JP2000219887A - Lubricant, magnetic recording medium and production of the same medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a lubricant composition having excellent lubricating performance and capable of imparting a highly, practically reliable magnetically recording medium excellent in running durability and still one without impairing electromagnetically transforming characteristics by including plural specific compounds having fluorine. SOLUTION: This lubricant composition is prepared by including (A) at least one kind of compounds of formula I [R1 is an alkyl or an alkenyl; R2 is a perfluoroalkyl or a perfluoropolyether; (a) is 0-20; (b) is 0 or 1] and/or formula II [R3 is an alkyl or an alkenyl; R4 is a perfluoroalkyl or a perfluoropolyether; R5 is 0 or S; (c) is 0-20; (d) is 0 or 1] and (B) a compound of formula III [R6 is an alkyl or an alkenyl; R7 is a perfluoroalkyl or a perfluoropolyether; R8 is O or S; (e) is 0-20; (f) is 0 or 1; R9-R11 are each a 1-20C hydrocarbon] preferably at a ratio (the compound A/the compound B) of (8/2)-(2/8).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricant composition exhibiting excellent lubricating performance, and a ferromagnetic metal thin film as a magnetic recording layer which is most suitable for a digital video tape recorder or a high definition video tape recorder. The present invention relates to a magnetic recording medium having a carbon film thereon and a lubricant layer thereon, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in the field of magnetic recording, with the advancement of digitalization, miniaturization, and prolonged use time of recording / reproducing devices, development of high-density magnetic recording media suitable therefor has been required. It has been actively performed, and recently, a metal thin film type magnetic recording medium which is extremely advantageous for short wavelength recording has been put to practical use instead of a coating type magnetic recording medium. In general, a metal thin film type magnetic recording medium refers to a tape, a disk, or the like in which a magnetic layer made of a ferromagnetic metal thin film is provided as a recording layer on a nonmagnetic substrate.

However, the magnetic layer of a metal thin film type magnetic recording medium has extremely good surface properties, that is, the surface roughness of the magnetic layer is small, so that the contact area with the magnetic head increases. During the reproduction process, the magnetic head is easily worn due to a large frictional force while sliding at a high speed with the magnetic head. Abrasion of the magnetic layer greatly affects running durability, still durability, and the like of the magnetic recording medium, and reducing it is a major issue in research and development of metal thin-film magnetic recording media.

[0004] Therefore, attempts have been made to reduce wear by providing a lubricant layer on the surface of the magnetic layer to improve running durability and still durability. When a lubricant layer is provided, the lubricant layer on the surface of the magnetic layer exhibits lubricating properties with a thickness of only a few nm in order to minimize output loss due to spacing loss between the magnetic recording medium and the magnetic head and achieve high output. Is required. Therefore, the use of fluorine-based compounds exhibiting excellent lubrication properties has been widely studied, and the use of various compounds has been proposed. For example,

Embedded image Fluorinated long-chain carboxylic acid ester represented by C ₁₈ H ₃₅ OCOC ₉ F ₁₇
-46431) or (Formula 17):

Embedded image It has been proposed to use a fluorine-containing carboxylic acid monoester having a carboxyl group (see JP-A-61-107529).

[0005]

However, there is a severe demand for improving the performance of a magnetic recording medium, and it is difficult to obtain sufficient lubricating characteristics with the above-mentioned conventional lubricant.
Further improvements in running durability and still durability are desired.

[0006] In view of the above problems, the present invention provides a lubricant composition which is capable of obtaining a magnetic recording medium which is excellent in running durability and still durability and has high practical reliability without impairing the electromagnetic conversion characteristics. It is intended to provide a magnetic recording medium using the lubricant composition and a method for producing the same.

[0007]

SUMMARY OF THE INVENTION The lubricant composition of the present invention comprises two or more specific fluorine-containing compounds. Thereby, for example, when a lubricant layer of a magnetic recording medium is formed using this lubricant composition, the adhesion strength to the carbon film located thereunder of the lubricant layer is improved, and excellent lubrication characteristics are obtained. Since the magnetic recording medium is applied to the magnetic recording medium, the magnetic recording medium exhibits excellent running durability and still durability without impairing its electromagnetic conversion characteristics.

[0008] The lubricant composition of the present invention contains a perfluoroalkyl group or a perfluoropolyether group in the molecule.
And having an alkyl group or an alkenyl group, general formulas (a) and (b):

Embedded image (Wherein, R ¹ is an alkyl group or an alkenyl group;
R ² is a perfluoroalkyl group or a perfluoropolyether group, a is an integer of 0 to 20, and b is 0
Or 1. )

Embedded image (Wherein R ³ is an alkyl group or an alkenyl group;
R ⁴ is a perfluoroalkyl group or a perfluoropolyether group; R ⁵ is O or S;
An integer of 20; d is 0 or 1; And at least one compound selected from the compounds represented by the general formula (c) having a perfluoroalkyl group or a perfluoropolyether group and an alkyl group or an alkenyl group in the molecule:

Embedded image (Wherein, R ⁶ is an alkyl group or an alkenyl group;
R ⁷ is a perfluoroalkyl group or a perfluoropolyether group; R ⁸ is O or S;
To 20 and f is 0 or 1, and
R ⁹ , R ¹⁰ and R ¹¹ are any of a hydrocarbon group and hydrogen, and the hydrocarbon group has 1 to 20 carbon atoms. ), Wherein at least one compound selected from the compounds represented by the formula (1) is included.

The compounds represented by the general formulas (a) to (c) are all fluorine-containing compounds. The lubricant composition comprises at least one compound selected from fluorinated monocarboxylic acids (a) and (b) and at least one selected from salts formed from fluorinated alkylcarboxylic acids and amines or ammonia. And one kind of compound. The compound represented by the general formula (a) can be said to be a fluorinated carboxylic acid monoester having one carboxyl group.

[0010] The composition is, for example, on a non-magnetic substrate,
If the ferromagnetic metal thin film, the carbon film, and the lubricant layer are included in the lubricant layer of a magnetic recording medium (hereinafter sometimes simply referred to as a metal thin film type magnetic recording medium) formed in this order, The adhesive strength of the agent layer to the carbon film is improved, and excellent lubricating properties are imparted to the magnetic recording medium. By these synergistic effects, it is possible to obtain a magnetic recording medium with high practical reliability in which running durability and still durability are improved without impairing the electromagnetic conversion characteristics.

