JPH0916948A - Magnetic recording medium and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [Structure] In a magnetic recording medium obtained by forming at least a metal magnetic thin film and a carbon film on one main surface of a non-magnetic support and cutting it into a predetermined size, carbon is also used for the cut surface. Form a film. Further, a coating film of a rust preventive agent is preferably formed on the surface of these carbon films. [Effect] Since the exposed portion of the metal magnetic thin film is eliminated, corrosion is suppressed even in an environment of high temperature and high humidity, and the magnetic recording medium has excellent storage characteristics. Therefore, even if it is stored for a long period of time, deterioration of the magnetic characteristics is prevented and the reliability is high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called metal thin film type magnetic recording medium in which a metal magnetic thin film and a carbon film are formed on a non-magnetic support.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a powder magnetic material such as an oxide magnetic powder or an alloy magnetic powder is coated on a non-magnetic support with a vinyl chloride-vinyl acetate copolymer, polyester resin, urethane resin, A so-called coating type magnetic recording medium, which is prepared by coating and drying a magnetic coating material dispersed in an organic binder such as a polyurethane resin, is widely used.

On the other hand, with the increasing demand for high-density recording, Co--Ni alloys, Co--Cr alloys, Co--
A so-called metal magnetic thin film type magnetic recording medium in which a metal magnetic material such as O is directly deposited on a non-magnetic support by plating or vacuum thin film forming means (vacuum deposition method, sputtering method, ion plating method, etc.) It has been proposed and attracts attention.

This metal magnetic thin film type magnetic recording medium is excellent not only in coercive force and squareness ratio but also in electromagnetic conversion characteristics at short wavelengths, and the magnetic layer can be extremely thin,
There are many advantages such as remarkably small thickness loss during recording demagnetization and reproduction, and higher packing density of the magnetic material because there is no need to mix the binder, which is a non-magnetic material, into the magnetic layer. Have

Further, in order to improve the electromagnetic conversion characteristics of this kind of magnetic recording medium and to obtain a larger output, the magnetic layer is obliquely vapor-deposited when forming the magnetic layer of the magnetic recording medium. The so-called oblique vapor deposition has been proposed and put to practical use.

By the way, it is said that the magnetic recording medium as described above has problems in durability and rust resistance, and in order to solve these problems, the surface of the magnetic layer is oxidized or vacuum film formation is performed. Method, a protective film is provided on the metal magnetic thin film, and a lubricant is further applied thereon.

At present, as this type of protective film,
A carbon film formed by a sputtering method and a diamond-like carbon film formed by a chemical vapor deposition (CVD) method using a hydrocarbon-based gas are considered promising.

[0008]

However, when the carbon film is formed as described above and then cut into a predetermined size, the metal magnetic thin film is exposed at the cut surface. When such a magnetic recording medium is used for a long time in a high temperature and high humidity environment, or is stored for a long time, corrosion may progress from the cut surface of the metal magnetic thin film. Become.

Therefore, the present invention has been proposed in view of the above-mentioned conventional circumstances, and magnetic recording is excellent in storage characteristics, in which corrosion is suppressed even when used or stored in an environment of high temperature and high humidity. The purpose is to provide a medium. Moreover, it aims at providing the manufacturing method of such a magnetic recording medium.

[0010]

A magnetic recording medium according to the present invention has been proposed in order to achieve the above-mentioned object, and at least a metal magnetic thin film and a carbon film are provided on one main surface of a non-magnetic support. It is formed and cut into a predetermined size, and a carbon film is also formed on this cut surface.

Here, in order to further obtain the effect of suppressing corrosion, it is preferable to have a structure in which a coating film of a rust preventive agent is formed on the surface of the carbon film.

In order to manufacture a magnetic recording medium having such a structure, at least a metal magnetic thin film and a carbon film are formed on one main surface of a non-magnetic support, and this is cut into a predetermined size. After passing through the steps, a step of depositing a carbon film on the cut surface may be performed.

