JP2001207182A - Lubricant composition, magnetic recording medium and method for producing magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lubricant composition having excellent lubrication properties, and further to provide a magnetic recording medium having improved traveling durability or the like without damaging electromagnetic transducing characteristics. SOLUTION: This lubricant composition contains (I) at least one compound selected from fluorine-containing monocarboxylic acids having a perfluoroalkyl group or a perfluoro polyether group, and an alkyl group or an alkenyl group in the molecule, (II) at least one compound selected from perfluoro polyether- based compounds having polar groups at both terminals of the molecule, and (III) at least one compound selected from fluorocarboxylic acid esters having a fluorine-containing organic group in the molecule. The lubricant composition forms a lubricant layer (4) of a magnetic recording medium obtained by forming a ferromagnetic metal thin film (2), a carbon film (3) and the lubricant layer (4) in order on one surface of a paramagnetic substrate (1), and further forming a backcoat layer (5) on the other surface.

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, high-density magnetic recording media suitable for such digital recording and reproducing apparatuses have been developed with high performance such as digitization, miniaturization, and long use time. It has been actively carried out and has recently become an extremely advantageous alternative to coating type magnetic recording media for short wavelength recording.
Metal thin film magnetic recording media have been put to practical use. In general,
The 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 non-magnetic 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 has a great effect on running durability or still durability of the magnetic recording medium, and reducing it has been 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 has a lubricating property 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 to achieve high output. It is required to demonstrate. Therefore, the use of fluorine-based compounds exhibiting excellent lubrication properties has been widely studied, and the use of various compounds has been proposed. As such a compound, for example, the chemical formula (x1):

Embedded image Fluorinated long-chain carboxylic acid ester represented by
-46431) or a chemical formula (x2):

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 weather storage stability are desired. The storability is determined by the degree of deterioration of various performances such as running durability after being left for a long time, and when "weather resistance" storability is good, it can be determined in any environment including severe conditions such as high temperature and high humidity. It means that a decrease in running durability or the like is small even after being left for a long time under the conditions.

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 weather resistance and has high practical reliability without impairing the electromagnetic conversion characteristics. It is another object of the present invention to provide a magnetic recording medium using the lubricant composition and a method for manufacturing the same.

[0007]

In order to solve the above-mentioned problems, the present invention provides a compound represented by the following general formula (a) having a perfluoroalkyl group or a perfluoropolyether group and an alkyl group or an alkenyl group in the molecule. ) And at least one compound selected from the compounds represented by (b); II) a compound having a perfluoropolyether chain in the molecule and represented by the general formulas (c), (d) and (e); III) a lubricant composition comprising at least one compound selected from; and III) at least one compound selected from the compounds represented by formula (f):

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

Embedded image (Wherein, R ³ represents an alkyl group or an alkenyl group;
R ⁴ represents a perfluoroalkyl group or a perfluoropolyether group, R ⁵ represents —O— or —S—,
c is an integer of 0 to 20; d is 0 or 1)

Embedded image (Wherein, e and g are integers of 1 or more)

Embedded image (Where i and j are integers of 1 or more)

Embedded image (Where k and m are integers of 1 or more, and R ⁶ has 4 carbon atoms.
~ 22 alkyl groups)

Embedded image (Wherein R ⁷ represents a fluorine-containing organic group, R ⁸ represents an alkyl group or an alkenyl group, and n is an integer of 0 to 12).

[0008] The lubricant composition of the present invention comprises three or more specific fluorine-containing compounds, and has a general formula (a) to (f).
Are all fluorine-containing compounds. This lubricant composition comprises: I) at least one compound selected from fluorinated monocarboxylic acids represented by the general formulas (a) and (b); II) perfluoropolyether having polar groups bonded to both terminals A perfluoropolyether compound having hydroxyl groups bonded to both terminals represented by the general formula (c), a perfluoropolyether compound having carboxyl groups bonded to both terminals represented by the general formula (d), And at least one compound selected from perfluoropolyether compounds having acyloxyl groups bonded to both terminals represented by the general formula (e); and III) a fluorinated carboxylic acid ester represented by the general formula (f) Can be said to comprise at least one compound selected from The compound represented by the general formula (a)
It can also be said to be a fluorinated carboxylic acid monoester having one carboxyl group.

This lubricant composition is, for example, 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 (this is simply called a metal thin film type magnetic recording medium). In some cases), the adhesive strength to the carbon film located below the lubricant layer is improved, and excellent lubricating properties are imparted to the magnetic recording medium. Due to these synergistic effects, the magnetic recording medium has improved running durability and weather-preservability without impairing the electromagnetic conversion characteristics, and has extremely low scattering of the lubricant during use. can get.

