JPH11134632A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure an excellent electromagnetic conversion characteristic and to control the degradation of an output and the generation of noises. SOLUTION: A metal magnetic thin film, wherein a magnetization inverting ratio (b) in an external magnetic field (Hp/2) of a half strength of the external magnetic field (Hp) that shows the map. value (a) of the magnetization inverting ratio in an inverting magnetic field distribution measured in the inplane direction is set at <=40% of the maximum value (a), is formed on a non-magnetic support. Furthermore, a protective film is preferably formed on the matal magnetic thin film, and the protective film is preferably composed of carbon or any one of SiO2 , SiN, carbon nitride, ZrO2 , TiC, Al2 O3 , TiN.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic recording medium having a metal magnetic thin film formed on a non-magnetic support.
More specifically, the present invention relates to a magnetic recording medium having improved electromagnetic conversion characteristics by regulating the switching magnetic field distribution characteristics.

[0002]

2. Description of the Related Art Conventionally, magnetic recording media include ferromagnetic powders such as oxide magnetic powders and alloy magnetic powders and binders such as vinyl chloride-vinyl acetate copolymers, polyester resins, urethane resins and polyurethane resins. A so-called coating type magnetic recording medium in which a magnetic layer is formed by applying a magnetic paint composed of an organic solvent on a non-magnetic support, is widely used.

On the other hand, with the increasing demand for high-density recording, Co, Co-Ni alloy, Co-Cr alloy,
Metal terephthalate (PE) is prepared by plating a metal magnetic material such as Co-O or a vacuum thin film forming technique (vacuum deposition method, sputtering method, ion plating method, etc.).
T) A so-called metal magnetic thin film type magnetic recording medium, in which a magnetic layer is formed by directly applying a film on a non-magnetic support such as a film, polyethylene naphthalate (PEN) film, or aramid film, has been proposed and attracted attention. ing.

The magnetic recording medium of the metal magnetic thin film type has excellent magnetic properties such as coercive force and squareness ratio as compared with a coating type magnetic recording medium, and has excellent electromagnetic conversion characteristics in a short wavelength region. Since the thickness of the layer can be made extremely thin, the thickness loss during recording and reproduction is extremely small, and there is no need to mix a binder, which is a non-magnetic material, into the magnetic layer. It has a number of advantages, such as being able to increase the packing density of the material.

In such a magnetic recording medium, in order to further improve the electromagnetic conversion characteristics and to obtain a larger output, a so-called oblique evaporation in which the magnetic layer is obliquely evaporated at the time of forming the magnetic layer has been proposed. Therefore, such a magnetic recording medium has an excellent property that recording demagnetization is small, and it is easy to record with a ring head due to the structure of the magnetic layer.
For 8mm video tape recorders and digital video cassettes (Digital Video Cassette;
DVC).

Further, in such an obliquely deposited metal thin film type magnetic recording medium, the surface of the magnetic layer is close to a mirror surface and sticks easily to the magnetic head. The magnetic layer is provided with minute projections so that the projections are present on the surface of the magnetic layer, and the contact area with the magnetic head is reduced to ensure the durability of the magnetic layer. I try to ensure the nature.

However, in a digital video tape recorder, since the data transfer rate is increased along with the high recording density, the relative speed between the magnetic head and the magnetic recording medium is required to be at least twice that in the case of analog recording. It will be. In the case of a magnetic recording medium for business use,
Specifications that can cope with severe use conditions such as an edit mode are required. Therefore, in a magnetic recording medium used in the above-mentioned fields where the magnetic head rotates at a high speed, the magnetic recording medium is greatly damaged, and the durability of the magnetic recording medium such as running durability and still durability is improved. Some improvement is needed. For this reason, a technique for forming a protective film on the surface of the magnetic layer has been studied. Then, for example, a carbon protective film is formed as the protective film.

[0008]

By the way, in the magnetic recording medium of the metal magnetic thin film type as described above, the thickness of the carbon protective film is set to the minimum thickness which can ensure durability so as not to cause a spacing loss. Is common.

However, in the above-described metal magnetic thin film type magnetic recording medium, when forming the magnetic layer, oxygen gas is slightly introduced into the vacuum thin film forming apparatus in order to control the magnetic characteristics. Although slightly, C
An oxide layer made of an oxide such as o-O is formed.
This oxide layer improves durability in a magnetic recording medium having no protective layer such as a carbon protective film, but is not necessary in a magnetic recording medium having a carbon protective film as described above. Instead, it increases the spacing loss. Such spacing loss causes output deterioration of the magnetic recording medium of the metal magnetic thin film type and an increase in noise.

