JPH10105951A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium exhibiting stable output and high S/N ratio by obtaining a magnetic recording medium small in the difference between the output in a 1st angle direction to the medium and the output in a 2nd angle direction different from the 1st angle direction. SOLUTION: The magnetic recording medium obtained by forming one or more magnetic layers on a long size non-magnetic supporting body is formed so as to reduce the difference between the output in the 1st angle direction and the output in the 2nd angle direction different from the 1st angle direction. In such a case, the difference between the 1st angle and the 2nd angle to the longitudinal direction of the non-magnetic supporting body is preferably controlled to 20 deg. in the view point of measurement. In the case of producing the magnetic recording medium, the magnetic recording medium obtained by film- forming a protective layer at first on a PET film on which a single layer of a metal cobalt magnetic layer is formed, applying a fluorine based lubricant and vapor depositing a back coat layer on the surface opposite to the magnetic layer is cut at 0 deg. and 20 deg. to the longitudinal direction to manufacture a desired video set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic recording medium. More specifically, the present invention relates to a magnetic recording medium that can realize a stable output and a high S / N ratio.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable improvement in performance of a magnetic recording medium such as a magnetic tape. As for magnetic tapes, taking video tapes as an example, VHS, 8 mm video tapes, and DVCs have been reduced in size, while high-density recording has also been advanced. By the way, the magnetic layer on the magnetic recording medium
When the recording density is low, it is formed by a method of applying an oxide-based magnetic material. However, as the recording density increases, the performance required for the magnetic layer formed by the coating method cannot be sufficiently satisfied because the thickness of the magnetic layer is large or the magnetic particles forming the magnetic layer are large.
Fe, which has better magnetic properties than oxide-based magnetic materials,
A metal or alloy magnetic layer mainly composed of a ferromagnetic element such as Co or Ni is formed on a support by a vacuum film forming method. A metal thin film magnetic layer is formed by applying an oxide magnetic material to a magnetic layer. The thickness of the magnetic layer can be made smaller than that of the magnetic recording medium, and the density of the magnetic material can be increased because it does not contain a binder. Further, the metal thin film magnetic layer has attracted attention because it can easily control the structure in the direction perpendicular to the support, and is suitable for high-density recording and digital recording as compared with longitudinal magnetic recording.

[0003]

[0005] Currently commercially available video decks employ a helical scan system in which recording is performed diagonally on a video tape. At the same time, azimuth recording by two heads is also performed.
High density recording is achieved by these two. When performing azimuth recording, it is necessary that the output difference between the two heads A and B used for the same input signal is small. That is, it is desired that the reproduction output of the magnetic tape be small in angle dependence with respect to the longitudinal direction of the magnetic tape. However, a magnetic recording medium as described above has not yet been obtained. Therefore, in the present invention, a stable output and a high S
It is an object to obtain a magnetic recording medium having a / N ratio.

[0004]

The magnetic recording medium obtained by the present invention is a magnetic recording medium comprising at least one magnetic layer formed on a long non-magnetic support. The difference between the output in the first angular direction and the output in a second angular direction different from the first angular direction is small, whereby a stable output and a high S / N ratio are realized. It is a tape. Here, the difference between the first angle and the second angle with respect to the longitudinal direction of the nonmagnetic support is 10 to 30
Degree, and preferably 20 degree in terms of measurement. Further, from the practical viewpoint of the magnetic recording medium, it is particularly preferable that the first angle is 0 degree with respect to the longitudinal direction of the non-magnetic support and the second angle is 20. In addition, when recording and reproducing a signal of a high-frequency wavelength and measuring an output difference at the first angle and the second angle with respect to the longitudinal direction of the non-magnetic support, the wavelength is not particularly limited. From the viewpoint of clearly measuring the characteristics or from a practical viewpoint, it is preferable to use a signal having a wavelength of 0.50 μm or less. Furthermore, for that signal,
The output difference is less than 2 dB.

The non-magnetic support used in the present invention is preferably polyethylene terephthalate (PET) from the viewpoint of cost. However, in addition, use of polyesters such as polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polycarbonate, polyvinyl chloride, polyimide, and aromatic polyamide. Can be. The thickness of these non-magnetic supports is generally considered to be about 50 μm, but is preferably 6.3 μm or less from a practical viewpoint in the future.

