JPH08102048A - Magnetic recording media - Google Patents

Abstract

(57) [Summary] [Purpose] Excellent lubricity is maintained under various operating conditions, and especially under low temperature conditions (0 ° C or less), the lubrication effect is maintained for a long time, and running and wear resistance are improved. A magnetic recording medium having excellent durability and the like is provided. In a magnetic recording medium in which at least a magnetic layer is formed on a non-magnetic support, a carbon film is provided on the magnetic layer and at least 1 is used as a lubricant.
An amphipathic compound with one long chain branched alkyl group is used. As the amphipathic compound, a compound in which the hydrophobic group of the long-chain branched alkyl group has a structure represented by the following formula (1) is suitable. [CH ₃ (CH _{2) x] 2 CH (CH 2) y ─} ··· (1) where, in equation (1), x = 1~21, y = 1~21 ,
x + y = 10 to 30.

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 improvement of a lubricant.

[0002]

2. Description of the Related Art For example, a ferromagnetic metal material is deposited on a non-magnetic support by a method such as vapor deposition and used as a magnetic layer.
In a so-called metal magnetic thin film type magnetic recording medium or a so-called coating type magnetic recording medium in which a magnetic coating material containing very fine magnetic particles and a resin binder is coated on a non-magnetic support and used as a magnetic layer , Because the surface of the magnetic layer is extremely smooth,
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 apt to occur, which causes problems such as lack of running property and durability. Many.

Therefore, in order to improve these problems,
The use of various lubricants has been studied, and it has hitherto been attempted to suppress the coefficient of friction by internally adding, for example, a higher fatty acid or its ester to the magnetic layer of the magnetic recording medium or by top coating. However, in the lubricant used for the magnetic recording medium,
Due to its properties, very strict characteristics are required, and it is the current situation that it is difficult for conventional lubricants to comply.

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) with a magnetic head. Spacing is a problem, so it must be applied very thinly, and in this case, sufficient lubrication characteristics must be exhibited, and (3) long-term or long-term use and continuous lubrication effect are required. To be done.

[0005]

As described above, in the field of magnetic recording media, the friction coefficient increases particularly under low temperature conditions (0 ° C. or less) due to the lack of the ability of the lubricant used. Is dissatisfied with practical characteristics such as running performance.

Therefore, the present invention has been proposed in view of the above circumstances, and excellent lubricity is maintained under various usage conditions, and particularly under low temperature conditions (0 ° C. or less) for a long time. It is an object of the present invention to provide a magnetic recording medium which has a long-lasting lubrication effect and is excellent in running property, wear resistance, durability and the like.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies as a result of achieving the above-mentioned object, and as a result, parents having at least one long-chain branched alkyl group on a carbon film formed on a magnetic layer. The inventors have found that the friction coefficient can be reduced especially under low temperature conditions (0 ° C. or less) by applying the medium compound as a lubricant, and have completed the present invention.

That is, the magnetic recording medium of the present invention is a magnetic recording medium in which at least a magnetic layer is formed on a non-magnetic support, and a carbon film is formed on the magnetic layer, and at least one magnetic layer is formed. It is characterized in that it has an amphipathic compound having a chain-branched alkyl group as a lubricant.

In the magnetic recording medium of the present invention, a metallic magnetic thin film formed by a method such as vapor deposition is formed as a magnetic layer on a non-magnetic support, and a carbon film is further formed on this magnetic layer. It will be.

Between the magnetic layer and the non-magnetic support,
It may be configured to have an intermediate layer as a so-called undercoat layer.

A back coat layer may be provided on the surface of the non-magnetic support opposite to the surface on which the magnetic layer is formed, for the purpose of improving the running property of the magnetic recording medium, preventing charging, and preventing transfer. good.

In the present invention, an amphipathic compound having at least one long-chain branched alkyl group is used as a lubricant on the carbon film formed on the magnetic layer.
As a result, excellent lubricity is obtained under various usage conditions, and the lubrication effect is maintained for a long time, especially under low temperature conditions (0 ° C or less), and the running properties, wear resistance, durability, etc. are improved. Can be planned.

The above-mentioned long-chain branched alkyl group refers to a chain alkyl group which is not a long chain and preferably has 12 to 32 carbon atoms. This long-chain branched alkyl group has 1 carbon atom
When it is less than 2, the alkyl group length is too short, and sufficient abrasion resistance and durability cannot be ensured. On the contrary, when it is more than 32, it becomes a solvent for retaining the lubricant on the medium surface. The solubility may decrease, and it may be difficult to form a good coating film.

The long-chain branched alkyl group preferably has a hydrophobic group moiety having a structure represented by the following formula (1).

