JPH103640A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a good overwriting characteristic by specifying the thickness of the magnetic layer of a metallic thin film type which consists essentially of Co and for which a base hating a thickness of a prescribed range is used to the specific ratio of the thickness of this base and randomly changing the crystal faces of the metallic particles of columnar columns constituting the magnetic layer in the magnetic layer. SOLUTION: A film 1 is transported from an un-winding roll 2 over a can roll 3 to a take-up roll 4. The Co housed in the crucible 10 is irradiated with an electron beam from an electron gun 9 to evaporate the Co and the magnetic layer consisting of the Co is formed on the film 1 transported on the can roll 3. Gaseous oxygen is introduced from a gaseous oxygen introducing pipe 7 into a vapor deposition region to oxidize the Co surface. At this time, the vapor deposition conditions for randomizing the crystal faces are controlled. The thickness of the magnetic layer is usually selected from a range of 800 to 3000Å if this thickness is 1/70 to 1/15 of the thickness of the base. The magnetic layer is provided thereon with a protective layer having about 10 to 200Å thickness. As a result, the good overwriting characteristic is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ferromagnetic metal thin film type magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, magnetic recording is in the direction of high-density recording, and a magnetic recording medium having excellent high-frequency characteristics is demanded. Conventionally, a so-called coating type magnetic recording medium in which magnetic powder is dispersed in an appropriate binder and coated on a support is the mainstream, and various improvements have been made to meet the demand for high-density recording. Is approaching.

A so-called metal thin film type magnetic recording medium having a magnetic layer in which a magnetic metal is adhered to a support by vapor deposition or the like has been developed as a magnetic recording medium which can be expected to have a performance exceeding that of a coating type magnetic recording medium. Metal thin-film type magnetic recording media are considered to be promising for high-density recording because the magnetic layer does not contain a binder and can increase the density of a magnetic material. As the metal thin film type magnetic layer, Co, Co
-Ni, Co-Ni-P, Co-O, Co-Ni-O,
Co-Cr, Co-Ni-Cr and the like have been studied. A vacuum deposition method is most suitable as a manufacturing method when a metal thin film type magnetic recording medium is put into practical use.
Hi8 VTR tapes having a magnetic layer made of i-O and DVC (digital video cassette) tapes having a magnetic layer made of Co-O have already been put to practical use.

As a support for the magnetic recording medium, a non-magnetic support such as a plastic such as polyethylene terephthalate is used, and its thickness is, for example, VHS.
About 16 μm for type video tape, about 9 μm for 8 mm video tape, and about 6.3 μm for DVC (Digital Video Cassette), more support for achieving high-density recording (small and long time) It is thought that the body will be made thinner.

[0005]

Generally, a metal thin film type magnetic recording medium has a metal thin film formed on a flat support, but the metal thin film does not contain a binder and has high elasticity. May be distorted (so-called cupping). In general, the thickness of the magnetic layer in a metal thin film type magnetic recording medium is about 500 to 5000 °. When the thickness of the support is large, the effect of the elasticity of the metal thin film is small and does not cause much problem. It is anticipated that a thinner support will be used, in which case the elasticity of the metal thin film will have a significant effect and the head touch may be reduced. In addition, the overwrite characteristics are affected by the thickness and type of the magnetic layer. However, as described above, the thickness of the support has been reduced, and in order to improve the overwrite characteristics, the thickness of the support has to be reduced. It is required to form an appropriate magnetic layer according to the size.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above situation, and as a result, have found that the thickness is 2 μm or more and 6 μm or more.
The thickness of the magnetic layer is 1/70 to 1/15 of the thickness of the support, and the magnetic layer is formed in a metal thin film type magnetic layer containing Co as a main component and using a support having a thickness of less than m. The inventors have found that the above object can be achieved by randomly changing the crystal plane of the metal fine particles in the columnar column in the magnetic layer, and have completed the present invention.

That is, the present invention relates to a magnetic recording medium having a support having a thickness of 2 μm or more and less than 6 μm and a magnetic layer formed on the support and composed of columnar columns of a ferromagnetic metal containing Co as a main component. The thickness of the magnetic layer is 1/70 to 1/15 of the thickness of the support, and the direction of the crystal plane (Miller index) of the fine particles in the columnar column is randomly changed. A magnetic recording medium is provided.

[0008] The magnetic layer of the magnetic recording medium of the present invention is a so-called metal thin film type magnetic layer, and is formed of columnar columns of ferromagnetic metal. The thickness of the magnetic layer is one of the thickness of the support.
/ 70 to 1/15, preferably 1/60 to 1/20. As in the present invention, a thickness of 2 μm or more and 6 μm
When using a support having a thickness of less than the above range, good overwrite characteristics can be achieved by setting the thickness of the metal thin film type magnetic layer to this range.

