JPH10255262A - Manufacturing method of magnetic recording medium - Google Patents

Abstract

(57) [Problem] To provide a method for manufacturing a magnetic recording medium in which a carbon protective film is made thinner and durability is further improved. SOLUTION: A magnetic layer 3 formed on a non-magnetic support 2
A carbon protective film 4 is formed thereon, and a reaction gas containing at least nitrogen gas is ionized on the carbon protective film 4 and irradiated with an acceleration voltage of 40 kV to 100 kV.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a magnetic recording medium in which a carbon protective film is formed on a magnetic layer. More specifically, the present invention relates to a method for manufacturing a magnetic recording medium with improved durability.

[0002]

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

On the other hand, with the growing demand for high-density magnetic recording of information signals and the like, a non-magnetic support such as a polyester film or a polyamide-polyimide film is coated on a non-magnetic support.
A so-called metal magnetic thin film in which a metal magnetic material such as a Ni alloy, a Co-Cr alloy, or Co-O is directly applied by plating or a vacuum thin film forming method (for example, a vacuum evaporation method, a sputtering method, an ion plating method, etc.). Type magnetic recording media have been put to practical use. Metallic magnetic thin film type magnetic recording media have excellent coercive force, squareness ratio, etc., and excellent electromagnetic conversion characteristics at short wavelengths. There are many advantages, such as extremely small thickness loss at the time, and the fact that it is not necessary to mix a binder, which is a nonmagnetic material, in the magnetic layer, so that the packing density of the magnetic material can be increased.

In the above-described magnetic recording medium of the metal magnetic thin film type, when a magnetic layer is formed in order to improve the electromagnetic conversion characteristics and to obtain a larger output, the magnetic layer is obliquely formed. An oblique deposition method for vapor deposition on a substrate has been proposed and put to practical use.

In recent years, magnetic recording media of the metal magnetic thin film type have
As the technology shifts from analogization to digitalization, higher density is required as information recording means. Due to this demand for higher density, the magnetic recording medium of the metal magnetic thin film type tends to have a smooth surface in order to reduce spacing loss.

However, when the surface of the magnetic recording medium is smoothed, the frictional force between the head and the magnetic recording medium increases, so that the shear force generated on the magnetic recording medium also increases. Therefore, a magnetic recording medium of the metal magnetic thin film type
It is necessary to improve durability such as sliding durability under such severe conditions.

In view of the above, the formation of a protective film on a magnetic layer of a magnetic recording medium of the metal magnetic thin film type for the purpose of imparting durability has been studied and put to practical use.

As a protective film, a carbon film, quartz (Si
O ₂ ) films, zirconia (ZrO ₂ ) films and the like have been put to practical use. In particular, as a carbon film that has attracted attention, a diamond-like carbon film (hereinafter, DLC) which is a harder film is used.
It is called a film. ). The method of forming the DLC film is as follows.
A sputtering method, a chemical vapor deposition (hereinafter, referred to as a CVD method), or the like is used.

In the sputtering method, first, an inert gas such as Ar gas is ionized (plasmaized) using an electric field or a magnetic field. Next, the ionized Ar ions are accelerated, and the atoms of the target are repelled by their kinetic energy. Then, the ejected atoms are a physical process in which the atoms are deposited on an opposing substrate to form a film. This sputtering method is generally inferior in productivity from an industrial point of view because the film formation rate of the DLC film is generally slow.

On the other hand, in the CVD method, a chemical reaction such as decomposition or synthesis of a gas such as a hydrocarbon gas as a raw material is caused by utilizing the energy of plasma generated using an electric field or a magnetic field to form a film. It is a chemical process.

With the carbon protective film formed by these methods, the sliding durability of the magnetic recording medium of the metal magnetic thin film type is remarkably improved.

[0012]

However, in recent years,
Due to the demand for higher density magnetic recording, spacing loss due to the thickness of the carbon protective film has become a problem, and the carbon protective film itself has been made thinner. There is a need to ensure the quality.

Accordingly, the present invention has been proposed in view of such a conventional situation, and provides a magnetic recording medium capable of reducing the thickness of a carbon protective film and improving reproduction output and durability. The purpose is to:

[0014]

In order to achieve the above-mentioned object, a method of manufacturing a magnetic recording medium according to the present invention comprises forming a carbon protective film on a magnetic layer formed on a non-magnetic support, On the carbon protective film, a reaction gas containing at least nitrogen gas is ionized to increase the acceleration voltage from 40 kV to 10 kV.
The irradiation is performed at 0 kV.

