JP2003178421A - Recording medium and manufacturing method for recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a recording medium whose practical reliability of running durability, weather resistant preservability and the like are enhanced without damaging electromagnetic transducing characteristics. <P>SOLUTION: In the recording medium wherein a metal thin film or a metal oxide thin film (2), a protective film (3) and a lubricant layer (4) are formed in this order on one surface of a non-magnetic substrate (1) and a back coating layer (5) is formed on the other surface, the surface of the protective film (3) has ≥40 mN/m surface free energy and at least one compound selected from a first group consisting of compounds having ≥15 mN/m and <33 mN/m surface free energy and at least one compound selected from a group consisting of compounds having ≥30 mN/m and <50 mN/m surface free energy are incorporated into the lubricant layer (4) as lubricant. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a digital video tape recorder, a high definition video tape recorder,
And a recording medium such as a magnetic recording medium, an optical recording medium or a magneto-optical recording medium suitable for use in a data storage device of a computer, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, in the field of recording, a high density recording medium suitable for the recording and reproducing apparatus has been actively developed along with the performance improvement such as digitalization, downsizing and long usage time. Has been. Here, the recording medium includes, for example, a magnetic recording medium, an optical recording medium or a magneto-optical recording medium. Recently, a metal thin film type recording medium, which is extremely advantageous for short wavelength recording, has been put into practical use in place of the coating type recording medium. Generally, a metal thin film type recording medium refers to a tape, a disc, or the like in which a recording layer composed of a metal thin film or a metal oxide thin film (or a metal oxide thin film) is provided as a recording layer on one surface of a non-magnetic support. Adapted for recording media having a lubricant layer.

The recording layer of this metal thin film type recording medium has an extremely good surface property, that is, since the surface roughness of the recording layer is small, the contact area with the magnetic head is increased, so that recording / reproducing of signals is performed. During the process, it is likely to be worn due to a large frictional force during high-speed sliding with the magnetic head. Since the abrasion of the recording layer has a great influence on the running durability or still durability of the recording medium, reducing it is a major issue in the research and development of the metal thin film type recording medium.

Therefore, attempts have been made to reduce wear and improve running durability and still durability by providing a lubricant layer on the surface of the recording layer. When a lubricant layer is provided, the lubricant layer on the surface of the recording layer exhibits lubricating characteristics with a thickness of only a few nanometers in order to minimize output reduction due to spacing loss between the recording medium and the magnetic head to achieve high output. Is required to do. Therefore, it has been widely studied to use a fluorine-based compound exhibiting excellent lubricating properties, and use of various compounds has been proposed. As such a compound, for example, the chemical formula (x1):

[Chemical 6] Fluorine-containing long-chain carboxylic acid ester represented by
-46431) and the chemical formula (x2):

[Chemical 7] It has been proposed to use a fluorine-containing carboxylic acid monoester having a carboxyl group represented by (see JP-A-61-107529).

[0005]

[Patent Document 1] JP-A-62-46431

[Patent Document 2] Japanese Patent Laid-Open No. 61-107529

[0006]

However, the demands for improving the performance of the recording medium are strict, and it is difficult to obtain sufficient lubrication characteristics with the above-mentioned conventional lubricants, and it is more difficult to obtain running durability and weather resistance storage stability. Improvement is desired. It should be noted that the storability is judged by the degree of deterioration in the various performances after the recording medium is left with respect to the various performances before the storage (for example, running durability) when the recording medium is left for a long time, and it is said that the “weather resistance” storage stability is good. Sometimes, it means that the deterioration of running durability is small even after being left for a long time under all environmental conditions including severe conditions such as high temperature and high humidity.

The present invention has been made in view of the above circumstances, and provides a recording medium which is excellent in running durability and weather resistance and has high practical reliability without impairing electromagnetic conversion characteristics, and a manufacturing method thereof. This is an issue.

[0008]

In order to solve the above problems, the present invention provides a metal thin film or a metal oxide thin film formed on one surface of a non-magnetic support, or a metal thin film or a metal oxide thin film. A recording medium having a protective film and a lubricant layer formed on the protective film, wherein the surface free energy of the surface of the protective film is 40 mN / m or more, and the lubricant layer has a surface free energy of 15 mN. / M or more 33m
At least one compound selected from the first group consisting of compounds in the range of less than N / m and a second group consisting of compounds having a surface free energy in the range of 33 mN / m to 50 mN / m. There is provided a recording medium containing a lubricant containing at least one kind of compound. still,
The term "metal oxide thin film" is used to mean "metal oxide thin film (ie, metal oxide thin film)".

The present invention is characterized in that a protective film having a specific surface free energy and at least two kinds of compounds having a specific surface free energy are combined. Due to this feature, the adhesive strength between the protective film and the lubricant layer is further improved, and as a result, the recording medium of the present invention exhibits excellent durability and storability.

The surface free energy of a certain object is obtained from the contact angle of a droplet when an appropriate solvent is dropped on the surface of the object. The surface free energy is obtained by using a CA-V type automatic contact angle meter manufactured by Kyowa Interface Science Co., Ltd., for example.

In the present specification, the surface free energy of the surface of the protective film is represented by the value measured on the surface of the protective film formed on the recording medium. In addition, in the present specification, the surface free energy of the surface of the protective film is represented by a value measured immediately before forming the lubricant layer (specifically, within 180 minutes before forming the lubricant layer). The surface free energy of each compound constituting the lubricant layer is 8.0 mg / each of each compound on the surface of the protective film of the recording medium which actually forms the lubricant layer.
It is a value measured on the surface of a film coated so as to have m ² . The application of each compound to the protective film is carried out by preparing a coating solution in which each compound is dissolved in an appropriate solvent, applying this, and then drying the solvent. The surface free energy of each compound is measured in this way because the lubricant layer is so thin that it cannot completely cover the surface of the protective film in the actual recording medium. This is because even when a layer is formed, the surface free energy of the surface of the lubricant layer changes under the influence of the protective film located thereunder.

In the recording medium of the present invention, the surface free energy of the surface of the protective film is 40 mN / m or more. In view of the fact that the value of the surface free energy is a combination of two kinds of compounds having a specific surface free energy as described later, it is useful as a lubricant, a lubricant layer containing such a lubricant and a protective film It was selected to increase the adhesion strength between the two.

In the recording medium of the present invention, the lubricant layer is
At least one compound selected from the first group consisting of compounds having a surface free energy in the range of 15 mN / m or more and less than 33 mN / m (also simply referred to as “first group” in the present specification), and surface free energy Is 33 mN / m
Second compound consisting of a compound in the range of 50 mN / m or less
And a lubricant comprising at least one compound selected from the group (also referred to herein simply as "second group"). Surface free energy of 15mN / m or more and 33mN /
The compound in the range of less than m improves the running property of the recording medium when included in the lubricant layer of the recording medium, and is therefore preferably used. Surface free energy is 33mN / m
The compound in the range of 50 mN / m or more is preferably used because it improves the durability of the recording medium when it is contained in the lubricant layer of the recording medium. A compound having a surface free energy in the range of 33 mN / m or more and 50 mN / m or less has a surface free energy close to the surface free energy of the surface of the protective film, and thus strongly adheres to the protective film. Therefore, by using at least two kinds of compounds having different surface free energy in combination as a lubricant, excellent lubrication characteristics are imparted to the recording medium, and the adhesion strength between the lubricant layer and the protective film is improved. To do. As a result, it is possible to obtain a magnetic recording medium which has excellent running durability and weather resistance storage, and which has little scattering of the lubricant during use and has high practical reliability.

At least one compound selected from the first group is preferably at least one compound selected from fluorine-containing carboxylic acids. The fluorinated carboxylic acid refers to a carboxylic acid in which one or more hydrogen atoms in an organic group are substituted with a fluorine atom. The fluorinated carboxylic acid may have two or more carboxyl groups. The fluorinated carboxylic acid may contain an ester bond.

