JPH11175972A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a large reproduced output at a lower frequency region even though the medium has a thin film thickness in a specific range by reducing the diameter of the can roll to a specific range while vapor depositing a magnetic layer. SOLUTION: A magnetic metal 20 is inserted into a crucible 19 located in a vacuum container 12 and the electron beams from an electron gun 21 provides a vapor environment. Then, a magnetic tape supporting body 14 is run over a can roll 13 whose diameter is set to be 15 to 30 cm and a magnetic layer having a film thickness of 100 to 140 nm is formed by sticking metallic vapor. By employing the can roll having a smaller diameter, setting the vapor flow density of the vapor deposition material to be a proper one and maintaining a specific geometric relationship between the can roll and the source of the vapor deposition, a large reproduced output is obtained at a lower frequency region. It is desirable to set the coercive force of the magnetic layer to be 1,000 to 1,450 Oe. If the force is smaller than the above level, no improvement is realized in the reproduced output at the lower frequency region. If the force exceeds the above level, no desirable effect is obtained. It is also desirable to set the curveture rate of the column, which forms the magnetic layer, to be 8 to 20%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium and a method for manufacturing the same. In particular, the present invention relates to a magnetic recording medium capable of obtaining high output even when the thickness of the magnetic layer is small, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Video tape recorders (VTRs) are widely used in general, but this is largely due to high performance and low cost of VTR devices and magnetic tapes. This trend is expected to continue.

[0003] In particular, since magnetic tapes are replaced like consumables, it is important to lower the price in terms of expanding demand. Various methods are conceivable to realize a low price, but the following is particularly necessary in actual operation. That is, reduction of the film formation time and reduction of the variable cost. These can be achieved by making the film thickness thinner.

[0004]

In recent years, the performance of magnetic tapes has been further improved. One of the factors is that the magnetic layer has been changed from a coating method to a coating method by a vapor deposition method. Since the magnetic recording tape formed by the vapor deposition method does not contain a binder in the magnetic layer, the density of the magnetic material can be increased, and the magnetic characteristics can be improved. Conventionally, when forming a magnetic layer in a vacuum evaporation apparatus, a can roll having a diameter of more than 30 cm has been used.
When the thickness of the magnetic layer is reduced with such an apparatus, the reproduction output, particularly in the low frequency region, is significantly reduced. For this reason, when forming a magnetic layer with a conventional vacuum deposition apparatus,
It is said that the film thickness needs to be about 180 nm.

Accordingly, an object of the present invention is to provide a magnetic recording medium capable of obtaining a high output even with a small film thickness, and a method of manufacturing the same.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by reducing the diameter of the can roll in a vapor deposition apparatus, even if the thickness of the magnetic layer is small, the reproduction is possible. The inventors have found that the output can be improved, and have completed the present invention. That is, the method for producing a magnetic recording medium of the present invention is a method for producing a magnetic recording medium by an oblique vacuum evaporation apparatus having a can roll, wherein the diameter of the can roll is 15 to 30 cm, and the film to be produced is a film. The magnetic layer has a thickness of 100 to 140 nm. 15 ~ 30cm diameter can roll, 100 ~ 1 film thickness
By forming a 40nm magnetic layer, high playback output,
In particular, a magnetic recording medium having a high reproduction output even in a low frequency region can be obtained. Although the cause of obtaining this high output is not clear at present, the present inventors are closely related to various factors such as the vapor flow density of the deposition material or the geometric relationship between the can roll and the deposition source. I believe that. The film thickness can be measured by taking a photograph of a cross section of the magnetic recording medium with a TEM.

In the magnetic recording medium of the present invention having a magnetic layer having a thickness of 100 to 140 nm, the coercive force of the magnetic layer is
Preferably it is 1000-1450 Oe. Coercivity 1000 Oe
If it is less than 10, the effect of improving the output in the low frequency region is small. Conversely, even if the coercive force exceeds 1450 Oe, the output cannot be significantly improved. The measurement of the coercive force can be performed by an ordinary method using a vibrating magnetometer (VSM).

Further, in the magnetic recording medium of the present invention having a magnetic layer having a thickness of 100 to 140 nm, it is preferable that a curvature ratio of a column forming the magnetic layer is 8 to 20%. If the curvature of the column deviates from 8% to 20%, the shape of the magnetic flux leaking from the head and the shape of the column greatly differ, so that sufficient recording cannot be performed. As a result, the output decreases during reproduction and the noise increases. A photograph of the cross section of the magnetic recording medium was taken by TEM, and a linear distance a from the upper end to the lower end of the column,
The maximum distance b from the line to the arc of the column was measured, and the ratio b / a between a and b was defined as the curvature.