Here, the carbon protective film has a thickness of 12 nm.
Preferably, it is formed to the following thickness. This carbon protective film is preferably formed by a CVD method.

According to the method for manufacturing a magnetic recording medium of the present invention as described above, the reaction gas containing at least nitrogen gas is ionized on the carbon protective film, and the acceleration voltage is reduced to 40 kV.
By irradiating with a voltage of V to 100 kV, a magnetic recording medium capable of reducing the thickness of the carbon protective film and improving the durability is manufactured.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a method for manufacturing a magnetic recording medium according to the present invention will be described in detail with reference to the drawings.

The magnetic recording medium of this embodiment is a metal magnetic thin film type magnetic recording medium 1 in which a magnetic layer 3 is formed on a non-magnetic support 2, as shown in FIG. In the magnetic recording medium 1 of the metal magnetic thin film type, after a carbon protective film 4 is formed on the magnetic layer 3, the carbon protective film 4 is irradiated with ions of a reaction gas containing at least nitrogen gas.

The nonmagnetic support 2 is made of, for example, polyesters such as polyethylene terephthalate, polyolefins such as polyethylene, cellulose derivatives such as cellulose triacetate and cellulose butyrate, and vinyl resins such as polyvinyl chloride and polyvinylidene chloride. In addition to polymer materials such as polyamides, light metals such as aluminum alloys and titanium alloys, and ceramics such as alumina glass can be used.

A plurality of fine surface projections may be formed on the surface of the non-magnetic support 2 on which the magnetic layer 3 is formed, for the purpose of controlling the surface. These surface protrusions are formed by a method in which a filler of a predetermined size is dispersed in a raw material (chip) of the nonmagnetic support 2 and the filler is fixed with a binder resin or the like. Examples of the filler include SiO ₂ particles and water-soluble latex.

When a rigid substrate such as an aluminum alloy plate or a glass plate is used for the nonmagnetic support 2,
An oxide film such as alumite treatment or a Ni-P film may be formed on the substrate surface to make the surface hard.

The magnetic material constituting the magnetic layer 3 is, for example, a ferromagnetic metal such as Fe, Co, or Ni;
o, Co-Ni, Fe-Co-Ni, Fe-Cu, Co
—Cu, Co—Au, Co—Pt, Mn—Bi, Mn—
Al, Fe-Cr, Co-Cr, Ni-Cr, Fe-C
o-Cr, Co-Ni-Cr, Fe-Co-Ni-Cr
And other ferromagnetic alloys. The magnetic layer 3 may be a single-layer film or a multilayer film.

The magnetic layer 3 may be formed by a vacuum evaporation method in which a ferromagnetic material is heated and evaporated under vacuum to deposit the ferromagnetic material on the nonmagnetic support 2, or an ion plating method in which the ferromagnetic metal material is evaporated during discharge. And a so-called physical vapor deposition method (hereinafter, referred to as a PVD method) such as a sputtering method in which glow discharge is caused in an atmosphere containing argon as a main component and atoms of the target surface are beaten by generated argon ions.

The carbon protective film 4 is not particularly limited, but a diamond-like carbon film (hereinafter, referred to as a DLC film) is preferable. In the Raman spectrum of carbon, a peak derived from a diamond structure and a peak derived from a graphite structure are observed, and a diamond-like carbon described later has a peak derived from a diamond structure among them. .

The carbon protective film 4 can be formed by ion-plating, in which the material is evaporated during discharge, or sputtering, in which glow discharge is caused in an atmosphere containing argon as a main component, and atoms on the target surface are struck by argon ions generated. PVD method, plasma CVD, arc jet CV
The film is formed by a CVD technique such as D. Here, the thickness of the carbon protective film 4 is preferably formed to be 12 nm or less.

Further, the surface of the carbon protective film 4 is ionized by using a reaction gas containing at least nitrogen gas as an ion source, and irradiated with the reaction gas ions. At this time, the acceleration voltage is desirably 40 kV to 100 kV.