Further, the lubricant composition of the present invention may further contain an organic phosphorus compound. The organophosphorus compound acts as an extreme pressure agent and / or a rust inhibitor, and when it is contained in the lubricant layer of the metal thin film type magnetic recording medium, reduces the adhesion strength between the lubricant layer and the carbon film. Since it also plays a role of improving, the lubrication performance, running durability and still durability of the magnetic recording medium are further improved, and as a result, the practical reliability of the magnetic recording medium is further improved.

Specifically, the following general formulas (g) and (h)
(I) (j) (k) (l) (m) (n) and (o):

Embedded image HP (O) (OC _n H _{2n + 1} ) ₂ ... (G)

Embedded image P (OC _n H _{2n + 1} ) ₃ ... (H)

_{Embedded image} P (SC _n H _{2n + 1} ) ₃ ... (I)

Embedded image O = P (OC _n H _{2n + 1} ) ₃ ... (J)

Embedded image S = P (OC _n H _{2n + 1} ) ₃ ... (K)

Embedded image O = P (SC _n H _{2n + 1} ) ₃ ... (L)

Embedded image S = P (SC _n H _{2n + 1} ) ₃ ... (M)

_{Embedded image} (C _n H _{2n + 1} O) ₂ P (O) OH ... (n)

(C _n H _{2n + 1} O) P (O) (OH) ₂ ... (O) (in the above general formulas (g) to (o), n is 8 to 20)
Is an integer. It is preferable to use at least one organic phosphorus compound selected from the group consisting of the organic phosphorus compounds represented by the formula (1).

When the lubricant composition containing these specific organic phosphorus compounds is used in, for example, a lubricant layer of a metal thin film type magnetic recording medium, the practical reliability of the magnetic recording medium is further improved.

The magnetic recording medium of the present invention is a magnetic recording medium in which a ferromagnetic metal thin film, a carbon film and a lubricant layer are formed in this order on a non-magnetic substrate, wherein the lubricant layer has the above-mentioned lubricant composition. It is characterized by including an object. By using a lubricant composition in which two or more of the above-mentioned specific fluorine-containing compounds are combined, the adhesion strength of the lubricant layer to the carbon film located thereunder is improved, and excellent lubricating properties are obtained for a magnetic recording medium. Granted. By these synergistic effects, it is possible to obtain a magnetic recording medium having high running reliability and still durability with high practical reliability without impairing the electromagnetic conversion characteristics.

The method of manufacturing a magnetic recording medium according to the present invention is characterized by the step of forming a lubricant layer. Other manufacturing steps may be steps conventionally used for manufacturing a magnetic recording medium. The step of forming a lubricant layer in the production method of the present invention comprises applying a coating solution prepared by dissolving the above-described lubricant composition in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent, at a relative humidity of 10 to 40. % In an environment within the range of 0.1%, and a step of drying the mixed organic solvent on the carbon film. By applying a coating liquid containing a lubricant composition under specific humidity conditions using a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent, the adhesion strength between the lubricant layer and the carbon film is improved. In addition, a uniform thin lubricant layer with very little coating unevenness can be formed. Therefore, according to the manufacturing method of the present invention, it is possible to obtain a highly practical magnetic recording medium having excellent lubrication performance.

In the above production method of the present invention, the mixing ratio of the hydrocarbon solvent and the alcohol solvent is 1: 1:
It is preferably in the range of 9 to 9: 1. Mixing both in this range makes it possible to minimize coating unevenness and is advantageous in terms of cost.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The fluorine-containing compounds contained in the lubricant composition of the present invention are represented by the above general formulas (a) to (c).

The compound represented by the general formula (a) can be said to be a fluorinated carboxylic acid monoester having one carboxyl group. This compound can be obtained, for example, by converting one of the two carboxyl groups contained in a dicarboxylic acid such as succinic acid into an ester.

In the general formula (a), R ¹ is an alkyl group or an alkenyl group, and R ² is a perfluoroalkyl group or a perfluoropolyether group. a is usually an integer of 0 to 20, preferably 1 to 10. b is 0 or 1. R in the general formula (a)
The carbon number of ¹ is preferably from 6 to 30, more preferably from 10 to 24. When the number of carbon atoms is less than 6 or more than 30, the lubricity may decrease.

When R ² is a perfluoroalkyl group, it preferably has 6 to 12 carbon atoms, more preferably 6 to 10 carbon atoms. When R ² is a perfluoropolyether group, the molecular weight is preferably about 200 to about 6000, and more preferably about 300 to about 4000. If the molecular weight is less than 200 or exceeds 6000, lubricity and storage reliability may decrease.

When R ² is a perfluoropolyether group, the perfluoropolyether group has the general formula (d), (e) and (f):

Embedded image (In the formula, q is an integer of 1 or more.)

Embedded image (In the formula, r and t are integers of 1 or more.)

Embedded image ^{_{R 12 (OC u F 2u)}} v O (CF 2) u-1 - ... (f) ( wherein, R ¹² is a perfluoroalkyl group, u is 1
And v is an integer of 1 to 30. ) Is preferable.

When the above compound having a perfluoropolyether group is contained in the lubricant composition, for example, when the composition is contained in the lubricant layer of a metal thin-film type magnetic recording medium, the lubricant layer Is further improved, and more excellent lubricating properties are imparted to the magnetic recording medium. By these synergistic effects, it is possible to obtain a magnetic recording medium with high practical reliability in which running durability and still durability are improved without impairing the electromagnetic conversion characteristics.

In the general formula (d), q is an integer of 1 or more. Further, r and t in the general formula (e) are integers of 1 or more. In the general formula (f), R ¹² is a perfluoroalkyl group, u is usually an integer of 1 to 6, v is usually an integer of 1 to 30, and more preferably 1
８8. If u and v are outside these ranges,
Lubricity and storage reliability of the magnetic recording medium may decrease. q, r, t, the number of carbon atoms of u and v and R ¹² are the preferred range of the molecular weight of the perfluoropolyether group is described above, i.e. from about 200 to about 6000 nm, preferably about 3
It is suitably selected to be in the range of 00 to about 4000.

