JPS63239615A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having an excellent preservable property by incorporating at least nitrogen atoms and oxygen atoms into a thin ferromagnetic film and increasing the atomic number ratio of the oxygen incorporated in the thin ferromagnetic film with respect to iron gradually from near the surface of the thin film toward a substrate. CONSTITUTION:The thin ferromagnetic metallic film which is formed on the nonmagnetic substrate and consists essentially of iron is provided as the magnetic layer. At least the nitrogen atoms and oxygen atoms are incorporated into the thin metallic film and the atomic number ratio of the oxygen incorporated in the thin ferromagnetic film is increased gradually from near the surface of the thin film toward the substrate. For example, an ion gun 6 is operated to form an iron oxynitride film at the time of fixing the nonmagnetic substrate 2, melting and evaporating the iron material 4 and depositing the film thereof on said substrate. Rust resistance is thereby improved and the adhesiveness between the substrate and the thin magnetic film after the long term preservation is simultaneously improved. The preservable property is markedly improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a metal thin film type magnetic recording medium that does not cause rust and has excellent storage stability.

[Conventional technology]

As magnetic recording media, coating-type media have been widely used, which are obtained by coating a non-magnetic substrate with a magnetic paint in which ferromagnetic powder is dispersed in an organic binder and drying the coating. However, this coated magnetic recording medium mainly uses metal oxide powder as the ferromagnetic powder, has a low saturation magnetization, and contains an organic binder, which makes it difficult to increase the concentration of ferromagnetic material in the magnetic layer. However, it is not suitable for high-density recording, and the manufacturing process is complicated.

In recent years, the demand for high-density recording has increased, and in response to this demand, good magnetic recording media have been developed by forming metal thin films on non-magnetic substrates. A thin metal film is formed on a non-magnetic substrate by a magnetic deposition method, or a plating method such as electroplating or electroless plating.The magnetic material is not limited to metals, but metals are typical. Therefore, a magnetic recording medium having this is hereinafter referred to as a gold-thin film type magnetic recording medium. Furthermore, since this type of magnetic recording medium 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 with high saturation magnetization can be formed as a thin film without containing a binder, so it has a higher coercive force and a thinner film than the coated type, and can be shortened. It is attracting attention because it has less effect of demagnetization in the wavelength range, enables high-density recording, and simplifies the manufacturing process.

However, although the metal thin film of a metal thin film type magnetic recording medium has an apparently uniform and smooth metal surface, its fine structure is rough and has a structure in which fine metal particles are lined up. In addition, it is easily corroded, and as a result, this type of magnetic recording medium has inferior weather resistance and corrosion resistance compared to coated magnetic recording media.

In particular, the surface of magnetic recording media used as cassette tapes, video tapes, etc. is rubbed by a magnetic head during recording and playback, so even if there is a very small amount of corrosive material on the thin metal film, it will fall off due to friction. This causes the head to become clogged, which causes damage to the head and the magnetic recording medium.

Furthermore, metal thin film magnetic recording media have a problem of poor durability. In this type of magnetic recording medium, the metal thin film is smooth, so there are problems such as high friction (easiness to cause stickiness), and it is inferior to the coated type in terms of still durability in VTRs, etc.

In order to improve the weather resistance and durability of such metal thin film type magnetic recording media, there are two methods: surface nitriding treatment by ion blasting (Japanese Patent Application Laid-open No. 2003-100002) and sputtering to form a silicon nitride film ( Tokukai Akira!
3-,! A method of forming a non-magnetic surface layer by exposing a magnetic film to discharge in an atmosphere such as nitrogen gas [JP-A-Sho J-J-r! ≠No. 03), a method of providing a nitrided metal thin film on a magnetic metal thin film (Japanese Unexamined Patent Publication No. Sho!≠-1≠31//), and the like are known. In addition, iron nitride or a magnetic thin film made of iron and iron nitride as disclosed in European Patent No. JJJr or Japanese Patent Application Laid-Open No. be. Furthermore, the present applicant has previously proposed a magnetic recording medium (Japanese Unexamined Patent Application Publication No. 2003-110013) in which a magnetic thin film containing iron oxynitride as a main component is provided on a non-magnetic substrate. The thin film has the following compositional formula 2 formula % C9, 0.4 in the formula! ≦χ+Y≦o, to).

[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 is insufficient, and improvements have been desired.

Therefore, an object of the present invention is to provide a magnetic recording medium with excellent storage stability.

[Means for solving problems]

That is, the present invention provides a magnetic recording medium comprising a ferromagnetic metal thin film mainly made of iron formed on a nonmagnetic substrate as a magnetic layer, in which the metal thin film contains at least nitrogen atoms and oxygen atoms. and the atomic ratio of oxygen to iron contained in the ferromagnetic thin film gradually increases from near the thin film surface toward the substrate, that is, in the depth direction of the ferromagnetic thin film, gradually increases as it approaches the substrate. The present invention relates to a magnetic recording medium characterized by comprising:

The ferromagnetic thin film containing iron, nitrogen, and oxygen atoms referred to in the present invention is a complex mixture or composite whose main components are pure iron, iron nitride, and iron oxide. For example, regarding iron nitride, g-Fe2-3N%r-Fe4N
It controls the crystal structure of Fe16N2, etc. 1, and its composition, ratio, etc. can be controlled to a certain degree by controlling the film forming conditions. In the present invention, the ratio of oxygen atoms to iron atoms contained in the ferromagnetic thin film is gradually increased as it approaches the non-magnetic substrate in the depth direction of the ferromagnetic thin film. However, since the oxygen content of the very surface of the thin film increases due to the presence of a natural oxidation layer, this region is excluded. The atomic ratio of oxygen to iron can be analyzed by Auger electron spectroscopy (AES), and to obtain information in the depth direction, for example, the analysis is performed while etching a magnetic thin film tube with argon ions. , is widely known.