Of course, the magnetic recording medium 1 according to the present invention
However, the present invention is not limited thereto, and may be modified without departing from the scope of the present invention. For example, a back coat layer may be formed on the main surface of the non-magnetic support 2 on the side opposite to the magnetic layer 3, An undercoat layer may be formed on the magnetic support 2, or a layer of a lubricant or the like may be formed. In this case, any conventionally known materials can be used as the material contained in the nonmagnetic pigment, the resin binder, or the lubricant contained in the back coat layer.

The magnetic recording medium 1 configured as above is
For example, it is manufactured by the CVD apparatus 5 shown in FIG. CV
As shown in FIG. 2, the D apparatus 5 includes a vacuum chamber 6 forming a closed internal space, and a vacuum chamber 6.
And a protective film forming unit disposed therein. The inside of the vacuum chamber 6 is brought into a high vacuum state by a vacuum exhaust system 7 provided at the head thereof.

The protective film forming unit comprises a vacuum chamber 6
A feed roll 8 for feeding a magnetic recording medium intermediate 1a having the magnetic layer 3 formed on the non-magnetic support 2 and a can 9 for running the magnetic recording medium intermediate 1a on the outer peripheral surface; A reaction tube 10 arranged near the outer periphery of the can 9 and serving as a means for forming the DLC film 5a on the surface of the magnetic recording medium intermediate 1a; and an ion irradiation chamber for irradiating the carbon protective film 4 with nitrogen ions. And a take-up roll 12 for winding the formed magnetic recording medium 1.

The can 9 is a magnetic recording medium intermediate 1 having the magnetic layer 3 formed on the non-magnetic support 2 on the side of the take-up roll 12 from the feed roll 8 in the vacuum chamber 6.
It is arranged in the middle of the travel of “a” and at a position facing the reaction tube 10 serving as the means for forming the carbon protective film 4. The can 9 is composed of a large-diameter, cylindrical roller body having a width slightly larger than the width of the nonmagnetic support 2, and is rotatably supported in the vacuum chamber 6.
The can 9 is driven by a driving source (not shown).
The magnetic recording medium intermediate 1a is rotated clockwise in the drawing so as to be pulled out downward in the drawing. In addition, the can 9 serves as the acceleration electrode 1 when the carbon protective film 4 is formed.
3 has a counter electrode (not shown).

The feed roll 8 and the take-up roll 12 are driven to rotate counterclockwise by a drive source (not shown) as shown in FIG. The feed roll 8 and the take-up roll 12 are driven to rotate in synchronization with the can 9. A magnetic recording medium intermediate 1 a in which the magnetic layer 3 is formed on the non-magnetic support 2 is wound around the feed roll 8 to form a roll. The winding roll 12 has the carbon protective film 4 formed thereon, and the magnetic recording medium 1 irradiated with nitrogen ions is wound.

As a material of the reaction tube 10, Pyrex glass, plastic, or the like is used. In addition, reaction tube 1
As the film-forming gas introduced into 0, a gas containing a hydrocarbon-based gas as a main component is preferably used.

One end of the reaction tube 10 is connected to a film-forming gas introduction tube 10a. The film forming gas introduction pipe 10a penetrates the bottom of the vacuum chamber 6.
Furthermore, the reaction tube 10 is arranged such that the other open end of the film formation gas introduction tube 10 a that is not connected faces the can 9. Here, the reaction tube 10 is configured such that a hydrocarbon-based film formation gas is introduced into the reaction tube 10 from a film formation gas introduction tube 10a.

An accelerating electrode 13 made of gold mesh or the like is attached to the inside of the reaction tube 10 in the vicinity of its opening, and the reaction tube 10 is disposed between the accelerating electrode 13 and a counter electrode (not shown) disposed on the can 9. Glow discharge occurs. The film-forming gas introduced into the reaction tube 10 is decomposed by the generated glow discharge, is deposited on the magnetic layer 3 of the magnetic recording medium intermediate 1a, and the carbon protective film 4 is formed. It becomes body 1b.

In this case, the can 9 is at the ground potential, and the potential generated between the accelerating electrode 13 and the counter electrode provided on the can 9 is preferably +500 to 2000 V.

The ion irradiation chamber 11 is connected at one end to an ion irradiation gas introduction pipe 11a. The ion irradiation gas introduction pipe 11a penetrates the side wall of the vacuum chamber 6. Further, the ion irradiation chamber 11 is arranged near the can 9 and the reaction tube 10 such that the other open end of the ion irradiation gas introduction tube 11 a that is not connected faces the can 9. Here, the ion irradiation chamber 11 is isolated from the reaction tube 10 by a partition wall 14, and the feed roll 8, the take-up roll 12,
It is isolated from the guide rolls 16 and 17 and a part of the can 9.

