JPH0754577B2 - Magnetic recording medium - Google Patents

Description

The present invention relates to a magnetic recording medium, and is particularly suitable for applications such as magnetic disks, magnetic drums, magnetic tapes, and magnetic cards.
The present invention relates to a magnetic recording medium having excellent durability.

[Background of the Invention]

Generally, a magnetic recording medium is one in which a magnetic layer, which is a magnetic recording film, is formed on various substrates made of an organic material or an inorganic material, and the surface of the magnetic layer of the medium is rubbed by a magnetic recording head during magnetic recording and reproduction. To be done. A major problem is that the performance of the magnetic layer is deteriorated due to the abrasion during the friction. For example, during steady operation in a magnetic disk device, the magnetic head is in a floating state due to the levitation force of an air film generated on the surface of the rotating disk. However, at the time of starting or stopping the rotation of the magnetic disk, the floating force is lost and the magnetic head and the disk come into contact sliding condition. In order to reduce the wear of the magnetic recording medium in such a contact sliding state and to prevent the flying characteristics of the magnetic head from being impaired, a lubricating layer firmly bonded to the magnetic recording film is required.

Japanese Patent Laid-Open No. 57-164430 discloses that a surface treatment layer is provided on the magnetic recording film to improve the adhesion to the lubricating layer. This is a combination of a fluorinated alkane such as tetrafluoroethylene telomer as a lubricant and a fluorine-based surface treatment agent, and the surface treatment agent and the magnetic layer are merely physical bonds, so the surface treatment There is a drawback in that the adhesion of the layer to the magnetic recording film is insufficient and the abrasion resistance is not sufficient, and thus the durability as a magnetic recording medium is poor.

[Object of the Invention]

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a magnetic recording medium having excellent wear resistance of the magnetic recording film and excellent durability.

[Outline of Invention]

In general, it is considered that a lubricant that easily adheres to an object to be rubbed and that is easily sheared in the friction direction effectively acts as a lubricant and imparts wear resistance. Conventionally, as such a lubricant, a substance such as higher fatty acid (and its derivative), silicone oil, and fluorine-based oil is used as a lubricant for the magnetic recording medium, but some improvement in wear resistance is recognized. However, it is still not completely satisfactory, and there is a demand for further improvement in durability.

The inventors of the present invention have conducted extensive studies in view of the above situation, and as a result, decomposed a specific fluorine-containing azide compound on the surface of the magnetic layer, which is a magnetic recording film, and generate it through nitrene,
By applying a surface treatment to bond a fluorine-containing azide compound to the surface of the magnetic layer and then providing a fluorine-containing lubricating substance layer on it, the lubricating substance can be firmly adhered to the surface of the magnetic layer. It was found that the wear resistance of the magnetic recording medium was significantly improved, and the magnetic recording medium had excellent durability that could not be achieved by the conventional technique, and the present invention was completed.

In the magnetic recording medium of the present invention, a surface treating agent having a molecular structure similar to that of the lubricating substance is covalently bonded to the surface of the magnetic layer through nitrene, and the lubricating substance has a molecular structure similar to that of the surface treating agent. Because they have a good intermolecular compatibility, they are bound by a strong intermolecular force. Therefore, the lubricating material layer is easily sheared by the contact of the object and is recombined with the surface treatment layer, so that a magnetic recording medium having excellent sliding resistance and durability can be obtained.

The magnetic recording medium of the present invention will be specifically described below.

In the magnetic recording medium of the present invention, the substance used as the surface treatment agent for the magnetic layer which is the magnetic recording film is selected from compounds having a perfluoroalkyl polyether chain and having at least one azide group. Be done. The perfluoroalkylpolyether chain is not limited to a linear chain, but may be a branched chain. Specific examples of compounds having the perfumeoloalkyl polyether chain and having at least one azide group include the specific compounds shown in Table 1.

Further, as a compound having the above-mentioned perfluoroalkylpolyether chain and at least one azide group, a functional group that absorbs ultraviolet light, such as an unsaturated bond or an aromatic ring, is introduced in the vicinity of the azido group. May be.