The fluorine-containing carboxylic acid constituting the first group is
Preferably, the following general formulas (a) to (c):

[Chemical 8] (In the formula, 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, and b is 0.
Or 1)

[Chemical 9] (In the formula, 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.)

[Chemical 10] (In the formula, i and j are integers of 1 or more).

At least one compound selected from the second group is preferably at least one compound selected from fluorine-containing carboxylic acid esters. The fluorinated carboxylic acid ester means a carboxylic acid ester in which one or more of the organic groups are substituted with a fluorine atom. The fluorinated carboxylic acid ester may have two or more ester bonds.

The fluorine-containing carboxylic acid ester constituting the second group is preferably the following general formulas (d) and (e):

[Chemical 11] (In the formula, R ⁶ represents a fluorine-containing organic group, R ⁷ represents an alkyl group or an alkenyl group, and n is an integer of 0 to 12)

[Chemical 12] (In the formula, k and m are integers of 1 or more, and R ⁸ has 4 carbon atoms.
To 22 alkyl groups).

In the lubricant layer of the recording medium of the present invention,
Generally, the proportion of the compound selected from the second group gradually decreases toward the surface of the lubricant layer. That is, the concentration of the compound having a surface free energy of 33 mN / m or more and 50 mN / m or less is highest on the surface in contact with the protective film and becomes smaller as the distance from the protective film increases.
This is because the surface free energy of the compound is closer to the surface free energy of the surface of the protective film, so that the compound is more easily adsorbed on the protective film. The lubricant layer having such a structure can be formed even when two kinds of compounds are uniformly mixed and applied on the protective film according to the method described later.

If the proportion of the compound selected from the second group gradually decreases toward the surface of the lubricant layer,
In the vicinity of the surface of the lubricant layer, the proportion of the compound selected from the first group is large. Therefore, the surface free energy of the surface of the lubricant layer is determined by the compound selected from the first group, and its value is also 15 mN / m or more 3
It is in the range of less than 3 mN / m. However, since the compound selected from the second group does not exist on the surface of the lubricant layer at all, the surface free energy of the surface of the lubricant layer is also affected by the surface free energy of the compound. Therefore, even if the lubricant layer contains a compound having a surface free energy of less than 20 mN / m, the surface free energy of the surface of the lubricant layer is generally 20 mN / m or more.
It is in the range of less than mN / m. Furthermore, the surface free energy of the surface of the lubricant layer is also affected by the proportion of each compound in the lubricant layer.

In the recording medium of the present invention, the lubricant layer is
80 at least one compound selected from the first group
A first lubricant layer containing a lubricant containing not less than wt%, and a second lubricant layer
A second lubricant layer containing a lubricant containing 80% by weight or more of at least one compound selected from the group, the second lubricant layer is formed on the protective film, and the first lubricant layer is the second lubricant layer. It is preferably formed on the lubricant layer.
In such a lubricant layer, the compound having a large surface free energy is exclusively contained in the second lubricant layer adjacent to the protective film, so that the adhesion strength between the lubricant layer and the protective film is further improved. In addition, since the compound having a small surface free energy is exclusively present on the surface of the lubricant layer, the lubricating property is improved and the moisture resistance is also improved.

In the recording medium of the present invention, the protective film preferably has a nitrogen-containing plasma polymerized film, and the surface of the nitrogen-containing plasma polymerized film forms the surface of the protective film. When the nitrogen-containing plasma polymerized film is formed, amino groups are present in the surface layer of the protective film, and the surface of the protective film is rendered hydrophilic. Therefore, by forming the nitrogen-containing plasma polymerized film, the surface free energy of the surface of the protective film can be easily set to 40 mN / m or more.

The present invention also provides a method for manufacturing the recording medium of the present invention. The method for producing a recording medium of the present invention is characterized by the step of forming a lubricant layer. The other manufacturing process may be a process conventionally used for manufacturing a recording medium.

When the lubricant layer is a single layer, in the step of forming the lubricant layer, a coating solution prepared by dissolving the lubricant in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent is used at a relative humidity of It includes a step of coating on the protective film and drying the mixed organic solvent under an environment in the range of 10 to 40%.

When the lubricant layer includes the first lubricant layer and the second lubricant layer, the step of forming the lubricant layer includes the step of forming the first lubricant layer and the second lubricant layer, and the second lubricant layer. A coating liquid prepared in the step of forming the agent layer by dissolving a lubricant containing 80% by weight or more of at least one compound selected from the second group in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent. Is applied to the protective film in an environment where the relative humidity is in the range of 10 to 40% and the mixed organic solvent is dried, and the step of forming the first lubricant layer includes a hydrocarbon-based solvent and an alcohol-based solvent. A coating liquid prepared by dissolving a lubricant containing 80% by weight or more of at least one compound selected from the first group in a mixed organic solvent with a solvent has a relative humidity of 1
It includes a step of coating the second lubricant layer under an environment in the range of 0 to 40% and drying the mixed organic solvent.

In any step of forming the lubricant layer,
It is characterized in that a coating liquid containing a lubricant is applied under a specific humidity condition by using a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent. Due to this feature, the adhesion strength between the lubricant layer and the protective film is improved, and it becomes possible to form a uniform thin lubricant layer with very little coating unevenness. Therefore, according to the manufacturing method of the present invention including the step of forming the lubricant layer, it is possible to obtain a recording medium having excellent lubrication performance and high practical reliability.

In the above production method of the present invention, the mixing ratio of the hydrocarbon solvent and the alcohol solvent is 1: by weight.
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 also advantageous in terms of cost.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of the present invention will be described below. In the present specification including the following description, the “surface” of each layer or film constituting the recording medium is a surface exposed when each layer or film is formed, that is, a non-magnetic support of each layer or film. It means the side far from. With respect to the structure of a recording medium, the term "on" of each layer or film constituting the recording medium means "on the surface far from the non-magnetic support" of each layer or film unless otherwise specified. . Therefore, for example, the phrase "on the protective film" means "at a position adjacent to the surface of the protective film remote from the non-magnetic support".

First, the protective film constituting the recording medium of the present invention will be described. As long as the surface free energy of the surface of the protective film is 40 mN / m or more, the material and the forming method are not particularly limited, and a carbide,
It may be carbon nitride, silicon oxide, silicon nitride, boron nitride, boron carbide, or boron-carbon-nitrogen system.

The protective film acts as a protective layer and prevents damage to the recording medium together with the lubricant layer. The protective film is, for example, a carbon film made of amorphous carbon, graphite carbon, or diamond carbon formed by a method such as plasma CVD using only a hydrocarbon gas or a mixed gas of a hydrocarbon gas and an inert gas. Alternatively, it is a carbon film formed by mixing and / or stacking those carbons. The carbon film has a Vickers hardness of about 2.45 × 10.
It is preferably ⁴ N / mm ² (about 2500 kgf / mm ² ). The thickness of the protective film is preferably 10 nm to 20 nm in consideration of the balance between practical reliability and output.

The protective film is formed on the metal thin film or the metal oxide thin film (or the metal oxide thin film) after forming the metal thin film or the metal oxide thin film (or the metal oxide thin film) on the non-magnetic support. . 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 inside the container is set to 1.33 × 10.
^{-1 to} 1.33 × 10 ² Pa (0.001 to ¹ Torr) is maintained and a discharge is generated inside the vacuum container to generate a hydrocarbon gas plasma, and the protective film is a metal thin film or a metal oxide thin film. Form on top. The discharge method may be either an external electrode method or an internal electrode method, and the discharge frequency can be experimentally determined. Further, by applying a voltage of 0 KV to -3 KV to the electrode arranged on the non-magnetic support side, the hardness of the protective film can be increased, and the adhesion between the protective film and the metal thin film or the metal oxide thin film can be improved. Can be improved. As hydrocarbon gas, methane, ethane,
Propane, butane, pentane, hexane, heptane, octane, benzene and the like can be used. Also,
Other carbon nitrides, silicon oxides, silicon nitrides, boron nitrides, boron carbides, and boron-carbon-nitrogen-based protective films can also be formed on metal thin films or metal oxide thin films by electron beam vapor deposition, sputtering, or ion plating. It is formed.