In the general formula (b), R ³ is an alkyl group or an alkenyl group, and R ⁴ is a perfluoroalkyl group or a perfluoropolyether group. R ⁵ is an oxygen atom or a sulfur atom. c is usually an integer of 0 to 20, preferably 1 to 10. d is 0 or 1. The carbon number of R ³ in the general formula (b) is 6
To 30 is preferable, and 10 to 24 is more preferable. When the number of carbon atoms is less than 6 or more than 30, the lubricity may decrease.

When R ⁴ is a perfluoroalkyl group, it preferably has 6 to 12 carbon atoms, more preferably 6 to 10 carbon atoms. When R ⁴ is a perfluoropolyether group, the molecular weight is preferably about 200 to about 6000, and more preferably about 300 to about 4000. When the molecular weight is less than 200 or more than 6000, lubricity and storage reliability may decrease.

When R ⁴ is a perfluoropolyether group, R ⁴ is represented by any of the above formulas (d), (e) and (f), similarly to R ² in formula (a). Preferably, the group is The general formulas (d), (e) and (f) are as described above in relation to the general formula (a), and the detailed description is omitted here by citing the description.

[0027] In general formula (c), R ⁶ is an alkyl or alkenyl group, R ⁷ is a perfluoroalkyl group or perfluoropolyether group,, R ⁸
Is an oxygen atom or a sulfur atom, e is an integer of 0 to 20, and f is 0 or 1. Also, R ⁹ , R ¹⁰ ,
R ¹¹ is either a hydrocarbon group or hydrogen, and when it is a hydrocarbon group, it preferably has 1 to 20 carbon atoms.

When R ⁶ is a perfluoroalkyl group, it preferably has 6 to 12 carbon atoms, more preferably 6 to 10 carbon atoms. If R ⁷ is a perfluoropolyether group preferably has a molecular weight of about 200 to about 6000, more preferably from about 300 to about 4000. When the molecular weight is less than 200 or more than 6000, lubricity and storage reliability may decrease.

In particular, when R ⁷ is a perfluoropolyether group, R ⁷ is represented by any of the above formulas (d), (e) and (f), similarly to R ² in formula (a). It is preferably a group. The general formulas (d), (e) and (f) are as described above in relation to the general formula (a), and the detailed description is omitted here by citing the description.

R ⁹ , R ¹⁰ and R ¹¹ are any of a hydrocarbon group and hydrogen. R ⁹ , R ¹⁰ , and R ¹¹ may all be the same or they may all be different. Also, two of the three may be the same. In the present invention, at least one of R ⁹ , R ¹⁰ and R ¹¹ is preferably a hydrocarbon group. R ⁹ ,
When any one or more of R ¹⁰ and R ¹¹ is a hydrocarbon group, it preferably has 1 to 20 carbon atoms, and more preferably 6 to 18 carbon atoms.

The lubricant composition of the present invention comprises at least one compound selected from the compounds represented by formulas (a) and (b)
And at least one compound selected from the general formula (c).
The molar ratio of the former and the latter is preferably in the range of 8: 2 to 2: 8, more preferably 7: 3 to 4: 6 in molar ratio.
Range. If the former ratio is small, the lubricating performance may decrease, and if the latter ratio is small, the adhesion strength to the carbon film may decrease.

Each of the above lubricant compositions may further contain an organic phosphorus compound in the lubricant layer. In the present invention, it is particularly preferable to use at least one organic phosphorus compound selected from the group consisting of the general formulas (g) to (o). In the general formulas (g) to (o), the number (n) of carbon atoms constituting each compound is preferably from 8 to 20, and more preferably from 10 to 18. If the number of carbon atoms is 7 or less, the lubricity may decrease, and if it exceeds 21, the solubility in general-purpose solvents such as hydrocarbon solvents or alcohol solvents decreases. The decrease in solubility in a general-purpose solvent hinders the production of a magnetic recording medium, for example, when a lubricant layer of a metal thin-film magnetic recording medium is formed from this composition.

The mixing ratio between the total amount of the lubricant composition excluding the organic phosphorus compound and the organic phosphorus compound is 1: 1 in molar ratio.
１ ： 1: 0.01, preferably 1: 0.3〜
More preferably, it is in the range of 1: 0.02. If the mixing ratio of the organophosphorus compound is too large, the lubricating performance deteriorates, and if it is too small, the action and effect of the organophosphorus compound cannot be sufficiently obtained.

The magnetic recording medium of the present invention is a magnetic recording medium in which a ferromagnetic metal thin film, a carbon film, and a lubricant layer are formed in this order on a non-magnetic substrate. It contains a composition. So, next,
Each layer constituting the magnetic recording medium of the present invention will be described together with a method of manufacturing the same with reference to the drawings.

FIG. 1 is a sectional view of a metal thin film type magnetic tape (hereinafter, simply referred to as a magnetic tape) which is one embodiment of the magnetic recording medium of the present invention. This magnetic tape has a configuration in which a back coat layer (5), a non-magnetic substrate (1), a ferromagnetic metal thin film (2), a carbon film (3), and a lubricant layer (4) are laminated in this order from the bottom. . As described above, the layers other than the lubricant layer and the method of forming the layers are known, and conventional materials and forming methods can be employed.

For example, as the non-magnetic substrate (1), a film made of polyethylene terephthalate, polyethylene naphthalate, aromatic polyamide or aromatic polyimide, an aluminum substrate or a glass substrate can be used. In order to achieve both practical reliability and good RF output, the surface of the nonmagnetic substrate (1), that is, the surface in contact with the ferromagnetic metal thin film, has a diameter of 50 to 700 nm and a height of 5 nm.
It is preferable that a projection forming process of up to 70 nm is performed.

The ferromagnetic metal thin film (2) can be formed by an ion plating method, a sputtering method, an electron beam evaporation method, or the like. Co, F
ferromagnetic metals such as e and Ni, and Co-Ni, Co
-Ni-O, Co, Co-O, or Co-Cr. The thickness of the ferromagnetic metal thin film (2) is 50 to
300 nm is common.

