JPS63237211A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability under low humidity by incorporating at least nitrogen atoms. and oxygen atoms. into a thin ferromagnetic film and increasing the atom. ratio of the oxygen to be incorporated with respect to iron gradually from a substrate toward the surface of the thin film. CONSTITUTION:Formation of the desired thin film magnetic layer is executed by maintaining a specified evaporation rate of a iron material 4, then changing the compsn. of a gas 7 to be introduced into an ion gun 6 with time during the film formation. For example, the film can be formed by a method consisting in increasing the amt. of the gaseous O2 to be incorporated gradually into the gas, in which the content of N2 is 100% in the initial period of the film formation. The amt. of the gaseous O2 introduced through a gas introducing port 8 is otherwise increased with time under the conditions under which the gaseous N2 is used for the gas 7 in the state of constantly operating the ion gun 6 while the evaporation rate of the iron material 4 is maintained constant. The magnetic recording medium having the improved durability of the thin magnetic film under the low humidity is thus obtd.

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 durability.

[Conventional technology]

Is ferromagnetic powder used as a magnetic recording medium? A droplet type material obtained by coating a magnetic paint dispersed in an organic binder on a non-magnetic substrate and drying it has been widely used. However, since this coated magnetic recording medium mainly uses metal oxide powder as the ferromagnetic powder, its saturation magnetization is low, and since it contains an organic binder, the entire concentration of ferromagnetic material in the magnetic layer cannot be increased. Therefore, it is not suitable for high-density recording, and has drawbacks such as a complicated manufacturing process.

In recent years, the demand for high-density recording has increased, and in response to this, magnetic recording media formed on a thin metal film on a non-magnetic substrate have been developed. A thin metal film is formed on a non-magnetic substrate by a plating method such as electroplating or electroless plating, and the magnetic material is not limited to metal, but since metal is a typical example, these are included below. The magnetic recording medium is called a metal thin film 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.

Is this gold a 5S @ metal τ binder with large saturation zero magnetization in thin film magnetic recording media? Since it can be formed as a thin film in a non-containing state, it has a higher coercive force and a thinner film than the coated type, has less effect of demagnetization in the short wavelength range, realizes high-density recording, and is easy to manufacture. It is attracting attention because it simplifies the process.

However, although the metal thin film of a metal thin film type magnetic recording medium appears to have a uniform and smooth metal surface, its microstructure is rough and has a structure in which fine metal particles are lined up! As a result, this type of magnetic recording medium is inferior in 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, the friction will cause damage. The magnetic recording medium falls off and clogs the head, thereby damaging the head and the magnetic recording medium.

Furthermore, metal thin film magnetic recording media have a problem of poor durability. This type of magnetic recording medium has problems such as high friction and easy scratching because the metal thin film is smooth, and is inferior to the coated type in terms of stealth durability in VTRs, etc.

The ninth method for completely improving the weather resistance and durability of such metal thin film type magnetic recording media is to apply surface nitriding treatment by ion blasting (Japanese Unexamined Patent Publication No. 2003-33306) and to form a silicon nitride film by sputtering. How to set up (Tokukaisho!
J-jOJOj), 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-53-tj≠03), nitrided metal on a magnetic metal thin film A method in which the entire thin film is used (% opening/closing jμ-7≠37//) is 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 Yorotsuno ξ Patent No. R32R or Japanese Patent Application Laid-Open No. Shoj Tarr R7RO. Furthermore, the applicant has previously proposed a magnetic recording medium (Japanese Unexamined Patent Application Publication No. 6-117) in which a magnetic thin film mainly composed of iron oxynitride is provided on a non-magnetic substrate.
/-j≠No.023), but this magnetic thin film contains the composition expressed by the following compositional formula % (where 0.2!≦X+Y≦0.60). Ta.

[Problems to be solved by the present invention]

However, although the above-mentioned method greatly improves weather resistance, there is a problem with the durability of the magnetic thin film, especially when the same part of the medium is entirely slid by a magnetic head at low temperatures (usually in still mode in VTRs). However, there was a need for improvements due to the drawback of poor durability.

Therefore, an object of the present invention is to provide a magnetic recording medium that has excellent still durability, especially at low humidity.

[Means for determining the meeting point]

That is, the present invention provides a magnetic recording medium in which a ferromagnetic metal thin film mainly made of iron is provided as an all-magnetic layer formed on a nonmagnetic substrate, 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 the substrate toward the surface of the thin film, that is, gradually increases as the distance from the substrate increases in the depth direction of the ferromagnetic thin film. The present invention relates to a magnetic recording medium characterized by the following.

The ferromagnetic thin film containing iron, nitrogen, and oxygen atoms as used in the present invention is a complex tetramer or composite whose main components are pure iron, iron nitride, and iron oxide.

For example, regarding iron nitride, ε-Fe2,3N1γ-F
It can have a crystal structure such as e4N%Fe16N2, and its composition ratio can be controlled to a certain extent by fully controlling the film forming conditions.

In the present invention, furthermore, in the depth direction of the ferromagnetic thin film, the ratio of oxygen atoms to iron atoms contained in the thin film is gradually increased as the distance from the nonmagnetic substrate increases. This atomic ratio of oxygen to iron can be analyzed by Auger electron spectroscopy (AES), and when obtaining information in the depth direction, for example, using argon ions to form a magnetic thin film? A widely known method is to perform analysis while etching.

