JPH1125440A - Magnetic record medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the magnetic record medium and its manufacture of which a superior electromagnetic conversion characteristic is obtained. SOLUTION: The medium is made by forming the magnetic layer, which is made of a ferromagnetic body metallic thin film, on a non-magnetic supporting body. Relating to the magnetic layer, which has a thickness (d), the amplitude of the oxidation degree distribution of the region excluding a surface side (1/5)d of the magnetic layer and a non-magnetic supporting body boundary side (1/5)d is set within 8%. The magnetic layer is formed by vapor depositing metallic magnetic particles on the running non-magnetic supporting body while introducing oxygen gas. In this process, an oxygen gas introducing port is arranged on the low injecting side of the vapor depositing region and an exhaust port is arranged on the high injecting side of the vapor depositing region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium in which a magnetic layer made of a ferromagnetic metal thin film is formed on a non-magnetic support, and a method for manufacturing the same.

[0002]

2. Description of the Related Art At present, as a magnetic recording medium corresponding to high-density recording, a ferromagnetic metal material such as a Co-Ni alloy, a Co-Cr alloy, or cobalt oxide is formed by a vacuum deposition method on a non-magnetic material such as a polyester film or a polyimide film. The so-called vapor deposition type magnetic recording medium directly attached on a support is becoming mainstream.

[0003] This vapor-deposited magnetic recording medium is excellent not only in coercive force and squareness ratio, but also in electromagnetic conversion characteristics at short wavelengths, and because the thickness of the magnetic layer can be made extremely thin, recording demagnetization is required. And the thickness loss during reproduction can be significantly reduced, and there is no need to mix an organic binder, which is a non-magnetic material, in the magnetic layer, so that the charge density of the magnetic material can be increased. ing. Recently, this vapor deposition type magnetic recording medium has been used as a high-band 8 mm video tape or a home digital video tape (D
V) has already been commercialized.

It is generally known that the electromagnetic conversion characteristics of a magnetic recording medium have a great relationship with the magnetic characteristics such as residual magnetic flux density, saturation magnetization and coercive force. In general, a technique of controlling magnetic properties by introducing oxygen gas to oxidize a part of the metal vapor to make it non-magnetic is used.

Various studies have been made on the method of introducing oxygen gas. However, at present, it is difficult to introduce oxygen from the vicinity of the minimum incident angle regulating mask of the vapor deposition apparatus and to set an optimal amount of oxygen to be introduced. Is considered to be the optimal method.

[0006] A commonly used vapor deposition apparatus is shown in FIG.
As shown in FIG. 3, a metal magnetic material 34 is filled in a vacuum chamber 32 evacuated from exhaust ports 31a and 31b provided on the head and bottom, respectively, and facing the cooling can 33. The crucible 35 is arranged.

The cooling can 33 includes a cooling device (not shown), and rotates at a constant speed in a clockwise direction in the figure. Then, the non-magnetic support 36 is fed out from the supply roll 37, moves along the peripheral surface of the cooling can 33, and is wound up by the take-up roll 38. The guide roller 3 is provided between the supply roll 37 and the cooling can 33.
9, a guide roller 40 is disposed between the cooling can 33 and the take-up roll 38, and the non-magnetic support 3
6 can smoothly travel between the supply roll 37, the cooling can 33, and the take-up roll 38 with a predetermined tension.

The crucible 35 is irradiated with an electron beam 42 from an electron gun 41 at an accelerated rate. The metal magnetic material 34 to which the electron beam 42 has been accelerated and irradiated is heated and evaporated, and adheres (deposits) on the non-magnetic support 36 traveling along the peripheral surface of the cooling can 33.

At this time, a mask 43 is disposed between the crucible 35 and the cooling can 33 so as to cover a predetermined area of the non-magnetic support 36 running at a constant speed on the peripheral surface of the cooling can 33. I have. Therefore, the metal magnetic particles enter the non-magnetic support 36 within a predetermined angle range, and the metal magnetic particles are oriented obliquely to the surface of the non-magnetic support 36 to form a magnetic layer.

Further, during such a vapor deposition, an oxygen gas is supplied to the surface of the non-magnetic support 36 through an oxygen gas inlet 44 provided in the vicinity of the vapor deposition region to control the magnetic properties.

