JPH02177018A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain high corrosion resistance and to improve a traveling property by forming a rust inhibitor layer on a magnetic recording layer consisting of a thin ferromagnetic metallic film which consists essentially of cobalt, and providing a layer contg. an aliphat. compd. on this rust inhibitor layer. CONSTITUTION:The magnetic recording layer of the magnetic recording medium is formed of the thin ferromagnetic metallic film which consists essentially of the cobalt. The rust inhibitor layer is formed on this magnetic recording layer and the layer contg. the aliphat. compd. is formed on this rust inhibitor layer. Fatty acids contg. >=12C in one molecule are used for the aliphat. compd. The layer which consists essentially of >=1 kinds of the compds. selected from the group consisting of benzotriazole, benzotriazole derivatives, benzimidazole, benzimidazole derivatives, naphthols, quinolines and quinones is used for the rust inhibitor layer. The high corrosion resistance is obtd. in such a manner and the traveling property is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ferromagnetic metal thin film type magnetic recording medium having a protective film made of a rust preventive agent. More specifically, the present invention relates to a ferromagnetic metal thin film magnetic recording medium having a protective film with excellent corrosion resistance.

[Prior Art] Magnetic recording media that have been commonly used in the past include coatings in which a magnetic coating mainly consisting of magnetic powder from a needle wipe and a polymeric bonded coating is applied onto a non-magnetic substrate to form a magnetic layer. This is a type of magnetic recording medium.

Currently, there is a trend toward higher density magnetic recording and reproducing devices, and there is a demand for magnetic recording media with excellent short wavelength recording characteristics.

However, there are limits to the improvement of short wavelength recording characteristics in coated magnetic recording media. On the other hand, C01CoNi,
C such as CoN1P and CoCr.

Vacuum deposition, sputtering, and
Metal thin film magnetic recording media formed on non-magnetic substrates by so-called physical vapor deposition methods such as ion brating have significantly high residual magnetic flux density because no non-magnetic binder is mixed in the magnetic layer. Moreover, since the magnetic layer can be formed extremely thin, it has the advantage of high output and excellent short wavelength response.

Due to this feature, thin film magnetic recording media have recently become the mainstream of magnetic media.

[Problems to be Solved by the Invention] Thin-film magnetic recording media have a high magnetic recording density and excellent short-wavelength recording properties, but sCo is relatively easy to corrode, and the magnetic layer is exposed. Poor corrosion resistance,
It has the disadvantage of being susceptible to magnetic deterioration, which makes it difficult to put into practical use.
1-This is a big problem.

To solve this problem, for example, a thiazole compound (Japanese Patent Publication No. 58-188) was added as a rust preventive to the magnetic recording layer.
(see Publication No. 333), cuperones (Special Publication No. 1984-194)
138), diamines, polyamines (see Japanese Patent Publication No. 59-3724), etc. have been proposed. All of these are intended to suppress surface corrosion under high humidity, which is the main cause of atmospheric corrosion.

That is, the attempt is made to react these with cobalt ions or cobalt oxides to form an insoluble salt on the surface of the thin film medium.

However, since the reactivity of these materials is not high, the formation of insoluble salts does not occur to the extent that the antirust effect is sufficiently exhibited.

In addition to these problems, media provided with a rust preventive layer also have the drawback of poor running stability.

From this perspective, 1. For the purpose of improving running stability,
A method of improving corrosion resistance and properties using a salt of a nitrogen-containing heterocyclic compound and a fatty acid has been disclosed (Japanese Patent Application Laid-Open No. 1982-1982).
-202326 publication).

Although this method claims that both characteristics can be achieved by using salt, it has the following drawbacks. In other words, in this case as well, it is mainly the nitrogen-containing heterocyclic compound that provides corrosion resistance, but in the above method, the fatty acid group side of the salt applied to the magnetic film surface also bonds with the magnetic film, so nitrogen The contained heterocyclic compound group side appears on the outermost surface, and this remains as a factor that inhibits running stability.

