JPH0992533A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize low noise high output and high C/N by a method wherein the ratio between the maximum and minimum values of coercive force acquired when the magnetic field angle θimpressed longitudinally is varied within a specific angle range is specified to be at a specific value. SOLUTION: A chamber is exhausted at the pressure down to 3×10<-7> Torr and then a PET film 9.8μm thick is wound from the feeding side roll to the winding side roll at a rate of 25m/min so that the PET film may be irradiated with electron beams from two electron guns in output of 30kw and 25kw to evaporate a magnetic metal. Besides, in case of evaporating the magnetic metal particles, oxygen at 130 and 110sccm is fed from respective oxygen gas feeding nozzles. Thus, a magnetic tape for 8mm VTR having dual layer laminated magnetic films (upper and lower layer magnetic films 800Å, 1200Å thick respectively) can be formed. Through these procedures, the ratio between the maximum value Hcmax and the minimum value Hcmin of coercive force acquired when the impressed magnetic field angle of this magnetic tape is varied from 0 deg. to 180 deg. will become 4-6.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a magnetic recording medium.

[0002]

In recent years, vapor deposition tape has been actively studied as a magnetic tape for high recording density. In particular, much research is being conducted to increase the coercive force Hc for the purpose of high output and high C / N. However, it has become clear that a high Hc is not enough. And while pushing forward the research, the characteristics of low noise, high output, high C / N, etc.
It has been found that the coercive force obtained when the applied magnetic field angle θ of the magnetic field applied to the longitudinal direction of the magnetic recording medium is varied from 0 ° to 180 °.

The present invention has been made based on this finding, and an object thereof is to provide a magnetic recording medium having low noise, high output, and high C / N.

[0004]

The object of the present invention is a magnetic recording medium in which a metal thin film type magnetic film is provided on a support, and a magnetic field applied in the longitudinal direction of the magnetic recording medium. A magnetic recording medium characterized in that the ratio Hcmax / Hcmin of the maximum value Hcmax and the minimum value Hcmin of the coercive force obtained when the applied magnetic field angle θ is varied from 0 ° to 180 ° is 4 to 6. It

Particularly, in a magnetic recording medium in which a metal thin film type magnetic film is provided on a support, the applied magnetic field angle θ of the magnetic field applied to the longitudinal direction of the magnetic recording medium is 0 ° to 1
Maximum coercive force Hcmax obtained when variable up to 80 °
And the minimum value Hcmin, the ratio Hcmax / Hcmin is 4 to 6,
The coercive force Hc0 when the applied magnetic field angle θ is 0 ° is 1100 Oe.
The above is achieved by a magnetic recording medium characterized by the above.

The minimum value Hcmin is in the region where the applied magnetic field angle θ is 50 to 80 °. The maximum value Hcmax is in the region where the applied magnetic field angle θ is 80 to 120 °. The coercive force Hc || in the in-plane direction of the magnetic film (coercive force Hc0 when the applied magnetic field angle θ is 0 °) is 1100 to 2500 Oe, and particularly 1200 to 1
800 Oe, coercive force Hc⊥ in the direction perpendicular to the magnetic film
(Coercive force Hc90 when applied magnetic field angle θ is 90 °) is 1500
˜3000 Oe, particularly 2000 to 2500 Oe is preferable.

Further, it is preferable that a plurality of magnetic films are laminated, and that the magnetic film on the upper side has a smaller thickness.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a magnetic recording medium in which a metal thin film type magnetic film is provided on a support, and an applied magnetic field angle θ of a magnetic field applied in the longitudinal direction of the magnetic recording medium.
The ratio Hcmax / Hcmin of the maximum value Hcmax and the minimum value Hcmin of the coercive force obtained when the value is varied from 0 ° to 180 ° is 4
~ 6. Particularly, in a magnetic recording medium in which a metal thin film type magnetic film is provided on a support, the applied magnetic field angle θ of the magnetic field applied to the longitudinal direction of the magnetic recording medium is from 0 ° to 1
Maximum coercive force Hcmax obtained when variable up to 80 °
And the minimum value Hcmin, the ratio Hcmax / Hcmin is 4 to 6,
The coercive force Hc0 when the applied magnetic field angle θ is 0 ° is 1100 Oe.
That is all.

