JPH0765346A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance recording and reproducing characteristics and corrosion resistance by disposing two metallic magnetic films each contg. a specified metal as the principal component. CONSTITUTION:An undercoat layer 2, a 1st metallic magnetic film 3 based on Co or Fe and a 2nd metallic magnetic film 4 contg. Ni are successively laminated on a substrate 1 with a back coat layer 6 and an oxide film 4a as an insulating film and a lubricant layer 5 are further laminated to obtain the objective magnetic recording medium. Since the magnetic film 4 having a high coercive force and excellent in corrosion resistance is laminated on the magnetic film 3 having a high saturation magnetic flux density, the magnetic recording medium has enhanced recording and reproducing characteristics and corrosion resistance.

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.

[0002]

BACKGROUND OF THE INVENTION In a magnetic recording medium such as a magnetic tape, due to a demand for high density recording, a binder resin is not used as a magnetic layer provided on a non-magnetic support, instead of a coating type using a binder resin. It is well known that a metal thin film type that is not used has been proposed.

That is, there has been proposed a magnetic recording medium having a magnetic layer formed by a wet plating means such as electroless plating, or a dry plating means such as vacuum deposition, sputtering or ion plating. Since the magnetic recording medium of this type has a high packing density of magnetic material, it is suitable for high-density recording. Incidentally, for example, Co is used as the magnetic material forming the magnetic layer in the metal thin film type magnetic recording medium of this type.

However, since Co is inferior in corrosion resistance, it has been proposed to use Co--Ni alloy instead of Co. Since this Co—Ni alloy has better corrosion resistance than Co, it is currently becoming mainstream to use Co—Ni alloy rather than Co as a material for forming the metal magnetic film.

[0005]

DISCLOSURE OF THE INVENTION Although it is recognized that a Co—Ni alloy has better corrosion resistance than Co, what is important as a magnetic recording medium is that it has excellent recording / reproducing characteristics. From this point of view, the magnetic recording medium in which the metal magnetic film is made of a Co—Ni alloy is by no means sufficient. Incidentally, a magnetic recording medium having a metal magnetic film made of Co and Co
Comparing the reproduction output (7 MHz) with a magnetic recording medium having a metal magnetic film made of a -Ni (80% -20%) alloy,
There is a difference of 5.2 dB, which is Co-N rather than Co.
i-alloy is by no means superior.

That is, although corrosion resistance is important, it must be premised that the recording / reproducing characteristics are sufficiently satisfied. And from such a viewpoint, C
Considering the o-Ni alloy, Co-Ni (80%-
A magnetic recording medium having a metal magnetic film made of a 20% alloy was not satisfactory. From this, as a result of further study based on a new viewpoint, it came back to the basic condition that the corrosion resistance only needs to secure the surface. As a result of further pushing this, the metal magnetic film is not composed of a single layer, but is composed of a plurality of layers, and the material forming the uppermost metal magnetic film is one having high corrosion resistance, and The inventors have come to the idea that a material having a high magnetic property may be used as the material forming the lower metal magnetic film.

The present invention has been achieved based on the above findings, and it is an object of the present invention to provide a magnetic recording medium having excellent recording / reproducing characteristics and corrosion resistance. An object of the present invention is to provide a first metal magnetic film containing Co or Fe as a main component on a support and a second metal magnetic film containing Ni thereon. This is achieved by the characteristic magnetic recording medium.

The magnetic characteristics of the first metal magnetic film and the second metal magnetic film in this magnetic recording medium are the saturation magnetic flux density in the lower layer (first metal magnetic film) from the viewpoint of recording / reproducing characteristics. And the upper layer (the metal magnetic film of 2) has excellent corrosion resistance and high coercive force. or,
The upper and / or lower metallic magnetic films are preferably formed in a state in which an oxidizing gas is sprayed.

Particularly, the Ni content of the second metal magnetic film is 4
It is preferably 0 to 100%, and its thickness is preferably 100 to 500Å. That is, Co and Fe forming the first metal magnetic film have excellent magnetic characteristics, but have poor corrosion resistance. Therefore, the second metal magnetic film formed on the first metal magnetic film has the above-described structure. I liked to do it.

The present invention will be described in more detail below. FIG. 1 shows a schematic sectional view of a magnetic recording medium according to the present invention. In the figure, 1 is a non-magnetic support, and this support 1
Is a polymer material such as polyester such as polyethylene terephthalate, polyamide, polyimide, polysulfone, polycarbonate, olefin resin such as polypropylene, cellulose resin, vinyl chloride resin,
Inorganic materials such as glass and ceramics, and metal materials such as aluminum alloys are used.

