JPH10204032A - Fluorinated dialkyl carboxylic acid monoester and magnetic recording medium having the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a substance whose lubricity does not decrease from a low humidity environment to a high humidity environment. In A fluorinated dialkyl carboxylic acid monoester represented by the following chemical formula, 1705 cm carboxylic ^acid-1
Absorption peak. Here, R ₁ and R ₁ ｀ represent an aliphatic alkyl group or an aliphatic alkenyl group, R ₂ represents a fluoroalkyl group, and R ₃ represents
Represents —O— or —S—, and R ₄ represents —S— or —SC ₂ H ₄ S—
Wherein 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.

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 their sliding parts has also shifted from fluid lubrication to boundary lubrication. In particular, in electronic devices and devices such as VTRs and magnetic disks, the use of a ferromagnetic metal thin film for the purpose of improving the recording density has led to
High-precision lubrication has been required for sliding between a magnetic recording medium such as a magnetic tape or a magnetic disk and a magnetic head. 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 No. 62-46431) or a chemical formula (4) is used. There is a fluoroalkylcarboxylic 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.

[0007] The present invention solves the above-mentioned conventional problems, and has excellent running properties, durability and weather resistance and a stable friction coefficient even in a wide temperature environment.
It is an object of the present invention to provide a magnetic recording medium that can be put to practical use and maintain reliability. It also aims to improve the still life under various environments. According to the present invention, it is possible to develop a metal thin film type magnetic recording medium for broadcasting or a data streamer.

[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 a fluorine-containing dialkyl carboxylic acid monoester containing two alkyl groups of the present invention and having an increased molecular weight.

Although the molecular structure of the lubricant is complicated by adding two alkyl groups, as a result, crystals of the lubricant are hardly formed and the friction coefficient is significantly reduced. For this reason, the surface properties of the magnetic recording medium can be further improved than the current state, and the output of the magnetic recording medium can be improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The fluorine-containing dialkyl carboxylic acid monoester used in the present invention includes a fluoroalkyl terminal group represented by the general formula (Chemical Formula 5) and having one fluoroalkylene oxide chain in the same molecule; The structure has two aliphatic hydrocarbon terminal groups, that is, an aliphatic dialkyl terminal group or an aliphatic dialkenyl terminal group, and a carboxyl group.

[0011]

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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.

As R ₁ and R ₁ ′, a carbon number of 6 to 30, preferably 10 to 24 is suitable. If the carbon number is less than 6 or more than 30, the lubricity is reduced. R ₂ has 1 to 3 carbon atoms
0, preferably 1 to 8 fluoroalkyl groups, m is an integer of 1 to 6, n is an integer of 1 to 30, preferably 1 to 8, and m and n are out of these ranges. If it is, lubricity and storage reliability decrease. R ₃ is -O
-Or -S-, and R ₄ is -S- or -SC ₂ H ₄
S-, a is 0 or 1, and b is 0 or 1.

The fluorinated dialkyl carboxylic acid monoester is prepared by using a fluoroalkyl alcohol with a fluoroalkylene oxide group or a fluoroalkyl thiol with a fluoroalkylene oxide group as a starting material.
Wherein 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 Is suitably 1 to 8, and R ₃ is —O— or —S—.

[0015]

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[0016] 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 dialkyl carboxylic acid monoester or a fluorinated dialkyl carboxylic acid monoester represented by the general formula (5) and other lubricants, rust preventives, extreme pressure agents and the like. On the protective film. The mixing ratio is 40 mol% or more based on the total amount of the mixture,
Preferably, the content is 60 mol% or more, and if the content of the fluorinated dialkylcarboxylic acid monoester is less than 40 mol%, the effects of the present invention are hardly obtained. Its abundance surface 1 m ² per 0.05 to 100 mg, preferably suitable range of 0.1 to 50 mg. 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 the content of the fluorinated dialkyl carboxylic acid monoester 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 diamond state, a mixed state thereof, or a laminated state obtained by a method such as sputtering or plasma CVD can be applied, and these are all collectively referred to as amorphous carbon. The thickness is preferably 50 to 500 mm.

