JP2505587B2 - Magnetic recording medium and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thin film magnetic recording medium having a ferromagnetic thin film as a recording layer capable of high density magnetic recording, and more specifically, a thin film magnetic recording medium used as a flexible disk or a tape. A recording medium and its manufacturing method.

[Prior Art] In recent years, the above-mentioned thin film magnetic recording medium has attracted attention as a medium for high density magnetic recording, and many proposals have already been made. For example,
In Japanese Patent Laid-Open No. 54-147010, a Co-deposited film is used as a recording layer, and in Japanese Patent Publication No. 58-91 is a perpendicularly magnetized film made of a sputtered film of Co-Cr alloy as a recording layer. It is disclosed.

A thin film type magnetic recording medium having a ferromagnetic thin film formed by a thin film forming means such as vapor deposition, sputtering or ion plating as a recording layer shows a performance higher than that of a conventional coating type magnetic recording medium, and is practically used. Technology development is active.

In particular, high-definition tape, or high-density recording flexible disk, the recording density is higher 50Kfrpi, preferably practically at 100kfrpi (f lux r eversal p er i nch) than is expected. As a ferromagnetic thin film serving as a recording layer that responds to this gas, for example, a Co—Cr alloy-based perpendicular magnetic thin film or a Ni—Co alloy-based magnetic thin film having a thickness of 1 μm or less, specifically 0.1 to 0.2 μm has been proposed. [Applied Magnetics Society of Japan Vol.11, No.2, p.109, IEICE 70th Anniversary General Conference S3-4,1-239].

By the way, when the above-mentioned metal thin film is used as a recording layer,
It is known that the surface roughness of the substrate affects the spacing loss between the medium and the head, etc., as disclosed in Japanese Patent Application Laid-Open No. 58-14319, and greatly affects the reproduction output. And in the publication, the surface roughness of the substrate film is 0.0% in terms of average roughness (CLA).
It is disclosed that when the maximum projection height is 0.1 μm or less and the maximum protrusion height is 0.1 μm or less, a large reduction in reproduction output can be prevented.

Further, in the above-mentioned Japanese Patent Application Laid-Open No. 61-267921, the durability of the medium is greatly affected, and the durability can be improved by setting the surface roughness of the substrate to a ten-point average roughness Rz of 0.03 μm or less. Are disclosed to be improved.

That is, in the thin-film magnetic recording medium, the surface property of the substrate has a great influence on the surface property of the medium, and the recording / reproduction special
It is known that it is preferable that the surface of the substrate is smooth in terms of durability.

Therefore, when the manufacture of the magnetic recording medium was examined using the above-mentioned polymer film substrate having a smooth surface which is said to have sufficient durability, the following findings were obtained. That is, one of the problems is that a metal thin film such as a recording layer cannot be stably and continuously formed. For mass production, continuous production in which a thin polymer film substrate such as a recording layer is continuously formed by sputtering while transferring a long polymer film substrate by a roll is preferable. It was found that stable running and winding could not be ensured and continuous formation was difficult, probably because the slipperiness of the surface was lowered and it was affected by heat when forming the metal thin film of the recording layer. Secondly, when a metal thin film is formed, the surface property of the medium surface tends to be lower than that of the substrate due to the generation of oligomers, gases, etc. from the substrate, and the unevenness of the substrate causes a film formation on the film surface. It means that it tends to be expanded. Therefore,
It was found that a polymer film with a smoother surface should be used as the substrate.

[Object of the Invention] The present invention has been made in view of the above circumstances, and a thin film magnetic recording medium suitable for high density recording with improved surface properties that can be continuously produced by using a polymer film having a smooth surface and a method for manufacturing the same. The purpose is to provide.

[Structure / Operation of the Invention] The above-mentioned object is achieved by the present invention described below. That is, the present invention, in a magnetic recording medium having a recording layer consisting of a ferromagnetic thin film on a polymer film substrate, a carbon thin film having a thickness of 40 nm or less is provided on both surfaces of the polymer film substrate,
A first aspect of the present invention is a magnetic recording medium having a recording layer provided on at least one surface thereof, wherein in the method for producing a magnetic recording medium of the first aspect, the carbon thin film is perpendicular to a facing target. A method for manufacturing a magnetic recording medium is characterized in that a polymer film substrate is formed while continuously traveling by a facing target type sputtering method in which a magnetic field in a direction is applied to form a film on a substrate arranged side by side. It is an invention of No. 2.

