JPH09104885A - Magnetic medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a magnetic medium having a low friction coefficient and a low fluctuation of output (voltage) and excellent in durability in still picture playing and long time recording and playing by forming at least a magnetic layer on a non-magnetic base and allowing the magnetic layer to contain a specific lubricating agent. SOLUTION: This magnetic medium has at least a magnetic layer on a non- magnetic base and a lubricating agent which is a compound of the formula [R1 is a 1-30C (branched) alkyl; R2 is a 1-30C (branched) alkylene; Rf1 is a 1-30C (branched) fluoroalkylene; Rf2 is a 1-30C (branched) fluoroalkyl; X is H or F] in an amount of 0.05-100mg/m<2> applied directly on the magnetic layer or via a protective layer coated on the magnetic layer, on the surface of the magnetic medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having a low friction coefficient value and improved durability.

[0002]

2. Description of the Related Art Increasing the recording density in a magnetic recording medium is achieved by improving the magnetic characteristics, thinning the magnetic layer, or enhancing the smoothness of the surface of the magnetic layer. To be done. However, thinning the magnetic layer or improving the smoothness of the surface causes problems such as wear of the magnetic layer due to contact with the head during sliding, and an increase in friction coefficient during running. Specifically, the following two points are highlighted as major problems.

(1) The wear of the magnetic layer when the VTR is operated in the pause state is prevented, and the deterioration of the output is suppressed. (Still durability) (2) It suppresses an increase in the coefficient of friction when the recording / reproducing reciprocating motion is repeated.

Therefore, in order to solve these problems, the use of various lubricants such as higher fatty acids and their esters has been proposed. In this case, the coating amount of the lubricant is limited to almost a monomolecular level, and in particular, since the metal thin film magnetic recording medium cannot be supplemented with the lubricant,
The lubricant is required to be thermally and chemically stable on the magnetic layer. However, commercially available lubricants cannot fully satisfy their lubricating properties, and it is pointed out that the development of new lubricants or lubricant compositions is important.

As such a novel lubricant, a fluorine-based lubricant has been actively used in recent years. For example, as commercially available fluorine-based lubricants, Demnum SA manufactured by Daikin Industries or Fomblin Z manufactured by Aojimont Co., which has the following chemical structure, is used.
DOL and the like are known.

[0006]

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Although these fluorine-based lubricants have good durability, they cannot suppress the increase in the friction coefficient when the recording / reproducing reciprocating motion is repeated.
Therefore, JP-A-4-178357 and JP-A-4-178357
In Japanese Patent No. 271013, it is proposed to improve the slipperiness and durability of a magnetic recording medium by using a fluorine-containing compound having both an alkyl group and a fluoroalkyl group. However, with the increasing recording density of magnetic recording media, it is the current situation that satisfactory lubricity and durability have never been obtained even with such lubricants.

Therefore, an object of the present invention is to provide a magnetic recording medium which has a low friction coefficient value and whose output does not fluctuate even after recording and reproducing for a long time.

[0009]

In order to achieve the above object,
As a result of intensive studies by the present inventors, the inventors have found that the use of a specific fluorine-containing carboxylic acid ester-based lubricant can reduce the friction coefficient value and obtain a magnetic recording medium without output fluctuation.

The present invention has been made on the basis of the above findings, and has at least a magnetic layer on a non-magnetic support and contains a fluorine-containing carboxylic acid ester represented by the following formula (1). The above object is achieved by providing a magnetic recording medium characterized by the above.

