JPH0991659A - Magnetic recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic recording medium having improved output characteristics. SOLUTION: A film 4 is carried from a release roll 2 to a winding roll 3 along a cooling can roll 5 and a magnetic material is deposited on the film 4 by electron beam vapor deposition from a crucible disposed in a lower part. The coating region of the magnetic material vapor is limited by two shielding plates 8. The incident angle θ1 at the start point of the coating region and the incident angle θ2 at the end point of the region are specified to <=85 deg. and >=50 deg. respectively. The obtd. magnetic recording medium has such property that when the coercive force is measured while the direction of a magnetic field applied on the medium is changed from 0 deg. to 180 deg. around the longitudinal direction of the medium, the half width of the angle-coercive force curve ranges 85 deg. to 100 deg.. The angle of the magnetic field is defined by that the angle of the magnetic field applied is 0 deg. when a magnetic field is applied perpendicular to the longitudinal direction of the medium and parallel to the medium plane.

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, and more particularly to a metal thin film type magnetic recording medium having improved output and C / N characteristics and a method for manufacturing the same.

[0002]

2. Description of the Related Art A vapor-deposited magnetic recording medium, in which a metal thin film is formed on a support by electron beam heating, has a higher magnetic substance filling rate, and therefore has a thinner saturation magnetization than a coated magnetic recording medium. It has a large coercive force and is suitable for high-density recording and is used in various application fields. Regarding the manufacturing technology of such a vapor deposition type magnetic recording medium, for example, a video tape or an 8 mm video tape, many improvements have been proposed for the purpose of improving the characteristics. As an example,
41-19389 discloses that a so-called oblique vapor deposition technique is used to obtain a magnetic layer having an oblique column structure, thereby increasing coercive force and improving output.

Here, the coercive force Hc is conventionally measured by the following method. For example, in the case of a magnetic tape, a magnetic field is applied in the longitudinal direction of the magnetic tape, that is, parallel to the film formation direction, and then the magnetic tape is vibrated in the vertical direction to change the magnetic flux, which is electrically changed. It detects and obtains a measured value.

[0004]

As the frequency of the recording signal becomes higher and the recording wavelength becomes shorter, a magnetic recording medium having higher output and higher C / N is required. In this case, as the coercive force, the one measured by the conventional method as described above is used as an index, but the characteristics do not always match only the coercive force measured by the conventional method. Therefore, in addition to the measurement by the conventional method, it is considered important to describe the coercive force from a different point of view and obtain a magnetic recording medium satisfying this. From this point of view, it is an object of the present invention to specify a magnetic characteristic of a magnetic recording medium based on a measuring method different from the conventional one, and to provide a magnetic recording medium with high output and high C / N, and a manufacturing method thereof.

[0005]

A magnetic recording medium according to the present invention is a metal thin film type magnetic recording medium in which at least one magnetic layer is formed on a support. In the longitudinal direction of this magnetic recording medium, that is, perpendicular to the film forming direction of the magnetic layer,
A magnetic field is applied parallel to the plane of the magnetic recording medium, and the applied angle of the magnetic field to the magnetic recording medium at this time is 0 °. In the magnetic recording medium according to the present invention, when the coercive force is measured by changing the applied angle of this magnetic field from 0 ° to 180 ° around the longitudinal axis of the magnetic recording medium, the obtained applied angle-coercive force curve of The full width at half maximum is in the range of 85 ° to 100 °. If the full width at half maximum is less than 85 °, the output characteristics are not satisfactory because the magnetic layer protrudes only in the direction in which it exists. If the full width at half maximum is greater than 100 °, the directions of magnetization will be different and noise will increase. Half-width angle
It has been found that excellent output characteristics can be obtained by setting the angle within the range of 85 ° to 100 °.

Preferably, the coercive force when the applied angle is 0 ° is 650 Oe or more. This means that the minimum value in the applied angle-coercive force curve is kept above this value.

In the magnetic recording medium of the present invention, polyethylene terephthalate is preferred as the support. However, besides, polyesters such as polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonates; polyvinyl chloride; polyimides; The thickness of these supports is 3-50 μm
It is a degree.

Examples of the magnetic material used for forming the magnetic layer in the present invention include ferromagnetic metal materials used in the production of ordinary metal thin film type magnetic recording media.
For example, ferromagnetic metals such as Co, Ni, Fe, or Fe-Co, Fe-
Ni, Co-Ni, Fe-Co-Ni, Fe-Cu, Co-Cu, Co-Au, Co
-Y, Co-La, Co-Pr, Co-Gd, Co-Sm, Co-Pt, Ni-
Cu, Mn-Bi, Mn-Sb, Mn-Al, Fe-Cr, Co-Cr, Ni-C
Examples include ferromagnetic alloys such as r, Fe-Co-Cr, and Ni-Co-Cr. In particular, a ferromagnetic alloy mainly composed of iron, cobalt, and nickel, and at least one selected from nitrides and carbides thereof are preferable. In addition, the durability can be improved by introducing an oxidizing gas when forming the magnetic layer by vapor deposition and forming an oxide on the surface of the magnetic layer. The magnetic layer may have a single-layer structure or a multilayer structure. In order to cope with high frequency recording, it is preferable to use a multilayer, and as a practical range, two to three layers are appropriate. The thickness of the magnetic layer is 1000 to 3000
It is about Å, the lower layer is about 200 to 2000 Å in the case of two layers and the upper layer is preferably about 100 to 1000 Å, and the lower layer is about 200 to 2000 Å, the middle layer is about 200 to 1000 Å, the upper layer is about 3 layers.
About 100 to 1000Å is preferable.

