JPH0836745A - Magnetic recording medium and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium which extremely excels in the electromagnetic conversion characteristic and also excels in reliability in durability, corrosion resistance and the like. CONSTITUTION:In the magnetic recording medium in which ferromagnetic metal thin films 13, 15 of at least two or more layers are formed on a non-magnetic supporting body 10 and further a protective layer 18 is formed on the ferromagnetic metal thin films, the protective layer 18 is a plasma-polymerized film which is formed by using a hydrocarbon gas and hydrogen gas as raw material, and it has such physical properties that the refractive index is 1.9 to 2.15 and the contact angle is less than 80 deg.. The ferromagnetic metal thin films 13, 15 contain 5at% or more of oxygen uniformly thoroughly in the direction of the thickness of the films, and the maximum oxygen concentration Tu of the ferromagnetic metal thin film of the uppermost layer is 10 to 30at%, and the maximum oxygen concentration To of the ferromagnetic metal thin film located thereunder is 15 to 50at%, and the ratio of Tu/To is not less than 0.3 and not more than 0.8.

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 provided with a multi-layered ferromagnetic metal thin film, and more particularly to a magnetic recording medium as a vapor-deposited video tape having excellent surface protection effect and electromagnetic conversion characteristics.

[0002]

2. Description of the Related Art Evaporation type video tape (magnetic recording medium)
Is suitable for high recording density because it has a high packing density of the magnetic material, unlike the coating type medium. Therefore, it is very advantageous in terms of electromagnetic conversion characteristics, and has already been put into practical use at present. However, since the vapor deposition type video tape has a structure in which a magnetic metal film is formed on the support,
Durability and corrosion resistance are insufficient and reliability is somewhat difficult, and various proposals have been made to solve this problem.

One of them is a proposal to form a plasma polymerization protective film on a ferromagnetic metal thin film (magnetic layer). That is, in JP-A-59-171028, JP-A-61-5426, and JP-A-1-205714, a plasma polymerized film as a protective film is formed on a ferromagnetic metal thin film. It has been proposed to form a thick oxide layer on the surface of a ferromagnetic metal thin film. However, in this case, although improvement in reliability can be expected,
The total spacing loss is the sum of the spacing loss of the thickness of the plasma polymerized film and the spacing loss of the metal oxide layer, which is extremely disadvantageous in terms of electromagnetic conversion characteristics.

On the other hand, Japanese Unexamined Patent Publication No. 63-34728 discloses that, contrary to the above-mentioned method, the surface of the magnetic metal layer is etched to forcibly remove the oxide layer. However, in this case, an extra surface treatment is required, which complicates the equipment, and if the surface oxide layer is completely removed by etching, the reliability is insufficient. .

From this point of view, the formation of the magnetic layer is generally performed so that the oxygen concentration on the surface of the magnetic layer in one layer is high and the oxygen concentration inside the magnetic layer is low (Japanese Patent Laid-Open No. Sho 60-60). No. 157717, Japanese Patent Publication No. 3-18246
No. That is, the oxygen concentration on the surface of the magnetic layer is increased to improve the reliability, while the inside of the magnetic layer is rich in metal components to improve the electromagnetic conversion characteristics.
A method of balancing mutually opposing phenomena (reliability is improved by increasing the oxygen concentration on the surface of the magnetic layer but is disadvantageous in terms of electromagnetic conversion characteristics) is generally taken. In addition, a rust preventive agent may be used (JP-A-58-189825), or perfluoropolyether (JP-A-56-872).
No. 36), a method for improving reliability has also been proposed.

[0006]

By the way, two or more ferromagnetic metal thin films (magnetic layers) are provided on a non-magnetic support, and the uppermost magnetic layer is suitable for recording at a high frequency of, for example, about 7 MHz. There is known a so-called multilayer magnetic layer type magnetic recording medium having a band and a recording band in a relatively low frequency region in the other deep part.