Further, the present inventors measured the reversal magnetic field distribution in order to investigate the detailed behavior of the metal magnetic thin film type magnetic recording medium, and found that a component (so-called low Hc component) whose magnetization was reversed at a low magnetic field was found. It was confirmed that there was a considerable amount. This low magnetic field reversal component causes partial re-reversal of magnetization by the magnetic field of the magnetic head after reversal in the magnetization transition region where the magnetic field of the magnetic head reverses, resulting in deterioration of electromagnetic conversion characteristics, output deterioration, and noise increase. I will invite you.
As a result of further studies by the present inventors, it has been found that such a phenomenon occurs when an oxide layer is present on the surface of the magnetic layer.

Accordingly, the present invention has been proposed in view of the above-mentioned circumstances, and a magnetic recording medium of a metal magnetic thin film type which has good electromagnetic conversion characteristics and suppresses output deterioration and noise generation. The purpose is to provide.

[0012]

In order to solve the above-mentioned problems, a magnetic recording medium according to the present invention is a magnetic recording medium in which a metal magnetic thin film is formed on a non-magnetic support. Wherein the magnetization reversal rate in a magnetic field having half the strength of the magnetic field where the magnetization reversal rate shows the maximum value in the reversal magnetic field distribution measured in the in-plane direction is 40% or less of the above-mentioned maximum value. It is.

In the magnetic recording medium of the present invention, it is preferable that a protective film is formed on the metal magnetic thin film, and the protective film is made of carbon, SiO ₂ , SiN, carbon nitride, ZrO ₂ , TiC, Al ₂ O. ₃ and TiN are preferably exemplified.

In the magnetic recording medium according to the present invention, the magnetization reversal distribution measured in the in-plane direction of the metal magnetic thin film formed on the nonmagnetic support has a magnetization reversal rate of half the strength of the magnetic field at which the magnetization reversal rate has the maximum value. The magnetization reversal rate in the magnetic field is set to 40% or less of the maximum value, and the low magnetic field reversal component is reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. Here, an example in which the present invention is applied to a magnetic tape will be described.

The magnetic recording medium according to the present invention comprises a metal magnetic thin film formed on a non-magnetic support, and has a maximum magnetization reversal rate in a switching magnetic field distribution measured in the in-plane direction of the metal magnetic thin film. The magnetization reversal rate in a magnetic field having a half strength of the magnetic field indicating the value is 40% or less of the maximum value.

As the non-magnetic support, those generally used in this type of magnetic recording medium may be used.
Examples include a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, and an aramid film.

The metal magnetic thin film may be made of Co, Co—Ni alloy, Co, which is generally used in this type of magnetic recording medium.
A metal magnetic material such as a -Cr alloy, Co-O or the like may be formed on the non-magnetic support by plating or a vacuum thin film forming technique (such as a vacuum deposition method, a sputtering method, or an ion plating method).

Further, in the magnetic recording medium of the present invention, it is preferable that a protective film is formed on the metal magnetic thin film.

The protective film is preferably made of carbon, particularly preferably of diamond-like carbon having relatively high hardness. The protective film is made of SiO ₂ , SiN, carbon nitride, ZrO.
Preferred are those composed of any one of ₂ , TiC, Al ₂ O ₃ , and TiN.

In the magnetic recording medium according to the present invention, as described above, the magnetic reversal distribution measured in the in-plane direction of the metal magnetic thin film has a magnetic reversal rate at which the magnetization reversal rate is half of the magnetic field at which the maximum value is obtained. The magnetization reversal rate is set to 40% or less of the maximum value.

The switching field distribution will be described. FIG.
Shows a hysteresis loop representing the relationship between the external magnetic field (Hex) and the magnetization (B). Usually, for example, a positive external magnetic field is gradually applied to a magnetic recording medium (for example, a metal thin film magnetic tape) magnetized in a negative direction. , The magnetization of the medium gradually reverses, and a sharp magnetization reversal is observed near the coercive force (Hc, here, about 100 (kA / m)).

The relationship between the magnitude of the external magnetic field applied at this time and the ratio of the magnetization reversal in the magnetic recording medium is shown by the reversal magnetic field distribution as shown in FIG.