According to another aspect of the present invention, a ferromagnetic metal thin film is provided on a nonmagnetic substrate, and a lubricant layer is provided on the ferromagnetic metal thin film via a carbon film. A magnetic recording medium is provided, wherein the lubricant layer contains the lubricant composition of the present invention. By using a lubricant composition in which three or more of the above-mentioned specific fluorine-containing compounds are combined, the adhesion strength to a carbon film located below the lubricant layer is improved, and excellent lubricating properties are imparted to the magnetic recording medium. Is done. And by these synergistic effects, it has improved running durability and weather storage stability without impairing the electromagnetic conversion characteristics,
A practically reliable magnetic recording medium with very little scattering of the lubricant during use can be obtained.

In a preferred embodiment of the magnetic recording medium according to the present invention, 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. Amino groups are present in the surface layer of the carbon film by the nitrogen-containing plasma polymerization, and as a result, the adhesion strength between the lubricant layer and the carbon film is increased, and the durability of the magnetic recording medium is further improved. Become. And, combined with the inclusion of a specific fluorine-containing compound or the like in the lubricant layer, the running durability and the weather storage stability have been improved with excellent lubrication characteristics without impairing the electromagnetic conversion characteristics. A high magnetic recording medium can be obtained.

Further, the present invention provides a method for manufacturing the magnetic recording medium of the present invention. The method for manufacturing a magnetic recording medium according to the present invention is characterized in 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%, and a step of drying the mixed organic solvent.

By applying a coating liquid containing a lubricant composition under a specific humidity condition 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 increased. And 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 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.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The fluorine-containing compound contained in the lubricant composition of the present invention is a compound represented by any of the general formulas (a) to (f). General formula (a):

Embedded image Can be said to be a fluorine-containing carboxylic acid monoester having one carboxyl group. This compound is 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.

In formula (a), R ¹ has 6 to 6 carbon atoms.
It is preferably 30 and more preferably 10 to 24. When the number of carbon atoms is less than 6 or more than 30, the lubricity may decrease. R ¹ may be linear or branched.

When R ² is a perfluoroalkyl group, it preferably has 6 to 12 carbon atoms,
More preferably, it is 10. R ² may be linear or branched. When R ² is a perfluoropolyether group, its molecular weight is about 20
It is preferably about 0 to about 6000, and about 300 to
More preferably, it is about 4000. Molecular weight 200
If it is less than 6000 or more than 6000, the lubricity and storage reliability may decrease.

When R ² is a perfluoropolyether group, the perfluoropolyether group is preferably one represented by any of the following formulas (g), (h) and (i). . When the compound having the following perfluoropolyether group is contained in the lubricant composition, for example, when the composition is contained in the lubricant layer of the metal thin-film magnetic recording medium, the carbon film of the lubricant layer The adhesion strength to the magnetic recording medium is further improved, and more excellent lubricating properties are imparted to the magnetic recording medium. And due to these synergistic effects,
It is possible to obtain a magnetic recording medium having improved running durability and weather storage stability without impairing the electromagnetic conversion characteristics, and having very little scattering of the lubricant during use, and having high practical reliability.

General formula (g):

Embedded image In the above, q is an integer of 1 or more.

General formula (h):

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

Formula (i):

Embedded imageIn, R⁹Represents a perfluoroalkyl group, and u represents
V is an integer of 1 to 30; v
Is more preferably 1 to 8. R⁹Has 1 carbon atom
Is preferably from 30 to 30, more preferably from 1 to 8.
preferable. Also, R ⁹Is branched even if it is linear
May be done.

When q, r, t, u and v in the general formulas (g), (h) and (i) are out of the above ranges,
For example, when this composition is contained in a lubricant layer of a magnetic recording medium, the lubricity and storage reliability of the magnetic recording medium may be reduced. Further, the carbon number of q, r, t, u and v and R ⁹ is such that the molecular weight of the perfluoropolyether group is in the above-mentioned preferred range, that is, about 200 to about 6
It is preferable to select appropriately so that it is in the range of about 000, more preferably in the range of about 300 to about 4000.

General formula (b):

Embedded image In the compound represented by, 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
It is.

The carbon number of R ³ in the general formula (b) is 6 to
It is preferably 30 and more preferably 10 to 24. When the number of carbon atoms is less than 6 or more than 30, the lubricity may decrease. R ³ may be linear or branched.

When R ⁴ is a perfluoroalkyl group, it preferably has 1 to 12 carbon atoms,
More preferably, it is 10. R ⁴ may be linear or branched. When R ⁴ is a perfluoropolyether group, its molecular weight is about 20
It is preferably about 0 to about 6000, and about 300 to
More preferably, it is about 4000. Molecular weight 200
If it is less than 6000 or more than 6000, the lubricity and storage reliability may decrease.

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

Next, the lubricant composition of the present invention contains
A perfluoropolyether compound having polar groups at both ends will be described.

General formula (c):

Embedded image The compound represented by has hydroxyl groups at both ends of the molecule.

