JPH0778866B2 - Magnetic recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having an iron nitride thin film having good magnetic characteristics and strong strength.

[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, magnetic recording media in which a metal thin film is formed on a non-magnetic substrate are being developed. This is a method for forming a metal thin film on a non-magnetic substrate by vapor deposition method such as direct air vapor deposition, sputtering, ion plating, or plating method such as electric plating or electroless plating. However, since metal is typical,
Hereinafter, a magnetic recording medium having this will be 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 type 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 simplifies the 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 suspended type magnetic recording medium. In particular, magnetic recording media used as cassette tapes, video tapes, etc., are rubbed on the metal thin film due to friction because the surface of the media is rubbed by the magnetic head during recording and reproduction. 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 low durability. This type of magnetic recording medium has a problem that since it uses a smoother substrate than that of the coating type, it causes large friction and is likely to cause nicks, and is inferior to the coating type in the still durability of VTR. .

In order to improve the weather resistance and durability of such a metal thin film magnetic recording medium, a Fe-based thin film containing FeN of 5% or more represented by FeyN (where y is 2 to 8) is used as a base. A magnetic recording medium on a material has been proposed (JP-A-60-2349).
62, JP-A-60-236113).

[Problems to be solved by the invention]

However, although the corrosion resistance of the magnetic recording medium having the Fe-based thin film containing iron nitride as the magnetic layer is improved to some extent, the magnetic characteristics are not so good.

Therefore, the present invention is intended to obtain a magnetic recording medium having excellent corrosion resistance and good magnetic characteristics.

[Means for solving problems]

The present invention relates to a magnetic recording medium provided with an iron nitride thin film, in which iron nitride contains γ′-Fe ₄ N to form a magnetic layer with good magnetic properties, and FeO _X to form a strong thin film. .

That is, according to the present invention, α-Fe and γ'-Fe are formed on a non-magnetic substrate.
A magnetic recording medium provided with an iron nitride thin film made of a mixture of ₄ N, α ″ -Fe ₈ N, ε-Fe _2-3 and FeO _x , wherein α-Fe: ε-Fe _2-3 N: γ ′ -Fe ₄ N: α ″ -Fe ₈ N = a: b: c: d, a + b + c + d = 1 a ≧ 0.10, 0.70 ≧ b ≧ 0.20, c ≧ 0.05. It is a medium.

The iron nitride thin film according to the present invention is not composed only of pure iron nitride, but includes α-Fe, ε-Fe _{2 to 3} N,
It contains so-called iron nitride-based substances such as γ'-Fe ₄ N and α "-Fe ₈ N, and also contains iron oxide generally represented by FeO _x .
The content of ε-Fe _{2 to 3} N must be within the range of 0.70 ≧ b ≧ 0.20 with respect to the sum of the above a, b, c and d. If the content exceeds 0.70, the coercive force is increased. Markedly reduced. γ′-Fe
₄ N must be greater than 0.05 of the above sum. Further, the FeO _X is 0.1 to 2: 1 with respect to the sum of α-Fe and Fe _X N.
Is preferable.

The magnetic layer made of the iron nitride thin film is formed on the non-magnetic substrate by depositing a magnetic vapor deposition film on the surface of the non-magnetic substrate by the so-called oblique vapor deposition method. In this vapor deposition, iron contained in the crucible is heated by an electron beam to evaporate iron atoms and obliquely impinge on the non-magnetic substrate for vapor deposition.On that occasion, an ion gun is provided on the crucible. Nitrogen ions may be supplied from the above, and oxygen may be supplied to the ion gun together with nitrogen, or may be contained in the vapor deposition zone as an atmospheric gas.

By adjusting the intensity of the electron beam and adjusting the amount of nitrogen ions supplied and the amount of oxygen gas supplied, the amount of iron, nitrogen and oxygen contained in the magnetic layer can be controlled within a predetermined range. You can

FIG. 1 shows an apparatus 1 for forming a metal thin film by vapor deposition.
Thus, the iron nitride thin film is deposited on the surface of the non-magnetic substrate 2. Iron 4, which is a vapor deposition material, is placed in the crucible 3, and an electron beam is radiated from the electron gun 5 to vaporize iron atoms. Nitrogen 7 is supplied to the ion gun 6, ionized nitrogen is supplied to the vapor deposition region, and ammonia and oxygen are supplied from the introduction pipe 8. The degree of vacuum during vapor deposition is generally about 10 ^-4 to 10 ^-6 Torr.