[0024] In the hysteresis loop in FIG. 1, varying the external magnetic field from zero to X _1, and inverted part of the magnetization of the magnetic material of the magnetic recording medium, the residual magnetization state returning the external magnetic field to zero magnetization when compared with the magnetization when the external magnetic field zero, decreases by y _1. Subsequently, when the external magnetic field is increased from X ₁ to X ₂ , the magnetization of the magnetic material of the magnetic recording medium is further reversed, and the magnetization in the remanent magnetization state where the external magnetic field is returned to zero is the same as when the external magnetic field X ₁ compared to the magnetization, it decreased by y _2.

As described above, when the external magnetic field is changed from the minus direction to the plus direction, the magnetization in the residual state changes from the minus direction to the plus direction with a predetermined magnetization amount difference (magnitude change). To go. Here, the magnetization is-
Σy _n the magnetization amount difference when it began to change in Br from Br
(= 2Br) and then, the magnetization amount of the residual magnetization state when the external magnetic field is changed from X _n-1 to X _n and y _n, as shown in FIG. 2 that plots the magnetization with respect to the external magnetic field inverting It is a magnetic field distribution. The horizontal axis in FIG. 2 indicates the external magnetic field. On the other hand, the vertical axis indicates the ratio of each magnetization amount to the above-mentioned difference in magnetization amount. As can be seen from FIG. 2, the coercive force Hc (about 1
In the vicinity of 00 (kA / m)), the magnetization reversal rate becomes maximum.

Originally, the reversal magnetic field distribution should have a sharp distribution as shown in FIG. 3 in order to secure the steepness of the magnetic field reversal region of the magnetic recording medium and improve the recording / reproducing characteristics in the short wavelength region. preferable. However, generally, as shown in FIG. 2, the distribution of the magnetization reversal rate tends to be broad on the relatively low magnetic field side. The area A differs from the sharp distribution obtained by the calculation indicated by the hatched area in FIG. 2 when the information is recorded by using the inductive head. Means that a region which is easily inverted again exists in the magnetic recording medium.
That is, the presence of such a region prevents the steepness of the magnetization reversal region, thereby deteriorating the recording / reproducing characteristics in the short wavelength region.

Therefore, in the magnetic recording medium according to the present invention, the magnetization reversal rate in a magnetic field having a half strength of the magnetic field at which the magnetization reversal rate shows the maximum value is set to 40% or less of the above maximum value. . That is, as shown in FIG. 4, which shows the switching magnetic field distribution, the horizontal axis represents the external magnetic field, and the vertical axis represents the magnetization reversal rate, as shown in FIG. Hp (here, about 100 (kA /
m)) When the magnetization reversal rate in an external magnetic field Hp / 2 having half the strength of b) is b, b / a is a low magnetic field reversal rate R,
The above R is set to 40 (%) or less.

That is, in the magnetic recording medium according to the present invention, the distribution of the magnetization reversal rate on the relatively low magnetic field side is assumed to be sharp, and the difference from the sharp distribution obtained by the calculation shown by the shaded area in FIG. By narrowing the region A, the steepness of the magnetization reversal region is ensured, good electromagnetic conversion characteristics are ensured, output deterioration and noise are suppressed, and the recording / reproducing characteristics in the short wavelength region are improved. I have.

As described above, the region where reversal occurs on the relatively low magnetic field side is formed by the low magnetic field reversal component in the magnetic recording medium. As described above, the present inventors have studied and found that this low magnetic field reversal component is an oxide on the surface of a metal magnetic thin film that is a magnetic layer. Such an oxide has a small coercive force and is easily inverted again.

Therefore, in the magnetic recording medium according to the present invention, the above characteristics are ensured by reducing the low magnetic field reversal component. By doing so, when a protective film is formed, spacing loss is suppressed, and output deterioration and noise generation are further suppressed.

Next, a method of manufacturing a magnetic recording medium according to the present invention will be described. FIG. 5 shows a flowchart of a method for manufacturing a magnetic recording medium according to the present invention. First, for example, to prepare a non-magnetic support made of polyethylene terephthalate (PET), perform deposition in step S _1,
A magnetic layer made of a metal magnetic thin film is formed on a non-magnetic support. That is, for example, C
_{o x Ni 100-x (x} = 100~80, numerals content and represents a weight percent. of each element) incident angle of 45 ° while introducing oxygen metal magnetic thin film made of Co as a raw material It is formed to have a thickness of 0.2 (μm). This magnetic layer
It may be formed by performing oblique evaporation using a vacuum evaporation apparatus as shown in FIG.

