JPH1196543A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent lubricating effect by holding a lubricant com prising a nitrile in a magnetic layer on a nonmagnetic supporting body. SOLUTION: Relating to a magnetic recording medium having a carbon film on a magnetic layer, a lubricant comprising a nitrile is applied on the carbon film by coating. When a nitrile is applied as a lubricant on the carbon film, the cyano group as a polar group of the lubricant is adsorbed on the carbon film while aggregation force between long-chain hydrocarbon groups in the hydrophobic part causes to form a lubricant film. Therefore, by holding the nitrile as a lubricant, excellent lubricating property is kept for a long time under various use conditions, and the lubricating property is kept for a long time. The lubricant has a small coefft. of friction and shows excellent travelling property, wear resistance and durability. As the nitrile, a compd. expressed by R-CN (wherein R is a hydrophobic functional group) is preferably used.

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.

[0002]

2. Description of the Related Art For example, a so-called metal magnetic 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 a magnetic layer is used, In a so-called coating type magnetic recording medium in which a magnetic coating material containing a binder and a resin binder is applied on a non-magnetic support and this is used as a magnetic layer, the surface of the magnetic layer is extremely smooth to improve the electromagnetic conversion characteristics. Because of this, a substantial contact area with a sliding member such as a magnetic head or a guide roller is large, so that a friction coefficient is large, and an adhesion phenomenon (so-called sticking) is likely to occur, and the running property and durability are lacking. There are many problems.

[0003] In order to solve these problems, use of various lubricants has been studied. Conventionally, higher fatty acids and esters thereof have been internally added to the magnetic layer of the magnetic recording medium. Alternatively, attempts have been made to suppress the coefficient of friction by top coating.

[0004]

By the way, lubricants used for magnetic recording media are required to have very strict characteristics due to their properties, and it is difficult for conventional lubricants to respond. It is.

[0005] Lubricants used in magnetic recording media include (1) excellent low-temperature characteristics so as to ensure a predetermined lubricating effect when used in cold regions, and (2) lubricants for magnetic heads. Since pacing poses a problem, it is required that the coating be able to be applied extremely thinly and that sufficient lubrication properties be exhibited even in such a case, and (3) that it can withstand long-term use or long-term use and that the lubrication effect be maintained. Is done.

However, it is difficult to say that lubricants such as higher fatty acids and esters thereof sufficiently satisfy the performance required for the above-mentioned lubricants. Due to the lack of capacity, they are dissatisfied with the practical characteristics such as the level reduction of the reproduction output in the shuttle running test.

Accordingly, the present invention provides a magnetic recording medium which maintains excellent lubricity under various use conditions, maintains a lubricating effect for a long time, and exhibits excellent running properties, abrasion resistance and durability. It is intended to provide.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies on achieving the above object, and as a result, a magnetic recording medium comprising at least a magnetic layer on a nonmagnetic support, This magnetic recording medium is provided with a nitrile
It has been found that an excellent lubricating effect can be obtained by holding the same as a lubricant, and the present invention has been completed.

That is, the present invention provides a magnetic recording medium having a magnetic layer on a nonmagnetic support, wherein a lubricant made of nitrile is held (hereinafter referred to as a magnetic recording medium of the present invention). Media).

According to the magnetic recording medium of the present invention, since nitrile is retained as a lubricant, excellent lubricity is maintained under various use conditions, a lubricating effect is maintained for a long time, and a friction coefficient is maintained. Small, and can exhibit excellent running properties, wear resistance, and durability.

That is, the nitrile according to the present invention has a cyano group (-CN) as a polar group (hydrophilic group), which adheres to a hydrophilic surface such as a magnetic powder or a protective film to cause friction. It is considered that the reduction of the coefficient is realized, and the still traveling performance and the shuttle traveling performance are further improved.

