JPH0927110A - Magnetic recording medium and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve quality of a magnetic recording medium and to easily produce the medium by forming a base layer containing copper on a supporting body and forming a magnetic layer containing iron and nitrogen on the base layer. SOLUTION: A base layer 2 containing copper is formed by physical vapor deposition on a supporting body 1, and a magnetic layer 3 containing iron and nitrogen is formed by ion-assist physical vapor deposition method on the base layer 2. Because the crystal structure of copper is similar to the crystal structure of the iron nitrogen compd. and vapor deposition of copper on the supporting body is easy, vapor of the iron-nitrogen compd. can be easily deposited compared to the case of forming a magnetic layer 3 directly on the supporting body 1. The base layer 2 contains copper in the form of metal copper, copper compd. or copper alloy. As for the copper compd., CuO is used, and as for the copper alloy, Cu-Al alloy or Cu-Ni alloy can be used. The base layer 2 is preferably formed to 150-350Å thickness.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a magnetic recording medium and a method for manufacturing the same. More specifically, the present invention relates to a vapor deposition type magnetic recording medium having a magnetic layer containing iron and nitrogen and a method for manufacturing the same.

[0002]

2. Description of the Related Art Magnetic recording media, such as magnetic tape,
A conventional coating tape made by applying a magnetic paint in which magnetic powder is dispersed in a binder on a film that is a non-magnetic support, and a binder using a vacuum evaporation method that deposits a magnetic metal in a vacuum on the film And a vapor-deposited tape in which a magnetic layer of a metal thin film that does not contain any metal is adhered to a nonmagnetic support.

[0003] In recent years, magnetic recording is in the direction of high-density recording, and a vapor-deposited tape is considered to be promising for high-density recording because the magnetic layer does not contain a binder so that the density of a magnetic material can be increased. ing.

By the way, as the magnetic material for the magnetic layer formed on the non-magnetic support by the vacuum deposition method, Co type, Co--Ni type and Co--Cr type ferromagnetic alloys have been conventionally used. . However, Co, Ni and Cr are all expensive and have pollution problems. In this respect, Fe (metallic iron) is inexpensive and has no problem in terms of pollution safety, but it has the drawbacks of low coercive force, which is essential for high recording density, and low corrosion resistance. , Co—Cr based materials and magnetic layer materials replacing Fe are desired.

Under these circumstances, the base is made of Fe, which is inexpensive and does not cause environmental pollution, and oxygen, nitrogen, and nitrogen are deposited during the deposition of Fe in order to form a magnetic layer having high coercive force and corrosion resistance.
Ionizing and irradiating a gas such as carbon dioxide or a mixed gas thereof, by a so-called ion-assisted vapor deposition method, Fe-N system, Fe-C system, Fe-N-O system, Fe-C-N-O system Attempts have been made to form magnetic films such as.

[0006]

However, such Fe-N-based, Fe-C-based, Fe-N-O-based, Fe-C-N-O-based magnetic films obtain desired film characteristics. Therefore, it is necessary to reduce the film formation rate, which is disadvantageous in terms of production efficiency. Also,
Usually, a plastic film such as PET (polyethylene terephthalate) is used as the base film of the magnetic recording medium, but the iron-nitrogen based magnetic layer may have insufficient binding property at the interface with the film, Although a more stable film is formed by heating the film, such a method has a limit in terms of durability of the film.

[0007]

In view of the above situation, the present inventors provide a method for more efficiently producing a magnetic recording medium having a higher performance nitrogen-iron based magnetic layer. As a result of intensive studies, it was found that this object can be achieved by forming an underlayer made of a compound containing copper on a base film, and forming an iron-nitrogen based magnetic layer on the underlayer, thereby completing the present invention. Came to.

That is, the present invention provides a magnetic recording medium having an underlayer containing copper and formed on a support, and a magnetic layer containing iron and nitrogen formed on the underlayer. In such a magnetic recording medium, a step of forming an underlayer containing copper on a support by a physical vapor deposition method in a vacuum atmosphere, and then forming a magnetic layer containing iron and nitrogen on the underlayer by an ion assisted physical vapor deposition method. It is manufactured by a manufacturing method characterized by containing.

FIG. 1 is a schematic diagram showing the structure of the magnetic recording medium of the present invention. This magnetic recording medium includes a support 1, an underlayer 2 containing copper formed on the support 1 by a physical vapor deposition method, and iron and nitrogen formed on the underlayer 2 by an ion assisted physical vapor deposition method. And an iron-nitrogen based magnetic layer is formed more quickly. The reason is that copper is easy to deposit on a support, and since the crystal structure of copper is similar to the crystal structure of an iron-nitrogen-based compound, it is easier to form a magnetic layer on the support than copper. It is considered that this is because the vapor of the iron-nitrogen compound is likely to adhere.