Further, a step of applying a rust preventive agent on the surface of the carbon film may be added during the manufacturing process. In the step of applying the rust preventive agent, the rust preventive agent coating film can be formed not only on the carbon film on the main surface but also on the surface of the carbon film on the cut surface, after the cutting step. However, even if the rust preventive agent is applied before the cutting step, the rust preventive agent also wraps around the cut surface to some extent after that.

Here, the carbon film may be a carbon film formed by a sputtering method or a carbon film formed by a CVD method using a hydrocarbon gas. The sputtering method includes a magnetron sputtering method and a facing target method,
As the CVD method, CVD is plasma CVD method, EC
R plasma CVD method, arc jet plasma CVD method and the like can be mentioned. Alternatively, the carbon film may be formed by applying a vacuum vapor deposition method, an ion plating method, or the like.

However, when forming a carbon film on a metal magnetic thin film, the nonmagnetic support on which the metal magnetic thin film is formed is continuously formed while running, and the carbon film is formed on the side surface formed by cutting. When depositing a film, place a roll of the magnetic recording medium that has been cut at a predetermined position,
The film may be formed all at once on the side surface of the roll.

In the magnetic recording medium according to the present invention, the constituent materials such as the non-magnetic support and the metal magnetic thin film are not particularly limited, and any conventionally known one can be used.

For example, as the non-magnetic support, polyesters, polyolefins, celluloses, vinyls,
Polymer substrates formed of polymer materials typified by polyimides and polycarbonates, metal substrates made of aluminum alloys and titanium alloys, ceramics substrates such as aluminum glass, glass substrates, and the like can be given. Although not limited in any way, when applied to a magnetic tape, a polyethylene terephthalate film, a polyethylene naphthalate film, an aramid film or the like is preferably used. In addition, a filler may be internally added to these films to control the surface roughness,
A layer for controlling the surface roughness may be formed on the surface.

As the metal magnetic thin film, any conventionally known one can be used. For example, Fe, C
Ferromagnetic metals such as o and Ni, Fe-Co, Fe-Ni,
Co-Ni, Fe-Co-Ni, Fe-Co-B, Fe
-Ni-B, Fe-Cu, Co-Cu, Co-Au, C
o-Pt, Mn-Bi, Mn-Al, Fe-Cr, Co
-Cr, Ni-Cr, Fe-Co-Cr, Co-Ni-
Cr, Co-Ni-Pt, Fe-Co-Ni-Cr, F
A metal magnetic thin film for in-plane magnetization recording made of a ferromagnetic alloy such as e-Co-Ni-B, a Co-Cr alloy thin film, Co-
A metal magnetic thin film for perpendicular magnetization recording such as an O-based thin film may be used.

These metal magnetic materials include a vacuum vapor deposition method of evaporating a ferromagnetic metal magnetic material under vacuum to deposit it on a support, an ion plating method of evaporating a ferromagnetic metal material in a discharge, and argon. A thin film is formed by a so-called PVD technique such as a sputtering method in which atoms on the target surface are knocked out by argon ions generated through a glow discharge in an atmosphere containing the main component. The magnetic layer may be either a single-layer film or a multilayer film of a metal magnetic thin film formed by these methods. In order to improve the adhesive force between layers and control the coercive force between the non-magnetic support and the metal magnetic thin film, or between the metal magnetic thin films when the metal magnetic thin film is a multilayer film. A base layer or an intermediate layer may be provided. Further, the vicinity of the surface of these metal magnetic thin films may be an oxide layer for the purpose of improving corrosion resistance and the like.

Particularly in the case of a metal magnetic thin film for in-plane magnetization recording, Bi, Sb, Pb, Sn and G are previously formed on a non-magnetic support.
A base film of a low melting point non-magnetic material such as a, In, Ge, Si, Ti is formed in advance, and a metallic magnetic material is vapor-deposited or sputtered from the vertical direction to diffuse the low melting point non-magnetic material into the metallic magnetic thin film. However, the orientation may be eliminated to secure the in-plane isotropy and improve the coercive force.