In this case, since the high frequency recording region is performed relatively near the surface of the magnetic layer, the structure and physical properties of the protective layer and the oxygen concentration on the surface of the magnetic layer depend on the electromagnetic conversion characteristics of the medium. It greatly affects reliability. for that reason,
It is not always preferable to use the conventionally known magnetic layer structure and protective layer structure as they are. Therefore, it is necessary to design the protective layer and the multi-layer magnetic layer in order to obtain an excellent surface protection effect, electromagnetic conversion characteristics and the like.

The present invention was created under such circumstances, and its purpose is to provide a magnetic recording medium having extremely excellent electromagnetic conversion characteristics and excellent reliability such as durability and corrosion resistance, and a method for manufacturing the same. To provide.

[0009]

[Means for Solving the Problems] In order to solve such an object, the inventors of the present application have earnestly studied, and as a result,
By setting a predetermined plasma polymerized film as a protective layer, and by designing a magnetic layer in consideration of the oxygen concentration in the multilayer magnetic layer, it was found that a medium having particularly excellent electromagnetic conversion characteristics and reliability can be obtained, This led to the present invention.

That is, the present invention provides a magnetic recording medium in which at least two ferromagnetic metal thin films are formed on a non-magnetic support, and a protective layer is further formed on the ferromagnetic metal thin film. The layer is a plasma-polymerized film formed from hydrocarbon gas and hydrogen gas as raw materials, and has physical properties of a refractive index of 1.9 to 2.15 and a contact angle of less than 80 degrees, and the ferromagnetic metal thin film is the film. 5 at% or more of oxygen is evenly distributed throughout the thickness direction, and the maximum oxygen concentration Tu of the uppermost ferromagnetic metal thin film is 10 to 30 at%, and the maximum oxygen of the ferromagnetic metal thin film located therebelow. Concentration To is 15 to 5
0 at% and Tu / To ratio of 0.3 or more and 0.8
It is constructed as follows.

[0011]

According to the present invention, since the predetermined plasma polymerized film is set as the protective layer and the magnetic layer is designed in consideration of the oxygen concentration in the multilayer magnetic layer, the electromagnetic conversion characteristics and the reliability are particularly improved. Excel.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the magnetic recording medium of the present invention will be described with reference to FIG. FIG. 1 is a sectional view of a magnetic recording medium of the present invention. According to this figure, the magnetic recording medium 1 of the present invention comprises a two-layered ferromagnetic metal thin film 1 on a non-magnetic support 10.
3 and 15 are sequentially formed, and a protective layer 18 is formed on the ferromagnetic metal thin film 15 on the upper side.

The non-magnetic support 10 has a flexible tape-like or sheet-like form, and its material is heat-resistant enough to withstand the formation of the ferromagnetic metal thin films 13 and 15. I wish I had it. Specifically, polyethylene terephthalate (PET), polyethylene naphthalate (P
EN), polyimide, aramid, polyetheretherketone (PEEK), polysulfone and the like. The thickness of the non-magnetic support 10 may be selected, for example, in consideration of the recording time of the magnetic recording medium, and is usually about 5 to 40 μm.

The ferromagnetic metal thin films 13 and 15 sequentially formed on the non-magnetic support 2 are preferably made of cobalt or cobalt alloy. As the cobalt alloy, Co-Ni, Co-Fe, Co-Ni-C
r, Co-Ni-B, Co-Cu, Co-Pt-Cr, etc. are illustrated. When these ferromagnetic metal thin films 13 and 15 are formed by vapor deposition, a metal having a melting point close to that of Co is deposited using the same crucible, that is, so-called unitary vapor deposition is performed, and a plurality of crucibles having different melting points are used. It is preferable to perform so-called multi-source vapor deposition.

In the vapor deposition process, the inside of the vapor deposition chamber is
For example, after evacuation to about 10 ⁻⁶ Torr, the metal is melted for vapor deposition with an electron gun, and vapor deposition is started when the entire metal is melted. Further, in order to control the magnetic characteristics of the ferromagnetic metal thin films 13 and 15 formed by vapor deposition, the film is usually formed while introducing an oxidizing gas such as oxygen, ozone, nitrous oxide or the like.