In the general formula (c), each of e and g is an integer of 1 or more. Further, e and g are perfluoropolyether chains in the molecule, that is, —CF ₂ O (C _{2
F 4 O) e (CF 2} O) g CF 2 - molecular weight, preferably from about 200 to about 6000 nm, more preferably about 300 to
It is selected to be in the range of 4000. Molecular weight 2
If it is less than 00 or more than 6000, lubricity and storage reliability may be reduced.

General formula (d):

Embedded image The compound represented by has carboxyl groups at both ends of the molecule.

In the general formula (d), i and j are each an integer of 1 or more. Further, i and j are perfluoropolyether chains in the molecule, that is, —CF ₂ O (C _{2
F 4 O) i (CF 2} O) j CF 2 - molecular weight, preferably from about 200 to about 6000 nm, more preferably about 300 to
It is selected to be in the range of 4000. The reason why the molecular weight in this range is preferable is as described above with respect to the general formula (c).

Formula (e):

Embedded image Has an acyloxyl group at both ends of the molecule.

In the general formula (e), k and m are each an integer of 1 or more. R ⁶ is an alkyl group having 4 to 22 carbon atoms, more preferably an alkyl group having 12 to 22 carbon atoms. R ⁶ may be linear or branched. k and m are perfluoropolyether chains in the molecule, that is, —CF ₂ O (C ₂ F ₄ O)
_{k (CF 2 O) m CF} 2 - molecular weight, preferably about 200
About 6000, more preferably about 300 to 4000
Are selected to be within the range. The reason why the molecular weight in this range is preferable is as described above with respect to the general formula (c).

The compounds represented by the general formulas (c), (d) and (e) include e and g in the general formula (c), i and j in the general formula (d), and k in the general formula (e). And m may be a conventionally known or commercially available perfluoropolyether compound or a compound obtained by subjecting it to a predetermined chemical reaction as long as the above conditions are satisfied. For example, as the compound represented by the general formula (c), Fombli manufactured by Ausimont
There is n Z DOL, and as a compound represented by the general formula (d), there is Fomblin Z DIAC manufactured by Ausimont. In addition, the compound represented by the general formula (e) is manufactured by Ausimont as described above.
It is obtained by subjecting Fomblin Z DOL to a carboxylic acid represented by R ⁶ COOH to undergo an esterification reaction.

Next, the fluorine-containing carboxylic acid ester represented by the general formula (f) will be described.

General formula (f):

Embedded image In the formula, R ⁷ represents a fluorine-containing organic group, R ⁸ represents an alkyl group or an alkenyl group, and n is an integer of 0 to 12.

The term "fluorine-containing organic group" as used herein refers to an organic group in which one or more hydrogen atoms have been replaced with fluorine atoms. R ⁷ is preferably a fluoroalkyl group, a fluoroalkenyl group, a fluoroether group, or a fluoropolyether group, and more preferably a perfluoroalkyl group, a perfluoroalkenyl group, a perfluoroether group, or a perfluoropoly group. It is an ether group. R ⁷ preferably has 4 to 14 carbon atoms,
It is more preferable that the number is from 12 to 12. R ⁷ may be linear or branched.

In the general formula (f), n is more preferably 1 to 6. Further, R ⁸ preferably has 8 to 22 carbon atoms, and more preferably 12 to 18 carbon atoms. R ⁸ may be linear or branched.

The lubricant composition of the present invention comprises Group I, ie,
At least one compound selected from the compounds represented by the general formulas (a) and (b); Group II, ie, at least one compound selected from the compounds represented by the general formulas (c), (d) and (e) And at least one compound selected from Group III, ie, the compound represented by the general formula (f). The mixing ratio of the three is preferably in the range of 1 to 7: 1 to 7: 1 to 7 (Group I: Group II: Group III) by molar ratio, and 2 to 5: 1 to 3 : More preferably in the range of 3 to 6.

If the proportion of the compound selected from each group in the lubricant composition is small, the following problems may occur when the lubricant composition of the present invention forms a lubricant layer of a magnetic recording medium. . If the proportion occupied by the compound selected from Group I is small, the lubrication performance may be reduced. II
If the proportion of the compound selected from the group is small, the adhesion strength of the lubricant layer to the carbon film may be reduced. II
If the proportion occupied by the compound selected from Group I is small, the lubricating performance may decrease, and the adhesive strength of the lubricant layer of the magnetic recording medium to the carbon film may decrease.

The lubricant composition of the present invention has the general formula (a)
Components other than the compound represented by (f), for example, a rust inhibitor,
Alternatively, it may contain a conventionally known lubricant. In that case, the proportion occupied by components other than the compounds represented by the general formulas (a) to (f) is preferably less than 20% by weight, more preferably less than 10% by weight, based on the total amount of the composition. .
If the content is 20% by weight or more, for example, when a lubricant layer of a magnetic recording medium is formed with this lubricant composition, good lubricating properties may not be imparted to the magnetic recording medium.