The present invention described above has been made as follows. As a result of various studies on the film formation on the polymer film having a smooth surface described above, it was found that stable continuous film formation can be achieved if the film formation is performed at a temperature lower than the heat resistant temperature of the polymer film. Therefore, when we investigated an undercoat layer that can be continuously formed, when a carbon thin film can be stably produced continuously, and when it is provided as an undercoat layer,
Even in a vacuum of 0.1 to 1 Pa, the sliding property with the roll surface is improved, and even with the above-mentioned ultra-flat surface substrate that was difficult with the conventional technology, there is no generation of heat wrinkles due to sputtering of the recording layer etc. It has been found that stable film formation can be achieved.
Further, the carbon thin film is provided on both sides of the substrate to prevent generation of oligomers, gases, etc. from the substrate and prevent deterioration of the surface property of the medium, and when the film thickness exceeds 40 nm,
It has been found that the surface property of the medium deteriorates remarkably due to the roughening of the film surface as compared with the surface of the substrate, probably because of the expansion effect of the film. The present invention has been made based on such findings.

Therefore, the carbon thin film of the present invention, from the point of expressing on the medium surface without significantly reducing the surface property of the substrate,
The film is provided on both sides of the substrate, and its thickness is 40 nm or less, more preferably 30 nm or less. From the viewpoint of suppressing the generation of oligomers and gases, it is preferable that the film thickness is thicker than 1n.
It is preferably m or more, more preferably 5 nm or more. The carbon thin film can be formed by a PVD method such as a sputtering method or other known thin film forming means, but it is disclosed in Japanese Patent Publication No. 62-56575 and the like, and a vertical magnetic field is applied to the facing target to the side thereof. A method of forming a film on the arranged substrate by a facing target sputtering method is preferable in that stable production can be performed at a substrate temperature of 100 ° C. or lower. Above all, it is more preferable from the aspect of adjusting the film quality such as internal stress of the film obtained by the facing target type sputtering method provided with the reflection electrode for repelling electrons disclosed in JP-A-63-270461 and the utilization efficiency of the target.

Further, the polymer film substrate of the present invention is not particularly limited, but at least one surface thereof is a smooth surface having a surface roughness equal to or less than the surface roughness described in JP-A-58-14319 and JP-A-61-267921. Is preferred.

By the way, in the study by the present inventors, the surface property of the magnetic recording medium is 10 nm in the maximum roughness TIR described later and about 2 nm in the average roughness Ra from the surface roughness of the substrate due to the formation of the recording layer, the protective layer, etc. To do. In a high-density thin film magnetic recording medium such as a perpendicular magnetic recording medium, the allowable spacing is said to be about 50 nm at maximum, and if the thickness of the protective layer is about 20 to 30 nm,
From the above-mentioned point, the surface roughness of the substrate is particularly preferably 20 nm or less in maximum roughness TIR. More preferably, the average roughness Ra is 2 nm.
It is the following.

The maximum roughness TI that defines the surface roughness in the present invention
R and average roughness Ra are measured as follows. That is, it was calculated by measuring the surface of the measurement sample in an arbitrary width of 80 μm using a stylus surface roughness meter and calculating from the measured value as follows. The maximum roughness TIR is the difference between the maximum value and the minimum value of the measured values, and the average roughness Ra is the arithmetic average value of the measured values, which is equivalent to ANSI standard B46.1. The data of the present invention is measured by using a stylus type surface roughness meter with Alphastep 200 (alphastep 200) of Tencor Instruments of the United States of America (TENCOR INSTRUMENTS), and 12 arbitrary sections are measured for each sample. It is an average.

The material of the polymer film to be used is not particularly limited as long as it has heat resistance to withstand film formation such as a recording layer, and various known polymer films can be applied. Among them, polyethylene terephthalate (PET) film and polyethylene naphthalate (PEN) film are preferably applied in view of mechanical properties such as dimensional stability, surface properties, and cost.

Further, the magnetic recording medium of the present invention is not particularly limited as long as it is a thin film type magnetic recording medium having a recording layer made of a magnetic thin film, and all known ones such as the above NiCo alloy and CoCr alloy are applied.
In particular, it is preferably applied to a perpendicular magnetic recording medium having a film thickness of 1 μm or less, which is greatly influenced by the surface property of the substrate, and in particular, the influence of spacing is remarkable. The surface property of the obtained magnetic recording medium is preferably 30 nm or less in maximum roughness TIR and 5 nm or less in average roughness Ra in view of recording / reproducing characteristics and durability.