In particular, the nitrile has a lower acidity than a highly polar group such as a carboxyl group, is strongly adsorbed on the hydrophilic surface, and has a reduced friction coefficient and improved still running performance and shuttle running performance. It is a lubricant that is compatible with both.

Further, while the conventional fluorine-containing lubricant is soluble only in a fluorine-based solvent and can only be coated using this solvent, the above-mentioned lubricant made of nitrile is used in a hydrocarbon-based lubricant such as toluene and acetone. It can be dissolved in a solvent, and the load on the environment is small in terms of solvent treatment.

[0014]

According to the present invention, in a magnetic recording medium having a carbon film (carbon film) provided on the magnetic layer, the lubricant comprising the nitrile is provided on the carbon film by coating. Is desirable.

When the above-mentioned nitrile is applied as a lubricant on a carbon film, a cyan group, which is a polar group of the nitrile, is adsorbed on the carbon film and lubricated by a cohesive force between hydrophobic groups such as long-chain hydrocarbon groups. Form a film.

In particular, according to the pH measurement, for example, a polar group site (such as a hydroxyl group or a carboxyl group) on the surface of a carbon film formed by sputtering a carbon film,
= Approximately 2, which is a very acidic surface.

However, since nitrile has low acidity, it is considered that the above-mentioned adsorption property to the carbon film surface is excellent. Therefore, by strongly adsorbing on the carbon film surface, it can be applied extremely thinly, and in this case, sufficient lubricating properties are exhibited. Further, the lubricating effect can be maintained, the friction coefficient is reduced, and the shuttle durability is reduced. And still durability can be improved.

The carbon film (carbon film) may be formed by a physical film forming method (PVD method) such as a sputtering method, or may be formed by a chemical vapor deposition (CVD) method using a hydrocarbon gas. Method). Further, the carbon film may be a hard carbon film or an amorphous carbon film in which a diamond structure and a graphite structure are mixed, which is called diamond-like carbon.

In the magnetic recording medium of the present invention, the nitrile is preferably a compound represented by the following general formula 1. General formula 1: R-CN (However, in the above general formula 1, R is a hydrophobic functional group.)

That is, in the nitrile having such a structure, the cyan group acts as a polar (hydrophilic) group, and R acts as a hydrophobic group.

In the magnetic recording medium of the present invention, the hydrophobic functional group (long-chain hydrocarbon group) represented by R is preferably a group represented by the following general formula A. General formula A: CH ₃ (CH ₂ ) ₁ — or CH ₃ (CH ₂ ) _m CH (C
H ₃ (CH ₂ ) _n ) (CH ₂ ) _p − (where, in the general formula A, 1, m, n and p are integers selected from the following ranges. L = 3 to 28, m = 3 ~ 28, n = 1 ~ 28, p = 0 ~
15)

In the general formula A, l, m, n
And p are more preferably integers selected from the following ranges. l = 6 to 21, m = 6 to 21, n = 1 to 17, p = 0
10

That is, in the case of the long-chain hydrocarbon group of the hydrophobic functional group site in the nitrile, if the carbon number is 6 or more, the alkyl group has an appropriate alkyl group length, and the durability against friction and wear is improved. When the carbon number is 22 or less, the solubility of the nitrile lubricant in the solvent is good.

In the present invention, a carbon film is provided on the magnetic layer, and when a lubricant made of nitrile is applied on the carbon film, the amount of the lubricant applied is 0.5 to 100 mg / m 2. Desirably ² .

If the coating amount is less than 0.5 mg / m ² , the performance of the lubricant cannot be sufficiently exhibited,
On the other hand, if it exceeds 100 mg / m ² , the amount of the lubricant may become too large and the friction coefficient may be increased.

In the magnetic recording medium of the present invention, the magnetic layer may be a metal magnetic thin film type magnetic recording medium comprising a metal magnetic thin film.