In the magnetic recording medium of the present invention, the magnetic layer is composed of columnar columns made of a ferromagnetic metal containing Co as a main component. Exists, and the aggregate of the fine particles forms a column. The fine particles are also called crystallites.) The direction of the crystal plane having the same Miller index (hereinafter sometimes simply referred to as crystal plane) is The magnetic layer changes randomly in the magnetic layer. In other words, it means that the Miller index of the crystal plane viewed from the observer changes randomly.

The crystal plane is a plane that defines the outer shape of the crystal. In the present invention, “the direction of the crystal plane changes randomly” means that the “randomness” defined by the following method is 50%.
It means above. That is, the cross-sectional TEM of the magnetic layer
In the image, the diffraction image of the 1 nm spot electron beam
The value (%) calculated by 100-A is defined as the degree of randomness when the ratio of the largest crystal plane among the crystal planes having the same mirror index and oriented in the same direction is taken as 00%. The higher the value is, the more the crystal unit cells of the crystal plane oriented in different directions are. In other words, in the present invention, the Miller index is determined to determine a reference crystal plane, and the direction of the reference crystal plane in the magnetic layer is measured.

Many types and compositions of ferromagnetic metals to be used as magnetic layers are known. For example, ferromagnetic metals such as Co, Ni, and Fe, and Fe-Co, Fe-Ni, and Co-N
i, Fe-Co-Ni, Fe-Cu, Co-Cu, Co
-Au, Co-Y, Co-La, Co-Pr, Co-G
d, Co-Sm, Co-Pt, Ni-Cu, Mn-B
i, Mn-Sb, Mn-Al, Fe-Cr, Co-C
r, Ni-Cr, Fe-Co-Cr, Ni-Co-Cr
And other ferromagnetic alloys. Also, as the magnetic layer,
There is a magnetic layer containing nitride, carbide, or oxide of Co, Ni, Fe or a ferromagnetic alloy mainly containing these. In the present invention, among these, it is particularly desirable to form a metal thin film type magnetic layer containing Co as a main component. Here, “having Co as a main component” means that Co accounts for 50 atomic% or more of the metal constituting the magnetic layer.

A ferromagnetic metal thin film having crystal planes oriented in random directions can be formed by changing the deposition conditions. Specifically, there are methods of controlling the scanning direction of the electron gun at the time of vapor deposition, controlling the output of the electron gun, controlling the vapor deposition rate, controlling the oxidation method, and the like. Techniques may be combined.

The support of the magnetic recording medium of the present invention has a thickness of 2 μm or more and less than 6 μm. Examples of the material include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cellulose triacetate and cellulose. Cellulose derivatives such as diacetate; polycarbonate; polyvinyl chloride; polyimide; and plastics such as aromatic polyamide are used.

As described above, the magnetic recording medium of the present invention
When manufacturing a thin metal film type magnetic recording medium using a thin support having a thickness of at least 6 μm and less than 6 μm, a magnetic layer having an optimum thickness for obtaining good overwrite characteristics is formed. In addition, since the crystal plane of the metal crystal forming the magnetic layer is oriented in a random direction, it is considered that the stress of the support is reduced and the head touch is improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic recording medium of the present invention will be described.
An example in which a Co-based magnetic layer is formed will be described. FIG. 1 shows C
5 is a schematic view illustrating a main part of a vapor deposition apparatus for forming an o-based magnetic layer. In FIG. 1, 1 is a film, 2 is an unwinding roll, 3 is a can roll, 4 is a take-up roll, 5 is a bombardment treatment means, 6 and 6 'are expander rolls, 7 is an oxygen gas introduction pipe, and 8 is metal A shielding plate for regulating the region of the vapor, 9 is an electron gun, 10 is a crucible, which contains Co. These are arranged in a vacuum vessel (not shown), and the inside of the vacuum vessel is maintained at a degree of vacuum of about 1 × 10 ^{−4 to} 5 × 10 ⁻⁷ Torr. The film 1 is conveyed from an unwinding roll 2 to a take-up roll 4 via a can roll 3. Electron gun 9
Then, an electron beam was applied to Co stored in the crucible 10 to vaporize Co and form a magnetic layer made of Co on the film 1 conveyed on the can roll 3. Further, an oxygen gas is introduced from the oxygen gas introduction pipe 7 into the deposition region to oxidize the Co surface. At this time, to make the crystal plane random,
Adjust the deposition conditions.