[0011]

In a magnetic recording medium obtained by the above-described vapor deposition apparatus, the degree of oxidation in the thickness direction of the inside of the magnetic layer generally shows a distribution as shown in FIG.

In the oxidation degree distribution shown in FIG. 6, the internal oxidation degree of the magnetic layer increases as the oxygen gas introduction amount increases. Each internal oxidation degree has a peak on the magnetic layer surface side and the nonmagnetic support interface side, and in other regions, the oxidation degree tends to increase toward the nonmagnetic support interface side.

The peak is present on the magnetic layer surface side because oxygen gas is introduced from the low incidence side. It is considered that the reason why there is a peak on the nonmagnetic support interface side is that oxygen gas is generated from the nonmagnetic support. However, each peak in the case where no oxygen gas is introduced is considered to be naturally oxidized by the oxygen gas generated from the nonmagnetic support and the oxygen gas present in the vapor deposition apparatus.

However, the reason why the degree of oxidation increases in the region other than the peak on the surface side of the magnetic layer and the interface side of the non-magnetic support toward the interface side of the non-magnetic support was not clear.

Although the degree of internal oxidation of the magnetic layer has a large effect on magnetic properties, it is unknown and has not been investigated how the unevenness of the degree of oxidation of these magnetic layers affects the magnetic layer. Further, a vapor deposition method for making the degree of oxidation in the thickness direction of the magnetic layer uniform has not been studied.

The present invention has been made in view of such circumstances, and provides a magnetic recording medium that controls the oxidation degree distribution in the thickness direction of a magnetic layer and exhibits more excellent electromagnetic conversion characteristics, and a method of manufacturing the same. It is intended to do so.

[0017]

The present inventors have made intensive studies and as a result, the unreacted oxygen gas diffused and retained in the vapor deposition apparatus has a great effect on the internal oxidation degree distribution of the magnetic layer. It was found that the internal oxygen degree distribution could be made uniform by immediately exhausting the introduced oxygen gas from the exhaust port.

In the magnetic layer having a thickness d,
The surface side (1/5) d of the magnetic layer and the non-magnetic support side (1/5)
5) It has been found that excellent electromagnetic conversion characteristics can be obtained by suppressing the amplitude of the oxidation degree distribution in the region excluding d to within 8% and achieving uniform oxidation degree distribution.

That is, the magnetic recording medium according to the present invention comprises:
In a magnetic recording medium in which a magnetic layer made of a ferromagnetic metal thin film is formed on a non-magnetic support, the surface side (1/5) d of the magnetic layer having a thickness d and the non-magnetic support side (1/5)
It is characterized in that the amplitude of the oxidation degree distribution in the region excluding d is within 8%.

As described above, the magnetic recording medium in which the amplitude of the oxidation degree distribution inside the magnetic layer is suppressed to within 8% can exhibit excellent electromagnetic conversion characteristics. Further, by setting the maximum value of the degree of oxidation in the region of the magnetic layer on the nonmagnetic support interface side (1/5) d to 60 to 80%, the orientation of the magnetic layer is improved, and more excellent electromagnetic conversion is achieved. Characteristics can be exhibited.

On the other hand, the method of manufacturing a magnetic recording medium according to the present invention is characterized in that metal magnetic particles are deposited on a running non-magnetic support while introducing oxygen gas to form a magnetic layer. Arrange the oxygen gas inlet on the low incidence side,
An exhaust port is arranged on the high incidence side of the deposition region.

In the conventional vapor deposition method, an exhaust port is provided on a side wall surface of a vapor deposition apparatus or a part of a wall surface to which a shaft of a guide roll is attached in consideration of workability. here,
Most of the oxygen gas introduced from the oxygen gas inlet is
Immediately after being exposed to the vapor deposition particles, it reacts with the vapor deposition particles and adheres to the non-magnetic support, and the unreacted gas diffuses or stays in the vapor deposition device and is eventually taken into the exhaust port.

