JP3154232B2 - Magnetic recording media - Google Patents

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 and a magnetic disk having a magnetic layer formed of a ferromagnetic metal thin film formed on a non-magnetic support.

[0002]

SUMMARY OF THE INVENTION The present invention provides a magnetic recording medium having a magnetic layer on a nonmagnetic support, wherein a salt compound of a perfluoropolyether having a hydroxyl group in a molecule and an amine is used as a lubricant. Accordingly, an object of the present invention is to provide a magnetic recording medium that exhibits excellent running properties, wear resistance, and durability under various use conditions.

[0003]

2. Description of the Related Art For example, in 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 method such as vapor deposition and the magnetic layer is used as a magnetic layer, the surface of the magnetic layer has a smoothness. Because it is extremely good, a substantial contact area with a sliding member such as a magnetic head or a guide roller is large,
Therefore, there are many problems such as an increase in the coefficient of friction, a tendency for adhesion phenomenon (so-called sticking) to occur, and lack of running property and durability.

In order to solve these problems, use of various lubricants has been studied. Conventionally, a higher fatty acid or an ester thereof has been top-coated on the magnetic layer of the magnetic recording medium. Attempts have been made to reduce the coefficient of friction.

[0005] By the way, lubricants used for magnetic recording media are required to have extremely severe properties due to their properties, and it is presently difficult for conventional lubricants to cope with them.

That is, the lubricant used for the magnetic recording medium includes (1) excellent low-temperature characteristics so as to secure a predetermined lubrication effect when used in a cold region, and (2) a lubricant with a magnetic head. Since pacing is a problem, it can be applied very thinly, and in that case, sufficient lubricating properties can be exhibited. (3) It can be used for a long time or for a long time,
It is required that the lubrication effect be maintained.

However, higher fatty acids and their esters, which have been conventionally used, freeze and solidify under low-temperature conditions such as 0 ° C. or lower, impairing the function as a lubricant, or having a long-term durability. Tend to lack.

[0008]

As described above, in the field of magnetic recording media, due to lack of ability of the lubricant used, the practical characteristics such as running property and durability remain unsatisfactory. I have. Therefore, the present invention provides a magnetic recording medium that maintains excellent lubricity under various use conditions, maintains a lubricating effect for a long time, and has excellent running properties, wear resistance, durability, and the like. It is the purpose.

[0009]

Means for Solving the Problems The inventor of the present invention has conducted intensive studies on the achievement of the above-mentioned object, and as a result, a salt compound of a perfluoropolyether having a hydroxyl group in the molecule and an amine has been developed for this purpose. It has been found that they are compatible, and the present invention has been completed.

That is, according to the present invention, there is provided a magnetic recording medium having a magnetic layer comprising a ferromagnetic metal thin film formed on a non-magnetic support, wherein a hydroxyl group represented by the following general formula is formed on the magnetic layer. And a lubricant layer containing a salt compound of a perfluoropolyether and an amine having the following. (However, R _f represents a perfluoropolyether group.
R, R ¹ , R ² and R ³ represent a hydrogen atom or the same or different hydrocarbon groups. )

[0011]

According to the present invention, the lubricant layer is applied to the surface of a thin-film magnetic recording medium such as a vapor-deposited tape so that it can be used under severe conditions such as high temperature, high humidity or low temperature and low humidity. However, good durability can be obtained, and its characteristics do not deteriorate.

The above salt compound can be obtained, for example, by adding an amine compound to a perfluoropolyether having a hydroxyl group in an equimolar amount to the hydroxyl group, and heating and mixing at a temperature higher than the melting point of the amine.

The synthesis example will be specifically described. 2.69 g of stearylamine was added to 10 g of a perfluoropolyether having a molecular weight of 2,000 and having hydroxyl groups at both terminals to give 70
Heat and mix at 10 ° C for 10 minutes to obtain a waxy compound after cooling. The infrared absorption spectrum is shown in Figure 1, disappeared stretching vibration of the hydroxyl groups of 3400 cm ^-1, stretching vibration of CH around 2900 cm ^-1 is also 1350 the stretching vibration of CF is observed in 1050 cm ^-1 from Determines the structure of the compound.

In the present invention, the perfluoropolyether having a terminal hydroxyl group and the amine forming a salt compound with the perfluoropolyether are selected irrespective of the molecular weight, branched structure, unsaturated bond, isomer structure and alicyclic structure. be able to. Specifically, the structure is shown in Table 1 below.

It is possible to use monofunctional and polyfunctional perfluoropolyethers, for example, as monofunctional, The polyfunctionality includes, but is not limited to, HOCH ₂ (CF ₂ CF ₂ O) _p (CF ₂ O) _q CF ₂ CH ₂ OH.