[0011]

Embedded image (In the formula, R ₁ represents a linear or branched alkyl group having 1 to 30 carbon atoms, R ₂ represents a linear or branched alkylene group having 1 to 30 carbon atoms, and R _f1 represents Represents a linear or branched fluoroalkylene group having 1 to 30 carbon atoms, R
_f2 represents a linear or branched fluoroalkyl group having 1 to 30 carbon atoms, and X represents H or F. )

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic recording medium of the present invention will be described below in detail. The fluorinated carboxylic acid ester represented by the above formula (1) used in the magnetic recording medium of the present invention will be described. The fluorinated carboxylic acid ester is used as a lubricant in the magnetic recording medium. In the above formula (1), R ₁ is an alkyl group having 1 to 30 carbon atoms. The alkyl group may be linear or branched. The number of carbon atoms in the alkyl group is preferably 1-20, more preferably 1-15.
Particularly preferred examples of the alkyl group are CH ₃ , C ₂
H _5, C ₃ H _7, can be mentioned C ₅ H ₁₁ and C ₁₀ H ₂₁ and the like.

In the above formula (1), R ₂ has 1 carbon atom.
To 30 alkylene groups. In this case, the alkylene groups in R ₂ may be the same or different. Further, the alkylene group may be linear or branched. Further, the number of carbon atoms in the alkylene group is preferably 1 to
20 and more preferably 1 to 15. Particularly preferred examples of the alkylene group include C ₂ H ₄ and C
₅ H _10, C ₇ H ₁₄ and C ₁₅ H ₃₀ and the like.

In the above formula (1), R_f1Has 1 carbon
To 30 fluoroalkylene groups. The fluoroal
The xylene group may be linear or branched. Also,
The number of carbon atoms in the fluoroalkylene group is preferably 1-20
And more preferably 2 to 15. The fluoroa
A particularly preferred example of the alkylene group is C_TwoF_Four, C _Five
F_Ten, C₈F₁₆, (CF_Three)_TwoC (CF_Two)₆And C_FifteenF₃₀
Etc. can be mentioned.

In the above formula (1), R _f2 has 1 carbon atom.
To 30 fluoroalkyl groups. The fluoroalkyl group may be linear or branched. The number of carbon atoms in the fluoroalkyl group is preferably 1-20, more preferably 2-15. Particularly preferred examples of the fluoroalkyl group include C ₆ F ₁₃ , C ₇ F ₁₅ ,
_{(CF 3) 2 CF (CF} 2) can be given _6, C ₁₀ F ₂₁ and C ₁₅ F ₃₁ or the like.

In the above formula (1), X is H or F. The X may be H or F depending on the types of the substituents R ₁ , R ₂ , R _f1 and R _f2 .

Particularly preferred specific examples of the fluorine-containing carboxylic acid ester represented by the above formula (1) are 3,3.
2- (perfluorohexyl) ethyl 4,4-tetrafluoropentanoate, 2- (perfluorohexyl) ethyl 4,4,5,5-tetrafluorohexanoate,
4,4,5,5,6,6,7,7,8,8-5- (perfluoroheptyl) pentyl decafluorodecanoate,
3,3,4,4,5,5,6,6,7,7,8,8,
9,9,10,10,11,11-heptadecafluorotridecanoic acid-7- (perfluoroheptyl) heptyl, 4,4,5,5,6,6,7,7-octafluoroheptadecanoic acid- 7- (perfluorodecyl) heptyl, 4,4,5,5,6,6,7,7,8,8,9,9
-Dodecafluoro-9-trifluoromethyloctadecanoic acid-7- (perfluorodecyl) heptyl, 4,4
5,5,6,6,7,7,8,8,9,9,10,1
0,11,11,12,12,13,13,14,1
4,15,15,16,16-hexacosafluoroheneicosanoic acid-15- (perfluoroisononyl) pentadecyl and the like can be mentioned.

The molecular weight of the fluorinated carboxylic acid ester represented by the above formula (1) is not particularly limited, but the molecular weight in a general range is preferably about 500 to 5,000. When the molecular weight is less than 500, sufficient lubricity cannot be obtained, and when it exceeds 5,000, the effect of the terminal group may not be sufficiently exerted, so the above range is preferable.