The carbon film (3) has a Vickers hardness of about 2500.
It is as high as kg / mm ² , preventing damage to the magnetic tape together with the lubricant layer (4). In consideration of the balance between practical reliability and output, the thickness is preferably 10 to 20 nm. This carbon film (3) is composed of only hydrocarbon gas,
Alternatively, it is formed by a plasma CVD method using a mixed gas of a hydrocarbon gas and an inert gas. Specifically, a hydrocarbon gas or a mixed gas of a hydrocarbon gas and an inert gas such as argon is introduced into a vacuum vessel, and the pressure in the vessel is reduced to 0.
Discharge is generated inside the vacuum vessel while maintaining the pressure at 001 to 1 Torr, and a plasma of hydrocarbon gas is generated to form the carbon film (3) on the ferromagnetic metal thin film (2). The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency can be determined experimentally. Also,
0 KV to -3 KV for the electrode arranged on the non-magnetic substrate (1) side
By applying this voltage, the hardness of the carbon film (3) can be increased, and the adhesion between the carbon film (3) and the ferromagnetic metal thin film (2) can be improved. As the hydrocarbon gas, methane, ethane, propane, butane, pentane, hexane, heptane, octane or benzene can be used.

In order to form the hard carbon film (3), it is desirable to increase discharge energy, and it is also desirable to maintain the temperature of the non-magnetic substrate (1) at a high temperature. For example, the discharge energy is desirably set to an effective value of 600 V or more by superimposing an alternating current, for example, a high-frequency current and a direct current.

In the present invention, a nitrogen-containing plasma polymerized film (not shown) is formed on the surface layer of the carbon film (3), and the lubricant layer (4) is formed on the nitrogen-containing plasma polymerized film of the carbon film. Is preferred. Amino groups are present in the surface layer of the carbon film due to the nitrogen-containing plasma polymerization, and as a result,
The adhesion strength between the lubricant layer and the carbon film becomes larger,
The durability of the magnetic recording medium is further improved. In combination with the inclusion of a specific fluorine-containing compound or the like in the lubricant layer, practical durability with improved running durability and still durability having excellent lubrication performance without impairing electromagnetic conversion characteristics. A high magnetic recording medium can be obtained.

The nitrogen-containing plasma polymerized film is obtained by gasifying and introducing an amine compound such as propylamine, butylamine, ethylenediamine, propylenediamine or tetramethylenediamine into a vacuum vessel, and reducing the pressure in the vessel to 0.001.
While maintaining the pressure at １1 Torr, high-frequency discharge is performed inside the vacuum vessel to form the vacuum container. By forming the nitrogen-containing plasma polymerized film, the chemical adsorption power of the lubricant composition is improved, and as a result, the adhesion strength between the lubricant layer and the carbon film is improved. The film thickness of the nitrogen-containing plasma polymerized film is suitably less than 3 nm. If the nitrogen-containing plasma polymerized film is thicker than this, the protective effect of the carbon film is reduced. The method for forming a nitrogen-containing plasma polymerized film on the surface layer of a carbon film is disclosed in U.S. Patent Nos. 5,540,957 and 5,637,393, and the contents disclosed in these patents by this citation are described in the present specification. Make up part.

The lubricant composition constituting the lubricant layer (4) is as described above. The step of forming the lubricant layer (4) includes:
A lubricant comprising a mixture of at least one compound selected from the compounds represented by the above general formulas (a) and (b) and at least one compound selected from the compounds represented by the above general formula (c) A composition or a lubricant composition obtained by mixing an organic phosphorus-based compound with the composition is dissolved in a mixed organic solvent of a hydrocarbon-based solvent and an alcohol-based solvent to prepare a coating solution. % In the environment within the range of%.

The hydrocarbon solvents that can be used in the present invention include, for example, toluene, hexane, heptane, and octane. The alcohol solvents that can be used in the present invention include, for example, methyl alcohol, ethyl alcohol, propyl alcohol, and isopropyl alcohol. Is a lower alcohol. If the proportion of the alcohol-based solvent is too large, coating unevenness is likely to occur. On the other hand, if the proportion of the hydrocarbon-based solvent is too large, it is uneconomical, and the mixing ratio of the two is in the range of 1: 9 to 9: 1 by weight. It is preferable to mix and use them in a range of preferably 3: 7 to 7: 3. The concentration and the coating thickness of the coating liquid are applied such that the lubricant layer (4) formed on the carbon film (3) after the solvent evaporates has a desired thickness. In general, it is preferable to apply a coating solution having a lubricant composition concentration of 100 to 4000 ppm so as to have a thickness of 1 to 50 μm.

The coating solution is preferably applied in an environment where the relative humidity is in the range of 10 to 40%. When the relative humidity is less than 10%, static electricity is easily generated, and there is a problem that equipment for creating an environment of such humidity is expensive, and when the relative humidity exceeds 40%, application unevenness is apt to occur. There's a problem.

The optimum thickness of the lubricant layer (4) is determined according to the lubricant composition, and the thickness is generally 3 to 5 nm.
The coating method may be any of a wet coating method such as a bar coating method, a gravure coating method, a reverse roll coating method, a die coating method, a dip coating method or a spin coating method, or an organic vapor deposition method.

After the coating solution is applied, the organic solvent is evaporated by drying treatment, and a layer (4) of the lubricant composition is formed on the carbon film (3). By heating the drying process,
Alternatively, it can be carried out by natural drying.

By using this mixed organic solvent, it is possible to obtain a lubricant layer having a uniform thickness without coating unevenness, and to form a very thin lubricant layer of several nm after the solvent is finally evaporated. Can be. As a result, a highly reliable magnetic recording medium having excellent lubrication performance can be obtained.

The back coat layer (5) is made of polyurethane,
The layer is formed of one or more materials selected from nitrocellulose, polyester, carbon, calcium carbonate, and the like, and preferably has a thickness of about 500 nm.