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

The surface free energy of the surface of the protective film is set to 40
In order to obtain mN / m or more, it is preferable to form a nitrogen-containing plasma polymerized film on the surface layer of the protective film. When the nitrogen-containing plasma polymerized film is formed, amino groups are present in the surface layer portion of the protective film, and as a result, the hydrophilicity of the surface of the protective film is increased and the surface free energy is increased.

In the nitrogen-containing plasma polymerized film, an amine compound such as propylamine, butylamine, ethylenediamine, propylenediamine or tetramethylenediamine is gasified and introduced into a vacuum container to expose the surface of the protective film to the gas of the amine compound, The pressure inside the container is 1.33 × 10 ^-1
˜1.33 × 10 ² Pa (0.001 to 1 Torr) is maintained, and high-frequency discharge is generated inside the vacuum container to form the electrode. The film thickness of the nitrogen-containing plasma polymerized film is preferably 0.5 to 3 nm. If it is less than 0.5 nm, it becomes difficult to set the surface free energy of the surface of the protective film to 40 mN / m. If it exceeds 3 nm, the protective effect of the protective film is lowered.
The method for forming the nitrogen-containing plasma polymerized film on the surface layer of the protective film is disclosed in U.S. Pat.Nos. 5,540,957 and 5,637,393, and the contents disclosed in these patents by this citation are the contents of the present specification. Make up a part.

The surface free energy of the surface of the protective film is set to 40
Another method of increasing the mN / m or more is, for example, a method of containing nitrogen in the protective film. In order to contain nitrogen in the protective film, it is preferable to form the protective film in an atmosphere in which nitrogen is introduced. Alternatively, the surface free energy of the surface of the protective film is also increased by leaving the protective film formed according to the above-mentioned conventional method in the air and adsorbing moisture in the air to dangling bonds or the like on the surface of the protective film. be able to. Therefore, the surface free energy of the surface of the protective film can be set to 40 mN / m or more by adjusting the time for which the protective film is left in the air after forming the protective film and before forming the lubricant layer. It is possible.

Next, the lubricant constituting the lubricant layer will be described. In the recording medium of the present invention, the lubricant constituting the lubricant layer is at least one compound selected from the first group consisting of compounds having a surface free energy in the range of 15 mN / m or more and less than 33 mN / m. , And at least one compound selected from the second group consisting of compounds having a surface free energy in the range of 33 mN / m or more and 50 mN / m or less.

At least one compound selected from the first group is preferably at least one compound selected from fluorine-containing carboxylic acids. At least one compound selected from the second group is preferably at least one compound selected from fluorine-containing carboxylic acid esters.

As described above, the at least one compound selected from the first group is more preferably at least one selected from the group consisting of the fluorine-containing carboxylic acids represented by the general formulas (a) to (c). It is a class of compounds. Further, the at least one compound selected from the second group is more preferably at least one compound selected from the group consisting of the fluorine-containing carboxylic acid esters represented by the general formulas (d) and (e). . The compounds represented by formulas (a) to (e) are described below.

First, the fluorinated carboxylic acids represented by the general formulas (a) to (c) will be described. General formula (a):

[Chemical 13] The compound represented by 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 ¹ in the general formula (a) has 6 to 6 carbon atoms.
It is preferably 30 and more preferably 10 to 24. If the carbon number 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, and 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 from 0 to about 6000, and from about 300 to about 4.
It is more preferably 000. If the molecular weight is less than 200 or more than 6000, the lubricity and storage reliability of the recording medium may decrease.

When R ² is a perfluoropolyether group, the perfluoropolyether group is preferably one represented by any of the following general formulas (f), (g) and (h). . By including the compound having the following perfluoropolyether group in the lubricant,
Better lubricating properties are imparted to the recording medium. Due to these synergistic effects, it is possible to obtain a recording medium that is excellent in running durability and weather resistance and has high practical reliability without impairing electromagnetic conversion characteristics.

General formula (f):

[Chemical 14] In, q is an integer of 1 or more.

General formula (g):

[Chemical 15] In, r and t are integers of 1 or more.

General formula (h):

[Chemical 16] Where R⁹Represents a perfluoroalkyl group, and u represents
It is an integer of 1 to 6 and v is an integer of 1 to 30. v
Is more preferably 1-8. R⁹Has 1 carbon
It is preferable that it is -30, and it is more preferable that it is 1-8.
preferable. Also, R ⁹Is branched, even if linear
It may be one.

When q, r, t, u and v in the general formulas (f), (g) and (h) are out of the above range,
The lubricity and storage reliability of the recording medium containing such a compound having a perfluoropolyether group in the lubricant layer may be reduced. Further, q, r, t, u and v and the carbon number of R ⁹ are such that the molecular weight of the perfluoropolyether group is in the above-mentioned preferred range, that is, about 200 to about 6.
000, more preferably about 300 to about 4000, preferably selected appropriately.

General formula (b):

[Chemical 17] 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 generally an integer of 0 to 20, preferably 1 to 10. d is 0 or 1
Is.

R ³ in the general formula (b) has 6 to 6 carbon atoms.
It is preferably 30 and more preferably 10 to 24. If the carbon number 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, and 6 to 6 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 from 0 to about 6000, and from about 300 to about 4.
It is more preferably 000. If the molecular weight is less than 200 or more than 6000, the lubricity and storage reliability of the recording medium may decrease.

When R ⁴ is a perfluoropolyether group, R ⁴ is represented by any of the above general formulas (f), (g) and (h), like R ² in the general formula (a). It is preferable that the group is The general formulas (f), (g) and (h) are as described above in relation to the general formula (a), and the detailed description thereof will be omitted here by citing the description.

General formula (c):

[Chemical 18] The compound represented by is a perfluoropolyether chain (-
CF ₂ O (C ₂ F ₄ O) _i (CF ₂ O) _j CF ₂ −) and 2
It is a carboxylic acid having two carboxyl groups. In the compound represented by the general formula (c), i and j are each an integer of 1 or more. In the compound represented by the general formula (c), the molecular weight of the perfluoropolyether chain is about 2
00 to about 6000 are preferable, and about 300 to about 4000 are more preferable. When the molecular weight of the perfluoropolyether chain is less than 200 or exceeds 6000, the lubricity and storage reliability of the recording medium deteriorate.

Next, the fluorine-containing carboxylic acid ester represented by the general formulas (d) and (e) will be described. General formula (d):

[Chemical 19] In the compound represented by, R ⁶ represents a fluorine-containing organic group, R ⁷ represents an alkyl group or an alkenyl group, and n is an integer of 0-12.

The term "fluorine-containing organic group" as used herein refers to an organic group in which one or more hydrogen atoms are substituted with fluorine atoms. R ⁶ is preferably a fluoroalkyl group, a fluoroalkenyl group, a fluoroether group, or a fluoropolyether group, more preferably a perfluoroalkyl group, a perfluoroalkenyl group, a perfluoroether group, or a perfluoropoly group. It is an ether group. The carbon number of R ⁶ is preferably 4 to 14,
More preferably, it is -12. R ⁶ may be linear or branched. In the general formula (d), n is more preferably 1-6.

The carbon number of R ⁷ is preferably 8 to 22, and more preferably 12 to 18. R ⁷ is
It may be linear or branched.

General formula (e):

[Chemical 20] In the compound represented by, k and m are each an integer of 1 or more, and R ⁸ is an alkyl group having 4 to 22 carbon atoms. In the compound represented by the general formula (e), a perfluoropolyether chain (—CF ₂ O (C ₂ F ₄ O) _k (CF
The molecular weight of ₂ O) _m CF _2- ) is preferably about 200 to about 6000, more preferably about 300 to about 4000. When the molecular weight is less than 200 or exceeds 6000, the lubricity and storage reliability of the recording medium deteriorate. The carbon number of R ⁸ in the general formula (e) is preferably 4 to 22,
12-22 is more preferable.

