JP3336801B2 - 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 holding a lubricant for ensuring running durability.

[0002]

2. Description of the Related Art In general, a magnetic recording medium, especially a magnetic tape, slides at a high speed with a magnetic head in the process of writing / reading a magnetic signal. Must be done. However, since the surface of the magnetic layer of the magnetic recording medium is smoothed for high-density recording, a substantial contact area with a sliding member such as a magnetic head or a guide roller is increased, and the At times, the coefficient of friction between the magnetic recording medium and the sliding member increases, causing an adhesion phenomenon (so-called sticking).
It is easy to cause. In particular, in the case of 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 used as a magnetic layer, the surface smoothness of the magnetic layer is extremely good. Therefore, the problem associated with the increase in the friction coefficient as described above is likely to occur.

For example, in an 8 mm video deck,
A magnetic tape is wound around a drum along ten or more guide pins, and a tension of about 20 g and a traveling speed of about 0.5 g are applied to the magnetic tape by a pinch roller and a capstan.
Run while maintaining m / s. In this traveling system, the magnetic layer of the magnetic tape is configured to come into contact with the guide pins made of stainless steel, so that when the coefficient of friction between the magnetic tape and the guide pins increases, the magnetic tape causes stick slip, A phenomenon called tape squeal occurs. Then, for example, if this tape squeals occurs during the reproduction operation, the reproduction screen becomes tight.

In the pause state, the magnetic head slides at a high speed in the same area of the magnetic tape. Therefore, when the friction coefficient increases, the magnetic layer is worn and the reproduction output decreases. In particular, in a metal magnetic thin film tape, since the magnetic layer is very thin, abrasion of the magnetic layer becomes a serious problem. A problem due to an increase in the coefficient of friction also occurs when a magnetic head is contact-start-stop (CSS) with a magnetic disk like a hard disk device. This is because the magnetic head slides on the rotating magnetic disk when the magnetic head flies and lands. In this case, if the friction coefficient increases, a problem such as abrasion of the magnetic layer of the magnetic disk occurs, but a problem such as a head crash also occurs. To ensure product-level reliability, CS
It is desired that the coefficient of friction after performing S operation 20,000 times is 0.5 or less.

[0005] In order to solve the various problems caused by the increase in the coefficient of friction as described above and the problem of running durability, use of various kinds of lubricants has been studied. Attempts have been made to coat or internally add to a magnetic paint in the case of a coating type magnetic recording medium. The properties of the lubricant include not only having a good lubricating effect with the magnetic head, but also (1) being excellent in low-temperature properties so that a predetermined lubricating effect can be ensured even when used in cold regions. (2) The coating can be applied extremely thinly so that the spacing loss with the magnetic head can be minimized, and in that case, a sufficient lubrication effect can be exhibited. (3) Long-term use and long-term lubrication effect Is required to be maintained.

In order to realize the above-mentioned characteristics at a thickness of a monomolecular layer of about several nm, it is necessary to examine the molecular structure of the compound constituting the lubricant. Currently, a lubricant composed of a silicon-based, hydrocarbon-based, or fluorine-based compound is typically used as a lubricant for a magnetic recording medium.

[0007]

However, none of the lubricants has sufficient lubricating properties for practical use, and there is a problem such as a reduction in reproduction output level in a shuttle running test. . Therefore, the present invention has been proposed in view of such circumstances, and by using a lubricant that can ensure an excellent lubricating effect under various use conditions and maintain this lubricating property for a long time. It is an object of the present invention to provide a magnetic recording medium excellent in running property, wear resistance, durability and the like.

[0008]

The magnetic recording medium according to the present invention has been proposed to achieve the above-mentioned object, and at least a magnetic layer and a carbon protective layer are provided on a non-magnetic support in this order. In the formed magnetic recording medium,
A lubricant mainly composed of an acid anhydride having two hydrocarbon groups is held on the surface of the carbon protective layer.

