JP3216316B2 - Fluorine-containing carboxylic acid and magnetic recording medium having the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a novel fluorine-containing carboxylic acid useful as a lubricant, a surfactant, a release agent, a rust inhibitor and the like for precision machines and precision parts requiring 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 the recording density enables high-precision lubrication of the sliding between the magnetic tape or magnetic disk and the magnetic head. Is needed.

For example, in the case of a vapor-deposited tape or a hard disk, a lubricant layer on the surface of a magnetic layer is required to minimize the spacing loss between a magnetic recording medium and a magnetic head and to achieve high output while securing durability and reliability. Is formed to have a thickness of only several tens of degrees. Therefore, development of an organic compound having excellent lubricity as a material for forming the lubricant layer is an important issue.

[0004] As a lubricant for a metal thin film type magnetic recording medium, for example, a fluoroalkyl group-containing aliphatic carboxylic acid represented by the following formulas (2) and (3) has excellent compatibility with a metal thin film. A proposal has been made (JP-A-61-1075).
29, JP-A-2-108218).

[0005]

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[0006]

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[0007]

However, the lubricant of the aliphatic carboxylic acid having a fluoroalkyl group represented by the above-mentioned (Chemical Formula 2) or (Chemical Formula 3) has a problem that when stored in an environment of high temperature and high humidity, the lubricant crystal becomes There is a problem that the lubricating property deteriorates due to precipitation.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a substance which does not lose lubricity even after storage in an environment of high temperature and high humidity.

[0009]

The substance of the present invention for attaining the above object is a fluorine-containing carboxylic acid represented by the general formula (Formula 4).

[0010]

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As R ₁ , those having 6 to 30 carbon atoms, preferably 10 to 24 carbon atoms, are suitable.
When it exceeds, the lubricity decreases. R ₂ has 1 carbon atom
-30, preferably 4-18, and having 0 carbon atoms
Or, when it exceeds 30, lubricity decreases. m is 1-2
0, preferably 2 to 10, is suitable, and when m exceeds 20, lubricity decreases.

In the magnetic recording medium of the present invention, a ferromagnetic film is provided on a non-magnetic support, and the fluorine-containing carboxylic acid represented by the general formula (4) is directly or via a protective film on the ferromagnetic film. It is provided with a lubricant layer containing one or more acids.

This lubricant layer is made of a fluorinated carboxylic acid represented by the general formula (4) alone or in the form of a thin layer by adding another lubricant, a rust inhibitor and the like. Its abundance is 0.05 to 100 mg, preferably 0.1 to 50 mg / m ^{2 on the} surface.
The mg range is suitable. Further, as the other lubricant and rust preventive, a fluorine-containing compound is preferable, and a liquid fluorine-containing compound is more preferable. The added amount is 0 to 80
%, Preferably in the range of 0 to 70%, and when the content of the fluorinated carboxylic acid represented by the general formula (Chemical Formula 4) is less than 20%, 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.
0-500 ° is preferred.

[0015]

It is conventionally known that the fluorine-containing carboxylic acid of the present invention has a fluorocarbon terminal group, that is, a fluorine-containing hydrocarbon terminal group having an aliphatic omega (ω) alkenyl bonded immediately after a fluoroalkyl terminal group or a fluoroalkenyl terminal group. Is different from the lubricant.

That is, the fluorine-containing hydrocarbon terminal group is bent into a cis or trans structure at a portion where the fluorocarbon terminal group and the aliphatic omega (ω) alkenyl bond. Therefore, the fluorocarbon terminal group is hardly close to the fluorocarbon terminal group of another adjacent molecule, and an appropriate intermolecular interaction does not work. Therefore, the molecules of the fluorinated carboxylic acid cannot be aligned with each other, and the crystallization phenomenon in which the molecules are aligned does not occur.

Incidentally, 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. In addition, the fluorocarbon end groups are exposed on the surface and contribute to lowering the energy of the surface, forming a non-adhesive surface.
In addition, aliphatic hydrocarbon end groups, i.e., aliphatic alkyl or alkenyl end groups, are flexible carbon-
It exhibits good lubricity because it is a carbon-bonded chain. And
Due to the synergistic effect of these terminal groups, excellent lubricity is exhibited in all environments from a low humidity environment to a high humidity environment.

[0018]

【Example】

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be specifically described.

The substance of this embodiment is represented by the following formula (5).

[0020]

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[0021] (Formula 5) of the while explaining comparative substance with the general formula (Formula 4), C ₁₈ aliphatic alkyl group R ₁
H ₃₇ has a (octadecyl) has a fluoroalkyl group having six carbon bonded to fluorine as R _2, m is 2
And n is 0.

Next, a method for producing the substance represented by the formula (5) will be described. The starting materials are 35.3 g (0.10 mol) of octadecylsuccinic anhydride represented by (Chem. 6) and (Chem. 7)
39.0 g of a fluoroalkyl group-containing alcohol represented by
(0.10 mol).