The magnetic recording medium of the present invention has an underlayer formed on a support, and the underlayer essentially contains copper. Specifically, copper, a copper compound, a copper alloy, etc. are vapor-deposited on a support body, and a base layer is formed. Examples of the copper compound include CuO 2 and the like. Examples of the copper alloy include Cu-Al alloy and Cu-Ni alloy. The thickness of the underlayer is preferably 50 to 500Å, particularly preferably 150 to 350Å.

In the present invention, the magnetic layer is formed by a so-called ion assisted vapor deposition method in which nitrogen ions and other suitable ions are supplied while iron is vapor deposited. Specifically, Fe-N based mainly on Fe, Fe-N-O based, Fe-C-N
A magnetic layer made of a compound such as —O type is formed. The thickness of the magnetic layer is usually about 1500 to 2000Å. The ion-assisted deposition method for forming the magnetic layer can be performed by a conventionally known method.

Nitrogen gas is essential as a gas serving as an ion source in the ion assisted vapor deposition, and oxygen gas, carbon dioxide gas or the like is used alone or in combination according to the intended composition of the magnetic layer. At that time, the ion supply ratio may be determined in consideration of the type of gas, the film formation rate, the output of the electron gun, and the like.

FIG. 2 shows an example of a vacuum vapor deposition apparatus for oblique vapor deposition used for manufacturing the magnetic recording medium of the present invention. FIG.
In the vacuum container 21, a vacuum state is maintained by the turbo pump 22 and the rotary pump 23. The vacuum container
An unwind roll 24 and a take-up roll 25 are provided in 21. While being unwound from the unwind roll 24 and wound on the take-up roll 25, PET (polyethylene terephthalate),
The film 26 as a support made of polyimide, aramid, or the like travels and moves along a flat plate-shaped cooling plate 27 through which cooling water flows. Cooling water is supplied to the cooling plate 27 from a cooling water supply pipe 28 and drained from a drain pipe (not shown), and the cooling water is circulated and supplied from an external cooling water tank. Below the cooling plate 27, a MgO crucible 29 is placed. For example, 99.95% pure Fe is put in the crucible 29, and an electron beam gun 30 obliquely above the Fe surface in the crucible 29 is used. Irradiate with an electron beam.
As a result, Fe is heated and vaporized. During the deposition of Fe, the cooling plate is adjusted so that the angle of incidence α of the vapor flow of Fe from the crucible 29 on the film 26 falls within a desired range.
Set the inclination of 27. By employing such an oblique deposition method, the magnetic properties are improved by the magnetic anisotropy of the magnetic layer. Further, an ion gun 31 is arranged in a direction perpendicular to the vapor deposition surface of the film 26, and a mixed gas of N ₂ and O ₂ is supplied to the ion gun 31 to generate nitrogen ions and oxygen ions,
While depositing Fe on 26, the deposition surface is irradiated with the nitrogen ions and oxygen ions. Reference numeral 32 in the figure denotes a shielding plate for controlling the vapor deposition range on the film 6.

The material for the support of the magnetic recording medium of the present invention includes polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyethylene,
Polyolefin such as polypropylene; Cellulose derivative such as cellulose triacetate and cellulose diacetate; Polycarbonate; Polyvinyl chloride; Polyimide;
Plastics such as aromatic polyamide are used. The thickness of these substrates is about 3 to 50 μm.

A protective layer having a thickness of about 10 to 100 Å, a lubricating layer having a thickness of about 2 to 50 Å, and a back coat layer containing carbon black as a main component and having a thickness of about 0.2 to 1.0 μm may be provided. Good. As a raw material for forming these layers, conventionally known materials can be appropriately used. The back coat layer can also be formed by vapor-depositing a metal such as aluminum or an alloy thereof.