The ferromagnetic metal thin films 13 and 15 are
Each film has a predetermined oxygen concentration distribution in the thickness direction of the film, and FIG. 2 is presented to explain this easily. FIG. 2 shows the thickness direction of the medium on the horizontal axis.
From the left side of the drawing, a state in which the protective layer 18, the ferromagnetic metal thin film 15, the ferromagnetic metal thin film 13, and the nonmagnetic support 10 are laminated is shown. The vertical axis of FIG. 2 indicates the ferromagnetic metal thin films 13, 15
It shows the oxygen concentration (at% (atomic%)) in the inside, and the concrete distribution of the oxygen concentration (at%) is shown by the solid line. The distribution of this oxygen concentration (at%) is
Alternatively, it is obtained by measuring the oxygen concentration profile in the thickness direction while etching the medium in the thickness direction by ESCA.
By the way, assuming that the magnetic metal composition of the ferromagnetic metal thin films 13 and 15 is Co—Ni, oxygen concentration (at%) = O / (Co + Ni + O) × 1
00 is calculated.

It should be noted that one-dot chain points in the protective layer 18 region on the left side in FIG. 2 indicate the amount of carbon for reference, and do not indicate the oxygen concentration (at%).

The ferromagnetic metal thin films 13 and 15 of the present invention are evenly distributed at 5 at% throughout the thickness direction in the films.
It contains the above oxygen. That is, when the oxygen concentration profile in the ferromagnetic metal thin films 13 and 15 shown in FIG. 2 is taken, the minimum oxygen concentration value Tx of the profile is 5 at% or more, particularly preferably 8 to 15 at% oxygen is contained. ing. If this value is less than 5 at%, the coercive force (H
Inconvenience arises that c) decreases. On the other hand, if this value becomes too high (for example, exceeds 25 at%), the magnetic flux density will decrease, and the density density will not increase, and the output will decrease.

The maximum oxygen concentration Tu of the ferromagnetic metal thin film 15 of the uppermost layer is 10 to 30 at%, more preferably 1
It is set to 0 to 20 at%. And the maximum oxygen concentration To of the ferromagnetic metal thin film 13 located thereunder is 15 to 50 at.
%, And more preferably 25 to 35 at%. In addition, Tu / To, which is the value of these ratios, is set to 0.3 or more and 0.8 or less. If the maximum oxygen concentration Tu of the uppermost ferromagnetic metal thin film 15 exceeds 30 at%, the spacing loss increases and the output decreases, and if the Tu value is less than 10 at%, the reliability decreases. The inconvenience arises. Further, it is theoretically unrealistic that the maximum oxygen concentration To of the ferromagnetic metal thin film 13 located below this exceeds 50 at%, and when the To value becomes less than 15 at%, the interaction of the magnetic column develops and the magnetic field is reduced. The structure becomes unstable, the coercive force is reduced, and the output of high frequency components is reduced. Further, if the value of Tu / To exceeds 0.8, electromagnetic conversion characteristics deteriorate, and if the value of Tu / To is less than 0.3, reliability deteriorates.

The maximum oxygen concentration Tu in the uppermost ferromagnetic metal thin film 15 is preferably located at the uppermost portion of the ferromagnetic metal thin film 15, that is, near the interface with the protective layer 18. Further, the maximum oxygen concentration To of the ferromagnetic metal thin film 13 located therebelow is preferably located at the uppermost portion of the ferromagnetic metal thin film 13, that is, near the interface with the uppermost ferromagnetic metal thin film 15.

The oxygen concentration distribution in the ferromagnetic metal thin films 13 and 15 basically controls the amount (partial pressure) of oxidizing gas such as oxygen (O ₂ ) introduced during film formation. According to the present invention, a hydrogen gas, which is a reducing gas, is mixed in a raw material gas in a predetermined amount when the plasma polymerized film is formed, as will be described later. The gas enables the operation of lowering the oxygen concentration on the surface of the ferromagnetic metal thin film 15 at the same time when the plasma polymerized film is formed. Therefore, the desired Tu / To ratio can be obtained by forming the ferromagnetic metal thin films 13 and 15 under the same conditions without changing the film forming conditions and appropriately setting the plasma polymerization conditions. It is also a great merit in terms of process simplification.