[CH ₃ (CH ₂ ) _x ] ₂ CH (CH ₂ ) _y- (1) However, in the above formula (1), x = 1 to 21, y = 1 to 21,
x + y = 10 to 30.

A long-chain alkyl group may be introduced into the amphipathic compound. The long-chain alkyl group preferably has 13 to 21 carbon atoms. When the carbon number of the long-chain alkyl group is less than 13, the alkyl group length is too short, and sufficient abrasion resistance and durability cannot be secured. On the contrary, when the carbon number of the long-chain alkyl group is larger than 21, the interaction between the long-chain alkyl groups is increased, and as a result, the cohesive force between the chains is increased and the melting point in bulk is increased. Therefore, the wear resistance and durability under the originally obtained low temperature condition (0 ° C. or less) are lost.

Examples of the hydrophilic group of the amphipathic compound include those represented by the following structural formulas (2) to (5).

[0018] R-COOH (carboxylic acid) ··· (2) R-NH 2 ( amine) ··· (3) R-COO - · H 3 N + -R '( carboxylic acid amine salt) ... (4) R-COO-R '(ester) ... (5) In the structural formulas (2) to (5), R and R'represent a long-chain branched alkyl group or a long-chain alkyl group. However, in the case of two, at least one is a long-chain branched alkyl group. In the magnetic recording medium of the present invention, the nonmagnetic support and the magnetic metal thin film forming the magnetic layer are not limited in any way, and any conventionally known material can be used.

As a specific example, as the non-magnetic support, polyethylene terephthalate, polyethylene-
Polyesters such as 2,6-naphthalate, polyolefins such as polypropylene, celluloses such as cellulose triacetate and cellulose diacetate, polymeric materials such as vinyl resins, polyimides and polycarbonates, aluminum alloys, Examples thereof include a metal plate made of a titanium alloy or the like, a support formed of glass, ceramics, or the like. Here, 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 an alumite treatment or a Ni-P film is formed on the surface of the substrate to harden the surface. It may be done. The form is not limited at all,
It may be in any form such as a tape form, a sheet form and a drum form. Further, this non-magnetic support may be subjected to a surface treatment so that fine irregularities are formed in order to control its surface property.

As the metal magnetic thin film, any film can be used as long as it is formed as a continuous film by PVD method such as plating, sputtering and vacuum deposition method, for example, Fe, Co, N.
metal such as i, Co-Ni alloy, Co-Pt alloy,
Co-Pt-Ni based alloy, Fe-Co based alloy, Fe-N
In-plane magnetization recording metal magnetic thin film made of i-based alloy, Fe-Co-Ni-based alloy, Fe-Ni-B-based alloy, Fe-Co-B-based alloy, Fe-Co-Ni-B-based alloy, etc., Co -C
Examples include r-based alloy films.

In particular, in the case of an in-plane magnetization recording metal magnetic thin film,
Bi, Sb, b, Sn, Ga, I on the non-magnetic support in advance
An underlayer of a low-melting point non-magnetic material such as n, Ge, Si, or Tl is formed in advance, a magnetic metal material is vapor-deposited or sputtered from the vertical direction, and the low-melting point non-magnetic material is diffused in the metal magnetic thin film. The orientation may be eliminated to secure the in-plane isotropic property, and the coercive force may be improved.

A carbon film is formed on the surface of the magnetic recording medium. Sputtering is generally used as a method for forming the carbon film, but the method is not particularly limited to this, and any other method can be used.

The carbon film has a thickness of 2 to 100 nm.
Is preferable, and more preferably 5 to 30 nm.

As a method of retaining the lubricant on such a carbon film, there is a method of top-coating the surface of the carbon film with the lubricant. In this case, the applied amount of the lubricant is 0.5 to 100 mg.
It is preferably a / m ^2, and more preferably 1 to 20 mg / m ^2.

The above lubricant may be used in combination with a rust preventive, 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. For example, phenols, naphthols,
Examples thereof include quinones, heterocyclic compounds containing a nitrogen atom, heterocyclic compounds containing an oxygen atom, and heterocyclic compounds containing a sulfur atom.

This rust preventive may be used in combination with the above lubricant, but after the rust preventive agent layer is formed by coating on the carbon film, the lubricant is applied to form the lubricant layer. As described above, it is more effective if the layers are formed in two or more layers.