In general, in a magnetic recording medium of a so-called metal magnetic thin film type in which a ferromagnetic metal material is deposited on a non-magnetic support by a method such as vapor deposition and a magnetic layer is used, the magnetic layer is formed by depositing a magnetic material. In addition, since no binder is used in the magnetic layer, the magnetic layer is vulnerable to the sliding operation. To compensate for this, a protective film such as a carbon film is provided.

The lubricant according to the present invention can be applied very thinly on such a protective film, and in this case, sufficient lubricating properties can be exhibited, and the lubricant can withstand long-term use. The obtained lubrication effect can be maintained.

Hereinafter, a configuration example of the magnetic recording medium of the present invention will be described in more detail.

The magnetic recording medium to which the present invention is applied can be applied to a so-called metal thin film type magnetic recording medium in which a magnetic film is formed as a magnetic layer on the surface of a nonmagnetic support by a method such as vapor deposition. is there. Further, a carbon film may be formed as a protective film on the magnetic layer. The metal thin film type magnetic recording medium may have a configuration in which an underlayer is interposed between the nonmagnetic support and the magnetic layer.

In this case, the non-magnetic support and the metal magnetic thin film are not limited at all without departing from the gist of the present invention, and any conventionally known ones can be used.

As an example, the same non-magnetic support as that of the coating type magnetic recording medium can be used. When a rigid substrate such as an Al alloy plate or a glass plate is used for the nonmagnetic support, an oxide film such as alumite treatment or a Ni-P film is formed on the surface of the substrate, and the surface is hardened. 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, Ni or the like.
Ni-based alloy, Co-Pt-based alloy, Co-Pt-Ni-based alloy, Fe-Co-based alloy, Fe-Ni-based alloy, Fe-Co
-Ni-based alloy, Fe-Ni-B-based alloy, Fe-Co-B
An in-plane magnetization recording metal magnetic thin film or a Co-Cr alloy thin film made of a base alloy, a Fe-Co-Ni-B alloy, or the like is exemplified.

In particular, in the case of an in-plane magnetization recording metal magnetic thin film,
Bi, Sb, Pb, Sn, Ga,
A base layer of a low-melting non-magnetic material such as In, Ge, Si, or Tl is formed, and a metal magnetic material is vapor-deposited or sputtered from a vertical direction to diffuse the low-melting non-magnetic material into the metal magnetic thin film. Orientation may be eliminated to ensure in-plane isotropy and also to improve coercivity.

As a method for forming a protective film, especially a carbon film on the surface of such a magnetic recording medium, sputtering is generally used, but the method is not particularly limited, and any method can be used. In this case, the thickness of the protective film is 2 to 10
0 nm, more preferably 5 to 30 nm.
nm.

As a method for retaining the lubricating film structure on a protective film, particularly a carbon film, on the surface of a magnetic recording medium, a solution in which the nitrile is dissolved in a solvent such as toluene or acetone is used. And a method of top-coating. In this case, the coating amount of the lubricant, it is preferably a 0.5 to 100 mg / m ^2, more preferably 1 to 20 mg / m ^2.

The above-mentioned lubricant may be used together with a rust preventive, if necessary.

As the rust preventive, any rust preventive can be used as long as it is generally used as a rust preventive for this type of magnetic recording medium. Examples thereof include phenols, naphthols, quinones and heterocycles containing a nitrogen atom. Examples include a formula compound, a heterocyclic compound containing an oxygen atom, and a heterocyclic compound containing a sulfur atom.

This rust preventive may be used in combination with the above-mentioned lubricant. However, after a rust preventive layer is applied on the carbon film, a lubricant layer is applied. The effect is high if formed separately.

The magnetic recording medium to which the present invention is applied is a so-called coating type magnetic material in which a magnetic paint containing fine magnetic particles and a resin binder is applied on a non-magnetic support, and this is used as a magnetic layer. It may be a recording medium.