In the magnetic recording medium of the present invention, it is needless to say that there are no particular restrictions on the laminated structure of the recording layers, the formation of the protective layer, the formation of the intermediate layer, etc., and all known various aspects can be applied.

According to the present invention described above, since a magnetic recording medium having a very smooth surface with irregularities of about the thickness of the protective layer and a small spacing can be obtained by continuous production, thin-film magnetic recording excellent in durability and capable of high-density recording. The medium is realized at low cost. As described above, the present invention makes a great contribution to the industrialization of the perpendicular magnetic recording system even in a thin film magnetic recording medium which is expected to be put into practical use from the viewpoint of high density recording.

 Hereinafter, the details of the present invention will be described based on Examples.

FIG. 1 shows a facing target type sputtering apparatus used in the structure of the embodiment, which has the same structure as that disclosed in the above-mentioned JP-A-63-270461.

That is, in the figure, 10 is a vacuum tank, 20 is an exhaust system including a vacuum pump for exhausting the vacuum tank 10, 30 is a predetermined gas introduced into the vacuum tank 10, and the pressure in the vacuum tank 10 is adjusted to 10 ^-1 to 10 ^-4
This is a gas introduction system that is set to a predetermined gas pressure of about Torr.

In the vacuum chamber 10, a target portion is
A pair of rectangular targets T, T'having a long side facing the substrate S by 100, 100 'are arranged so as to face each other in parallel with a space.

The target parts 100 and 100 'have exactly the same configuration, and the following description will be given based on one of the targets 100.

As is clear from FIGS. 2 and 3, the target section 100 has a magnetic field generating means 120 for forming a plasma capturing magnetic field.
Is arranged not around the target T but around the target T, and a negative potential reflecting electrode 110 that reflects γ electrons and the like is provided on the entire surface thereof. That is, in FIG. 2 and FIG. 3, 101 is a target holder to which the target T is attached, which is made of a cylindrical body having the same outer shape as the target T and a predetermined wall thickness. Through an insulating block 102 made of an insulating material such as DuPont Co., Ltd., a zigzag continuous cooling groove 103a as shown by a dotted line in FIG. Cooling plate 103 made of a material having good thermal conductivity
Are fixed with bolts. Then, the target T is fixed on the support plate 103 with bolts through bolt holes 104 formed around the support plate 103 at predetermined intervals. The cooling groove 103a of the cooling plate 103 is connected to a cooling pipe (not shown) at a connection port 103b so as to directly cool the entire surface of the target T by circulating a cooling medium. The upper surface of the target holder 101, the insulating block 102, the cooling plate 103, and the contact surfaces of the target T are naturally sealed by packing (not shown). With the above configuration, the target T can be easily replaced, the target T can be uniformly cooled in every corner, the deposition rate can be greatly improved, and productivity and stable operation can be effectively achieved.

The reflection electrode 110 that reflects electrons has a frame structure made of copper, iron, or the like having an L-shaped cross section along the periphery of the target T as shown in the drawing, and is directly attached to the side surface of the cooling plate 103 with a bolt to cool and apply a potential. You can do it.

A channel type magnet holder 105 made of a non-magnetic conductive material such as stainless steel is fixed to the outside of the target holder 101 with bolts. The magnet holder 105 has a channel type holder portion 105a formed outside the tip end portion thereof so that the core 121 of the magnetic field generating means 120 and the permanent magnet 122 can be housed therein, and the target T and the cooling plate 10 are also formed.
3 and a predetermined gap 106.

The core 121 and the permanent magnet 122 of the magnetic field generating means 120 are, as shown in the figure, a core 121 made of a plate-like body of a soft magnetic material such as iron or permalloy, which is located on the entire upper surface side in the figure, and the permanent magnet behind it. The magnet holder 105 is fixed to the magnet holder 105 with bolts so that the magnetic pole 122 is arranged so as to generate a magnetic field in the direction perpendicular to the sputtering surface of the target T. The permanent magnet 122 is formed by arranging rectangular rod-shaped magnets of a predetermined length side by side so that the combined magnetic field forms the plasma capturing magnetic field. Therefore, the plasma capturing magnetic field is generated by using the core 121 as a magnetic pole, so that a uniform magnetic field is generated around the target T.