As shown schematically in FIG. 6, the vacuum deposition apparatus includes a vacuum chamber 1 which is evacuated from exhaust ports 15 provided at the head and the bottom to make a vacuum state inside.
A feed roll 3 that rotates at a constant speed in the clockwise direction in the figure and a take-up roll 4 that rotates at a constant speed in the clockwise direction in the figure are provided. The magnetic support 2 runs sequentially.

A cooling can 5 having a diameter larger than the diameter of each of the rolls 3 and 4 is provided in the middle of the travel of the non-magnetic support 2 from the feed roll 3 to the take-up roll 4. I have. The cooling can 5 is provided so as to pull out the nonmagnetic support 2 downward in the drawing, and is configured to rotate at a constant speed in the clockwise direction in the drawing. The feed roll 3, the take-up roll 4, and the cooling can 5 each have a cylindrical shape having a length substantially equal to the width of the nonmagnetic support 2. Further, a cooling device (not shown) is provided in the cooling can 5 so that deformation and the like of the nonmagnetic support 2 due to a temperature rise can be suppressed.

Accordingly, the non-magnetic support 2 is sequentially sent out from the feed roll 3 as shown by an arrow M ₁ in FIG.
Further, it passes through the peripheral surface of the cooling can 5 and is wound up by the winding roll 4. In addition, guide rolls 6 and 7 are provided between the feed roll 3 and the cooling can 5 and between the cooling can 5 and the take-up roll 4, respectively. A predetermined tension is applied to the non-magnetic support 2 running from the cooling can 5 to the take-up roll 4 so that the non-magnetic support 2 runs smoothly. A crucible 8 is provided in the vacuum chamber 1 below the cooling can 5, and the crucible 8 is filled with a metal magnetic material 9. The crucible 8 has substantially the same width as the width of the cooling can 5 in the longitudinal direction.

On the other hand, an electron gun 10 for heating and evaporating the metallic magnetic material 9 filled in the crucible 8 is attached to the side wall of the vacuum chamber l. This electron gun 10
Is disposed at a position where an electron beam emitted from the electron gun 10 and indicated by an arrow X in the figure is irradiated on the metal magnetic material 9 in the crucible 8. Then, the metal magnetic material 9 evaporated by the electron gun 10 is formed as a magnetic layer on the non-magnetic support 2 running at a constant speed on the peripheral surface of the cooling can 5. The cooling can 5
A shutter 13 is provided between the crucible 8 and the vicinity of the cooling can 5. This shutter 13
The shutter 13 is formed so as to cover a predetermined area of the non-magnetic support body 2 running at a constant speed on the peripheral surface of the cooling can 5.
Thus, the evaporated metal magnetic material 9 is obliquely deposited on the nonmagnetic support 2 at a predetermined minimum incident angle. Furthermore, in such deposition,
Oxygen gas is supplied to the surface of the non-magnetic support 2 from the pump 17 through an oxygen gas inlet 12 provided through the side wall of the vacuum chamber 1 to improve magnetic properties, durability and weather resistance. Have been. The oxygen gas inlet 12 is provided such that its jet port opens between the shutter 13 and the peripheral surface of the cooling can 5.

Further, in this vacuum deposition apparatus, the inside of the vacuum chamber 1 is connected to the lower part where the crucible 8 is provided and the feed roll 3.
Plate 1 that divides into upper portions where winding roll 4 is provided
The cooling can 4 is provided at a position substantially at the same height as the rotation axis of the cooling can 5 so as not to impair the rotation of the cooling can.
Further, in this vacuum evaporation apparatus, a magnetic material supply box 1 for supplying a metal magnetic material 9 into a crucible 8 is provided.
1 is provided above the vacuum chamber 1 partitioned by the dividing plate 14, and a supply port 16 for supplying the metal magnetic material 9 to the crucible 8 through the dividing plate 14 is also provided.

When the magnetic layer is formed by oblique deposition while introducing oxygen in this way, a Co--O oxide is formed on the surface of the magnetic layer, although the thickness varies depending on the conditions. FIG. 7 schematically shows a composition profile from the surface of the magnetic layer. In FIG. 7, the horizontal axis indicates the thickness of the magnetic layer, and the zero point is the surface of the magnetic layer. In FIG. 7, the ordinate indicates the composition ratio, the solid line indicates the Co content, the dashed line indicates the O content, and the one-dot chain line indicates the C content. As can be seen from FIG. 7, a large amount of Co—O oxide exists on the surface side of the magnetic layer. Although this oxide functions as a protective film in a magnetic recording medium having a structure without a protective film,
When a protective film, particularly a protective film made of diamond-like carbon, is used, it is completely useless, and rather causes a spacing loss.