[0016]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 (1) Manufacture of magnetic recording medium An underlayer made of copper and having a thickness of 100 Å was formed on a PET film, and a Fe—N—O magnetic material having a thickness of 1600 Å was formed on the underlayer. A magnetic recording medium was manufactured by forming a layer, and further forming a back coat layer and a lubricating layer. The conditions for forming each layer are as follows. (a) Underlayer A PET film 26 having a thickness of 9.3 μm is mounted on the vapor deposition apparatus shown in FIG. 3, and the film 26 is run on a can roll 41.
The running speed was 20 m / min. Then, put 99.9% pure copper into the magnesium oxide crucible 42 and output 5 kW.
The electron gun 43 is activated by the
A copper underlayer having a thickness of 100 Å was formed on 26. (b) Magnetic Layer Next, the PET film 26 on which the copper underlayer is formed is mounted on the ion assisted oblique vapor deposition apparatus shown in FIG. 2, and the film 26 is run on the cooling plate 27. The running speed was 1 m / min. And the purity is 99.9 in the crucible 29 made of magnesium oxide.
Put about 5% of iron, operate electron gun 30 with output of 5kW to evaporate iron, deposit iron particles on PET film 26 (incident angle α = 70 °), and mix gas of nitrogen gas and oxygen gas. Kaufman type ion gun 31 (volume mixing ratio = 2: 1)
Then, the surface of the PET film 26 on which iron was deposited was irradiated with nitrogen ions and oxygen ions. As a result, a Fe-N-O based magnetic layer was formed. (c) Back coat layer and lubricating layer Next, a back coat formed by dispersing carbon black having an average particle size of 40 nm in a binder resin of urethane prepolymer and vinyl chloride resin on the surface of the PET film opposite to the magnetic layer surface. For paint by die coating method
A back coat layer was formed by coating so as to have a dry film thickness of 0.5 μm and drying. Then perfluoropolyether
(FOMBLIN Z DOL, manufactured by Montecatini Co.) was diluted and dispersed in a fluorine-based inert liquid (Fluorinert FC-77, manufactured by Sumitomo 3M Co., Ltd.) to a concentration of 0.05% by weight, and the coating was dried to obtain a dry film thickness. Of 20 Å on the magnetic layer and dried at 105 ° C to form a lubricating layer.

(2) Performance evaluation of magnetic recording medium The PET film having the underlayer, magnetic layer, lubricating layer and backcoat layer formed as described above was cut into a width of 8 mm and loaded into a high band 8 mm VCR cassette to obtain an 8 mm video. A cassette was manufactured. The output and C / N of the obtained 8 mm video cassette were measured by the following methods. The film forming rate was also evaluated. Table 1 shows the results. -Output and C / N characteristics Input the signal from the oscillator to the device that is a modified 8 mm VTR on the market and record from the recording head to the tape. Next, the recorded signal is reproduced and frequency analysis is performed using a spectrum analyzer. The recording frequency f output at this time f _out (dB _m )
Ratio to noise level No (dB _m ) at (f−1) MHz [f _out −No (d
B)] is C / N.

Example 2 The film forming conditions in Example 1 were changed, and the thickness of the underlayer was 40%.
An 8 mm cassette tape of 0 Å was manufactured and evaluated in the same manner as in Example 1. However, the traveling speed is different from that in the first embodiment.

Comparative Example 1 In Example 1, an 8 mm cassette tape was manufactured by forming a magnetic layer without forming an underlayer, and the same evaluation as in Example 1 was performed. However, the traveling speed is different from that in the first embodiment.

Comparative Example 2 The film forming conditions in Example 1 were changed, and the thickness of the underlayer was 30.
An 8 mm cassette tape of Å was manufactured and evaluated in the same manner as in Example 1. However, the traveling speed is different from that in the first embodiment.

Comparative Example 3 A loop was manufactured and evaluated in the same manner as in Example 1. However, the traveling speed is different from that in the first embodiment.

[0023]

[Table 1]

Note) * The output and C / N are based on Comparative Example 1 as a reference (0 dB). ** The film forming speed is a relative speed with 1 in Comparative Example 1.

[0025]

According to the present invention, the quality of a vapor deposition type magnetic recording medium having an iron-nitrogen based magnetic layer is improved, and it can be manufactured at a higher speed than in the conventional case.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the structure of a magnetic recording medium of the present invention.

FIG. 2 is a schematic view of an apparatus for manufacturing the magnetic recording medium of the present invention.

FIG. 3 is a schematic diagram of an apparatus for forming an underlayer of the magnetic recording medium of the present invention.

[Explanation of symbols]

 1 Support 2 Underlayer Containing Copper 3 Magnetic Layer Containing Iron and Nitrogen

 ─────────────────────────────────────────────────── ─── 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 (6)

[Claims] 1. A magnetic recording medium having an underlayer containing copper formed on a support and a magnetic layer containing iron and nitrogen formed on the underlayer. 2. The magnetic recording medium according to claim 1, wherein the magnetic layer is made of a Fe—N—O based compound. 3. The magnetic recording medium according to claim 1, wherein the magnetic layer is made of a Fe _x N-based compound. 4. The magnetic recording medium according to claim 1, wherein the underlayer is made of copper. 5. The magnetic recording medium according to claim 1, wherein the underlayer has a thickness of 50 to 500 Å. 6. A step of forming an underlayer containing copper on a support by a physical vapor deposition method in a vacuum atmosphere, and then forming a magnetic layer containing iron and nitrogen on the underlayer by an ion assisted physical vapor deposition method. A method of manufacturing a magnetic recording medium, comprising: