JPH09120521A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the progress of rusting from the substrate side and to suppress the deterioration of magnetic characteristics with the lapse of time by forming an Ni-contg. metallic underlayer in a specified thickness between the nonmagnetic substrate and a metallic magnetic thin film. SOLUTION: A metallic underlayer 2 made of an Fe-Cr-Ni alloy film is formed on the front side of a nonmagnetic substrate 1 made of a polymer film and a Co-base metallic magnetic thin film is formed as a magnetic layer 3 on the underlayer 2. A protective film 4 is formed on the magnetic layer 3 and the top of the film 4 is successively coated with an org. corrosion inhibitor and a lubricant to form a top layer 5. A back coating layer 6 is disposed on the rear side of the substrate 1 to obtain the objective magnetic tape.

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 metal magnetic thin film formed by a vacuum thin film forming technique as a magnetic layer on a non-magnetic support, and in particular, it has improved corrosion resistance. Regarding

[0002]

2. Description of the Related Art For example, in the field of video tape recorders, there is a strong demand for high density recording in order to achieve high image quality. As a magnetic recording medium corresponding to this, metal or Co--Ni is used. Alloy, Co-Cr alloy, C
Directly on a non-magnetic support such as polyester film, polyamide, polyimide film, etc., by plating a ferromagnetic material made of alloy material such as o-O by means of plating or 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 in which a magnetic layer is formed by deposition is 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, so that the 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 various advantages such that the packing density of the magnetic material can be increased. That is, this metal magnetic thin film type magnetic recording medium is considered to be the mainstream of high density magnetic recording because of its superior magnetic characteristics.

However, in such a metal magnetic thin film type magnetic recording medium, the above-mentioned ferromagnetic material forming the magnetic layer has a high surface activity and is easily oxidized in the atmosphere. In particular, in the manufacturing method up to now, the surface is subjected to a wide range of anti-oxidation treatment, and although practically usable characteristics can be obtained in the environment where it is normally used, from the viewpoint of long-term storage of data, the corrosion resistance is further improved. Is required.

In response to such demands, a method of preventing the above-mentioned ferromagnetic material from being oxidized by providing a rust preventive layer on the magnetic layer has been studied.

However, as the research on the progress of rust of the above-mentioned ferromagnetic material has been advanced, it has been clarified that the progress of rust from the surface of the magnetic layer and the rust progressing from the non-magnetic support side cannot be ignored.

[0007] In particular, rust which progresses from a non-magnetic support has a characteristic that it is generated in the form of islands, and it has been considered that this is caused by insufficient cleaning of the non-magnetic support, but alcohol was used. It is difficult to completely suppress the above-mentioned rust generation by washing or ordinary washing such as using pure water.

Therefore, in order to improve durability and corrosion resistance, it is desired to develop a magnetic recording medium that suppresses the progress of rust from the side of the non-magnetic support and prevents oxidation.

[0009]

Therefore, the present invention has been proposed in view of the above circumstances, and prevents the progress of rust from the non-magnetic support side and deteriorates the magnetic characteristics with time. An object of the present invention is to provide a magnetic recording medium capable of suppressing the above.

[0010]

Means for Solving the Problems As a result of earnest studies, the inventors of the present invention have not achieved the above-mentioned object, and as a result, provided a metal underlayer between the non-magnetic support and the magnetic layer. By using Ni or an alloy thereof as a material, it was found that an excellent rust preventive effect can be obtained, and deterioration of magnetic characteristics can be suppressed even during long-term storage, and the present invention has been completed.

That is, the magnetic recording medium of the present invention is a magnetic recording medium in which a magnetic layer comprising at least a metal magnetic thin film is formed on a non-magnetic support, wherein the non-magnetic support and the metal magnetic thin film are thin. It is characterized in that a metal underlayer containing Ni is formed in a thickness range of 10 nm or more and 500 nm or less.

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 metal magnetic thin film is formed as a magnetic layer on a non-magnetic support by a vacuum thin film forming technique.

In such a magnetic recording medium, a rust preventive layer, which will be described later, is formed on the non-magnetic support, a magnetic layer comprising the metal magnetic thin film is provided on the rust preventive layer, and then a top coat is formed if necessary. After forming a magnetic recording medium roll by applying a back coat or the like, or forming a protective film mainly composed of an inorganic substance on the rust preventive layer, and then forming a top coat layer, a back coat layer, etc., if necessary. After manufacturing the magnetic recording medium original fabric, the magnetic recording medium original fabric is further cut into a predetermined size.

Further, in the present invention, the structure may be combined with a conventional rust preventive layer arranged on the magnetic layer.

In this magnetic recording medium, the non-magnetic support, the metal magnetic thin film and the like which have been conventionally used in this type of magnetic recording medium can be used and are not particularly limited.

As a specific example, the non-magnetic support is made of a polymer material such as polyesters, polyolefins, cellulose derivatives, vinyl resins, polyimides, polyamides and polycarbonates. The polymer support etc. which are formed are mentioned.

Further, as the metal magnetic thin film, Fe,
Ferromagnetic metals such as Co and Ni, Co-Ni alloys, Co-
Ni-Pt based alloy, Fe-Co-Ni based alloy, Fe-N
i-B type alloy, Fe-Co-B type alloy, Fe-Co-N
In-plane magnetization recording metal magnetic film made of i-B type alloy or the like, C
Perpendicular magnetic recording metal magnetic films such as o-Cr alloy thin films and Co-O thin films can be used.

The magnetic layer may be a single-layer film of a metal magnetic thin film made of these ferromagnetic materials or a multi-layer film.

As means for forming the above-mentioned metal magnetic thin film, a vacuum vapor deposition method in which the above-mentioned ferromagnetic metal material is heated and evaporated under vacuum to be deposited on the above-mentioned non-magnetic support, or evaporation of the above-mentioned ferromagnetic metal material is carried out. A so-called PVD method such as an ion plating method performed in discharge, 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, or a CV method.
Either the D method or the plating method can be used.

In the present invention, a base metal layer containing Ni is formed as a rust preventive layer between the metal magnetic thin film and the nonmagnetic support.

Conventionally, various methods of forming a metal layer between a non-magnetic support and a metal magnetic thin film have been carried out for the purpose of improving magnetic properties.
(JP-A-62-42317 and JP-A-62-23)
See Japanese Patent No. 6128. ), Be, Hf, Zr (JP-A-1)
See -287821. ), Th (JP-A-62-1)
See Japanese Patent Publication No. 10619. ), Au, Pt, Ti (see Japanese Patent Laid-Open No. 3-20314), or Al, Si, T.
i, W, Mo, Zr, Ta (JP-A-62-102027)
No. reference. ) And other various metals are used to improve the magnetic properties.

Further, from the viewpoint of rust preventive property, an invention adopting a structure similar to that of the present invention is, for example, Japanese Patent Laid-Open No.
As the description can be seen in Japanese Patent No. 1241151, etc.,
It is known that the rust prevention effect can be enhanced by using Al, Cr, Ti, Cu or the like.

However, these inventions do not systematically select materials, even for inventions whose purpose is to improve the magnetic characteristics and have an anticorrosive effect, and a sufficient anticorrosive effect can be obtained. It is hard to say that it is difficult to achieve both improvement of magnetic properties and anticorrosive effect.

On the other hand, in the present invention, Ni or an alloy containing Ni is used as the constituent material of the rust preventive layer (metal underlayer), and the layer thickness of the metal underlayer is 1
It is defined as 0 nm or more and 500 nm or less. This allows
Oxidation from the non-magnetic support side is reliably suppressed, good corrosion resistance can be ensured, and magnetic properties are improved.

As a method of forming such a metal underlayer, for example, a sputtering method, a physical vapor deposition (PVD) method such as a vacuum vapor deposition method, a chemical vapor deposition (CVD) method, or a plating method can be used.

