JPH05247483A - Lubricant and magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which can keep its excellent slidability under various conditions, maintains its sliding effect for a long time, and excels in running properties, abrasion resistance, durability, etc., by using a lubricant comprising a perfluoropolyether containing terminal hydroxyl and a long-chain hydrocarbon containing inner hydroxyl. CONSTITUTION:The title lubricant comprises a perfluoropolyether containing terminal hydroxyl and a long-chain hydrocarbon containing inner hydroxyl. The perfluoropolyether/long-chain hydrocarbon ratio is desirably 0.01-100 (by a molar ratio).

Description

Detailed Description of the Invention

[0001]

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

[0002]

SUMMARY OF THE INVENTION According to the present invention, in a magnetic recording medium having a magnetic layer on a non-magnetic support, a long-chain hydrocarbon having a hydroxyl group in the molecule is added to perfluoropolyether having a hydroxyl group at the terminal. By using a lubricant, it is intended 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 used as a magnetic layer, the smoothness of the magnetic layer surface is Since it is extremely good, the substantial contact area with sliding members such as magnetic heads and guide rollers is large,
Therefore, the friction coefficient becomes large, the adhesion phenomenon (so-called sticking) is likely to occur, and there are many problems such as lack of running property and durability.

Therefore, it has been studied to use various kinds of lubricants in order to improve these problems. Conventionally, a higher fatty acid or its ester is top-coated on the magnetic layer of the magnetic recording medium. Attempts have been made to reduce the coefficient of friction.

By the way, the lubricant used in the magnetic recording medium is required to have extremely strict characteristics, and it is difficult to cope with the conventional lubricant.

That is, the lubricant used in the magnetic recording medium is (1) excellent in low temperature characteristics so as to ensure a predetermined lubricating effect when used in cold regions, and (2) a lubricant with a magnetic head. Since pacing becomes a problem, it can be applied extremely thinly, sufficient lubrication characteristics can be exhibited even in that case, (3) It can withstand a long time or use for a long time,
It is required that the lubrication effect continues.

However, conventionally used higher fatty acids and their esters are frozen and solidified under low temperature conditions such as 0 ° C. or lower, impairing the function as a lubricant, and having long-term durability. Tends to lack.

[0008]

As described above, in the field of magnetic recording media, practical properties such as running property and durability are unsatisfactory due to insufficient capacity of the lubricant used. There is. Therefore, the present invention provides a magnetic recording medium that maintains excellent lubricity under various conditions of use, has a long-lasting lubrication effect, and is excellent in runnability, wear resistance, durability, and the like. It is intended.

[0009]

The present inventor has conducted extensive studies as a means to achieve the above-mentioned object, and as a result, perfluoropolyether having a hydroxyl group at the terminal and long-chain carbonization having a hydroxyl group in the molecule. The present inventors have found that a lubricant containing hydrogen and a magnetic recording medium containing the same meet this purpose, and completed the present invention.

That is, the magnetic recording medium of the present invention is a magnetic recording medium having at least a magnetic layer formed on a non-magnetic support, and comprises a perfluoropolyether having a hydroxyl group at the terminal and a hydroxyl group in the molecule. A magnetic recording medium characterized in that it has a lubricant consisting of a long-chain hydrocarbon.

Further, the present invention comprises a perfluoropolyether having a hydroxyl group at the terminal and a long-chain hydrocarbon having a hydroxyl group in the molecule, and the ratio of the long-chain hydrocarbon to the perfluoropolyether (perfluoropolyether). A lubricant having a molar ratio of (polyether / long-chain hydrocarbon) of 0.01 to 100, and a magnetic recording medium having the lubricant are also provided.

That is, the present invention is particularly good even when used under severe conditions such as high temperature and high humidity or low temperature and low humidity by applying the above lubricant to the surface of a thin film magnetic recording medium such as a vapor deposition tape. It has excellent durability and its characteristics are not deteriorated.

