JPH08106627A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To obtain a magnetic recording medium which always shows excellent traveling property, wear resistance, and durability. CONSTITUTION: This magnetic recording medium has at least a magnetic layer and a carbon protective film on a nonmagnetic supporting body. A long-chain hydrocarbon fatty acid having two triple bonds in the long-chain hydrocarbon group is held on the surface of the carbon protective film. Thereby, the long- chain hydrocarbon fatty acid gives lubricating performance under any conditions for use and the lubricating function can be maintained for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape or a magnetic disk, and more particularly to improving a lubricant.

[0002]

2. Description of the Related Art For example, a so-called metal thin film type magnetic recording medium in which a ferromagnetic metal material is deposited on a non-magnetic support by a technique such as vapor deposition and used as a magnetic layer, and a very fine magnetic material In a so-called coating type magnetic recording medium in which a magnetic coating material containing particles and a resin binder is coated on a non-magnetic support to form a magnetic layer, the smoothness of the magnetic layer surface is extremely good. Therefore, a substantial contact area with a sliding member such as a magnetic head or a guide roller is large, and a friction coefficient is large. As a result, an adhesion phenomenon (so-called sticking) is likely to occur with these sliding members, and there are many problems such as lack of running performance and durability.

Therefore, use of various lubricants has been studied in order to improve these problems. For example, a higher fatty acid or its ester is internally added to the magnetic layer or top coated to increase the friction coefficient. Attempts have been made to contain it.

[0004]

By the way, the lubricant used in the magnetic recording medium is required to have very strict characteristics. That is, (1) excellent low temperature characteristics are ensured so that a predetermined lubrication effect can be ensured when used in cold regions, and (2) spacing between the magnetic head and the magnetic head becomes a problem, and therefore extremely thin coating is possible. In addition, it is required that sufficient lubrication characteristics be exhibited, (3) that it be durable for a long period of time or used for a long period of time, and that the lubricating effect be sustained.

However, higher fatty acids and their esters, which have been used as lubricants so far, have insufficient lubrication performance, and for example, in a shuttle running test of a medium, reproduction output is attenuated early. Further, if the operating environment is hot and humid or low temperature, the lubrication performance is impaired, and the running property, wear resistance and durability of the medium cannot be improved.

Therefore, the present invention has been proposed in view of the above-mentioned conventional circumstances, and it is possible to maintain excellent lubricity under various conditions of use and to maintain the lubricity for a long time. It is an object of the present invention to obtain a magnetic recording medium and provide a magnetic recording medium excellent in running property, abrasion resistance, durability and the like.

[0007]

Means for Solving the Problems As a result of intensive studies by the inventors of the present invention, the carbon protective film was formed on a magnetic layer, and long-chain hydrocarbons were formed on the carbon protective film. It has been found that holding the long-chain hydrocarbon fatty acid having two triple bonds in the group greatly improves the running property, wear resistance, and durability of the medium.

The magnetic recording medium of the present invention has been proposed on the basis of such findings, and comprises at least a magnetic layer and a carbon protective film formed on a non-magnetic support. The above is characterized in that a long chain hydrocarbon fatty acid having two triple bonds in a long chain hydrocarbon group is retained as a lubricant.

In the magnetic recording medium of the present invention, a magnetic layer and a carbon protective film are formed on a non-magnetic support, and two triple bonds are added to a long chain hydrocarbon group as a lubricant on the carbon protective film. The long-chain hydrocarbon fatty acid possessed is retained.
This long-chain hydrocarbon fatty acid is represented by Chemical formula 2, for example.

[0010]

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The long-chain hydrocarbon fatty acid having two triple bonds in the long-chain hydrocarbon group improves the running property, wear resistance and durability of the medium by the following mechanism.

That is, when a long-chain hydrocarbon fatty acid having two triple bonds in a long-chain hydrocarbon group is coated on a carbon protective film, its polar carboxylic acid, a carboxylic acid, is adsorbed on the carbon protective film. Then, the lubricant film is formed by the cohesive force between the long-chain hydrocarbon groups, which are the hydrophobic groups.

Here, it is known that a long-chain hydrocarbon fatty acid having two triple bonds in a long-chain hydrocarbon group is generally polymerized by light (ultraviolet ray) or heat to become a polydiacetylene compound.

When this long-chain hydrocarbon fatty acid is held as a lubricant film on the carbon protective film, it is considered that polymerization is caused by light or heat which is expected to be generated by friction when the medium is run. The polymerization reaction formula is shown in Chemical formula 3.

[0015]

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As a result of such polymerization, a very thin monomolecular film level polymer film of a polydiacetylene compound is formed on the surface of the carbon protective film. This polymer film is very strong and will greatly improve the shuttle durability of the medium.