Having these perfluoroalkyl polyether chains,
As a method for applying a compound having at least one azido group to the magnetic recording medium of the present invention as a surface treatment agent, for example, a method of spraying directly on a magnetic disk or magnetic tape or as a solution and further wiping is applied. To be done. Then, the azido group of the surface treatment agent is decomposed by irradiation with ultraviolet light or heating to generate nitrene, and the covalent bond is firmly formed with the surface of the magnetic layer.

Lubricant material provided on the surface treatment layer of the present invention is a compound having a perfluoroalkyl polyether chain, for example the general formula, F [CF (CF ₃₎ CF ₂ O] _n CF (CF ₃₎ X (formula In the formula, X represents a substituent selected from the group consisting of F atom, CO ₂ H group, CO ₂ Li group, and CH ₂ OH group.), Or CF ₃ O (CF ₂ CF ₂ O) _m (CF ₂ O) _n CF _{3 and the} like, and specific compound examples thereof are shown in Table 2.

If the film thickness of the surface treatment layer in the present invention is less than 5Å, the coating state is not good and the effect of coupling with the magnetic layer is not sufficient.
If it exceeds 500Å, the spacing between the magnetic head and the medium becomes large and the reproduction output loss increases. Therefore, the film thickness is preferably in the range of 5 to 500Å, more preferably in the range of 20 to 250Å.

When the film thickness of the lubricating substance layer formed on the surface-treated layer of the present invention is less than 20Å, the coverage as a lubricant is deteriorated, and a sufficient lubrication effect cannot be obtained. Since the reproduction output loss increases, the film thickness is preferably in the range of 20 to 500Å, and 30 to 2
A range of 50Å is more preferable.

In addition, the total thickness of the surface treatment layer and the lubricating material layer in the present invention is preferably 30 Å or more from the viewpoint of uniformity and strength, and the upper limit thereof is reproduction by spacing between the magnetic head and the medium. From the viewpoint of output loss, it is desirable to be less than 500Å.

As a magnetic recording medium to which the present invention is applied, a magnetic layer, which is a magnetic recording film, includes a metal magnetic film such as a Co-Cr alloy, a Co-Ni alloy, a Co-Fe alloy, and a Co-P alloy, and a magnetic layer. γ-Fe ₂ O _3, Co-containing _{γ-Fe 2 O 3, Fe} 3 O 4, Co -containing Fe ₃ O _4, CrO ₂ oxide magnetic powder and Fe such as, Co, and Ni, metal-magnetic alloys thereof The thing containing a powder etc. can be mentioned. Needless to say, the present invention is also applicable to a magnetic recording medium having a protective film on the magnetic recording film.

Example of Invention

Before describing the examples of the present invention, a method for synthesizing an azide compound having a perfluoroalkyl polyether chain, which is a novel substance used as the surface treatment agent of the present invention, will be described below.

(Synthesis Example 1) 1,1,2-trichlorotrifluoroethane (Freon) solution of polyhexafluoropropylene oxide acid (Krytox 157FS, trade name of DuPont) is dried and then treated with thionyl chloride to obtain the following chemical formula (1). The acid chloride shown by was obtained.

F [CF (CF ₃₎ CF ₂ O] _{n CF (CF 3) COCl ......} (1) Then, the compound (1) as a freon solution, after stirring at room temperature was added a diethyl ether solution of p- azido aniline, When the solvent was distilled off, an azide represented by the following chemical formula (2) was obtained.

By using 2-azido ethanol instead of the above p-azidoaniline, an azide represented by the following chemical formula (3) was obtained.

F [CF (CF ₃₎ CF ₂ O] _{n CF (CF 3) CO 2} (CH 2) 2 N 3 ......
(3) (Synthesis Example 2) Krytox 157FS and silver oxide were dissolved in dry freon, the above mixture was stirred at room temperature, unreacted silver oxide was filtered off, and the solvent was distilled off to obtain a silver salt. When this silver salt was heated in the presence of iodine and decarboxylated, an iodide represented by the following chemical formula (4) was obtained.

F [CF (CF ₃ ) CF ₂ O] _n CF (CF ₃ ) I (4) The compound (4) and 10-undecen-1-ol are added to 2,
It was heated with 2'-azoisobutyronitrile (AIBN) in a nitrogen atmosphere to obtain the following compound.

