JPH10106834A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable obtaining appropriate stiffness, by causing a change in reflectance to be substantially constant in the case where a light of a specified wavelength is radiated to a medium. SOLUTION: After a predetermined degree of vacuum is provided in a vacuum chamber 2, a non-magnetic support 4 is caused to travel from a supply reel 5 onto a cooling can roll 3. An electron beam is radiated toward a crucible 7 from an electron gun 8, and a cobalt metal in the crucible 7 is melted and evaporated, thus carrying out evaporation to the non-magnetic support 4. This evaporation is carried out in the presence of oxygen supplied from a nozzle 10. The non-magnetic support 4 processed in this manner is wound on a take-up roll 6. A change in reflectance in the case where a light of a wavelength of 200 to 300nm is radiated to a magnetic recording medium is substantially constant, and the difference in reflectance between the case where a light of a wavelength of 850nm is radiated to the magnetic recording medium and the case where a light of a wavelength of 250nm is radiated to the magnetic recording medium is not less than 30%.

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 capable of obtaining appropriate stiffness, thereby obtaining good running properties and good head touch.

[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.

On the other hand, as magnetic tapes have become smaller, the thickness of the magnetic tape support has also become smaller. For example, VH
About 15.0 μm for S type video tape, about 9.0 μm for 8 mm video tape, and 6.3 μm for DVC
m. When the thickness of the support is reduced, the stiffness of the support as a whole is sharply reduced, and problems such as a decrease in output due to a poor head touch and a deterioration in running performance are caused. By the way, it is known that a metal thin-film magnetic substance has a resilience which cannot be ignored with respect to a support, since it does not contain a binder. In recent years, the back coat layer has been formed by a vacuum film forming method in order to solve problems such as poor conductivity and adhesion of dust, which have been problems in the conventional coating method. It now has considerable elasticity to the body.
Under such circumstances, the applicant of the present invention has proposed that the back coat layer is made of two or more layers of metal or metalloid to provide appropriate surface properties and elasticity.
Japanese Patent Application Laid-open No. Hei 8-98853 and Japanese Patent Application Laid-Open No. H8-102444 each propose that a backcoat layer is formed of a carbon-based film so that the backcoat layer has sufficient hardness. By doing so, attempts have been made to improve head touch and running performance.

[0004]

It is considered that magnetic recording media, especially magnetic tapes, will be required to be further miniaturized together with higher recording density. By the way, in order for the magnetic tape to achieve good head touch and good runnability,
The magnetic tape must have proper stiffness. Although the stiffness of the magnetic tape as a whole has been improved by the above proposal, sufficient performance has not yet been obtained. On the other hand, the reflectance of the surface of the magnetic layer formed on the support depends on the coordination number of the metal and the like. That is, the reflectivity of the magnetic layer surface is affected by the coordination number of the metal on the magnetic layer surface, that is, the degree of oxidation of the metal on the magnetic layer surface. Since the quality and hardness of the magnetic layer differ depending on the degree of oxidation, the reflectivity of the surface of the magnetic layer on the support is closely related to the stiffness of the entire magnetic tape.

Therefore, in the present invention, in view of the above situation, the change in reflectance when light having a wavelength of 200 to 300 nm is applied to the medium is substantially constant, and light having a wavelength of 850 nm is applied to the medium. By setting the difference between the reflectance in the case and the reflectance when the light having the wavelength of 250 nm is applied to the medium to 30% or more, it is possible to obtain an appropriate stiffness as the whole magnetic tape, and to achieve good running property and good running property. It is an object of the present invention to obtain a magnetic recording medium capable of obtaining a proper head touch.

[0006]

The magnetic recording medium obtained according to the present invention has a substantially constant change in reflectance when light having a wavelength of 200 to 300 nm is applied to the medium.
The reflectance when light of wavelength m is applied to the medium and 250 nm
30% difference from reflectivity when light of wavelength
With the above, an appropriate stiffness can be obtained, whereby the magnetic tape can achieve good running properties and good head touch.

The nonmagnetic 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 the vacuum film formation method 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. The thickness of the metal thin film type magnetic layer is not limited.
00 to 5000 ° is preferable, and particularly 8
00-3000 ° is preferred. In the case of two layers, the lower layer is about 200 to 2000 ° and the upper layer is 100 to 1000 °.
Å is preferred, and in the case of three layers, the lower layer is 200 to 20
About 00Å, middle layer about 200 ~ 2000Å, upper layer 1
It is preferably about 100 to 1000 °.

[0009] 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.

[0012]

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. An electron gun 8 is arranged in the vacuum chamber 2 and irradiates the crucible 7 with an electron beam to evaporate metallic cobalt in the crucible 7. Between the crucible 7 and the cooling can roll 3, there is a protection for limiting the minimum incident angle and the maximum incident angle of the metallic cobalt vapor from the crucible 7 evaporated by the electron beam toward the cooling can roll 3 to the non-magnetic support 4. The landing plates 9 and 9 'are arranged. A nozzle 10 for supplying oxygen gas is disposed between the deposition preventing plate 9 and the cooling can roll 3. Nozzle 10
The position of the gas supply port is determined as follows. That is, when the metal vapor reaches the cooling can roll 3, the positions on the cooling can roll 3 where the metal vapor forms the maximum incident angle and the minimum incident angle are point A and point B, respectively. The deviation from the point B in the direction of travel of the nonmagnetic support is positive, and the deviation in the direction opposite to the direction of travel of the nonmagnetic support is negative. Then, the gas is flowed from the gas supply port of the nozzle 10 toward the point C on the cooling can roll 3 which is a specific distance away from the point B with reference to the distance (AB) between AB.