In the present invention, the metal thin film type magnetic layer is formed by a vacuum film forming method. Examples of the magnetic material for forming the metal thin film type magnetic layer include ferromagnetic metal materials used for manufacturing a normal metal thin film type magnetic recording medium. For example, C
o, Ni, a ferromagnetic metal such as Fe, or Fe-Co,
Fe-Ni, Co-Ni, Fe-Co-Ni, Fe-C
u, Co-Cu, Co-Au, Co-Y, Co-La,
Co-Pr, Co-Gd, Co-Sm, Co-Pt, N
i-Cu, Mn-Bi, Mn-Sb, Mn-Al, Fe
-Cr, Co-Cr, Ni-Cr, Fe-Co-Cr,
Ferromagnetic alloys such as Ni-Co-Cr are exemplified. In particular, from the viewpoint of the magnetic properties of the magnetic material used for the magnetic recording medium,
At least one selected from ferromagnetic alloys mainly composed of Co, Ni, and Fe and nitrides or carbides thereof is preferable. The durability can be improved by introducing an oxidizing gas at the time of vacuum film formation to form an oxide layer on the surface of the magnetic layer. The magnetic layer formed by vacuum film formation may be a single layer or a multilayer of two or more layers, but is preferably a multilayer for high-density recording, and a practical range of two to three layers is appropriate. It is preferable that the magnetic layer of the magnetic recording medium is formed on the non-magnetic support by oblique evaporation. The method of oblique deposition is not particularly limited, and follows a conventionally known method.In the present invention, in order to obtain particularly good magnetic properties, an electron gun for evaporating a material to be deposited is installed in parallel. It is preferable to use two electron guns. The thickness of the metal thin film type magnetic layer is not limited, but may be 500-5000.
好 ま し く is preferred, and particularly 800 to 3000 as a practical range.
Å is preferred. In the case of two layers, the lower layer is 200 to 2
The upper layer is preferably about 100-1000 °, and in the case of three layers, the lower layer is about 200-2000 °, the middle layer is about 200-2000 °, and the upper layer is 100-1000.
Å is preferred.

[0007] A backcoat layer may be formed on the surface of the non-magnetic support opposite to the surface on which the magnetic layer is formed. The back coat layer may be formed by applying a liquid in which carbon black or the like is dispersed in an appropriate solvent, or by forming a metal or metalloid by physical vapor deposition, particularly thermal evaporation or sputtering. May be. Although the thickness of the back coat layer is not particularly limited, the thickness after drying is 0.4 to 1.0 μm when formed by coating, and 0.05 to 1 when formed by physical vapor deposition. It is about 0.0 μm.

For the purpose of improving the durability and corrosion resistance of the magnetic recording medium, a protective layer of a high hardness thin film can be provided on the magnetic layer and the back coat layer. Such a protective layer is made of a non-magnetic material such as carbide, nitride, or oxide such as diamond-like carbon, boron carbide, silicon carbide, boron nitride, silicon nitride, silicon oxide, or aluminum oxide. The film is formed by the PVD method. The thickness of the protective layer is 50 to 300 in view of the function of the protective layer.
Å is preferred.

A lubricating layer made of a suitable lubricant may be formed on the protective layer on the magnetic layer and the back coat layer or on the protective layer on the magnetic layer and the protective layer on the back coat layer. The lubricating layer may be formed by applying a solution obtained by dissolving a lubricant in an appropriate solvent, or may be formed by spraying the lubricant in a vacuum. As the lubricant, a fluorine-based lubricant such as perfluoropolyether is preferable from the viewpoint of lubricating property in either application or spraying. For example, the molecular weight of perfluoropolyether is 2,000 to 5,
000 are preferred. The amount of the lubricant to be applied or sprayed is determined as appropriate depending on the use of the magnetic recording medium and the type of the lubricant.
It is about.