[0038] Therefore, in the magnetic recording medium according to the present invention, as shown in FIG. 5, in step S _2,
After the oxide is a surface side of the example Co-O magnetic layer is removed by etching, by sputtering to form a protective film, for example of diamond-like carbon in step S _3.

More specifically, the etching of Co—O oxide and the formation of the protective film made of diamond-like carbon may be performed in the same apparatus by using an apparatus schematically shown in FIG. . This device has substantially the same configuration as a sputtering device used for forming a protective film of this type of magnetic recording medium.

That is, the above-described device is provided with the exhaust ports 35 up and down.
Are arranged in a vacuum chamber 21 in which the inside is in a vacuum state, and a delivery roll 23, a take-up roll 24, a can roll 2
5, the delivery roll 23, the can roll 25,
The guide rolls 26,
27 are provided. Then, these feed rolls 23, the guide roll 26, can roll 25, guide roll 27, a non-magnetic support 22 on a take-up roll 24 is adapted sequentially to travel in the direction as shown by arrow M ₂ I have.

The can roll 25 is provided so as to draw out the non-magnetic support 22 wound around the feed roll 23 downward in the drawing, and has a diameter larger than the diameter of the feed roll 23 and the take-up roll 24. ing. The delivery roll 23, the take-up roll 24, and the can roll 25
Are each formed in a cylindrical shape having substantially the same width as the nonmagnetic support 22. The can roll 25 is provided with a cooling device (not shown) therein,
2 can suppress deformation due to temperature rise.

The guide rolls 26 and 27 are disposed between the feed roll 23 and the can roll 25 and between the can roll 25 and the take-up roll 24, respectively, and are provided above the can roll 25 in the drawing. ing. That is, the guide rolls 26 and 27 are
A predetermined tension is applied to the non-magnetic support 22 which is supplied to the can roll 25 from the can roll 25 and is wound on the take-up roll 24 from the can roll 25, and the non-magnetic support 22 reliably runs on the peripheral surface of the can roll 25. Is to do so.

In the above apparatus, a sputter electrode 30 is provided below the can roll 25, and a target 31 made of a thin film forming material such as carbon is disposed on the sputter electrode 30. Note that a gas introduction pipe 32 for introducing a gas is provided between the sputter electrode 30 and the can roll 25.

Therefore, if the target 31 is sputtered by the gas introduced from the gas introduction pipe 32, the non-magnetic support 22 running at a constant speed on the peripheral surface of the can roll 25 can be used.
A thin film forming material is deposited thereon and deposited as a film.

In this apparatus, a dividing plate 34 for dividing the inside of the vacuum chamber 41 into a lower portion where the sputter electrode 30 and the like are provided and an upper portion where the feed roll 23 and the take-up roll 24 are provided is provided with a rotating shaft of the can roll 25. The can rolls 25 are provided at substantially the same height so as not to impair the rotation of the can roll 25.

In this apparatus, in particular, an ion gun 36 using an argon gas as an ion source is provided so as to face the nonmagnetic support 22 running on the peripheral surface of the can roll 25. The ion gun 36 is provided in a region of the peripheral surface of the can roll 25 from when the nonmagnetic support 22 contacts the peripheral surface of the can roll 25 to when it faces the target 31. In the upper region of the region.

According to such an apparatus, the nonmagnetic support 22 having the magnetic layer, which is a metal magnetic thin film, formed on one main surface is sent out from the feed roll 23, and the oxide on the surface of the magnetic layer is removed by the ion gun 36. Immediately after the target 3
It is possible to form a protective film made of, for example, diamond-like carbon by sputtering 1. In this example, an argon gas is introduced into the apparatus at a variable gas pressure, the sputtering power is set to, for example, 6.8 (W / cm ² ), and a protective film having a thickness of, for example, 10 (nm) is formed. It was decided to. Further, in the above apparatus, the degree of removal of the oxide layer on the surface of the magnetic layer can be changed by changing the power of the ion gun.

Since the surface of a magnetic layer made of a metal magnetic film is oxidized when left in the air, the removal of oxide on the surface of the magnetic layer and the formation of a protective film are performed in the same apparatus as described above. Is preferred.