An undercoat layer 2 for improving the adhesion of the magnetic layer is provided on the surface of the support 1. That is, in order to improve the adhesion of the magnetic layer formed by dry plating by appropriately roughening the surface roughness and further improve the runnability by making the surface roughness of the magnetic recording medium surface moderate, for example, The undercoat layer 2 is formed by providing a coating film containing particles such as SiO ₂ and having a thickness of 0.005 to 0.1 μm.

A metal thin film type first metal magnetic film 3 is provided on the undercoat layer 2 by, for example, an oblique vapor deposition apparatus. For example, Co or Fe having a purity of 99.95% or more in a vacuum atmosphere of about 10 ⁻⁴ to 10 ⁻⁶ Torr.
Are evaporated by resistance heating, high frequency heating, electron beam heating, etc. and deposited (evaporated) on the surface of the undercoat layer 2 of the support 1, so that the first metal magnetic film 3 becomes 0.02%.
It is formed to a thickness of 1 μm.

The first metal magnetic film 3 is purely for recording / recording.
It is constructed only by considering the requirements from the reproduction characteristics. Therefore, considering the corrosion resistance, the first metal magnetic film 3 is not made of a Co—Ni (80% -20%) alloy. Even if Ni is contained, this does not substantially deteriorate the magnetic characteristics of the Co metal. That is, it is important that the first metal magnetic film 3 is composed of a material containing Fe and Co as main components.

After the first metal magnetic film 3 having excellent magnetic characteristics is formed as described above, the second metal magnetic film 4 is formed on the first metal magnetic film 3 by 100 to 500.
Å Thickness is provided. The method of forming the second metal magnetic film 4 may be the same as that of the first metal magnetic film 3 or may be different.

For example, a Co--Ni (40% -60%) alloy is used as a constituent material of the second metal magnetic film 4, and a film is formed in the same manner as the first metal magnetic film 3. May be. Since the second metal magnetic film 4 takes corrosion resistance into consideration, when forming the second metal magnetic film 4, a method of supplying oxygen and forming an oxide film may be adopted. preferable.

In other words, the second metal magnetic film 4 is provided without considering the magnetic characteristics, but is provided from the viewpoint of considering the corrosion resistance while considering the magnetic characteristics. Therefore, it is preferable to adopt a method in which the second metal magnetic film 4 is configured by an ion assisted oblique vapor deposition apparatus and various ions and oxygen gas are positively supplied.

Reference numeral 4a is an oxide film on the surface of the second metal magnetic film 4 configured from the above viewpoint. Reference numeral 5 is a lubricant layer provided on the second metal magnetic film 4. That is, the lubricant layer 5 having a thickness of about 5 to 50 Å, preferably about 10 to 30 Å is provided by applying a coating material containing a lubricant by a predetermined means.

Reference numeral 6 is a back coat layer provided on the other surface of the substrate 1 and containing carbon black or the like. Less than,
A specific example is given and demonstrated.

[0019]

【Example】

Example 1 A PET film provided with an undercoat layer having a thickness of 10 μm was attached to a first oblique vapor deposition apparatus,
Also, the purity is 99.95% in the magnesium oxide crucible.
The above Co was charged, and the electron gun of 30 kW was operated to evaporate Co, and Co particles were deposited to a thickness of 1500Å on a PET film running at a running speed of 2 m / min.

After that, the P on which the first metal magnetic film is formed is formed.
The ET film was attached to the second oblique vapor deposition apparatus, and the purity of Co-Ni (40%-
60%) alloy, and actuating a 30 kW electron gun to evaporate Co-Ni particles and C on the first metallic magnetic film of the PET film running at a running speed of 2 m / min.
The o-Ni particles were evaporated to a thickness of 100Å. In addition, oxygen is supplied at the time of this vapor deposition. Therefore, an oxide film is formed on the surface of the second metal magnetic film made of a Co—Ni alloy formed on the PET film.

After that, a lubricant was applied to the surface of the second metal magnetic film, and a back coat layer was formed on the other surface of the PET film to obtain a magnetic recording medium as shown in FIG. [Example 2] A magnetic recording medium was obtained in the same manner as in Example 1, except that the thickness of the second metal magnetic film was 300 Å.

Example 3 A magnetic recording medium was obtained in the same manner as in Example 1, except that the constituent material of the second metal magnetic film was Ni (purity 99.9% or more). [Example 4] A magnetic recording medium was obtained in the same manner as in Example 3, except that the thickness of the second metal magnetic film was 200 Å.