[0028]

The use of an amphipathic compound having at least one long-chain branched alkyl group (non-linear chain alkyl group) as a lubricant retained on the surface of the carbon film provided on the magnetic layer is preferable. The lubricating effect is exhibited and the friction coefficient is reduced. Further, the mobility of the alkyl group in the film made of the lubricant is maintained even under low temperature conditions, and the lubricating action is not impaired even under such severe conditions. Therefore, even under low temperature conditions (0 ° C. or lower), a friction coefficient equivalent to that under normal temperature conditions (about 20 ° C.) can be maintained. Under such low temperature conditions (0 ° C or less)
The coefficient of friction in is lower when using an amphipathic compound having at least one long-chain branched alkyl group as the lubricant than when using an amphipathic compound having only a linear alkyl group.

[0029]

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.

Examples 1 to 10 In this example, a metal is formed by coating a lubricant layer made of an amphipathic compound represented by the following structural formula (6) on a carbon film provided on a magnetic layer. It is an example of a magnetic thin film type magnetic recording medium.

R ₁ —COO ⁻ · H ₃ N ⁺ —R ₂ (6) However, in the above formula (6), R ₁ is [CH ₃ (CH ₂ ) _x ].
_{2 CH (CH 2) y ─} , R 2 represents respectively CH ₃ (CH _{2) z} ─ a. Here, x and y were changed as shown in Table 1 below.

[0032]

[Table 1]

First, a Co-Ni alloy film was deposited on a polyethylene terephthalate film having a thickness of 10 μm by an oblique vapor deposition method to form a magnetic layer made of a ferromagnetic metal thin film having a thickness of 150 nm.

Next, a carbon film having a film thickness of 10 nm is formed on the magnetic layer by sputtering, and then a carbon film having a thickness of 8 m is formed.
A sample tape was obtained by cutting into m width.

Subsequently, a lubricant layer was formed by coating the surface of the sample tape, that is, the carbon film, using the above-mentioned amphipathic compound.

Comparative Examples 1 to 4 The amphipathic compound used as the lubricant in the above Example 1 was changed to the compound represented by the following structural formula (7),
Others were formed into a tape by the same method as in Example 1 to prepare a comparative tape.

R ₃ —COO ⁻ · H ₃ N ⁺ —R ₃ (7) However, in the above formula (7), R ₃ represents CH ₃ (CH ₂ ) _p −. Here, p was changed as shown in Table 2 below.

[0038]

[Table 2]

Therefore, with respect to the sample tape and the comparative tape produced as described above, the temperature is 25 ° C. and the humidity is 60.
%, Temperature -5 ° C and temperature 40 ° C, humidity 80%
At that time, the friction coefficient, the still durability and the shuttle durability were measured.

Still durability is the output of the pause state.
It was evaluated by the decay time up to 3 dB.

The shuttle durability was evaluated by the number of shuttles until the output decreased by 3 dB after the shuttle traveled for 2 minutes each time.

The results are shown in Table 3 below.

[0043]

[Table 3]

As shown in Table 3, by forming a carbon film on the surface of the magnetic layer and using an amphipathic compound having a long-chain branched alkyl group (non-linear chain alkyl group) as a lubricant, It was found that the friction coefficient, still durability and shuttle durability did not deteriorate even under severe conditions such as low temperature low humidity or high temperature high humidity, and that very good results were obtained.

[0045] changing the amphiphilic compound used as a lubricant in the Examples 11 to 20 Example 1 to the compounds represented by the following structural formula (8),
Others were taped by the same method as in Example 1 to prepare a sample tape.

R ₁ —COO—R ₂ (8) However, in the above formula (8), R ₁ is [CH ₃ (CH ₂ ) _x ].
_{2 CH (CH 2) y ─} , R 2 is CH ₃ (CH ₂₎ represents the _z ─. Here, x and y were changed as shown in Table 4 below.

[0047]

[Table 4]

Comparative Examples 5 to 8 The amphipathic compound used as the lubricant in the above Example 1 was changed to the compound represented by the following structural formula (9),
Others were formed into a tape by the same method as in Example 1 to prepare a comparative tape.

R ₃ —COO—R ₃ (9) However, in the above formula (9), R ₃ represents CH ₃ (CH ₂ ) _p −. Here, p was changed as shown in Table 5 below.

[0050]

[Table 5]

Then, the coefficient of friction, the still durability and the shuttle durability of the sample tape and the comparative tape were examined in the same manner as described above.

The results are shown in Table 6 below.

[0053]

[Table 6]

As shown in Table 6, by forming a carbon film on the surface of the magnetic layer and using an amphipathic compound having a long-chain branched alkyl group (non-linear chain alkyl group) as a lubricant, It was found that the friction coefficient, still durability and shuttle durability did not deteriorate even under severe conditions such as low temperature low humidity or high temperature high humidity, and that very good results were obtained.