Although the method of etching and removing the oxide layer on the surface of the magnetic layer with an ion gun has been described here, the oxide layer on the surface of the magnetic layer may be removed by reactive etching. Furthermore,
The formation of the oxide layer on the surface of the magnetic layer during the formation of the magnetic layer may be suppressed so that the magnetic layer has the above characteristics. Specific methods include a method of changing the film quality by adjusting the atmosphere gas at the time of vapor deposition, a method of introducing vapor, a method of introducing oxygen, and a method of disposing a shutter.

Further, in the above-mentioned example, the example in which the protective film is formed by sputtering is described. However, a method generally used for forming a protective film of this type of magnetic recording medium such as CVD is used. Either is applicable.

Subsequently, as shown in FIG.
₄ , a back coat layer mainly made of carbon, for example, having a thickness of, for example, 0.5 (μm) is formed on the main surface of the nonmagnetic support opposite to the main surface on which the magnetic layer made of the metal magnetic thin film is formed.
To form a coating. Further, in step S _5, subjected to a rust-proofing protective layer surface and the surface of the protective film such as fluorine-based lubricant was applied in step S _6, to manufacture a magnetic recording medium. And, finally, cutting the magnetic recording medium produced in step S ₇ to a predetermined width (slit)
Then, a magnetic recording medium is completed.

[0052]

EXAMPLES Next, in order to confirm the effects of the present invention, the following experiments were conducted.

First, a non-magnetic support made of polyethylene terephthalate was prepared, and Co _x Ni _100-x (x = ₁₀₀ ) was formed on one main surface of the sample using a vapor deposition apparatus schematically shown in FIG. 10
The numbers from 0 to 80 represent the contents of each element in% by weight. ) Was formed by oblique evaporation while introducing oxygen from Co as a raw material.

As shown in FIG. 9, the vapor deposition apparatus has substantially the same configuration as that of the vapor deposition apparatus previously shown in FIG. 6, and parts having the same configuration have the same reference numerals as in FIG. And the description is omitted. However, also in this vapor deposition apparatus, oxygen gas is supplied from the pump 47 to the surface of the nonmagnetic support 2 via the oxygen gas inlet 42 provided through the side wall of the vacuum chamber 1. The introduction port 42 is provided so that the ejection port is opened not to a location between the shutter 13 and the peripheral surface of the cooling can 5 but to a location through which the vapor flow of the metal magnetic material 9 passes. By doing so, oxygen is satisfactorily mixed into the metal magnetic material 9 deposited on the non-magnetic support 2, and a surface oxide layer is less likely to be formed. As the metal magnetic material 9, Co was used, the incident angle was 45 °, and the deposition rate was 25 (m / m
In), a magnetic layer having a thickness of 0.2 (μm) was formed.

Subsequently, using the apparatus shown in FIG. 8, the oxide layer on the surface of the magnetic layer was removed and a protective film made of diamond-like carbon was formed. At this time, the gas pressure of the Ar gas is variable, and the power is 6.8 (W
/ Cm ² ) to form a protective film having a thickness of 10 (nm).

Further, a back coat layer mainly composed of carbon is formed by applying a coating having a thickness of 0.5 (μm), a rust-preventing treatment is performed on the surface of the protective film, and a fluorine-based lubricant is also applied.
The magnetic recording medium was completed by cutting to a predetermined width.

Next, a non-magnetic support made of polyethylene terephthalate was prepared, and Co _x Ni _100-x (x = ₁₀₀ ) was formed on one principal surface of the support using a vapor deposition apparatus as schematically shown in FIG.
The numbers from 100 to 80 represent the content of each element in% by weight. ) Was formed by oblique evaporation while introducing oxygen from Co as a raw material.

As shown in FIG.
It has substantially the same configuration as that of the vapor deposition apparatus shown in FIG. 6 earlier, and the portions having the same configuration are denoted by the same reference numerals as in FIG. 6, and the description will be omitted. However, also in this vapor deposition apparatus, oxygen gas is supplied from the pump 57 to the surface of the nonmagnetic support 2 through an oxygen gas inlet 52 provided through the side wall of the vacuum chamber 1. The inlet 52 is not located between the shutter 13 and the peripheral surface of the cooling can 5, but is provided at the tip 13 a of the shutter 13.
It is provided so as to open at a position lower by 10 (mm) or more below in the figure. In this way, the metal magnetic material 9 (here, C
The portion (particularly, the surface layer) where the coercive force decreases due to excessive oxidation of o) is hardly formed. Note that Co was used as the metal magnetic material 9, an incident angle was 45 °, a deposition rate was 25 (m / min), and a magnetic layer having a thickness of 0.2 (μm) was formed.