The method for producing the fluorinated dialkyl carboxylic acid monoester used in the present invention includes a dialkyl succinic anhydride, a dialkenyl succinic anhydride, a dialkylthio succinic anhydride or a dialkenylthio succinic anhydride and a fluoroalkylene oxide-containing fluoroalkyl group. An alcohol or a fluoroalkyl thiol having a fluoroalkylene oxide group is mixed and heated with stirring. The heating temperature is 60 to 100 ° C, preferably 80 to 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 dialkyl succinic anhydride or dialkenyl succinic anhydride or dialkylthio succinic anhydride or dialkenylthio succinic anhydride that can be used includes:
Didodecyl succinic anhydride, ditridecyl succinic anhydride,
Ditetradecyl succinic anhydride, dipentadecyl succinic anhydride, dihexadecyl succinic anhydride, diheptadecyl succinic anhydride, dioctadecyl succinic anhydride, dinonadecyl succinic anhydride, diicosyl anhydride succinic anhydride, dihenicosyl anhydride succinic anhydride, didocosyl succinic anhydride, didosenic anhydride , Ditridecenyl succinic anhydride, ditetradecenyl succinic anhydride, dipentadecenyl succinic anhydride, dihexadecenyl succinic anhydride, diheptadecenyl succinic anhydride, dioctadecenyl succinic anhydride, dinonadecenyl succinic anhydride, diicosenyl succinic anhydride,
Dihenicocenyl succinic anhydride, didococenyl succinic anhydride, didodecylthiosuccinic anhydride, ditridecylthiosuccinic anhydride, ditetradecylthiosuccinic anhydride, dipentadecylthiosuccinic anhydride, dihexadecylthiosuccinic anhydride, diheptadecylthiosuccinic anhydride Acid, dioctadecylthio succinic anhydride, dinonadecyl succinic anhydride,
Diicosylthio succinic anhydride, diphenicosylthio succinic anhydride, didocosylthio succinic anhydride, didodecenylthio succinic anhydride, ditridecenylthio succinic anhydride,
Ditetradecenyl succinic anhydride, dipentadecenylthio succinic anhydride, dihexadecenylthio succinic anhydride, diheptadecenylthio succinic anhydride, dioctadecenylthio succinic anhydride, dinonadecenylthio succinic anhydride, diicosenylthio There are succinic anhydride, dihenicosenylthio succinic anhydride, and didocosenylthio succinic anhydride. Further, other than succinic anhydride, dialkyl glutaric anhydride and dialkenyl glutaric anhydride containing a dialkyl group as exemplified above may be used.

The fluoroalkylene oxide-containing fluoroalkyl alcohol or fluoroalkylene oxide-containing fluoroalkyl thiol 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.

For example, the reaction of an alkyl succinic anhydride or alkenyl succinic anhydride or an alkylthio succinic anhydride or an alkenylthio succinic anhydride with a fluoroalkyl alcohol having a fluoroalkylene oxide group or a fluoroalkyl thiol having a fluoroalkylene oxide group is carried out in the presence of a solvent. Conveniently proceed with heating and stirring below. The solvent includes normal octane and normal heptane.

The molar ratio of the dialkyl succinic anhydride or dialkenyl succinic anhydride, dialkylthio succinic anhydride or dialkenylthio succinic anhydride to the fluoroalkyl alcohol having a fluoroalkylene oxide group or the fluoroalkyl thiol having a fluoroalkylene oxide group is as follows. Is a mole.

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 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—, 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 dihexadecyl succinic anhydride (0.10 mol) represented by the formula (8) and a fluoroalkyl alcohol having a fluoroalkylene oxide group represented by the formula (9) (0.1 mol).
0 mol).

[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 dihexadecyl 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 represented by the following chemical formula (7) free from starting materials and by-products by infrared spectroscopy (IR), gel permeation chromatography (GPC) and organic mass spectrometry (FD-MS). Turned out to be a substance. The results of infrared spectroscopy (spectrum) of this compound are shown in FIG. 1, where the horizontal axis represents wavelength (cm- ¹ ) and the vertical axis represents transmittance (%).