Ferromagnetic metal thin film 1 thus formed
The thickness of the ferromagnetic metal thin film 15 of the uppermost layer is 5
The ferromagnetic metal thin film 13 located below this is set to about 500 to 2000Å.

In this embodiment, the case where the ferromagnetic metal thin film has two layers has been described as an example for easy understanding, but the present invention is not limited to this.
As a matter of course, the present invention can be suitably applied to the case of a multi-layer structure of three layers or more. In the case of a multi-layer structure of three or more layers, attention is paid to the uppermost ferromagnetic metal thin film and the ferromagnetic metal thin film located thereunder, and the film structure is set so as to satisfy the above conditions. .

A protective layer 18 is formed on the uppermost ferromagnetic metal thin film 15, and the protective layer 18 is a plasma-polymerized film formed from hydrocarbon gas and hydrogen gas as raw materials.

The plasma polymerized film used as the protective layer 18 in the present invention has physical properties of a refractive index of 1.9 to 2.15, more preferably 1.95 to 2.10. When this value exceeds 2.15, the magnetic head in sliding contact is damaged, and when this value is less than 1.9, the durability is not improved. Further, the plasma polymerized film used in the present invention has a contact angle of 8
It has physical properties of less than 0 degree. When this value is 80 degrees or more, there is a disadvantage that durability is lowered.

An example of the method for forming the plasma polymerized film will be described below. FIG. 3 shows a schematic front view of the plasma polymerized film forming apparatus. In this apparatus, the pay-out roll 51 has the ferromagnetic metal thin films 13, 1 on the non-magnetic support 10 in advance.
The laminated body original fabric 70 provided with 5 is wound. Then, as shown in FIG. 3, the laminate original fabric 70 fed from the feeding roll 51 moves along the rotary drum 55 via the guide roll 52, and further, the guide roll 56.
It is adapted to be taken up by the take-up roll 58 via. In this case, the rotary drum 55 is in contact with the back surface side of the non-magnetic support (the side on which the ferromagnetic metal thin film is not formed).

The inside of the vacuum chamber 37 is divided into upper and lower parts by, for example, partition plates 38 and 38 in order to secure a space necessary only for forming the plasma polymerized film, and a plurality of, for example, a plurality of discharge plates for generating an electric discharge. The rod-shaped plasma electrode 39 is disposed around the rotating drum 55 (downward in the drawing). In this case, the rotary drum 5
Reference numeral 5 constitutes one plasma electrode (ground side) that does not generate discharge. The plurality of plasma electrodes 39 have a so-called comb shape integrally connected at their bases.
A high frequency power source or the like is connected.

The formation of the plasma polymerized film is carried out by forming a monomer gas of an organic compound, for example, a hydrocarbon compound, into plasma in a vacuum chamber by high frequency and forming it on the surface of the ferromagnetic metal thin film 15 which is continuously conveyed. . Normally, the inside of the vacuum chamber for transporting the laminate original fabric 70 is 10 ^-5 T
After evacuation to or or higher, a predetermined amount of raw material gas is introduced.
This predetermined amount is generally set so that the reaction pressure is 1 to 10 ^-2 Torr.