Subsequently, first, using the apparatus shown in FIG. 8, the oxide layer on the surface of the magnetic layer was removed, and a protective film made of diamond-like carbon was formed. At this time, the gas pressure of Ar gas is variable, the power is 6.8 (W / cm 2), and the thickness is
A protective film of 0 (nm) was formed.

Further, a back coat layer mainly composed of carbon was formed to a thickness of 0.5 (μm) in the same manner as in the sample 1, and the surface of the protective film was rust-proofed. The magnetic recording medium was completed by coating the sample with a predetermined width, and was cut into a predetermined width.

Next, a non-magnetic support made of polyethylene terephthalate was prepared, and Co _x Ni _100-x (x = 100 to 100) was formed on one main surface of the support using the vapor deposition apparatus shown in FIG.
80, the numbers represent the content of each element in% by weight. ) Was formed in the same manner as in Working Example 1 by oblique deposition while introducing oxygen from Co as a raw material.

Next, using the apparatus shown in FIG.
The oxide layer on the surface of the magnetic layer was removed, and a protective film made of diamond-like carbon was formed in the same manner as in Working Example 1. At this time, the ion gun 36 in FIG.
An oxide layer on the surface was removed using a gas in which CF ₄ gas was mixed at a ratio of 1: 1 as a reaction gas with the gas. further,
The sputtering power is set to 6.8 (W / cm ² ) using the target 31 in the same apparatus, and the thickness is set to 10 (nm).
Is formed.

Further, in the same manner as in the working sample 1, a back coat layer mainly composed of carbon was applied to a thickness of 0.5 (μm) to form a coating, and the surface of the protective film was subjected to rust prevention treatment. An agent was also applied and cut to a predetermined width to complete a magnetic recording medium.

Next, for comparison, a non-magnetic support made of polyethylene terephthalate was prepared, and Co _x Ni _100-x was formed on one main surface of the support using the vapor deposition apparatus shown in FIG.
(X = 100 to 80, the numbers represent the contents of the respective elements in weight%). A metal magnetic thin film was formed by oblique deposition while using Co as a raw material and introducing oxygen. Note that Co was used as the metal magnetic material 9, an incident angle was 45 °, a deposition rate was 25 (m / min), and a magnetic layer having a thickness of 0.2 (μm) was formed. The surface oxide layer at this time was 15 (nm).

Further, in the same manner as in Working Example 1, a back coat layer mainly composed of carbon was formed to a thickness of 0.5 (μm) by coating, and after performing a rust preventive treatment on the surface of the protective film, fluorine-based lubrication was performed. An agent was also applied and cut to a predetermined width to complete a magnetic recording medium. This magnetic recording medium was used as Comparative Sample 1.

Subsequently, for comparison, a non-magnetic support made of polyethylene terephthalate was prepared, and Co _x Ni _100-x was formed on one main surface of the support using the vapor deposition apparatus shown in FIG.
(X = 100 to 80, the numbers represent the contents of the respective elements in% by weight.) A metal magnetic thin film made of Co was used as a raw material and formed by oblique vapor deposition while introducing oxygen in the same manner as in Sample 1. did. In addition, as the metal magnetic material 9,
Co, the incident angle was 45 °, and the deposition rate was 25.
(M / min), a magnetic layer having a thickness of 0.2 (μm) was formed.

Next, a protective film made of diamond-like carbon was formed using a sputtering apparatus as schematically shown in FIG.

The sputtering apparatus shown in FIG. 11 has substantially the same configuration as the apparatus shown in FIG.
Portions having the same configuration are denoted by the same reference numerals, and description thereof will be omitted. That is, the sputtering apparatus shown in FIG. 11 has a configuration in which the ion gun 36 provided to face the nonmagnetic support 22 running on the peripheral surface of the can roll 25 is removed from the apparatus shown in FIG. The target 31 is sputtered, and a thin film forming material is deposited on a magnetic layer (not shown) on the non-magnetic support 22 that travels at a constant speed on the peripheral surface of the can roll 25, and is deposited as a film. . At this time, the gas pressure of the Ar gas is variable, and the sputtering power is 6.8 (W
/ Cm ² ) to form a protective film having a thickness of 10 (nm).