The fluorine-containing carboxylic acid ester represented by the above formula (1) has an alkyl group (R ₁ ) and an alkylene group (R ₂ ) as well as a fluoroalkyl group (R _f2 ) and a fluoroalkylene group (in its molecule). R _f1 ) is contained. In this case, the alkyl group and the alkylene group contribute to the slip property (friction coefficient value of the magnetic recording medium) among the properties of the lubricant, while the fluoroalkyl group and the fluoroalkylene group contribute to the properties of the lubricant. It contributes to the durability (variation in output of the magnetic recording medium). And
In the present invention, by using the specific alkyl group and alkylene group and the fluoroalkyl group and fluoroalkylene group together with the carboxylic acid ester as the main skeleton of the lubricant, the lubricity and durability of the lubricant are improved. .

Next, the method for synthesizing the fluorine-containing carboxylic acid ester represented by the above formula (1) will be described. The fluorine-containing carboxylic acid ester represented by the above formula (1) can be obtained, for example, by the reaction formula It can be easily synthesized according to [I].

[0021]

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That is, the fluorine-containing carboxylic acid ester represented by the above formula (1) is obtained by adding an alkylfluoroalkyl iodide (a) and a fluoroalkylalkyl acrylate (b) in the presence of a small amount of iodine at 145 ° C. The resulting compound (c) was dissolved in ethanol saturated with hydrogen chloride gas, zinc powder was added, and the mixture was heated at 70 ° C.
It is obtained by further reacting with, further filtering the zinc powder, and then purifying. The carboxylic acid as the raw material for the acrylic acid fluoroalkylalkyl ester (b) is
N. O. Brace et al. [J. Org. Chem.
Vol. 27, P4491 (1962)].

The fluorine-containing carboxylic acid ester represented by the above formula (1) is preferably applied in the form of a thin film directly on the magnetic layer in the magnetic recording medium of the present invention, or provided on the magnetic layer. It is applied as a thin film through the protective layer and acts as a lubricant layer. That is, the fluorine-containing carboxylic acid ester represented by the above formula (1) exists as a lubricant layer provided on the magnetic layer (when a protective layer is provided on the magnetic layer, the protective layer is provided on the magnetic layer). Exists as a lubricant layer provided on top). The method for applying the above-mentioned fluorine-containing carboxylic acid ester is not particularly limited, and for example, a wet coating method using a sprayer equipped with an ultrasonic oscillator or a dry coating method such as vacuum deposition can be used.

The content (adhesion amount) of the above-mentioned fluorine-containing carboxylic acid ester in the magnetic recording medium of the present invention can be appropriately adjusted according to the form (tape, disk) of the magnetic recording medium, etc. The content (adhesion amount) as a specific range is 0.05 per 1 m ² of the surface of the magnetic recording medium.
It is preferably -100 mg, more preferably 1-50 mg. The content (adhesion amount) is 0.05
If it is less than mg / m ² , sufficient lubricity and durability may not be obtained, and the head and tape may be damaged.
If it exceeds g / m ² , sticking of the tape and clogging of the head may occur, so the above range is preferable.

In the present invention, the above-mentioned fluorine-containing carboxylic acid ester may be used alone or in combination with a lubricant usually used in magnetic recording media.
Further, if necessary, other additives such as phenols, quinones and naphthols, and heterocyclic compounds containing nitrogen atom, oxygen atom or sulfur atom may be used in combination. In these cases, the amount of the lubricant or additive is 1 to 30 with respect to 100 parts by weight of the fluorine-containing carboxylic acid ester.
It is preferable to add parts by weight.

As described above, the magnetic recording medium of the present invention comprises at least a magnetic layer on a non-magnetic support. Examples of the magnetic layer include a coating type magnetic layer formed by coating a magnetic coating material containing magnetic powder and a binder on the non-magnetic support, and a physical vapor layer such as sputtering, vacuum deposition or ion plating. Phase growth method (PVD
Method) can be used. Of these magnetic layers, it is particularly preferable to use a metal thin film type magnetic layer.