The grounded ring-shaped anode electrode 130 is
10 It is provided in the lateral space of the support so as to surround the inter-target space. By the arrangement of the anode electrode 130,
The collection of γ-electrons during sputtering can be adjusted, and the position thereof can erode the target T and adjust the film thickness distribution in the substrate width direction.

A wire mesh 107 made of stainless steel or the like is laid on the outer surface of the holder portion 105a of the magnet holder. The metal net 107 prevents peeling of spatter deposits deposited on these parts during spattering, that is, abnormal discharge, and simplifies cleaning.
A great effect can be obtained in terms of productivity and stable operation. Reflective electrode
110 is directly attached to the cooling plate 103, and the anode electrode 130 is provided with a cooling passage 131 through which a cooling medium is passed. Since these are prevented from being heated by cooling with water, radiant heat to the substrate is not generated even if the sputtering speed is increased. Since it is small, thermal deformation of the substrate is small and high-speed productivity is realized.

The material of the anode electrode 130 may be any conductive material, and may be the same soft magnetic material as the core 121 described above, or may be copper, stainless steel, or the like. The reflective electrode 110 is a conductive material according to the purpose,
Applicable with insulating material. A conductive material is used when the potential is positively applied from a power source, and an insulating material is used when the self-bias is used in DC sputtering. As is apparent from the arrangement shown in the figure, it is preferable to use a target material for the reflective electrode 110 because the target electrode has the same composition as the target T even when the reflective electrode 110 is sputtered. In this example, the potential of the reflective electrode 110 is the same as that of the target T, but a power source different from the target potential or a target potential and a ground potential are divided so that the potential becomes a negative potential necessary for reflecting γ electrons and the like. Can be formed. It is preferable that the reflective electrode 110 has a potential that does not sputter.

Returning to FIG. 1, the target sections 100, 10
A substrate holding means 40 for holding a long substrate S on which a magnetic thin film or the like is formed is provided beside the opposed targets T and T 'attached to 0'. The substrate holding means 40 includes three feeding rolls 41, a support roll 42, and a winding roll 43, each of which is rotatably supported by a support bracket (not shown) and axially parallel to each other. It is composed of rolls, and is arranged so as to hold the substrate S in a direction substantially perpendicular to the sputtering surface so as to face the space between the targets T ′ and T. The surface temperature of the support roll 42 is adjustable.

Note that other parts of the target parts 100 and 100 '(left side in the figure)
Substrate holding means (not shown) for holding another long substrate S can be provided laterally.

On the other hand, the power supply means 50 composed of a DC power supply for supplying the sputtering power has the plus side connected to the ground and the minus side connected to the targets T and T '. Therefore, the sputtering power from the power supply means 50 is supplied between the anode and the cathode by using the ground as the anode and the targets T and T ′ as the cathode.

As described above, the above-mentioned configuration is the same as that of the above-mentioned Japanese Patent Laid-Open No. 63-270461, and high-speed low-temperature sputtering is possible as is known. That is, in the space between the targets T and T ′, a high-density plasma in which sputter gas ions, γ electrons emitted by sputtering, and the like are bound by the action of the plasma trapping magnetic field is formed. Therefore, the target T,
The spattering of T ′ is promoted to increase the amount of deposition from the space, the deposition rate on the substrate S is increased, and high-speed spattering is possible, and since the substrate S is on the side of the targets T and T ′, low-temperature spattering is possible. I can.