According to the present invention, the following method is provided for manufacturing the magnetic recording medium as described above. That is, the manufacturing method of the present invention comprises forming a magnetic layer by electron beam vapor deposition of a magnetic material in a predetermined deposition area on a support running in a vacuum chamber. The incident angle is 85 ° or less, and the incident angle of vapor at the end of the deposition area is 50 ° or more.
Also, the energy of the magnetic material particles evaporated by the electron beam follows a Gaussian distribution.In this case, the beam position of the electron gun is set to the deposition area so that the deposition area is near the central area of the Gaussian distribution. Generally adjusted for can rolls. This allows particles with high energy to be deposited on the support. The degree of vacuum during vapor deposition is about 10 ⁻⁴ to 10 ⁻⁷ Torr. By keeping the incident angle within the above range and adjusting the beam position of the electron gun appropriately to form a film, the full width at half maximum of the applied angle-coercive force curve is within the range of 85 ° to 100 ° as described above. A magnetic recording medium can be obtained.

In the magnetic recording medium produced by the present invention, a back coat layer can be formed on the support on the surface opposite to the magnetic layer. The back coat layer may be formed before or after the formation of the magnetic layer. The backcoat layer may be formed by applying a backcoat paint by a conventional method, or may be formed by depositing a metal or a semimetal in vacuum. Although its thickness is not particularly limited, it is about 0.1 to 1.0 μm in the case of coating and about 0.05 to 1.0 μm in the case of vapor deposition. If necessary, a protective layer made of diamond-like carbon, boron carbide, silicon dioxide or the like and having a thickness of about 50 to 200 Å may be provided.

Further, a top coat layer made of a suitable lubricant may be formed on the magnetic layer. This is formed, for example, by applying a fluorine-based lubricant in the air or spraying it on the magnetic layer in a vacuum. The thickness of the top coat layer is 5-50
It is about Å. When a back coat layer is provided, a top coat layer can be formed on it.

[0012]

1 shows the principle of a measuring method for obtaining an applied angle-coercive force curve according to the present invention. The sample 1 obtained by cutting the magnetic recording medium obtained by depositing the magnetic layer is placed between the magnets 2 and 3 as shown in the drawing, and the direction of deposition of the magnetic layer, that is, the magnetic recording medium It is rotated about the longitudinal direction. Therefore, the angle of the magnetic field applied to the sample will change around the longitudinal axis of the magnetic recording medium. In this case, the magnetic field application angle when the magnetic field is applied in parallel to the sample plane, that is, the plane of the magnetic recording medium is θ = 0 °. The sample is vibrated along the longitudinal axis, and the coercive force Hc is measured based on the change in magnetic flux in this case. The value obtained when θ = 90 °, that is, when the sample plane is perpendicular to the magnetic field indicates the maximum coercive force by this measuring method.

FIG. 2 shows the applied angle measured according to FIG.
An example of a coercive force curve is shown. As shown in the drawing, in the present invention, the curve obtained by plotting the measurement from 0 ° to 180 ° requires that the angular range of the half width H be within the range of 85 ° to 100 °. Further, as shown in the figure, the coercive force at 0 ° is preferably 650 Oe or more.

FIG. 3 shows one specific example of the manufacturing method for obtaining the magnetic recording medium of the present invention. In the vacuumed chamber 1, from the unwinding roll 2 to the winding roll 3, a support such as a PET film 4
Are conveyed through the cooling can roll 5. A crucible 6 is disposed below the cooling can roll 5, the magnetic material contained therein is irradiated with an electron beam ε from an electron gun 7 to evaporate the magnetic material, and the PET film is placed on the cooling can roll 5. 4 is to be deposited. In this case, two shielding plates 8 are provided in order to limit the deposition area of the magnetic material vapor. One shielding plate defines an incident angle θ1 at the beginning of the deposition area and the other shielding plate defines an incident angle θ2 at the end of the deposition area. In the present invention, the positions of the shielding plate and the evaporation source, that is, the position of the electron beam from the crucible and the electron gun are adjusted so that θ1 is 85 ° or less and θ2 is 50 ° or more. Reference numeral 9 is a nozzle for supplying an oxidizing gas during vapor deposition.