[0023]

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[0024]

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The above raw materials, 170 ml of normal heptane and 130 ml of toluene were collected in a 1-lit. Flask equipped with stirring blades and reacted under reflux for 24 hours. After the reaction,
Normal heptane and toluene were distilled off from the reaction solution, and the reaction product was made into a normal hexane solution, and then cooled to 0 ° C. to remove unreacted octadecyl succinic anhydride.

Further, the reaction product was converted into a methanol solution and cooled to -10 ° C to remove unreacted fluoroalkyl group-containing alcohol to obtain 53g of a white solid having a melting point of 43 ° C. The white solid was analyzed by infrared spectroscopy (IR), gel permeation chromatography (GPC) and organic mass spectroscopy (FD-MS) to obtain a fluorine-containing compound represented by the formula (Chemical Formula 5) containing no starting materials and by-products. It was found to be a carboxylic acid.

IR; absorption peak of acid anhydride at 1,775 cm ^-1 and disappearance of absorption peak of alcohol at 3,330 cm ^-1 , absorption peak of ester at 1,735 cm ^-1 and absorption peak of carboxylic acid at 1705 cm ^-1 Appearance.

GPC: Starting material and by-product not detected. FD-MS; main peak at m / e 743.

In this example, a mixed solvent of normal heptane and toluene was used as a reaction solvent.
With a hydrophobic solvent that can be set to ~ 120 ° C, alcohols,
Any material other than the ester type may be used. This is the same in other embodiments.

(Embodiment 2) Next, a second embodiment of the present invention will be specifically described.

The substance of this embodiment is represented by the following formula (8).

[0032]

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[0033] When the (Formula 8) will be described in comparison with the general formula of the material (of 4), C as aliphatic alkenyl group R _{1
It has 15} H ₃₁ CH ＝ CHCH ₂ (2-octadecenyl), R ₂ has a fluoroalkenyl group having 6 fluorine-bonded carbons, m is 9 and n is 1.

Next, a method for producing the substance represented by Chemical Formula 8 will be described. Starting materials are 35.1 g (0.10 mol) of 2-octadecenyl succinic anhydride represented by (Chemical Formula 9) and 45.0 g (0.10 mol) of alcohol having a fluoroalkenyl group represented by (Chemical Formula 10).

[0035]

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[0036]

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The above raw materials and 300 ml of benzene were collected in a 1-lit. Flask equipped with a stirring blade, and reacted under reflux for 24 hours. After completion of the reaction, unreacted starting materials were removed by the same treatment as in (Example 1).
g was obtained. This colorless transparent liquid has IR, GPC and F
By D-MS, it was found to be a fluorinated carboxylic acid represented by the formula (Formula 8) which does not contain a starting material and a by-product.

IR; absorption peak of acid anhydride at 1,775 cm ^-1 and absorption peak of alcohol at 3,330 cm ^-1 , absorption peak of ester at 1,735 cm ^-1 and absorption peak of carboxylic acid at 1705 cm ^-1 Appearance.

GPC: Starting material and by-product not detected. FD-MS; main peak at m / e 801.

(Embodiment 3) Next, an embodiment of the magnetic recording medium of the present invention will be specifically described.

In the non-magnetic support of the magnetic recording medium of this embodiment, there are several granular projections (average height 70 °, diameter 1 μm) with a gentle gradient due to silica fine particles added to the polyester film per 100 μm ² surface. In addition, on the surface of the polyester film, where relatively large protrusions due to fine particles due to the polymerization catalyst residue are reduced as much as possible, steep mountain-like protrusions using silica colloid particles having a diameter of 150 mm as nuclei and an ultraviolet-curable epoxy resin as a binder. Formed so as to be 1 × 10 ⁷ per 1 mm ² .

Then, a Co—Ni ferromagnetic film (Ni content: 2) was formed on the nonmagnetic support by a continuous vacuum oblique deposition method.
0%, thickness 1000 °) in the presence of a trace amount of oxygen. The oxygen content in the ferromagnetic film was 5% in atomic fraction.

Next, on the above-mentioned ferromagnetic film, a fluorine-containing carboxylic acid represented by the formula (Formula 5) was applied in an amount of 10 mg per 1 m ² to form a lubricant layer. Then, it was cut to a predetermined width to produce a magnetic tape. After the magnetic tape was stored in an environment of 40 ° C. and 90% RH for one week, the presence or absence of crystals was examined by an optical microscope. Also, at 23 ° C,
Under the environment of 10% RH, 40 ° C. and 80% RH, the output characteristics during repeated running on a commercially available VCR were measured,
The number of runnings until the RF output decreased by 3 dB from the initial value or the output fluctuation started to occur was determined.

(Example 4) A magnetic tape was prepared from the magnetic tape of (Example 3) using (Formula 8) instead of (Formula 5), and the same test was performed.

(Example 5) In the magnetic tape of (Example 3), instead of (Chemical Formula 5), (Chemical Formula 5) and a conventionally known rust preventive agent C ₈ F ₁₇ C ₂ H ₄ NHC ₁₈ H ₃₅ were used in weight. A similar test was conducted by making a magnetic tape using a 2: 1 mixture.