However, in the present invention, the oxygen gas inlet is disposed on the low incidence side of the vapor deposition region, and the exhaust port is disposed on the high incidence side of the vapor deposition region, so that the oxygen gas introduced from the oxygen gas inlet is supplied to the exhaust port. By immediately evacuating the magnetic layer, the degree of internal oxidation of the magnetic layer can be made uniform.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetic recording medium to which the present invention is applied and a method for manufacturing the same will be described in detail with reference to the drawings.

The magnetic recording medium to which the present invention is applied has a magnetic layer made of a ferromagnetic metal thin film formed on a non-magnetic support. As shown in FIG. 1, in a magnetic layer having a thickness d, a region excluding the surface side (1/5) d of the magnetic layer and the nonmagnetic support interface side (1/5) d (hereinafter referred to as an intermediate region). ) Is within 8%.

Here, the degree of oxidation is the oxygen content in the constituent atoms at each point in the thickness direction of the magnetic layer, and the ferromagnetic metal M (for example, cobalt, iron, nickel,
O / M [atomic%] when a magnetic thin film having a composition of chromium or the like is used. The degree of oxidation inside the magnetic layer is
It may be measured by Auger electron spectroscopy. Auger electron spectroscopy irradiates a sample with an electron beam and detects Auger electrons emitted from the sample surface. Auger electrons have energy peculiar to the type of element on the solid surface, so that elemental analysis can be performed by measuring this energy.

The amplitude is the difference between the maximum degree of oxidation x ₁ and the minimum degree of oxidation x ₂ excluding the noise component in the intermediate region of the magnetic layer.

As described above, the magnetic recording medium in which the amplitude of the oxidation degree distribution in the middle region of the magnetic layer is suppressed to within 8% exhibits excellent electromagnetic conversion characteristics because the magnetic characteristics of the magnetic layer are uniform. be able to. If the amplitude of the oxidation degree distribution exceeds 8%, the magnetic characteristics inside the magnetic layer become non-uniform and the reproduction output decreases.

Oxidation of the magnetic layer at the nonmagnetic support interface side improves the orientation of the magnetic layer. Therefore, the maximum oxidation degree in the region of the magnetic layer at the nonmagnetic support interface side (1/5) d is improved. Is preferably 60 to 80%.

By the way, in order to suppress the amplitude of the oxidation degree distribution in the intermediate region of the magnetic layer to within 8%,
It is preferable to arrange an oxygen gas inlet on the low incidence side of the deposition region and an exhaust port on the high incidence side of the deposition region. Here, in the deposition region, one closer to the deposition source is defined as a low incidence side, and the other far from the deposition source is defined as a higher incidence side.

Specifically, it is preferable to form a magnetic layer on a non-magnetic support by the vapor deposition apparatus shown in FIG.

In this vapor deposition apparatus, a metal magnetic material 4 was filled in a vacuum chamber 2 in which the inside was evacuated by a first vacuum pump 1, which was opposed to a cooling can 3. The crucible 5 is arranged.

The cooling can 3 rotates at a constant speed in the clockwise direction in the figure and includes a cooling device (not shown) therein so that deformation of the nonmagnetic support 6 due to a rise in temperature can be suppressed. I have. Then, the nonmagnetic support 6 is fed out from the supply roll 7, moves along the peripheral surface of the cooling can 3, and is taken up by the take-up roll 8.
A guide roller 9 is disposed between the supply roll 7 and the cooling can 3, and the cooling can 3 and the take-up roll 8
Between them, a guide roller 10 is arranged so that the nonmagnetic support 6 can smoothly travel between the supply roll 7, the cooling can 3, and the winding roll 8 with a predetermined tension. The feed roll 3, the take-up roll 4, and the cooling can 6 each have a cylindrical shape having a length substantially equal to the width of the nonmagnetic support 5.

The crucible 5 is moved from an electron gun 11 attached to the side wall of the vacuum chamber to an electron beam 12.
Are accelerated. The metal magnetic material 4 to which the electron beam 12 has been accelerated and irradiated is heated and evaporated, and adheres (deposits) as a magnetic layer on the nonmagnetic support 6 running along the peripheral surface of the cooling can 3.

