JPH0817050A - Magnetic recording media - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the sliding durability of a magnetic recording medium and enhance its reliability. A magnetic layer made of a metal magnetic thin film is formed on a non-magnetic support, a protective film made of silicon dioxide is formed on the magnetic layer, and the Vickers hardness of the protective film is 200 or more. The protective film made of silicon dioxide is preferably formed by depositing silicon in an oxygen atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having a protective film, and more particularly to a magnetic recording medium having improved sliding durability.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a powder magnetic material such as oxide magnetic powder or alloy magnetic powder is used as a vinyl chloride-vinyl acetate copolymer, polyester resin,
A coating-type magnetic recording medium prepared by coating a non-magnetic support with a magnetic coating material dispersed in an organic binder such as urethane resin or polyurethane resin and drying it is widely used.

On the other hand, with the increasing demand for high-density magnetic recording, Co--Ni alloys, Co--Cr alloys, Co
A metallic magnetic material such as —O is coated with a polyester film or polyamide by plating or a vacuum thin film forming means (vacuum deposition method, sputtering method, ion plating method, etc.).
A so-called metal magnetic thin film type magnetic recording medium, which is directly deposited as a magnetic layer on a non-magnetic support such as a polyimide film, has been proposed and attracted attention.

This metal magnetic thin film type magnetic recording medium is excellent not only in coercive force and squareness ratio but also in electromagnetic conversion characteristics at short wavelengths, and since the thickness of the magnetic layer can be made extremely thin, recording demagnetization and reproduction are required. Has a number of advantages such as a significantly small thickness loss and the fact that it is not necessary to mix a binder which is a non-magnetic material in the magnetic layer, so that the packing density of the magnetic material can be increased. That is, it is considered that the metal magnetic thin film type magnetic recording medium is the mainstream of magnetic recording media compatible with high density magnetic recording because of its superior magnetic characteristics.

In order to improve the electromagnetic conversion characteristics of this type of magnetic recording medium and to obtain a larger output, the magnetic layer is obliquely deposited when forming the magnetic layer of the magnetic recording medium. A magnetic recording medium that has been subjected to so-called oblique vapor deposition has been proposed and put into practical use.

[0006]

By the way, it is expected that a higher recording density will be required in the future. Therefore, the above magnetic recording medium tends to be smoothed to reduce spacing loss. However, as the magnetic recording medium is smoothed, the frictional force between the magnetic head and the magnetic recording medium increases, and the shear stress generated in the magnetic recording medium also increases. Therefore, in such a magnetic recording medium, formation of a protective film on the magnetic layer has been studied in order to improve sliding durability. The protective film may be a carbon film, a silicon dioxide film, a zirconia film, or the like. However, it is difficult to improve sliding durability simply by forming a protective film on the surface of the magnetic layer.

Therefore, the present invention has been proposed in view of the conventional circumstances, and provides a magnetic recording medium which is improved in sliding durability and is particularly applicable to a magnetic recording medium such as a magnetic tape. The purpose is to

[0008]

In order to achieve the above object, the magnetic recording medium of the present invention comprises a magnetic layer comprising a metal magnetic thin film formed on a non-magnetic support, and the magnetic layer is formed of silicon dioxide. Is formed, and the Vickers hardness of the protective film is 200 or more.

If the Vickers hardness of the protective film made of silicon dioxide is less than 200, it is difficult to obtain sufficient sliding durability.

As a method of forming the protective film of the magnetic recording medium as described above, a vapor deposition method, an ion plating method,
A thin film forming means such as a sputtering method or a CVD method can be used. When the protective film of the magnetic recording medium is formed by these thin film forming means, the Vickers hardness of the protective film made of silicon dioxide is set to 20 by selecting various conditions.
It can be 0 or more.

The vapor deposition method is a technique for forming a thin film by heating and evaporating a thin film forming material to deposit evaporated particles on a substrate. Examples of the method of heating and evaporating include resistance heating, high frequency heating, flash heating, electron beam heating and the like. Reactive vapor deposition is also possible by introducing a gas during vapor deposition to react with vapor deposited particles.

In the ion plating method, the thin film forming material or its component metal is heated in a low vacuum containing an inert gas such as argon or an active gas such as oxygen or nitrogen by resistance heating, high frequency heating, or heating by electron impact. Evaporate to
It is a technique for forming a thin film by ionizing by DC discharge, RF discharge, electron impact, etc. and accelerating by an electric field, and as it is or by reacting with an atmosphere active gas to deposit it on a substrate.

In the sputtering method, an inert gas such as argon is ionized (converted into plasma) by utilizing an electric field or a magnetic field to accelerate the ionized argon ions, and the kinetic energy thereof is used to form a target made of a thin film forming material. This is a technique for forming a thin film by ejecting atoms from the substrate and depositing the ejected atoms on the substrate. In particular, the RF sputtering method using an alternating electric field can form many kinds of thin films because both a metallic material and a non-metallic material can be used as a target material.

Further, in the CVD method, the energy of plasma generated by using an electric field or a magnetic field is used to cause a chemical reaction such as decomposition / bonding on the vaporized raw material in the vapor phase or on the substrate surface to form a thin film. It is a technology. Especially recently
Studies have also been made to form a diamond-like carbon (DLC) film, which is a harder carbon film, by the above CVD method.

Among the above-mentioned thin film forming means, the sputtering method and the CVD method have a disadvantage that the thin film forming rate is slower than the vapor deposition method and the ion plating method, and the productivity is not good. From this point of view, it is preferable to use a vapor deposition method or an ion plating method as the protective film forming means.

In the magnetic recording medium of the present invention,
It is preferable to form a protective film made of silicon dioxide by depositing silicon in an oxygen atmosphere.

[0017]

In the magnetic recording medium of the present invention, a magnetic layer made of a metal magnetic thin film is formed on a non-magnetic support, and a protective film made of silicon dioxide is formed on the magnetic layer, and the Vickers of the protective film is formed. Since the hardness is 200 or more, it has good sliding durability.

In the magnetic recording medium of the present invention, if the protective film made of silicon dioxide is formed by depositing silicon in an oxygen atmosphere, the productivity will be good.

[0019]

EXAMPLES Specific examples to which the present invention is applied will be described below based on experimental results. In this experimental example, a magnetic tape was used as a magnetic recording medium, and a protective film made of silicon dioxide of the magnetic tape was formed by an evaporation method, an ion plating method, and a sputtering method to manufacture a magnetic tape sample. The sliding durability of the magnetic tape sample and the occurrence of scan scratches were measured. The Vickers hardness of each protective film was also measured.

First, the vacuum vapor deposition apparatus used in this experimental example will be described with reference to the drawings. As shown in FIG. 1, this vacuum vapor deposition apparatus has delivery rolls 2 and take-up rolls 3 arranged on the upper and left sides of a vacuum chamber 1 whose inside is in a vacuum state, and a can roll 4 in the center of the vacuum chamber 1. Are arranged. It should be noted that exhaust ports 5a and 5b are provided above and below the vacuum chamber 1, and the interior of the vacuum chamber 1 is brought into a vacuum state by exhausting from there. Further, a guide roll 6 is arranged between the delivery roll 2 and the can roll 4, and a guide roll 7 is arranged between the can roll 4 and the winding roll 3.

The can roll 4 is a delivery roll 2
Flexible continuous substrate 8 having a magnetic layer wound around it
Is provided so as to be drawn downward in the figure, and has a diameter larger than the diameter of the delivery roll 2 and the winding roll 3. The delivery roll 2, the winding roll 3, and the can roll 4 each have a cylindrical shape having a width substantially the same as that of the flexible continuous substrate 8.
A temperature control device (not shown) is provided inside, and the temperature of the flexible continuous substrate 8 is arbitrarily controlled.

The guide rolls 6 and 7 are arranged between the feed roll 2 and the can roll 4 and between the can roll 4 and the take-up roll 3, respectively, and are provided above the can roll 4 in the figure. ing. That is, the guide rolls 6 and 7 are from the delivery roll 2 to the can roll 4
Is applied to the flexible continuous substrate 8 wound on the take-up roll 3 from the can roll 4 by applying a predetermined tension so that the flexible continuous substrate 8 reliably travels on the peripheral surface of the can roll 4. It is something to do.

