JPH08129747A - Magnetic recording medium and production thereof - Google Patents

Abstract

PURPOSE: To form a protective film capable of ensuring satisfactory durability in spite of a small film thickness. CONSTITUTION: When a DLC film is formed as a protective film by a vacuum thin film forming technique on a nonmagnetic substrate 1 with a formed ferromagnetic metallic thin film, part of the interior of a reaction tube 6(or a reaction chamber) is divided into two or more chambers 6a, 6b and gaseous hydrocarbon and gaseous fluorocarbon are introduced into the chambers 6a, 6b, respectively, so that a hydrogen-rich DLC film is formed near the metallic thin film and a fluorine-rich DLC film is formed on the surface side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called metal magnetic thin film type magnetic recording medium having a ferromagnetic metal thin film as a magnetic layer on a non-magnetic support, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a magnetic powder material such as an oxide magnetic powder or an alloy magnetic powder is provided on a non-magnetic support and a vinyl chloride-vinyl acetate strong polymer, polyester resin, urethane resin, etc. A so-called coating type magnetic recording medium is widely used, which is produced by coating a magnetic coating material dispersed in an organic binder of 1 above and drying it.

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 on a non-magnetic support such as a polyimide film, has been proposed and attracts attention.

This metal magnetic thin film type magnetic recording medium is excellent in coercive force, squareness ratio and the like, and the thickness of the magnetic layer can be made extremely thin. Therefore, thickness loss during recording demagnetization and reproduction is extremely small and electromagnetic waves at short wavelengths are reduced. Not only is it excellent in conversion characteristics, but since it is not necessary to mix a binder, which is a non-magnetic material, in the magnetic layer, it has a number of advantages such that the packing density of the magnetic material can be increased. For this reason, it is considered that this metal magnetic thin film type magnetic recording medium becomes the mainstream of high density magnetic recording due to its superior magnetic characteristics.

In such a metal magnetic thin film type magnetic recording medium, when the magnetic layer of the magnetic recording medium is formed in order to further improve the electromagnetic conversion characteristics and obtain a larger output. In addition, so-called oblique vapor deposition, in which the magnetic layer is obliquely vapor-deposited, has been proposed and put into practical use. By the way, in this type of magnetic recording medium, when forming the magnetic layer, an oxygen gas is introduced at the time of vapor deposition to improve the magnetic characteristics, and the electromagnetic conversion characteristics suitable for high density magnetic recording are ensured, and Is covered with metal oxide to improve durability.

As an effective means for improving the durability, for example, a method of previously providing fine irregularities on the magnetic layer to reduce friction, a method of improving the film quality of the medium surface by applying a lubricant, a hard method Methods for providing a protective film and the like have been studied, and in particular, attention has been paid to forming a protective film using a diamond-like hard carbon (DLC) film.

[0007]

However, the diamond-like hard carbon film (hereinafter, abbreviated as DLC film) is directly formed on the ferromagnetic metal thin film made of Co alone or Co-Ni alloy as a protective film. In this case, in order to improve the obtained durability to a practical level, the thickness of the DLC film must be increased. For this reason, if the wavelength is further shortened along with higher density recording in the future, the output reduction due to the spacing loss cannot be ignored and becomes a serious problem.

Therefore, the present invention has been proposed in view of such circumstances, and when a DLC film is used as a protective film, it has sufficient durability even if the film thickness of the DLC film is reduced. It is an object of the present invention to provide a magnetic recording medium and a method for manufacturing the same that can ensure the above.

[0009]

Means for Solving the Problems As a result of earnest studies that the above-mentioned objects cannot be achieved, the present inventors partition a reaction tube or a reaction chamber when forming a DLC film used as a protective film. By continuously changing the gas composition of hydrocarbons and fluorocarbons to be introduced, a hydrogen-rich DLC film is formed on the magnetic layer side, and a fluorine-rich DL is formed on the surface side.
By forming the C film, it was found that durability was improved and good results were obtained, and the present invention was completed.

That is, the magnetic recording medium of the present invention is a magnetic recording medium in which a diamond-like hard carbon film is formed on a ferromagnetic metal thin film formed by a vacuum thin film forming technique on a non-magnetic support. A diamond-like hard carbon film containing a large amount of hydrogen is formed in the vicinity of the magnetic metal thin film,
It is characterized by having a structure in which a diamond-like hard carbon film containing a large amount of fluorine is formed near the surface.