A magnetic recording medium according to a second aspect 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 on a nonmagnetic substrate in this order. The layer contains the lubricant composition of the present invention. Then, each layer constituting the magnetic recording medium of the present invention will be described together with its manufacturing method 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. In this magnetic tape, a ferromagnetic metal thin film (2), a carbon film (3) and a lubricant layer (4) are formed in this order on one surface of a non-magnetic substrate (1), and a back coat layer (4) is formed on the other surface. 5) is formed.
Therefore, the structure is such that 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. ing.

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 projections are formed, for example, by dispersing and fixing ultrafine particles made of an inorganic substance such as SiO ₂ or ZnO, or ultrafine particles made of an organic substance such as imide on the surface of the nonmagnetic substrate, or It is formed by molding a polymer material containing such fine particles into a film.

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. The material of the ferromagnetic metal thin film (2) is a ferromagnetic metal such as Co, Fe and Ni, and C
It is suitably selected from alloys such as o-Ni and Co-Cr. The ferromagnetic metal thin film is generally formed under an oxygen atmosphere, and thus the ferromagnetic metal thin film contains oxygen, for example, in the form of a ferromagnetic metal oxide. The thickness of the ferromagnetic metal thin film (2) is generally 50 nm to 300 nm.

The carbon film (3) has a Vickers hardness of about 2.
As high as 45 × 10 ⁴ N / mm ² (about 2500 kgf / mm ² ), damage of the magnetic tape is prevented together with the lubricant layer (4). In consideration of the balance between practical reliability and output, the thickness is preferably 10 nm to 20 nm. This carbon film (3) is formed by a plasma CVD method using only a hydrocarbon gas or 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 container, and the pressure in the container is set to 1.33 × 10 ⁻¹ to 1.33.
A discharge is generated inside the vacuum vessel while maintaining the pressure at × 10 ² Pa (0.001 to 1 Torr), a plasma of hydrocarbon gas is generated, and the carbon film (3) is deposited on the ferromagnetic metal thin film (2). Let it form. The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency can be determined experimentally. Further, by applying a voltage of 0 KV to -3 KV to the electrode arranged on the non-magnetic substrate (1) side, the hardness of the carbon film (3) can be increased, and the carbon film (3) and the ferromagnetic Adhesion with the metal thin film (2) can be improved. As 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 keep the temperature of the non-magnetic substrate (1) high. 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. The formation of the nitrogen-containing plasma polymerized film results in the presence of amino groups in the surface layer of the carbon film. As a result, the adhesive strength between the lubricant layer and the carbon film is increased, and the magnetic recording medium The durability is further improved. And, combined with the inclusion of a specific fluorine-containing compound in the lubricant layer, the running durability and the weather storage stability have been improved with excellent lubrication performance without impairing the electromagnetic conversion characteristics. A magnetic recording medium is obtained.

The nitrogen-containing plasma polymerized film is put in a vacuum vessel.
Propylamine, butylamine, ethylenediamine, pro
Such as pyrylenediamine or tetramethylenediamine
The min compound is gasified and introduced, and the pressure in the container is increased to 1.3.
3 × 10^-1~ 1.33 × 10 ^TwoPa (0.001 to 1 Tor
r), high-frequency discharge is generated inside the vacuum vessel.
Formed. To form a 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. Nitrogen containing
The thickness of the plasma polymerized film is suitably less than 3 nm.
Protective effect of carbon film when nitrogen-containing plasma polymerized film is thick
Fruits decrease. In addition, the nitrogen-containing plasma
A method for forming a polymer film is disclosed in U.S. Pat.
And No. 5,637,393.
The contents disclosed in these patents form a part of the present specification.
You.

The lubricant composition constituting the lubricant layer (4) is as described above. In the present invention, the amount of the lubricant composition of the present invention contained in the lubricant layer (4) is preferably 0.1 to 50 mg, and preferably 0.5 to 5 mg per 1 m ² of the surface of the lubricant layer. More preferably, there is. In order for such a small amount of the compound to be uniformly present in the lubricant layer, the lubricant layer of the magnetic recording medium of the present invention is desirably formed by the following method.

The lubricant layer (4) is formed on the non-magnetic substrate (1) using a conventional material and means.
After the carbon film (3) is formed in this order, it is formed on the carbon film (3). In the step of forming the lubricant layer (4), a lubricant containing the lubricant composition of the present invention is dissolved in a mixed organic solvent of a hydrocarbon-based solvent and an alcohol-based solvent to prepare a coating solution. A step of coating on the carbon film (3) in an environment within a range of 10 to 40%.

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. 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 selected so that the thickness of the lubricant layer (4) formed on the carbon film (3) after the evaporation of the solvent becomes a desired thickness. In general, a coating solution having a lubricant composition concentration of 100 ppm to 4000 ppm is applied at a concentration of 1 μm to
It is preferable to apply the coating so as to have a thickness of 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%, there is a problem that static electricity is easily generated, and equipment for creating an environment of such humidity is expensive. When the relative humidity exceeds 40%, there is a problem that coating unevenness is likely to occur.