In the present invention, when the atomic ratio of oxygen atoms on the surface layer side of the magnetic recording medium in the Auger profile of the magnetic layer of the magnetic recording medium is Os and the atomic ratio of oxygen atoms on the support side is Ob, Os / Ob It is desirable that ≧ 1.3. In a magnetic recording medium in which the thickness of the magnetic layer is 100 to 140 nm, by setting Os / Ob ≧ 1.3, the metal layer of the magnetic layer on the surface layer can be covered with an oxide layer to increase corrosion resistance and hardness, The durability can be further improved. When the value at which the atomic ratio of oxygen atoms is the lowest between the peaks on the surface layer side and the support side is Ol, Os / Ol ≧ 2.0
It is preferred that In a magnetic recording medium in which the thickness of the magnetic layer is 100 to 140 nm, by setting the value of Os / Ol indicating the degree of oxidation inside the magnetic layer to 2.0 or more, a magnetic metal portion having high magnetic properties can be formed inside the magnetic layer. And the coercive force can be improved. As a result, output characteristics can be improved. In the present invention, the surface side of the magnetic recording medium and the support side of the Auger profile of the magnetic layer indicate the peak points of the oxygen atom profile on the left and right sides, respectively, on the Auger profile.

In the present invention, an Auger profile,
That is, the control of Os / Ob or Os / Ol can be performed by changing the supply amount of oxygen between the central part and the peripheral part of the vapor at the time of vapor deposition. Specifically, by turning the oxygen supply nozzle toward the peripheral portion of the steam or the like, more oxygen gas can be supplied to the peripheral portion of the steam than in the central portion, and Os / Ob or Os / Ol can be increased.

Next, the magnetic tape manufactured by the present invention will be described. First, as the support, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN);
Polyolefins such as polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonate; polyvinyl chloride;
And aromatic polyamides. PE in terms of price
T is preferred.

The magnetic layer can be formed by using a ferromagnetic metal material used for manufacturing a normal magnetic recording medium. As a raw material of the ferromagnetic metal material, for example, Co, Ni, Fe
Ferromagnetic metals such as 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-Cr, Fe-Co-Cr, Ni
-Co-Cr and other ferromagnetic alloys. In particular, a ferromagnetic alloy mainly composed of iron, cobalt, and nickel, and at least one selected from nitrides and carbides thereof are preferable.
By introducing an oxidizing gas when forming the magnetic layer and forming an oxide on the surface of the magnetic layer, the durability can be improved. The number of magnetic thin films constituting the magnetic layer is preferably large in order to cope with high-frequency recording, but 1 to 5 is considered to be appropriate as a practical range.

The back coat layer is formed on the surface of the support opposite to the magnetic layer by a known method, for example, a plating method or a coating method.
It can be formed by a vacuum film forming method or the like. The back coat layer is formed of, for example, a metal such as Cu, Ni, or Al, or a semimetal such as C, Si, or Ge, or an oxide, nitride, or carbide thereof. The thickness of the back coat layer is, for example, 300 nm or less according to a plating method or a vacuum film forming method, and 0.8 μm according to a coating method.
m or less. In the magnetic recording medium of the present invention, the method of forming the back coat layer, the material to be formed, the thickness, and the like are appropriately determined according to the use of the magnetic recording medium or the relationship between the hardness and the magnetic layer formed on the support. Can be.

The protective layer can be formed on the magnetic layer and / or on the back coat layer. As a method of forming the protective layer, a known vacuum film forming method such as a CVD method or a PVD method can be used. The protective layer is formed by adhering a high-hardness material such as carbon or carbide, nitride, or oxide, particularly diamond-like carbon, diamond, boron carbide, silicon carbide, boron nitride, silicon nitride, silicon oxide, or aluminum oxide. It is formed by filming. The method for forming the protective layer, the material for forming the protective layer, and the like can be appropriately determined depending on the use of the magnetic recording medium. In general, the thickness of the protective layer is suitably 15 nm or less.

Further, the lubricating layer can be formed on the support on the outermost layer on the magnetic layer side and / or on the outermost layer on the opposite side to the magnetic layer. The lubricating layer is formed by a method in which a lubricant is dissolved in an appropriate solvent and applied, or a method in which the lubricant is sprayed by a sprayer equipped with an ultrasonic oscillator. Examples of the lubricant include a fluorine-based lubricant containing a benzene ring or a double bond, a branched chain, and the like, and a fatty acid-based lubricant. From the viewpoint of lubricity, a fluorine-based lubricant such as perfluoropolyether is used. Is preferred. As a perfluoropolyether, a molecular weight of 2,000 to
5000 is preferred, and commercially available ones can be used. The thickness of the lubricating layer is appropriately determined depending on the use of the magnetic recording medium, the type of the lubricant, and the like.

[0016]

FIG. 1 shows an example of an oblique vacuum evaporation apparatus suitable for manufacturing a magnetic recording medium according to the present invention. 11 is a vacuum evaporation device, 12 is a vacuum vessel, 13 is a can roll, 14 is a support, 15 is an unwinding roll, 16 is a take-up roll, 17 is a gas introduction pipe, 18a and 18b are anti-adhesion plates, 19 is a crucible , 20 is a magnetic metal and 21 is an electron gun. The vacuum container 12 is connected to a vacuum exhaust device (not shown), and has a predetermined degree of vacuum. The support 14 is run from the unwinding roll 15 to the winding roll 16. The crucible 20 is filled with a magnetic metal 21 and irradiated with an electron beam from the electron gun 21 to form a vapor deposition atmosphere. Deposition plate 18a
And 18b limit the minimum and maximum angles of incidence of the metal vapor. Metal vapor from the crucible 20 adheres to the support 14 running on the can roll 13 having a diameter of 15 to 30 cm,
A magnetic layer having a thickness of 100 to 140 nm is formed.