The compounds represented by the general formulas (a) to (e) are examples of the compounds preferably used in the present invention. It goes without saying that other compounds that have a surface free energy in the above-mentioned specific range and can be used as a lubricant may be used instead of or together with these.

As described above, the lubricant layer has at least one compound selected from the first group consisting of compounds having a surface free energy in the range of 15 mN / m or more and less than 33 mN / m and the surface free energy. At least one compound selected from the second group consisting of compounds in the range of 33 mN / m or more and 50 mN / m or less is contained as a lubricant. Two or more kinds of compounds selected from the first group may be contained in the lubricant layer. Similarly, two or more kinds of compounds selected from the second group may be included.

The proportion of the compound selected from the first group and the compound selected from the second group in the lubricant layer is preferably 1: 9 to 8: 2 (first group: second group) in molar ratio. ), More preferably in the range of 1: 9 to 5: 5. When two or more compounds selected from the first group are contained in the lubricant layer, the sum of the ratios of the respective compounds corresponds to the ratio of the compounds selected from the first group. The same applies when two or more compounds selected from the second group are contained.

This preferable ratio is independent of the structure of the lubricant layer (that is, a single layer structure in which all compounds are mixed, or a compound selected from the first group, as described later). Showing the preferable ratio of the compound selected from each group to the whole lubricant layer, regardless of the two-layer structure consisting of the layer exclusively containing and the layer exclusively containing the compound selected from the second group) There is. If the proportion of the compound selected from the first group is small, the lubricating performance may be deteriorated. When the proportion of the compound selected from the second group is small, the lubricating performance may be reduced, and the adhesion strength of the lubricant layer to the protective film and the covering property may be reduced.

Next, the structure of the lubricant layer of the recording medium of the present invention will be described. The lubricant layer may be a single layer formed by mixing at least one compound selected from the first group and at least one compound selected from the second group. However, as described above, in the finally obtained lubricant layer, each compound is not uniformly distributed. For example, when the lubricant layer is composed of one kind of compound selected from the first group and one kind of compound selected from the second group (that is, composed of two kinds of compounds), The proportion of the compound selected from the group tends to gradually decrease toward the surface of the lubricant layer. This is because the compound selected from the second group is easily adsorbed on the protective film. When the lubricant layer contains three or more kinds of compounds having different surface free energies, the compound having the surface free energy closest to the surface free energy of the surface of the protective film is most present near the surface of the protective film. The compound having the smallest surface free energy is most present near the surface of the lubricant layer.

The lubricant layer comprises a first lubricant layer containing a lubricant containing 80% by weight or more of at least one compound selected from the first group, and at least one compound selected from the second group. Second containing lubricant containing 80% by weight or more
It may include a lubricant layer, the second lubricant layer is formed on the protective film, and the first lubricant layer is formed on the second lubricant layer. The lubricant layer including the two layers is formed by separately forming the two layers as described below. The adhesion of the lubricant layer to the protective film is ensured by the second lubricant layer.

The first lubricant layer may contain two or more compounds selected from the first group. Similarly, the second lubricant layer may contain two or more compounds selected from the second group. In any case, the ratio of all the compounds selected from the first group and all the compounds selected from the second group in the entire lubricant layer is 1: 9 to 8: 2 in molar ratio as described above. Is preferred.

In another embodiment, the lubricant layer may include more than two lubricant layers. For example, three or more kinds of compounds having different surface free energies may be used, and each compound may form a lubricant layer. In that case, a layer made of a compound having the largest surface free energy and closest to the surface free energy of the surface of the protective film is adjacent to the protective film, and a layer made of a compound having the smallest surface free energy is formed on the surface of the lubricant layer. Each layer may be sequentially stacked so that the layers are positioned.

In the recording medium of the present invention, the lubricant layer is
Compounds whose surface free energy is not within the above range may be included. Such compounds are, for example, known lubricants and rust inhibitors. The proportion of such a compound in the whole lubricant layer is preferably not more than 20% by weight.

Next, the process of forming the lubricant layer will be described. The total amount of the compound selected from the first group and the compound selected from the second group contained in the lubricant layer is preferably 0.5 to 30 mg per 1 m ² of the surface of the lubricant layer,
More preferably, it is 5 to 15 mg. In order to make such a small amount of the compound evenly present in the lubricant layer, it is desirable to form the lubricant layer of the recording medium of the present invention by the method described below.

First, the compound selected from the first group and the second compound
Using a lubricant mixed with a compound selected from the group,
A method for forming a single lubricant layer will be described.

The lubricant layer is formed on the protective film after a metal thin film or a metal oxide thin film and a protective film are formed in this order on one surface of the non-magnetic support using conventional materials and means. In the step of forming the lubricant layer, the lubricant is dissolved in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent to prepare a coating solution, and the coating solution is prepared under an environment where the relative humidity is in the range of 10 to 40%. It includes a step of coating on the protective film. The lubricant soluble in an organic solvent has at least one compound selected from the first group consisting of compounds having a surface free energy of 15 mN / m or more and less than 33 mN / m, and a surface free energy of 33 mN / m or more. A mixture containing at least one compound selected from the second group consisting of compounds in the range of 50 mN / m or less, and further containing other components as necessary.

Hydrocarbon-based solvents that can be used in the present invention are, for example, toluene, hexane, heptane, octane and the like, and alcohol-based solvents that can be used in the present invention are, for example, methyl alcohol, ethyl alcohol, propyl alcohol and isopropyl alcohol. Is a lower alcohol of. Specifically, the mixed organic solvent is preferably a mixed solvent of toluene and isopropyl alcohol, a mixed solvent of hexane and isopropyl alcohol, or a mixed solvent of heptane and isopropyl alcohol. If the proportion of the alcohol solvent is too large, coating unevenness tends to occur, while if the proportion of the hydrocarbon solvent is too large, it is uneconomical. Therefore, the mixing ratio of both is 1: 9 to 9: 1 by weight.
The mixture is used in the range of, preferably in the range of 3: 7 to 7: 3. The concentration of the coating liquid and the coating thickness are selected so that the lubricant layer formed on the protective film after the solvent has evaporated has a desired thickness. Generally, a coating solution with a lubricant concentration of 100 ppm to 4000 ppm is
It is preferable to apply it so as to have a thickness of ˜50 μm.

The coating liquid is preferably applied in an environment where the relative humidity is in the range of 10 to 40%. Relative humidity is 1
If it is less than 0%, there is a problem that static electricity is likely to be generated, and that equipment for creating such a humidity environment is expensive. If the relative humidity exceeds 40%, uneven coating is likely to occur.

The optimum thickness of the lubricant layer is determined depending on the lubricant, and the thickness is generally 3 to 5 nm. As a coating method, 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 dipping method and a spin coating method, and an organic vapor deposition method may be adopted.

After applying the coating solution, a drying process is performed to evaporate the organic solvent, whereby a lubricant layer is formed on the protective film. The drying treatment can be carried out by heating or by natural drying. 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.

By applying the lubricant layer forming step described above, a lubricant layer having a first lubricant layer and a second lubricant layer can be formed. Such a lubricant layer is formed by forming the second lubricant layer on the protective film and then forming the first lubricant layer in the same manner as described above. The second lubricant layer is prepared by dissolving a lubricant (a lubricant containing at least one compound selected from the second group) constituting the second lubricant layer in a mixed organic solvent in the same manner as above to prepare a coating solution. Then, this is applied on the protective film and then dried. For the first lubricant layer, a coating liquid is prepared by dissolving a lubricant (a lubricant containing at least one compound selected from the first group) constituting the first lubricant layer in a mixed organic solvent in the same manner as above. Then, this is applied on the second lubricant layer and then dried. In the step of forming the first and second lubricant layers, coating and drying are carried out by the same method as described above.

