JPH08316083A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE: To enhance the magnetic characteristics by bringing a intensively heated body made of a high melting point material having high specific heat into contact with a gas and ionizing atoms in the gas when an iron based magnetic layer is formed as a continuous magnetic body while introducing a gas containing at least one of nitrogen, oxygen and carbon gases. CONSTITUTION: Iron is placed in a crucible 6 and a vacuum chamber 1 is evacuated before an electron beam is projected to the iron from an electron gun 7 in order to fuse and evaporate the iron. An electron beam is also projected from an electron gun 12 to a body 10 having high specific heat while introducing nitrogen gas through a ventilation nozzle 13 toward the body 10 thus generating plasma. A PET base film 2 is then fed from a winding roll 3 to a rewinding roll 4. Subsequently, a DLC layer is formed on the PET film 2 by ECR plasma CVD in another chamber and a fluorine based lubricant is applied onto the protective film and an Al back coat layer is formed on the rear side by vacuum deposition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium, and more particularly to an iron-based magnetic layer such as Fe-N or Fe-N.
The present invention relates to a method of manufacturing a magnetic recording medium, which comprises forming a magnetic layer of —O, Fe—C, Fe—C—O, or Fe—N—C—O system.

[0002]

2. Description of the Related Art A continuous magnetic substance type magnetic recording medium formed by vapor deposition or sputtering has a high magnetic substance filling rate, so that it has a large saturation magnetization in a thin film as compared with a coating type magnetic recording medium and is suitable for high density recording. And is used in various application fields. Iron, cobalt, nickel, or an alloy thereof is generally used as the ferromagnetic material for such a continuous magnetic material type magnetic recording medium. Of these, cobalt is a ferromagnetic material that is excellent in both coercive force and saturation magnetization, but since cobalt alone has a problem in corrosion resistance, it is common to increase the corrosion resistance by alloying it with nickel, etc. even though cobalt is the main component. For example, a cobalt-nickel alloy containing about 20% by weight of nickel is used as a vapor deposition tape.

[0003] However, cobalt is a scarce resource, and there is concern about supply, and it is a material that has problems in terms of cost and environment. Therefore, it is desired to reduce the amount of cobalt used in the magnetic recording medium. Here, as an alternative to cobalt, it is conceivable to use iron, which is a material with excellent saturation magnetization and is an inexpensive resource that is abundant on the earth. However, iron is very susceptible to oxidation and has less corrosion resistance than cobalt. Therefore, in order to effectively utilize the high saturation magnetic flux density of iron in the magnetic recording medium while compensating for this drawback, Fe-N, Fe-NO, Fe-
Attempts have been made to form C, Fe—C—O, Fe—N—C—O based magnetic films.

[0004]

Such a magnetic film is formed, for example, by sputtering iron in a desired gas atmosphere with iron as a target, or by introducing nitrogen ions by a so-called ion assist method while depositing iron. It However, for example, sputtering may be performed with N ₂
If it is performed in an atmosphere, the film formation speed is slow, which makes it unsuitable for industrial-scale manufacturing, and it is not suitable for recording / reproduction using a ring head because it is not possible to obtain a column structure that grows in an oblique direction. There is. There is also a problem in the uniformity of the obtained iron nitride film.

When the iron-based magnetic layer is formed by vapor deposition,
Although it is faster than sputtering, it is still unsatisfactory industrially, and the resulting nitride film is not uniform enough. This is because in the ion assist method, nitrogen gas is excited by an ion gun and nitrogen ions are injected at a position where iron vapor is incident and deposited on the base film, so that the reaction between iron and nitrogen is not sufficiently performed. Is considered to be. As a result, the distribution of nitrogen atoms in the film becomes non-uniform, high magnetic properties cannot be obtained, and the reaction is insufficient. That is, the vapor deposition rate is limited by the ability of the ion gun.

[0006]

According to the present invention, nitrogen,
While introducing a gas containing at least one of oxygen and carbon, in forming a continuous magnetic body type iron-based magnetic layer on the running base film by vapor deposition or sputtering,
A high specific heat body made of a high melting point material is placed in contact with the gas. The high specific heat body is strongly heated by irradiation with a high energy ray such as an electron beam, thereby ionizing atoms in the gas. To enhance the reaction between iron vapor and nitrogen,
The high specific heat material is preferably arranged in a vapor passage area from a vapor deposition source such as a crucible or a target toward the base film. Also, for example, when a shielding plate is used for performing oblique vapor deposition, the high specific heat body is suspended on this shielding plate,
It is desirable to ensure a suitable reaction of iron vapor with nitrogen.