[0049]

EXAMPLES Next, specific examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1 A non-magnetic substrate (1) having a width of 500 mm, a thickness of 6.3 μm, and a height of 30
nm, in diameter was used a polyethylene terephthalate film which projections are formed 10 ⁹ from 1 mm ² per 10 ⁵ 200 nm. The number of protrusions is a value measured by STM analysis.
On the surface of the non-magnetic substrate (1), a 180 nm thick ferromagnetic metal thin film (2) of Co (80) -Ni (20) (in parentheses, a mixture molar ratio) is formed by oblique vacuum evaporation while introducing oxygen. ) Formed.

Next, a 30% solids solution of methyl ethyl ketone / toluene / cyclohexanone composed of polyurethane, nitrocellulose and carbon black is applied to the back surface of the nonmagnetic substrate (1) by a reverse roll coater, and the thickness after drying is applied. Formed a back coat layer (5) of about 500 nm.

Next, a 15 nm-thick carbon film (3) was formed on the ferromagnetic metal thin film (2) by a plasma CVD method. As the carbon film, a gas obtained by mixing hexane gas and argon gas at a ratio of 4: 1 (pressure ratio) into a vacuum vessel is introduced.
While maintaining the total gas pressure at 0.3 Torr, the frequency 20
It was formed by superimposing an alternating current of KHz and a voltage of 1500 V and a direct current of 1000 V, and applying this to an electrode in a discharge tube. Further, propylamine gas was introduced onto the carbon film (3) to
While maintaining a pressure of 05 Torr, high-frequency plasma treatment at 10 KHz was performed to form a 2.5-nm nitrogen-containing plasma polymerized film on the surface layer of the carbon film (3).

Next, a lubricant composition comprising the compound represented by the chemical formula (a1) and the compound represented by the chemical formula (c1) in a molar ratio of 1: 1 was prepared by adding isopropyl alcohol and toluene by weight. A coating solution was prepared by dissolving in a mixed organic solvent mixed at a ratio of 1: 1 so that the concentration became 2000 ppm. Then, the coating solution is heated at 23 ° C.
The coating was performed by a wet coating method using a reverse roll coater in a 30% RH environment, and then dried. Finally, a 4 nm lubricant layer (4) was formed on the carbon film (3).

Embedded image

Embedded image 8mm of the tape material prepared as above with a slitter
The tape was cut into a width to prepare a magnetic tape sample having a width of 8 mm (total thickness: 7 μm, 60 minutes long).

(Examples 2 to 6) Chemical formulas (a2) to
(A6) Except for using a lubricant composition in which the compound represented by (corresponding to Examples 2 to 6) and the compound represented by the chemical formula (c1) were blended at a molar ratio of 1: 1 respectively. Magnetic tape samples were produced in the same manner as in Example 1.

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(Examples 7 to 11) Chemical formula (b1)
Except for using a lubricant composition in which a compound represented by (b5) (corresponding to Examples 7 to 11) and a compound represented by the chemical formula (c1) were blended at a molar ratio of 1: 1 respectively. Produced a magnetic tape sample in the same manner as in Example 1.

Embedded image

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(Examples 12 to 22) Chemical formula (a)
1) to (a6) (corresponding to Examples 12 to 17), compounds represented by chemical formulas (b1) to (b5) (corresponding to Examples 18 to 22), and a compound represented by chemical formula (c2), respectively. A magnetic tape sample was prepared in the same manner as in Example 1, except that a lubricant composition mixed at a molar ratio of 1: 1 was used.

Embedded image

(Examples 23 to 33) Chemical formula (a)
1) to (a6) (corresponding to Examples 23 to 28), compounds represented by chemical formulas (b1) to (b5) (corresponding to Examples 29 to 33), and a compound represented by chemical formula (c3), respectively. A magnetic tape sample was prepared in the same manner as in Example 1, except that a lubricant composition mixed at a molar ratio of 1: 1 was used.

Embedded image

(Examples 34 to 39) Chemical formula (a)
1) to (a6) (corresponding to Examples 34 to 39), compounds represented by chemical formulas (b1) to (b5) (corresponding to Examples 40 to 44), and a compound represented by chemical formula (c4), respectively. A magnetic tape sample was prepared in the same manner as in Example 1, except that a lubricant composition mixed at a molar ratio of 1: 1 was used.

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(Examples 45 to 50) Chemical formula (a)
1) to (a6) (corresponding to Examples 45 to 50), compounds represented by chemical formulas (b1) to (b5) (corresponding to Examples 51 to 55), and a compound represented by chemical formula (c5) A magnetic tape sample was prepared in the same manner as in Example 1, except that a lubricant composition mixed at a molar ratio of 1: 1 was used.

Embedded image

(Examples 56 to 61) Chemical formula (a)
1) to (a6) (corresponding to Examples 56 to 61), compounds represented by chemical formulas (b1) to (b5) (corresponding to Examples 62 to 66), and a compound represented by chemical formula (c6), respectively. A magnetic tape sample was prepared in the same manner as in Example 1, except that a lubricant composition mixed at a molar ratio of 1: 1 was used.

Embedded image

Example 67 A lubricant composition in which a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (c1) were mixed at a molar ratio of 4: 1 was used. A magnetic tape sample was produced in the same manner as in Example 1.

Example 68 A lubricant composition in which a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (c1) were mixed at a molar ratio of 1: 4 was used. A magnetic tape sample was produced in the same manner as in Example 1.

(Examples 69 to 77) Chemical formula (a)
A two-component lubricant composition containing a compound represented by the formula (1) and a compound represented by the chemical formula (c1) (molar ratio 1:
Instead of 1), the compound represented by the chemical formula (a1), the compound represented by the chemical formula (c1), and the compound represented by the chemical formula (g)
1), (h1), (i1), (j1), (k1), (l
1), (m1), (n1) or (o1) (Example 6)
9 to 77) (in a molar ratio of 5: 5:
A magnetic tape sample was prepared in the same manner as in Example 1 except that 1) was used.