F [CF (CF ₃₎ CF ₂ O] _{n CF (CF 3) CHCH (} I) (CH 2) 9 O
H This compound was sequentially treated with lithium aluminum hydride, hydrobromic acid, and sodium azide to obtain an azide represented by the following chemical formula (5).

F [CF (CF ₃₎ CF ₂ O] _{n CF (CF 3) (CH} 2) 11 N 3 ......
(5) Instead of the above Krytox 157FS, a perfluoroalkyl polyether HO ₂ CCF ₂ O (CF
₂ O) _m (CF ₂ CF ₂ O) _n CF ₂ CO ₂ H was synthesized by the above method to obtain an azide compound represented by the following chemical formulas (6), (7) and (8). It was

N ₃ (CH ₂ ) ₂ CO ₂ CF ₂ O (CF ₂ O) _m (CF ₂ CF ₂ O) _n CF ₂ CO ₂ (C
H ₂ ) ₂ N ₃ (7) N ₃ (CH ₂ ) ₁₁ CF ₂ O (CF ₂ O) _m (CF ₂ CF ₂ O) _n CF ₂ (CH ₂ ) ₁₁ N
₃ (8) The structures of chemical formulas (1) to (8) were confirmed by infrared (IR) and nuclear magnetic resonance (NMR) spectra.

An example of the present invention will be described below in more detail.

The azide compound having the perfluoroalkylpolyether chain of the present invention shown in Table 1 above was used as the surface treatment agent in this example, and the lubricant substance of the present invention shown in Table 2 above was used as the lubricant. A compound having a perfluoroalkylpolyether chain was used, and as a comparative example, a conventional lubricating substance shown in Table 3 was used.

In Sample Nos. 1 to 14 of this example, a magnetic recording medium was prepared by dispersing magnetic powder (γ-Fe ₂ O ₃ ) in a binder made of epoxy, phenol, and polyvinyl butyral resin and having a diameter of 5 inches. Type magnetic disk was used to apply the surface treatment agent shown in Table 1 to a predetermined film thickness, and the coating was heated in a nitrogen atmosphere at a temperature of about 150 ° C. for about 30 minutes. A method of forming a surface treatment layer which is chemically bonded directly to the magnetic recording medium by ultrasonically cleaning the magnetic disk in a Freon solution for 10 minutes before applying the lubricating substance to remove the unreacted surface treatment agent Will be referred to as treatment method (2), and on the other hand, the treatment method in which the lubricating substance is applied without Freon cleaning will be referred to as treatment method (1). The lubricant substance was applied by spraying in the form of a Freon solution, and then the excess lubricant substance was wiped off with a gauze tape while rotating the magnetic disk until the thickness of the lubricant substance layer became a predetermined thickness.

The film thickness of the surface treatment layer and the lubricating substance layer were measured by a Fourier transform infrared spectroscope.

The sliding strength against the magnetic head was measured by using the magnetic disk manufactured by the above method with α-Al ₂ O ₃ with a load of 20 g applied.
Durability was evaluated by using a slider (a spherical slider with a radius of curvature of 30 mm) repeatedly sliding at a sliding speed of 10 m / s, and measuring the number of times until a flaw was generated on the surface of the magnetic recording medium. .

The results of exposure (UV) with a 600 watt Hg-Xe lamp instead of the heat treatment are shown in Sample Nos. 8 to 14 of this example.

For sample Nos. 1 to 9 which are comparative examples, application and treatment of the surface treatment agent were not performed, and sample No. 1 of the above-described example was used.
Sample No. 1 of the comparative example according to the method shown in
For 0 to 12, after surface treatment, a non-fluorine-based lubricant was used to prepare a sample having a predetermined thickness of the lubricating substance layer,
The sliding strength was measured by the above sliding test method.

Sample Nos. 15 to 17 of this example were used as a magnetic recording medium, and were 0.3 μm by a high frequency sputtering method in Ar gas.
Using a magnetic disk in which a Co-Cr metal magnetic film having a thickness of m is formed on a glass substrate, the surface treatment agent is applied, and its treatment and lubrication are performed in the same manner as in Sample Nos. 1 to 14 of the present embodiment. A sample was prepared by applying a volatile substance. The sliding strength was measured by the above sliding test method.