A magnetic recording medium having a magnetic layer formed as described above has a high reproduction output, particularly in the low frequency region.

[0018]

EXAMPLE Using a vacuum deposition apparatus as shown in FIG.
A Co magnetic layer was formed on a μm PET.

Example 1 A can roll having a diameter of 20 cm was used.
Oxygen flow rate 41SCCM, electron gun power 35kW, line speed 8m / m
in.

Example 2 A magnetic layer was formed in the same manner as in Example 1 except that the oxygen flow rate during film formation was 58 SCCM.

Example 3 A can roll having a diameter of 15 cm was used.
Oxygen flow rate 37SCCM, electron gun power 41kW, line speed 7m / m
in.

Example 4 A magnetic layer was formed in the same manner as in Example 3 except that the oxygen flow rate during film formation was 23 SCCM.

Comparative Example 1 A can roll having a diameter of 60 cm was used.
Oxygen flow rate 63SCCM, electron gun power 48kW, line speed 7m / m
in.

Comparative Example 2 A can roll having a diameter of 20 cm was used.
Oxygen flow rate 51SCCM, electron gun power 29kW, line speed 3m / m
in.

Comparative Example 3 A can roll having a diameter of 20 cm was used.
Oxygen flow rate 57SCCM, electron gun power 48kW, line speed 8m / m
in.

Evaluation The thickness and the coercive force of the magnetic layers formed in the examples and comparative examples were measured. Table 1 shows the results.

A 10 nm thick protective layer and a 2 nm thick lubricating layer were formed on the magnetic layers of the tapes manufactured in Examples and Comparative Examples by a conventionally known method. Further, the magnetic tape was slit to a width of 6.35 mm. The reproduction output of these magnetic tapes was measured with a modified DVC camcorder. Table 1 shows the results. The output of each wavelength of Comparative Example 1 was used as a reference.

Further, the Auger profiles of the magnetic layers of the tapes manufactured in Examples and Comparative Examples were measured. The results are shown in FIGS. Note that the film thickness was converted by a stylus type step meter.

[0029]

[Table 1]

[0030]

As is clear from Table 1, in the oblique vacuum evaporation method, using a can roll having a diameter of 15 to 30 cm,
By producing a magnetic layer having a thickness of 100 to 140 nm, a magnetic recording medium having a high output, particularly a high output in a low frequency region, can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating an example of a vacuum evaporation apparatus suitable for manufacturing a magnetic recording medium of the present invention.

FIG. 2 is a view showing an Auger profile of a magnetic layer formed in Example 1.

FIG. 3 is a view showing an Auger profile of a magnetic layer formed in Example 2.

FIG. 4 is a view showing an Auger profile of a magnetic layer formed in Example 3.

FIG. 5 is a view showing an Auger profile of a magnetic layer formed in Example 4.

FIG. 6 is a view showing an Auger profile of a magnetic layer formed in Comparative Example 1.

[Explanation of symbols]

 11 Vacuum evaporation equipment 13 Can roll 14 Support

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Osamu Yoshida 2606 Kabane-cho, Akaga-cho, Haga-gun, Tochigi Prefecture, Japan Kao Co., Ltd. 72) Inventor Katsumi Endo 2606 Akabane, Kakaicho, Haga-gun, Tochigi Pref.

Claims (5)

[Claims] 1. A method for producing a magnetic recording medium using an oblique vapor deposition apparatus having a can roll, wherein the diameter of the can roll is 15 to 30 cm, and the film to be produced has a film thickness of 10 to 10.
A method for manufacturing a magnetic recording medium, comprising a magnetic layer having a thickness of 0 to 140 nm. 2. The magnetic recording medium manufactured by the method according to claim 1, wherein the magnetic layer has a coercive force of 1000 to 1450 Oe. 3. The curvature ratio of a column forming a magnetic layer is 8 to 8.
The magnetic recording medium manufactured by the method according to claim 1, which is 20%. 4. The magnetic recording medium according to claim 2, wherein in the Auger profile of the magnetic layer, the atomic ratio Os of oxygen atoms on the surface layer side of the magnetic recording medium and the atomic ratio Ob of oxygen atoms on the support side show the following relationship. recoding media. Os / Ob ≧ 1.3 5. The Auger profile of the magnetic layer, wherein the ratio between the value Ol and Os at which the atomic ratio of oxygen atoms is lowest between the peak on the surface layer side and the peak on the support side shows the following relationship. 5. The magnetic recording medium according to claim 4. Os / Ol ≧ 2.0