Below the can roll 4, a crucible 9 is provided.
The crucible 9 is filled with a thin film forming material (not shown). The can roll 4 is located between the can roll 4 and the crucible 9 filled with the thin film forming material.
In the vicinity of, the shutter 10 is provided so as to be curved so as to face the peripheral surface of the can roll 4.

Further, an electron gun 11 is provided on the side wall portion outside the vacuum chamber 1. The electron gun 11 is the electron gun 1.
The thin film forming material filled in the crucible 9 is swept and irradiated with the electron beam X irradiated by the electron beam X in the figure, and the thin film forming material is irradiated by the electron beam X. Is capable of being heated and evaporated.

A gas introducing pipe 12 is arranged between the crucible 9 and the shutter 10, and a gas can be introduced through the gas introducing pipe 12 during vapor deposition.
The so-called reactive vapor deposition is possible, in which a thin film forming material that has been heated and vaporized reacts with a gas for vapor deposition.

In the vacuum vapor deposition apparatus constructed as described above, the flexible continuous substrate 8 wound around the delivery roll 2 is fed from the delivery roll 2 which rotates at a constant speed in the clockwise direction, for example, as indicated by an arrow M _{1 in the} figure. And is supplied to the can roll 4 that rotates at a constant speed in the clockwise direction, for example, while receiving a predetermined tension from the guide roll 6. Then, it is pulled up from the can roll 4 by the guide roll 7 while receiving a predetermined tension, and is wound around the winding roll 3 rotating in the clockwise direction at a constant speed in the direction of the arrow M ₁ in the drawing. .

The flexible continuous substrate 8 which is a non-magnetic material
Is vapor-deposited when passing through the peripheral surface of the can roll 4.

That is, in the vacuum chamber of FIG. 1, a crucible 9 filled with a thin film forming material is provided below the can roll 4 as described above, and the crucible 9 has the same width as the can roll 4. It consists of the width of. And
The thin film forming material with which the crucible 9 is filled is heated and evaporated by the electron beam X emitted from the electron gun 11 provided outside the vacuum chamber 1. At this time, the gas is introduced into the vacuum chamber from the gas introduction pipe 12. Therefore, the thin film forming material evaporated by the electron beam X reacts with the gas, and then adheres to the flexible continuous substrate 8 traveling at a constant speed on the peripheral surface of the can roll 4 to form a protective film. To be done.

At this time, since the shutter 10 is disposed so as to cover a predetermined region of the can roll 4, the thin film forming material is vapor-deposited within a predetermined angle range.

Next, the ion plating apparatus used in this experimental example will be described with reference to the drawings. This ion plating device has a configuration similar to that of the above-described vacuum vapor deposition device. That is, the delivery roll 22, the take-up roll 23, and the cooling can 24 are disposed in the vacuum chamber 21 in which the exhaust ports 25a and 25b are arranged above and below and the inside is in a vacuum state.
2, guide rolls 26 and 27 are arranged between the cooling can 24 and the winding roll 23, respectively. And
The flexible continuous substrate 28 sequentially runs on the feed roll 22, the guide roll 26, the cooling can 24, the guide roll 27, and the winding roll 23 in the direction indicated by the arrow M ₂ in the figure. .

A crucible 29 filled with a thin film forming material (not shown) is provided below the cooling can 24, and the cooling can 24 is provided between the cooling can 24 and the crucible 29 in the vicinity of the cooling can 24. A shutter 30 is arranged so as to be curved so as to face the surface.

Further, an electron gun 31 is provided on the side wall outside the vacuum chamber 21. A gas introduction pipe 32 is arranged between the crucible 29 and the shutter 30.

The shape, role, etc. of each of these constituent members are the same as those of the aforementioned vacuum vapor deposition apparatus.

In this ion plating apparatus, a coil 33 is provided between the crucible 29 filled with the thin film forming material and the shutter 30, and the coil 33 is provided with a high frequency power source 34 via a matching unit 35. It is connected.