Here, k, l, m, n, p and q in the chemical structural formula of the perfluoropolyether represent an integer of 1 or more. The molecular weight is not particularly limited, but is preferably about 600 to 5,000. If the molecular weight is too large, the effect of the amine salt, which is an adsorptive group (to increase the lubricating effect by strongly adsorbing on the magnetic layer surface due to its large polarity) will be small. The effect of lowering the surface energy) is reduced. In the case of an amine, an alkyl group exhibits an effect (to increase the van der Waals force to stabilize the lubricating film structure), and the effect is large when the alkyl group has 10 or more carbon atoms.

The magnetic recording medium of the present invention has an amine salt compound of perfluoropolyether having a hydroxyl group in a molecule as a lubricant.

Here, as a magnetic recording medium to which the present invention is applied, for example, as shown in FIG. 2, a magnetic film is formed as a magnetic layer 2 on the surface of a non-magnetic support 1 by a method such as vapor deposition. It can be applied to a so-called metal thin film type magnetic recording medium. In this metal thin film type magnetic recording medium, the above-mentioned lubricant layer 3 is provided on the magnetic layer 2. Further, the present invention can be applied to a magnetic recording medium having a configuration in which an underlayer (not shown) is provided between the nonmagnetic support 1 and the magnetic layer 2.

In this case, the non-magnetic support and metal magnetic thin film of the metal thin film type magnetic recording medium to which the present invention can be applied are not limited at all, and any conventionally known ones can be used.

For example, as the nonmagnetic support,
The same type as the coating type magnetic recording medium can be used.
In this case, when a rigid substrate such as an Al alloy plate or a glass plate is used for 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. You may make it.

The metal magnetic thin film is formed as a continuous film by a PVD technique such as plating, sputtering, or vacuum deposition, and is made of a metal such as Fe, Co, or Ni, a Co—Ni alloy, or a Co—Ni alloy.
-Pt alloy, Co-Pt-Ni alloy, Fe-Co alloy, Fe-Ni
Alloy, Fe-Co-Ni alloy, Fe-Ni-B alloy, Fe-Co
In-plane magnetization recording metal magnetic films and Co-Cr-based alloy thin films made of -B-based alloys, Fe-Co-Ni-B-based alloys and the like are exemplified.

In particular, in the case of an in-plane magnetization recording metal magnetic thin film,
Bi, Sb, Pb, Sn, Ga, In, Ge, S on a non-magnetic support in advance
forming an underlayer of a low-melting nonmagnetic material such as i, Tl,
Metallic magnetic material is deposited or sputtered from the vertical direction,
By diffusing these low-melting non-magnetic materials into the metal magnetic thin film, eliminating orientation and ensuring in-plane isotropy,
The coercivity may be improved.

When a hard disk is used, a hard protective film such as a carbon film, a diamond-like or amorphous carbon film, a chromium oxide film, and a SiO ₂ film may be formed on the surface of the metal magnetic thin film.

As a method for making the metal thin film type magnetic recording medium contain the amine salt compound of perfluoropolyether having a hydroxyl group in the molecule, a lubricant layer is formed on the surface of the metal magnetic thin film or the protective film. There is a method of coating. In this case, the coating amount of the amine salt compound of perfluoropolyether having a hydroxyl group in the molecule is preferably 0.5 to 100 mg / m ² , and 1 to 20 mg / m ^2.
/ M ² is more preferable.

The above-mentioned amine salt compound of perfluoropolyether having a hydroxyl group in the molecule may be used alone as a lubricant for a magnetic recording medium, or may be used in combination with a conventionally known lubricant.

Further, in order to cope with more severe conditions and maintain the lubricating effect, an extreme pressure agent may be used in combination at a weight ratio of about 30:70 to 70:30.

The extreme pressure agent reacts with the metal surface due to the frictional heat generated when partial metal contact occurs in the boundary lubrication region, and forms a reaction product film to thereby prevent friction and wear. A phosphorus-based extreme pressure agent,
Sulfur-based extreme pressure agent, halogen-based extreme pressure agent, organometallic extreme pressure agent,
Any of composite extreme pressure agents and the like can be used.

Further, in addition to the above-mentioned lubricant and extreme pressure agent, if necessary, a rust preventive may be used in combination. As the rust inhibitor, any one which is usually used as a rust inhibitor for this type of magnetic recording medium can be used, for example, phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, oxygen atoms And heterocyclic compounds containing a sulfur atom.

Incidentally, in the above-described metal thin film type magnetic recording medium, a back coat layer, an undercoat layer and the like may be formed as necessary in addition to the metal magnetic thin film as the magnetic layer.

For example, the backcoat layer is formed by adding a carbon-based fine powder for imparting conductivity to the same resin binder as the magnetic coating film or an inorganic pigment for controlling the surface roughness to form a coating. Things. In the present invention,
The back coat layer may contain the above-mentioned amine salt compound of perfluoropolyether having a hydroxyl group in the molecule as a lubricant internally or by a top coat. Alternatively, various combinations are possible, such as internally adding and top-coating a magnetic coating film or a metal magnetic thin film and a back coat layer as amine salt compounds of perfluoropolyether having a hydroxyl group in each molecule. The present invention can be applied to not only a metal thin film type but also a coating type magnetic recording medium and a magnetic recording medium using an oxide magnetic powder.

