JPH10204031A - Fluorinated alkyl carboxylic acid monoester and magnetic recording medium having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject new compound useful for a magnetic recording medium, etc., which is excellent in traveling, durability and weather resistance, at the same time, capable of holding reliability even under environments with a wide temperature range and free from the loss of lubricity under environments from low to high humidity. SOLUTION: A compound of formula I [R<1> is an aliphatic alkyl, etc.; R<2> is a fluoroalkyl; R<3> is O or S; R<4> is S or SC2 H4 S; (m) is an integer of 1-6; (n) is an integer of 1-30; (a) is 0, 1; (b) is 0, 1], e.g. a compound of formula II. A compound of formula I is obtained by reacting an alkylsuccinic anhydride such as dodecylsuccinic anhydride, etc., with a fluoroalkylene oxide-containing fluoroalkyl alcohol which is expressed by a general formula III (R<2> is a fluoroalkyl; R<3> is O or S), etc., in a solvent such as normal octane at 60-100 deg.C under heating stirring, removing the solvent from the reaction mixture by reduced pressure distillation and subsequently extracting the residue with an organic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel fluorine-containing compound useful as a lubricant for a precision machine, a precision part, a surfactant, a release agent, a rust inhibitor, etc., which require high precision lubrication. The present invention relates to a magnetic recording medium having the same.

[0002]

2. Description of the Related Art With the miniaturization and high precision of mechanical devices and parts, the lubrication mode of sliding parts thereof has also shifted from fluid lubrication to boundary lubrication. In particular, in electronic devices and electronic components such as VTRs and magnetic disks, the use of a ferromagnetic metal thin film for the purpose of improving recording density allows sliding between a magnetic recording medium such as a magnetic tape or a magnetic disk and a magnetic head. Has required high-precision lubrication. For example, in the case of vapor-deposited tapes and hard disks, the lubricant layer on the surface of the magnetic layer has only a few lubricant layers in order to minimize the spacing loss between the magnetic recording medium and the magnetic head while increasing the output while ensuring durability and reliability. It is formed to have a thickness of 10 mm. Therefore, development of an organic compound having excellent lubricity as a material for forming the lubricant layer is an important issue.

As a lubricant for a metal thin-film type magnetic recording medium, a long-chain carboxylic acid fluoroalkyl ester represented by the following chemical formula (for example, JP-A-62-46431) or a fluorocarbon represented by the following chemical formula (4) is used. There is an alkyl carboxylic acid monoester
(For example, JP-A-61-107529).

[0004]

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[0005]

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[0006]

However, the above-mentioned (Formula 3)
The lubricant of long-chain carboxylic acid fluoroalkyl ester represented by the formula (1) has reduced lubricity in a high-humidity environment, and the lubricant of fluoroalkyl carboxylic acid monoester represented by the formula (4) lubricates in a low-humidity environment. There is a problem that the property is reduced.

The present invention solves the above-mentioned conventional problems, and provides a magnetic recording medium which is excellent in running properties, durability and weather resistance, and which can be practically used in a wide range of temperature environments and maintain its reliability. Aim.

[0008]

In order to achieve the above object, a magnetic recording medium of the present invention comprises a ferromagnetic metal thin film provided on a nonmagnetic support, and a protective film provided on the ferromagnetic metal thin film. And a lubricant layer containing the fluorinated alkyl carboxylic acid monoester of the present invention.

The fluorine-containing alkyl carboxylic acid monoester used in the present invention is represented by the general formula (Chemical Formula 5), wherein the fluoroalkyl terminal group having one fluoroalkylene oxide chain in the same molecule is formed on the surface of the metal thin film. Alternatively, it is exposed to the surface of the protective film or the surface of the magnetic head to contribute to lowering the energy of the surface, and forms a non-adhesive surface.

Further, the fluoroalkylene oxide chain in the fluorine-containing alkyl carboxylic acid monoester molecule has a function of softening a rigid fluorine-containing hydrocarbon end chain due to the presence of the ether bonding group, so that good lubricity is obtained. It shows both non-adhesiveness and lubricity. In addition, the aliphatic hydrocarbon terminal group exhibits a good lubricity because it is a flexible carbon-carbon bond chain.