When a high frequency (for example, 13.56 MHz) is introduced from the high frequency power source 34 into the coil 33 through the matching device 35, when the gas is introduced from the gas introduction pipe 32, the gas is excited and turned into plasma. . That is,
The thin film forming material heated and evaporated by the electron beam X shown by the broken line in the drawing of the electron gun 31 passes through the plasma, and a part of the vapor of the thin film forming material is ionized and the peripheral surface of the cooling can 24 is It is deposited on the flexible continuous substrate 28 that runs at a constant speed, and is deposited as a protective film. A DC bias voltage is applied to the flexible continuous substrate 28 running on the cooling can 24 from a bias electrode 36 connected to a DC power supply 37.

Next, the sputtering apparatus used in this experimental example will be described with reference to the drawings. This sputtering apparatus has a configuration substantially similar to that of the vacuum vapor deposition apparatus described above. That is, the exhaust port 45
Vacuum chamber 4 in which a and 45b are arranged and the inside is in a vacuum state
A delivery roll 42, a take-up roll 43, and a cooling can 44 are arranged in the unit 1, and guide rolls 46 and 47 are provided between the delivery roll 42, the cooling can 44, and the take-up roll 43, respectively. Then, the flexible continuous substrate 48 is sequentially run on the feed roll 42, the guide roll 46, the cooling can 44, the guide roll 47, and the winding roll 43 in the direction shown by the arrow M ₃ in the drawing. ing.

The shape and role of each of these constituent members are the same as those of the above-described vacuum vapor deposition apparatus.

In the sputtering apparatus, a sputter electrode 49 is provided below the cooling can 44, a target 51 made of a thin film forming material is arranged on the sputter electrode 49, and a high frequency wave is passed through a matching unit 55. The power supply 54 is connected. The cooling can 4
A shutter 50, which is curved and formed so as to face the peripheral surface of the cooling can 44, is provided near the cooling can 44 between the electrode 4 and the sputter electrode 49. Further, a gas introduction pipe 52 for introducing gas is arranged between the sputtering electrode 49 and the shutter 50.

Therefore, if the target 51 is sputtered by the gas introduced from the gas introduction pipe 52, the flexible continuous substrate 48 traveling at a constant speed on the peripheral surface of the cooling can 44.
A thin film-forming material is applied on top and is formed as a protective film.

Then, a protective film made of silicon dioxide of the magnetic tape was formed using the apparatus as described above to manufacture a magnetic tape sample. A sample for measuring the hardness of the protective film was also manufactured.

The above magnetic tape sample was manufactured as follows. That is, first, using the vacuum deposition apparatus shown in FIG. 1, a base film made of polyethylene terephthalate (PET) is used as the flexible continuous substrate 8, 28, 48, and a Co—Ni—O metal magnetic thin film is formed on the base film. Was formed.

The metal magnetic thin film is formed by electron gun power.
Is 30 kW and the degree of vacuum is 2 × 10 ^-2Pa, vapor deposition material
Reactivity with Co-Ni as the material and oxygen gas as the introduced gas
The film thickness was set to 200 nm by vapor deposition.

Next, a protective film made of silicon dioxide was formed on each of the magnetic layers made of the metal magnetic thin film by using each device to obtain a magnetic tape sample. That is, a magnetic tape sample was manufactured by using a base film having a magnetic layer formed thereon as the flexible continuous substrate 8, 28, 48 of each device and forming a protective film on the base film.

When the protective film is formed by a vacuum vapor deposition apparatus, the electron gun power is 5 kW and the degree of vacuum is 2 × 1.
The magnetic tape sample was manufactured as Example 1 at 0 ^-2 Pa, Si as the vapor deposition material, oxygen gas as the introduction gas, reactive substrate vapor deposition at a substrate temperature of 45 ° C, and a film thickness of 10 nm. . Further, a magnetic tape sample manufactured under the same conditions with the substrate temperature set to 20 ° C. using the same apparatus was set as Comparative Example 1.

When the protective film is formed by an ion plating apparatus, the electron gun power is 6 kW, the vacuum degree is 2 × 10 ^-2 Pa, the vapor deposition material is Si, the introduction gas is oxygen gas, and the high frequency is used. DC power with 100W
The bias voltage was set to −100 V, the protective film thickness was set to 10 nm, and the manufactured magnetic tape sample was used as Example 2.