The metal thin film type magnetic layer will be described. Examples of the metal forming the magnetic layer include Fe and C.
In addition to metals such as o and Ni, Co-Ni alloys, Co-Pt
Alloy, Co-Ni-Pt alloy, Fe-Co alloy, Fe-
A Ni alloy, an Fe-Co-Ni alloy, an Fe-Co-B alloy, a Co-Ni-Fe-B alloy, a Co-Cr alloy, or those containing a metal such as Al is used. In addition, Fe-N, Fe-N-O, Fe-C, Fe
-CO is also used. It is preferable that an oxidizing gas be supplied at the time of forming the metal thin film to form a protective layer made of an oxide film on the surface of the metal thin film.

The magnetic layer may be composed of a single metal thin film, or may be composed of two or more metal thin films. When the magnetic layer is composed of two or more metal thin films, the material of each metal thin film may be the same or different. The magnetic layer preferably has a total thickness of generally 500 to 5,000 liters.

As the support on which the magnetic layer is provided, a known non-magnetic support can be used without particular limitation. Specifically, known resins such as polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polycarbonate, polyamide, polyimide, polyamide imide, polysulfone, aramid, and aromatic polyamide; metals such as aluminum and copper; paper and the like are used. be able to. The form may be any of a film, tape, sheet, disk, drum and the like. Before providing the magnetic layer on the support, the surface of the support is previously subjected to corona discharge treatment in air and / or in vacuum,
Plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, bombardment treatment, and the like can also be performed. The preferred thickness of the support is 1 to 300 μm.

When a protective layer is provided on the magnetic layer, the protective layer is generally carbon, carbide, nitride or oxide, particularly diamond-like carbon, diamond, boron carbide, silicon carbide in vacuum. It is formed by forming a film of boron nitride, silicon nitride, silicon oxide, chromium oxide, aluminum oxide, or the like. As the protective layer, it is particularly preferable to use a carbon thin film layer in an amorphous state, a graphite state, a diamond state, or a mixed state or a laminated state thereof. The thickness of the protective layer is not particularly limited, but is generally 3
It is preferably 0 to 300Å. As the method of forming the protective layer, there are chemical vapor deposition (CVD method) and PVD.
Either method may be used. In the CVD method, an ECR (Electron Cyclotron Resonance) method using a microwave and a method using a high frequency (RF) are particularly effective. When the protective layer is formed by the CVD method, the raw material may be any of gas, liquid and solid.

In the magnetic recording medium of the present invention, other layers may be provided, if necessary, in addition to the above protective layer. For example, an undercoat layer may be provided between the support and the magnetic layer to improve the adhesion between the two, or a surface of the support opposite to the surface on which the magnetic layer is formed. In addition, a back coat layer for improving running properties and durability of the magnetic recording medium can be provided.

The above-mentioned fluorine-containing carboxylic acid ester can be applied on the above-mentioned back coat layer, if necessary. In this case, the back coat layer may be any of a coating type and a metal thin film type, but is preferably a metal thin film type back coat layer. The metal thin film type back coat layer is generally made of Al, Cu, Si, Fe, M.
It is formed by forming a film of o, Mn, Zn or the like, or an alloy or oxide of these. In general, the thickness of the back coat layer is preferably 500 to 10000Å. Further, regarding the adhesion amount of the fluorine-containing carboxylic acid ester in the back coat layer, the forming method, the additive, and the like, the detailed description regarding the magnetic layer side is similarly applied.

The magnetic recording medium of the present invention is used in the form of tape, disk, drum, sheet and other forms.
It is particularly preferably used in the form of a magnetic tape.