A mask 13 is provided between the cooling can 3 and the crucible 5 and in the vicinity of the cooling can 3. The mask 13 is formed so as to cover a predetermined area of the non-magnetic support 6 running at a constant speed on the peripheral surface of the cooling can 3, and the heated and evaporated metal magnetic material 4 is applied to the non-magnetic support 6. Vapor deposition is performed obliquely within a predetermined angle range (θ _{1 to} θ ₂ ).

Further, at the time of such vapor deposition, an oxygen gas inlet 14 is arranged on the low incidence side of the vapor deposition region. The oxygen gas inlet 14 partially oxidizes the metal magnetic particles evaporated from the crucible and oxidizes the surface of the nonmagnetic support 6. In addition,
The oxygen gas inlet 14 is preferably arranged between the cooling can 3 and the mask 13 in order to prevent direct exposure to the vapor of the metal magnetic particles. When the oxygen gas inlet 14 is directly exposed to the vapor of the metal magnetic particles, the vapor of the metal magnetic particles adheres to the oxygen gas inlet 14, and the introduction of the oxygen gas is hindered.

On the other hand, on the high incidence side of the deposition region, an exhaust port 1 is provided.
5 are arranged. The exhaust port 15 is provided with a second vacuum pump 16
And the amount of exhaust gas can be adjusted by the conductance valve 17. Thereby, the exhaust port 15 serves to exhaust the oxygen gas introduced from the oxygen gas inlet 14.

In the vapor deposition apparatus configured as described above, the oxygen gas introduced from the low incidence side of the deposition area is immediately exhausted from the exhaust port 15 arranged on the high incidence side, and the unreacted oxygen gas is removed by vacuum. There is no diffusion or stagnation in the chamber 1. Therefore, the degree of internal oxidation in the intermediate region of the magnetic layer is made uniform, and the amplitude of the degree of internal oxidation can be suppressed to within 8%.

The second vacuum pump 16 may be used also as the first vacuum pump 1 for evacuating the vacuum chamber 1.

Incidentally, conventionally known metal magnetic materials can be used as these metal magnetic materials. For example, C
o-Ni alloy, Co-Pt alloy, Co-Ni-Pt
Alloy, Fe-Co alloy, Fe-Co-Ni alloy,
Fe-Co-B-based alloy, Fe-Co-Ni-B-based alloy,
Co-Cu alloy, Fe-Cu alloy, Co-Au alloy, Mn-Bi alloy, Mn-Au alloy, Fe-Cr
Alloy, Ni-Cr alloy, Fe-Co-Cr alloy,
Co-Ni-Cr alloys and the like can be mentioned.

The material of the non-magnetic support is as follows:
Conventionally known polymer materials can be used. For example, polyethylene terephthalate, polyethylene-2,
Polyesters such as 6-naphthalate and the like, polyolefins such as aromatic polyamide, polyethylene and polypropylene, cellulose derivatives such as nitrocellulose, cellulose triacetate, cellulose diacetate and cellulose triacetate butyrate, and vinyl compounds such as polyvinyl chloride and polyvinylidene chloride Polymer materials such as resins, polycarbonates, and polyimides are exemplified.

The configuration of the magnetic recording medium according to the present invention is not limited to the above-described two layers of the non-magnetic support and the magnetic layer. An underlayer or an intermediate layer may be provided for improving the adhesion of the film and controlling the coercive force.

A back coat layer may be provided on the side of the non-magnetic support opposite to the surface on which the magnetic layer is formed, for the purpose of improving running properties and enhancing durability. For the back coat layer, a conventionally known material can be used.For example, a non-magnetic pigment such as carbon or calcium carbonate dispersed in a binder such as polyurethane or vinyl chloride-vinyl acetate copolymer is used. Can be.

Further, a hard carbon film may be provided on the surface of the magnetic layer made of the metal magnetic thin film for the purpose of improving the durability and weather resistance of the magnetic recording medium. The hard carbon film is formed by a sputtering method, a chemical vapor deposition (CVD) method, or the like. Further, by allowing the lubricant to be present, it is possible to enhance the running property based on the shape of the particulate protrusions of the magnetic material.