Further, in the magnetic recording medium according to the present invention, a back coat layer is formed on the surface of the non-magnetic support opposite to the side on which the metal magnetic thin film is formed, or the carbon film is further lubricated. A top coat layer made of an agent, an anticorrosive agent, or the like may be applied. As a material used for these layers, any conventionally known material can be used.
For example, the back coat layer is a non-magnetic layer in which a non-magnetic powder having an antistatic effect and a friction reducing effect, such as carbon black formed in a normal magnetic recording medium, is dispersed in a binder. Good.

[0022]

When the carbon film is formed not only on the main surface of the metal magnetic thin film but also on the cut surface, the exposed portion of the metal magnetic thin film disappears, so that the corrosion is suppressed even in an environment of high temperature and high humidity. Therefore, the magnetic recording medium according to the present invention has excellent storage characteristics.

[0023]

EXAMPLES Specific examples to which the present invention is applied will be described below, but it goes without saying that the present invention is not limited to these examples.

Example 1 The magnetic tape of this example is one in which a metal magnetic thin film and a carbon film are formed on one main surface of a non-magnetic support, and a carbon film is also formed on the cut surface.

Specifically, this magnetic tape has a thickness of 7 μm.
m of polyethylene terephthalate (PET) film on one main surface of the non-magnetic support having a thickness of 200 nm of C
o A metal magnetic thin film made of a thin film is formed, and an amorphous carbon film called diamond-like carbon is further formed thereon with a film thickness of about 1/20 (about 10 nm) of the metal magnetic thin film. Become.

The surface of the non-magnetic support has a particle size of about 6
The protrusions composed of 0 nm SiO ₂ particles are formed at a density of 10,000 / mm ² , and the metal magnetic thin film is composed of two thin films having the same crystal growth direction.

On the surface of this carbon film, a top coat layer composed of a coating film of a fluorine-based lubricant and a coating film of a rust preventive was formed, and a metal magnetic thin film on a non-magnetic support was formed. A back coat layer mainly composed of carbon black and a binder is formed on the main surface opposite to the main surface.

The magnetic tape is cut to a width of 8 mm, and an amorphous carbon film called diamond-like carbon is also formed on the cut surface. Here, this magnetic tape is the sample tape of the first embodiment.

In order to manufacture such a sample tape, first, a non-magnetic support having the above-mentioned structure is prepared, and while the non-magnetic support is run in a vacuum vapor deposition apparatus, a main component of the non-magnetic support is prepared. A metal magnetic thin film was continuously formed on the surface by performing oblique vapor deposition using Co as a vapor deposition source.

Thereafter, while the non-magnetic support on which the metal magnetic thin film is thus formed is run in the sputtering apparatus, sputtering using carbon as a target is performed to form a carbon film on the metal magnetic thin film. Were continuously deposited.

Subsequently, a back coat paint having the following composition was applied to the main surface of the non-magnetic support opposite to the main surface on which the metal magnetic thin film and the carbon film were formed.

Composition of coating for back coat Carbon black (trade name: Asahi # 80) 100 parts by weight Polyester-polyurethane copolymer 100 parts by weight Methyl ethyl ketone 500 parts by weight Toluene 500 parts by weight After applying the above coating for back coat After drying, a back coat layer having a thickness of 0.5 μm was obtained.

On the above-mentioned carbon film, a fluorine-based lubricant dissolved in toluene and a rust preventive dissolved in ethanol were applied at a coating amount of 10 mg / m ² , respectively, A coat layer was formed.

Thereafter, this was cut into a width of 8 mm and wound to form a roll of magnetic tape, and then a carbon film was formed on the cut surface.