Further, the irradiation position of the electron beam ε from the electron gun 7 to the magnetic material in the crucible 6 is adjusted so that the vicinity of the central area of the Gaussian distribution of the energy of the evaporated magnetic material particles is in the adhered area. It

[0016]

【Example】

Example 1 An apparatus as shown in FIG. 3 was constructed. 3 x vacuum chamber 1
The crucible 6 was evacuated to 10 ^-6 Torr and Co (1
(00%) and charged with an electron beam from the electron gun 7 with an output of 10 kW to create a vapor deposition atmosphere. The PET film 4 was run from the unwinding roll 2 to the winding roll 3 at 3 m / min, and oxygen was introduced at 70 SCCM from the oxygen nozzle. The incident angle θ1 at the beginning of the deposition area was 82 ° and the incident angle θ2 at the end of the deposition area was 65 °. The thickness of the obtained magnetic layer was 1800Å. Next, on the side opposite to the side on which the magnetic layer of the PET film is formed, a back coat paint obtained by dispersing carbon black having an average particle diameter of 40 nm in a binder resin of urethane prepolymer and vinyl chloride resin, It was applied by a die coating method so as to have a dry film thickness of 0.5 μm, and dried to form a back coat layer. Then, perfluoropolyether (FOMBLI
NZ DOL, made by Montecatini Co.) as a fluorine-based inert liquid (Fluorinert FC-77, made by Sumitomo 3M Ltd.)
The coating composition diluted and dispersed to 0.05% by weight was applied onto the magnetic layer by a die coating method so that the dry film thickness was 30 liters, and dried at 105 ° C to form a lubricating layer. The obtained product was cut to a width of 8 mm and loaded into a cassette to obtain a high band 8 mm VCR cassette tape.

Example 2 In Example 1, θ1 = 80 ° and θ2 = 53 °. Others were operated in the same manner to obtain a high band 8 mm VCR cassette tape.

Comparative Example 1 In Example 1, θ1 = 90 ° and θ2 = 45 °. Others were operated in the same manner to obtain a high band 8 mm VCR cassette tape.

Comparative Example 2 In Example 1, θ1 = 90 ° and θ2 = 40 °. Others were operated in the same manner to obtain a high band 8 mm VCR cassette tape.

Comparative Example 3 In Example 1, θ1 = 90 ° and θ2 = 60 °. Others were operated in the same manner to obtain a high band 8 mm VCR cassette tape.

With respect to the tapes obtained in Examples and Comparative Examples, the outputs at recording wavelengths of 1 MHz and 7 MHz were measured using a device obtained by modifying a commercially available VTR deck. The results are shown in Table 1. In Table 1, the output is a relative value based on Comparative Example 1. Further, sample pieces were prepared from these tapes, and the coercive force was measured while changing the applied angle of the magnetic field by the method shown in FIG. 1 to obtain the applied angle-coercive force curve. The full width at half maximum, coercive force at 0 ° and 90 ° for these are also shown in Table 1.

[0022]

[Table 1]

[0023]

As described above, according to the present invention, a magnetic recording medium having a high output and suitable for high density recording is provided.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a method for obtaining an applied angle-coercive force curve by changing an applied magnetic field according to the present invention.

FIG. 2 is an application angle required for the magnetic recording medium of the present invention.
It is an explanatory graph for showing the half value width of a coercive force curve.

FIG. 3 is a schematic view showing an example of an apparatus for manufacturing a magnetic recording medium of the present invention.

[Explanation of symbols]

 1 Chamber 2 Unwinding Roll 3 Winding Roll 4 Film 5 Cooling Can Roll 6 Crucible 7 Electron Gun 8 Shielding Plate 9 Nozzle H Half Width

Claims (3)

[Claims] 1. A metal thin film type magnetic recording medium having at least one magnetic layer formed on a support, the magnetic recording medium being perpendicular to the longitudinal direction of the magnetic recording medium and parallel to the plane of the magnetic recording medium. When the coercive force is measured by changing the applied angle when the magnetic field is applied to 0 °, and changing the applied angle of the magnetic field from 0 ° to 180 ° around the longitudinal axis of the magnetic recording medium, The half-width of the angle-coercive force curve is in the range of 85 ° to 100 °,
Magnetic recording medium. 2. The coercive force is 65 when the applied angle is 0 °.
The magnetic recording medium according to claim 1, which is 0 Oe or more. 3. A method of manufacturing a metal thin film type magnetic recording medium, comprising forming a magnetic layer by electron beam evaporation of a magnetic material in a predetermined deposition region on a support running in a vacuum chamber. The incident angle of vapor at the beginning of the deposition area is 85 ° or less, the incidence angle of vapor at the end of the deposition area is 50 ° or more, and the energy of the magnetic material particles vaporized by the electron beam is A method of manufacturing a magnetic recording medium, wherein the adhered area is in the vicinity of a central area of the Gaussian distribution according to a Gaussian distribution.