In the present invention, the magnetic layer may have a multilayer structure. In this case, the magnetic layer (outermost layer) farthest from the support satisfies the above-mentioned thickness and the random orientation of the crystal plane. The magnetic layer is preferably It is more preferable that the other magnetic layers also satisfy the requirements of the thickness and the random orientation of the crystal plane specified in the present invention. When a magnetic layer having a multilayer structure is formed, the magnetic layer may be formed continuously using an apparatus as shown in FIG. 1 or may be formed by repeating vapor deposition a plurality of times (in a so-called batch system).

In the present invention, the thickness of the magnetic layer is not limited as long as it is 1/70 to 1/15 of the thickness of the support.
Usually, it is selected from the range of 800 to 3000 °. Also, when forming multiple magnetic layers, the thickness of each magnetic layer is 800 to
It is about 3000Å.

The magnetic layer has a thickness of 10 to 200 mm.
It is desirable to provide a protective layer of a certain degree, particularly a carbon thin film such as diamond-like carbon and graphite, a silicon-containing thin film such as silicon oxide (SiO _x ) and silicon carbide, and a zirconium oxide thin film. Further, it is preferable to form a lubricating layer having a thickness of about 2 to 50 °, particularly a lubricating layer made of a fluorine-based lubricant such as perfluoropolyether, on the magnetic layer or the protective layer. Further, on the surface opposite to the surface on which the magnetic layer is formed, a back coat layer or the like containing carbon black as a main component and having a thickness of about 0.1 to 1.0 μm may be further provided. As a raw material for forming these layers, conventionally known materials can be appropriately used. Further, a metal such as a Cu-Al alloy may be deposited to form a back coat layer having a thickness of about 500 to 5000 °. In addition, oxygen gas, nitrogen gas,
A ceramic material such as an oxide film, a carbonized film, a nitrided film, or a composite thereof, which is obtained by passing a carbon dioxide gas or the like and performing oxidation, carbonization, and nitridation, is particularly suitable.

[0019]

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) Production of Magnetic Tape A PET film having a thickness of 4.5 μm was set in the apparatus shown in FIG. 1, and Co was vapor-deposited while introducing oxygen gas to a thickness of 17 μm.
A magnetic layer of 00 ° was formed. The deposition conditions at this time were a film running speed of 50 m / min, an electron gun power of 50 kW, and an oxygen gas introduction amount of 800 SCCM. However, in order to make the crystal plane in the column structure of the magnetic layer random, a rectangular crucible that is long in the width direction with respect to the film was used, and the electron beam from the electron gun was slowly scanned in the width direction at 30 Hz to obtain the Co. Irradiation. The crystal plane of the magnetic layer was analyzed by a TEM image using the above-described method, and the most crystal plane in the same direction was measured. The most crystal plane was the (100) plane. Overall 3
Accounted for 5%. Therefore, the degree of randomness was 65%.

Next, an ECR plasma C is formed on the magnetic layer.
A protective layer composed of a diamond-like carbon thin film having a thickness of 100 ° was formed by the VD method. Further, a perfluoropolyether having a -OH group as a polar group (Demkin Industries, Ltd., Demnum SA) having a thickness of 20 was formed on the protective layer.
付 着 to form a lubricant layer. A back coat layer was formed on the surface of the film opposite to the surface on which the magnetic layer was formed. The back coat layer was formed by applying a binder containing carbon having a diameter of 20 to 30 nm to a film so that the thickness after drying was 0.5 μm, and drying the film. The film obtained above, on which the magnetic layer, the diamond-like carbon protective layer, the fluorine-based lubricating layer and the back coat layer were formed, was cut into a width of 8 mm and loaded into a cassette case to obtain an 8 mm video tape.

(2) Performance evaluation The envelope of the 8 mm video tape obtained above was evaluated as an index of head touch by the following method.
The overwriting characteristics were also evaluated by the following method. Table 1 shows the results. Envelope The envelope was measured using an advantest TR4171 type spectrum analyzer, RBW = 10 kHz, VB
The output waveform (envelope) obtained under the conditions of W = 30 kHz, frequency span = 0 MHz, sweep time = 40 ms, average = 16 times was measured, and the maximum value B and the minimum value A of the output waveform were measured as shown in FIG. Was calculated as the missing amount as follows. Chipping amount (dB) = 20 log (A / B) The smaller the chipping amount, the better the head touch. Overwrite characteristics (OW) W. The characteristics were measured using RBW = 10 kHz, VB
W = 30 kHz, frequency span = 0 MHz, sweep time = 40 ms, and after recording a signal with a recording wavelength λ = 1.0 μm, the peak value C of the reproduced spectrum and λ
= 1.0 μm only once where λ = 0.
Λ = 1.0 μm after overwriting a 5 μm signal
The overwrite characteristics were evaluated by the ratio D / C to the remaining amount D of the signal. Note that the overwrite characteristics are shown in Comparative Example 1.
Is expressed as a relative value with the value (0 dB) as a reference.