By the way, the high energy γ electrons sputtered from the surface of the targets T, T '
Although it is radiated to the space of T ', it is not affected by the magnetic field up to the center and the vicinity of the outer periphery of the target, so that almost uniform γ
The electron density is reached and the formation of Ar ⁺ ions used for sputtering is made almost uniform over the entire surface of the targets T, T '. On the other hand, in the strong magnetic field region formed on the outer peripheral edge of the target,
As shown in FIG. 4, in addition to the magnetic force lines M extending over the targets T and T ', short-circuit magnetic force lines M'through the target T are formed. Therefore, the γ-electrons emitted from the surface of the center of the target T, T ′ and accelerated in the cathode potential drop portion (interval of several millimeters on the target surface) are bound in a spiral shape along the magnetic force line M, and the target T , T ′ reciprocates, but the γ-electrons generated at the outer edge of the target are constrained by the short-circuit magnetic force lines M ′ and move toward the surface of the core 121 of the magnetic field generating means 120. Therefore, when a grounded shield acting as an anode used in the technique of Japanese Patent Laid-Open No. 59-116376 is provided on the magnetic field generating means 120 or when it is also used as the core 121 thereof, the target outer edge portion A part of the γ-electrons generated in is attracted to the shield. Therefore, the erosion of the target and the thickness of the formed film tended to be biased toward the center. To prevent this, the γ-electrons generated at the targets T and T'reciprocate between the targets to increase the sputtering voltage, or to increase the sputtering gas pressure to generate the magnetron mode. However, there was another problem such as film quality.

On the other hand, in this device, the core 121 of the magnetic field generating means 120 is
Since the negative electrode reflecting electrode 110 for reflecting γ-electrons is provided on the front surface of the portion, as is obvious from FIG.
The γ-electrons moving along is reflected by the surface of the reflective electrode 110 and returned between the targets T and T ′. Further, depending on the arrangement of the anode electrode 130, the absorption of γ electrons can be adjusted.

Therefore, according to the present apparatus, not only can the entire surface of the targets T and T ′ be sputtered uniformly, but also the high speed of γ electrons can be strictly performed, so that the film pressure distribution in the width direction of the substrate can be set in a wide range. In addition to being adjustable arbitrarily, the above-mentioned various effects can be obtained.

Example 1 Targets T and T'each consist of a wide rectangle of 125 mm x 575 mm and are attached to a 15 mm thick copper packing plate via an indium-based adhesive with a graphite carbon target of 5 mm thickness (manufactured by Kojundo Chemical Co., Ltd.). ). The distance between the targets T and T ′ was 200 mm, and the reflective electrode 110 had the same potential as the target. An alnico 7 magnet is used as the magnetic field generating means 120, and the magnetic field in the direction perpendicular to the electrode surface on the reflective electrode 110 is 3
Sputtering power was supplied from the same power source to the targets T and T'of 30 gauss. A carbon plate made of the same material as the targets T, T ′ was attached to the front surface of the reflective electrode 110.

Support roll 42 with a diameter of 200 mm from the end of the target T, T '
The carbon film was formed while the polyester film was running through a roll with the distance to the beginning being 30 mm.

When the sputtering gas pressure PAr with 100% argon was changed from 0.1 to 2 Pa (Pascal), the discharge voltage at a discharge current of 10 A showed stable characteristics from 710V to 570V. Further, in the discharge current range of 1 to 10 A, the change in discharge voltage was substantially constant at 5 V or less.

The polyester film used in this example has a smooth surface with a mean roughness Ra of 1.6 mm and a maximum roughness TIR of 10 nm, provided with fine convex fillers on both sides of the film to impart slipperiness.

The polyester film has a property that oligomer-like particles are deposited on the film surface at a high temperature of 120 ° C. or higher. FIG. 5 shows the results of examining the effect of preventing the roughness of the polyester film surface with respect to the thickness δ of the carbon thin film according to the present invention. The carbon thin film was formed at a temperature of the support roll 42 of 70 ° C. or lower.

As shown in FIG. 5, heat treatment was carried out in a hot air dryer at 160 ° C. for 10 minutes to examine the effect of oligomer sealing and the change in the roughness of the film surface due to the formation of a carb film. As a result, Ra is 1.6 nm to 13.4 nm and TIR is 10.5 nm without the carbon film.
The surface was extremely rough from nm to 136.9 nm. On the other hand, when a carbon film is formed, its thickness is 5 to 40 nm, especially 30 nm.
Below, there is almost no change in the surface property of the film surface, and the oligomer is sufficiently sealed, and the surface roughness is Ra, T
IR is also good. However, at 40 nm or more, both Ra and TIR increase in roughness compared to the film surface.

From the above, it is understood that the thickness of the carb thin film to be provided is preferably 40 nm or less, more preferably 30 nm or less from the viewpoint of maintaining the surface property of the substrate surface. From the viewpoint of oligomer sealing, it can be seen that a film thickness of 5 nm or more is sufficient.