The long-chain hydrocarbon having a hydroxyl group in the molecule of the present invention specifically has a structure shown in Table 1 below, and preferably has a carbon number of 6 or more and 30 or less. Further, it can be selected regardless of its branched structure, unsaturated bond, isomer structure, or alicyclic structure. More preferably, it is composed of an alkyl group, has a large effect when the number of carbon atoms is 10 or more, and is preferably a linear one having 22 or less. When the number of carbon atoms is small, the effect (the effect of increasing the strength of the lubricating film by van der Waals force due to the hydrocarbon group) is small, and when it is large, the solubility is small.

As the perfluoropolyether having a hydroxyl group at the terminal, it is possible to use monofunctional and polyfunctional perfluoropolyethers. For example, as the monofunctional, for example, Demnum manufactured by Daikin Industries: F (CF ₂ CF ₂ CF ₂
O) _n CF ₂ CF ₂ CH ₂ OH, DuPont ₂ ) _l CH ₂ OH, and as a polyfunctional compound, Fomblin Z-DIAC: HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _p (CF
₂ O) _q CF ₂ CH ₂ OH, but not limited thereto.

Here, k, l, m, n, p and q in the chemical structural formula of the perfluoropolyether represent integers of 1 or more. The molecular weight is not particularly limited, but is preferably about 600 to 5000. If the molecular weight is too large, the effect of the adsorbing group (the part that adsorbs to the substrate in the polar part) becomes small, and if it is small, the effect of fluorine (having water repellency and lowering the surface energy) is weakened.

The magnetic recording medium of the present invention contains a mixture of perfluoropolyether having a hydroxyl group at the terminal and a long-chain hydrocarbon having a hydroxyl group in the molecule as a lubricant. Particularly effective lubricants are those having a molar ratio of perfluoropolyether / long-chain hydrocarbon of 0.01 to 100.

In the magnetic recording medium to which the present invention is applied, for example, as shown in FIG. 1, 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.
An underlayer (not shown) between the non-magnetic support 1 and the magnetic layer 2.
It can be applied to a magnetic recording medium having a configuration through.

In this case, the non-magnetic support and the metal magnetic thin film of the applicable metal thin film type magnetic recording medium are not particularly limited, and any conventionally known one can be used.

For example, as the non-magnetic support,
The same 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 as the non-magnetic support, an oxide film such as alumite treatment or Ni-P film is formed on the substrate surface to harden the surface. You may do so.

The metal magnetic thin film is formed as a continuous film by a PVD method such as plating, sputtering, vacuum deposition, and the like. Metals such as Fe, Co and Ni, Co--Ni alloys and Co.
-Pt alloy, Co-Pt-Ni alloy, Fe-Co alloy, Fe-Ni
Alloys, Fe-Co-Ni alloys, Fe-Ni-B alloys, Fe-Co
Examples include in-plane magnetization recording metal magnetic films and Co-Cr alloy thin films made of -B alloys, Fe-Co-Ni-B alloys and the like.

In particular, in the case of an in-plane magnetization recording metal magnetic thin film,
Bi, Sb, Pb, Sn, Ga, In, Ge, S on the non-magnetic support in advance.
An underlayer of a low melting point non-magnetic material such as i or Tl is formed in advance,
Metal magnetic material is vapor-deposited or sputtered from the vertical direction,
These low melting point non-magnetic materials are diffused in the metal magnetic thin film to eliminate the orientation and ensure the in-plane isotropic property.
The anti-magnetism may be improved.

In the case of a hard disk, 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.

In the metal thin film type magnetic recording medium, perfluoropolyether having a hydroxyl group at the terminal is added with a long-chain hydrocarbon having a hydroxyl group in the molecule (especially 0.01 to 10 in molar ratio).
(0) As a method of retaining the added lubricant, there is a method of top-coating a lubricant layer on the surface of the metal magnetic thin film or the surface of the protective film. In this case, the coating amount of the compound obtained by adding a long-chain hydrocarbon having a hydroxyl group in the molecule (particularly 0.01 to 100 in a molar ratio) to perfluoropolyether having a hydroxyl group at the terminal is 0.5 to 100 mg / m ² . Desirably 1
More preferably, it is about ²⁰ mg / m ² .