In the ion irradiation chamber 11, a reaction gas containing at least nitrogen gas is introduced into the ion irradiation chamber 11 from an ion irradiation gas introduction pipe 11a.
Then, the reaction gas is ionized under a high voltage, and is irradiated on the carbon protective film 4 of the magnetic recording medium intermediate 1b by an acceleration voltage.

Here, in particular, the acceleration voltage is 40 k
V to 100 kV is preferable.

Guide rolls 16 and 17 are arranged between the feed roll 8 and the take-up roll 12 and the can 9, respectively. The guide rolls 16 and 17 smoothly move by applying a predetermined tension to the magnetic recording medium intermediates 1 a and 1 b and the magnetic recording medium 1 traveling along the feed roll 8 along the can 9 and the can 9 along the take-up roll 12. It has been made to be.

The magnetic recording medium 1 may be in any form such as a tape, a sheet, a drum, etc., but the present invention is applied to a tape medium which is often damaged by a sliding member such as a guide. Then, the improvement in durability is remarkable.

In the CVD apparatus 5 configured as described above, first, the magnetic recording medium intermediate 1 a in which the magnetic layer 3 is formed on the non-magnetic support 2 is wound around the feed roll 8. Next, the magnetic recording medium intermediate 1a is sent out from the feed roll 8, and is pulled out by the can 9 via the guide roll 16. The magnetic recording medium intermediate 1 a travels around the outer periphery of the can 9, and the hydrocarbon-based film-forming gas introduced into the reaction tube 10 grows between the accelerating electrode 13 and the counter electrode of the can 9. The carbon protective film 4 is decomposed by the electric discharge and adheres on the magnetic layer 3 to form the carbon protective film 4, thereby forming the magnetic recording medium intermediate 1 b.

Further, the magnetic recording medium intermediate 1 b on which the carbon protective film 4 is formed travels around the outer periphery of the can 9, and the reaction gas containing at least nitrogen gas ionized by the high voltage in the ion irradiation chamber 11 is discharged. Then, the carbon protective film 4 is irradiated from the ion irradiation chamber 11.

The magnetic recording medium 1 in which the carbon protective film 4 is irradiated with ions of a reaction gas containing nitrogen gas,
It is wound up by the winding roll 12 via the guide roll 17.

[0044]

EXAMPLES Hereinafter, examples to which the present invention is applied will be described in detail based on specific experimental results.

Example 1 The vapor deposition tape used in this example was produced as follows. Here, the evaporation tape refers to a magnetic recording medium in which a magnetic layer is formed on a non-magnetic support by a vacuum evaporation method.

First, a polyethylene polyethylene terephthalate having a thickness of 10 mm was prepared as a nonmagnetic support. On this nonmagnetic support, Co80 / Ni20 (numerical values indicate% by weight) by a vacuum evaporation method under the following conditions.
Was formed as a single layer with a thickness of 200 nm to form a magnetic layer.

Incident angle of metal vapor: 45 to 90 ° Introduced gas: oxygen gas Vacuum degree during deposition: 2 × 10 ^-2 Pa Next, a carbon protective film was formed on the above magnetic layer under the following conditions.

Raw material gas: ethylene Reaction pressure: 20 Pa Introduced power: DC 1.0 kV Deposition rate: 100 nm / min Thickness of carbon protective film (DLC film): 4 nm Next, the following conditions were formed on the above carbon protective film. Then, nitrogen gas was ionized from the ion irradiation chamber and irradiated.

Acceleration voltage: 80 kV Ion dose: 1 × 10 ¹² N ₂ ⁺ ion / cm ² (1 ×
(10 ¹⁰ to 1 × 10 ²⁰ N ₂ ⁺ ions / cm ² are preferable) Tape speed: 1 m / min Then, as described above, after nitrogen gas is ionized and irradiated, an amine of fluorocarboxylic acid is further formed as a top coat layer. Salt (C ₅ F ₁₁ (CH ₂ ) ₁₀ COOH: N (C ₈ H
₁₇ ) The lubricant of ₃ ) was formed to a thickness of 3 nm by a wet coating method. This magnetic recording medium is
It was cut to a width of mm to produce a magnetic tape.