Of course, the structure of the magnetic recording medium to which the present invention is applied is not limited to this, and may be modified within the scope of the present invention, for example, on the magnetic layer as required. A top coat layer may be formed, or a back coat layer may be formed on the surface of the nonmagnetic support opposite to the surface on which the magnetic layer is formed. When the magnetic layer is a multilayer film, an underlayer or an intermediate layer may be provided in order to improve the adhesive force between the layers and control the coercive force. Also,
For example, the vicinity of the surface of the magnetic layer may be an oxide in order to improve the corrosion resistance. Further, a protective film mainly composed of an inorganic material may be formed on the magnetic layer for the purpose of improving durability, and the top coat layer is formed on the protective film. Is also good.

As the protective film, carbon or Al ₂ O is used.
₃ , Ti-N, Mo-C, Cr-C, SiO, SiO
₂ , Si-N, etc., but not limited thereto, any conventionally known material can be used.

The top coat layer is composed of a rust preventive agent or a lubricant, and any rust preventive agent or lubricant can be used as long as it is one usually used in this kind of magnetic recording medium. And is not particularly limited.

The top coat layer made of the above-mentioned rust preventive agent is provided to prevent the oxidation of the above-mentioned metal magnetic thin film, but a phenomenon in which it is moved by a head that slides at a high speed is observed, or a high temperature is applied. Since it evaporates under the environment, it is difficult to function as a complete rust preventive layer under a severe environment, and further, oxidation progresses from the non-magnetic support to the ferromagnetic material, resulting in deterioration of magnetic characteristics. In addition, the above protective film alone does not always provide a sufficient antirust effect.

The back coat layer is made of an antistatic agent or the like. As the antistatic agent, any antistatic agent can be used as long as it is usually used in this kind of magnetic recording medium. There is no particular limitation.

A metal underlayer made of Ni or an alloy containing Ni is formed between the magnetic layer made of a metal magnetic thin film provided on the non-magnetic support and the non-magnetic support,
By setting the thickness of the metal underlayer to 10 nm or more and 500 nm or less, it is possible to prevent the oxidation from proceeding from the nonmagnetic support side, and suppress the deterioration of the magnetic flux density due to long-term storage.

[0032]

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.

Example 1 In this example, after a metal underlayer was formed on a non-magnetic support by using Fe--Cr--Ni by a sputtering method, a Co thin film was magnetically formed on the metal underlayer by an oblique deposition method. It is an example formed as a layer.

First, the structure of the magnetic tape of this embodiment will be described.

In this magnetic tape, as shown in FIG. 1, a metal underlayer 2 made of a Fe--Cr--Ni alloy film formed by sputtering on a non-magnetic support 1 made of a polymer film. A metal magnetic thin film containing Co as a main component is provided as a magnetic layer 3 on the metal underlayer 2 so as to have a thickness of 50 nm.

A protective film 4 made of a carbon film is formed on the magnetic layer 3. Further, a 0.1% by weight naphthalenediol solution is used as an organic rust preventive agent on the protective film 4, and a lubricant is used. As a top coat layer 5, a 0.5 wt% solution mainly containing an organic substance consisting of a perfluoropolyether derivative is used, and these organic rust preventive agent and lubricant are sequentially applied.

The magnetic layer 3 of the non-magnetic support 1 is also used.
A back coat layer 6 mainly composed of carbon is provided on the surface opposite to the surface on which is formed. The back coat layer 6 contains a vinyl chloride binder as a curing agent.

The magnetic tape having the above structure is
It was manufactured as follows.

In producing this magnetic tape, a sputtering apparatus having a structure as shown in FIG. 2 was used in the step of forming the metal underlayer.

That is, as shown in FIG. 2, this sputtering apparatus is a tape-shaped object to be processed in a vacuum chamber 10 whose inside is kept at a predetermined vacuum degree by a vacuum pump 18 attached to the bottom. The non-magnetic support 11 is sequentially run from the feed roll 13 that rotates at a constant speed in the counterclockwise direction in FIG. 2 toward the winding roll 14 that rotates at a constant speed in the counterclockwise direction.