Further, the carboxyl group strongly adheres to the surface of the metal thin film or the surface of the protective film and the surface of the magnetic head.
Due to the synergistic effect of each of these terminal groups, the magnetic recording medium provided with a lubricant layer containing at least one kind of the fluorinated alkyl carboxylic acid monoester of the present invention has lubricity from a low humidity environment to a high humidity environment. An excellent effect of not decreasing is obtained.

[0012]

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Here, R ₁ represents an aliphatic alkyl group or an aliphatic alkenyl group, R ₂ represents a fluoroalkyl group, R ₃ represents —O— or —S—, and R ₄ represents —S— or —S. S
C ₂ H ₄ S—, m is an integer of 1 to 6, and n is 1
A is 0 or 1, and b is 0 or 1.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The fluorine-containing alkyl carboxylic acid monoester used in the present invention includes a fluoroalkyl terminal group represented by the aforementioned general formula (Formula 5) and having one fluoroalkylene oxide chain in the same molecule. 1. A structure having one aliphatic hydrocarbon terminal group, that is, an aliphatic alkyl terminal group or an aliphatic alkenyl terminal group, and a carboxyl group. Here, R ₁ in the above (Chemical Formula 5) has a carbon number of 6 to 30, preferably 10 to 24, and if the carbon number is less than 6 or more than 30, the lubricity decreases. R ₂ is a fluoroalkyl group having 1 to 30, preferably 1 to 8 carbon atoms, m is an integer of 1 to 6, n is an integer of 1 to 30, and preferably 1 to 8; , M, and n are out of these ranges, the lubricity and storage reliability are reduced. R ₃ is —O— or —S—, and R ₄ is —
S- or -SC ₂ H ₄ is S-, a is 0 or 1, b is 0 or 1.

[0015] The fluorine-containing alkyl carboxylic acid monoester represented by general formula (6) using a fluorosilicone alkylene oxide fluoroalkyl alcohol or fluoroalkyl fluoroalkyl thiol with alkylene oxide groups with group as a starting material, carbon as R ₂ The number is 1 to 30, preferably 1 to 8, a fluoroalkyl group, m is an integer of 1 to 6, n is an integer of 1 to 30, preferably 1 to 8, and R ₃ is preferably -O- or -S-.

[0016]

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[0017] wherein R ₂ represents a fluoroalkyl group, R ₃
Represents -O- or -S-, m is an integer of 1 to 6,
n is an integer of 1 to 30.

This lubricant layer is prepared by adding a fluorinated alkyl carboxylic acid monoester represented by the general formula (5) or a fluorinated alkyl carboxylic acid monoester and other lubricants, rust preventives, extreme pressure agents and the like. On a thin layer. The mixing ratio is suitably at least 40 mol%, preferably at least 60 mol%, based on the total amount of the mixture. If the content of the fluorinated alkyl carboxylic acid monoester is less than 40 mol%, it is difficult to obtain the effects of the present invention. Its abundance surface 1 m ² per 0.05 to 100
mg, preferably in the range of 0.1 to 50 mg, is suitable. As the other lubricant and rust preventive, a fluorine-containing compound is preferable, and a liquid fluorine-containing compound is more preferable. The addition amount is suitably in the range of 0 to 60%, preferably 0 to 40%.
If it is less than 40%, it is difficult to obtain the effects of the present invention.

As the protective film, a carbon thin film in an amorphous state, a graphite state, a diamond state, a mixed state thereof, or a laminated state obtained by a method such as sputtering or plasma CVD can be applied.
50-500 ° is preferred.

The process for producing the fluorinated alkyl carboxylic acid monoester used in the present invention includes alkyl succinic anhydride or alkenyl succinic anhydride or alkylthio succinic anhydride or alkenylthio succinic anhydride and a fluoroalkyl alcohol having a fluoroalkylene oxide group or The mixture is mixed with a fluoroalkylene thiol-added fluoroalkyl thiol and heated with stirring. 60 ~ 10 as heating temperature
0 ° C, preferably 80-90 ° C. If it is lower than this range, unreacted substances tend to remain, while if it is higher, by-products tend to be formed.

