JPH0654534B2 - Magnetic recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium, and more particularly to a metal thin film type magnetic recording medium which does not cause rust and has excellent storage stability.

[Conventional technology]

As a magnetic recording medium, a coating type one obtained by coating a non-magnetic substrate with a magnetic coating material in which a ferromagnetic powder is dispersed in an organic binder and drying it has been widely used. However, since this coating type magnetic recording medium mainly uses a metal oxide powder as the ferromagnetic powder, it has a small saturation magnetization, and since it contains an organic binder, the concentration of the ferromagnetic material in the magnetic layer cannot be increased. However, it is not suitable for high-density recording and has a drawback that the manufacturing process is complicated.

In recent years, the demand for high-density recording has increased, and in response to this, a magnetic recording medium in which a metal thin film is formed on a non-magnetic substrate has been developed. This is a vapor deposition method such as vacuum deposition, sputtering, ion plating, or A metal thin film is formed on a non-magnetic substrate by a plating method such as electric plating or electroless plating.The magnetic material is not limited to metal, but since metal is typical, The magnetic recording medium having the above is referred to as a metal thin film type magnetic recording medium. Further, since this type does not contain an organic binder, it is also called a non-binder type magnetic recording medium.

In this metal thin film magnetic recording medium, a ferromagnetic metal having a large saturation magnetization can be formed as a thin film without containing a binder. It is attracting attention because it has little effect of demagnetization in the wavelength range, realizes high-density recording, and simplifies the manufacturing process.

However, although the metal thin film of the metal thin film magnetic recording medium has a smooth and smooth metal surface in appearance, it has a rough fine structure and a structure in which fine metal particles are lined up. In addition, this type of magnetic recording medium is inferior in weather resistance and corrosion resistance as compared with the coating type magnetic recording medium. In particular, magnetic recording media used as cassette tapes, video tapes, etc., rub against the surface of the media during recording and reproduction, so even if there is a very slight amount of corroded material on the metal thin film, it will fall off due to friction. As a result, the head is clogged, which damages the head and the magnetic recording medium.

Further, the metal thin film type magnetic recording medium has a problem of poor durability. This type of magnetic recording medium has a problem that since the metal thin film is smooth, it causes large friction and is likely to cause fracturing, and it is inferior to the coating type in the still durability of the VTR.

In order to improve the weather resistance and durability of such a metal thin film type magnetic recording medium, a method of performing surface nitriding treatment by ion plating (Japanese Patent Laid-Open No. 33806/1975) and a method of forming a silicon nitride film by sputtering ( JP-A-5
3-30304), a method of forming a non-magnetic surface layer by exposing a magnetic film to an electric discharge in an atmosphere such as nitrogen gas (JP-A-53-85403), and a metal thin film nitrided on a magnetic metal thin film. A method of providing (JP-A-54-143111),
Etc. are known. Further, as a non-binder type magnetic recording medium having excellent weather resistance, there is a magnetic thin film made of iron nitride or iron and iron nitride as disclosed in European Patent No. 8328 or JP-A-59-87809. Further, the applicant of the present invention previously disclosed a magnetic recording medium comprising a magnetic thin film containing iron oxynitride as a main component on a non-magnetic substrate (Japanese Patent Laid-Open No. Sho 6-62).
1-54023), the magnetic thin film has a composition represented by the following composition formula: Fe _1-XY N _X O _Y (where 0.25 ≦ X + Y ≦ 0.60). Atsuta

[Problems to be Solved by the Present Invention]

However, according to the above-mentioned method, although the rust resistance is greatly improved, there is a problem in storage stability. That is, the adhesion between the substrate and the thin film after storage and storage is insufficient, and improvement has been desired.

Therefore, an object of the present invention is to provide a magnetic recording medium having excellent storability.

[Means for solving problems]

That is, the present invention provides a magnetic recording medium provided with a ferromagnetic metal thin film mainly composed of iron formed on a non-magnetic substrate as a magnetic layer, wherein the metal thin film contains at least nitrogen atoms and oxygen atoms. And the atomic number ratio of oxygen to iron contained in the ferromagnetic film gradually increases from the vicinity of the surface of the thin film toward the substrate, that is, in the depth direction of the ferromagnetic thin film, gradually increases toward the substrate. And a magnetic recording medium characterized by the fact that

The ferromagnetic thin film containing iron, nitrogen, and oxygen atoms referred to in the present invention is a complex mixture or composite containing pure iron, iron nitride, and iron oxide as main components. For example, with respect to iron nitride, ε-Fe _2-3 N, γ-Fe ₄ N, Fe
_It can have a crystal structure such as ₁₆ N ₂ , and its composition and ratio can be controlled to some extent by controlling the film forming conditions. In the present invention, in the depth direction of the ferromagnetic thin film, the ratio of oxygen atoms contained in the thin film to iron atoms is gradually increased toward the non-magnetic substrate.
However, in the very surface of the thin film, the oxygen content is increased due to the presence of the natural oxide layer, and thus this region is excluded. The atomic ratio of oxygen to iron can be analyzed by Auger electron spectroscopy (AES). When obtaining information in the depth direction, for example, the magnetic thin film is etched while being etched with argon ions. The method is widely known.

The method for forming the ferromagnetic metal thin film of the present invention on a non-magnetic substrate will be described below. The film forming method is the well-known oblique deposition method. Then, in order to cause a nitriding or oxidation reaction at the time of film formation, a combination with an ion plating method or a combination with ion beam irradiation (so-called ion beam assisted vapor deposition or the like) is performed. FIG. 1 shows an example of the nonmagnetic substrate 2. Fixed, and iron material on this 4. Electron beam 5. At the same time when the film is deposited by dissolving and evaporating by means of the ion gun 6. To form an iron oxynitride film. Ion gun has nitrogen and oxygen atoms 7. (For example, N ₂ gas, NH ₃ gas, NO _X gas, O
₂ gas, etc.) is introduced, and its ions, radicals,
1. Bases made by creating atoms in an ion gun. Irradiate on top. Alternatively, gas inlet 8. It is also possible to change the reaction atmosphere by introducing more atmosphere gas.