The minimum value Hcmin is that the applied magnetic field angle θ is 50 to 8
The maximum value Hcmax is 0 ° when the applied magnetic field angle θ is 8
It is in the range of 0 to 120 °. The coercive force Hc || (Hc0) in the in-plane direction of the magnetic film is 1100 to 2500 Oe, and the coercive force Hc⊥ (Hc90) in the direction perpendicular to the magnetic film is 1500 to 3
It is 000 Oe. By the way, in view of recording / reproducing on a magnetic tape using a ring type magnetic head, it is advantageous that the coercive force Hc⊥ in the vertical direction is large.

However, it is not enough that Hc⊥ is large. That is, even with the same Hc⊥, the ratio Hcmax of the maximum value Hcmax and the minimum value Hcmin of the coercive force obtained when the applied magnetic field angle θ of the magnetic field applied to the longitudinal direction of the magnetic recording medium is changed from 0 ° to 180 °. A large difference was found in output and noise depending on / Hcmin. Representative examples showing the applied magnetic field angle dependence of the coercive force of the vapor deposition tape according to the present invention are shown in FIGS. According to this, the minimum value Hcmin is that the applied magnetic field angle θ is 50 to 80 °, especially 50 to 7
In the region of 0 ° (around 60 °), the maximum value Hcmax is 80 to 120 °, particularly 90 to 110 ° (1
(Around 00 °). In addition, FIG. 4 shows the applied magnetic field angle dependence of the coercive force of the vapor deposition tape of the comparative example. Also in this case, the minimum value Hcmin is in the region where the applied magnetic field angle θ is around 65 °, and the maximum value Hcmax is 100 cm.
° around the area.

However, the major difference between FIGS. 1 to 3 and FIG. 4 is that Hcmax / Hcmin is 4 in FIGS.
In contrast to the values of ˜6 in FIG. 4, Hcmax / H
cmin is about 3. Although the complete reason why the output and noise greatly differ due to this Hcmax / Hcmin is unknown, it is supposed that the magnetization directions are not aligned when Hcmax / Hcmin is smaller than 4. However, although the reason is not clear, Hcmax / Hcmin
If the value is less than 4 and it is too small, the output characteristics deteriorate and Hcm
Noise increased when ax / Hcmin exceeded 6 and was too large.

The applied magnetic field angle dependency of the coercive force is performed as shown in FIG. That is, a magnetic field along the X-axis direction is applied, and the angle θ formed by the magnetic field application direction and the longitudinal direction of the magnetic recording medium is 0 ° to 1 at intervals of 5 ° to 15 °.
Change between 80 ° and obtain the coercive force. The applied magnetic field angle-dependent patterns shown in FIGS. 1 to 4 are shown in this way. In FIG. 5, 1 is a support, 2a and 2b are magnetic films, 3 is a protective film, 4 is a lubricant film, and 5 is a back coat film.

In addition, when the coercive force Hc0 when the applied magnetic field angle θ is 0 ° is 1100 Oe or more, particularly 1300 Oe or more, the output characteristics are improved and the noise is small. In addition, the coercive force Hc || (Hc0) in the in-plane direction of the magnetic film is 1100 to 2500 Oe, and the coercive force Hc⊥ (Hc90) in the direction perpendicular to the magnetic film is 1500 to 3
In the case of 000 Oe, the output characteristics were improved and the noise was small.