As shown in FIG. 1, the sputtering apparatus used for forming the carbon film has a cathode chamber 4 and an anode electrode 5 in a vacuum chamber 1 provided with a gas inlet 2 and an exhaust port 3. Are arranged so as to face each other, a target 6 is arranged on the cathode electrode 4, and a magnet 7 for forming a magnetic field is arranged on the back side thereof, which is a so-called DC magnetron sputtering apparatus. Here, the roll 8 described above can be placed on the surface of the anode electrode 5 facing the target 6. Here, the roll 8 is placed so that the width direction of the magnetic tape is perpendicular to the upper surface of the target 6, that is, one cutting surface of the magnetic tape faces the target 6. The conditions for forming the carbon film are as follows.

Film-forming conditions Device: DC magnetron sputtering device Target described above: Carbon (thickness 6 mm) Sputtering gas: Ar Vacuum degree during film formation: 8 × 10 ⁻¹ Pa Set film thickness: 5-10 nm Note that the predetermined film formation After finishing, roll 8 upside down,
The magnetic tape was placed on the anode electrode 5 so that the other cut surface of the magnetic tape faces the target 6, and a carbon film was similarly formed.

Then, after forming a carbon film on both cut surfaces of the magnetic tape as described above, the carbon tape was incorporated into a cassette to complete the sample tape of Example 1.

Example 2 The magnetic tape according to this example has the same structure as the sample tape of Example 1 except that the coating film of the rust preventive agent is not formed on the carbon film. In addition, this magnetic tape, except that the step of applying the rust preventive agent is omitted,
It was produced in the same manner as in Example 1. This magnetic tape is used as the sample tape of Example 2.

Comparative Example 1 The magnetic tape according to this comparative example has the same structure as the sample tape of Example 1 except that the carbon film is not formed on the cut surface. This magnetic tape was manufactured in the same manner as in Example 1 except that the step of forming a carbon film on the cut surface was omitted. This magnetic tape is used as a sample tape of Comparative Example 1.

Comparative Example 2 The magnetic tape according to this Comparative Example is the same as the sample tape of Example 1 except that the coating film of the rust preventive agent is not formed and the carbon film is not formed on the cut surface. It has a structure of. This magnetic tape was produced in the same manner as in Example 1 except that the step of applying a rust preventive agent and the step of forming a carbon film on the cut surface were omitted.
This magnetic tape is used as a sample tape of Comparative Example 2.

Comparative Example 3 The magnetic tape according to this comparative example has the same structure as the sample tape of Example 1 except that the carbon film is not formed on the metal magnetic thin film. This magnetic tape was produced in the same manner as in Example 1 except that the step of forming a carbon film on the metal magnetic thin film was omitted. This magnetic tape is used as a sample tape of Comparative Example 3.

Comparative Example 4 The magnetic tape according to this Comparative Example is a sample tape of Example 1 except that the carbon film is not formed on the metal magnetic thin film and the rust preventive coating film is not formed. It has the same configuration as the above. In addition, this magnetic tape,
It was produced in the same manner as in Example 1 except that the step of forming a carbon film on the metal magnetic thin film and the step of applying a rust preventive agent were omitted. This magnetic tape is used as a sample tape of Comparative Example 4.

Comparative Example 5 The magnetic tape according to this comparative example was the same as the sample tape of Example 1 except that the carbon film was not formed on the metal magnetic thin film and the carbon film was not formed on the cut surface. It has a similar configuration. This magnetic tape was manufactured in the same manner as in Example 1 except that the step of forming a carbon film on the metal magnetic thin film and the step of forming a carbon film on the cut surface were omitted. This magnetic tape is used as a sample tape of Comparative Example 5.