In the apparatus shown in FIG. 1, an iron material is used to obtain the thin film magnetic layer of the present invention. Ion gun during film formation while keeping the evaporation rate of 6 constant. Gas introduced into 7. The composition of can be changed with time. For example, N ₂ 50%, O ₂ 5
It can be prepared by a method of gradually reducing the amount of O ₂ gas mixed with 0% gas. Alternatively, the iron material 4. Keep the evaporation rate constant and keep the ion gun 6. Gas in the state where it is also operated constantly 7. Under the condition that N ₂ gas is used, the gas inlet 8. The amount of O ₂ gas introduced from is increased with time. In FIG. 2, an ion gun 24. Is incorporated to enable the production of iron oxynitride film. According to this device,
Substrate 22. Cooling drum 23. A magnetic film is formed by being irradiated with the iron vapor flow and the nitrogen ion or nitrogen + oxygen ion flow while being transported along the. Here, the iron material 27 . Of the ion gun 24 . The operation of the gas introduction port 30. is maintained constant while introducing N ₂ gas. The ferromagnetic metal thin film of the present invention can be formed by introducing a more appropriate amount of oxygen gas.

The thickness of the magnetic layer in the present invention is generally 0.02 to 5.0.
μm, preferably 0.05 to 2.0 μm.

As the non-magnetic substrate used in the present invention, plastics such as polyethylene terephthalate, polyimide, polyamide, polyvinyl chloride, cellulose triacetate and polycarbonate are used.

A lubricating layer may be formed on the magnetic layer in the magnetic recording medium of the present invention. As the lubricating layer, a fatty acid having 12 to 18 carbon atoms, a metal salt of the fatty acid, silicone oil, and 2 carbon atoms are used.
The fatty acid ester etc. which consist of -20 monobasic fatty acid and C3-C12 monohydric alcohol are used. The addition amount is preferably 0.5 to 20 mg / m ² on the magnetic layer.

In the magnetic recording medium of the present invention, a packing layer may be provided on the surface of the non-magnetic substrate opposite to the magnetic layer side, if necessary.

Further, a layer made of an organic substance or an inorganic substance may be provided between the magnetic layer of the metal thin film and the non-magnetic substrate.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

A magnetic thin film was prepared using the apparatus shown in FIG. Substrate 2. Polyethylene terephthalate film (1
3 μm thick) and 99.9% Fe by electron beam 5.
Dissolved and evaporated by. Although not explicitly shown in the figure, the evaporation rate was monitored by a film thickness monitor (quartz oscillation type) so as to be constant at 5Å / S. At the same time Kaufman type ion gun 6. N ₂ gas was introduced into the reactor to activate it. At this time, the accelerating voltage was 0.3 kV and the ion current value was 5 mA, and the degree of vacuum was 5 × 10 ⁻⁵ Torr in this state.
Further, O ₂ gas was introduced from the gas introduction port 8 . First, gas inlet 8. The introduction of O ₂ from the beginning to the end of the film formation has a degree of vacuum of 3 × 10 ⁻⁴ Torr to 5 × 10 ⁻⁵ Tor.
The thickness was changed to rr, and the film was formed to a thickness of 2000Å. The thin film sample A produced at this time was AE
When S analysis and element content analysis in the film depth direction were performed, the pattern shown in FIG. 3 was obtained. Next is the gas inlet
8. O _{2 was} introduced so that the degree of vacuum was 1 × 10 ⁻⁴ Torr from the beginning of film formation to the end of film formation, and O ₂ was introduced under the same other conditions. Sample B
And The results of this thin film AES analysis are shown in FIG. The thin film sample prepared in this way was placed in an atmosphere of 60 ° C and 90% RH for 14
It was stored for a day, then taken out and dried, and then the Scott tape test and the still measurement were performed.
In the Scottish tape test, cellophane tape was attached on the thin film surface of the sample, and peeled off to see if the film was peeled. For steel measurement, a sample is cut into a size of 8 mm x 100 mm, a leader tape is joined before and after cutting, and the temperature is 23% at 10% with a testing machine modified by FLJIX-8 manufactured by Fuji Film.
It was performed under an RH atmosphere.

That is, it can be seen that the magnetic recording medium of the present invention has good adhesion between the substrate and the magnetic thin film even after long-term storage, and is excellent in storability.

〔The invention's effect〕

The magnetic recording medium of the present invention is excellent not only in rust resistance but also in the adhesion between the substrate and the magnetic thin film after long-term storage, and the storage stability is remarkably improved.

[Brief description of drawings]

1 and 2 show an apparatus for producing the magnetic recording medium of the present invention. 2, 22: Non-magnetic substrate, 6, 24: Ion gun 4, 27: Evaporation material, 5, 28: Electron beam 8, 30: Gas inlet, 23: Cooling drum FIG. 3 shows the magnetic recording medium of the present invention ( AES of sample A)
It is a profile. FIG. 4 is an AES profile of a comparative sample (sample B).

Claims (1)

[Claims] 1. A magnetic recording medium comprising, as a magnetic layer, a ferromagnetic metal thin film composed mainly of iron formed on a non-magnetic substrate, wherein the ferromagnetic thin film contains at least nitrogen atoms and oxygen atoms. A magnetic recording medium characterized in that the atomic ratio of oxygen to iron contained in the ferromagnetic thin film gradually increases from near the surface of the thin film toward the substrate.