A magnetic recording medium having the above-mentioned pattern of the present invention and showing an applied magnetic field angle dependency is obtained as follows. First, the continuous oblique vapor deposition apparatus of FIG. 6 is prepared. Figure 6
Inside, 10a is a supply side roll of the support body 1, 10b is a winding side roll of the support body 1, 11 is a cooling drum, and the support body 1 is from the supply side roll 10a to the cooling drum 11
After that, it is taken up by the take-up side roll 10b. The support 1 may be either magnetic or non-magnetic, but is generally non-magnetic. Such a support 1 is made of PE
Organic materials such as polyesters such as T, polyamides, polyimides, polysulfones, polycarbonates, olefin resins such as polypropylene, cellulose resins, and vinyl chloride resins are mainly used. An undercoat layer for improving the adhesion with the magnetic film is appropriately provided on the surface of the support. Reference numerals 12a and 12b are crucibles, 13a and 13b are magnetic metals filled in the crucibles 12a and 12b, and the magnetic metals 13a and 13b receive an electron beam from the electron guns 14a and 14b, evaporate, and run. Deposit on top. Examples of magnetic metal materials for forming the metal magnetic film include metals such as Fe, Co, and Ni, as well as Co—Ni alloys, Co—Pt alloys, and Co—N.
i-Pt alloy, Fe-Co alloy, Fe-Ni alloy, Fe
-Co-Ni alloy, Fe-Co-B alloy, Co-Ni-
Fe-B alloy, Co-Cr alloy, etc. are used. In addition, as the metal magnetic film, a nitride (for example, Fe-
N, Fe-NO) and carbides (for example, Fe-CO)
And the like. Then, first, magnetic metal particles from the crucible 12a set at a predetermined position are deposited on the support 1 running in the chamber 15 evacuated to 10 ^-4 to 10 ^-6 Torr, and the lower magnetic film 2a is formed. Is formed. still,
When forming the lower magnetic film 2a, oxygen is supplied from the oxygen gas supply nozzle 16a, and the surface is oxidized. After that, magnetic metal particles from the crucible 12b set at a predetermined position are deposited on the lower magnetic film 2a to form the upper magnetic film 2b. When forming the upper magnetic film 2b, oxygen is supplied from the oxygen gas supply nozzle 16b, and the surface is oxidized.

In order to form a film having the applied magnetic field angle dependence pattern of the present invention, it is preferable to improve the particle property and pay attention to the control of oxygen distribution in the film. After the lower magnetic film 2a and the upper magnetic film 2b are laminated in this way, if necessary, the magnetic film is formed on the magnetic film with a thickness of about 50 to 200Å made of diamond-like carbon, boron carbide, silicon nitride, or the like. A protective film is provided. Further, a fluorine-based lubricant film such as perfluoropolyether is provided with a thickness of about 20 to 70Å.

A back coat film is also provided. When the back coat film is formed by coating, the particle size is 10 to 10
Carbon black of 0 nm is dispersed in a binder resin such as a vinyl chloride type or a urethane type, and the thickness after drying is 0.4 to 1 μm by a gravure method, a reverse method or a die coating method.
It is applied so that it becomes m. P for back coating film deposition
When the VD means is used, a metal material such as an Al—Cu alloy is placed in the evaporation source, and the evaporated metal particles are contained in an amount of 0.05 to 1 μm.
To deposit the thickness of. Then, a top coat layer may be provided on such a back coat film in order to improve running properties and durability.

[0017]

Example 1 The magnetic recording medium of this example was obtained by the continuous oblique vapor deposition apparatus shown in FIG. That is, the chamber 15 is evacuated to 3 × 10 ⁻⁷ Torr and the thickness is 9.8.
A PET film of μm is fed from the supply side roll 10a through the cooling drum 11 to the winding side roll 10b at 25 m / m.
The magnetic metal is evaporated by irradiating with an electron beam from the electron gun 14a having an output of 30 kw and the electron gun 14b having an output of 25 kw at an in speed. The vapor amount distribution of the vaporized particles by the electron beam is a Gaussian distribution, and the crucible is set so that its center lies between the maximum incident angle and the minimum incident angle. During vapor deposition of magnetic metal particles, 130 sccm of oxygen is supplied from the oxygen gas supply nozzle 16a and 110 sccm of oxygen is supplied from the oxygen gas supply nozzle 16b.