For sample Nos. 13 to 14 which are comparative examples, on the surface of the Co-Cr metal magnetic film produced by the same method as that of sample Nos. 15 to 17 in the above-mentioned examples, A lubricant was applied in the same manner as in 12 to prepare a sample. The sliding strength was measured by the same method as above.

The test results in this example are shown in Tables 4, 5 and 6.
Shown in the table.

As can be seen from Table 4, in the example samples Nos. 1 to 4 in which the lubricating substance layer and the surface treatment layer having almost the same film thickness as the lubricating substance layer of the comparative sample No. 1 were provided, It is recognized that the surface treatment layer improves the sliding strength by about one digit.

In addition, when the sample Nos. 1 to 4 of the example and the samples No. 5 to 7 of the example are compared, it is shown that the treatment method (2) of the surface treatment agent has the same effect as the treatment method (1).

Example samples Nos. 8 to 14 shown in Table 5 and the fourth sample
Comparing the example samples Nos. 5 to 7 in the table, it is clear that the same effect as the heat treatment can be obtained by the UV treatment.

Further, in the case where the fluorine-based surface treatment layer of the present invention was provided with a non-fluorine-based lubricating material layer, Comparative Example Sample Nos. 7 to 9 in Table 5 were obtained.
As seen in Sample Nos. 10 to 12 and the same, no significant improvement in sliding strength was observed even when the surface-treated layer of the present invention was used.
It has been shown for the first time that the sliding strength is significantly improved by combining the surface-treated layer of the present invention and the fluorine-based lubricating substance.

Furthermore, as shown in Example sample Nos. 15 to 17 in Table 6,
It is obvious that the present invention can obtain the same effect as the coating type magnetic film with respect to the metal magnetic film.

As described above in the examples of the present invention, it is understood that the magnetic disk according to the present invention exhibits good head sliding resistance in any case and has excellent durability as a magnetic recording medium.

〔The invention's effect〕

As described in detail above, in the magnetic recording medium of the present invention, the surface treating agent having a molecular structure similar to that of the lubricating substance is strongly covalently bonded to the surface of the magnetic layer which is the magnetic recording film via nitrene. In addition, since the intermolecular compatibility between the lubricating substance and the surface treatment agent is good and they are bound by a strong intermolecular force, a magnetic recording medium having good wear resistance on the surface of the magnetic layer and excellent durability is obtained. can get. The effect of the present invention is effective not only for the coating type magnetic recording medium and the Co-Cr sputtered metal magnetic recording medium but also for the metal magnetic film formed by plating or vapor deposition, which can be widely put into practical use and is industrially applicable. The utility value of is extremely large.

Claims (5)

[Claims] 1. A magnetic recording film formed directly or via a protective layer on a substrate, having a perfluoroalkylpolyether chain on the magnetic recording film and having at least one azide group. Magnetic recording in which a surface-treated layer made of a reaction product of a fluorine-containing azide compound having two is formed, and a lubricating substance layer made of a fluorine-containing compound having a basic skeleton of perfluoroalkyl polyether is formed on the surface-treated layer. In the medium, the surface treatment layer has a thickness of 5 to 50.
It is in the range of 0Å, and the film thickness of the above-mentioned lubricating substance layer is 20 to 500.
A magnetic recording medium having a range of Å. 2. The magnetic recording medium according to claim 1, wherein the reaction product of the fluorine-containing azide compound which is the surface treatment layer is formed by heating or exposure treatment. 3. A magnetic recording medium having a magnetic recording film formed on a substrate directly or via a protective layer, wherein a perfluoroalkylpolyether chain is formed on the magnetic recording medium film via a protective layer. A surface-treated layer comprising a reaction product of a fluorine-containing azide compound having at least one azido group, and a fluorine-containing compound having a perfluoroalkyl polyether as a basic skeleton is formed on the surface-treated layer. In the magnetic recording medium provided with the lubricating substance layer, the thickness of the surface treatment layer is in the range of 5 to 500Å, and the thickness of the lubricating substance layer is in the range of 20 to 500Å. Magnetic recording medium. 4. The magnetic recording medium according to claim 3, wherein the protective layer directly below the surface treatment layer is a film containing carbon as a main component. 5. The magnetic recording medium according to claim 3, wherein the reaction product of the fluorine-containing azide compound, which is the surface treatment layer, is formed by heat treatment or exposure treatment.