When the protective film is formed by a sputtering apparatus, the degree of vacuum is 4.6 × 10 ^-1 Pa, the target is SiO ₂ , the sputter gas is argon gas, the high frequency power is 300 W, and the protective film is Thickness 10 nm
The manufactured magnetic tape sample is referred to as Example 3.

A sample for measuring the hardness of the protective film was manufactured as follows. That is, a Si substrate was attached on a base film made of PET, and a protective film similar to the protective film of the magnetic tape samples of Examples 1 to 3 and Comparative Example 1 was formed on the Si substrate with a film thickness of 100 nm to measure hardness. Was used as a sample.

Then, the sliding durability and the occurrence of scan scratches of the magnetic tape samples of Examples 1 to 3 and Comparative Example 1 were measured, and the hardness measurement samples having the same protective film as those of the magnetic tape samples were prepared. Vickers hardness was measured.

As for the sliding durability of the magnetic tape sample, a modified 8 mm video deck CVD-1000 (model name) manufactured by Sony Corporation was used, and the output was 3 d more than the initial output.
The number of times the magnetic head slid (the number of passes) when B was lowered was measured and evaluated. Further, the occurrence of scan scratches at this time was also measured. On the other hand, Vickers hardness is NEC MHA-
400 (model name) was used to measure the Vickers hardness when the indentation depth was 50 nm. The results are shown in Table 1. It should be noted that in Table 1, scan scratches are indicated by ○ when they are not generated at all, and Δ when they are slightly generated but do not cause any problems in practical use.
It was expressed by.

[0050]

[Table 1]

As is clear from the results shown in Table 1, a magnetic layer made of a metal magnetic thin film is formed on a non-magnetic support, and a protective film made of silicon dioxide is formed on the magnetic layer. In Examples 1 to 3 having a Vickers hardness of 200 or more, it was confirmed that sliding durability was good and high reliability could be obtained. It was also confirmed that sliding durability was significantly improved as compared with Comparative Example 1 in which the Vickers hardness of the protective film was less than 200.

In Example 1, although the sliding durability was good, scanning scratches were generated. But,
In Examples 2 and 3, the sliding durability is good and
There are no scan scratches. Therefore, it was confirmed that when the Vickers hardness of the protective film was 490 or more, the sliding durability was improved and the scan scratches did not occur.

Further, when the protective film made of silicon dioxide is formed by vapor-depositing silicon in an oxygen atmosphere as in Example 1, the productivity becomes good.

[0054]

As is apparent from the above description, in the magnetic recording medium of the present invention, a magnetic layer made of a metal magnetic thin film is formed on a non-magnetic support, and a protective layer made of silicon dioxide is formed on the magnetic layer. Since the film is formed and the Vickers hardness of the protective film is 200 or more, it has good sliding durability and high reliability.

In the magnetic recording medium of the present invention, if the protective film made of silicon dioxide is formed by vapor deposition of silicon in an oxygen atmosphere, the productivity will be good.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration example of a vacuum vapor deposition device.

FIG. 2 is a schematic diagram showing a configuration example of an ion plating device.

FIG. 3 is a schematic diagram showing a configuration example of a sputtering apparatus.

[Explanation of symbols]

 1,21,41 Vacuum chamber 2,22,42 Sending roll 3,23,43 Winding roll 4 Can roll 24,44 Cooling can 8,28,48 Flexible continuous substrate 9,29 Crucible 11,31 Electron gun 12 , 32, 42 Gas introduction tube 33 Coil 34, 54 High frequency power supply 35, 55 Matching device 49 Sputtering electrode 51 Target X electron beam

Claims (2)

[Claims] 1. A magnetic layer made of a metal magnetic thin film is formed on a non-magnetic support, and a protective film made of silicon dioxide is formed on the magnetic layer, and the Vickers hardness of the protective film is 200 or more. A magnetic recording medium characterized by the above. 2. The magnetic recording medium according to claim 1, wherein the protective film made of silicon dioxide is formed by depositing silicon in an oxygen atmosphere.