Embedded image HP (O) (OC ₁₂ H ₂₅ ) ₂ ... (G1)

Embedded image P (OC ₁₀ H ₂₁ ) ₃ ... (H1)

Embedded image P (SC ₁₂ H ₂₅ ) ₃ ... (I1)

Embedded image O = P (OC ₁₈ H ₃₇ ) ₃ ... (J1)

Embedded image S = P (OC ₁₈ H ₃₇ ) ₃ ... (K1)

Embedded image O = P (SC ₁₂ H ₂₅ ) ₃ ... (11)

Embedded image S = P (SC ₁₈ H ₃₇ ) ₃ ... (M1)

Embedded image (C ₁₂ H ₂₅ O) ₂ P (O) OH (n1)

(C ₁₂ H ₂₅ O) P (O) (OH) ₂ ... (o1)

Example 78 A mixture of a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (c1) 2
A compound represented by the chemical formula (a1), a compound represented by the chemical formula (c1), and an organic phosphorus-based compound represented by the chemical formula (g1) are blended in place of the component-based lubricant composition (molar ratio 1: 1) A magnetic tape sample was prepared in the same manner as in Example 1 except that the three-component lubricant composition (molar ratio 1: 1: 2) was used.

Example 79 A mixture of a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (c1) 2
A compound represented by the chemical formula (a1), a compound represented by the chemical formula (c1), and an organic phosphorus-based compound represented by the chemical formula (g1) are blended in place of the component-based lubricant composition (molar ratio 1: 1) A magnetic tape sample was prepared in the same manner as in Example 1 except that the three-component lubricant composition (molar ratio 25: 25: 1) was used.

(Example 80) A magnetic tape sample was prepared in the same manner as in Example 1 except that the step of forming a nitrogen-containing plasma polymerized film on the surface portion of the carbon film (3) was omitted.

Example 81 A magnetic tape sample was produced in the same manner as in Example 1 except that the weight ratio of the organic solvent composed of isopropyl alcohol and toluene was changed from 1: 1 to 8: 1.

(Example 82) A magnetic tape sample was prepared in the same manner as in Example 1 except that the weight ratio of the organic solvent composed of isopropyl alcohol and toluene was changed from 1: 1 to 1: 8.

(Comparative Example 1) Instead of a two-component lubricant composition containing a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (c1), the above-mentioned chemical formula A magnetic tape sample was prepared in the same manner as in Example 1 except that only the compound represented by 16) was used.

(Comparative Example 2) Instead of a two-component lubricant composition containing a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (c1), the known chemical formula A magnetic tape sample was prepared in the same manner as in Example 1 except that only the compound represented by 17) was used.

Comparative Example 3 Instead of a two-component lubricant composition comprising a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (c1), only the compound represented by the chemical formula (a1) was used. A magnetic tape sample was prepared in the same manner as in Example 1 except that the magnetic tape sample was used.

(Comparative Example 4) Instead of a two-component lubricant composition containing a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (c1), only the compound represented by the chemical formula (c1) was used. A magnetic tape sample was prepared in the same manner as in Example 1 except that the magnetic tape sample was used.

(Comparative Example 5) Instead of a two-component lubricant composition comprising a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (c1), only the compound represented by the chemical formula (g1) was used. A magnetic tape sample was prepared in the same manner as in Example 1 except that the magnetic tape sample was used.

Comparative Example 6 A magnetic tape sample was prepared in the same manner as in Example 1, except that only isopropyl alcohol was used instead of the mixed organic solvent consisting of isopropyl alcohol and toluene.

Comparative Example 7 A magnetic tape sample was prepared in the same manner as in Example 1 except that only toluene was used instead of the mixed organic solvent composed of isopropyl alcohol and toluene.

Comparative Example 8 A magnetic tape sample was prepared in the same manner as in Example 1 except that the coating solution was applied by a wet coating method using a reverse roll coater in an environment of 23 ° C. and 55% RH. did.

The above Examples 1 to 82 and Comparative Examples 1 to
The following evaluation tests (1) and (2) were performed on the magnetic tape samples having a width of 8 mm obtained in Step 8 above.
Tables 1 to 9 show the results obtained in each test.

(1) Running durability test Commercially available 8 mm VTR modified for measuring RF (high frequency) output
Using a Sony (EV-S900, manufactured by Sony Corporation), the change in RF output after repeated reproduction of each 8 mm wide tape sample for 300 passes in an environment of 5 ° C. and 80% RH for 300 hours was measured. Changes after the test compared to before the test are shown in decibels. The tape damage was evaluated in five stages by visually observing the tape sample and observing the state with a differential interference microscope. The evaluation criteria are as follows. 5: There is no problem in practical use. 4: There is no practical problem. 3: Practical, but needs improvement. 2: The tape is severely damaged and practically not practical. 1: The tape damage is too bad and there is no practicality at all.

(2) Still Life Test The initial still life was calculated using a commercially available 8 modified for still life measurement.
mm VTR (EV-S900 manufactured by Sony Corporation)
It was measured under a 5% RH environment. In addition, the still life was represented by the time from the initial stage until the output decreased by 6 dB. The post-storage still life was measured in the same manner as in the initial still life measurement after leaving it for one month in an environment of 40 ° C. and 80% RH.

[Table 1] Reduction in running durability Still life output Tape still life Initial still life Still life after storage (dB) (Minutes) (Min) Example 1 -0.75> 60 44 Example 2 -1.45> 60 35 Example 3 -1.45> 60 38 Example 4 -1.35> 60 39 Example 5 -0.85> 6047 Example 6-1.34> 6036 Example 7-0.95> 6048 Example 8-1.25> 6041 Example 9-1.35> 60 38 Example 10 -0.95> 60 46 Example 11 -1.44> 60 37

[Table 2] Decrease in running durability still life output taper machine Initial still life Still life after storage (dB) (Minutes) (Minutes) Example 12 -0.95> 60 44 Example 13 -1.35> 60 35 Example 14 -1.44> 60 41 Example 15 -1.45> 60 39 Example 16 -0.85> 6045 Example 17-1.34> 6041 Example 18-0.85> 6043 Example 19-1.45> 6040 Example 20-1.24> 60 37 Example 21 -1.04> 60 39 Example 22 -1.24> 60 43