In the present invention, the plasma polymerized film is formed by using the source gas containing the hydrocarbon gas and the hydrogen gas. The hydrogen gas not only affects the film characteristics of the plasma polymerized film, but also has the effect of lowering the oxygen concentration on the surface of the ferromagnetic metal thin film 15 at the same time as the formation of the plasma polymerized film as described above. The volume ratio of the flow rate of the hydrocarbon gas to the hydrogen gas is 1 to 5, preferably 2 to 3. If this value exceeds 5 times and the hydrocarbon gas becomes excessive, the denseness of the formed film is lacked and desired refractive index physical properties cannot be obtained. In some cases (though the absolute value of the amount of hydrogen gas is a problem), the merit in manufacturing that the oxygen concentration on the surface of the ferromagnetic metal thin film 15 is reduced disappears. Further, when this value is less than 1 and the hydrogen gas is excessive, the film formation rate is lowered and the refractive index which is a physical property of the film becomes too high.

As the hydrocarbon gas, methane, ethane,
Propane, butane, ethylene, propylene, acetylene, methylacetylene, toluene and the like are used alone or in combination.

The discharge power source for plasma formation is 50 k
The frequency is in the range of Hz to 450 kHz. Above all, frequencies in the range of 100 kHz to 400 kHz are particularly desirable. When the frequency is less than 50 kHz, it is difficult to operate for a long time, and the desired refractive index physical properties cannot be obtained.

Further, if the frequency exceeds 450 kHz, a dense film cannot be obtained, and further, the refractive index as a physical property of the film becomes too low, and the contact angle becomes too large.

The thickness of the plasma polymerized film thus formed is preferably about 80 to 150Å. If the thickness is less than 80Å, the film cannot be formed sufficiently and the characteristics cannot be measured. On the other hand, when it exceeds 150 Å, the spacing loss becomes large, which tends to be unsuitable for high density recording.

In the present invention, various known liquid lubricating layers may be coated on the protective film 18 made of a plasma polymerized film, in which case the durability characteristics are improved. Also,
A so-called various known back coat layer may be provided on the back surface of the non-magnetic support 10 (the surface opposite to the surface on which the ferromagnetic metal thin film is formed), or between the non-magnetic support 10 and the ferromagnetic metal thin film 13. Various intermediate layers may be provided.

In forming the plasma-polymerized film, in order to make the explanation simple and easy to understand, the laminate original fabric 70 in which the ferromagnetic metal thin films 13 and 15 are provided on the non-magnetic support 10 is fed out. Although the case of being pre-wound on the roll 51 has been described as an example, the present invention is not limited to this and, for example, as described in JP-A-4-95220, only the non-magnetic support is used as the pay-out roll. Needless to say, the method of manufacturing a magnetic recording medium of the present invention can be applied to a system in which the ferromagnetic metal thin film and the plasma polymerized film are sequentially formed in the same vacuum chamber.

The present invention will be described in more detail below by showing specific experimental examples relating to the present invention. (Production of Example Sample 1) First, in a vacuum chamber (evacuated to 10 ⁻⁶ Torr), a nonmagnetic support 10 of polyethylene terephthalate (PET) having a thickness of 6 μm.
Was continuously conveyed, and two layers of Co—Ni ferromagnetic metal thin films 13 and 15 were formed thereon. That is, Co-
Using an alloy of Ni (Co: Ni = 90: 10 (atm ratio)) as a vapor deposition source, oblique vapor deposition was performed at an incident angle of 30 ° (oxygen partial pressure 10 ⁻⁴ Torr), and a thickness of 0.15 μm of Co—Ni
The ferromagnetic metal thin film 13 was formed. Then, using a similar cylindrical can, Co-Ni (Co: Ni = 90: 10 (at
(m ratio)) was used as a vapor deposition source to perform oblique vapor deposition at an incident angle of 30 ° (oxygen partial pressure 10 ⁻⁴ Torr), and the thickness was 0.1.
A Co—Ni ferromagnetic metal thin film 15 of 5 μm was laminated.

Next, using the apparatus shown in FIG. 3, a protective layer 18 made of a plasma polymerized film was formed on the ferromagnetic metal thin film 15.

That is, 20 SCCM of methane gas and 10 SC of hydrogen gas as hydrocarbons from the plasma raw material gas inlet port.
While introducing CM, plasma was generated under a vacuum of 0.05 Torr to form a protective film made of a plasma polymerized film.