The acid anhydride having two hydrocarbon groups is represented by the following general formula (1). R ¹ —CO—O—CO—R ² (1) (However, R ¹ and R ^{2 each} represent a hydrocarbon group.) In the general formula (1), R ¹ and R ² are directly A chain hydrocarbon group is preferred. The number of carbon atoms in each of R ¹ and R ² is preferably 3 to 29, and the total number of carbon atoms in R ¹ and R ² is preferably 12 to 42. That is, R ¹ and R ² are represented by the following general formulas (2) and
It is shown in (3).

CH ₃ (CH ₂ ) _m (2) CH ₃ (CH ₂ ) _n (3) (where m, n = 2 to 28, and m + n = 10 to 40) R ^{If the} carbon number in ¹ and R ² is too small, the durability of the magnetic recording medium against friction and abrasion deteriorates. Conversely, if the carbon number is too large, the solubility in a solvent deteriorates.
It becomes difficult to use as a lubricant. Also, R ¹ ,
If the total number of carbon atoms in R ² is too small, the cohesive force between the hydrocarbons decreases, so that the lubricant film cannot withstand the shear stress in the direction parallel to the film surface caused by friction and breaks. For this reason, the friction coefficient of the magnetic recording medium increases, and the durability decreases. Conversely, if the total number of carbon atoms in R ¹ and R ² is too large, the solubility in a solvent will deteriorate, making it difficult to use as a lubricant.

[0011]

The acid anhydride having two hydrocarbon groups, which are the main components of the lubricant, has a polar group in the molecule adsorbed on the carbon protective layer and forms a lubricating film by the cohesive force of the hydrophobic group. In addition, since acid anhydrides have relatively low acidity, pH =
The carbon protective layer having a very strong acidic surface such as about 2 exhibits a better adsorption power than a compound having a highly acidic polar group such as carboxylic acid.

Therefore, such a lubricant containing an acid anhydride as a main component can maintain an excellent lubricating effect on the carbon protective layer for a long time. Therefore, the magnetic recording medium coated with the above-described lubricant maintains the reduced friction coefficient over a long period of time, and exhibits excellent running durability, wear resistance, and durability.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described, but it goes without saying that the present invention is not limited to these embodiments. Example 1 In this example, a magnetic tape holding a lubricant mainly composed of myristic anhydride was prepared.

Specifically, first, the aforementioned general formula (1)
In the above, an acid anhydride (stearic anhydride) in which the number of carbon atoms of the linear hydrocarbon group represented by R ¹ and R ² is 13 and the total number of carbon atoms of these hydrocarbon groups is 26 is converted to toluene. The lubricant of Example 1 was prepared by dissolving. On the other hand, a magnetic layer having a thickness of 100 nm was formed by applying a Co-Ni alloy to a 10 μm-thick polyethylene terephthalate film by oblique evaporation, and a 15 nm-thick film was formed on the surface of the magnetic layer by sputtering. After forming the carbon protective layer, this was cut into 8 mm width to produce a magnetic tape.

The lubricant of Example 1 was applied to the surface of the carbon protective layer of the magnetic tape at a coating amount of 5 mg / m ² . The sample tape of Example 1 was completed from the one thus obtained. Examples 2 to 24 In this example, the lubricants of Examples 2 to 26 in which the types of acid anhydrides were different were prepared.

Here, the acid anhydride which is the main component of the lubricant of Examples 2 to 26 is represented by the above-mentioned general formula (1), and is represented by R ¹ and R ^2. Tables 1 and 2 show the respective carbon numbers of the chain hydrocarbon groups and the total carbon numbers of the two hydrocarbon groups.

[0017]

[Table 1]

[0018]

[Table 2]

Each acid anhydride is dissolved in toluene. Then, the lubricant as described above was used in Example 1.
The sample tapes of Examples 2 to 26 were prepared by applying the composition to the surface of the carbon protective layer in the same manner as in Example 1. Comparative Examples 1 to 5 For comparison, the lubricants of Comparative Examples 1 to 5 mainly containing a long-chain carboxylic acid instead of the acid anhydride were prepared.

Here, the structures of the long-chain carboxylic acids which are the main components of the lubricants of Comparative Examples 1 to 5 are shown in Table 3.