Other than the above description, points not particularly detailed
For, the explanation on the conventional magnetic recording medium is appropriate.
Used. In addition, the fluorine-containing calcium represented by the above formula (1)
In the case of boric acid ester, X is other than H or F
In addition, perfluoroalkylalkyl group, alkyl perf
Luoroalkyl group, perfluoroalkylalkyloxy
Si group, alkylperfluoroalkyloxy group, perf
Luoroalkyloxyalkyl group, alkyloxyper
Fluoroalkyl group, perfluoroalkyloxyal
Killoxy group, alkyloxy perfluoroalkyl
A xy group may be used. Also, R₁R_f1-Instead of the base,
R₁R_f1O-, R₁OR_f1-, R₁OR_f1O-, R_f3R
_Three-, R_f3R_ThreeO-, R_f3OR_Three-Or R_f3OR_ThreeO-
A group represented by (where R_f3Is a C1-C30 full
Represents an oroalkyl group, R_ThreeIs an alkane having 1 to 30 carbon atoms
Indicates a xylene group. ) May be used, as well as -R_TwoR
_f2Instead of a group, -OR_TwoR_f2, -R_TwoOR_f2, -OR_Two
OR_f2, -R_f4R_Four, -OR _f4R_Four, -R_f4OR_FourOr
-OR_f4OR_FourA group represented by (where R_FourIs the carbon number
1 to 30 alkyl groups, R_f4Has 1 to 30 carbon atoms
Is a fluoroalkylene group. ) May be used. Ma
Further, in the above formula (1), -CH_Two-COO- skeleton
Instead of -CH_Two-O-COO- skeleton may be used
No. Furthermore, in the above formula (1), -CH_Two-COO
R_TwoR_f2In place of the ester skeleton of _Two-CONH
-Amide skeleton and -CH_Two-COO^-NH_Three ⁺-Ami
A salt salt skeleton may be used.

[0035]

EXAMPLES The magnetic recording medium of the present invention will be described in more detail below with reference to examples. However, the present invention is not limited to such an embodiment.

Example 1 Synthesis of 2- (perfluorohexyl) ethyl 3,3,4,4-tetrafluoropentanoate 83 g and 1,1,2 of acrylic acid-2- (perfluorohexyl) ethyl ester A small amount of iodine was added to a mixture of 23 g of 2,2-tetrafluoropropyl iodide,
The reaction was carried out at 145 ° C for 8 hours. After completion of the reaction, distillation / purification was performed under reduced pressure to obtain a compound represented by the following formula (i) (yield 67%). The obtained compound represented by the following formula (i) was dissolved in absolute ethanol. Dry hydrogen chloride gas was bubbled into this solution, zinc powder was added, and the mixture was stirred at 70 ° C. After the reaction is completed, the zinc powder is filtered off,
The filtrate was extracted with ether. Further, distillation and purification were performed under reduced pressure to obtain the title target compound [compound represented by the following formula (ii)].

[0037]

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[0038]

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[Examples 2 to 6] The fluorine-containing carboxylic acid ester shown in Table 1 was synthesized in the same manner as in Example 1.

[0040]

[Table 1]

[Examples 7 to 12] On a PET film having a thickness of 6 μm, Co was deposited by oblique vapor deposition while introducing oxygen to form a ferromagnetic metal thin film magnetic layer having a thickness of 1800 Å. Next, 60 L of DLC was formed on the surface of the magnetic layer by the plasma CVD method. Next, each of the lubricants obtained in Examples 1 to 6 was dissolved in Fluorinert FC-77 (fluorine-based solvent, manufactured by 3M Co., Ltd.) so that the solution had a dry coating amount of 8 mg / m ^2. Each was applied to form a lubricant layer coating film. After drying the coating film 1
A metal thin film type magnetic tape was produced by slitting a width of / 4 inch.

With respect to each magnetic tape, the friction coefficient value (measurement conditions are shown below) in an environment of a temperature of 23 ° C. and a humidity of 50% RH was measured, and a relative speed of 10 was measured using the drum tester shown in FIG. The output fluctuation (ΔOutput) after running for 60 minutes at 0.2 m / s was measured (measurement conditions are shown below). Table 2 shows the results.