[0010]

FIG. 1 shows an example of a vapor deposition apparatus 1 suitable for manufacturing a magnetic recording medium according to the present invention. Here, a vacuum chamber 2 connected to a vacuum evacuation device (not shown), a cooling can roll 3 provided in the vacuum chamber 2, and a nonmagnetic support 4 such as a PET film running on the cooling can roll 3. Unwinding roll 5 for
And a take-up roll 6. A crucible 7 is disposed vertically below the rotation axis of the cooling can roll 3 as an evaporation source, and a magnetic material, for example, metallic cobalt is accommodated in the crucible 7. In the vacuum chamber 2, electron guns 8, 8 ′ arranged at a specific interval in a direction perpendicular to the traveling direction of the non-magnetic support 4 are arranged, and an electron beam is irradiated toward the crucible 7. It is designed to evaporate metallic cobalt. Between the crucible 7 and the cooling can roll 3, there is provided a deposition preventing plate 9 for limiting the minimum incident angle of the metal cobalt vapor from the crucible 7 evaporated by the electron beam toward the cooling can roll 3 to the non-magnetic support 4. Are located. A nozzle 10 for supplying oxygen gas is disposed between the deposition preventing plate 9 and the cooling can roll 3.

The manufacture of a magnetic recording medium according to the present invention using such a vapor deposition apparatus 1 is as follows. That is, after the inside of the vacuum chamber 2 is evacuated to a predetermined degree by the vacuum exhaust device, the non-magnetic support 4 is run from the unwinding roll 5 onto the cooling can roll 3. At this time, the back coat may or may not be formed on the nonmagnetic support in advance on the surface opposite to the surface on which the magnetic layer is formed on the supportive support. The electron gun 8, 8 ′ irradiates the crucible 7 with an electron beam, melts and evaporates the metal cobalt in the crucible 7, and performs vapor deposition on the nonmagnetic support 4. This is performed in the presence of oxygen supplied from the nozzle 10. Non-magnetic support 4 thus treated
Is wound on a winding roll 6. After this, if necessary, a protective layer made of diamond-like carbon is formed on the magnetic layer on the non-magnetic support by using the ECR plasma CVD method, and a perfluoropolyether-based lubricant is applied by a coating method. A lubrication layer may be formed. After the formation of the necessary layers is completed, slitting, wrapping, assembling into a cassette, and the like are performed by a general method. The output is measured by a drum tester, and the S / N ratio is measured by a noise meter, an oscillator, and a VTR.

[0012]

【Example】

Example 1 PET having a thickness of 6.3 μm using the vacuum evaporation apparatus 1 of FIG.
2000 single metal cobalt magnetic layer per film
Å A film was formed. The film forming conditions were as follows: the distance between the electron guns was 8 cm, the output of each electron gun was 30 kV, and the film running speed was 1 minute.
5m, introduce oxygen gas at 55SCCM from gas nozzle,
The minimum angle of incidence was 50 °. Then ECR as a protective layer
A diamond-like carbon film is formed to a thickness of 100 ° by plasma CVD, and a fluorine-based lubricant is coated on the protective layer so that the film thickness after drying becomes 20 °, and the surface of the PET film opposite to the magnetic layer is dried. Then, a back coat layer made of aluminum was adhered by vapor deposition at 2000 °. The magnetic recording medium obtained as described above is
An 8 mm wide video cassette was produced by cutting it at an angle of 0 degree and 20 degrees with respect to the longitudinal direction.

Example 2 In the same manner as in Example 1, a single metallic cobalt magnetic layer was formed on the PET film used in Example 1 at 1950 °. The film forming conditions were as follows: the distance between the electron guns was 12 cm, and the gas nozzle was 48 SC.
Example 1 is the same as Example 1 except that oxygen gas was introduced by CM and the minimum incident angle was 42 °. Further, a protective layer, a lubricating layer, and a back coat layer were formed in the same manner as in Example 1, and were cut into 8 mm widths at an angle of 0 degree and 20 degrees in the longitudinal direction.
A mm video cassette was prepared.

Example 3 In the same manner as in Example 1, a single metal cobalt magnetic layer was formed on the PET film used in Example 1 at a thickness of 1970 °. The film forming conditions were as follows: the distance between the electron guns was 15 cm;
Example 1 is the same as Example 1 except that oxygen gas was introduced by CM and the minimum incident angle was 38 °. Further, a protective layer, a lubricating layer, and a back coat layer were formed in the same manner as in Example 1, and were cut into 8 mm widths at an angle of 0 degree and 20 degrees in the longitudinal direction.
A mm video cassette was prepared.