The non-magnetic support 11 is provided in the middle of the running of the non-magnetic support 11 from the feed roll 13 side to the take-up roll 14 side so as to pull out the non-magnetic support 11 leftward in FIG. A cooling can 15 having a diameter larger than that of each of the rolls 13 and 14 is provided so as to rotate at a constant speed in the counterclockwise direction in FIG.

The feed roll 13, the take-up roll 14 and the cooling can 15 each have a cylindrical shape having a length substantially the same as the width of the non-magnetic support 11.

Therefore, in this sputtering apparatus, the non-magnetic support 11 is sequentially fed from the feed roll 13, passes along the outer peripheral surface of the cooling can 15, and is further wound by the take-up roll 14. In addition to the above, the film is formed when passing through the cooling can 15.

During film formation, an exhaust valve 1 for exhausting to the vacuum pump 18 side is provided between the vacuum pump 18 arranged outside the vacuum chamber 10 and the vacuum chamber 10.
9 is provided, and during film formation, the exhaust speed is appropriately adjusted by narrowing the angle of the exhaust valve 19 from the fully open state to a predetermined angle (here, 10 °).

On the other hand, inside the vacuum chamber 13, there is provided a rectangular target 17 placed on the electrode 17 on the left side of the cooling can 15 in FIG. 2, and between the cooling can 15 and the target 17. The metal underlayer is formed on the non-magnetic support 11 when passing through.

Further, an Ar gas introducing pipe 20 connected to an Ar gas supply device 21 is arranged at the head of the vacuum chamber 10 so as to penetrate the wall surface of the vacuum chamber 10, and the Ar gas introducing pipe 20 is formed at the time of film formation. The Ar gas supply device 2 through the Ar gas introduction pipe 20.
Ar gas is introduced from 1 and a predetermined vacuum degree is set.

In the process of forming the magnetic layer, the process shown in FIG.
A vacuum vapor deposition apparatus having a structure as shown in was used.

That is, as shown in FIG. 3, this vacuum vapor deposition apparatus is a tape-shaped object to be processed in a vacuum chamber 30 whose inside is kept at a predetermined vacuum degree by a vacuum pump 18 attached to the bottom. The non-magnetic support 31 is sequentially run from the feed roll 33 that rotates at a constant speed in the counterclockwise direction in FIG. 3 toward the winding roll 34 that rotates at a constant speed in the counterclockwise direction.

The non-magnetic support 31 is provided in the middle of the running of the non-magnetic support 31 from the feed roll 33 side to the take-up roll 34 side so as to pull out the non-magnetic support 31 leftward in FIG. A cooling can 35 having a diameter larger than that of each of the rolls 33 and 34 is provided so as to rotate at a constant speed in the counterclockwise direction in FIG.

These feed roll 33 and take-up roll 3
4 and the cooling can 35 each have a cylindrical shape having a length substantially the same as the width of the nonmagnetic support 31.

Therefore, in this vacuum vapor deposition apparatus, the non-magnetic support 31 is sequentially fed from the feed roll 33, passes along the outer peripheral surface of the cooling can 35, and is further wound on the winding roll 34. It is designed to be taken.

On the left side of the cooling can 35 in FIG. 3, a crucible 41 filled with a ferromagnetic material (not shown) is arranged.

On the other hand, an electron beam gun 40 is attached to the head of the vacuum chamber 31, and the ferromagnetic material (Co ₁₀₀ is used here) in the crucible 41 is heated and melted by the electron beam gun 40. It is designed to do. And
The vapor flow X evaporated from the crucible 41 is vapor-deposited on the non-magnetic support 31 running along the outer peripheral surface of the cooling can 35 to be formed as a magnetic layer.

Further, an oxygen gas introducing pipe 42 is provided at the bottom of the vacuum chamber 31 so as to penetrate through the wall surface, and the particles of the obtained metal magnetic thin film are formed on the magnetic layer from the oxygen gas introducing pipe 42. Oxygen gas that is introduced to achieve miniaturization is supplied.