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 bar coating method, a gravure coating method, a reverse roll coating method, a die coating method, a wet coating method such as a dip coating method or a spin coating method, or an organic vapor deposition method.

After the application of the coating solution, a drying treatment is performed to evaporate the organic solvent, whereby 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. Then, the thickness of the finally obtained lubricant layer is preferably about 3 to 5 nm. However, since there is an optimum range of the thickness of the lubricant layer depending on the composition of the lubricant, the thickness of the lubricant layer is not necessarily limited to this range.

As described above, a lubricant layer having a uniform thickness without coating unevenness can be obtained by forming a lubricant layer at a predetermined relative humidity using a specific mixed organic solvent, and the solvent can be used as a final solvent. After evaporation, a very thin lubricant layer of several nm can be formed. 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.

[0061]

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

Example 1 As a nonmagnetic substrate (1), protrusions having a width of 500 mm, a thickness of 6.3 μm, a height of 30 nm and a diameter of 200 nm were formed on a surface of 10 ⁵ to 10 ⁵ per 1 mm ^2.
Nine polyethylene terephthalate films were used. 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 (Co (80) -Ni (20) (mixed mole ratio in parentheses) is formed by oblique vacuum evaporation while introducing oxygen. 2) was formed.

Next, a methyl ethyl ketone / toluene / cyclohexanone solution having a solid content of 30% composed of polyurethane, nitrocellulose and carbon black is applied to the back surface of the non-magnetic substrate (1) by a reverse roll coater, and the thickness after drying is applied. A back coat layer (5) having a thickness of about 500 nm was formed.

Next, a plasma is formed on the ferromagnetic metal thin film (2).
A carbon film (3) having a thickness of 15 nm is formed by a CVD method.
Was. Hexane gas and argon gas in a vacuum vessel
Gas mixed at a ratio of 4: 1 (pressure ratio)
Total gas pressure 4.0 × 10 ¹Pa (0.3 Torr)
However, the frequency of 20KHz, the voltage of 1500V AC and 1
000V DC is superimposed and applied to the electrodes in the discharge tube
It formed by doing. In addition, the carbon film (3)
Introducing propylamine gas, 6.67 Pa (0.05 Torr)
r) High-frequency plasma treatment at 10 KHz while maintaining the pressure
To a thickness of 2.5 nm on the surface of the carbon film (3).
An oxygen plasma polymerized film was formed.

Next, a compound represented by the following chemical formula (a1), a compound represented by the chemical formula (c1) (Fomblin-Z-DOL, manufactured by Ausimont), and a compound represented by the chemical formula (f1) are mixed in a molar ratio. Is dissolved in a mixed organic solvent in which isopropyl alcohol and toluene are mixed at a weight ratio of 1: 1 so that the concentration becomes 1500 ppm. To prepare a coating solution. Then, apply this coating solution to 23
In a 30 ° C., 30% RH environment, the solution was applied to a thickness of 4 μm by a wet coating method using a reverse roll coater, and then dried. On final carbon film (3) is, 1 m ² per 4m
A 4 nm-thick lubricant layer (4) containing g of the lubricant composition was formed.

The tape material prepared as described above was cut into a 6.35 mm width by a slitter to prepare a 6.35 mm width magnetic tape sample (total thickness 7 μm, 60 minutes long).

[0067]

Embedded image

[0068]

Embedded image

[0069]

Embedded image

Examples 2 to 11 In Examples 2 to 6, the compounds represented by the chemical formulas (a2) to (a6) were used. In Examples 7 to 11, the compounds represented by the chemical formulas (b1) to (b) were used.
Using the compound represented by 5), the respective compounds, the compound represented by the chemical formula (c1), and the compound represented by the chemical formula (f1)
Magnetic tape samples were produced in the same manner as in Example 1 except that a lubricant composition in which the compound represented by the formula was mixed at a molar ratio of 1: 1: 1 was used.

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[0072]

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Embodiments 12 to 22 Embodiments 12 to
17, the compounds represented by the chemical formulas (a1) to (a6) are used.
Compounds represented by the following formulas (1) to (b5) are used, each of which is represented by the following chemical formula (d1) (Ausimont Fomblin-Z-DIAC), and the compound represented by the chemical formula (f1) With a molar ratio of 1:
Magnetic tape samples were prepared in the same manner as in Example 1 except that the lubricant composition was used in a ratio of 1: 1.

[0082]

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Embodiments 23 to 33 Embodiments 23 to 33
28, the compounds represented by the chemical formulas (a1) to (a6), and Examples 29 to 33, respectively, the chemical formula (b)
Using the compounds represented by 1) to (b5), the respective compounds, the compound represented by the following chemical formula (e1), and the compound represented by the following formula (f1) are mixed at a molar ratio of 1: 1: 1.
The magnetic tape samples were produced in the same manner as in Example 1 except that the lubricant composition was used in such a manner as to satisfy the following ratio.