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 stimulate nitriding or oxidation reactions during film formation, ion blating or ion beam irradiation (so-called ion beam assisted vapor deposition, etc.) is used in combination. Figure 1 shows an example of this, in which a non-magnetic substrate (gold) is fixed, and an iron material (4) is placed on top of this.
．． Total electron beam5. When the film is deposited by decomposition and evaporation using the ion gun 6. Fully operate to form an iron oxynitride film. A gas 7 containing nitrogen and oxygen atoms (for example, a combination of N2 gas, NH3 gas, NOx gas, 02 gas, etc.) is introduced into the ion gun, and all of the ions, radicals, atoms, etc. are produced in the ion gun. The dashi is irradiated onto the substrate. Alternatively, the sound quality of the reaction atmosphere can be obtained by introducing an atmosphere gas through the gas inlet.

To obtain the thin film magnetic layer of the present invention using the apparatus shown in FIG.
Iron material 4. The ion gun was used during film formation while keeping the evaporation rate constant.6. What is necessary is to change the composition of the gas 7 introduced into the chamber over time. For example, it can be created by a method in which the amount of 02 gas mixed into 100% N2 gas is gradually increased in the initial stage of film formation. Chirui is also an iron material4. The evaporation rate of 6. The amount of 02 gas introduced from the gas inlet 8° is increased over time under the condition that the gas is 7° rNz gas while the gas is kept constant. FIG. 2 shows an ion gun 24. It is shown that a fully integrated iron nitride oxide film can be created. According to this device, the base body 22-
is the cooling drum 23. While being transported along the magnetic field, the magnetic film is irradiated with a flow of iron black air and a flow of nitrogen ions or nitrogen + oxygen ions, thereby forming a magnetic film. Here, iron material U
Keeping the evaporation rate constant above? The operation of the ion gun is also N2
While introducing the gas, keep it constant and open the gas inlet 30. 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 of the present invention is generally 0.02 to t,
o/j7rt, preferably o, or~ko, 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 of the magnetic recording medium of the present invention, and the lubricating layer may include a fatty acid having 12 to /r carbon atoms, a metal salt of the fatty acid, a silicone oil, and a silicone oil having 2 to 2 carbon atoms.
A fatty acid ester consisting of 20 monobasic fatty acids and an example alcohol having 3 to 12 carbon atoms is used. The amount of addition is preferably 0.j-20 to /'m2 on the magnetic layer.

In the magnetic recording medium of the present invention, a back 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.

The device shown in Figure 7? A magnetic thin film was created using this method. The substrate 2 is a polyethylene terephthalate film (13
μm thickness) all used, Tata, Tachi Fe1-electron ° beam 5
．． The mixture was dissolved and evaporated. Although it is not clearly shown in the figure, the film thickness monitor (crystal oscillation type) is used to monitor the entire evaporation rate L! A/s was kept constant. At the same time, Kaufuma/type ion gun6. N2 gas was introduced into the reactor and the reactor was operated. At this time, the acceleration voltage is 0, J kV ion current value is 7 m, and the degree of vacuum is t x t o 5 in this state.
It was made to be T Or r. Furthermore, the gas inlet 8. All 02 gas was introduced.

First, gas inlet 8. The degree of vacuum was 5 x 16 5 Tor r from the beginning of film formation to the end of film formation.
The film was formed to have a thickness of 2000A by changing the current from JXio to 4Torr.

The thin film sample created at this time was analyzed by Aa-AES, and the element content in the film depth direction was analyzed. As a result, the hair turn shown in FIG. 3 was obtained. Next, the gas inlet 8, the vacuum level of 7X from the beginning of the gold film formation to the end of the gold film formation.
02 was introduced to keep the pressure constant at 7.7-4 Torr, and the film formation session was conducted under the same conditions as above. Sample B
shall be. The results of AES analysis of this thin film are shown in Fig. μ. The thin film sample 'If''rm x 100yH was prepared in this way, and the still durability was measured by bonding the leader tape seven times before and after cutting.The test machine was a Fuji Photo Film F
UJIX-r2 has been modified so that it can measure the still time even with small samples. With this testing machine, 23
When the still time is measured in an atmosphere of °Cio%RH, the test piece of sample A maintains its normal state for more than 60 minutes, while the output of the test piece of sample B decreases by more than A dB in 73 minutes. A clear improvement in still durability of the recording medium under low humidity conditions was observed.

〔Effect of the invention〕

The magnetic recording medium of the present invention has excellent durability of the magnetic thin film under low humidity,
This is an iron nitride thin film magnetic recording medium that has excellent durability against magnetic heads, especially in VTR still mode.

[Brief explanation of drawings]

1 and 2 show an apparatus for producing the magnetic recording medium of the present invention. λ, 22: Non-magnetic substrate A, 2g: Ion Gunhiro, 27
: Vapor deposition material j, 2F: Electron beam t, 3O: Gas inlet 23: Cooling drum FIG. 3 shows the AES profile of the magnetic recording medium (Sample A) of the present invention. Figure 1 shows the AES profile of a comparative prototype (sample B). Patent applicant: Fuji Photo Film Co., Ltd. Figure 1 Figure 2 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 the substrate to the surface of the thin film. magnetic recording medium.