Examples 2, 3 and Comparative Example As a polymer film substrate, a thickness of 50 μm adjusted to the surface roughness of Table 1 by a coating film containing fine filler on both sides
m polyethylene terephthalate (PET) film (Example 2) and a similar coating treatment on only one side, while the other side was left as a polymer film, a 36 μm thick polyethylene naphthalate (PEN) film (implemented) Example 3) was used, but the other configurations were the same, and the above-mentioned permalloy layer and Co-Cr were used.
A two-layered perpendicular magnetic recording medium composed of an alloy layer was manufactured as follows.

First, a carbon film having a thickness of 10 nm was formed on both sides of the polymer film substrate in the same manner as in Example 1.

Then, the film formation example 4 of the above-mentioned JP-A-63-270461,
In the same manner as in 5, a permalloy thin film and a CoCr perpendicular magnetization film were sequentially formed. That is, the permalloy thin film is Ni ₈₀ Fe ₁₅ Mo ₅ (subscript indicates composition (% by weight)) on the targets T and T ′.
Ni alloy plate was attached to the front surfaces of the electron reflection plates 110 and 110 'using the alloy target of No. 3, and the film thickness was set to 0.5 μm under the conditions that the surface temperature of the support roll 42 was 90 ° C. and the argon gas pressure was 0.5 Pa.

For the CoCr perpendicular magnetic film, an alloy target of Co ₈₀ Cr ₂₀ (subscript indicates composition (% by weight)) is used for the targets T and T ′.
A Co plate was attached to the front surfaces of the electron reflection plates 110 and 110 ', and a film thickness of 0.15 μm was formed under the conditions that the surface temperature of the support roll 42 was 130 ° C. and the argon gas pressure was 0.5 Pa.

Then, a cobalt oxide (CoO _x ) film was formed as a protective layer on the CoCr perpendicular magnetization film as follows. That is, using the facing target type sputtering apparatus of the same FIG. 1, using Co metal targets as the targets T and T ′, attaching the Co plate to the front surfaces of the electron reflection plates 110 and 110 ′, and the surface temperature of the support roll 42 to 110 ° C. The sputtering gas was oxygen-containing argon gas (O ₂ concentration: 30% by volume), and the film pressure was 0.5 Pa.

It has been found that the above film formation is all performed in a stable continuous operation, and that the present invention enables continuous production suitable for industrial production.

Also, as a comparative example, the same PET film as in Example 1 was used as a polymer film substrate, carbon thin films were not provided on both sides thereof, and otherwise the permalloy thin film and CoCr perpendicular magnetization film were sequentially formed in the same manner as in Examples 1 and 2. Although it was formed, wrinkles occurred on the film substrate on the support roll 42 and the like, and stable continuous production was not possible. Alternatively, on the surface of the obtained medium, irregular projections having a height of about 70 to 100 nm, which were not observed in the above-mentioned examples, were scattered.

The maximum roughness TIR and the average roughness Ra of the surface of each of the obtained perpendicular magnetic recording media were measured. Table 1 shows the measurement results
Shown in

From Table 1, in the examples, the maximum roughness TIR is 27 nm or less, the average roughness Ra is 3.9 nm or less, and therefore the spacing including the protective layer is 50 nm or less. Has been realized.

On the other hand, in the comparative example using the PET film having the same surface property as that of Example 2, as described above, the medium surface is greatly roughened due to abnormal protrusions not present on the substrate surface, and the effect of the present invention is clear. .

By the way, in Co--Cr alloy system direct magnetic recording, 200 kfrpi
It is possible to achieve high-density recording exceeding the limit (70th anniversary general conference of the Institute of Electronics, Information and Communication Engineers, S3-1, Sho 62), and in order to achieve this, it is necessary to make the spacing of the head and medium as small as possible. Is said. Also in this respect, the present invention is considered to make a great contribution. When a medium having such excellent flatness is used, the spacing between the head and the medium can be minimized and the head surface can be slid while being supported by a large number of minute projections. It has good compatibility with the head surface and is less likely to wear, improving durability. Further, as an experimental example, as disclosed in the material MR87-47 of the Institute of Electronics, Information and Communication Engineers, Magnetic Recording Research Group, if there are protrusions with a height of about 4 to 10 nm in the surface spacing of several microns, tens of thousands of A protrusion with a height of about 10 nm may be scraped by sliding about a path. It is considered that when these minute projections are scraped off and the flatness becomes uniform, the signal level between the head and the medium becomes more stable, and so-called familiarity is achieved. Therefore, the above-mentioned Examples 2 and 3
In the case of thin film hard magnetic recording media with excellent surface flatness, the signal level stability between head media is better than immediately after sliding, especially when recording in high-density recording areas exceeding 100 kfrpi.
The effect of playing is great.