The two-layer laminated magnetic film thus obtained (the upper magnetic film has a thickness of 800Å and the lower magnetic film has a thickness of 120).
FIG. 1 shows an applied magnetic field angle dependence pattern of an 8 mm VTR magnetic tape having 0Å).

[0019]

Second Embodiment In the first embodiment, the degree of vacuum in the chamber 15 is 5 × 10 ⁻⁷ Torr and the output of the electron gun 14a is 27.
kw, the output of the electron gun 14b is 27 kw, the oxygen gas supply amount from the oxygen gas supply nozzle 16a is 100 sccm, and the oxygen gas supply amount from the oxygen gas supply nozzle 16b is 100 kcm.
8 mmV performed in the same manner as in Example 1 except that sccm was used.
A magnetic tape for TR was obtained.

The two-layer laminated magnetic film thus obtained (the upper magnetic film has a thickness of 1000 Å, the lower magnetic film has a thickness of 10).
The applied magnetic field angle dependence pattern of the magnetic tape for 8 mm VTR having 00 Å) is shown in FIG.

[0021]

Third Embodiment In the first embodiment, the degree of vacuum in the chamber 15 is 2 × 10 ⁻⁷ Torr and the output of the electron gun 14a is 30.
kw, the output of the electron gun 14b is 24 kw, the oxygen gas supply amount from the oxygen gas supply nozzle 16a is 150 sccm, and the oxygen gas supply amount from the oxygen gas supply nozzle 16b is 100 kcm.
8 mmV performed in the same manner as in Example 1 except that sccm was used.
A magnetic tape for TR was obtained.

The two-layer laminated magnetic film thus obtained (the upper magnetic film has a thickness of 700Å and the lower magnetic film has a thickness of 110).
FIG. 3 shows the applied magnetic field angle dependence pattern of the 8 mm VTR magnetic tape having 0Å).

[0023]

Comparative Example 1 In Example 1, the degree of vacuum in the chamber 15 was 5 × 10 ⁻⁵ Torr and the output of the electron gun 14 a was 27.
kw, the output of the electron gun 14b is 32 kw, the oxygen gas supply amount from the oxygen gas supply nozzle 16a is 60 sccm, and the oxygen gas supply amount from the oxygen gas supply nozzle 16b is 55 sc.
8 mm VTR according to Example 1 except for cm
Magnetic tape was obtained.

The two-layer laminated magnetic film thus obtained (the upper magnetic film has a thickness of 1500Å and the lower magnetic film has a thickness of 10)
The applied magnetic field angle dependence pattern of the magnetic tape for 8 mm VTR having 00 Å) is shown in FIG.

[0025]

Comparative Example 2 In Example 1, the degree of vacuum in the chamber 15 was 2 × 10 ⁻⁶ Torr and the output of the electron gun 14a was 34.
kw, the output of the electron gun 14b is 27 kw, the oxygen gas supply amount from the oxygen gas supply nozzle 16a is 50 sccm, and the oxygen gas supply amount from the oxygen gas supply nozzle 16b is 100 s.
8 mm VT performed in the same manner as in Example 1 except that ccm was used.
An R magnetic tape was obtained.

Thus, an 8 mm VTR magnetic tape having a two-layer laminated magnetic film (upper magnetic film thickness 1000 Å, lower magnetic film thickness 1500 Å) was obtained.

[0027]

COMPARATIVE EXAMPLE 3 In Example 1, the degree of vacuum in the chamber 15 was 3 × 10 ⁻⁷ Torr, and the output of the electron gun 14a was 37.
kw, the output of the electron gun 14b is 20 kw, the oxygen gas supply amount from the oxygen gas supply nozzle 16a is 30 sccm, and the oxygen gas supply amount from the oxygen gas supply nozzle 16b is 120 s.
8 mm VT performed in the same manner as in Example 1 except that ccm was used.
An R magnetic tape was obtained.