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. Crucible 7 from electron gun 8
Is irradiated with an electron beam to melt and evaporate the metallic cobalt in the crucible 7, and vapor deposition is performed on the nonmagnetic support 4.
This is performed in the presence of oxygen supplied from the nozzle 10. The non-magnetic support 4 thus treated is wound on a take-up roll 6. Thereafter, if necessary, the ECR plasma CV is applied on the magnetic layer on the non-magnetic support.
A protective layer made of diamond-like carbon may be formed by the method D, and a lubricating layer may be formed by applying a perfluoropolyether-based lubricant by a coating method. After the formation of each required layer is completed, slitting,
Entrainment, cassette installation, etc. are performed. In addition, measure the output and envelope using a drum tester.
The Hi8VTR is modified and a jitter meter is connected to measure jitter, and the reflectance of the surface of the magnetic recording medium is measured with a spectroscopic altimeter.

[0014]

【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 deposition conditions were as follows: the output of the electron gun was 30 kV, the film traveling speed was 10 m / min, and 50 SCC from the gas nozzle.
At M, oxygen gas was introduced. The position of the gas supply port was point B. 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 °. 8 mm
An 8 mm video cassette was cut out to a width.

Example 2 In the same manner as in Example 1, a single-layer metallic cobalt magnetic layer was formed on the PET film used in Example 1 by 2030 °. The film forming conditions were the same as in Example 1 except that the oxygen gas introduction amount was 52 SCCM and the position of the gas supply port was shifted by 3 × (AB) / 10 in the direction of travel of the nonmagnetic support. Further protective layer,
A lubricating layer and a back coat layer were formed in the same manner as in Example 1, and 8
An 8 mm video cassette was cut out to a width of 8 mm.

Example 3 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 1960 °. The film forming conditions were the same as in Example 1 except that the oxygen gas introduction amount was 45 SCCM and the position of the gas supply port was shifted by (AB) / 5 in the direction of travel of the nonmagnetic support. Further, a protective layer, a lubricating layer, and a back coat layer were formed in the same manner as in Example 1, and 8 mm
An 8 mm video cassette was cut out to a width.

Comparative Example 1 In the same manner as in Example 1, a single-layer metallic cobalt magnetic layer was formed on the PET film used in Example 1 by 1990 °. The film forming conditions were the same as in Example 1 except that the oxygen gas introduction amount was 48 SCCM and the position of the gas supply port was shifted by (AB) / 5 in the direction opposite to the direction of travel of the nonmagnetic support. Further, a protective layer, a lubricating layer, and a back coat layer were formed in the same manner as in Example 1 and cut out to a width of 8 mm to produce an 8 mm video cassette.

Comparative Example 2 In the same manner as in Example 1, a single-layer metallic cobalt magnetic layer was formed on the PET film used in Example 1 by 2010 °. The deposition conditions were the same as in Example 1 except that the oxygen gas introduction amount was 51 SCCM, and the position of the gas supply port was shifted by 2 × (AB) / 5 in the direction opposite to the direction of travel of the nonmagnetic support. did. Further, a protective layer, a lubricating layer, and a back coat layer were formed in the same manner as in Example 1 and cut out to a width of 8 mm to produce an 8 mm video cassette.

Performance Evaluation The magnetic recording media obtained in the examples and comparative examples as described above were evaluated as follows. Output and envelope measurements were performed using a drum tester. The jitter was measured using a device modified from a commercially available Hi8 VTR and connected to a jitter meter. Measurement of the reflectance of the surface of the magnetic recording medium was performed using a spectrometer U3200 manufactured by Hitachi.
Was performed. The measurement was performed from above the lubricating layer of the magnetic tape in which the back coat layer, the magnetic layer, the protective layer, and the lubricating layer were formed on the tape. The results are as shown in Tables 1, 2, and 3.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

According to the present invention, the change in reflectance when light having a wavelength of 200 to 300 nm is applied to the medium is almost constant, and the change in reflectance when light having a wavelength of 850 nm is applied to the medium is 25%.
The difference in reflectance when light having a wavelength of 0 nm is applied to the medium is 3
By setting it to 0% or more, it is possible to obtain an appropriate stiffness, and it is possible to obtain a magnetic recording medium capable of realizing good running performance and good head touch.

[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.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum vapor deposition apparatus 2 Vacuum chamber 3 Cooling can roll 4 Non-magnetic support 5 Unwind roll 6 Take-up roll 7 Crucible 8 Electron gun 9, 9 'Detachment-proof plate 10 Gas nozzle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01F 41/20 H01F 41/20

Claims (4)

[Claims] In a magnetic recording medium having at least one magnetic layer formed on a tape-shaped non-magnetic support, a change in reflectivity is substantially reduced when light having a wavelength of 200 to 300 nm is applied to the medium. A magnetic recording medium characterized by being constant. 2. The magnetic recording medium according to claim 1, wherein
2. The magnetic recording medium according to claim 1, wherein a difference between the reflectance when the light having the wavelength of 250 nm is applied to the medium and the reflectance when the light having the wavelength of 250 nm is applied to the medium is 30% or more. 3. The magnetic recording medium according to claim 2, wherein
3. The magnetic recording medium according to claim 1, wherein a change in reflectance when light having a wavelength of 00 nm is applied to the medium is within 3%. 4. The magnetic recording medium according to claim 1, wherein the magnetic layer is formed by oblique evaporation in a vacuum.