<Conditions for Measuring Friction Coefficient Value> As shown in FIG. 2, a sample magnetic tape 1 was hung on a φ5 mm SUS guide pin 2 so as to be in contact with the outer periphery of an angle of 115 ° (2 rad), and a load was applied to one end of the magnetic tape. (T ₂ ) 20 g is applied, and the tension T ₁ applied to the other end of the tape when running at a tape speed of 14.3 mm / s is measured. From the above results, the friction coefficient value μ was calculated from the following formula. μ = (1 / θ) ln (T ₁ / T ₂ )

<Specifications of Head Used in Drum Tester> Head used Hi8 mm VCR / EP head Track width: 15 μm Effective gap length: 0.23 μm

[Comparative Examples 1 to 5] Magnetic tapes were obtained in the same manner as in Example 7 except that no lubricant was used (Comparative Example 1).
Further, magnetic tapes were obtained in the same manner as in Example 7 except that DYNAM SA manufactured by Daikin Industries and Fomblin Z DOL manufactured by Aojimont were used as lubricants (Comparative Examples 2 and 3). Further, as a lubricant, R-COO-R
and a compound represented by _f (in the formula, R represents an alkyl group, R _f represents a fluoroalkyl group, and has an average molecular weight of 2500) and R _f '-R'-COOH (in the formula, R _f '
Is a perfluoroalkyl group and R ′ is an alkylene group. The average molecular weight is 2200. Magnetic tapes were obtained in the same manner as in Example 7 except that each of the compounds represented by (4) was used (Comparative Examples 4 and 5). The same measurement as in Example 7 was performed on each magnetic tape. Table 2 shows the results.

[0046]

[Table 2]

As is clear from the results shown in Table 2, the magnetic recording medium of the present invention (Examples 7 to 12) containing the fluorine-containing carboxylic acid ester represented by the above formula (1) has a friction coefficient value of It is low and no output fluctuation is observed. On the other hand, in the magnetic tape not using the lubricant (Comparative Example 1) and the magnetic tape using the conventional lubricant (Comparative Examples 2 to 5), the friction coefficient value was high and the decrease in the output was observed. It was

[0048]

As described above, according to the present invention,
Since the specific fluorine-containing carboxylic acid ester is used as the lubricant, a magnetic recording medium having a low friction coefficient value and little output fluctuation can be obtained. Therefore, the magnetic recording medium of the present invention is excellent in still durability and durability when recording / reproducing for a long time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a method of measuring an output fluctuation of a magnetic recording medium using a drum tester.

FIG. 2 is a schematic view showing an apparatus for measuring a friction coefficient of a magnetic tape.

[Explanation of symbols]

 1 magnetic tape 2 guide pin

Claims (3)

[Claims] 1. A magnetic recording medium comprising at least a magnetic layer on a non-magnetic support and containing a fluorinated carboxylic acid ester represented by the following formula (1). Embedded image (In the formula, R ₁ represents a linear or branched alkyl group having 1 to 30 carbon atoms, R ₂ represents a linear or branched alkylene group having 1 to 30 carbon atoms, and R _f1 represents Represents a linear or branched fluoroalkylene group having 1 to 30 carbon atoms, R
_f2 represents a linear or branched fluoroalkyl group having 1 to 30 carbon atoms, and X represents H or F. ) 2. The magnetic recording medium according to claim 1, wherein the fluorine-containing carboxylic acid ester is applied directly on the magnetic layer or via a protective layer provided on the magnetic layer. . 3. A fluorine-containing carboxylic acid ester lubricant for a magnetic recording medium represented by the following formula (1). Embedded image (In the formula, R ₁ represents a linear or branched alkyl group having 1 to 30 carbon atoms, R ₂ represents a linear or branched alkylene group having 1 to 30 carbon atoms, and R _f1 represents Represents a linear or branched fluoroalkylene group having 1 to 30 carbon atoms, R
_f2 represents a linear or branched fluoroalkyl group having 1 to 30 carbon atoms, and X represents H or F. )