The alkyl succinic anhydride or alkenyl succinic anhydride or alkylthio succinic anhydride or alkenylthio succinic anhydride that can be used includes dodecyl succinic anhydride, tridecyl succinic anhydride, tetradecyl succinic anhydride, pentadecyl succinic anhydride, hexadecyl anhydride. Succinic acid, heptadecyl succinic anhydride, octadecyl succinic anhydride, nonadecyl succinic anhydride, icosyl succinic anhydride, henicosyl succinic anhydride, docosyl succinic anhydride, dodecenyl succinic anhydride, tridecenyl succinic anhydride, tetradecenyl succinic anhydride, pentadecenyl anhydride Succinic acid, hexadecenyl succinic anhydride, heptadecenyl succinic anhydride, octadecenyl succinic anhydride, nonadecenyl succinic anhydride, icosenyl succinic anhydride, henicocenyl Water succinic, docosenyl succinic anhydride, dodecylthio succinic anhydride, tridecylthio succinic anhydride, tetradecylthio succinic anhydride, pentadecyl thio succinic anhydride, hexadecylthio succinic anhydride,
Heptadecylthio succinic anhydride, otacdecylthio succinic anhydride, nonadecyl succinic anhydride, icosylthio succinic anhydride, henicosylthio succinic anhydride, docosylthio succinic anhydride, dodecenylthio succinic anhydride, tridecenylthio succinic anhydride, tetradecenyl succinic anhydride, pentadecenyl succinic anhydride Ruthiosuccinic anhydride, hexadecenylthiosuccinic anhydride, heptadecenylthiosuccinic anhydride,
There are octadecenylthio succinic anhydride, nonadecenylthio succinic anhydride, icosenylthio succinic anhydride, henicocenylthio succinic anhydride, and docosenylthio succinic anhydride.

The fluoroalkylene oxide-containing fluoroalkyl alcohol or fluoroalkylene oxide-containing fluoroalkylthiol is preferably a perfluoro-alkyl thiol.
3,7,11-trioxahexadecylmethanol, perfluoro-2,5,8,11,14,17,20-heptaoxaheptacosylmethanol, perfluoro-4,9,14-trioxatetrasilmethanol , Perfluoro-3,7,1
1-trioxahexadecylmethylthiol, perfluoro-2,5,8,11,14,17,20-heptaoxaheptacosylmethylthiol, perfluoro-4,9,14-trioxatetrasylmethylthiol is there. The reaction of an alkyl succinic anhydride or an alkenyl succinic anhydride, an alkylthio succinic anhydride or an alkenylthio succinic anhydride with a fluoroalkylene oxide-containing fluoroalkyl alcohol or a fluoroalkylene oxide group-containing fluoroalkylthiol is carried out by heating and stirring in the presence of a solvent. Proceeds conveniently. The solvent includes normal octane and normal heptane.

The molar ratio of alkyl succinic anhydride or alkenyl succinic anhydride or alkylthio succinic anhydride or alkenylthio succinic anhydride to fluoroalkylene oxide-containing fluoroalkyl alcohol or fluoroalkylene oxide-containing fluoroalkylthiol is as follows:
Equimolar.

In order to isolate the target compound from the obtained mixture, the solvent is first removed by distillation under reduced pressure, and the residue is extracted with an organic solvent to obtain a fluorine-containing alkyl carboxylic acid monoester of the compound. This compound is identified by infrared spectroscopy (IR),
It can be identified by gel permeation chromatography (GPC) and organic mass spectrometry (FD-MS).

[0025]

The embodiments of the present invention will be specifically described below.

Example 1 The chemical formula of the substance of Example 1 is
It is shown by (Formula 7).

[0027]

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The substance of the formula (7) will be described in comparison with the general formula of the formula (5). R ₁ is a hexadecyl group having 16 carbon atoms.
R ₂ is a fluoroalkyl group having 5 carbon atoms bonded to fluorine, m is 3, n is 2, R ₃ is —O—, and a is 1
And b is 0.

Next, a method for producing the substance represented by the formula (7) will be described.