In this case, the frequency of the plasma discharge power supply is
The plasma output was 100 kHz and the plasma output was 1 W / cm ² . The so-called plasma passage time for exposing the ferromagnetic metal thin film to the plasma atmosphere was set to 1 sec. After forming the plasma-polymerized film in this manner, slitting was performed to a width of 8 mm to fabricate Example Sample 1 (Production of Example Samples 2 to 5).
In forming the plasma polymerized film on the ferromagnetic metal thin film 15 made of Co—Ni, the plasma raw material gas of hydrocarbon is changed from methane to ethane (Example sample 2),
Ethylene (Example sample 3), propylene (Example sample 4), and acetylene (Example sample 5) were used, respectively.

Other than the above, Example samples 2 to 5 were prepared in the same manner as Example sample 1 above. (Production of Example Samples 6 to 9) Example Sample 1 above
In forming the plasma polymerized film on the ferromagnetic metal thin film 15 made of Co—Ni, the gas amount of methane gas introduced as a part of the plasma raw material gas is changed from 20 SCCM to 10 SCCM (Example sample 6), 30 SCCM / Min (Example sample 7), 40 SCCM (Example sample 8), 5
It was changed to 0 SCCM (Example sample 9).

Example samples 6 to 9 were produced in the same manner as the example sample 1 except the above. (Production of Example Samples 10 to 13) In the example sample 1 described above, the ferromagnetic metal thin film 15 made of Co-Ni is used.
When the plasma polymerized film is formed on the substrate, the frequency of the plasma discharge power source is changed from 100 kHz to 50 kHz (Example sample 10) and 200 kHz (Example sample 1).
1), 300 kHz (Example sample 12), 400 k
Hz (example sample 13).

Example samples 10 to 13 were prepared in the same manner as the example sample 1 except the above. (Production of Example Samples 14 to 17) In the example sample 1 above, the ferromagnetic metal thin film 15 made of Co—Ni was used.
When the plasma polymerized film is formed on the surface, the plasma passage time is changed from 1 sec to 100 msec (Example sample 14), 500 msec (Example sample 15), 5 s.
ec (Example sample 16) and 10 sec (Example sample 17), respectively. In the example samples 14 and 17, the To value was changed in advance by changing the supply amount of oxygen gas when the ferromagnetic metal thin film was formed.

Example samples 14 to 17 were produced in the same manner as the example sample 1 except the above. (Production of Example Samples 18 to 20) In the example sample 1 above, the ferromagnetic metal thin film 15 made of Co—Ni is used.
When the plasma polymerized film was formed on the surface, the plasma output was changed from 1 W / cm ² to 4 W / cm ² (Example Sample 1
8) 2 W / cm ² (Example sample 19), 0.8 W
/ Cm ² (Example sample 20).
Further, the To value was changed in advance by changing the supply amount of oxygen gas when the ferromagnetic metal thin film was formed.

Example samples 18 to 20 were produced in the same manner as the example sample 1 except the above. (Preparation of Example Sample 21) In Example Sample 1 described above, the same ferromagnetic metal thin film as the ferromagnetic metal thin film 13 is further provided below the Co—Ni ferromagnetic metal thin films 13 and 15 having the two-layer structure. A ferromagnetic metal thin film having a three-layer structure was used.

Example sample 21 was prepared in the same manner as example sample 1 except for the above. (Preparation of Example Sample 22) When the ferromagnetic metal thin film was formed, the supply amount of oxygen gas was changed to change the Tu and To values. Except for this, the example sample 22 was manufactured in the same manner as the example sample 1 described above.

(Preparation of Example Sample 23) The Tx value was changed by changing the supply amount of oxygen gas when the ferromagnetic metal thin film was formed. Except for this, the example sample 23 was manufactured in the same manner as the example sample 1 described above. (Production of Comparative Example Samples 1 and 2) Above Example Sample 1
In forming the plasma polymerized film on the ferromagnetic metal thin film 15 made of Co—Ni, the amount of methane gas introduced as a part of the plasma raw material gas is changed from 20 SCCM to 5 SCCM (Comparative sample 1), 60 SCCM ( Comparative sample 2) was used instead.