In the long-chain hydrocarbon fatty acid represented by Chemical formula 2, the carbon number m + n of the long-chain hydrocarbon group is 12 to 22.
It is desirable that When the carbon number m + n is 11 or less, the alkyl chain length is too short, and the friction / wear durability of the medium cannot be sufficiently improved. Also, carbon number m
When + n is 23 or more, the solubility in a solvent for forming a coating becomes low, and it becomes difficult to form a lubricant film.

The carbon number m of the carbon chain on the terminal side of the triple bond is 1 to 15, more preferably 7 to 13. When the carbon number m is 6 or less, the cohesive force between the lubricant molecules decreases, and the polymer formation by friction cannot be sufficiently achieved. On the other hand, when the carbon number m is 14 or more, the solubility in a solvent for forming a coating becomes low, and it becomes difficult to form a lubricant film.

On the other hand, the carbon number n of the carbon chain on the carboxylic acid group side of the triple bond is 2 to 12, more preferably 6 to 10. When the carbon number n is 5 or less, the distance of the triple bond between the lubricant molecules becomes long, and the polymerization becomes difficult. Also,
When the carbon number n is 11 or more, the positions of the triple bonds do not match between the lubricant molecules, and the polymerization reaction does not proceed smoothly.

In order to retain such a long-chain hydrocarbon fatty acid on the carbon protective film, the long-chain hydrocarbon fatty acid is dissolved in an organic solvent to prepare a lubricant solution, which is then applied to the surface of the carbon protective film. Just coat it. The coating amount of this long chain hydrocarbon fatty acid is 0.5 to 100 mg /
m ² , more preferably 1 to 20 mg / m ² .

As described above, the long chain hydrocarbon fatty acid is used as a lubricant in the present invention, but the following materials are used for the non-magnetic support, the magnetic layer and the protective film.

First, as the non-magnetic support, any of those usually used in magnetic recording media can be used. For example, polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate and cellulose butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonates, polyimides, polyamides. In addition to polymer materials such as, light metals such as aluminum alloys and titanium alloys, ceramics such as alumina glass, and the like. When a rigid substrate such as an aluminum alloy plate or a glass plate is used as the non-magnetic support, an oxide film such as alumite treatment or a Ni-P film is formed on the substrate surface to harden the surface. May be.

The magnetic layer is a metallic magnetic thin film formed by depositing a metallic magnetic material on a non-magnetic support by a PVD method such as plating, sputtering or vacuum deposition.

Fe, Co, Ni are used as the metal magnetic thin film.
And other metals, Co-Ni-based alloys, Co-Pt-based alloys, C
o-Pt-Ni based alloy, Fe-Co based alloy, Fe-Ni
Examples of the in-plane magnetization recording type metal magnetic film include a Fe-Co-Ni-based alloy, a Fe-Ni-B-based alloy, an Fe-Co-B-based alloy, and a Fe-Co-Ni-B-based alloy. To be Besides, a perpendicular magnetic recording type metal magnetic film made of a Co—Cr alloy or the like may be used.

Of these, in the case of the in-plane magnetization recording type metal magnetic thin film, Bi, Sb, Pb,
An underlayer of a low melting point non-magnetic material such as Sn, Ga, In, Ge, Si, Tl is formed in advance, and a metallic magnetic material is vertically vapor-deposited or sputtered on the underlayer to form a metallic magnetic thin film. It is good to form. When the metallic magnetic material is deposited on the underlayer, the low-melting point nonmagnetic material of the underlayer diffuses into the metallic magnetic thin film, and the orientation of the metallic magnetic thin film is eliminated to secure the in-plane isotropic property. And the anti-magnetism is improved.

The carbon protective film coated with the long-chain hydrocarbon fatty acid is for imparting durability to the medium. If this carbon protective film is not formed,
Even if a long chain hydrocarbon fatty acid is applied as a lubricant, the durability of the medium cannot be sufficiently improved.

As a method of forming the carbon protective film,
Although sputtering is generally used, various PVD methods can be used without any particular limitation. The thickness of the carbon protective film is 2 to 100 n from the viewpoint of sufficiently securing the protective effect and minimizing the spacing loss.
m is more preferable, and more preferably 5 to 30 nm.
Is.

The above is the basic structure of the present invention. The magnetic recording medium of the present invention is the same as a normal magnetic recording medium.
Further, various elements may be added to further improve the characteristics.

For example, a rust preventive agent may be top-coated with a lubricant on the carbon protective film. As the rust preventive, for example, phenols, naphthols, quinones, nitrogen-containing heterocyclic compounds, oxygen-containing heterocyclic compounds, sulfur-containing heterocyclic compounds and the like can be used.

The rust preventive may be used in combination with the above lubricant, but it is different from the lubricant layer such that the rust preventive is applied on the carbon protective film and then the lubricant is applied. It is highly effective when applied as a layer.