Further, a back coat layer mainly composed of carbon was formed to a thickness of 0.5 (μm) in the same manner as in Working Sample 1, and the surface of the protective film was subjected to rust prevention treatment. The magnetic recording medium was completed by coating and cutting to a predetermined width, and this magnetic recording medium was used as Comparative Sample 2.

Evaluation of Samples Next, the characteristics of the above-mentioned working samples 1 to 3 and comparative samples 1 and 2 were evaluated. Specifically, the thickness of the oxide layer on the surface of the magnetic layer of these samples was determined by Auger analysis (AES).
The magnetic properties, especially the reversal magnetic field distribution, were measured by a vibrating sample magnet (Vibrating Sample Magnet).
The conversion characteristics are measured by using a commercially available digital video (DV) video cassette recorder (VCR), and the electromagnetic conversion characteristics are measured using a dc-demagn.
It was measured as etization. Note that the electromagnetic conversion characteristics are relatively shown with the output of Comparative Sample 1 being zero (dB). Table 1 shows the results.

[0071]

[Table 1]

As can be seen from the results shown in Table 1, when the oxide layer on the surface of the magnetic layer is made thinner as in Examples 1 to 3,
It was confirmed that the low magnetic field reversal rate R as described above can be set to 40 (%) or less, and good electromagnetic conversion characteristics can be secured if the low magnetic field reversal rate R is set to 40 (%) or less. Was done.

That is, in the magnetic recording medium to which the present invention is applied, steepness of the magnetization reversal region is secured, good electromagnetic conversion characteristics are secured, output deterioration and noise are suppressed, and furthermore, in the short wavelength region. It was confirmed that the recording / reproducing characteristics were improved.

[0074]

As described above, in the magnetic recording medium according to the present invention, the magnetization reversal rate has the maximum value in the reversal magnetic field distribution measured in the in-plane direction of the metal magnetic thin film formed on the nonmagnetic support. The magnetization reversal rate in a magnetic field having half the strength of the indicated magnetic field is set to 40% or less of the maximum value, and the low magnetic field reversal component is reduced.

That is, the present invention can provide a magnetic recording medium of the metal magnetic thin film type in which good electromagnetic conversion characteristics are secured and output deterioration and generation of noise are suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hysteresis loop representing a relationship between an external magnetic field and magnetization.

FIG. 2 is a characteristic diagram illustrating an example of a switching magnetic field distribution.

FIG. 3 is a characteristic diagram showing another example of a switching magnetic field distribution.

FIG. 4 is a characteristic diagram showing still another example of the switching magnetic field distribution.

FIG. 5 is a flowchart of a method for manufacturing a magnetic recording medium according to the present invention.

FIG. 6 is a schematic cross-sectional view of an essential part schematically showing an example of a vacuum evaporation apparatus.

FIG. 7 is a schematic diagram showing a composition profile from the surface of a magnetic layer.

FIG. 8 is a schematic cross-sectional view of a main part schematically showing an apparatus for performing etching and forming a protective film.

FIG. 9 is a schematic cross-sectional view of main parts schematically showing another example of the vacuum evaporation apparatus.

FIG. 10 is a schematic cross-sectional view of a main part schematically showing still another example of the vacuum evaporation apparatus.

FIG. 11 is a schematic sectional view of a main part schematically showing a sputtering apparatus.

[Explanation of symbols]

1,21 vacuum chamber, 2,22 nonmagnetic support, 5 cooling can, 8 crucible, 9 metal magnetic material, 10 electron gun, 12,42,52 oxygen gas inlet, 25 can roll, 30 sputter electrode, 31 target , 32
Gas inlet tube, 36 ion gun

Claims (4)

[Claims] 1. A magnetic recording medium comprising a metal magnetic thin film formed on a non-magnetic support, wherein a magnetic field at which the magnetization reversal ratio has a maximum value in a magnetic field reversal distribution measured in an in-plane direction of the metal magnetic thin film. A magnetic recording medium characterized in that the magnetization reversal rate in a magnetic field having half the strength of the magnetic recording medium is 40% or less of the maximum value. 2. The magnetic recording medium according to claim 1, wherein a protective film is formed on said metal magnetic thin film. 3. The magnetic recording medium according to claim 2, wherein said protective film is made of carbon. 4. The magnetic recording medium according to claim ₂ , wherein said protective film is made of any one of SiO ₂ , SiN, carbon nitride, ZrO ₂ , TiC, Al ₂ O ₃ , and TiN.