A compound obtained by adding a long-chain hydrocarbon having a hydroxyl group in the molecule (particularly 0.01 to 100 in molar ratio) to the above-mentioned perfluoropolyether having a hydroxyl group at the terminal is used alone as a lubricant for a magnetic recording medium. However, it may be used in combination with a conventionally known lubricant.

Further, in order to cope with more severe conditions and to 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 frictional heat generated when a metal contact is partially generated in the boundary lubrication region, and forms a reaction product film to prevent friction and wear. Which is a phosphorus-based extreme pressure agent,
Sulfur-based extreme pressure agent, halogen-based extreme pressure agent, organometallic extreme pressure agent,
Any compound type extreme pressure agent can be used.

In addition to the above lubricant and extreme pressure agent, a rust preventive agent may be used in combination, if necessary. As the rust preventive, any rust preventive commonly used as a rust preventive for magnetic recording media of this type can be used, and examples thereof include phenols, naphthols, quinones, nitrogen atom-containing heterocyclic compounds, and oxygen atoms. And a heterocyclic compound containing a sulfur atom.

By the way, in the above-mentioned metal thin film type magnetic recording medium, in addition to the metal magnetic thin film which is the magnetic layer, a back coat layer, an undercoat layer and the like may be formed if necessary.

For example, the back coat layer is formed by coating a carbon-based fine powder for imparting conductivity to the resin binder similar to that of the magnetic coating film and an inorganic pigment for controlling the surface roughness. It is a thing. In the present invention,
To this back coat layer, a lubricant prepared by adding a long-chain hydrocarbon having a hydroxyl group in the molecule (especially in a molar ratio of 0.01 to 100) to the above-mentioned perfluoropolyether having a hydroxyl group is internally added or a top coat. You may make it contain by.
Alternatively, a long-chain hydrocarbon having a hydroxyl group in the molecule is added to a perfluoropolyether having a hydroxyl group at the terminal (especially in a molar ratio of 0.01 to 100) for both the magnetic coating film or the magnetic metal thin film and the back coat layer. ) Various combinations such as internal addition of the added lubricant and top coating are possible. The present invention is applicable not only to a metal thin film type, but also to a coating type magnetic recording medium and a magnetic recording medium using oxide magnetic powder.

[0030]

EFFECTS OF THE INVENTION A long-chain hydrocarbon having a hydroxyl group in the molecule is added to a perfluoropolyether having a hydroxyl group at the terminal (especially 0.
The added lubricant (in a molar ratio of 01-100) exerts a good lubricating effect 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 prepared by coating a lubricant containing perfluoropolyether having a hydroxyl group in the molecule with a long-chain hydrocarbon having a hydroxyl group in the molecule (especially at a molar ratio of 0.01 to 100) is Add long-chain hydrocarbons with hydroxyl groups to perfluoropolyethers with hydroxyl groups (especially 0.01 to 100
The above-mentioned lubrication effect of the added lubricant (at a molar ratio of 1) improves runnability and improves durability.

[0031]

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.

Table 1 shows a lubricant obtained by adding a long-chain hydrocarbon having a hydroxyl group in the molecule to perfluoropolyether having a hydroxyl group in the molecule.

Using the lubricants shown in Table 1, magnetic recording media shown below were prepared. An example applied to a metal thin film type magnetic recording medium (vapor deposition tape) will be described.

Example 1 Co was deposited on a polyethylene terephthalate film having a thickness of 10 μm by oblique vapor deposition to form a ferromagnetic metal thin film having a thickness of 200 nm. Next, on the surface of this metal magnetic thin film, the lubricant (perfluoropolyether: long-chain hydrocarbon =
40:60 (mol%), molecular weight perfluoropolyethers about 2000, was applied to the coating amount those long-chain hydrocarbons was dissolved 326) in a mixed solvent of Freon and ethanol is 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, the lubricant was changed as shown in Table 1,
A sample tape was produced in the same manner as in Example 1 except for the above.