COMPARATIVE EXAMPLE 1 A 6.3 μm-thick PE was formed using the vacuum deposition apparatus 11 shown in FIG.
A single metallic cobalt magnetic layer was formed on the T film by 198.
0 ° was formed. The deposition conditions were as follows: the output of the electron gun was 30 kV, the film traveling speed was 15 m / min, and 53 SC from the gas nozzle.
Oxygen gas was introduced by CM, and the minimum incident angle was 47 °.
Thereafter, as a protective layer, diamond-like carbon is deposited to a thickness of 100 ° by ECR plasma CVD, and a fluorine-based lubricant is coated on the protective layer so that the thickness after drying becomes 20 °. A back coat layer made of aluminum was deposited on the surface opposite to the above by vapor deposition at 2000 °. The magnetic recording medium obtained as described above is cut into an 8 mm width so as to form an angle of 0 degree and 20 degrees with respect to the longitudinal direction.
A video cassette was made.

Comparative Example 2 A single metallic cobalt magnetic layer was formed on the PET film used in Comparative Example 1 in the same manner as in Comparative Example 1 by using the vacuum evaporation apparatus 11 shown in FIG. The film formation condition is 5 from the gas nozzle.
Comparative Example 1 was the same as Comparative Example 1 except that oxygen gas was introduced at 5 SCCM and the minimum incident angle was 52 °. Further, a protective layer, a lubricating layer, and a back coat layer were formed in the same manner as in Comparative Example 1, and were cut into 8 mm widths at an angle of 0 degree and 20 degrees in the longitudinal direction to produce an 8 mm video cassette.

Performance Evaluation The magnetic recording media obtained in Examples and Comparative Examples as described above were evaluated as follows. The output of magnetic recording media cut at different angles was measured using a drum tester. The output difference between the A head and the B head was measured by connecting a Sony Hi8VTR (EV-S900) to an oscilloscope. The S / N ratio was measured using a noise meter (VH31AX) and an oscillator (TG7-1) manufactured by Shibasoku and a Hi8VTR (EV-S) manufactured by Sony.
900). The value of Comparative Example 1 was set to 0 dB as a reference. The results are as shown in Tables 1, 2 and 3. Table 1 shows that the magnetic recording media prepared by cutting out at 0 ° and 20 ° with respect to the longitudinal direction of the support have a.
The output difference between the respective outputs S0 and S20 in the signal of the wavelength of 49 μm is shown. Table 2 shows the output difference between the A head and the B head, and Table 3 shows the measurement results of the S / N ratio. Note that the measurement results in Table 3 show the Y signal and C
The signal was set to 0 dB.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

According to the present invention, there is provided a magnetic recording medium comprising at least one magnetic layer formed on a long non-magnetic support, and an output in a first angular direction with respect to the medium. By obtaining a magnetic recording medium having a small difference in output between the first and second angular directions different from the first angular direction, the output difference between the A and B heads is reduced. A magnetic recording medium that can realize an N ratio can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an apparatus that can be used for manufacturing a magnetic recording medium of the present invention.

FIG. 2 is a schematic view of an apparatus used for manufacturing a conventional magnetic recording medium.

[Explanation of symbols]

 1, 11 Vacuum evaporation device 2, 12 Vacuum chamber 3, 13 Cooling can roll 4, 14 Non-magnetic support 5, 15, Unwind roll 6, 16 Take-up roll 7, 17 Crucible 8, 8 ', 18 Electron gun 9, 19 Deposition plate 10, 20 Gas nozzle

Claims (6)

[Claims] 1. A magnetic recording medium comprising at least one magnetic layer formed on a long non-magnetic support, comprising: an output of the medium in a first angular direction; A magnetic recording medium having a small difference from an output in a second angular direction different from the output of the magnetic recording medium. 2. The magnetic recording medium according to claim 1, wherein a difference between the first angle and the second angle is 10 degrees to 30 degrees. 3. The magnetic recording medium according to claim 1, wherein a difference between the first angle and the second angle is 20 degrees. 4. The magnetic recording medium according to claim 1, wherein the first angle is 0 degrees with respect to a longitudinal direction of the non-magnetic support. 5. The magnetic recording medium according to claim 1, wherein the output difference is 2 dB or less with respect to a signal having a high-frequency wavelength. 6. The magnetic recording medium according to claim 1, wherein the magnetic layer is formed by oblique deposition in a vacuum.