IR: Absorption peak at 1,775 cm- ¹ of acid anhydride, absorption peak of alcohol at 3,330 cm- ¹ disappeared, absorption peak of carboxylic acid at 1,705 cm- ¹ and ester at 1,760 cm- ¹ appeared. 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 and R ₁ ′ are hexadecyl groups having 16 carbon atoms, R ₂ is a fluoroalkyl group having 5 carbon atoms, m is 3, n is 2, and a
Is 1 and b is 0.
In the case where the structure is different from that described above, the starting material is replaced with, for example,
2) or (Formula 13) can be produced.

Further, dihexadecyl succinic anhydride was used as the aliphatic dialkyl succinic anhydride, but a corresponding reactant was obtained when the starting materials were changed. For example, as aliphatic dialkenylthio succinic anhydride (Chemical Formula 14) and (Chemical Formula 15)
Can be used to produce compounds (Chemical Formula 16) and (Chemical Formula 17).

[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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(Embodiment 2) Next, embodiments of a magnetic recording medium characterized by using the lubricant of the present invention will be specifically described. However, the present invention is not limited to these embodiments. Absent.

The non-magnetic support of the magnetic recording medium of the present embodiment has, on the surface of a polyester film, steep mountain-like projections having silica particles having a diameter of 150 mm as nuclei and an ultraviolet-curable epoxy resin as a binder per 1 mm ^2. One formed so as to have 1 × 10 ⁷ pieces was used. Then, a Co ferromagnetic thin film (thickness: 1000) is formed on the non-magnetic support by a continuous vacuum oblique deposition method.
Ii) was provided in the presence of trace amounts of oxygen. The oxygen content in the ferromagnetic film was 5% in atomic fraction.

Next, a voltage of 500 V is applied to the electrode by a DC plasma CVD method using methane as a raw material to form a 100-mm-thick diamond-like carbon protective film on the ferromagnetic film. After applying a fluorine-containing dialkyl carboxylic acid monoester represented by the formula (Formula 7) on the protective film in an amount of 10 mg per 1 m ² to form a lubricant layer, a 1/4 inch predetermined The tape was cut to a width to produce a magnetic tape. The Vickers hardness of the diamond-like carbon used was 2000.

The magnetic tape completed in this way is
℃, 10% RH and 40 ° C, 80% RH, commercially available DVC
Measure the running durability and output characteristics during still playback on a VCR, and measure the number of times the magnetic tape has run until the RF output drops by 3 dB from the initial value and the time until the output drops by 3 dB in the still life measurement. Was examined.

(Example 3) A magnetic tape was prepared from the magnetic tape of Example 2 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, instead of (Chemical Formula 7), (Chemical Formula 7) and a rust preventive (C ₁₂ H ₂₅ S) ₃ P =
A similar test was conducted by preparing a magnetic tape using a mixture of O at a weight ratio of 2: 1.

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

[0053]

[Table 1]

[0054]

[Table 2]

From Tables 1 and 2, all the magnetic tape samples provided with the lubricant layer containing the fluorinated dialkyl carboxylic acid monoester of the present invention have excellent lubricity at low humidity and high humidity. It is clear that On the other hand, it is apparent that the lubricating property of a magnetic tape provided with a conventional lubricant layer comprising only a lubricant is reduced in low humidity or high humidity.

In the examples, (Chem. 7), (Chem. 12) and (Chem. 7)
And the conventionally known lubricant and the mixture of (Chem. 7) and the rust preventive are described. The substances of (Chem. 13), (Chem. 16) and (Chem. 17), these substances and the conventionally known lubricant, The same effect can be obtained with a mixture with a rust inhibitor.

In the embodiment, trithiophosphate has been described as a rust preventive. However, hydrogen phosphite, phosphite, trithiophosphite, phosphate, thiophosphate, dithiophosphate, tetrathiophosphate, phosphonate, and phosphoric amide are described. Has the same effect.