The high specific heat body used in the present invention is composed of a substance having a large heat capacity and a high melting point. For example, constant pressure molar heat capacity Cp at 25 ℃ is 30 J / kmol
As described above, it is preferably 60 J / kmol or more if possible. In terms of thermal conductivity, 3 × 10 ⁻² cal · deg · sec or less is preferable, and 3 × 10 ⁻³ cal · deg · sec or less is particularly preferable. The melting point should be at least 1800 ° C or higher, if possible
It is preferably 2000 ° C. or higher. Various ceramics, Al ₂ O ₃ , MgO,
BN, Fe ₂ N, Fe ₃ N and the like. The volume, shape, suspension method, etc. of the high specific heat element are appropriately selected according to the application, but when the high specific heat element is placed in the vapor passage area, it should not hinder the uniform diffusion of vapor to the base film. I have to

The gas to be vented to the high specific heat material is selected according to the desired characteristics of the iron-based magnetic layer, and nitrogen gas, oxygen gas, etc. as a simple substance, carbon dioxide, ammonia gas, etc. It is supplied as a contained gas or a mixed gas thereof. The flow rate of the gas is not limited, and is determined in consideration of the type of gas, the desired film formation rate, the output of the electron gun, and the like. According to the present invention, Fe-N, Fe-NO, Fe
-C, Fe-C-O, although Fe-N-C-O based magnetic film can be suitably obtained in good film homogeneous Fe ₄ N film having, for example, high coercive force and corrosion resistance be able to.

Although polyethylene terephthalate is preferable as the base film, various polyester and polyolefin materials can be used in addition to the above, and the thickness is about 3 to 50 μm. In addition, an oxidizing gas can be introduced during vapor deposition to improve coercive force and durability. The degree of vacuum during vapor deposition is about 10 ⁻⁴ to 10 ⁻⁷ Torr. Further, a back coat layer, a protective layer such as DLC (diamond-like carbon) and SiO ₂ and a lubricating layer can be provided according to a conventional method.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of an apparatus which can be used for carrying out the manufacturing method of the present invention. In the vacuum chamber 1 exhausted by a vacuum pump (not shown), the base film 2
Is transported on the cooling can roll 5 from the unwinding roll 3 to the winding roll 4. A crucible 6 containing a ferromagnetic metal is arranged below the vacuum chamber, and an electron beam from an electron gun 7 melts and vaporizes the metal inside to obtain a vapor deposition atmosphere. A shielding plate 8 is arranged so that the incident angle of the vapor is limited to an oblique direction, and a nozzle 9 is provided in the vicinity of the cooling can roll 5 in order to improve the coercive force and durability by supplying an oxidizing gas during vapor deposition. It is located in. The high specific heat body is shown at 10 and here is made of spherical Al ₂ O ₃ suspended from the tip of the shield 8 by a tungsten wire 11. The electron gun 12 is arranged so as to irradiate the high specific heat body 10 with an electron beam, and a ventilation nozzle 13 is arranged below the vacuum chamber in order to ventilate a gas such as nitrogen gas into the high specific heat body for ionization. It is set up.

Example 1 Fe was put in the crucible 6 by using the apparatus shown in FIG. After evacuating the vacuum chamber 1 to 10 ^-6 Torr, the electron gun 7
Iron in the crucible was melted and evaporated by irradiating it with an electron beam at 16 kW to create a vapor deposition atmosphere. Further, an electron beam was applied from the electron gun 12 to the high specific heat body 10 at 12 kW, and at the same time, nitrogen gas was introduced from the ventilation nozzle 13 at 100 SCCM toward the high specific heat body to generate plasma. The high specific heat body had a diameter of 0.8 cm, and the base film 2 was made of PET having a thickness of 7 μm, and was made to travel from the unwinding roll 2 to the winding roll 3 at a speed of 2 m / min.

Then, in a chamber separate from that obtained, E
Microwave power 600W by CR plasma CVD method
Then, a diamond-like carbon (DLC) layer was formed at 70 Å. Fluorine-based lubricant (trade name FOMBLI on this protective layer
NAM2001) with a thickness of 20Å and a back coat layer of aluminum 0.2 μm on the back side of the PET film.
It is attached by the vacuum evaporation method with the thickness of, and cut into 8 mm width,
The cassette was loaded to make an 8 mm video cassette.

Example 2 In Example 1, oxygen gas was simultaneously supplied from the nozzle 9 to 20 S.
It was introduced at the flow rate of CCM. Others were operated in the same manner to produce an 8 mm video cassette.