The thickness of the magnetic layer provided on the magnetic recording medium of 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, a plastic substrate such as polyethylene terephthalate, polyimide, polyamide, polyvinyl chloride, cellulose triacetate, or polycarbonate is used.

A lubricant layer may be formed on the magnetic layer in the magnetic recording medium of the present invention, and examples of the lubricant include fatty acids having 12 to 18 carbon atoms, metal salts of the fatty acids, silicone oil, and 2 carbon atoms.
At least one selected from fatty acid esters consisting of ~ 20 monobasic fatty acids and C3-12 monohydric alcohols is used. The amount added is 0.5 to 20 g / m ² on the magnetic layer.
It is good to exist.

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

Further, a layer made of an organic substance or an inorganic substance may be provided between the magnetic layer of the iron nitride 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 these examples.

Example 1 Using the vapor deposition apparatus shown in FIG. 1, a polyimide film having a thickness of μm was used as a substrate, on which iron was deposited by oblique vapor deposition.
A magnetic layer containing nitrogen and oxygen was formed to manufacture a magnetic tape. The degree of vacuum during vapor deposition was set to 5.0 × 10 ⁻⁵ Torr. Put iron in the crucible and apply an electron beam with an electron gun to deposit the iron, and use a Kaufman type ion gun to convert the nitrogen gas into an ion beam to supply nitrogen ions, and also to the substrate part, an equal amount mixed gas of ammonia and oxygen. Was introduced to carry out vapor deposition. N
A thin film having the composition shown in the table below was formed by variously changing the ion irradiation dose and the introduction amounts of NH ₃ and O ₂ . Vapor deposition rate is 10Å / s
ec.

The coercive force (Hc), squareness ratio (SQ), and de-scratching test with Scotty tape were performed on them. The results are shown in the table below.

Measurement method: α-Fe, ε-Fe _2-3 N, γ′-Fe ₄ N, α ″-
The amount ratio (atomic%) of Fe ₈ N was determined by Moessbauer spectroscopy.
Determined from peak intensity ratio.

The amount of FeO _{x was} determined by the Auger electron spectroscopy (AES) and the amount ratio to FeN _x 100 was determined. Hc, SQ: Measured by VSM (vibrating magnetometer).

Hakuri; Scott tape is attached to the film surface and peeled off.

Not peeled off ○, slightly peeled off △, whole peeled off ×.

〔The invention's effect〕

The magnetic recording medium of the present invention has excellent corrosion resistance and good magnetic properties. This is because the iron nitride thin film contains a sufficient amount of γ'-Fe ₄ N and thus has a large magnetic property. As shown in Table 1, the coercive force (Hc) and squareness ratio (SQ) are large. In addition, FeO _X
Since it also contains, the film is tough, and good results can be obtained even with a film peeling test with Scotty tape. Therefore, the magnetic recording medium of the present invention is highly practical.

[Brief description of drawings]

FIG. 1 shows a vapor deposition apparatus for manufacturing the magnetic recording medium of the present invention. 1 ... Vapor deposition apparatus, 2 ... Non-magnetic substrate 3 ... Crucible, 4 ... Iron (vapor deposition material) 5 ... Electron gun, 6 ... Ion gas 7 ... Nitrogen 8 ... Ammonia, oxygen introduction tube

Claims (1)

[Claims] 1. An α-Fe, γ'-Fe ₄ N, α ″ on a non-magnetic substrate.
A magnetic recording medium provided with an iron nitride thin film made of a mixture of —Fe ₈ N, ε-Fe _{2 to 3} N, and FeO _X , wherein α-Fe: ε-Fe _{2 to 3} N: γ′-Fe ₄ N : α ″ -Fe ₈ N = a: b: c: d, a + b + c + d = 1 a Magnetic recording medium characterized by satisfying the relationship of a ≧ 0.10, 0.70 ≧ b ≧ 0.20, c ≧ 0.05.