used. Then, to a solution of these resins dissolved in the good solvent with a resin concentration of 1 to 10001) If, a solvent that is a poor solvent for the resin and has a boiling point higher than the good solvent is added at 1 G- By applying a solution added in 100 times the amount to the surface of a polymer film and drying it, 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 semispherical shape. The height of this granular protrusion is
50 to 500 people, density 1XIOh to 50X10-pieces/
fl wealth level.

The surface properties of the ferromagnetic metal thin film that is the magnetic layer can be controlled by forming at least one type of these protrusions, but the effect is enhanced by combining two or more types. By forming protrusions and bulge-like protrusions, durability and running properties are greatly improved.

In this case, the overall height of the protrusion is 100 to 200
Preferably within the range of 0 people, the density is 1m”
It is preferable that the number is 1X10'-IXIO' on average.

Further, 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 evaporation method, an ion blating method, or a sputtering method.

In the vacuum evaporation method described above, a ferromagnetic metal material is evaporated under a vacuum of 10-4 to 10-Torr by resistance heating, high-frequency heating, electron beam heating, etc., and the evaporated metal (
In order to obtain a high coercive force, an oblique evaporation method is adopted in which the ferromagnetic metal material is deposited obliquely to the substrate. or,
It also includes those in which the above-mentioned vapor deposition is performed in an oxygen atmosphere in order to obtain higher coercive force.

The above-mentioned ion brating method is also a type of vacuum evaporation method, in which DC glow discharge and RFFa-discharge are caused in an inert gas atmosphere of 1 O-4 to 1 O-'' Torr, and the above-mentioned ferromagnetic metal material is deposited during the discharge. It is evaporated.

The above sputtering method uses 10-" to l O-'Tor
A glow discharge is caused in an atmosphere mainly composed of argon gas, and the generated argon gas ions are used to knock out atoms on the target surface. There are sputtering methods, magnetron sputtering methods using magnetron discharge, and the like.

In the case of this sputtering method, Cr or W is used.

A base film such as V may be formed in advance.

In any of the above methods, Bi, Sb, Pb, Sn, Ga, and In are preliminarily deposited on the substrate.

By pre-depositing a base metal layer such as Cd, Ge, Si, Tl1, etc., and forming the film from a direction perpendicular to the substrate surface, excellent magnetic properties can be achieved in the in-plane direction without magnetic anisotropy orientation. It is suitable for forming a layer, for example, into a magnetic disk.

When forming a metal magnetic thin film using such vacuum thin film forming technology, the ferromagnetic metal materials used include Fe,
In addition to metals such as Co and Ni, C.

-Ni alloy, Co-Pt alloy, Co-Ni-Pt alloy,
Fe-Co alloy, Fa-Ni alloy, Fe-Co-Ni alloy, Fe-Go-B alloy, Co-N1-Fe-B alloy,
Examples include Go-Cr alloys and those containing metals such as Cr and An. In particular, when a Co--Cr alloy is used, a perpendicularly magnetized film is formed.

The thickness of the magnetic layer formed by such a method is 0.
It is about 0.04 to 1 μm.

In addition, a so-called back coat layer may be formed on the side of the non-magnetic support opposite to the side on which the magnetic layer is provided. Alternatively, a binder resin such as a butadiene copolymer and a powder component such as a carbon-based fine powder to impart IT properties or an inorganic pigment added to control surface roughness and improve durability are combined with acetone, methyl ethyl ketone, etc. Alternatively, it can be formed by applying a bank coating paint mixed and dispersed in an organic solvent such as benzene to the surface of a non-magnetic support.

A lubricant may be used in the bank coat layer. In this case, the lubricant may be internally added to the back coat layer, or the lubricant may be deposited on the bank coat layer. In any case, the above-mentioned lubricants include fatty acids,
Conventionally known lubricants such as fatty acid esters, fatty acid amides, metal soaps, fatty alcohols, paraffins, and silicones can be used.

[Effect]

A lubricant layer containing a carboxylic acid perfluoroalkyl ester and an extreme pressure agent exhibits a good lubricating effect and reduces the coefficient of friction by being formed as a top coat layer on a ferromagnetic metal thin film. In particular, carboxylic acid perfluoroalkyl esters exhibit good lubricating effects even at low temperatures.

[Examples] Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

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

Synthesis example Commercially available oleic acid, linoleic acid, lylunic acid.