Example 2 Example 1 was repeated except that the thickness of the carbon protective film was changed to 6 nm.
A magnetic tape was produced in the same manner as described above.

Example 3 Example 1 was repeated except that the thickness of the carbon protective film was changed to 8 nm.
A magnetic tape was produced in the same manner as described above.

Example 4 A magnetic tape was produced in the same manner as in Example 1 except that the thickness of the carbon protective film was changed to 10 nm.

Example 5 A magnetic tape was produced in the same manner as in Example 1 except that the thickness of the carbon protective film was changed to 12 nm.

Example 6 A magnetic tape was produced in the same manner as in Example 1, except that the thickness of the carbon protective film was changed to 16 nm.

Example 7 A magnetic tape was produced in the same manner as in Example 1 except that the thickness of the carbon protective film was changed to 20 nm.

Example 8 A magnetic tape was produced in the same manner as in Example 1 except that the acceleration voltage for ionizing and irradiating nitrogen gas was set to 50 kV.

Example 9 A magnetic tape was produced in the same manner as in Example 1 except that the acceleration voltage for ionizing and irradiating nitrogen gas was 75 kV.

Example 10 The acceleration voltage for ionizing and irradiating nitrogen gas was 100 kV.
A magnetic tape was produced in the same manner as in Example 1 except that the above procedure was adopted.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1 except that a top coat layer was formed on a carbon protective film without irradiation with nitrogen gas ions.

Comparative Example 2 Comparative Example 1 was conducted except that the thickness of the carbon protective film was changed to 6 nm.
A magnetic tape was produced in the same manner as described above.

Comparative Example 3 Comparative Example 1 was conducted except that the thickness of the carbon protective film was changed to 8 nm.
A magnetic tape was produced in the same manner as described above.

Comparative Example 4 A magnetic tape was produced in the same manner as in Comparative Example 1 except that the thickness of the carbon protective film was changed to 10 nm.

Comparative Example 5 A magnetic tape was produced in the same manner as in Comparative Example 1 except that the thickness of the carbon protective film was changed to 12 nm.

Comparative Example 6 A magnetic tape was produced in the same manner as in Comparative Example 1, except that the thickness of the carbon protective film was changed to 16 nm.

Comparative Example 7 A magnetic tape was produced in the same manner as in Example 1, except that the acceleration voltage for ionizing and irradiating nitrogen gas was 25 kV.

Comparative Example 8 Acceleration voltage for ionizing and irradiating nitrogen gas was 125 kV
A magnetic tape was produced in the same manner as in Comparative Example 7, except that the above procedure was repeated.

COMPARATIVE EXAMPLE 9 The acceleration voltage for ionizing and irradiating nitrogen gas was 150 kV.
A magnetic tape was produced in the same manner as in Comparative Example 7, except that the above procedure was repeated.

With respect to the magnetic tapes of Examples 1 to 6 and Comparative Examples 1 to 6 manufactured as described above,
Still life, level down, and coefficient of friction were measured for durability evaluation.

<Still Life Characteristics> Using a modified 8 mm VTR so that the pause mode is not released, the
Under a condition of 10 ° C. and a humidity of 10%, the time until the reproduction output dropped by 3 dB was measured. However, it was terminated after 3 hours.

<Level down characteristics> 8 mm as described above
Using a VTR at room temperature 30 ° C. and humidity 10%,
The video signal is recorded on each 0-minute magnetic tape, and the
Repeated 00 times. Here, the first reproduction output is 0 dB.
And the 100th reproduction output was measured.

<Coefficient of friction> Diameter 3 mm, surface roughness 0.2
The surface of the magnetic layer of the magnetic tape is brought into contact with the stainless steel (SUS420J) column of S at 90 °, and the weight is 30
g, tape running speed 0.5 mm / sec, room temperature 3
It was obtained from the following equation under the conditions of 0 ° C. and 80% humidity.

Friction coefficient μk = (2 / π) · log (x / 30) Here, a measured load value was substituted for x.

Further, Embodiments 1, 3, 5 and
For Example 6 and Example 7, the reproduction output characteristics were measured.