[Table 3] Reduction of running durability still life output Tape still life Initial still life Still life after storage (dB) (Minutes) (Min) Example 23 -1.05> 60 55 Example 24 -1.25> 60 46 Example 25-1.14> 60 49 Example 26 -1.25> 60 47 Example 27 -0.95> 6052 Example 28-1.44> 6038 Example 29-1.05> 6049 Example 30-1.45> 6042 Example 31-1.34> 60 41 Example 32 -0.95> 60 55 Example 33-1.14> 60 37

[Table 4] Decrease in running durability still life output taper machine Initial still life Still life after storage (dB) (Minutes) (Minutes) Example 34-1.15> 6052 Example 35-1.45> 6033 Example 36-1.35> 6041 Example 37-1.55> 6039 Example 38 -1.05> 6043 Example 39-1.45> 6047 Example 40-0.85> 6047 Example 41-1.45> 6041 Example 42-1.35> 60 45 Example 43-1.15> 60 52 Example 44-1.55> 60 39

[Table 5] Reduction of running durability still life output taper machine Initial still life Still life after storage (dB) (Minutes) (Minutes) Example 45-1.05> 6044 Example 46-1.54> 6037 Example 47-1.34> 6038 Example 48-1.54> 6041 Example 49 -0.85> 6045 Example 50-1.24> 6049 Example 51-0.95> 6047 Example 52-1.15> 6039 Example 53-1.44> 60 38 Example 54 -0.55> 60 51 Example 55 -1.64> 60 32

[Table 6] Reduction of running durability still life output Tape cutter machine Initial still life Still life after storage (dB) (Minutes) (Minutes) Example 56-1.35> 6045 Example 57-1.54> 6036 Example 58-1.64> 6032 Example 59-1.44> 6035 Example 60 -0.85> 6041 Example 61-1.44> 6037 Example 62-1.25> 6039 Example 63-1.54> 6032 Example 64-1.94> 60 31 Example 65-1.35> 60 41 Example 66-1.8 4> 60 32

[Table 7] Reduction of running durability still life output Tape still life Initial still life Still life after storage (dB) (Minutes) (Minutes) Example 67-1.55> 6049 Example 68-1.34> 6052 Example 69-1.65>60> 60 Example 70-1.44>60> 60 Example Example 71-1.15>60> 60 Example 72-1.35>60> 60 Example 73-1.15>60> 60 Example 74-1.25>60> 60 Example 75 -1.7 4>60> 60 Example 76 -1.25>60> 60 Example 77 -1.9 4>60> 60

[Table 8] Decrease in running durability still life output Tape still life Initial still life Still life after storage (dB) (Minutes) (Minutes) Example 78-1.95>60> 60 Example 79-1.55>60> 60 Example 80-2.34> 6028 Example 81-1.25> 6045 Example Example 82-0.85> 6052

[Table 9] Reduction of running durability still life output Tape still life Initial still life Still life after storage (dB) (Minutes) (Minutes) Comparative example 1-6.4 17 1 Comparative example 2-7.2 19 9 Comparative example 3-2.5 4 21 3 Comparative example 4-2.3 4 26 9 Comparative example 5-4.1 233 11 Comparative Example 6 -2.9 3 316 Comparative Example 7 -3.5 344 7 Comparative Example 8 -3.1 245 15

As is clear from Tables 1 to 9, in comparison with Comparative Examples 1 to 8, the output reduction of Examples 1 to 82 was small, and no problem of tape damage occurred. The post-still lifes were all good.

In Examples 1 to 68, Comparative Examples 1 and 2 using a conventional lubricant and general formula (a)
As compared with Comparative Examples 3 to 5 in which the lubricant layers were formed only with the compounds shown in (c) and (g), all exhibited excellent running durability and still life. Thus, on the carbon film (3), at least one compound selected from the compounds represented by the general formulas (a) and (b) and at least one compound selected from the compounds represented by the general formula (c) Each of the magnetic tape samples of Examples 1 to 68 in which the lubricant layer (4) was formed of a lubricant composition containing one compound was excellent in practical reliability such as running durability and still life. It is clear that there is.

The magnetic tape samples of Examples 69 to 79 each containing a lubricant composition further mixed with an organic phosphorus compound are also excellent in practical reliability such as running durability and still life. . As is clear from the fact that the still life after storage has been improved, those containing an organic phosphorus compound have particularly improved still life. Although not particularly shown in Table 7, it was recognized that the initial still life of the magnetic tapes of Examples 69 to 79 was significantly improved as compared with those not containing an organic phosphorus compound. .

The magnetic tape sample of Example 80 uses the same lubricant composition as in Example 1, but does not form a nitrogen-containing plasma polymerized film on the carbon film (3).
The running durability and still life of Example 80 are slightly inferior to those of Example 1. This indicates that the nitrogen-containing plasma polymerized film contributes to the improvement of the lubrication performance of the magnetic tape.

From Example 1 and Comparative Examples 6 and 7, the coating liquid prepared by dissolving the lubricant composition of the lubricant layer (4) in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent was used to prepare a carbon film. (3) It can be seen that a magnetic tape sample excellent in practical reliability such as running durability and still life can be stably manufactured by forming a lubricant layer (4) by coating on the lubricant tape. Further, Comparative Example 8 in which the coating liquid containing the lubricant composition was applied under high humidity was inferior in both running durability and still life despite using the same lubricant composition as in Example 1. Shows that application under high humidity is undesirable.

In Examples 1 to 82, the reverse roll coating method, which is a wet coating method, was used in the step of forming the lubricant layer (4), but the same effect can be obtained by the organic vapor deposition method. (4) can be formed.

In Examples 1 to 82 described above, the magnetic recording medium of the present invention and the method of manufacturing the same were manufactured using commercially available 8 mm VT.
Although the description has been given only of the case where the present invention is applied to the R tape, the magnetic recording medium of the present invention and the method of manufacturing the same are not limited to this, and can be applied to other metal thin film magnetic tapes and magnetic disks. Things.