Therefore, the purpose of the present invention is to solve the problems of conventional products, which are easy to corrode in the atmosphere and difficult to obtain running stability, and to provide a metal thin film type with excellent corrosion resistance and running stability. An object of the present invention is to provide a magnetic recording medium.

[Means for solving the problem] The above object is to provide a ferromagnetic metal thin film containing Go as a main component,
This is achieved by providing a highly reactive rust preventive layer that facilitates the formation of insoluble salts, and then providing a layer containing an aliphatic compound.

The aliphatic compound is preferably a fatty acid containing 12 or more carbon atoms in one molecule.

Rust inhibitors used with aliphatic compounds are benzotriazole, benzotriazole derivatives, benzimidazole, benzimidazole derivatives.

Preferably, the main component is one or more compounds selected from the group consisting of naphthols, quinolines, and quinones.

[Operation] The nitrogen-containing heterocyclic compound applied to the rust preventive layer forms an insoluble salt between the nitrogen-containing heterocyclic compound and cobalt on the surface of the magnetic film. Compared to these known examples of rust preventives,
Its corrosion resistance is extremely high.

The role of the layer containing an aliphatic compound applied on this rust preventive layer is as follows. The aliphatic compound has good affinity with the nitrogen-containing heterocyclic compound and firmly adheres to the rust preventive layer. Therefore, it is possible to maintain a low coefficient of friction due to the aliphatic compound over a long period of time, and to exhibit good corrosion resistance.

Fatty acids are suitable as the aliphatic compounds used in the present invention. The fatty acids used in the present invention may be -basic acids, dibasic acids, or tribasic acids, as long as the number of carbon atoms in one molecule is 12 or more. Further, it may be either linear or branched. The molecule may have a substituent or functional group other than a carboxyl group.

If the number of carbon atoms is 12, the effect of reducing the friction coefficient, which contributes to running stability, will be low, and the strength of the acid will become stronger, resulting in the generation of more carbon ions than necessary. Therefore, it cannot be used in the present invention. The upper limit of the number of carbon atoms is not particularly limited, but from the viewpoint of handling, it is preferably up to about 18 carbon atoms.

The concentration of the coating liquid at this time is preferably within the range of about 0.005 wt% to about 0.5 wt% of the fatty acid. If the amount of fatty acid added is less than 0.005 wt%, the lubricating effect will be insufficient, and running stability will not be improved.

On the other hand, if the amount of fatty acid added exceeds 0.5 wt It will not be seen.

The rust preventive agent used in the rust preventive layer is, for example, benzotriazole, benzotriazole derivatives, benzimidazole, or pensimidazole derivatives.

These include naphthols, quinolines, and quinones, but other known rust inhibitors can also be used.
Moreover, it is also possible to use two or more kinds of rust preventives together, and furthermore, two or more kinds of fatty acids can also be used together. Generally, there are no particular restrictions or limitations on these combinations.

The method of forming the rust preventive layer itself is not an essential requirement of the present invention.

For example, a fatty acid or a rust preventive agent may be dissolved in a suitable solvent and applied by a conventional method such as the DINBU method, a gravure roll method, or a spin code method, or it may be directly formed on a magnetic recording layer by J1 blank evaporation, etc. It can be formed by various methods.

Although the thickness of the rust preventive layer itself is not an essential requirement of the present invention, it is generally preferable to fall within the range of 50 to 500 layers. If there are fewer than 50 people, it will be difficult to form a rust preventive layer with a uniform thickness, and if there are more than 500 people, the spacing loss will become excessive, which is not preferable.

The magnetic recording layer in the magnetic recording medium of the present invention is COS14
body or Co-N1y Co-Cr, Co-P*Co-
It is made of a Co alloy such as Nt--P and is deposited and formed on the substrate by means such as vacuum evaporation, sputtering, and ion blasting.