Example 2 In Example 1, the thickness of the film was 3.5 μm.
Using two electron guns, one output was set to 30 kW and the other output was set to 15 kW.
In the same manner as described above, Co was deposited while scanning in the width direction of the rectangular crucible to form a magnetic layer having a thickness of 1600 °. The oxygen gas introduction amount was 700 SCCM. The degree of randomness of the crystal plane in this magnetic layer was 70%. Otherwise, an 8 mm tape was produced in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. Table 1 shows the results.

Example 3 In Example 1, the thickness of the film was 5.9 μm,
Using two electron guns, one output is set to 100 kW and the other output is set to 20 kW. Co is deposited while scanning each electron beam in the width direction of the rectangular crucible in the same manner as in the first embodiment, and the thickness is set to 1000 Å. Was formed.
The oxygen gas introduction amount was 300 SCCM. The degree of randomness of the crystal plane in this magnetic layer was 70%. Otherwise, an 8 mm tape was prepared in the same manner as in Example 1,
The same evaluation as in Example 1 was performed. Table 1 shows the results.

Example 4 In Example 1, the thickness of the film was set to 5.0 μm.
Using two electron guns, one output was set to 70 kW and the other output was set to 40 kW.
Co was deposited while scanning in the width direction of the rectangular crucible in the same manner as in the above to form a magnetic layer having a thickness of 3000 °. The oxygen gas introduction rate was 800 SCCM. The degree of randomness of the crystal plane in this magnetic layer was 50%. Otherwise, an 8 mm tape was produced in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. Table 1 shows the results.

Comparative Example 1 In Example 1, a magnetic layer was formed by irradiating Co while fixing the electron beam from the electron gun without scanning, and by performing evaporation. The degree of randomness of the crystal plane in this magnetic layer is 3
It was 0%. Otherwise, the same as in Example 1, 8 mm
A tape was produced and evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 In Example 1, a magnetic layer was formed by scanning an electron beam from an electron gun at a high speed (1000 Hz), irradiating Co, and performing vapor deposition. The degree of randomness of the crystal plane in this magnetic layer was 40%. Otherwise, an 8 mm tape was produced in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. Table 1 shows the results.

Comparative Example 3 In Example 4, the thickness of the film was set to 5.0 μm.
The output of one of the two electron guns was set to 100 kW and the output of the other was set to 40 kW.
In the same manner as described above, Co was deposited while scanning in the width direction of the rectangular crucible to form a magnetic layer having a thickness of 5000 °. The oxygen gas introduction amount was 900 SCCM. The degree of randomness of the crystal plane in this magnetic layer was 50%. Otherwise, an 8 mm tape was produced in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. Table 1 shows the results.

Comparative Example 4 In Example 4, the thickness of the film was set to 5.0 μm.
One of the two electron guns has an output of 30 kW and the other output has a power of 10 kW, and scans each electron beam in the width direction of the rectangular crucible in the same manner as in the first embodiment.
O was deposited to form a magnetic layer having a thickness of 500 °. Also,
The oxygen gas introduction amount was 120 SCCM. The degree of randomness of the crystal plane in this magnetic layer was 55%. Otherwise, an 8 mm tape was produced in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. Table 1 shows the results.

[0030]

[Table 1]

[0031]

According to the present invention, even when a thin film is used as a support, a metal thin-film magnetic recording medium having good head touch and excellent overwrite characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a vapor deposition apparatus for manufacturing a magnetic recording medium of the present invention.

FIG. 2 is a model diagram showing maximum and minimum values of an envelope waveform.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Film 3 Can roll 7 Oxygen gas introduction pipe 9 Electron beam gun 10 Crucible

Claims (2)

[Claims] 1. A support having a thickness of 2 μm or more and less than 6 μm,
A magnetic recording medium having a magnetic layer formed of columnar columns of a ferromagnetic metal containing Co as a main component and formed on the support, wherein the thickness of the magnetic layer is 1/70 of the thickness of the support.
A magnetic recording medium wherein the direction of the crystal plane (mirror index) of the fine particles in the columnar column changes randomly. 2. The magnetic recording medium according to claim 1, comprising a protective layer formed on the magnetic layer, and a lubricant layer formed of a fluorine-based lubricant formed on the protective layer.