[0031]

According to the present invention, in a magnetic recording medium having a magnetic layer and a carbon protective film formed on a non-magnetic support, two triple bonds are added to a long chain hydrocarbon group as a lubricant on the carbon protective film. To retain long chain hydrocarbon fatty acids having

This long-chain hydrocarbon fatty acid exhibits excellent lubricating performance not only under normal temperature and normal humidity environment but also under high temperature and high humidity environment and low temperature environment, and the lubricating performance is maintained for a long period of time. It

Therefore, the above magnetic recording medium, due to the action of the carbon protective film and such long-chain hydrocarbon fatty acid, always exhibits excellent shuttle durability under various conditions of use, and has good running property and wear resistance. ， Durability is obtained.

[0034]

EXAMPLES Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

First, the general formula of the long-chain hydrocarbon fatty acid used as the lubricant in this example is shown in Chemical formula 4. Example 1 below
In Example 34, a long-chain hydrocarbon fatty acid represented by Chemical formula 4 having carbon numbers m and n shown in Tables 1 and 2 was used as a lubricant to prepare a magnetic tape.

[0036]

[Chemical 4]

[0037]

[Table 1]

[0038]

[Table 2]

For comparison, the general formula of the lubricant is
Shown in In Comparative Examples 1 to 11 below, magnetic tapes were prepared by using the long-chain hydrocarbon fatty acid represented by Chemical formula 5 and having the carbon number p shown in Table 3 as a lubricant.

[0040]

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[0041]

[Table 3]

Example 1 On a polyethylene terephthalate film having a thickness of 10 μm, a Co—Ni alloy film having a thickness of 100 nm was formed as a ferromagnetic metal thin film by the oblique vapor deposition method. Then, a film thickness of 15 nm is formed on the ferromagnetic metal thin film by the sputtering method.
A carbon protective film was formed.

Next, a lubricant layer is formed by applying a long-chain hydrocarbon fatty acid represented by the formula 4 and having a carbon number m of 7 and a carbon number n of 6 on the carbon protective film to form a lubricant layer having a width of 8 mm. A sample tape was prepared by cutting into pieces.

Examples 2 to 34 The same as Example 1 except that a long chain hydrocarbon fatty acid represented by Chemical Formula 4 and having carbon numbers m and n shown in Table 1 or 2 is used as the lubricant. Then, a sample tape was prepared.

Comparative Examples 1 to 11 Example 1 was repeated except that a long chain hydrocarbon fatty acid represented by Chemical formula 5 and having a carbon number p represented by Table 3 was used as the lubricant.
A sample tape was prepared in the same manner as in.

Regarding the sample tape prepared as described above, the temperature is 40 ° C. under the environment of temperature 25 ° C. and humidity 60%.
In an environment with a humidity of 80% and a temperature of -5 ° C,
The friction coefficient, still durability, and shuttle durability were measured.

The still durability was evaluated by performing still reproduction on the sample tape and measuring the time for the output to decay to -3 dB.

The shuttle durability was evaluated by repeating the shuttle running for 2 minutes on the sample tape as one shuttle running and measuring the number of shuttles until the output decreased by -3 dB.

Tables 4 to 6 show the measured friction coefficient, still durability and shuttle durability.

[0050]

[Table 4]

[0051]

[Table 5]

[0052]

[Table 6]

As shown in Tables 4 to 6, the sample tapes of Examples 1 to 34 using the long-chain hydrocarbon fatty acid having two triple bonds in the long-chain hydrocarbon group as the lubricant were Excellent friction coefficient, still durability, and shuttle durability can be obtained even in the environment.

On the other hand, the sample tapes of Comparative Examples 1 to 11 using the long-chain hydrocarbon fatty acid having no triple bond as the lubricant are more ordinary temperature and normal humidity than the sample tapes of Examples 1 to 34. The shuttle durability in the environment is inferior, and the friction coefficient greatly increases in the high temperature and high humidity environment and the low temperature environment, and sufficient still durability and shuttle durability cannot be obtained.

From this, it was found that the lubricant must be a long-chain hydrocarbon fatty acid and that the long-chain hydrocarbon group should have two triple bonds.

[0056]

As is apparent from the above description, in the magnetic recording medium of the present invention, at least a magnetic layer and a carbon protective film are formed on a non-magnetic support, and a long chain is further formed on the carbon protective film. Since the long-chain hydrocarbon fatty acid having two triple bonds in the hydrocarbon group is retained, the lubricating performance is exhibited under any conditions of use, and the lubricating performance is retained for a long period of time. Therefore, it is possible to always obtain excellent running property, wear resistance, and durability.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C10N 40:18

Claims (2)

[Claims] 1. At least a magnetic layer on a non-magnetic support,
A magnetic recording medium comprising a carbon protective film, wherein a long-chain hydrocarbon fatty acid having two triple bonds in a long-chain hydrocarbon group is retained as a lubricant on the carbon protective film. . 2. The magnetic recording medium according to claim 1, wherein the long-chain hydrocarbon fatty acid has a structure represented by Chemical formula 1. Embedded image