Magnetic recording media include magnetic tapes based on synthetic resin films such as polyester, polyimide, and polyethylene, magnetic disks and magnetic drums based on disks and drums made of synthetic resins, aluminum, glass, etc. , including various forms of structures that come into sliding contact with the magnetic nod when stopped.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Fruit 11 [0.0 of 5-nitrobenzotriazole as a rust inhibitor
A 5wt% isopropyl alcohol solution was used, and a 0.05wt% benzene solution of stearic acid was used as the fatty acid. Polyethylene terephthalate (PET) on the substrate
CoNi (Co-80at%
*A magnetic recording layer was formed by providing an obliquely deposited Ni-20at% film (thickness: 1500 nm).

First, the above-mentioned rust preventive-containing IPA solution was applied onto this vapor-deposited film. The coating amount in this case is 3 to 50 m1/m2, preferably 3 to 20 mλ/(H2).Then, after drying the coated layer of this rust preventive-containing IPA solution, the above benzene solution was coated. The coating amount was the same as above.

A magnetic recording medium was produced under the same conditions as in Example 1 except that 1-nitrone-2-naphthol was used as a rust preventive agent instead of 6-nitrobenzotriazole.

EXAMPLE 1 A magnetic recording medium was produced under the same conditions as in Example 1 except that nitrosohydroxyquinoline was used as the rust preventive agent instead of 6-nitrobenzotriazole.

The first in heaven.

A magnetic recording medium was produced under the same conditions as in Example 1 except that lauric acid was used as the fatty acid instead of stearic acid.

Comparison 1 A magnetic recording medium was produced under the same conditions as in Example 1 except that only stearic acid was used without using a rust preventive.

L Etsusho 1 A magnetic recording medium was produced using Cuperone Q and lvt% as a rust preventive agent, and without adding fatty acids, and under the same conditions as described in Example 1 except for the addition of fatty acids.

Tokasho 1 A magnetic recording medium was produced under the same conditions as in Example 1 except that stearic acid was not added.

Hika Takumi 1 Commercially available salt of benzotriazole and stearic acid.
A magnetic recording medium was produced under the same conditions as in Example 1, except that the 1wtX IPA solution was applied once instead of twice as in Example 1.

A sample was cut from the magnetic recording medium obtained as described above and left in an atmosphere of 60° C. and 90% RH for one week, and then the rate of decrease in saturation magnetization (Ms) was measured, and changes in the medium surface over time were measured. was visually observed. Furthermore, running stability was evaluated using jitter values. Jitter rating is 8mmV
Play back the video signal recorded by TR, and one of the playback signals
The interval between horizontal synchronization signals of 5.75 kHz was read, and the deviation of this horizontal synchronization signal was defined as jitter. The results are shown in Table 1 below.
The following is a summary.

As is clear from the results shown in Table 1, according to the present invention, extremely high corrosion resistance and excellent running stability can be obtained by providing a two-layer structure consisting of a rust preventive layer and an aliphatic compound layer.

[Effects of the Invention] As explained above, in the present invention, the rust preventive layer has a two-layer structure, and the second layer uses an aliphatic compound.

Regarding corrosion resistance, by simultaneously adding an acid that promotes the ionization of cobalt, an insoluble salt of a nitrogen-containing heterocyclic compound is formed in one minute, and at the same time, the fatty acid itself also forms an insoluble salt that supplements corrosion resistance. At the same time, it also plays a role in increasing driving stability.

As a result, it not only provides extremely high corrosion resistance that cannot be obtained with conventional rust inhibitors, but also improves the ability to leave the company.

Claims (3)

[Claims] (1) A rust preventive layer is formed on a magnetic recording layer made of a ferromagnetic metal thin film containing cobalt as a main component, and a layer containing an aliphatic compound is provided on this rust preventive layer. magnetic recording media. (2) The magnetic recording medium according to claim 1, wherein the aliphatic compound is a fatty acid containing 12 or more carbon atoms in one molecule. (3) The rust preventive layer is mainly composed of one or more compounds selected from the group consisting of benzotriazole, benzotriazole derivatives, benzimidazole, benzimidazole derivatives, naphthols, quinolines, and quinones. The magnetic recording medium according to claim 1.