(Embodiment 6) Next, an embodiment of the lubricant of the present invention for another magnetic recording medium will be specifically described.

The non-magnetic support of the magnetic recording medium of the sixth 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 dialkyl carboxylic acid monoester represented by the formula (Formula 7) was applied in an amount of 10 mg per 1 m ² , and a lubricant layer was provided to produce a magnetic disk.

The magnetic disk was set at 5 ° C., 10% RH and 40%.
Under the environment of ℃, 80% RH, CSS (contact start
Stop) test was performed, and the 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 in Embodiment 4 instead of (Formula 7), and the same test was performed.

(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.

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

[0065]

[Table 3]

As shown in Table 3, all the magnetic disks provided with a lubricant layer containing at least one kind of the fluorinated dialkylcarboxylic acid monoester of the present invention have excellent CSS durability in low humidity and high humidity. It is clear that On the other hand, it is clear 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 conventionally known lubricant and the mixture of (Chem. 7) and the rust preventive are described. The substances of (Chem. 13), (Chem. 16) and (Chem. 17), these substances and the conventionally known lubricant, The same effect can be obtained with a mixture with a rust inhibitor.

In the examples, trithiophosphate was described as a rust preventive. However, hydrogenated phosphite, phosphite, trithiophosphite, phosphate, thiophosphate, dithiophosphate, tetrathiophosphate, phosphonate, and phosphoric amide were also used. Similar effects can be obtained.

[0069]

As described above, in the magnetic recording medium of the present invention, a ferromagnetic metal thin film is provided on a nonmagnetic support, and a carbon-based protective film is provided on the ferromagnetic metal thin film.
It is provided with a lubricant layer containing at least one kind of the fluorine-containing dialkylcarboxylic acid monoester of the present invention.

The fluorinated dialkyl carboxylic acid monoester has a fluoroalkyl terminal group having one fluoroalkylene oxide chain in the same molecule and two aliphatic hydrocarbon terminal groups, that is, an aliphatic dialkyl terminal group or an aliphatic terminal. The structure has a dialkenyl 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, thereby contributing to lowering the energy of the surface and forming 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 two aliphatic hydrocarbon terminal groups exhibit a good lubricating property due to a flexible carbon-carbon bond chain.
The presence of the two hydrocarbon groups reduced the coefficient of friction of the metal thin-film magnetic tape, drastically improved the output stability, and also significantly improved the still life in various environments.

As a result, the metal thin film type magnetic tape can be used for broadcasting and data streamers. 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 these terminal groups, the magnetic recording medium provided with a lubricant layer containing at least one kind of the fluorinated dialkyl carboxylic acid monoester of the present invention can be used in a low humidity environment to a high humidity environment. An excellent effect that the lubricity does not lower than that of the lubricant can be obtained.

[Brief description of the drawings]

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

Continued on the front page (72) Inventor Kenji Kuwahara 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A fluorine-containing dialkylcarboxylic acid monoester represented by the general formula (1). Embedded image Here, R ₁ and R ₁ ′ represent an aliphatic alkyl group or an aliphatic alkenyl group, R ₂ represents a fluoroalkyl group, and R ₃ represents
Represents —O— or —S—, and R ₄ represents —S— or —SC ₂ H ₄ S—
Wherein 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. A method of reacting with a dialkyl succinic anhydride or a dialkyl glutaric anhydride starting from a fluoroalkyl alcohol having a fluoroalkylene oxide group or a fluoroalkyl thiol having a fluoroalkylene oxide group represented by the following general formula: The fluorinated dialkyl carboxylic acid monoester according to claim 1, characterized in that: 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 thin film is provided on a nonmagnetic support, and a protective film is interposed on the ferromagnetic metal thin film.
The fluorinated dialkylcarboxylic acid monoester described in 1
A magnetic recording medium provided with a lubricant layer containing more than one kind. 4. The magnetic recording medium according to claim 3, wherein the protective film is made of amorphous carbon.