A method for forming the ferromagnetic metal thin film of the present invention on a nonmagnetic substrate will be described below. The film formation method is a well-known oblique vapor deposition method. In order to cause a nitriding or oxidizing reaction during film formation, a combination of ion plating or ion beam irradiation (so-called ion beam assisted vapor deposition, etc.) is used. FIG. 1 shows an example of the non-magnetic substrate 2. is fixed, and the iron material ψ is placed on top of this.
, all electron beam! , when melting and evaporating and depositing a film, an ion gun at the same time! : to form an iron oxynitride film. The ion gun contains nitrogen and oxygen atoms (for example, N2 gas, NH3 gas, NOX gas, 0
(combination of two gases, etc.) are introduced, and their ions, radicals,
Atoms are created in an ion gun and irradiated onto the substrate. Alternatively, the reaction atmosphere can be changed by introducing an atmospheric gas through the gas inlet t.

In the apparatus shown in FIG. 1, in order to obtain the thin magnetic layer of the present invention, the evaporation rate of the iron material ≠ is kept constant, and the composition of the gas 2 introduced into the ion gun t during film formation is changed over time. It would be good if we could change it. For example, at the beginning of film formation, N2! Section 0, 02
! It is created using a method of gradually reducing the amount of 02 gas mixed in with 0 gas. Alternatively, under the condition that the evaporation rate of the iron material is kept constant, the ion gun t is also operated at a constant rate, and the gas 7 is N2 gas, the gas inlet? , the amount of 02 gas introduced from , is increased over time. FIG. 2 shows a device in which an ion gun λlLt is incorporated into a well-known winding vapor deposition apparatus, thereby making it possible to create a stripped iron oxide film. According to this device, the base body 22. is the cooling drum 23. While being transported along the iron group gas flow and nitrogen ions or nitrogen +
When the irradiation tube receives the oxygen ion flow, a magnetic film is formed. Here, the evaporation rate of the iron material is kept constant, and the operation of the ion gun is also kept constant while introducing N2 gas.

By introducing a more appropriate amount of oxygen gas, the ferromagnetic metal thin film of the present invention can be formed.

The thickness of the magnetic layer in the present invention is generally Q, Ocor, 1.
0 μm1 preferably 0.0j to 2.0 μm.

As the nonmagnetic 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, and the lubricating layer may include a fatty acid having 72 to /r carbon atoms, a metal salt of the fatty acid, a silicone oil, and a silicone oil having 2 carbon atoms.
A fatty acid ester consisting of ~20 monobasic fatty acids and a monohydric alcohol having 3 to 1λ carbon atoms is used. The amount of addition is preferably 0.3-20rn97m2 on the magnetic layer.

In the magnetic recording medium of the present invention, one layer may be provided on the surface of the nonmagnetic substrate opposite to the magnetic layer side, if necessary.

Furthermore, a layer made of an organic or inorganic material may be provided between the magnetic layer of the metal thin film and the nonmagnetic substrate.

〔Example〕

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

A magnetic thin film was created using the apparatus shown in FIG. The base material is polyethylene terephthalate film (1
3 μm thick), and 4Fe was heated using an electronic beam
, dissolved and evaporated. Although not clearly shown in the figure, a film thickness monitor (crystal oscillation type) was used to keep the evaporation rate constant at the monitor LjA/S. At the same time, N2 gas was introduced into the Kaufmann type ion gun and activated.

At this time, the acceleration voltage is 0.3 kV, the ion current value is ZWtA, and the degree of vacuum is in this state! ×10'forr friend. Furthermore, #)02 gas was introduced through the gas inlet.

First, the gas inlet! , the degree of vacuum from the beginning of gold film formation to the end of gold film formation is from EXlo 'Torr!
x10 Torr and the thickness is 2
000. When the resulting thin film sample was analyzed by At-AES and the element content in the depth direction of the film was completely analyzed, the pattern shown in FIG. 3 was obtained. Next, 02 was introduced through the gas inlet j so that the degree of vacuum remained constant at /X10' Torr from the beginning of film formation to the end of film formation, and film formation was carried out under the same conditions. Let's call it sample B. The results of this thin film AES analysis are shown in Figure 1. The thin film sample made in this way was
'Stored under Co4RH atmosphere for l≠ days, then taken out and dried, then tested with scotch tape.
And then perform still measurements.

In the Scotch tape test, a piece of tape was pasted on the surface of the sample thin film and peeled off to see if the film had peeled off. In addition, for steel measurement, cut the sample into a size of r x 1100t, join leader tape at the front and back, and use a modified Fujifilm FUJIX-r testing machine at 23°C/
(This was carried out under an IRH atmosphere.

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

〔Effect of the invention〕

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

[Brief explanation of the drawing]

1 and 2 show an apparatus for producing the magnetic recording medium of the present invention. -12coni non-magnetic substrate 4%24t=ion gun μ,
Core: Deposition material! , Kot=electron beam! , 30
:Gas inlet 23:Cooling drum FIG. 3 shows the AES profile of the magnetic recording medium C sample of the present invention. FIG. 1 shows the AES profile of comparative example prototype C sample B). Patent applicant: Fuji Photo Film Co., Ltd. Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] In a magnetic recording medium in which a ferromagnetic metal thin film mainly made of iron is formed on a non-magnetic substrate as a magnetic layer,
The ferromagnetic thin film contains at least nitrogen atoms and oxygen atoms, and the atomic ratio of oxygen to iron in the ferromagnetic thin film gradually increases from near the surface of the thin film toward the substrate. magnetic recording medium.