The surface of the magnetic recording medium, the back surface thereof, the vicinity thereof, the inside of the magnetic layer (the gap in the ferromagnetic metal thin film), the interface between the non-magnetic support and the magnetic layer, the non-magnetic support, and the like. Various additives such as a rust preventive and an antistatic agent may be present as required by the above-mentioned means.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on experimental results.

Example 1 First, a metal magnetic thin film made of cobalt was deposited on a nonmagnetic support 6 made of polyethylene terephthalate having a thickness of 6 μm and a width of 500 mm by using the above-described vapor deposition apparatus shown in FIG. A film was formed at 150 nm. Here, the deposition conditions are as follows: the incident angle is 45 ° to 90 °, and the nonmagnetic support 6
Is set to 50 m / min, the opening of the conductance valve 17 is set to 5 degrees, and the oxygen introduction amount is set to 1600 cc / min.

Next, a backcoat paint mainly composed of carbon was applied to the surface of the nonmagnetic support 6 opposite to the surface on which the metal magnetic thin film was formed, to form a backcoat layer, followed by heat treatment. Then, a rust preventive and a lubricant were applied onto the metal magnetic thin film, respectively, and then cut into a width of 8 mm to form a magnetic tape, which was incorporated into a cassette.

Examples 2 to 6 As shown in Table 1, except that the opening degree of the conductance valve 17 was changed from 10 degrees to 90 degrees (fully opened) to change the exhaust amount and the oxygen introduction amount. Similarly, a magnetic tape was produced.

Here, the oxygen gas introduction amount is obtained in advance by an experiment, and is the oxygen gas introduction amount when the reproduction output is maximized. The reason why the oxygen gas introduction amount is changed is that the optimum oxygen introduction amount may differ depending on the internal oxidation degree distribution, so that it is not possible to discuss the superiority of the oxidation degree distribution with a constant introduction amount.

COMPARATIVE EXAMPLE 1 As a comparative example, the opening degree of the conductance valve 17 was set to 0 degree, the amount of exhaust gas exhausted from the exhaust port 15 was reduced, and vapor deposition corresponding to a conventional vapor deposition method was performed. Except for this, a magnetic tape was produced in the same manner as in Example 1.

Evaluation of Characteristics The magnetic tapes produced in the Examples and Comparative Examples were examined for the internal oxidation degree distribution, magnetic characteristics and electromagnetic conversion characteristics of the magnetic layer. The results are shown in FIG.

[0053]

[Table 1]

The internal oxidation degree of the magnetic layer was measured using an Auger electron spectrometer (manufactured by JEOL; JAMP-3).
0) was used.

As shown in FIG. 4, the Auger electron spectrometer has an analysis chamber 21 and a sample exchange chamber 22 arranged adjacent to the analysis chamber 21 for exchanging a sample. In the analysis room 21, a titanium getter pump 23,
Analysis room ion pump 2 consisting of baking heater 24
5 during analysis, the inside of the analysis chamber 21 is 10 ⁻⁸ to 1
An ultra-high vacuum of 0 ^-7 Pa is set.

A sample holder 20 on which a sample to be measured is fixed is installed in the analysis chamber 21. The sample stage 26 is rotated in the X and Y directions in a horizontal plane and around the Z axis perpendicular to the X and Y directions. It can be moved in the direction and the tilt direction in which the sample surface is tilted. In the analysis chamber 21, an electron gun 27 for generating an electron beam for Auger electron excitation, a secondary electron detector 28 for detecting a signal emitted from the sample, an Auger electron detector 29, and for sputtering the sample. The ion gun 30 is introduced and the Auger electrons are detected in the depth direction while sputtering the surface of the sample with Ar gas to obtain a spectrum in the depth direction.

The magnetic properties were measured in a longitudinal direction and an in-plane direction of the medium using a sample vibration type measuring device (VSMP-1S, manufactured by Toei Kogyo Co., Ltd.).

The electromagnetic conversion characteristics were obtained by modifying a high-band 8 mm video deck (manufactured by Sony Corporation; EV-S900), the relative speed of the magnetic recording medium was 3.8 m / sec, the recording frequency was 7 MHz, and the recording wavelength was 0.54 μm. The reproduction output was measured under the following conditions.