The starting materials are 32.5 g (0.10 mol) of hexadecylsuccinic anhydride represented by (Chemical Formula 8) and 74.8 g (0.10 mol) of fluoroalkyl alcohol having a fluoroalkylene oxyside group represented by (Chemical Formula 9).

[0031]

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[0032]

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The above raw materials and 500 ml of normal heptane were collected in a 1-liter flask equipped with a stirring blade,
The reaction was performed for 24 hours. After completion of the reaction, normal heptane was distilled off, the reaction mixture was dissolved in benzene, and cooled to -10 ° C to remove unreacted hexadecyl succinic anhydride. Further, the reaction mixture was treated as a methanol solution to remove unreacted fluoroalkylene oxide group-containing fluoroalkyl alcohol by the same treatment to obtain 107 g of a white semi-solid.
This white semi-solid is analyzed by infrared spectroscopy (IR), gel permeation chromatography (GPC) and organic mass spectrometry.
(FD-MS) shows no starting materials and no by-products
It was found to be a substance represented by the formula (Chem. 7). FIG. 1 shows the result of infrared spectroscopy (spectrum) of this compound, in which the horizontal axis represents wavelength (cm- ¹ ) and the vertical axis represents transmittance (%).

[0034] IR; 1,775cm ~ ¹ absorption peak and the absorption peak extinction of 3,330cm ~ ¹ alcohol anhydride, 1,705cm ~ ^1-carboxylic acid, the absorption peaks appearing between 1,760cm ~ ¹ ester. GPC: Fluoroalkylene oxide-containing fluoroalkyl alcohol, hexadecyl succinic anhydride not detected. FD-MS; main peak at m / e 1,072.

In Example 1, the compound represented by the general formula (Formula 5)
R ₁ is a hexadecyl group having 16 carbon atoms, R ₂ is a fluoroalkyl group having 5 carbon atoms, m is 3, n is 2, a is 1 and b is
Has been described above, but also in the case where the structure is different from this, the starting material is changed, for example,
Or by using (Chemical Formula 11)
(Formula 13) can be produced.

Hexadecyl succinic anhydride was used as the aliphatic alkyl succinic anhydride, but the starting material was changed to aliphatic alkenyl succinic anhydride, for example,
Alternatively, by using (Chemical Formula 15) as an aliphatic alkylthio succinic anhydride, for example, (Chemical Formula 16) as an aliphatic alkenylthio succinic anhydride, such as (Chemical Formula 17),
Or (Chem. 19) or (Chem. 20) or (Chem. 21) can be produced.

[0037]

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[0038]

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[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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[0044]

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[0045]

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[0046]

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[0047]

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[0048]

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(Embodiment 2) Next, embodiments of the magnetic recording medium of the present invention will be specifically described, but the present invention is not limited to these embodiments.

The nonmagnetic support of the magnetic recording medium of the second embodiment, gradual granular projections of the gradient on silica fine particles added to the polyester film (average height 70 Å, diameter 1 [mu] m) several strikes surface 100 [mu] m ² A polyester film with a diameter of 150 mm, which is present and minimizes relatively large protrusions due to fine particles caused by the polymerization catalyst residue
Of silica colloid particles as nuclei and steep mountain-like projections using an ultraviolet-curable epoxy resin as a binder were formed so as to be 1 × 10 ⁷ per 1 mm ² . Then, a Co—Ni ferromagnetic film (Ni content: 20%, film thickness: 1000 ° C.) was provided on the nonmagnetic support by a continuous vacuum oblique deposition method in the presence of a small amount of oxygen. The oxygen content in the ferromagnetic film was 5% in atomic fraction.

Next, a plasma CV is formed on the ferromagnetic film.
After a protective film of diamond-like carbon having a thickness of 50 ° was formed by the method D, the fluoroalkylcarboxylic acid monoester represented by the formula (Formula 7) was applied on the protective film for 1 m.
^A lubricant layer was formed by coating so as to have an amount of 10 mg per ² and then cut into a predetermined width to produce a magnetic tape.
The magnetic tape was put on a commercially available VCR in an environment of 5 ° C, 10% RH and 40 ° C, 80% RH, and the output characteristics during still playback were measured. The RF output decreased by 3dB from the initial value or the output fluctuated. The still endurance time before the onset of the occurrence of was observed.