The magnetic particles are preferably ferromagnetic powders, for example, γ-Fe ₂ O ₃ and Co-containing γ-Fe
Oxide magnetic powders such as ₂ O ₃ , Co-coated γ-Fe ₂ O ₃ , CrO ₂ , ferrites represented by magnetite,
Further, for example, Fe-Al based, Fe-Al-Ni based, F
e-Al-Ca system, Fe-Al-Co system, Fe-Al-
Zn-based, Fe-Al-Co-based, Fe-Ni-based, Fe-N
i-Si-Al-Mn system, Fe-Ni-Si-Al-Z
As in the case of n-based, Fe-Mn-Zn-based, and Ni-Co-based alloy powders, metal magnetic powders mainly containing Fe, Co, Ni, and the like can be used.

The binder is typically a polyester resin, a polyurethane resin, or a vinyl chloride resin such as a vinyl chloride copolymer. Further, for the purpose of improving the dispersibility of these binders magnetic powder to the resin, these _{resins, -SO 3 M, -OSO 3 M} , -CO
OM, -PO (OM ') ₂ (where M is Na, K, Li
And M ′ is a hydrogen atom or an alkali metal or an alkyl group. ) And at least one polar group selected from sulfopetine groups as a repeating unit.

The magnetic layer composed of the binder and the magnetic powder may contain known additives such as abrasives, lubricants, hardeners, and antistatic agents.

As the non-magnetic support used for the above-described metal magnetic thin film type magnetic recording medium and coating type magnetic recording medium, known materials can be appropriately used, for example, polyethylene terephthalate, polyethylene naphthalate, etc. Polyesters, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, aramid resins such as polyaramid, and plastics such as polycarbonate.

These non-magnetic supports may have a single-layer structure or a multi-layer structure. Further, a corona discharge treatment or the like may be performed. Further, it can be formed into any shape such as a film, a sheet, a disk, and a card.

Although the preferred embodiment of the magnetic recording medium of the present invention has been described above, the present invention is not limited to the above-described embodiment.

For example, when a coating type magnetic recording medium is used as the magnetic recording medium of the present invention, a predetermined amount of the lubricant may be contained in a magnetic layer comprising a magnetic powder and a binder. The lubricant may be applied on the magnetic layer with or without a protective film. When the lubricant is contained in the magnetic layer of the coating type magnetic recording medium, the content is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the magnetic powder.

When a magnetic recording medium of the metal magnetic thin film type is used as the magnetic recording medium of the present invention, it is preferable to coat the magnetic recording medium on a carbon film as described above. Alternatively, it may be applied indirectly.

Further, in addition to the above-described carbon film, a quartz (SiO ₂ ) film, a zirconia (ZrO ₂ ) film, or the like may be used as the protective film.

Further, in the magnetic recording medium of the present invention,
A back coat layer may be provided on the surface of the non-magnetic support on which the magnetic layer is not provided. This back coat layer can be formed according to a usual method. Further, the lubricant may be internally added or applied to the back coat layer.

[0051]

EXAMPLES The present invention will be described below with reference to specific examples, but it goes without saying that the present invention is not limited to these examples.

Examples 1 to 23 Using a compound having the composition shown in Table 1 below as a lubricant composed of a nitrile, a metal magnetic thin film type magnetic recording medium having the following structure was prepared.

<Preparation Example of Sample Tape> A 100-nm-thick ferromagnetic metal thin film was formed by applying a Co—Ni alloy to a 10 μm-thick polyethylene terephthalate film by an oblique vapor deposition method. A film in which a carbon film having a thickness of 15 nm was formed by sputtering was cut into a width of 8 mm to obtain a sample tape.

In Examples 1 to 23, Compounds 1 to 23 having the composition shown in Table 1 as a lubricant were dissolved in a toluene solvent, and then applied to the sample tapes to prepare samples. The amount of the lubricant applied is 1
0 mg / m ² (film thickness 5 to 10 nm).