In the method for manufacturing a magnetic recording medium of the present invention, a ferromagnetic metal thin film is formed on a non-magnetic support by a vacuum thin film forming technique, and then a diamond-like hard carbon film is formed on the ferromagnetic metal thin film. In the method for manufacturing a magnetic recording medium, when forming the diamond-like hard carbon film,
Partition a part of the reaction tube or reaction chamber into two or more chambers,
It is characterized in that a hydrocarbon gas and a fluorocarbon gas are introduced into each of these partitioned chambers.

In the present invention, a diamond-like hard carbon film is provided as a protective film on a ferromagnetic metal thin film formed as a magnetic layer on a non-magnetic support. In the Raman spectrum of carbon, a peak derived from a diamond structure and a peak derived from a graphite structure are observed, but the diamond-like hard carbon film referred to here is one in which a peak derived from the diamond structure exists. To tell.

As a method for forming this diamond-like hard carbon film, for example, a sputtering method, a CVD method or the like can be used. In the present invention, when forming the diamond-like hard carbon film, the reaction tube or a part of the reaction chamber is partitioned into two or more chambers, and a hydrocarbon gas and a fluorocarbon gas are introduced into the partitioned chambers, respectively. To do. Here, as the hydrocarbon gas, methane, ethane, toluene, propane, acetylene, butane, or the like can be used, and as the hydrogen fluoride gas, ethylene fluoride, ethane fluoride, octafluorocyclobutane, or freon 23 is used.
Etc. can be used.

As a result, a DLC film containing a large amount of hydrogen is formed on the ferromagnetic metal thin film side, and a DLC film containing a large amount of fluorine is formed near the surface. By controlling the contents of hydrogen and fluorine in the DLC film obtained by changing the composition of the introduced gas in this way, the durability can be improved. Here, it is preferable that the hydrogen and fluorine contents continuously change in the thickness direction of the protective film. As a result, the strength of the film itself is improved, and sufficient durability can be secured even if the film thickness is thin.

In forming the diamond-like hard carbon film, an organic silicon compound (silicone) gas such as hexamethyldisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane or an organic silicon fluoride gas is introduced. May be. Thereby, silicon is taken into the obtained diamond-like hard carbon film, and a more remarkable effect can be expected.

The magnetic recording medium to which the present invention is applied includes a so-called metal magnetic thin film type magnetic recording medium in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support by a vacuum thin film forming technique. . In the above-mentioned metal magnetic thin film type magnetic recording medium, the nonmagnetic support and the metal magnetic material forming the ferromagnetic metal thin film may be any of those conventionally used in this type of magnetic recording medium. It is not particularly limited.

As a specific example, the magnetic metal material is a ferromagnetic metal such as Fe, Co, or Ni, Fe--Co,
Co-O, Fe-Co-Ni, Fe-Cu, Co-C
u, Co-Au, Co-Pt, Mn-Bi, Mn-A
1, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co
Examples include ferromagnetic alloys such as —Cr, Co—Ni—Cr, and Fe—Co—Ni—Cr.

These may be a single layer film or a multilayer film. Further, between the non-magnetic support and the ferromagnetic metal thin film, or in the case of a multilayer film, an underlayer or an intermediate layer is provided to improve the adhesive force between the layers and control the coercive force. Is also good. Further, for example, the vicinity of the surface of the magnetic layer may be an oxide in order to improve the corrosion resistance.

As means for forming this ferromagnetic metal thin film, a vacuum vapor deposition method in which the above-mentioned metal magnetic material is heated and vaporized under vacuum to be deposited on the non-magnetic support, or vaporization of the metal magnetic material is discharged. Ion plating method,
Any so-called PVD technique such as a sputtering method in which atoms on the target surface are knocked out by argon ions generated by glow discharge in an atmosphere containing argon as a main component can be used.

Of course, the constitution of the magnetic recording medium to which the present invention is applied is not limited to this, and may be changed without departing from the scope of the present invention, for example, a back coat layer may be formed if necessary. There is no problem in forming the undercoat layer or forming various layers such as a lubricant layer on the non-magnetic support. In this case, as the non-magnetic pigment, the resin binder, the material contained in the lubricant layer, etc. contained in the back coat layer, any conventionally known materials can be used.

[0021]

When a DLC film is formed as a protective film on a ferromagnetic metal thin film formed by a vacuum thin film forming technique on a non-magnetic support, a reaction tube or a part of the reaction chamber is partitioned into two or more chambers. A hydrocarbon gas and a fluorocarbon gas are introduced into each of these partitioned chambers. As a result, the obtained protective film has a structure in which a large amount of hydrogen is contained on the ferromagnetic metal thin film side and a large amount of fluorine is contained near the surface. As a result, the hydrogen-rich DLC film is firmly attached to the ferromagnetic metal thin film, while on the other hand, near the surface, excellent lubricity is obtained due to the effect of fluorine, and the friction coefficient is reduced. Therefore, sufficient durability can be obtained.

[0022]

EXAMPLES The present invention will be described below with reference to specific examples, but it goes without saying that the present invention is not limited to these examples. First, the structure of the plasma CVD continuous film forming apparatus used in the step of forming the protective film when the magnetic tape of this example is manufactured will be described.

In this plasma CVD continuous film forming apparatus, as shown in FIG. 1, Co or Co--Ni is placed in a vacuum chamber 11 whose inside is kept at a predetermined vacuum degree by an exhaust system 12 attached to the head. A tape-shaped non-magnetic support (object to be processed) 1 in which a magnetic layer made of a film or the like is formed by an evaporation method or the like is rotated counterclockwise from a feed roll 4 that rotates at a constant speed in the counterclockwise direction in FIG. The winding rolls 5 are rotated in a constant direction, and the winding rolls 5 are sequentially run.

The non-magnetic support 1 is provided at a midpoint where the non-magnetic support 1 runs from the feed roll 4 side to the take-up roll 5 side so as to pull out the non-magnetic support 1 downward in FIG. A rotary support 3 having a diameter larger than that of each of the rolls 4 and 5 is provided so as to rotate at a constant speed in the clockwise direction in FIG. Further, guide rolls 2a and 2b are provided between the feed roll 4 and the rotary support 3, and between the rotary support 3 and the take-up roll 5, respectively. The non-magnetic support 1 running between the rotary support 3 and the winding roll 5 is appropriately tensioned while being smoothly run.

The feed roll 4, the take-up roll 5, and the rotary support 3 each have a cylindrical shape having a length substantially the same as the width of the non-magnetic support 1. Therefore, in this plasma CVD continuous film forming apparatus, the non-magnetic support 1 is sequentially fed from the feed roll 4, passes along the outer peripheral surface of the rotary support 3, and is further wound on the winding roll 5. It is designed to be rolled up.

On the other hand, in the vacuum chamber 11, a reaction tube 6 is provided below the rotary support 3, and a magnetic layer is formed on the surface when passing between the rotary support 3 and the reaction tube 6. A protective film is formed on the above-mentioned non-magnetic support 1. As the reaction tube 6, for example, a quartz tube Pyrex glass, plastic or the like can be used.

An accelerating electrode 10 for generating plasma is incorporated inside the reaction tube 6. The accelerating electrode 10 is preferably made of a material having a high flexibility, capable of easily transmitting a gas, uniformly applying an electric field, and a metal mesh such as a wire mesh, for example, is suitable. As a constituent material of such an accelerating electrode 10, for example, copper or the like is representative, but in terms of conductivity, for example, gold or the like can also be used.

A DC power supply 13 arranged outside the vacuum chamber 11 is connected to the acceleration electrode 10, and a voltage higher than the substrate potential is supplied by the DC power supply 13. The voltage applied to this acceleration electrode 10 is +5.
It is preferably from 00V to 2000V. A partition plate 7 is arranged in the reaction tube 6, and the partition plate 7 partitions the interior into two chambers 6a and 6b.

A hydrocarbon gas introduction port 8 and a fluorocarbon gas introduction port 9 are formed in the two chambers 6a and 6b which are partitioned from each other. The hydrocarbon gas inlet 8 and the fluorocarbon gas inlet 9 are provided in the vacuum chamber 11 described above.
Of the two chambers 6a and 6b partitioned by the hydrocarbon gas introduction port 8 and the fluorocarbon gas introduction port 9 respectively. It is introduced and controlled to a predetermined atmosphere.

Thus, when a predetermined voltage is applied to the accelerating electrode 10 to perform plasma CVD to form a protective film, the protective film is fed out from the feed roll 4 and along the outer peripheral surface of the rotary support 3. A DLC film containing a large amount of hydrogen is formed on the magnetic layer on the non-magnetic support 1 when the running non-magnetic support 1 passes between the rotary support 3 and the partitioned chamber 6a. A DLC film containing a large amount of fluorine is formed on the DLC film containing a large amount of hydrogen when passing between the rotary support 3 and the partitioned chamber 6b. As a result, the magnetic layer and the DLC film containing a large amount of hydrogen firmly adhere to each other, while the DLC film containing a large amount of fluorine formed in the vicinity of the surface provides excellent lubricity and reduces the friction coefficient. Is planned. Therefore, good durability can be ensured.

Then, using the plasma CVD continuous film forming apparatus having such a structure, a magnetic tape was manufactured as follows. First, a diameter of 12 μm was formed on a non-magnetic support made of polyethylene terephthalate having a thickness of 10 μm.
After applying 0 angstrom silica fine particles at a rate of 12 particles / μm ² to form an undercoat layer, a ferromagnetic metal thin film made of Co is formed on the undercoat layer by a vacuum deposition method so that the film thickness becomes 0.15 μm. A magnetic layer composed of a single layer film was formed.

Then, using the plasma CVD continuous film forming apparatus shown in FIG. 1 (the rotating support has a diameter of 60 cm, and the reaction tube has a rectangular parallelepiped shape of 20 × 10 cm), the ferromagnetic metal is used. After mounting the non-magnetic support on which the thin film is formed on the above-mentioned feed roll, plasma CVD is performed under a predetermined condition to form a film having a thickness of 50 on the ferromagnetic metal thin film.
A diamond-like carbon film of Å was formed.

In carrying out this plasma CVD, toluene was introduced through the above-mentioned hydrocarbon gas inlet and fluorinated ethylene was introduced through the fluorocarbon gas inlet at a ratio of 4: 1. The pressure during the reaction was 0.1 Torr, a gold mesh was used as the accelerating electrode, and a DC voltage of 1.5 kV was applied to the accelerating electrode. Then, DLC containing fluorine on the surface of the ferromagnetic metal thin film is obtained by decomposing toluene and ethylene fluoride by such glow discharge.
A film was formed.

Then, fluorinated phosphazine (manufactured by Dow Chemical Co., Ltd.) was applied as a lubricant layer on the DLC film so as to have a film thickness of 20 Å, and this was cut into 8 mm width to form a sample tape. Obtained. The sample tape 1 produced as described above, and the comparative tape 1 produced in the same manner as in the above example except that toluene alone was introduced only through the hydrocarbon gas introduction port in the plasma CVD apparatus described above as a comparative example, and A mixed gas of toluene and fluorinated ethylene (4:
1) was introduced, and the others were manufactured in the same manner as in the above-mentioned example, and a commercially available 8 mm video deck (manufactured by Sony Corporation, trade name: CVD-1000) was used, and sendust having a gap length of 20 μm. Recording and reproduction were performed with the head so that the shortest recording wavelength was 0.5 μm.

Then, the sample tape 1 and the comparative tapes 1 and 2 were recorded 100 times in an environment of a temperature of 20 ° C. and a relative humidity of 60% and then reproduced to obtain the output value 100 times after the initial output value. The amount of deterioration was examined. As a result, in the present embodiment, the deterioration amount after repeated recording stopped within 1 dB. On the other hand, the comparative tape 1 deteriorated by 4 to 5 dB, and the comparative tape 2 deteriorated by 2 to 3 dB.

Further, when still reproduction was performed in the same environment, the time until the reproduction output decreased by 3 dB was stable for 2 hours or more for any 20 points in the present embodiment, whereas the comparison tape was used. In No. 1, there was a large variation of 5 to 20 minutes, and the time was short. Moreover, in the comparative tape 2, 30-
It was 60 minutes, and in any case, it did not reach this example.

Furthermore, when the friction coefficient of each tape was measured, it was 0.20 for sample tape 1, 0.30 for comparative tape 1, and 0.25 for comparative tape 2, and sample tape 1 is also superior. I understood. From this, the durability is insufficient only by forming the DLC film as a protective film, and a DLC film containing only fluorine cannot secure sufficient running property and durability, but the magnetic layer side does not contain hydrogen. By using a DLC film containing a large amount of fluorine and a DLC film containing a large amount of fluorine only near the surface,
It was found that good durability can be obtained even with a thin film thickness of about nm.

Next, under the same conditions as the sample tape 1, a sample tape 2 was prepared by using hexamethyldisiloxane instead of fluorinated ethylene. The deterioration amount of this sample tape 2 after repeated recording is within 1 dB, the time until the reproduction output is reduced by 3 dB in the still reproduction is 2 hours or more, and the friction coefficient is 0.18, which is a further improvement over the previous sample tape 1. Admitted.

As described above, as in this embodiment, the DLC
When forming a protective film consisting of a membrane, a part of the reaction tube (or reaction chamber) is partitioned, and in addition to introducing the hydrocarbon gas that is normally used as the introduction gas into one chamber, fluorocarbon By introducing the gas into the other chamber and continuously changing the composition of these introduced gases, it is possible to obtain a DLC film excellent in lubricity and firmly adhered to the magnetic layer, and the durability is improved. Can be achieved.

[0040]

As is apparent from the above description, in the present invention, when a DLC film is formed as a protective film on a non-magnetic support having a magnetic layer, a reaction tube or a part of the reaction chamber is partitioned. Then, a hydrocarbon gas and a fluorocarbon gas are introduced into each of these partitioned chambers so that the gas composition changes continuously, so that the obtained film becomes hydrogen-rich on the magnetic layer side, The structure is such that it becomes rich in fluorine in the vicinity. Therefore, it is possible to obtain a protective film that is hard and has excellent self-lubricating property, and it is possible to strengthen the adhesive force to the magnetic layer and improve the durability.

Therefore, according to the present invention, it is possible to provide a magnetic recording medium having good durability without impairing the high density recording characteristics.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a plasma CVD apparatus used in forming a diamond-like carbon film when a magnetic tape is manufactured by applying the present invention.

[Explanation of symbols]

 1 Non-magnetic Support (Processing Object) 3 Rotating Support 4 Feed Roll 5 Winding Roll 6 Reaction Tube 7 Partition Plate 8 Hydrocarbon Gas Inlet 9 Fluorocarbon Gas Inlet 10 Accelerating Electrode 11 Vacuum Tank 12 Exhaust System

Claims (5)

[Claims] 1. A magnetic recording medium in which a diamond-like hard carbon film is formed on a ferromagnetic metal thin film formed on a non-magnetic support by a vacuum thin film forming technique, wherein hydrogen is provided in the vicinity of the ferromagnetic metal thin film. A magnetic recording medium having a structure in which a diamond-like hard carbon film containing a large amount is formed and a diamond-like hard carbon film containing a large amount of fluorine is formed near the surface. 2. The magnetic recording medium according to claim 1, wherein the diamond-like hard carbon film has a structure in which the contents of hydrogen and fluorine continuously change in the thickness direction. 3. The magnetic recording medium according to claim 1, wherein the diamond-like hard carbon film contains silicon. 4. A method of manufacturing a magnetic recording medium, comprising forming a ferromagnetic metal thin film on a non-magnetic support by a vacuum thin film forming technique, and then forming a diamond-like hard carbon film on the ferromagnetic metal thin film. When forming a rigid carbon film, a part of the inside of the reaction tube or reaction chamber is partitioned into two or more chambers, and hydrocarbon gas and fluorocarbon gas are introduced into the partitioned chambers, respectively. Manufacturing method of magnetic recording medium. 5. When forming the diamond-like hard carbon film, an organic silicon compound gas or an organic silicon fluoride gas is introduced so that silicon is contained in the diamond-like hard carbon film. 4. The method for manufacturing a magnetic recording medium according to 4.