Myristic acid and palmitic acid are each converted into phosphorus pentachloride (P).
C1%) or thionyl chloride (SOCIg) to obtain the corresponding carboxylic acid chloride. Note that a commercially available pucunyl chloride was used.

On the other hand, pentadecafluorooctanoic acid or nonadecafluorodecanoic acid is chlorinated with thionyl chloride (SOCI□) using dimethylformamide (DMF) as a catalyst, and then reduced with lithium aluminum hydride to produce pentadecafluoro-1-octatool. and nonadecafluoro-1-
Synthesized decanol.

Next, the above pentadecafluoro-1-octatool or nonadecafluoro-1-decanol was dissolved in chloroform together with triethylamine, and one of the carboxylic acid chlorides synthesized earlier was added dropwise over 30 minutes under water cooling. After completion of the dropwise addition, the mixture was stirred at room temperature overnight. This was washed with water, 5% diluted hydrochloric acid, 1'Ja) (C0w aqueous solution, and water), and purified by vacuum distillation.

According to the above synthesis method, eight types of compounds were synthesized by changing the type of carboxylic acid chloride.

Confirmation of the product was performed using infrared spectroscopy (IR) and mass spectrometry (
For example, in the case of oleic acid pentadecafluorooctyl ester, 1360-1
Absorption peculiar to CF bond is observed at 100c Peng-1, absorption of C=0 of ester is observed at 1760cm-', 3020cs+-' and 2930c+e-
It was confirmed from the fact that absorption due to CI stretching vibration was observed in '. In addition, the mass spectrum obtained by mass spectrometry shows that 66
The presence of the molecular ion peak M′ of 4 also supports this structure. The above mass spectrometer is manufactured by JEOL Ltd.

The measurement was performed using a mass spectrometer DX303, and the measurement was performed after confirming that it was a single component using a gas chromatograph.

Example 1 Co was deposited on a polyethylene terephthalate film having a thickness of 4 μm by oblique vapor deposition to form a ferromagnetic metal thin film having a thickness of 1000 μm.

Next, 0.48% of the carboxylic acid perfluoroalkyl ester synthesized in the previous synthesis example was placed on the surface of this ferromagnetic metal thin film.
Dissolve g in 800 g of freon and add 1 lb of extreme pressure agent to it.
A sample tape was prepared by applying a solution added at a ratio of 1:1 and cutting it into a width of 8 m. The type of carboxylic acid perfluoroalkyl ester and the name of the scratching agent used in each example are shown in Table 1 (11) and Table 1 (2).

(Leaving space below) Table 1 (1) Table 1 (2) Dynamic g-friction coefficient for each sample tape created under the conditions of 25°C, 50% relative humidity (RH), and -5°C and shuttle durability was measured. This dynamic friction coefficient was tested by using a gyrip pin made of stainless steel (SUS304) and feeding it at a speed of 5 as/sec under a constant tension. In addition, the shuttle durability was evaluated by running the shuttle for 2 minutes each time, and determining the number of shuttle runs until the output decreased by 13 dB. Methyl durability was evaluated by evaluating the decay time for the output to -3 dB in a pause state. The results are shown in Table 2 +11 and Table 2 (2).

Table 2 (1) Table 2 (2) As is clear from this table, each example of the present invention has a small dynamic friction coefficient under both normal temperature and low temperature conditions, and the running is extremely stable. Further, even after running back and forth 100 times, no damage was observed on the tape surface. Furthermore, the durability was extremely good, and even after 150 shuttle runs, no decrease in output by 13 dB was observed. On the other hand, in the tape of the comparative example without a lubricant layer, the friction coefficient increased as the number of reciprocating runs increased, running was unstable, tape wear was observed, and durability was poor.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since a top coat layer containing carboxylic acid perfluoroalkyl ester and a scratching agent is formed on the ferromagnetic metal F4 film type magnetic recording medium, the coefficient of dynamic friction can be reduced under any temperature conditions, making it possible to A magnetic recording medium with excellent stability and wear resistance can be obtained.

In particular, since the freezing point temperature of carboxylic acid perfluoroalkyl ester is low, it is highly effective when used at low temperatures.

Claims (1)

[Claims] A magnetic recording medium comprising: a ferromagnetic metal thin film formed on a non-magnetic support; and a top coat layer containing a carboxylic acid perfluoroalkyl ester and an extreme pressure agent formed on the ferromagnetic metal thin film.