FIG. 1 shows a schematic sectional view of the magnetic tape thus produced. That is, the magnetic recording medium of this embodiment is a magnetic recording medium 5 in which a magnetic layer 3, a carbon film 4, and a lubricant layer 1 are sequentially provided on a nonmagnetic support 2.

The conditions of (1) when the temperature was 25 ° C. and the humidity was 60%, (2) when the temperature was 40 ° C. and when the humidity was 80%, and (3) when the temperature was −5 ° C. The lower coefficient of friction, still durability, and shuttle durability were measured. In addition, the still durability evaluated the decay time of the output in the pause state to -3 dB.
The shuttle durability was evaluated by the number of shuttles in which the shuttle traveled for 2 minutes each time and the output decreased by -3 dB.

From Table 2, it can be seen that the magnetic recording medium of the present invention has a friction coefficient, still durability, shuttle durability, etc. by forming a carbon film on the surface of the magnetic layer and using nitrile as a lubricant. It can be seen that very good results can be obtained without deterioration even under various conditions.

Comparative Examples 1 to 10 Sample tapes having the same constitution as those of the examples were prepared, and Compounds 24 to 28 having the compositions shown in Table 3 below were applied to the sample tapes to obtain samples. The amount of the lubricant applied was 10 mg / m ² (film thickness 5 to 10 nm).
Comparative Examples 1 to 5 are sample tapes using higher fatty acids as lubricants, and Comparative Examples 6 to 10 are sample tapes using fatty acid esters.

The friction coefficient, still durability and shuttle durability of each of the samples thus prepared were measured under various conditions in the same manner as in the examples. The measurement results are shown in Table 4 below.

From Table 4, it was found that the sample tapes using higher fatty acids as the lubricant (Comparative Examples 1 to 5) had a temperature of 25.
When the temperature is 60 ° C. and the humidity is 60%, relatively excellent friction coefficient, still durability, and shuttle durability are obtained, but as the usage conditions become more severe, the still durability and shuttle durability in particular decrease.

The sample tapes using fatty acid esters as lubricants (Comparative Examples 6 to 10) have a large coefficient of friction under any conditions, have problems in running properties, and have still durability, shuttle durability, Both durability are insufficient.

Table 1A (Nitrile composition)

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[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073]

According to the magnetic recording medium of the present invention, since nitrile is retained as a lubricant, excellent lubricity is maintained under various use conditions, and the lubricating effect is maintained for a long time. It has a small coefficient of friction and can exhibit excellent running properties, wear resistance and durability.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part of a magnetic recording medium according to an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Lubricant layer, 2 ... Nonmagnetic support, 3 ... Magnetic layer 4 ... Carbon film, 5 ... Magnetic recording medium

Continued on the front page (72) Inventor Kenichi Kurihara 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (6)

[Claims] 1. A magnetic recording medium having a magnetic layer on a nonmagnetic support, wherein a lubricant made of nitrile is held. 2. The magnetic recording medium according to claim 1, wherein a carbon film is provided on the magnetic layer, and the lubricant is applied on the carbon film. 3. The magnetic recording medium according to claim 1, wherein the nitrile is represented by the following general formula 1. General formula 1: R-CN (However, in the above general formula 1, R is a hydrophobic functional group.) 4. The magnetic recording medium according to claim 3, wherein the hydrophobic functional group represented by R is represented by the following general formula A. General formula A: CH ₃ (CH ₂ ) ₁ — or CH ₃ (CH ₂ ) _m CH (C
H ₃ (CH ₂ ) _n ) (CH ₂ ) _p − (where, in the general formula A, 1, m, n and p are integers selected from the following ranges. L = 3 to 28, m = 3 ~ 28, n = 1 ~ 28, p = 0 ~
15) 5. The coating amount of the lubricant is 0.5 to 100 m.
^{3. The} magnetic recording medium according to claim ^2, which has a g / m ² . 6. The magnetic recording medium according to claim 1, wherein said magnetic layer comprises a metal magnetic thin film.