Examples 21 to 30 Tapes were prepared in the same manner as in Example 1 except that the amphipathic compound used as the lubricant in Example 1 was replaced by the compound represented by the following structural formula (10). Then, a sample tape was produced.

R ₁ —COOH (10) However, in the above formula (10), R ₁ is [CH ₃ (C
H _{2) x] 2} CH (CH ₂₎ represents the _y ─. Where x,
y was changed as shown in Table 7 below.

[0057]

[Table 7]

Comparative Examples 9 to 12 Tapes were prepared in the same manner as in Example 1 except that the amphipathic compound used as the lubricant in Example 1 was replaced by the compound represented by the following structural formula (11). Was performed to prepare a comparative tape.

R ₃ —COOH ₃ N—R ₃ (11) However, in the above formula (11), R ₃ is CH ₃ (CH ₂ ) _p
Represents Here, p was changed as shown in Table 8 below.

[0060]

[Table 8]

Then, the friction coefficient, the still durability and the shuttle durability of the sample tape and the comparative tape were examined in the same manner as described above.

The results are shown in Table 9 below.

[0063]

[Table 9]

As shown in Table 9, by forming a carbon film on the surface of the magnetic layer and using an amphipathic compound having a long-chain branched alkyl group (non-linear chain alkyl group) as a lubricant, It was found that the friction coefficient, still durability and shuttle durability did not deteriorate even under severe conditions such as low temperature low humidity or high temperature high humidity, and that very good results were obtained.

Examples 31 to 40 Tapes were prepared in the same manner as in Example 1 except that the amphipathic compound used as the lubricant in Example 1 was replaced by the compound represented by the following structural formula (12). Then, a sample tape was produced.

R ₁ —NH ₂ (12) However, in the above formula (12), R ₁ is [CH ₃ (C
H _{2) x] 2} CH (CH ₂₎ represents the _y ─. Where x,
y was changed as shown in Table 10 below.

[0067]

[Table 10]

Comparative Examples 13 to 16 Tapes were prepared in the same manner as in Example 1 except that the amphipathic compound used as the lubricant in Example 1 was replaced by the compound represented by the following structural formula (13). Was performed to prepare a comparative tape.

R ₂ —NH ₂ (13) However, in the above formula (13), R ₂ is CH ₃ (CH ₂ ) _p
Represents Here, p was changed as shown in Table 11 below.

[0070]

[Table 11]

Then, the friction coefficient, the still durability and the shuttle durability of the sample tape and the comparative tape were examined in the same manner as described above.

The results are shown in Table 12 below.

[0073]

[Table 12]

As shown in Table 12, by forming a carbon film on the surface of the magnetic layer and using an amphipathic compound having a long chain branched alkyl group (non-linear chain alkyl group) as a lubricant, It was found that the friction coefficient, still durability and shuttle durability did not deteriorate even under severe conditions such as low temperature low humidity or high temperature high humidity, and that very good results were obtained.

[0075]

As is apparent from the above description, in the magnetic recording medium of the present invention, a carbon film is formed on the magnetic layer and an amphipathic property having at least one long-chain branched alkyl group as a lubricant is provided. Since the compound is used, good lubricating performance can be maintained under any conditions (especially low temperature of 0 ° C. or lower), and the lubricating performance can be maintained for a long time. Therefore, according to the present invention,
It is possible to provide a magnetic recording medium that can obtain good running stability and running durability even under severe conditions.

Claims (3)

[Claims] 1. A magnetic recording medium in which at least a magnetic layer is formed on a non-magnetic support, a carbon film is formed on the magnetic layer, and an amphiphile having at least one long-chain branched alkyl group. A magnetic recording medium containing a hydrophilic compound as a lubricant. 2. The magnetic recording medium according to claim 1, wherein the hydrophobic group of the long-chain branched alkyl group has a structure represented by the following formula (1). [CH ₃ (CH _{2) x] 2 CH (CH 2) y ─} ··· (1) where, in equation (1), x = 1~21, y = 1~21 ,
x + y = 10 to 30. 3. The hydrophilic group of the amphipathic compound is a carboxylic acid R—COOH (R represents a long-chain branched alkyl group or a long-chain alkyl group. The same applies hereinafter, provided that in the case of two, at least one is a long-chain. A branched alkyl group), amine R-
NH _2, carboxylic acid amine salt _{^{R-COO - · H 3 N}} + -
R '(R' represents a long-chain branched alkyl group or a long-chain branched alkyl group. The same applies hereinafter, provided that at least one of the two is a long-chain branched alkyl group.) Or ester R-CO.
3. The magnetic recording medium according to claim 1, which is at least one of OR.