[0032]

The amine salt compound of perfluoropolyether having a hydroxyl group in the molecule exerts a good lubricating action and reduces the coefficient of friction. Further, this lubricating action is not impaired even under severe conditions such as low temperature. Therefore, a magnetic recording medium using a perfluoropolyether amine salt compound having a hydroxyl group in the molecule as a lubricant has a running property due to the lubricating effect of the perfluoropolyether amine salt compound having a hydroxyl group in the molecule. Improvement is achieved, and durability is improved.

[0033]

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, an example of the lubricant of the present invention was synthesized as follows. This synthesis corresponded to the synthesized product 7 in Table 1 below. That is, molecular weight 20
Perfluoropolyether having hydroxyl groups at both ends of 00
Add 2.69 g of stearylamine to 10 g, and at 70 ° C
After heating and mixing for 10 minutes, a waxy compound was obtained after cooling. The infrared absorption spectrum is shown in Figure 1, disappeared stretching vibration of the hydroxyl groups of 3400 cm ^-1, stretching vibration of CH around 2900 cm ^-1 is also 1350 the stretching vibration of CF is observed in 1050 cm ^-1 from , The structure of this compound was determined.

Table 1 shows perfluoropolyether amine salt compounds having a hydroxyl group in the molecule, which were synthesized in the same manner according to the above synthesis examples.

Using the composites shown in Table 1, the following magnetic recording media were prepared. An embodiment applied to a metal thin film type magnetic recording medium (evaporated tape) will be described.

Example 1 Co was applied to a 14 μm thick polyethylene terephthalate film by oblique deposition to form a 200 nm thick ferromagnetic metal thin film. Next, a solution prepared by dissolving Compound 1 in Table 1 in a mixed solvent of Freon and ethanol was applied to the surface of the metal magnetic thin film so that the coating amount was 5 mg / m ^2, and cut into 8 mm width. To prepare a sample tape.

Examples 2 to 14 and Comparative Examples 1 to 4 In Example 1, compound 1 in Table 1 used as a lubricant was changed to compound 2 to compound 14, and In the same manner as in Example 1, sample tapes of Examples 2 to 14 corresponding to the respective synthetic products were produced.

Each of the sample tapes prepared as described above was subjected to a temperature of -5 ° C. at a temperature of 25 ° C. and a humidity of 60%.
At this time, the friction coefficient, still durability, and shuttle durability at a temperature of 40 ° C. and a humidity of 80% were measured. The still durability evaluated the decay time of the output in the pause state to -3 dB. Shuttle durability was evaluated by the number of shuttles required for the shuttle to run for 2 minutes each time and the output to decrease by 3 dB. In addition, as a comparative example, a blank tape using no lubricant at all and a case where perfluoropolyether having a hydroxyl group in a molecule was used alone as a lubricant were also measured. Table 2 shows the results.

As is apparent from Table 2, an amine salt compound of a perfluoropolyether having a hydroxyl group in the molecule is used as compared with a case where a perfluoropolyether having a hydroxyl group in the molecule is used alone as a lubricant. As a result, the friction coefficient, still durability, shuttle durability and the like were not deteriorated even under various conditions, and very good results were obtained.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[0044]

As is apparent from the above description, the magnetic recording medium of the present invention uses, as a lubricant, an amine salt compound of perfluoropolyether having a hydroxyl group in a molecule, which has extremely excellent lubricity. Since it possesses, lubricating properties can be maintained under any use conditions, and the lubricating properties can be maintained for a long period of time. Therefore, the magnetic recording medium of the present invention has excellent running properties, abrasion resistance and durability.

[Brief description of the drawings]

FIG. 1 is an infrared absorption spectrum of an example of the salt compound of the present invention.

FIG. 2 is a sectional view showing an example of the magnetic recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Non-magnetic support 2 ... Metal magnetic thin film 3 ... Lubricant layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI C10N 30:06 40:18 50:02 (58) Investigated field (Int.Cl. ⁷ , DB name) G11B 5/71 G11B 5 / 725 C10M 107/38 C10M 105/58-105/66 C10N 40:18

Claims (1)

(57) [Claims] 1. A magnetic recording medium in which a magnetic layer made of a ferromagnetic metal thin film is formed on a non-magnetic support, wherein a perfluoro group having a hydroxyl group in a molecule represented by the following general formula is formed on the magnetic layer. A magnetic recording medium comprising a lubricant layer containing a salt compound of a polyether and an amine. (However, R _f represents a perfluoropolyether group.
R, R ¹ , R ² and R ³ represent a hydrogen atom or the same or different hydrocarbon groups. )