[Example 5] A magnetic recording medium was obtained in the same manner as in Example 1 except that the constituent material of the first metal magnetic film was Fe (purity 99.9% or more). Example 6 A magnetic recording medium was obtained in the same manner as in Example 5, except that the constituent material of the second metallic magnetic film was Ni (purity 99.9% or more).

Comparative Example 1 A PET film provided with an undercoat layer having a thickness of 10 μm was mounted on a first oblique vapor deposition apparatus, and a crucible made of magnesium oxide had a purity of 9%.
Co of 9.95% or more was put in, and the electron gun of 30 kW was operated to evaporate Co to make the PET particles running at a running speed of 2 m / min.
It was vapor-deposited. Oxygen was supplied during this vapor deposition. Therefore, an oxide film is formed on the surface of the metal magnetic film made of Co formed on the PET film.

Then, a lubricant was applied to the surface of the metal magnetic film, and a back coat layer was formed on the other surface of the PET film to obtain a magnetic recording medium. [Comparative Example 2] In Comparative Example 1, instead of Co, Co-
The same operation is performed except that a Ni (80% -20%) alloy is used,
A magnetic recording medium was obtained.

[Comparative Example 3] In Comparative Example 1, 99.9
A magnetic recording medium was obtained in the same manner except that Fe (99.9% or more) was used instead of 5% or more Co. [Characteristics] The reproducing characteristics and the corrosion resistance of the magnetic recording media obtained in the above examples were examined, and the results are shown in Table 1 below.
Shown in. The reproduction characteristics were obtained by cutting the above into a tape shape with a width of 8 mm, placing it in a high band 8 mm cassette case, and examining the output at 1 MHz and 7 MHz using a device modified from a commercially available high band 8 mm VTR. is there.

Table-1 Regeneration output (dB) ΔBs (%) 1 MHz 7 MHz Example 1 +0.5 +5.0 3 Example 2 +0.5 +4.9 3 Example 3 +0.3 +4.5 2 Implementation Example 4 +0.4 +4.8 2 Example 5 +1.0 +5.5 3 Example 6 +1.1 +5.3 4 Comparative Example 1 +0.5 +5.2 14 Comparative Example 2 0 0 3 Comparative Example 3 +0. 6 +5.9 26 ΔBs: left for 4 weeks under conditions of temperature of 60 ° C. and humidity of 90% RH, and determine corrosion resistance by the rate of decrease of saturation magnetic flux. According to this, a plurality of metal magnetic films are provided on a support. , The lower layer side is made of one having excellent magnetic properties without considering the corrosion resistance, and the upper layer side is made with consideration of the corrosion resistance while considering the magnetic properties, so that the reproduction property and the corrosion resistance are both improved. Also has excellent features.

On the other hand, in the case of the conventional one, when the one having an excellent corrosion resistance is obtained, the reproduction characteristic is deteriorated, and when the one having an excellent reproduction characteristic is obtained, the corrosion resistance is sacrificed. , Only the one obtained at the sacrifice of either one is obtained. Therefore, such things are never satisfactory.

[0029]

[Effect] Excellent characteristics are exhibited in both reproduction characteristics and corrosion resistance.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a magnetic recording medium.

[Explanation of symbols]

 1 Support 2 Undercoat Layer 3 First Metal Magnetic Film 4 Second Metal Magnetic Film 4a Oxide Film 5 Lubricant Layer 6 Backcoat Layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Shiga 2606 Akabane, Kai-cho, Haga-gun, Tochigi Prefecture Kao Co., Ltd.

Claims (5)

[Claims] 1. A first metal magnetic film containing Co or Fe as a main component is provided on a support, and a second metal magnetic film containing Ni is provided on the first metal magnetic film. Magnetic recording medium. 2. The magnetic recording medium according to claim 1, wherein the first metal magnetic film has a high saturation magnetic flux density, and the second metal magnetic film has a high corrosion resistance and a high coercive force. . 3. The magnetic recording medium according to claim 1, wherein the metal magnetic film is formed in a state in which an oxidizing gas is sprayed. 4. The Ni content of the second metal magnetic film is 40 to 40.
It is 100%, The magnetic recording medium of Claim 1 characterized by the above-mentioned. 5. The thickness of the second metal magnetic film is 100 to 50.
The magnetic recording medium according to any one of claims 1 to 4, wherein the magnetic recording medium is 0Å.