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Embodiments 34 to 44 Embodiments 34 to 44
39, the compounds represented by the chemical formulas (a1) to (a6), and Examples 40 to 44, respectively, the chemical formula (b)
Using the compounds represented by 1) to (b5), the respective compounds, the compound represented by the chemical formula (e1), and the compound represented by the following chemical formula (f2) are mixed at a molar ratio of 1: 1: 1.
The magnetic tape samples were produced in the same manner as in Example 1 except that the lubricant composition was used in such a manner as to satisfy the following ratio.

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Example 45 A compound represented by the chemical formula (a1), a compound represented by the chemical formula (c1), and a compound represented by the chemical formula (f1) were adjusted to have a molar ratio of 3: 1: 1. Magnetic tape samples were prepared in the same manner as in Example 1 except that the blended lubricant composition was used.

Example 46 A compound represented by the chemical formula (a1), a compound represented by the chemical formula (c1), and a compound represented by the chemical formula (f1) were adjusted to have a molar ratio of 1: 3: 1. Magnetic tape samples were prepared in the same manner as in Example 1 except that the blended lubricant composition was used.

Example 47 A compound represented by the chemical formula (a1), a compound represented by the chemical formula (c1), and a compound represented by the chemical formula (f1) were adjusted to have a molar ratio of 1: 1: 3. Magnetic tape samples were prepared in the same manner as in Example 1 except that the blended lubricant composition was used.

Example 48 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 of the carbon film (3) was omitted.

(Example 49) 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 set to 8: 1.

Example 50 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 1: 8.

Comparative Example 1 The procedure of Example 1 was repeated except that only the compound represented by the chemical formula (x1), which was a known lubricant, was used instead of the three-component lubricant composition used in Example 1. Magnetic tape samples were prepared in the same manner as in Example 1.

Comparative Example 2 The procedure of Example 1 was repeated except that only the compound represented by the chemical formula (x2), which was a known lubricant, was used instead of the three-component lubricant composition used in Example 1. Magnetic tape samples were prepared in the same manner as in Example 1.

(Comparative Example 3) A method similar to that of Example 1 was used except that only the compound represented by the chemical formula (a1) was used instead of the three-component lubricant composition used in Example 1. Each magnetic tape sample was produced.

(Comparative Example 4) A method similar to that of Example 1 was used, except that only the compound represented by the chemical formula (c1) was used instead of the three-component lubricant composition used in Example 1. Each magnetic tape sample was produced.

(Comparative Example 5) A method similar to that of Example 1 was used, except that only the compound represented by the chemical formula (f1) was used instead of the three-component lubricant composition used in Example 1. Each magnetic tape sample was produced.

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 composed 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 consisting 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. Produced.

The magnetic tape samples having a width of 6.35 mm obtained in Examples 1 to 50 and Comparative Examples 1 to 8 were subjected to the following evaluation tests (1) and (2), respectively. Tables 1 to 6 show the results obtained in each test.

(1) Running durability test Commercially available digital VT modified for RF (high frequency) output measurement
R (Matsushita Electric Co., Ltd., NV-DJ1), each 6.3
A 5mm wide tape sample was placed in an environment of 5 ° C and 80% RH for 300 minutes.
The RF output change after performing the pass and repeating the reproduction for 300 hours was measured. Changes after the test compared to before the test are shown in decibels.

The tape damage is caused by the post on the tape surface,
Running scratches caused by the fixed drum, sliding scratches caused by the magnetic head, the rotating drum, and the like were visually observed and observed with a differential interference microscope, and evaluated on a five-point scale. 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.

In order to measure the residual amount of the lubricant on the tape sample surface after the running durability test, fluorine atoms were analyzed by X-ray photoelectron spectroscopy (XPS) before and after the running durability test, and before and after the test. The remaining amount was calculated from the ratio of the intensities.

(2) Weathering Storage Test In order to evaluate the weathering storage of each 6.35 mm wide tape sample, the sample was left in an environment of 40 ° C. and 80% RH for 30 days to perform a weathering storage test. .

The still life after storage was measured using a commercially available digital VTR (Made by Matsushita Electric Co., Ltd., NV-
It was measured in an environment of 3 ° C. and 5% RH using DJ1). The still life after storage was shown as the time from the initial stage until a decrease of 6 dB.

Further, under an environment of 40 ° C. and 80% RH, 30
After standing for days, using a commercial digital VTR (Matsushita Electric Co., Ltd., NV-DJ1) modified for RF output measurement,
Reproduction was repeated for 100 passes for 100 hours in an environment of 23 ° C. and 60% RH, and head clogging was measured from the RF output during reproduction. During this repetitive playback, the RF output is 6d
It is assumed that head clogging has occurred when the pressure has decreased by B or more, and the time obtained by summing the times when such a decrease has been measured is regarded as head clogging.