(Example 3) A magnetic tape was prepared from the magnetic tape of Example 2 by using (Formula 12) instead of (Formula 7), and the same test was performed.

(Example 4) In the magnetic tape of Example 2, (Chem. 7) was used instead of (Chem. 7), and a conventionally known lubricant C ₁₇ H _{33 was used.}
A similar test was conducted by preparing a magnetic tape using a mixture of COOC ₂ H ₄ C ₈ F ₁₇ at a weight ratio of 1: 1.

(Example 5) In the magnetic tape of Example 2, a mixture of (Chem. 7) in place of (Chem. 7) and a rust inhibitor (C ₁₈ H ₃₅ O) ₃ P at a weight ratio of 2: 1 was used. The same test was performed using the magnetic tape used.

The test results of Examples 2 to 5 are shown in (Table 1). The lubricants of Conventional Examples 1 and 2 in the table are (Chemical Formula 3),
It is shown in (Formula 4).

[0056]

[Table 1]

From Table 1, it can be seen that all the magnetic tape samples provided with the lubricant layer containing the fluorinated alkyl carboxylic acid monoester of the present invention have excellent lubricity at low humidity and high humidity. it is obvious. On the other hand, it is clear that the lubricating property of a conventional magnetic tape provided with a lubricant layer consisting of only a lubricant decreases in low humidity or high humidity.

In the examples, (Formula 7), (Formula 12), and (Formula 7)
And the known lubricant and the mixture of (Chem. 7) and the rust preventive agent were described, but (Chem. 13), (Chem. 18), (Chem. 19), (Chem. 20),
Similar effects can be obtained with the substances of the formulas (21), (22) and (23), and mixtures of these substances with conventionally known lubricants and rust preventives.

[0059]

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[0060]

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In the embodiment, phosphite has been described as a rust preventive.
Similar effects can be obtained with trithiophosphite, phosphate, thiophosphate, dithiophosphate, tetrathiophosphate, phosphonate, and phosphoric amide.

Embodiment 6 Next, another embodiment of the magnetic recording medium of the present invention will be described in detail.

The non-magnetic support of the magnetic recording medium of this embodiment has a thickness of 25 μm on a surface of an Al alloy plate having a diameter of 95 mm and a thickness of 1.2 mm.
A non-magnetic Ni-P alloy plating having an average roughness of 50 ° and a maximum height of 300 ° formed by texturing was used. A 1300 mm thick Cr underlayer and a 600 mm thick Co-Ni ferromagnetic film are formed by sputtering on the non-magnetic Ni-P alloy plating, and a 200 mm thick Co-Ni ferromagnetic film is formed on the ferromagnetic film by sputtering. A sample on which a graphite protective film was formed was designated as Sample A. 50mm thick by plasma CVD instead of graphite protective film
A sample on which a diamond-like carbon protective film was formed was designated as Sample B. Next, on the protective film of these samples
A fluorine-containing alkyl carboxylic acid monoester represented by the formula (Formula 7) was applied in an amount of 10 mg per 1 m ² to provide a lubricant layer, thereby producing a magnetic disk.

The magnetic disk was heated at 5 ° C., 10% RH and 40 ° C.
A CSS (contact start / stop) test was performed in an environment of 80 ° C. and 80% RH, and durability was determined based on the number of CSSs when the friction coefficient exceeded 1.0 or the number of CSSs when a head crash occurred.

(Example 7) A magnetic disk was prepared from the magnetic disk of Example 6, using (Formula 12) instead of (Formula 7), and the same test was performed.

(Embodiment 8) A magnetic disk was prepared from the magnetic disk of Embodiment 6 using the same lubricant as that of Embodiment 4 in place of (Formula 7), and the same test was conducted.

(Example 9) A magnetic disk was prepared from the magnetic disk of Example 6 using the same rust preventive agent as in Example 5 instead of (Formula 7), and the same test was performed.

Table 2 shows the test results of Examples 6 to 9 described above. The lubricants of Conventional Examples 3 and 4 in the table are (Chemical Formula 3), respectively.
It is shown in (Formula 4).