Other than the above, Comparative Samples 1 and 2 were prepared in the same manner as in Example Sample 1 above. (Preparation of Comparative Example Samples 3 to 6) Above Example Sample 1
In forming the plasma polymerized film on the ferromagnetic metal thin film 15 made of Co—Ni, the frequency of the plasma discharge power supply was changed from 100 kHz to 20 kHz (Comparative sample 3), 500 kHz (Comparative sample 4), 1M.
Hz (Comparative sample 5) and 13.56 MHz (Comparative sample 6), respectively.

Other than the above, Comparative Samples 3 to 6 were prepared in the same manner as in the above Example Sample 1. (Production of Comparative Example Samples 7 to 9) The above-described example sample 1
In forming the plasma polymerized film on the ferromagnetic metal thin film 15 made of Co—Ni, the plasma passage time was changed from 1 sec to 0.5 msec (Comparative sample 7), 15 sec (Comparative sample 8), 50 msec.
(Example sample 9).

Other than the above, Comparative Samples 7 to 9 were prepared in the same manner as in Example Sample 1 above. (Preparation of Comparative Samples 10 and 11) In the above-described sample 1 of the example, the ferromagnetic metal thin film 15 made of Co—Ni was used.
When the plasma polymerized film was formed on the surface, the plasma output was changed from 1 W / cm ² to 6 W / cm ² (Comparative Example Sample 1
0) and 0.7 W / cm ² (Comparative sample 11).

Other than the above, Comparative Samples 10 and 11 were prepared in the same manner as in Example Sample 1 above. (Production of Comparative Example Sample 12) In the above-described Example Sample 1, the plasma polymerized film was not formed on the ferromagnetic metal thin film 15 made of Co—Ni.

A comparative sample 12 was prepared in the same manner as in the example sample 1 except for the above. (Production of Comparative Example Sample 13) In the above-described Example Sample 1, no plasma polymerized film was provided on the ferromagnetic metal thin film 15 made of Co—Ni. However, the surface of the ferromagnetic metal thin film 15 was reduced with hydrogen gas. A comparative example sample 13 was prepared in the same manner as the example sample 1 except the above. (Production of Comparative Example Sample 14) When the ferromagnetic metal thin film was formed, the amount of oxygen gas supplied was changed to change the values of Tu, To, and Tx (Table 3 below). A comparative example sample 14 was prepared in the same manner as the example sample 1 except the above. (Production of Comparative Example Sample 15) When the ferromagnetic metal thin film was formed, the amount of oxygen gas supplied was changed to change the values of Tu, To, and Tx (Table 3 below). A comparative sample 15 was manufactured in the same manner as the example sample 1 except the above.

Sample 1 of the above-mentioned embodiment manufactured in this manner
.About.23 and Comparative Examples 1 to 15 were subjected to the following measurements or evaluations.

As a preliminary experiment of the physical properties (refractive index) of the plasma polymerized film , a Si-wafer was adhered on a tape, a film was formed under the plasma conditions of the examples, and measured by an ellipsometer.

(Contact angle) A tape sample having a width of 8 mm was measured using a contact angle measuring device (contact angle measuring device manufactured by Kyowa Interface Science Co., Ltd.).

Oxygen Concentration in Ferromagnetic Metal Thin Films 13 and 15 While etching in the film thickness direction of the sample by Auger spectroscopy, an oxygen concentration profile in the film thickness direction of the ferromagnetic metal thin films 13 and 15 is created to obtain the minimum oxygen content. Concentration value Tx (at
%), And the maximum oxygen concentration Tu of the uppermost ferromagnetic metal thin film 15
(At%), and the maximum oxygen concentration To of the ferromagnetic metal thin film 13 located therebelow was determined.

Oxygen concentration (at%) = O / (Co + Ni +
It was calculated as O) × 100.