In this way, an 8 mm VTR magnetic tape having a two-layer laminated magnetic film (upper magnetic film thickness 1800 Å, lower magnetic film thickness 500 Å) was obtained.

[0029]

[Characteristics] For the magnetic tapes obtained in the above examples, Hc0 (H
c‖), Hcmin, Hc90 (Hc⊥), and Hcmax were examined, and the results are shown in Table-1. Also, the output and noise were examined, and are also shown in Table-1. Table-1 Coercive force (Oe) Hcmax / Output (dB) Noise (dB) Hc0 Hcmin Hc90 Hcmax Hcmin 5MHz 10MHz 5MHz 10MHz Example 11220 390 1890 1930 5.0 +1.8 +2.6 -1.5 -2.0 Example 21380 470 1930 1970 4.2 +1.6 +2.3 -1.9 -2.3 Example 3 1220 300 1760 1800 6.0 6.0 +2.1 +2.7 -0.9 -1.1 Comparative Example 11390 570 1890 1990 3.5 0 0 0 0 Comparative Example 21340 640 1910 1910 3.0 -0.3 -0.6 -0.7 -0.8 Comparative Example 3 1110 270 1700 1700 6.2 +1.5 +1.9 +1.1 +1.9

[0030]

As described above, a magnetic recording medium having high output and low noise can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the applied magnetic field angle dependence of the coercive force of the magnetic recording medium of Example 1.

FIG. 2 is a graph showing the dependence of the coercive force of the magnetic recording medium of Example 2 on the applied magnetic field angle.

FIG. 3 is a graph showing the dependence of the coercive force of the magnetic recording medium of Example 3 on the applied magnetic field angle.

FIG. 4 is a graph showing the dependence of the coercive force of the magnetic recording medium of Comparative Example 1 on the applied magnetic field angle.

FIG. 5 is an explanatory diagram of how to use the magnetic field angle dependency of coercive force.

FIG. 6 is a schematic view of an apparatus for manufacturing a magnetic recording medium of the present invention.

Claims (6)

[Claims] 1. A magnetic recording medium in which a metal thin film type magnetic film is provided on a support, and an applied magnetic field angle θ of a magnetic field applied to the longitudinal direction of the magnetic recording medium is from 0 ° to 180 °. Ratio of maximum value Hcmax and minimum value Hcmin of coercive force obtained when variable, Hcmax / H
A magnetic recording medium having a cmin of 4 to 6. 2. A magnetic recording medium having a metal thin film type magnetic film provided on a support, wherein an applied magnetic field angle θ of a magnetic field applied to the longitudinal direction of the magnetic recording medium is from 0 ° to 180 °. Ratio of maximum value Hcmax and minimum value Hcmin of coercive force obtained when variable, Hcmax / H
When the applied magnetic field angle θ is 0 °, the coercive force Hc0 is 1100 Oe when cmin is 4 to 6
A magnetic recording medium having the above. 3. The minimum value Hcmin has an applied magnetic field angle θ of 50 to 50.
The magnetic recording medium according to claim 1 or 2, wherein the magnetic recording medium is in an area of 80 °. 4. The maximum value Hcmax of the applied magnetic field angle θ is 80 to
The magnetic recording medium according to claim 1 or 2, wherein the magnetic recording medium is in an area of 120 °. 5. The coercive force Hc.parallel. In the in-plane direction of the magnetic film is 11.
The magnetic recording medium according to claim 1 or 2, wherein the magnetic recording medium has a coercive force Hc⊥ in the direction perpendicular to the magnetic film of 0.002 to 2,500 Oe. 6. The magnetic recording medium according to claim 1, wherein a plurality of magnetic films are laminated, and the upper magnetic film has a smaller thickness.