When forming a lubricant layer composed of the first and second lubricant layers, the total thickness of the lubricant layer finally obtained should be a desired thickness (for example, 3 to 5 nm). The concentration of the coating liquid and the coating thickness for forming each layer are selected. Generally, each layer has a lubricant concentration of 100-300.
It is preferable that the coating liquid of 0 ppm is applied to form a thickness of 1 to 20 μm.

As described above, by forming a lubricant layer using a specific mixed organic solvent under a predetermined relative humidity, a lubricant layer having a uniform thickness without coating unevenness can be obtained, 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 recording medium having excellent lubrication performance and high practical reliability can be obtained.

In the recording medium of the present invention, the surface of the protective film is 40
As long as the lubricant layer has a surface free energy of mN / m or more, and the lubricant layer contains at least one compound selected from the first group and at least one compound selected from the second group, It can be configured. Hereinafter, the configuration of elements other than the protective film and the lubricant layer described above, that is, the nonmagnetic support, the recording layer, and the backcoat layer formed as necessary will be described with reference to the drawings.

FIG. 1 is a sectional view of a metal thin film type tape (hereinafter, simply referred to as a tape) which is one embodiment of the recording medium of the present invention. In this tape (10), a metal thin film or a metal oxide thin film (2), a protective film (3) and a lubricant layer (4) are formed in this order on one surface of a non-magnetic support (1), and the other surface is formed. The back coat layer (5) is formed on the back surface.
Therefore, the structure is such that the back coat layer (5), the non-magnetic support (1), the metal thin film or the metal oxide thin film (2), the protective film (3) and the lubricant layer (4) are laminated in this order from the bottom. It has a structure. FIG. 2 is a sectional view of a metal thin film type tape which is another embodiment of the recording medium of the present invention. Figure 2
In the recording medium of No. 1, the lubricant layer (4) is the first lubricant layer (4a).
And it is the same as that shown in FIG. 1 except that it is constituted by the second lubricant layer (4b).

The non-magnetic support (1), the metal thin film or the metal oxide thin film (2) and the back coat layer (5) can be formed by using a conventional material and forming method.

For example, as the non-magnetic support (1), polyethylene terephthalate, polyethylene naphthalate,
A film made of aromatic polyamide or aromatic polyimide, an aluminum substrate, a glass substrate, or the like can be used. In order to achieve both practical reliability and good RF output, the surface of the non-magnetic support (1), that is, the surface in contact with the metal thin film or the metal oxide thin film, has a diameter of 50 to 700 n.
It is preferable that a protrusion forming treatment with m and a height of 5 to 70 nm is performed. The protrusions are specifically, for example, SiO ₂ ,
It is formed by dispersing and fixing ultrafine particles made of an inorganic substance such as ZnO or ultrafine particles made of an organic substance such as imide on the surface of a non-magnetic support, or a polymer material containing such fine particles is formed into a film. It is formed by molding. Examples of the non-magnetic support having protrusions on its surface are disclosed in JP-A-9-164644 and JP-A-1.
No. 0-261215 and the like.

The recording layer (2) is preferably a metal thin film or a metal oxide thin film. The metal thin film or the metal oxide thin film can be formed by a conventional material and method.

Suitable metals and metal oxides for the recording layer are ferromagnetic recording materials such as Fe metal, Co metal, and Ni-based metal, TbFeCo, GdTbFe, GdTbF.
Magneto-optical recording materials such as eCo, GdDyFeCo, NdDyFeCo, GeTe, GeSbTe, InSbTe,
AgInSbTe, SbInSn, TeAsSe, Te
Phase change recording materials such as Se, SeInSb, AgZn, and the like, and cyanine dyes, phthalocyanine dyes, quinone dyes, squalium dyes, azurenium dyes, merocyanine dyes, azo dyes, naphthoquinone dyes, porphyrin dyes, oxonol dyes, azomethine dyes, It may be an organic dye recording material such as an anthraquinone dye, an indigo dye or a formazan dye.

Examples of the method for forming the recording layer include vapor deposition, sputtering, ion plating and plasma CVD, coating and the like.

The metal thin film or the metal oxide thin film can be formed by an ion plating method, a sputtering method, an electron beam evaporation method, a resistance heating method, or the like. When the metal thin film or the metal oxide thin film is formed in an oxygen atmosphere, the metal thin film or the metal oxide thin film contains oxygen in the form of, for example, an oxide of a ferromagnetic metal. The thickness of the metal thin film or the metal oxide thin film is generally 50 nm to 300 nm.

The back coat layer (5) is made of polyurethane,
It is a layer formed of one or more materials selected from nitrocellulose, polyester, carbon, calcium carbonate and the like. The thickness of the back coat layer (5) is preferably about 500 nm. The back coat layer is
For example, a coating solution prepared by dissolving and dispersing the above materials in a suitable solvent (for example, a mixed solvent of toluene and methyl ethyl ketone) is applied to the other surface of the non-magnetic support, that is, the surface opposite to the surface on which the recording layer is formed. After that, it can be formed by a wet coating method of drying and evaporating the solvent.

[0084]

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

(Example 1) As the non-magnetic support (1),
A wide 500 mm, a thickness of 4.6 .mu.m, a height on the surface 30 nm, in diameter is 200nm projections 1 mm ² per 10 ⁵ -
A polyethylene naphthalate film having 10 ⁹ formed was used. The number of protrusions is a value measured by STM analysis. A ferromagnetic metal thin film with a thickness of 180 nm consisting of Co (80) -Ni (20) (mixed atom% in parentheses) by the oblique vacuum deposition method while introducing oxygen on the surface of this non-magnetic support (1). (2) was formed.

Then, on the back surface of the non-magnetic support (1), methyl ethyl ketone / toluene / containing polyurethane, nitrocellulose and carbon black with a solid content of 30% was used.
The cyclohexanone solution was applied by a reverse roll coater to form a back coat layer (5) having a thickness after drying of about 500 nm.

Next, plasma is formed on the ferromagnetic metal thin film (2).
A 15 nm thick carbon film (3) is formed by the CVD method.
It was A carbon film is prepared by placing hexane gas and argon gas in a vacuum container.
Introducing a gas in which the gas and the gas are mixed at a ratio (pressure ratio) of 4: 1,
Total gas pressure 4.0 × 10 ¹Keep at Pa (0.3 Torr)
In the meanwhile, the frequency is 20KHz and the voltage is 1500V AC and 1
Superimpose DC of 000V and apply this to the electrode in the discharge tube
It was formed by doing. In addition, the carbon film (3)
Introducing ropylamine gas, 6.67Pa (0.05Tor
High frequency plasma treatment of 10KHz while maintaining the pressure of r)
The surface of the carbon film (3) with a thickness of 2.5 nm containing nitrogen.
An elementary plasma polymerized film was formed.

The surface free energy of the surface of the obtained carbon film (3) was measured immediately before the formation of the lubricant layer, and it was 53 mN / m. The surface free energy was calculated from the contact angles of three kinds of solvents (water, methylene iodide, α-bromonaphthalene) using a CA-V type automatic contact angle meter manufactured by Kyowa Interface Science Co., Ltd.

Next, a lubricant prepared by mixing a compound represented by the following chemical formula (a1) and a compound represented by the chemical formula (d1) in a molar ratio of 3: 7 was prepared by mixing isopropyl alcohol and toluene by weight. A coating solution was prepared by dissolving the mixture in a mixed organic solvent having a ratio of 1: 1 so that the concentration was 2000 ppm. Then, this coating solution was applied by a wet coating method using a reverse roll coater in an environment of 23 ° C. and 30% RH to a thickness of 4 μm, and then dried. Finally, on the carbon film (3), 1 m ²
A 4 nm thick lubricant layer (4) was formed, containing 5 mg of lubricant per.