Initial friction Using a friction measuring device, the friction when the tape was passed by 1 pass was measured. That is, the tape loaded with 20 g through a predetermined rotating pin and fixed pin (made of SUS306, 3 mm diameter) is pulled up by a load cell (1 pa
ss), and the load applied to the load cell at that time was converted into friction (μ).

Endurance Friction Using the above-mentioned apparatus for measuring initial friction, 200 pass
Eye friction (μ) was measured.

The output is -5 dB using a Still Sony S1500 deck.
The time to reach was measured.

Electromagnetic conversion characteristics An output of 7 MHz was measured with an S1500 deck manufactured by Sony Corporation. Relative evaluation was performed by setting Comparative Example 12 to 0 dB.

Storage characteristics The amount of change in saturation magnetic flux density after storage for 1 week in an environment of 80 ° C. and 90% RH was measured.

Bm (%) = (Bb−Ba) / Bb × 100 Bb represents the saturation magnetic flux density before storage, and Ba represents the saturation magnetic flux density after storage.

The results are shown in Table 1, Table 2 and Table 3 below.
It was shown to.

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

[Table 3]

[0067]

The effects of the present invention are clear from the above results. That is, the present invention provides a magnetic recording medium in which at least two ferromagnetic metal thin films are formed on a non-magnetic support, and a protective layer is further formed on the ferromagnetic metal thin film. It is a plasma-polymerized film formed from hydrogen gas and hydrogen gas as raw materials, and has a refractive index of 1.9 to
2.15, having a contact angle of less than 80 degrees, the ferromagnetic metal thin film uniformly contains 5 at% or more of oxygen throughout the thickness direction of the film, and the ferromagnetic material of the uppermost layer is ferromagnetic. The maximum oxygen concentration Tu of the metal thin film is 10 to 30 at%, and the maximum oxygen concentration To of the ferromagnetic metal thin film located thereunder is 15 to 50
Since the composition is at% and the Tu / To ratio is 0.3 or more and 0.8 or less, the electromagnetic conversion characteristics are extremely excellent and the durability and corrosion resistance are also excellent. Play.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic recording medium of the present invention.

FIG. 2 is a diagram for explaining a predetermined oxygen concentration distribution existing in a thickness direction in a ferromagnetic metal thin film.

FIG. 3 is a schematic front view of a plasma polymerized film forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magnetic recording medium 10 ... Non-magnetic support body 13 ... Ferromagnetic metal thin film 15 ... Ferromagnetic metal thin film 18 ... Protective layer (plasma polymerization film)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jiro Yoshinari 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Koji Kobayashi 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Within the corporation

Claims (3)

[Claims] 1. A magnetic recording medium in which at least two or more ferromagnetic metal thin films are formed on a non-magnetic support, and a protective layer is further formed on the ferromagnetic metal thin film. A plasma-polymerized film formed from hydrogen gas and hydrogen gas as a raw material, and having a refractive index of 1.9 to 2.1.
5, having a contact angle of less than 80 degrees, the ferromagnetic metal thin film uniformly contains 5 at% or more of oxygen throughout the thickness direction of the film, and the maximum ferromagnetic metal thin film of the uppermost layer is included. The oxygen concentration Tu is 10 to 30 at%, and the maximum oxygen concentration To of the ferromagnetic metal thin film located thereunder is 15 to 30 at%.
50 at%, and the Tu / To ratio is 0.3 or more and not more than 0.1.
A magnetic recording medium characterized by being 8 or less. 2. The plasma polymerized film as the protective film,
A magnetic recording medium according to claim 1, wherein a mixture of a hydrocarbon gas and a hydrogen gas is used as a source gas, the flow rate ratio of the hydrocarbon gas to the hydrogen gas is set to 1 to 5, and the film is formed at a discharge frequency of 50 kHz to 450 kHz. Method. 3. The method of manufacturing a magnetic recording medium according to claim 2, wherein the ferromagnetic metal thin film is made of cobalt or an alloy containing cobalt as a main component and is formed by a vapor deposition method.