Comparative Example 1 The high specific heat body 10, the wire 11, the electron gun 12 and the ventilation nozzle 13 were removed from the apparatus of Example 1, and a Kaufman type ion gun 15 as shown in FIG. Nitrogen ion was implanted. The flow rate of nitrogen gas to the Kauffman type ion gun 15 was 20 SCCM, the current applied to the filament was 8 A, and the accelerating voltage was 800 V. Crucible 6
In the same manner as in Example 1, Fe was added, and the vapor deposition atmosphere was such that the vacuum chamber 1 was evacuated to 10 ^-6 Torr and then the electron gun 7 radiated an electron beam at 20 kW to melt and evaporate iron in the crucible. Obtained. The film thickness and running speed were the same as in Example 1. Others are the same as in Example 1,
An 8 mm video cassette was made.

Comparative Example 2 In Comparative Example 1, 20 S of oxygen gas was simultaneously supplied from the nozzle 9.
It was introduced at the flow rate of CCM. Others were operated in the same manner to produce an 8 mm video cassette.

The coercive force, the saturation magnetic flux density and the squareness ratio of the 8 mm video cassettes obtained in the examples and the comparative examples were measured using a sample vibrating magnetometer (VSM), and Auger spectroscopic analysis was performed to measure the thickness direction. The nitrogen atom distribution and the film thickness were measured. The results are shown in Table 1.

[0017]

[Table 1]

Further, the samples obtained in Example 1 and Comparative Example 1 were subjected to X-ray diffraction. Deviation angle 2θ is 40 to 50 °, X
The output of the wire tube was 30 mA and 100 kV, and Cu Kα rays were used. The results are shown in FIGS. 3 and 4. The vertical axis of the figure is the intensity by the count value (cps: count per sec), and the horizontal axis is 2
θ (angle). In the case of Example 1, since the reactivity is good, the pattern of the Fe ₄ N phase having good crystallinity can be clearly seen. On the other hand, in Comparative Example 1, unlike Example 1, the peak is unclear and is amorphous. This seems to be due to poor reactivity.

[0019]

As is clear from the results of the examples, according to the method of the present invention, the atoms in the gas are favorably ionized, so that the reactivity is improved and the iron-based material in which the nitrogen atoms are uniformly distributed. Can be obtained. As a result, a higher coercive force and a higher saturation magnetic flux density can be obtained as compared with the conventional method.

[Brief description of drawings]

FIG. 1 is a schematic view schematically showing an apparatus used in an embodiment according to a manufacturing method of the present invention.

FIG. 2 is a schematic view showing an apparatus used for carrying out an example of a manufacturing method according to a conventional method in contrast with the apparatus shown in FIG.

FIG. 3 is a graph showing an X-ray diffraction pattern in Example 1.

FIG. 4 is a graph showing an X-ray diffraction pattern in Comparative Example 1.

[Explanation of symbols]

 1 Vacuum Chamber 2 Base Film 3 Unwinding Roll 4 Winding Roll 5 Cooling Can Roll 6 Crucible 7, 12 Electron Gun 8 Shielding Plate 9 Nozzle 10 High Specific Heat Body 11 Tungsten Wire 13 Venting Nozzle 15 Kaufmann Ion Gun

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsumi Sasaki 2606 Akabane Kai, Cho, Haga-gun, Tochigi Prefecture Kao Co., Ltd. (72) Inventor Yuzo Matsuo 2606 Akabane Kai, Cho, Haga-gun, Tochigi Research Institute, Kao Corporation ( 72) Inventor Akira Shiga 2606 Akabane, Kabane-cho, Haga-gun, Tochigi Prefecture Kao Co., Ltd. (72) Inventor Junko Ishikawa 2606 Akabane, Kai-cho, Haga-gun, Tochigi Kao Corporation

Claims (4)

[Claims] 1. A method for producing a magnetic recording medium, comprising forming a ferrous magnetic layer on a running base film while introducing a gas containing at least one of nitrogen, oxygen and carbon. A method for producing a magnetic recording medium, comprising: ionizing atoms in the gas by bringing a highly specific heat body made of a substance and ignited into contact with the gas. 2. The manufacturing method according to claim 1, wherein the high specific heat body is arranged in a vapor passage region from an iron source to the base film, and is strongly heated by electron beam irradiation. 3. The manufacturing method according to claim 1, wherein the high specific heat body is suspended on a shielding plate that limits an incident angle of steam from an iron source to the base film. 4. The high specific heat material is Al ₂ O ₃ , MgO, BN, Fe.
The manufacturing method according to any one of claims 1 to 3, comprising ₂ N, Fe ₃ N, or other ceramics.