The tape material produced as described above was cut with a slitter to a width of 6.35 mm to obtain a 6.35 mm-wide magnetic tape sample (total thickness 5.3 μm, 80 minutes long).

[0091]

[Chemical 21]

[0092]

[Chemical formula 22]

Examples 2 to 12 In Examples 2 to 6, compounds represented by chemical formulas (a2) to (a6) are used, and in Examples 7 to 11, chemical formulas (b1) to (b) are used.
In Example 12, the compound represented by the formula (5)
1), the respective compounds and the compound represented by the chemical formula (d1) are used in a molar ratio of 3: 7.
Magnetic tape samples were prepared in the same manner as in Example 1 except that the lubricants were mixed so as to have the following ratio.

[0094]

[Chemical formula 23]

[0095]

[Chemical formula 24]

[0096]

[Chemical 25]

[0097]

[Chemical formula 26]

[0098]

[Chemical 27]

[0099]

[Chemical 28]

[0100]

[Chemical 29]

[0101]

[Chemical 30]

[0102]

[Chemical 31]

[0103]

[Chemical 32]

[0104]

[Chemical 33]

(Examples 13 to 24) Example 13 to
In 18, the compounds represented by the chemical formulas (a1) to (a6) are used, and in Examples 19 to 23, the chemical formulas (b) are used.
1) to (b5), in Example 24, the compound represented by the chemical formula (c1) is used, and each compound and the compound represented by the following chemical formula (d2) are used in a molar ratio of 3: 7. Magnetic tape samples were prepared in the same manner as in Example 1 except that the lubricants were mixed so as to have the following ratio.

[0106]

[Chemical 34]

(Examples 25 to 36) Example 25 to
In Example 30, the compounds represented by the chemical formulas (a1) to (a6) are used, and in Examples 31 to 35, the chemical formulas (b) and
1) to (b5), in Example 36, the compound represented by the chemical formula (c1) is used, and each compound and the compound represented by the following chemical formula (e1) are used in a molar ratio of 3: 7. Magnetic tape samples were prepared in the same manner as in Example 1 except that the lubricants were mixed so as to have the following ratio.

[0108]

[Chemical 35]

Example 37 Except that a lubricant prepared by mixing a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (d1) in a molar ratio of 1: 9 was used. A magnetic tape sample was prepared in the same manner as in Example 1.

(Example 38) Except that a lubricant prepared by mixing a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (d1) in a molar ratio of 5: 5 was used. A magnetic tape sample was prepared in the same manner as in Example 1.

Example 39 Except that a lubricant prepared by mixing a compound represented by the chemical formula (a1) and a compound represented by the chemical formula (d1) in a molar ratio of 7: 3 was used. A magnetic tape sample was prepared in the same manner as in Example 1.

(Example 40) Except that a lubricant prepared by mixing the compound represented by the chemical formula (a1) and the compound represented by the chemical formula (d1) in a molar ratio of 8: 2 was used. A magnetic tape sample was prepared in the same manner as in Example 1.

(Example 41) Except that a lubricant prepared by mixing a compound represented by the chemical formula (b1) and a compound represented by the chemical formula (d1) in a molar ratio of 1: 9 was used. A magnetic tape sample was prepared in the same manner as in Example 1.

Example 42 Except that a lubricant prepared by mixing a compound represented by the chemical formula (b1) and a compound represented by the chemical formula (d1) in a molar ratio of 5: 5 was used. A magnetic tape sample was prepared in the same manner as in Example 1.

Example 43 Except that a lubricant prepared by mixing a compound represented by the chemical formula (b1) and a compound represented by the chemical formula (d1) in a molar ratio of 7: 3 was used. A magnetic tape sample was prepared in the same manner as in Example 1.

(Example 44) Except that a lubricant prepared by mixing a compound represented by the chemical formula (b1) and a compound represented by the chemical formula (d1) in a molar ratio of 8: 2 was used. A magnetic tape sample was prepared in the same manner as in Example 1.

Example 45 A magnetic recording medium having the structure shown in FIG. 2 was produced. The non-magnetic support (1) used is the same as that used in Example 1. The magnetic layer (2), the carbon film (3) and the back coat layer (5) were formed in the same manner as in Example 1. The lubricant layer (4) was formed as follows.

First, only the compound represented by the chemical formula (d1) was dissolved and applied in a mixed organic solvent in which isopropyl alcohol and toluene were mixed at a weight ratio of 1: 1 so as to have a concentration of 1200 ppm and applied. A liquid was prepared.
The coating solution was applied onto the carbon film (3) to have a thickness of 4 μm by a wet coating method using a reverse roll coater in an environment of 23 ° C. and 30% RH, and then dried. As a result, a 2.4-nm-thick second lubricant layer (4b) containing 3 mg of lubricant per m ² was formed on the carbon film (3). Then, a coating solution is prepared by dissolving only the compound represented by the chemical formula (a1) 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 800 ppm. did. Then, this coating liquid was applied onto the second lubricant layer (4b) by a wet coating method using a reverse roll coater in an environment of 23 ° C. and 30% RH, and then dried. As a result, ² mg per 1 m ² on the carbon film (3)
1.6nm thick first lubricant layer (4
a) was formed. In the entire lubricant layer, the chemical formula (a
The molar ratio of the compound represented by 1) to the compound represented by the chemical formula (d1) was 3: 7.

The tape material produced as described above was cut into 6.35 mm width by a slitter to obtain a 6.35 mm width magnetic tape sample (total thickness 5.3 μm, 80 minutes long).

(Example 46) The first lubricant layer was formed by the chemical formula (a
A magnetic tape sample was prepared in the same manner as in Example 45, except that only the compound shown in 2) was used.

(Example 47) The first lubricant layer was formed by the chemical formula (a
A magnetic tape sample was prepared in the same manner as in Example 45, except that only the compound shown in 3) was used.

(Example 48) The first lubricant layer was formed by the chemical formula (a
A magnetic tape sample was prepared in the same manner as in Example 45, except that only the compound shown in 4) was used.

(Example 49) The first lubricant layer was formed by the chemical formula (a
A magnetic tape sample was prepared in the same manner as in Example 45, except that only the compound shown in 5) was used.

(Example 50) The first lubricant layer was formed by the chemical formula (a
A magnetic tape sample was prepared in the same manner as in Example 45, except that only the compound shown in 6) was used.

(Example 51) The second lubricant layer (4b) was formed using only the compound represented by the chemical formula (e1), and the first lubricant layer (4b) was formed using only the compound represented by the chemical formula (b1). A magnetic tape sample was prepared in the same manner as in Example 45, except that 4a) was formed.

(Example 52) A magnetic tape sample was prepared in the same manner as in Example 51 except that the first lubricant layer (4a) was formed using only the compound represented by the chemical formula (b2). .

(Example 53) A magnetic tape sample was prepared in the same manner as in Example 51 except that the first lubricant layer (4a) was formed using only the compound represented by the chemical formula (b3). .

(Example 54) A magnetic tape sample was prepared in the same manner as in Example 51 except that the first lubricant layer (4a) was formed using only the compound represented by the chemical formula (b4). .

(Example 55) A magnetic tape sample was prepared in the same manner as in Example 51 except that the first lubricant layer (4a) was formed using only the compound represented by the chemical formula (b5). .

(Example 56) A magnetic tape sample was prepared in the same manner as in Example 1 except that the step of forming the nitrogen-containing plasma polymerized film on the surface layer of the carbon film (3) was omitted. The surface free energy of the surface of the carbon film on which the nitrogen-containing plasma polymerized film was not formed was measured immediately before forming the lubricant layer, and it was 43 mN / m.

(Example 57) A magnetic tape sample was produced in the same manner as in Example 1 except that the weight ratio of the organic solvent consisting of isopropyl alcohol and toluene was 8: 1.

(Example 58) A magnetic tape sample was prepared in the same manner as in Example 1 except that the weight ratio of the organic solvent consisting of isopropyl alcohol and toluene was set to 1: 8.