For each sample tape prepared as described above, when the temperature is 25 ° C. and the humidity is 60%, the temperature is −5 ° C.
At that time, the friction coefficient, the still durability, and the shuttle durability at a temperature of 40 ° C. and a humidity of 80% were measured. For still durability, the decay time of the output in the pause state up to -3 dB was evaluated. The shuttle durability was evaluated by the number of shuttles until the output decreased by 3 dB after running the shuttle for 2 minutes each time. In addition, as a comparative example, a blank tape using no lubricant and a case where perfluoropolyether having a hydroxyl group at the end was used alone as a lubricant were also measured. The results are shown in Table 2.

As is clear from Table 2, the perfluoropolyether having a hydroxyl group at the terminal has a longer hydroxyl group than that in the case where the perfluoropolyether having a hydroxyl group at the terminal is used alone as the lubricant. By using the lubricant containing the chain hydrocarbon, the friction coefficient, the still durability, the shuttle durability and the like were not deteriorated under various conditions, and very good results were obtained.

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

Examples 15 to 40 and Comparative Example 5 A lubricant containing a long-chain hydrocarbon having a hydroxyl group at a molar ratio of 0.005 to 120 was added to a perfluoropolyether having a hydroxyl group at the terminal. It is shown in Table 3. Magnetic tapes were prepared in the same manner as described above using the lubricants shown in Table 3. The friction coefficient of this tape was measured in the same manner as described above, and the results are shown in Table 4.

As is clear from Table 4, a hydroxyl group in the molecule is added to the perfluoropolyether having a hydroxyl group at the terminal, as compared with the case where a perfluoropolyether having a hydroxyl group at the terminal is used alone as a lubricant. By using a lubricant containing 0.01 to 100 of long-chain hydrocarbons, the friction coefficient did not deteriorate under various conditions and very good results were obtained.

Table 3-1 (Lubricants used) Perfluoropolyether alcohol F (CF ₂ CF ₂ CF ₂ 0) _n CF ₂ CF ₂ CH ₂ OH C ₁₈ H ₃₇ OH ───────── ──────────────────────── Lubricant Perfluoropolyether / Alcohol (molar ratio) ─────────────── ────────────────── Comparative Example 5 Alcohol only Example 15 0.005 Example 16 0.01 Example 17 0.1 Example 18 0.3 Example 19 0.5 Example 20 1.0 Example 21 3.0 Example 22 5.0 Example 23 10 Example 24 30 Example 25 100 Example 26 110 Example 27 120 Comparative Example 2 Perfluoropolyether only ───────────────── ───────────────

Table 3-2 (Lubricants used) Perfluoropolyether alcohol HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _p (CF ₂ O) _q CF ₂ CH ₂ OH C ₁₈ H ₃₇ OH ── ────────────────────────────── Lubricant Perfluoropolyether / Alcohol (molar ratio) ──────── ──────────────────────── Example 28 0.005 Example 29 0.01 Example 30 0.1 Example 31 0.3 Example 32 0.5 Example 33 1.0 Example 34 3.0 Example 35 5.0 Example 36 10 Example 37 30 Example 38 100 Example 39 110 Example 40 120 Comparative Example 4 Perfluoropolyether only ──────────────── ───────────────

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

As is apparent from the above description, the magnetic recording medium of the present invention contains perfluoropolyether having a hydroxyl group at the terminal and a long-chain hydrocarbon having a hydroxyl group in the molecule (especially 0.01 mole ratio). Since it has the added lubricant, the lubricity can be maintained under any use condition, and the lubricity can be maintained for a long time.
Therefore, the magnetic recording medium of the present invention is excellent in running property, wear resistance and durability.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a magnetic recording medium of the present invention.

[Explanation of symbols]

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

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area C10N 30:06 40:18

Claims (3)

[Claims] 1. A lubricant comprising a perfluoropolyether having a hydroxyl group at the terminal and a long-chain hydrocarbon having a hydroxyl group in the molecule. 2. A perfluoropolyether having a hydroxyl group at the terminal and a long-chain hydrocarbon having a hydroxyl group in the molecule, wherein the ratio of the long-chain hydrocarbon to the perfluoropolyether (perfluoropolyether / long Lubricants whose chain hydrocarbons) are in a molar ratio of 0.01-100. 3. A magnetic recording medium having at least a magnetic layer on a non-magnetic support, the magnetic recording medium containing the lubricant according to claim 1.