<Reproduction Output Characteristics: C / N Value> A 7.6 MHz rectangular wave signal was recorded at the optimum recording current of each tape, and an output level of 7.6 MHz was detected by a spectrum analyzer. The relative speed between the tape and the head is
It was 3.8 m / sec. The difference between the noise at 6.6 MHz and the output level at 7.6 MHz is expressed by C /
N.

Next, Examples 8 to 10 and Comparative Example 7
About Comparative Example 9, as a durability evaluation, a friction coefficient and a still time were measured.

<Coefficient of friction> Diameter 3 mm, surface roughness 0.2
The surface of the magnetic layer of the magnetic tape is brought into contact with the stainless steel (SUS420J) column of S at 90 °, and the weight is 30
g, tape running speed 0.5 mm / sec, room temperature 4
It was determined from the following equation under the conditions of 5 ° C. and 80% humidity.

Coefficient of friction μk = (2 / π) · log (x / 30) Here, a measured load value was substituted for x.

<Still time> A still time was measured in a thermostat at room temperature, and the time required for the reproduction output to decrease to 3 dB was measured.

[0079]

[Table 1]

[0080]

[Table 2]

The above results are shown in Tables 1 and 2 and FIG.

As shown in Table 1, the still life of Examples 1 to 6 in which the carbon protective film was irradiated with nitrogen ions was higher than that of Comparative Examples 1 to 6 in which nitrogen ions were not irradiated. It was found that it was long, had little level down, and had a small coefficient of friction. From this, it was found that the durability of the magnetic tape was improved by irradiating the carbon protective film with nitrogen ions.

Then, the thickness of the carbon protective film was further examined.
In Examples 1, 3 and 5, which are not more than 10 nm, the carbon protective film has a larger C / N value than Examples 6 and 7 in which the carbon protective film is larger than 12 nm, and is excellent in reproduction output characteristics. all right. From this, it was found that the thickness of the carbon protective film was preferably 12 nm or less.

Further, when examining the accelerating voltage for irradiating nitrogen ions, as shown in FIG. 3, Examples 8 to 10 which fall within the range of dotted line A and dotted line B show Comparative Example 7 outside the above range. -It was found that the still time was longer, the friction coefficient was smaller, and the durability was better than that of Comparative Example 9. On the other hand, if the acceleration voltage is too high, the surface is roughened, the coefficient of friction increases, and as a result, the still time is significantly reduced. On the other hand, if the accelerating voltage is too low, nitrogen ions are not sufficiently irradiated, so that a thin carbon protective film alone cannot secure sufficient durability, so that the friction coefficient increases and the still time significantly decreases. . From this, it was found that the acceleration voltage for irradiating nitrogen ions is preferably 40 kV to 100 kV, which is within the range of dotted line A and dotted line B.

Therefore, the reaction gas containing nitrogen gas is ionized on the carbon protective film, and the acceleration voltage is increased from 40 kV to 1 kV.
By irradiating the carbon protective film at 00 kV, the carbon protective film can be made thinner and the durability can be improved.

[0086]

As described above in detail, according to the method of manufacturing a magnetic recording medium of the present invention, a carbon protective film is formed on a magnetic layer formed on a non-magnetic support, By ionizing a reactive gas containing at least nitrogen gas on the protective film and irradiating the protective gas at an acceleration voltage of 40 kV to 100 kV, it is possible to manufacture a magnetic recording medium with further improved durability.

Further, by making the carbon protective film 12 nm or less, the carbon protective film can be made thinner, and the reproduction output and durability can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a magnetic recording medium according to the present invention.

FIG. 2 is a schematic view showing an example of a CVD apparatus according to the present invention.

FIG. 3 is a diagram showing a relationship among an acceleration voltage of nitrogen ions, a still time, and a friction coefficient.

[Explanation of symbols]

1 magnetic recording medium, 2 non-magnetic support, 3 magnetic layer, 4
Carbon protective film, 5 CVD equipment, 11 ion irradiation chamber

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Seiichi Onodera 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (3)

[Claims] 1. A carbon protective film is formed on a magnetic layer formed on a nonmagnetic support, and a reaction gas containing at least nitrogen gas is ionized on the carbon protective film, and an acceleration voltage is increased from 40 kV to 100 k.
A method for producing a magnetic recording medium, wherein the irradiation is performed as V. 2. The method according to claim 1, wherein the carbon protective film is formed to a thickness of 12 nm or less. 3. The method according to claim 1, wherein the carbon protective film is formed by chemical vapor deposition.