Comparative Example 1 Instead of the two-component lubricant used in Example 1, a known lubricant represented by the following chemical formula (x
A magnetic tape sample was prepared in the same manner as in Example 1 except that only the compound shown in 1) was used.

[Chemical 36]

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

[Chemical 37]

(Comparative Example 3) The same method as in Example 1 was repeated except that only the compound represented by the chemical formula (a1) was used in place of the two-component lubricant used in Example 1. A magnetic tape sample was prepared.

(Comparative Example 4) The same method as in Example 1 was repeated except that only the compound represented by the chemical formula (b1) was used in place of the two-component lubricant used in Example 1. A magnetic tape sample was prepared.

(Comparative Example 5) The same method as in Example 1 was repeated except that only the compound represented by the chemical formula (c1) was used in place of the two-component lubricant used in Example 1. A magnetic tape sample was prepared.

(Comparative Example 6) The same method as in Example 1 was repeated except that only the compound represented by the chemical formula (d1) was used in place of the two-component lubricant used in Example 1. A magnetic tape sample was prepared.

Comparative Example 7 The same method as in Example 1 was carried out except that only the compound represented by the chemical formula (e1) was used in place of the two-component lubricant used in Example 1. A magnetic tape sample was prepared.

Comparative Example 8 A magnetic tape sample was prepared in the same manner as in Example 1, except that only isopropyl alcohol was used in place of the mixed organic solvent consisting of isopropyl alcohol and toluene in the step of forming the lubricant layer. Was produced.

Comparative Example 9 Except that only toluene was used in place of the mixed organic solvent composed of isopropyl alcohol and toluene in the step of forming the lubricant layer,
A magnetic tape sample was prepared in the same manner as in Example 1.

Comparative Example 10 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 under the environment of 23 ° C. and 55% RH. Was produced.

[Measurement of surface free energy of each compound]
The surface free energy of each compound used in the above examples was measured according to the following procedure. First, each compound was mixed in a mixed organic solvent in which isopropyl alcohol and toluene were mixed at a weight ratio of 1: 1 and the concentration thereof was 2140.
A coating solution was prepared by dissolving so as to be ppm. And
This coating solution was used to form a protective film (surface free energy: 53 mN / m) formed on a non-magnetic support in the same manner as in Example 1.
Of the compound per 1 m ² by applying a wet coating method using a reverse roll coater at a temperature of 23 ° C. and 30% RH to a thickness of 6 μm. A layer was formed that was 0 mg. The surface free energy of the surface of the obtained layer was measured and used as the surface free energy of each compound. The automatic contact angle meter and solvent used for measuring the surface free energy are the same as those used for measuring the surface free energy of the surface of the protective film. The results are shown in Table 1.

[Measurement of Surface Free Energy of Surface of Lubricant Layer] After forming the lubricant layer in Examples 1 to 58 and Comparative Examples 1 to 10, the surface free energy of the surface of the lubricant layer was measured. The automatic contact angle meter and solvent used for measuring the surface free energy are the same as those used for measuring the surface free energy of the surface of the protective film. The results are shown in Tables 2-4.

For each magnetic tape sample obtained in Examples 1 to 58 and Comparative Examples 1 to 10, the following running durability test and weather resistance storage test were carried out.

[Running Durability Test] Reduced Output Commercially available digital VT modified for RF (high frequency) output measurement
R (Matsushita Electric Co., Ltd., NV-DJ1) was used to measure the RF output change after each sample was repeatedly regenerated for 300 hours in an environment of 5 ° C. and 80% RH for 300 passes. RF
The change in output is shown in decibels after the test as compared with that before the test.

Head dirt, running system powder adhesion Head dirt, that is, seizure of the head surface or adhesion of powder to the head surface, is evaluated by 5 levels by observing the dirt state of the tape sliding surface of the head surface with a differential interference microscope. did. The running system powder adhesion was evaluated on a scale of 5 by visually observing dirt (state of powder adhesion) on the post and the fixed drum after the tape was repeatedly reproduced for 300 passes. The evaluation criteria for head dirt and running system powder adhesion are as follows. 5: There is no problem in practical use. 4: There is no problem in practical use. 3: Practical, but need improvement. 2: Head dirt or running system powder adhesion is severe, and practically practical. 1: Head dirt or running system powder adhesion was so severe that it had no practical use.

[Weather resistance storability test] In order to evaluate the weather resistance storability of each 6.35 mm wide tape sample, the sample was kept at 60 ° C. for 8 hours.
The sample was allowed to stand in an environment of 0% RH for 10 days, and the still life and the head clogging of the sample after standing were measured.

Still life after storage The still life after storage was measured using a commercially available digital VTR (NV-DJ1 manufactured by Matsushita Electric Co., Ltd.) modified for still life measurement under the environment of 3 ° C. and 5% RH. . The still life after storage was shown as the time from the initial output until the output dropped by 6 dB.

Head clogging After leaving each sample for 10 days in an environment of 60 ° C. and 80% RH, a commercially available digital VTR modified for RF output measurement
(Matsushita Electric Co., Ltd., NV-DJ1) is used, 23 degreeC, 6
Under the environment of 0% RH, 100 passes were repeatedly reproduced for 133 hours, and head clogging was measured from the RF output during reproduction. During this repeated reproduction, it was assumed that the head clogging occurred when the RF output decreased by 6 dB or more, and the time when the reduction was measured was summed as the head clogging.

[0151]

[Table 1]

[0152]

[Table 2]

[0153]

[Table 3]

[0154]

[Table 4]

[0155]

[Table 5]

[0156]

[Table 6]

[0157]

[Table 7]

[0158]

[Table 8]

[0159]

[Table 9]

[0160]

[Table 10]

[0161]

[Table 11]

From Table 1 and Tables 2 to 4, in Example 1, the compound having a large surface free energy in the lubricant layer (that is, the compound represented by the chemical formula (d1)) has a smaller surface free energy. Compound (that is, chemical formula (a
1), the surface free energy of the surface of the lubricant layer is 2
It can be seen that it is smaller than the average surface free energy of the two compounds. The same applies to Examples 2-36.
This is because most of the compounds having a surface free energy closer to the surface free energy of the surface of the protective film moved to the protective film and was adsorbed to the protective film after the coating liquid was applied to the protective film. it is conceivable that.

As is clear from Tables 5 to 11, in comparison with Comparative Examples 1 to 10, all of the magnetic tapes obtained in Examples 1 to 58 show a small output reduction even after repeated running. It had excellent properties such as little dirt, little adhesion of running system powder, little head clogging during repeated running after storage, and good still life after storage.

Particularly, in the running durability test, even if the number of repetitions of reproduction is increased to 300 passes for 400 hours, the magnetic tapes of Examples 1 to 58 have less head stains and running system powder adherence. It is shown that the tape of (1) runs well in the tape running system, and a frictional force for separating powder from the recording medium during the running of the tape is unlikely to occur between the recording medium and the tape running system. Therefore, when the recording medium of the present invention is used, it is possible to suppress the occurrence of traveling troubles due to powder adhesion in the traveling system.

The magnetic tapes of Examples 1 to 58 are the comparative examples 1 and 2 using the conventional lubricant, and the general formulas (a1), (b1), (c1), (d1) or (e), respectively.
As compared with Comparative Examples 3 to 7 in which the lubricant layer was formed only with the compound shown in 1), all exhibited excellent running durability and weather resistance storage stability. Thus, at least one selected from the compounds represented by the general formulas (a), (b) and (c) having a surface free energy of 15 mN / m or more and less than 33 mN / m on the protective film (3). Types of compounds and surface free energy of 33 mN / m or more and 50 mN /
Examples 1 to 5 in which the lubricant layer (4) was formed with a lubricant containing at least one compound selected from the compounds represented by the general formulas (d) and (e) within the range of m or less.
The magnetic tape samples of No. 8 are obviously excellent in practical reliability such as running durability and weather resistance.