[0021]

[Table 3]

Each long-chain carboxylic acid was dissolved in toluene. Then, by applying the above-mentioned lubricant to the surface of the carbon protective layer in the same manner as in Example 1, sample tapes of Comparative Examples 1 to 5 were produced. Evaluation of characteristics Examples 1-26 and Comparative Example 1 produced as described above
For each of the sample tapes Nos. To 5, the friction coefficient, still durability, and shuttle durability under the atmosphere conditions of condition α, condition β, and condition γ were measured. The still durability was evaluated by the time required for the output in the paused state to decrease by 3 dB, and the shuttle durability was evaluated by the number of shuttle operations performed until the output decreased by 3 dB by performing a 2-minute shuttle run each time. In addition, each atmosphere condition shown by (alpha), (beta), (gamma) is shown in Table 4, and the measurement result in each sample tape is shown in Tables 5-9.

[0023]

[Table 4]

[0024]

[Table 5]

[0025]

[Table 6]

[0026]

[Table 7]

[0027]

[Table 8]

[0028]

[Table 9]

From Tables 5 to 9, the sample tapes of Comparative Examples 1 to 5 have a large coefficient of friction and significantly deteriorated still durability and shuttle durability. Shows that the friction coefficient is small under any of the atmospheric conditions, and it is excellent in still durability and shuttle durability. However, the sample tapes of Example 25 and Example 26 used a lubricant mainly composed of an acid anhydride having two hydrocarbon groups, but the total number of carbon atoms of the two hydrocarbon groups was small. Therefore, the coefficient of friction is large, and the still durability and shuttle durability are significantly degraded.

From this, it is found that the use of an acid anhydride having an appropriate number of carbon atoms in the hydrocarbon group results in a lubricant excellent in lubricating effect, and the magnetic tape holding such a lubricant is
It was found that the running durability was excellent. As described above, the magnetic recording medium according to the present invention has been described, but the present invention is not limited to the above-described embodiment, and various modifications can be made.

As the acid anhydride, the above-mentioned general formula (1)
Has a carbon number of 3 to 29 in the linear hydrocarbon group represented by R ¹ and R ² , and the total of these carbon numbers is 12 to 42.
Should be fine. The most preferred R ¹ and R ² have 7 to 23 carbon atoms, and the most preferred total carbon number of both is 14 to 38. Specifically, caprylic anhydride, pelargonic anhydride, undecylic anhydride, lauric anhydride, tridecylic anhydride, myristic anhydride, pentadecylic anhydride, palmitic anhydride, heptadecyl anhydride, stearic anhydride, nonadecyl anhydride, anhydride Arachiic acid and the like. Of course, not limited to the compound equal number of carbon atoms of the R ^1, R ^2, satisfies the relationship between the number of carbon atoms described above may be such that the number of carbon atoms of R ¹ and R ² are different.

The above-mentioned acid anhydride is dissolved in a general-purpose solvent such as toluene or hexane to become a lubricant. The amount of the lubricant to be applied to the carbon protective layer is such that the above-mentioned acid anhydride is added in an amount of 0.1 to 1 m ^{2 of the} magnetic layer.
The dose may be 5 mg to 100 mg, more preferably 1 to 20 mg. If the amount is too small, the effect of reducing the coefficient of friction and the effect of improving wear resistance and durability will not be exhibited. On the other hand, if the amount is too large, sticking will occur between the sliding member and the magnetic layer, and the runnability will be worse, and a head clog in which abrasion powder from the magnetic layer adheres to the magnetic head will occur. May be disabled.

When the above lubricant is held in the carbon protective layer, one of the above-mentioned acid anhydrides may be used alone, or two or more thereof may be used in combination. Further, it can be used in combination with a conventionally known lubricant, and can also be used in combination with an extreme pressure agent or a rust preventive. When the extreme pressure agent is used in combination, it is used in a weight ratio of about 30:70 to 70:30 in order to maintain a lubricating effect under more severe conditions. The extreme pressure agent reacts with the metal surface due to frictional heat generated when partial metal contact occurs in the boundary lubrication region, and performs an action of preventing friction and wear by forming a reaction product film. Any of a phosphorus-based extreme pressure agent, a sulfur-based extreme pressure agent, a halogen-based extreme pressure agent, an organometallic extreme pressure agent, a composite extreme pressure agent, and the like can be used.