The comparative example, in which a large number of protrusions with a height exceeding 70 nm were generated, was used as a medium for high-density recording, with a large spacing between the head and the medium protrusions, which could easily cause breakage or scraping of the medium. There is a sexual problem.

Also, from Table 1, on the surface side where the surface roughness is adjusted by the coating film of the polymer film substrate, the surface roughness of the substrate is the average roughness Ra.
Whereas 1.1-2.7 nm and maximum roughness TIR is 7.8-17 nm,
The surface roughness of the medium is 3.0 to 3.9 nm in average roughness Ra, and the maximum roughness TI
The R is 21.8 to 27 nm, the average roughness is about 1.7 nm, and the maximum roughness TIR is about 12 nm higher than the substrate.

On the other hand, on the surface side without the coating of Example 2, the increase in the surface roughness of the medium with respect to the surface roughness of the substrate was 0.3 n in terms of the average roughness Ra.
m, maximum roughness TIR is 5 nm, which is half that of the coated surface. Therefore, from the viewpoint of good surface properties, a polymer film having a pure surface with no coating treatment is preferable for the substrate film.

As described in detail above, by forming a carbon layer of about 10 nm on both sides of a polymer film with a surface roughness of 2 nm or less in average roughness Ra and 20 nm or less in maximum roughness TIR, slippage during film running during sputtering can be achieved. Property improves and stable continuous film formation becomes possible, and the oligomer of the polymer film substrate is sealed, and the surface roughness of the metal thin film, especially the maximum roughness TI.
It has become possible to realize a thin film magnetic recording medium with an extremely flat surface with R of 30 nm or less.

[Brief description of drawings]

FIG. 1 is an explanatory view of a facing target type sputtering apparatus used for carrying out the present invention, FIG. 2 is a plan view of the target portion,
FIG. 3 is a cross-sectional view taken along the line AB of FIG. 2, FIG. 4 is an explanatory view of the distribution of magnetic lines of force for explaining the action, and FIGS. 5 (A) and 5 (B) are carbon film thickness and It is a graph which shows the relationship of the surface roughness. T, T ′: target, 10: vacuum chamber, 110: reflective electrode, 120: magnetic field generating means, 130: anode electrode, M: vertical magnetic field line, M ′:
Auxiliary magnetic field lines

Claims (8)

(57) [Claims] 1. A magnetic recording medium having a recording layer made of a ferromagnetic thin film on a polymer film substrate, wherein carbon thin films having a thickness of 40 nm or less are provided on both surfaces of the polymer film substrate, and recording is performed on at least one surface thereof. A magnetic recording medium having a layer. 2. The magnetic recording medium according to claim 1, wherein at least one surface of the polymer film is a smooth surface having a maximum roughness TIR of 20 nm or less, and a recording layer is provided on the smooth surface. 3. The smooth surface of the polymer film has a surface roughness having an average roughness Ra of 2 nm or less.
A magnetic recording medium according to the item. 4. The surface roughness of the medium surface provided with the recording layer has an average roughness Ra of 5 nm or less and a maximum roughness TIR of 30 nm or less. Magnetic recording medium. 5. The magnetic recording medium according to claim 1, 2, 3, or 4, wherein the polymer film substrate is polyethylene terephthalate or polyethylene naphthalate. 6. A method of manufacturing a magnetic recording medium according to claim 1, 2, 3, 4, or 5, wherein the carbon thin film is applied with a magnetic field in a direction perpendicular to a facing target. A method for producing a magnetic recording medium, characterized in that a polymer film substrate is formed while continuously traveling by a facing target type sputtering method in which a film is formed on a substrate which is applied and arranged on the side thereof. 7. The method for producing a magnetic recording medium according to claim 6, wherein the temperature of the polymer film substrate at the time of forming the carbon thin film is 100 ° C. or lower. 8. The method for producing a magnetic recording medium according to claim 6, wherein the opposed target type sputtering method is an opposed target type sputtering method having an opposite electrode which repels electrons around the target.