The magnetic tape sample of Example 56 uses the same lubricant as in Example 1, but the nitrogen-containing plasma polymerized film is not formed on the protective film (3). The running durability and weather resistance of Example 56 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 tape.

From Example 1 and Comparative Examples 8 and 9, a coating solution prepared by dissolving a lubricant in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent was applied onto the protective film (3) for lubrication. It is understood that by forming the agent layer (4), a tape sample excellent in practical reliability such as running durability and weather resistance can be stably prepared. In addition, Comparative Example 10 in which the coating liquid containing the lubricant was applied under high humidity is shown in Example 1.
Despite the use of the same lubricant, its running durability and weathering stability are both poor, indicating that application under high humidity is undesirable.

In Examples 1 to 58, the reverse roll coating method, which is a wet coating method, was adopted in the step of forming the lubricant layer (4), but the lubricant layer (4) having the same effect by the organic vapor deposition method is also used. ) Can be formed.

In Examples 1 to 58, the recording layer is C
Although the o-Ni metal thin film and the protective layer are described as the protective film, the recording layer is the GeSbTe metal thin film and the protective layer is the ZnS.
Similar effects were obtained even when -Si02 was used.

Although the embodiments in which the recording medium of the present invention and the manufacturing method thereof are applied to a tape for a commercial digital VTR have been described above, the metal thin film or metal oxide thin film of the present invention and the manufacturing method thereof are not limited thereto. not,
It can also be applied to a metal thin film or a metal oxide thin film such as a tape medium or a disk medium for data storage, an optical recording medium, an optical metal thin film or a metal oxide thin film.

[0171]

As described above, in the recording medium of the present invention, the free energy of the surface of the protective film is 40 mN / m or more, and the surface free energy of the lubricant layer is 15 mN / m.
From a second group consisting of at least one compound selected from the first group consisting of compounds in the range of m to less than 33 mN / m and a compound having a surface free energy in the range of 33 mN / m to 50 mN / m. It is characterized by including a lubricant containing at least one compound selected. Due to this feature, the adhesion strength and the covering property of the lubricant layer to the protective film are improved, so that the recording medium of the present invention exhibits good lubrication performance and excellent running durability and weather resistance storage stability. It will be highly responsive.

Further, in the recording medium of the present invention, by forming the nitrogen-containing plasma polymerized film on the surface layer of the protective film, the chemical adsorption force of the lubricant is improved, so that the adhesion strength of the lubricant layer to the protective film is further It is possible to obtain a recording medium that is improved and exhibits excellent lubricating performance. Due to these synergistic effects, the recording medium of the present invention has improved practical reliability such as running durability and weather storability without impairing electromagnetic conversion characteristics.

The recording medium of the present invention is manufactured by a manufacturing method including a step of coating a coating solution prepared by dissolving a lubricant in a specific mixed organic solvent on a protective film under specific humidity conditions. By using this coating solution, it is possible to obtain a lubricant layer having a uniform thickness without coating unevenness. Further, by limiting the range of 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 recording medium of the present invention which is excellent in practical reliability such as running durability and weather resistance.

[Brief description of drawings]

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

FIG. 2 is a schematic cross-sectional view of a thin film type tape which is one embodiment of the recording medium of the present invention.

[Explanation of symbols]

1 ... Non-magnetic support, 2 ... Metal thin film or metal oxide thin film (recording layer), 3 ... Protective film, 4 ... Lubricant layer, 4a ... First lubricant layer, 4b ... second lubricant layer, 5 ... back coat layer, 10 ... recording medium (tape)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 7/24 533 G11B 7/24 533K 5D121 534 534A 7/26 531 7/26 531 11/105 531 11 / 105 531B 531H 531M 546 546F // C10N 40:18 C10N 40:18 F term (reference) 4H104 BD07A PA16 5D006 AA01 AA05 AA06 5D029 HA06 LA20 NA12 5D075 EE03 FG04 5D05 A06 A21 BC08 5121 A08 BC02

Claims (12)

[Claims] 1. A metal thin film or a metal oxide thin film formed on one surface of a non-magnetic support, a protective film formed on the metal thin film or metal oxide thin film, and a lubricant formed on the protective film. A recording medium having a layer, wherein the surface free energy of the surface of the protective film is 40 mN / m or more, and the lubricant layer has a surface free energy of 15 mN / m or more 3
At least one compound selected from the first group consisting of compounds in the range of less than 3 mN / m and a second group consisting of compounds having a surface free energy in the range of 33 mN / m to 50 mN / m. A recording medium containing a lubricant containing at least one compound. 2. The recording medium according to claim 1, wherein the proportion of the compound selected from the second group gradually decreases toward the surface of the lubricant layer. 3. A first lubricant layer containing a lubricant containing 80% by weight or more of at least one compound selected from the first group, and at least one selected from the second group. A second lubricant layer containing a lubricant containing 80% by weight or more of a compound of a kind, the second lubricant layer is formed on the protective film, and the first lubricant layer is formed on the second lubricant layer. The recording medium according to claim 1, which is stored. 4. The recording medium according to claim 1, wherein the surface free energy of the surface of the lubricant layer is in the range of 15 mN / m or more and less than 33 mN / m. 5. The recording medium according to claim 1, wherein the surface free energy of the surface of the lubricant layer is in the range of 20 mN / m or more and less than 33 mN / m. 6. At least one selected from the first group
The kind of compound is at least one kind of compound selected from a fluorinated carboxylic acid, and the at least one kind of compound selected from the second group is at least one kind of compound selected from a fluorinated carboxylic acid ester. Item 6. The recording medium according to any one of items 1 to 5. 7. At least one compound selected from fluorine-containing carboxylic acids is represented by the following general formulas (a) to (c): (In the formula, 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, and b is 0.
Or 1) (In the formula, 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 from 0 to 20, and d is 0 or 1.) (Wherein i and j are integers of 1 or more) are at least one compound selected from the fluorine-containing carboxylic acids, and at least one compound selected from the fluorine-containing carboxylic acid ester is General formulas (d) and (e): (In the formula, R ⁶ represents a fluorine-containing organic group, R ⁷ represents an alkyl group or an alkenyl group, and n is an integer of 0 to 12) (In the formula, k and m are integers of 1 or more, and R ⁸ has 4 carbon atoms.
The recording medium according to claim 6, which is at least one compound selected from the group consisting of fluorinated carboxylic acid esters represented by the formula (1 to 22). 8. The ratio of the compound selected from the first group and the compound selected from the second group in the lubricant layer is in the range of 1: 9 to 8: 2 by molar ratio. 1-7
The recording medium according to any one of 1. 9. The protective film has a nitrogen-containing plasma polymerized film in the surface layer portion thereof, and the lubricant layer is formed on the nitrogen-containing plasma polymerized film of the protective film. Recording medium. 10. The method of manufacturing a recording medium according to claim 1, wherein the step of forming the lubricant layer dissolves the lubricant in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent. The relative humidity of the coating solution prepared by
A method of manufacturing a recording medium, which comprises a step of coating on a protective film in an environment in the range of%. 11. The method for manufacturing a recording medium according to claim 3, wherein the step of forming the lubricant layer includes the step of forming the first lubricant layer and the second lubricant layer, and the second lubricant layer. Forming a coating solution prepared by dissolving a lubricant containing 80% by weight or more of at least one compound selected from the second group in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent. , Relative humidity is 10-40
The step of forming the first lubricant layer in a mixed organic solvent of a hydrocarbon solvent and an alcohol solvent is selected from the first group. The coating liquid prepared by dissolving a lubricant containing at least one compound of 80% by weight or more has a relative humidity of 10 to 40.
A method of manufacturing a recording medium, comprising the step of applying the second lubricant layer under an environment in the range of%. 12. The method for producing a recording medium according to claim 10, wherein the mixing ratio of the hydrocarbon solvent and the alcohol solvent is in the range of 1: 9 to 9: 1 by weight.