[0108]

[Table 1] Running durability test Weathering / storability test output decrease Output tape Lubricant remaining Still head after storage Example Example (dB) Damage amount (%) Life (min) Clogging (sec) 1 -0.95 95> 60 0 2 -1.1 5 93 530 30 -1.249 92 510.54 -0.85 97> 600 -0.75 98> 600 -1.34 94550 .57-1.1 598> 6008 -1.259292 509 -1.1597> 60010 -1.44 93534011 -1.559149 0. 5

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[Table 2] Running durability test Weathering / storability test output decrease Output tape Remaining after storage Still head Example Example (dB) Damage amount (%) Life (minutes) Clogging (seconds) 12 -1.25 5 95> 60 013-0.9597> 60014-1.1 5996>600.515-0.95994>60016-0.7598> 60017-1.1495 >600.518-0.7596>60019-0.85929252020-1.3597> 600.521-1.44499558022-1.3. 4 93 55 0.5

[0110]

[Table 3] Running durability test Weather resistance and storage stability test Output decrease Tape Lubricant remaining Still head after storage Example (dB) Damage amount (%) Life (min) Clogging (sec) 23-1.1 5 98> 60 024-0.9598>60025-1.159857070-1.0597>60027-0.6598>60028-1.25596> 600 0.529-0.9595>60030-1.4595>60031-1.0597> 60032-1.259696 533633-1.3595> 60 0.5

[0111]

Table 4 Running Durability Test Weathering Preservability Test Output Decrease Tape Lubricant Remaining Still Head After Storage Example Example (dB) Damage Amount (%) Life (minutes) Clogging (seconds) 34-1.15 91 52 0 35-0.9596>60036-1.4593555037-1.3598>60038-0.8598>60039-1.1598> 600. 540 -1.3 597> 60041 -0.9596> 6004 -1.24 94533043 -1.2599149044 -1.15 90470.5

[0112]

[Table 5] Running durability test, weather resistance, storage stability test, output drop Table tape Lubricant remaining Still head after storage Item Example (dB) Damage amount (%) Life (minutes) Clogging (seconds) 45-1.24 93 520 46-0.6598> 600.547-1.5595580.50.548-1.5490490.50.549-1.449492480.550-0.9 5 98> 600

[0113]

[Table 6] running durability test weathering preservability test output reduction Tefu ° lubricant remaining after storage still Head Bu th Comparative Example (dB) data Bu Meshi Bu amount (%) Life (min) jam (s) 1 -6.4 1 49 1 29 0.02-6.8 147 1 27.0 3-2.9 352 5 2.04-2.2 4 98 12 24.0 5-2.5 372 8 14.6.0 6 -3. 3 394 24 4.5 7 -2.7 4 95 22 3.0 8 -3.2 3 92 19 5.0

As is clear from Tables 1 to 6, in comparison with Comparative Examples 1 to 8, all of the magnetic tapes obtained in Examples 1 to 50 have a small output reduction and a low residual amount of lubricant. More (ie less splash of lubricant in use),
The tape had excellent characteristics that no problem of tape damage occurred, less clogging of the head during repeated running after storage, and good still life after storage.

The magnetic tapes of Examples 1 to 47 were made of Comparative Examples 1 and 2 using a conventional lubricant and a lubricant layer containing only the compound represented by the general formula (a1), (c1) or (f1). In all, as compared with Comparative Examples 3 to 5 in which was formed, excellent running durability and weather resistance storage stability were exhibited. Thus, on the carbon film (3), at least one compound selected from the compounds represented by the general formulas (a) and (b), and the compounds represented by the general formulas (c), (d) and (e) Examples 1 to 3 in which a lubricant layer (4) was formed from a lubricant composition comprising at least one compound selected from compounds and at least one compound selected from compounds represented by the general formula (f) Each of the 47 magnetic tape samples is clearly superior in practical reliability such as running durability and weather storage stability.

The magnetic tape sample of Example 48 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 weather resistance of Example 48 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 as a carbon film. (3) It can be seen that a magnetic tape sample excellent in practical reliability, such as running durability and weather storage stability, can be stably manufactured by forming a lubricant layer (4) by coating on the lubricant tape. In Comparative Example 8 in which the coating liquid containing the lubricant composition was applied under high humidity, the running durability and the weather resistance storage stability were obtained even though the same lubricant composition as in Example 1 was used. Are inferior, indicating that application under high humidity is undesirable.

In Examples 1 to 50, the reverse roll coating method, which is a wet coating method, was employed in the step of forming the lubricant layer (4), but the same effect can be obtained by the organic vapor deposition method. ) Can be formed.

In the above-described embodiments 1 to 50,
Although only the case where the magnetic recording medium of the present invention and the method of manufacturing the same are applied to a commercially available tape for a digital VTR has been described, the magnetic recording medium of the present invention and the method of manufacturing the same are not limited thereto. The present invention can be applied to a magnetic tape or a magnetic disk.