As the rust preventive, any one can be used as long as it is generally used as a rust preventive for magnetic recording media. Examples thereof include phenols, naphthols, quinones, and heterocycles containing a nitrogen atom. Compounds, heterocyclic compounds containing an oxygen atom, heterocyclic compounds containing a sulfur atom, and the like can be used. In the case where the lubricant and the rust preventive are used together,
Although they may be mixed and used, for example, it is easier to apply a rust inhibitor to the surface of the carbon protective layer and then apply a lubricant to separate the two into two layers, whereby the respective effects are easily exerted.

By the way, as the material constituting the magnetic recording medium coated with the above-mentioned lubricant, any conventionally known materials can be used, and there is no particular limitation. Non-magnetic supports include polyesters, polyolefins,
Cellulose, vinyl resin, polyimide, polymer substrate formed of a polymer material represented by polycarbonates, aluminum alloy, metal substrate made of titanium alloy, ceramic substrate such as aluminum glass,
A glass substrate or the like can be used, and its shape is not limited at all. However, when the present invention is applied to a magnetic tape, it is preferable to use a polyethylene terephthalate film, a polyethylene naphthalate film, an aramid film, or the like.
When a rigid substrate such as an Al alloy plate or a glass plate is used, an oxide film such as alumite treatment or a Ni-P film may be formed on the substrate surface to make the surface hard. An underlayer may be provided on these non-magnetic supports before forming the metal magnetic thin film.

The metal magnetic thin film is formed as a continuous film by a technique such as plating, sputtering, or vacuum deposition, and is made of a metal such as Fe, Co, or Ni, a Co—Ni alloy, a Co—Pt alloy, or a Co—Pt alloy. -Pt-Ni alloy, Fe
-Co-based alloy, Fe-Ni-based alloy, Fe-Co-Ni-based alloy, Fe-Ni-B-based alloy, Fe-Co-B-based alloy,
An in-plane magnetization recording metal magnetic film made of an Fe-Co-Ni-B alloy or the like, or a Co-Cr alloy thin film may be used.

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, and Ti 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 improve coercivity.

As the carbon protective layer, a carbon film, a diamond-like or amorphous carbon film formed by sputtering is preferably used.
However, chromium oxide, SiO ₂ , ZrO
It is also possible to use ₂ or the like, and the film formation method is not limited to sputtering, and any conventionally known method can be used. Here, the thickness of the carbon protective layer is preferably 2 to 100 nm, particularly 5 to 30 nm.
It is preferably set to nm.

Further, the magnetic recording medium according to the present invention may have a back coat layer mainly composed of a binder and an abrasive, if necessary. In this case, the conditions for forming the back coat layer are not particularly limited as long as they are generally applied to a method for manufacturing a magnetic recording medium. The above-mentioned lubricant may be applied to the back coat layer or may be internally added.

[0040]

As is clear from the above description, the lubricant containing an acid anhydride having two hydrocarbon groups as a main component is:
It exhibits excellent lubricating effect under all conditions and can maintain its lubricating effect for a long time. Therefore, the magnetic recording medium in which the lubricant is held on the surface of the carbon protective layer exhibits excellent running durability, and also has excellent wear resistance and durability. In addition, since these characteristics are not impaired even under severe conditions such as low temperature, a highly reliable magnetic recording medium can be provided.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-342517 (JP, A) JP-A-4-186524 (JP, A) JP-A-62-28331 (JP, A) JP-A-58-1983 146026 (JP, A) JP-A-60-182013 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/725 C10M 105/24

Claims (3)

(57) [Claims] 1. A magnetic recording medium comprising at least a magnetic layer and a carbon protective layer formed in this order on a non-magnetic support, wherein an acid anhydride having two hydrocarbon groups is mainly formed on the surface of the carbon protective layer. A magnetic recording medium characterized by holding a lubricant. 2. The magnetic recording medium according to claim 1, wherein the hydrocarbon group has a linear structure. 3. The hydrocarbon group has 3 carbon atoms each.
The magnetic recording medium according to claim 1, wherein the total number of carbon atoms in the two hydrocarbon groups is 12 to 42.