[0069]

[Table 2]

As shown in Table 2, all the magnetic disks provided with a lubricant layer containing at least one kind of the fluorinated alkyl carboxylic acid monoester of the present invention have excellent CSS durability in low humidity and high humidity. It is clear that there is. On the other hand, it is apparent that a conventional magnetic disk provided with a lubricant layer comprising only a lubricant has poor CSS durability in low or high humidity.

In the examples, (Formula 7), (Formula 12), and (Formula 7)
And the known lubricant and the mixture of (Chem. 7) and the rust preventive agent were described, but (Chem. 13), (Chem. 18), (Chem. 19), (Chem. 20),
Similar effects can be obtained with the substances of the formulas (21) and (23), and mixtures of these substances with conventionally known lubricants and rust preventives.

In the examples, phosphite was described as a rust preventive, but hydrogen phosphite, trithiophosphite, phosphate, thiophosphate,
Similar effects can be obtained with dithiophosphate, trithiophosphate, tetrathiophosphate, phosphonate, and phosphoric amide.

[0073]

As described above, the magnetic recording medium of the present invention has a ferromagnetic metal thin film provided on a non-magnetic support,
A lubricant layer containing at least one fluorine-containing alkyl carboxylic acid monoester of the present invention is provided on the ferromagnetic metal thin film via a protective film.

The fluorinated alkyl carboxylic acid monoester has a fluoroalkyl terminal group having one fluoroalkylene oxide chain in one molecule and one aliphatic hydrocarbon terminal group, that is, an aliphatic alkyl terminal group or aliphatic group. The structure has an alkenyl terminal group and a carboxyl group.

The fluoroalkyl terminal group is exposed on the surface of the metal thin film, the surface of the protective film, or the surface of the magnetic head, and contributes to lowering the energy of the surface to form a non-adhesive surface. Further, the fluoroalkylene oxide chain in the fluorinated alkyl carboxylic acid monoester molecule has a function of softening a rigid fluorinated hydrocarbon terminal chain due to the presence of the ether bonding group, and thus exhibits good lubricity. Provides both tackiness and lubricity.

Further, the aliphatic hydrocarbon terminal group has a good lubricating property because it is a flexible carbon-carbon bond chain. Also,
The carboxyl group strongly adheres to the surface of the magnetic head on the surface of the metal thin film or the surface of the protective film. Due to the synergistic effect of each of these terminal groups, the magnetic recording medium provided with a lubricant layer containing at least one kind of the fluorinated alkyl carboxylic acid monoester of the present invention has lubricity from a low humidity environment to a high humidity environment. An excellent effect of not decreasing is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing the results of infrared spectroscopic analysis of the fluorinated alkyl carboxylic acid monoester shown in Example 1.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Mikio Murai 1006 Kadoma Kadoma, Kazuma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Inside

Claims (4)

[Claims] 1. A fluorine-containing alkyl carboxylic acid monoester represented by the general formula (1). Embedded image Here, R ₁ represents an aliphatic alkyl group or an aliphatic alkenyl group, R ₂ represents a fluoroalkyl group, R ₃ represents —O— or —S—, and R ₄ represents —S— or —SC ₂ H. Represents ₄ S-, m is an integer of 1 to 6, n is an integer of 1 to 30, a is 0 or 1, and b is 0 or 1. 2. The fluorinated alkyl according to claim 1, wherein a fluoroalkyl alcohol having a fluoroalkylene oxide group or a fluoroalkyl thiol having a fluoroalkylene oxide group represented by the following general formula is used as a starting material. Carboxylic acid monoester. Embedded image Here, R ₂ represents a fluoroalkyl group, and R ₃ represents —O— or
Represents -S-, m is an integer of 1 to 6, and n is 1 to 30
Is an integer. 3. A ferromagnetic metal film is provided on a nonmagnetic support, and one or more of the fluorine-containing alkylcarboxylic acid monoesters according to claim 1 are contained on the ferromagnetic metal film via a protective film. A magnetic recording medium provided with a lubricant layer. 4. The magnetic recording medium according to claim 3, wherein the protective film is made of diamond-like carbon.