[0120]

As described above, the lubricant composition of the present invention comprising three or more specific fluorine-containing compounds exhibits excellent lubricating performance. Then, by forming a lubricant layer of a magnetic recording medium with this lubricant composition, an adhesion strength of the lubricant layer to the carbon film is improved, and a magnetic recording medium of the present invention exhibiting good lubrication performance is obtained. Can be. Accordingly, the magnetic recording medium of the present invention using the lubricant of the present invention as a lubricant layer has improved running durability and weather resistance preservation without impairing the electromagnetic conversion characteristics due to a synergistic effect of these, and A practically reliable magnetic recording medium with very little scattering of the lubricant during use can be obtained.

Further, by forming a nitrogen-containing plasma polymerized film on the surface layer of the carbon film in the magnetic recording medium of the present invention, the chemical adsorption power 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 has improved practical reliability such as running durability and weather resistance without impairing the electromagnetic conversion characteristics.

The magnetic recording medium of the present invention is manufactured by a manufacturing method including a step of applying a coating solution prepared by dissolving a lubricant layer composition in a specific solvent on a carbon film under specific humidity conditions. Is done. 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 weather storage stability.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a metal thin-film magnetic tape which is one embodiment of the magnetic recording medium of the present invention.

[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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G11B 5/725 G11B 5/725 5/84 5/84 B // C09D 5/23 C09D 5/23 171 / 00 171/00 C10N 30:00 C10N 30:00 ZE 40:18 40:18 50:02 50:02 (72) Inventor Tetsuo Fuchi 1006, Oazadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Hisayo Ohata 1006 Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Kiyoshi Obata 1006 Okadoma, Kazuma, Kazuma, Osaka Matsushita Electric Industrial Co., Ltd. LA20 PA16 QA08 4J038 DF011 GA03 GA06 GA12 JA01 JA16 KA06 NA09 PA07 PB11 PC01 5D006 AA01 AA02 AA06 5D112 AA07 AA11 BC01 BC02 BC05 CC01

Claims (7)

[Claims] 1. I) at least one compound selected from compounds represented by the general formulas (a) and (b) having a perfluoroalkyl group or a perfluoropolyether group and an alkyl group or an alkenyl group in a molecule. II) at least one compound selected from compounds represented by general formulas (c), (d) and (e) having a perfluoropolyether chain in the molecule; and III) a general formula (f) A lubricant composition comprising at least one compound selected from the compounds represented by the following formula: (Wherein, R ¹ represents an alkyl group or an alkenyl group;
R ² represents a perfluoroalkyl group or a perfluoropolyether group; a is an integer of 0 to 20;
Or 1) (Wherein, R ³ represents an alkyl group or an alkenyl group;
R ⁴ represents a perfluoroalkyl group or a perfluoropolyether group, R ⁵ represents —O— or —S—,
c is an integer of 0 to 20, and d is 0 or 1. (Wherein, e and g are integers of 1 or more). (Where i and j are integers of 1 or more) (Where k and m are integers of 1 or more, and R ⁶ has 4 carbon atoms.
To 22). (Wherein, R ⁷ represents a fluorine-containing organic group, R ⁸ represents an alkyl group or an alkenyl group, and n is an integer of 0 to 12). 2. In the compound represented by the general formula (f), R ⁷ is a fluoroalkyl group, a perfluoroalkyl group, a fluoroalkenyl group, a perfluoroalkenyl group, a fluoroether group, a perfluoroether group, or a fluoropolyether. The lubricant composition according to claim 1, which is a group or a perfluoropolyether group. 3. The compound represented by formula (a) or (b), wherein the perfluoropolyether group is represented by any one of formulas (g), (h) and (i): The lubricant composition according to claim 1 or claim 2: (In the formula, q is an integer of 1 or more.) (In the formula, r and t are integers of 1 or more.) (Wherein, R ⁹ represents a perfluoroalkyl group, and u represents 1)
And v is an integer of 1 to 30). 4. A magnetic recording medium comprising: a ferromagnetic metal thin film provided on a non-magnetic substrate; and a lubricant layer provided on the ferromagnetic metal thin film via a carbon film. A magnetic recording medium comprising the lubricant composition according to claim 1. 5. The magnetic material according to claim 4, 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. 6. The method for manufacturing a magnetic recording medium according to claim 4, wherein the step of forming the lubricant layer comprises adding a lubricant composition to the mixed organic solvent of a hydrocarbon solvent and an alcohol solvent. The coating solution prepared by dissolving
A method for producing a magnetic recording medium, comprising a step of applying the composition on a carbon film in an environment within a range of 0 to 40%. 7. The method according to claim 6, wherein a mixing ratio of the hydrocarbon solvent and the alcohol solvent is in a range of 1: 9 to 9: 1 by weight.