[0087]

As described above, the lubricant composition of the present invention in which two or more specific fluorine-containing compounds are combined exhibits excellent lubrication performance. Then, by forming a lubricant layer with this lubricant composition, it is possible to obtain a magnetic recording medium of the present invention in which the adhesion strength of the lubricant layer to the carbon film is improved and which exhibits good lubrication performance. By the synergistic effect, the magnetic recording medium of the present invention has improved practical reliability such as running durability and still durability without deteriorating the electromagnetic conversion characteristics.

Further, by further adding an organic phosphorus compound to the lubricant composition, the adhesion strength of the lubricant layer to the carbon film in the magnetic recording medium is further improved, and the magnetic recording medium exhibits more excellent lubricating performance. Can be obtained. Due to these synergistic effects, the magnetic recording medium of the present invention has improved practical reliability such as running durability and still durability without deteriorating the electromagnetic conversion characteristics.

In the magnetic recording medium of the present invention, by forming a nitrogen-containing plasma polymerized film on the surface layer of the carbon film, the chemical adsorption of the lubricant composition is improved, so that the lubricant layer adheres to the carbon film. It is possible to obtain a magnetic recording medium with further improved strength and excellent lubrication performance. By these synergistic effects, the magnetic recording medium of the present invention improves practical reliability such as running durability and still durability without impairing the electromagnetic conversion characteristics.

The magnetic recording medium of the present invention has a manufacturing method including a step of coating a coating solution prepared by dissolving a composition of a lubricant layer in a specific solvent on a carbon film under a specific humidity condition. Manufactured. By using this coating liquid, a lubricant layer having a uniform thickness without coating unevenness can be obtained. Further, by limiting the range of the humidity, deterioration of the performance of the lubricant layer is prevented. Therefore, according to the production method of the present invention, it is possible to stably produce the magnetic recording medium of the present invention which is excellent in practical reliability such as running durability and still life.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a metal thin-film magnetic tape to which a magnetic recording medium according to an embodiment of the present invention has been applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-magnetic substrate 2 Ferromagnetic metal thin film 3 Carbon film 4 Lubricant layer 5 Back coat layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C10N 30:06 40:18 (72) Inventor Tetsuo Fuchi 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F term (reference) 4H006 AA03 AB60 BM10 BM71 BS10 4H104 BD07A BH03C BH06C LA20 PA16 5D006 AA01 AA02 AA03 AA06 BB01 FA02 FA05 5D112 AA05 AA07 AA11 AA22 BC02 BC05 BC08 BC10 FA07 GA05

Claims (8)

[Claims] 1. General formulas (a) and (b) having a perfluoroalkyl group or a perfluoropolyether group and an alkyl group or an alkenyl group in the molecule: (Wherein, R ¹ is an alkyl group or an alkenyl group;
R ² is a perfluoroalkyl group or a perfluoropolyether group, a is an integer of 0 to 20, and b is 0
Or 1. ) (Wherein R ³ is an alkyl group or an alkenyl group;
R ⁴ is a perfluoroalkyl group or a perfluoropolyether group; R ⁵ is O or S;
An integer of 20; d is 0 or 1; And at least one compound selected from the compounds represented by the general formula (c) having a perfluoroalkyl group or a perfluoropolyether group and an alkyl group or an alkenyl group in the molecule. (Wherein, R ⁶ is an alkyl group or an alkenyl group;
R ⁷ is a perfluoroalkyl group or a perfluoropolyether group; R ⁸ is O or S;
To 20 and f is 0 or 1, and
R ⁹ , R ¹⁰ and R ¹¹ may be the same or different from each other, and are either a hydrocarbon group or hydrogen, and the hydrocarbon group has 1 to 20 carbon atoms. A) a lubricant composition comprising at least one compound selected from the group consisting of: 2. The method of claim 1, wherein the perfluoropolyether groups are of the general formulas (d), (e) and (f): (In the formula, q is an integer of 1 or more.) (Wherein, r, and t is an integer of 1 or more.) Embedded image _{^{R 12 (OC u F 2u)}} v O (CF 2) u-1 - ... (f) ( wherein, R ¹² Is a perfluoroalkyl group, and u is 1
And v is an integer of 1 to 30. 2. The method according to claim 1, wherein
The lubricant composition according to any one of the preceding claims. 3. The lubricant composition according to claim 1, further comprising an organic phosphorus compound. 4. An organophosphorus compound represented by the general formula (g):
(H) (i) (j) (k) (l) (m) (n) and (o): HP (O) (OC _n H _{2n + 1} ) ₂ ... (G) of 8] _{P (OC n H 2n + 1} ) 3 ... (h) [Omitted] _{P (SC n H 2n + 1} ) 3 ... (i) [of 10] O = P (OC _n H _{2n + 1) 3 ... (j} ) embedded image _{S = P (OC n H 2n} + 1) 3 ... (k) embedded image _{O = P (SC n H 2n} + 1) 3. .. (l) S = P (SC _n H _{2n + 1} ) ₃ ... (M) (C _n H _{2n + 1} O) ₂ P (O) OH. n) embedded image (C _n H _{2n + 1} O) P (O) (OH) ₂ ... (o) (in the above general formulas (g) to (o), n is 8 to 20)
Is an integer. 4. The lubricant composition according to claim 3, which is at least one organic phosphorus compound selected from the group consisting of the organic phosphorus compounds represented by the formula (1). 5. A magnetic recording medium in which a ferromagnetic metal thin film, a carbon film and a lubricant layer are formed in this order on a non-magnetic substrate, wherein the lubricant layer is any one of claims 1 to 4. 7. A magnetic recording medium comprising the lubricant composition according to item 1. 6. The magnetic material according to claim 5, wherein the carbon film has a nitrogen-containing plasma polymerized film on a surface portion thereof, and the lubricant layer is formed on the nitrogen-containing plasma polymerized film of the carbon film. recoding media. 7. The method for manufacturing a magnetic recording medium according to claim 5, wherein the step of forming a lubricant layer comprises:
A step of applying a coating solution prepared by dissolving a lubricant composition in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent on a carbon film in an environment where the relative humidity is in the range of 10 to 40%. A method for manufacturing a magnetic recording medium, comprising: 8. The method according to claim 7, wherein the mixing ratio of the hydrocarbon solvent and the alcohol solvent is in the range of 1: 9 to 9: 1 by weight.