Comparative Example 6 In the magnetic tape according to this comparative example, the carbon film was not formed on the metal magnetic thin film, the carbon film was not formed on the cut surface, and the coating film of the rust preventive agent was formed. It has the same structure as the sample tape of Example 1 except that it is not provided. This magnetic tape was manufactured in the same manner as in Example except that the steps of forming a carbon film on the metal magnetic thin film, applying the rust preventive agent, and forming the carbon film on the cut surface were omitted. It was produced in the same manner as 1. This magnetic tape is used as a sample tape of Comparative Example 6.

[0045] Example 1 having the evaluation above-described structure characteristics, Example 2, was evaluated for storage characteristics of the sample tapes of Comparative Examples 1 to 6.

Specifically, each sample tape was placed in a constant temperature bath A having a temperature of 40 ° C. and a relative humidity of 80% RH.
3 in a constant temperature bath B with a temperature of 65 ° C and a relative humidity of 90% RH
Store for 0 days, 1 day, 5 days, 10 days, 20 days,
After 30 days, the presence or absence of corrosion was observed.

The constitutional conditions of each sample tape are summarized in Table 1, the observation results for each sample tape stored in the constant temperature bath A are shown in Table 2, and the observation results for each sample tape stored in the constant temperature bath B are shown. Is shown in Table 3.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

From Tables 2 and 3, the sample tape of Example 1 having the carbon film on the metal magnetic thin film and the cut surface and also having the coating film of the rust preventive agent was used under high temperature and high humidity environment. It can be seen that corrosion does not occur even if stored for more than a day. Even if the coating film of the rust preventive agent was not formed, the sample tape of Example 2 in which the carbon film was formed on the metal magnetic thin film and the cut surface was stored for 20 days or more under the environment of high temperature and high humidity. It turns out that it can endure.

Further, the sample tape of Example 1 and the sample tape of Comparative Example 1 are compared, or Example 2 is used.
Comparing the sample tape of No. 1 with the sample tape of Comparative Example 2, it is found that the sample tapes have the same constitution except that the carbon film on the cut surface is different, but there is a difference in the occurrence state of corrosion due to storage. . From this, it is understood that the formation of the carbon film on the cut surface makes the sample tape less likely to corrode and improves the storage characteristics.

However, the sample tape of Comparative Example 3 is compared with the sample tape of Comparative Example 5, or Comparative Example 4
When the sample tape of No. 1 and the sample tape of Comparative Example 6 are compared, there is no difference in the occurrence state of corrosion, although the presence or absence of the carbon film on the cut surface is different. From this, it is understood that the carbon film must be formed on the metal magnetic thin film in order to obtain the effect of suppressing corrosion by forming the carbon film on the cut surface.

[0054]

As is apparent from the above description, when the present invention is applied and the carbon film is formed not only on the main surface of the metal magnetic thin film but also on the cut surface, the exposed portion of the metal magnetic thin film is exposed. Since it disappears, corrosion is suppressed even in a high temperature and high humidity environment, and the magnetic recording medium has excellent storage characteristics.

Therefore, the magnetic recording medium according to the present invention is highly reliable in that deterioration of magnetic characteristics is prevented even if it is stored for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a DC magnetron sputtering apparatus used in the present invention.

[Explanation of symbols]

 1 Vacuum chamber 4 Cathode electrode 5 Anode electrode 6 Target 8 Roll

Claims (4)

[Claims] 1. A magnetic recording medium in which at least a metal magnetic thin film and a carbon film are formed on one main surface of a non-magnetic support, and the magnetic recording medium is cut to a predetermined size, and the carbon film is formed on the cut surface. A magnetic recording medium characterized by: 2. The magnetic recording medium according to claim 1, wherein a coating film of a rust preventive agent is formed on the surface of the carbon film. 3. After the step of forming at least a metal magnetic thin film and a carbon film on one main surface of the non-magnetic support and the step of cutting this into a predetermined size, the carbon is cut onto the cut surface. A step of depositing a film, the method for manufacturing a magnetic recording medium. 4. The method of manufacturing a magnetic recording medium according to claim 2, further comprising a step of applying a rust preventive agent on the surface of the carbon film.