(Example 6) In the magnetic tape of (Example 3), instead of (Chemical Formula 5), (Chemical Formula 5) and a conventionally known lubricant C ₁₇ H ₃₃ COOC ₂ H ₄ C ₆ F ₁₃ were used in a weight ratio. A magnetic tape using a 1: 1 mixture was prepared for the same test.

Table 1 shows the test results of the above examples. The lubricants of Conventional Examples 1, 2 and 3 in the table are represented by (Chem. 3), (Chem. 11) and (Chem. 12), respectively.

[0048]

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[0049]

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[0050]

[Table 1]

From Table 1, it can be seen that all magnetic tapes provided with a lubricant layer containing one or more fluorine-containing carboxylic acids of the present invention have excellent lubricity even after storage in a high temperature and high humidity environment. It is clear that. On the other hand, it is clear that when a magnetic tape provided with a conventional lubricant layer comprising only a lubricant is stored in a high-temperature, high-humidity environment, crystals of the lubricant are precipitated and lubricity is reduced.

(Embodiment 7) Next, another embodiment of the magnetic recording medium of the present invention will be specifically described.

The non-magnetic support of the magnetic recording medium of the present embodiment is prepared by plating a surface of an Al alloy plate having a diameter of 95 mm and a thickness of 1.2 mm with a non-magnetic Ni-P alloy having a thickness of 25 μm and averaging it by texturing. A projection having a roughness of 50 ° and a maximum height of 300 ° was used. 1300mm thick Cr by sputtering on non-magnetic Ni-P alloy plating
Forming a base and a ferromagnetic film of Co-Ni with a thickness of 600 °;
Further, a sample A in which a 200-mm-thick graphite protective film was formed on the ferromagnetic film by a sputtering method.

A sample B in which a diamond-like carbon protective film having a thickness of 50 ° was formed by plasma CVD instead of the graphite protective film was used. Next, on the protective film of these samples, a fluorine-containing carboxylic acid of the formula (5) was applied in an amount of 10 mg per 1 m ² to provide a lubricant layer, thereby producing a magnetic disk.

After storing the magnetic disk in an environment of 40 ° C. and 90% RH for one week, the presence or absence of crystals was examined by an optical microscope. Further, at 23 ° C., 10% RH and 40 ° C., 8
A CSS (contact start / stop) durability test was performed in an environment of 0% RH, and the number of CSSs when the friction coefficient exceeded 1.0 or the CS when a head crash occurred
The durability was determined by the number of S times.

(Embodiment 8) A magnetic disk was prepared from the magnetic disk of (Example 7) using (Formula 8) instead of (Formula 5), and the same test was performed.

(Example 9) A magnetic disk was prepared from the magnetic disk of (Example 7) using the same lubricant as in (Example 5) instead of (Formula 5), and a similar test was performed.

(Example 10) A magnetic disk was prepared from the magnetic disk of (Example 7) using the same lubricant as in (Example 6) in place of (Formula 5), and a similar test was performed.

Table 2 shows the test results of the above examples. The lubricants of Conventional Examples 4, 5 and 6 in the table are represented by (Chem. 3), (Chem. 11) and (Chem. 12), respectively.

[0060]

[Table 2]

From Table 2, it can be seen that all the magnetic disks provided with a lubricant layer containing one or more fluorine-containing carboxylic acids of the present invention have excellent lubricity even after storage in a high-temperature and high-humidity environment. It is clear that. On the other hand, it is clear that when a conventional magnetic disk provided with a lubricant layer comprising only a lubricant is stored in an environment of high temperature and high humidity, lubricant crystals are precipitated and lubricity is reduced.

In the examples, the mixtures of the substances of the formulas (5), (8) and (5) with conventionally known lubricants and rust inhibitors have been described. ), (Chemical Formula 15), (Chemical Formula 16) and (Chemical Formula 17), and the same effects can be obtained with mixtures of these materials with conventionally known lubricants and rust inhibitors.

[0063]

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[0064]

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[0065]

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[0066]

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[0067]

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[0068]

As is clear from the above description, the fluorinated carboxylic acid of the present invention can be obtained by adding an aliphatic omega (ω) alkenyl group immediately after a fluorocarbon terminal group, that is, a fluoroalkyl terminal group or a fluoroalkenyl terminal group, in the same molecule. Has a fluorinated hydrocarbon terminal group and an aliphatic hydrocarbon terminal group, that is, an aliphatic alkyl terminal group or an aliphatic alkenyl terminal group, and a carboxyl group bonded to each other after storage in an environment of high temperature and high humidity. Also shows an excellent effect that the lubricity does not decrease.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI C10N 40:18 C10N 40:18 (56) References JP-A-6-293703 (JP, A) JP-A-6-41561 (JP) (A) JP-A-61-107529 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/71 CA (STN) REGISTRY (STN) WPIDS (STN)

Claims (2)

(57) [Claims] 1. A fluorine-containing carboxylic acid represented by the general formula (1). Embedded image 2. A ferromagnetic film is provided on a nonmagnetic support, and one or more fluorine-containing carboxylic acids represented by the general formula (1) are directly or through a protective film on the ferromagnetic film. A magnetic recording medium provided with a contained lubricant layer.