From the results shown in FIG. 3, it can be seen that in the embodiment in which the exhaust port is provided on the high incidence side of the vapor deposition region, the degree of oxidation on the nonmagnetic support interface side in the intermediate region is small and uniform. That is, the amplitude of the oxidation degree distribution in the intermediate region is suppressed to within 8%. Also, it can be seen that the larger the displacement, the smaller the degree of oxidation on the non-magnetic support side.

On the other hand, in the comparative example corresponding to the conventional vapor deposition method, the degree of oxidation on the nonmagnetic support interface side in the intermediate region tends to be large and non-uniform.

Further, from the results in Table 1, as described above, in the embodiment in which the amplitude of the oxidation degree distribution in the intermediate region was suppressed to within 8%, a higher reproduction output was obtained as compared with the comparative example. You can see that. In particular, in the examples in which the degree of oxidation on the surface side of the nonmagnetic support is 60% or more, it is considered that there is an effect of improving the coercive force, and particularly excellent electromagnetic conversion characteristics are obtained.

As described above, by arranging the oxygen inlet on the low incidence side and the exhaust port on the high incidence side of the deposition region, the amplitude of the oxidation degree distribution in the middle region of the magnetic layer is suppressed to within 8%. We can see that we can do it. In addition, it can be seen that excellent electromagnetic conversion characteristics can be obtained by making the oxidation degree distribution in the intermediate region uniform.

[0063]

As is clear from the above description, the magnetic recording medium according to the present invention has a magnetic layer having a thickness d of the magnetic layer surface side (1/5) d and the nonmagnetic support interface side (1/5). / 5)
Since the amplitude of the oxidation degree distribution in the region excluding d is suppressed to within 8%, excellent electromagnetic conversion characteristics can be obtained. Further, in the method for manufacturing a magnetic recording medium according to the present invention, since the oxygen gas inlet is disposed on the low incident side and the exhaust port is disposed on the high incident side, the oxidation degree distribution inside the magnetic layer is controlled. be able to.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing the relationship between the depth of a magnetic layer and the degree of internal oxidation in a magnetic recording medium to which the present invention is applied.

FIG. 2 is a schematic diagram showing a configuration of a vapor deposition apparatus to which the present invention is applied.

FIG. 3 is a characteristic diagram showing the relationship between the depth of a magnetic layer and the degree of internal oxidation in the magnetic tapes obtained in Examples and Comparative Examples.

FIG. 4 is a schematic diagram showing a configuration of an Auger electron spectrometer.

FIG. 5 is a schematic diagram showing a configuration of a conventional vapor deposition apparatus.

FIG. 6 is a characteristic diagram showing the relationship between the depth of a magnetic layer and the degree of internal oxidation in a magnetic layer formed by a conventional vapor deposition apparatus.

[Explanation of symbols]

1 first vacuum pump, 2 vacuum chamber, 3 cooling can,
4 Metal magnetic material, 5 crucible, 6 Non-magnetic support, 7
Feed roll, 8 take-up roll, 9, 10 guide roll, 11 electron gun, 12 electron beam, 13 mask, 14
Oxygen gas inlet, 15 exhaust port, 16 second vacuum pump, 17 conductance valve

Continued on the front page (72) Inventor Yasuyo Kumichi 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Tsutomu Takeda 6-35-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation In company

Claims (3)

[Claims] 1. A magnetic recording medium comprising a magnetic layer comprising a ferromagnetic metal thin film formed on a non-magnetic support, wherein the magnetic layer having a thickness of d is equal to (1/5) d of the surface of the magnetic layer.
And a region other than the interface (1/5) d of the non-magnetic support, wherein the amplitude of the oxidation degree distribution is within 8%. 2. A method according to claim 1, wherein the magnetic layer is on the nonmagnetic support interface side (1/1 /
5) The magnetic recording medium according to claim 1, wherein the maximum value of the degree of oxidation in the region d is 60 to 80%. 3. When a magnetic layer is formed by vapor deposition of metal magnetic particles while introducing oxygen gas into a running non-magnetic support, an oxygen gas inlet is disposed on the low incidence side of the vapor deposition region. A method for manufacturing a magnetic recording medium, comprising arranging an exhaust port on a high incidence side of a deposition region.