It is to be noted that, during the film formation, the vacuum pump 38 and the exhaust valve 39 arranged outside the vacuum chamber 30 adjust the exhaust speed to perform vacuum exhaust, as in the previous sputtering apparatus.

Then, using these sputtering apparatus and vacuum vapor deposition apparatus, a vapor deposition tape was produced as follows.

First, a 99% pure Fe--Cr-- film was formed on a polymer film as a non-magnetic support by a sputtering method.
After forming a metal underlayer having a thickness of 50 nm with Ni (containing 18% by weight of Cr and 8% by weight of Ni, respectively) as a target, a metal magnetic thin film containing Co as a main component is formed by continuous oblique deposition. Then, a magnetic layer composed of a single layer film was provided.

When performing the sputtering for forming the metal underlayer, the pressure of the exhaust valve was reduced to 10 ^-4 Pa by using the sputtering apparatus shown in FIG. 2, and then the angle of the exhaust valve was set to 10 ° from the fully opened state. The exhaust rate is reduced by squeezing the gas to the lower limit, and Ar gas is introduced from the Ar gas introduction pipe to reduce the degree of vacuum in the vacuum chamber to 0.
It was set to 8 Pa. Then, the original fabric was set on the feed roll, and magnetron sputtering was performed while cooling the cooling can to −40 ° C. by a cooling device arranged inside the cooling can. At this time, the distance between the electrode and the target was 45 mm, a voltage of 3000 V was applied to the target, and a state in which a current of 1.4 A flowed was maintained. After the formation of this metal underlayer, the above raw fabric was wound up by the above winding roll.

In the step of forming the magnetic layer,
Using the vacuum vapor deposition apparatus shown in FIG. 3, the pressure was reduced to 10 ⁻⁴ Pa by the vacuum pump, and then oxygen gas was introduced from the oxygen introducing pipe. Then, the original roll provided with the metal underlayer as described above is set on the feed roll, and the cooling can is cooled to −40 ° C. by the cooling device provided inside the cooling can. A ferromagnetic metal material (Co was used here) in the crucible was evaporated with a beam gun at a power of 30 kW to form a Co thin film.

Next, only the target was changed to carbon (C) by the same sputtering apparatus as used in the above-mentioned metal underlayer forming step, and the sputtering conditions were vacuum degree 1.5 Pa, voltage 3500 V, current 3. The film was changed to 2A to form a protective film made of a carbon film.

Subsequently, naphthalene diol was used as an organic rust preventive on the protective film, and a 0.1% by weight solution of this naphthalene diol was applied by a coating machine using a gravure roll, and was dried by a dryer at a temperature of 100 ° C. After drying, a 0.5 wt% solution mainly composed of an organic substance composed of a perfluoropolyether derivative as a lubricant was applied by a coating machine using a gravure roll and dried in the same manner as the above naphthalene diol coating step, and then a top coat was obtained. Layers were formed.

Then, a back coat layer was formed using a vinyl chloride binder as a curing agent mainly composed of carbon to prepare a magnetic recording medium stock.

Further, this raw material of the magnetic recording medium was cut into a width of 8 mm to obtain a sample tape.

The film thickness was measured with a TEM (transmission electron microscope) after the metal underlayer was formed.

Therefore, the sample tape prepared in this way and the comparative tape prepared by the conventional manufacturing method without forming the above-mentioned metal underlayer for comparison (referred to as Comparative Example 1).
The storage characteristics were investigated.

The storage characteristics of the magnetic recording medium are as follows:
The sample was left for 144 hours under a high temperature and high humidity condition of 95% humidity, and the amount of deterioration of the residual magnetic flux density due to the standing was determined based on the following formula (1) to investigate.

[0067]

(Equation 1)

However, in the above equation (1), Φr ₀ represents the initial residual magnetic flux density, and Φr ₁ represents the residual magnetic flux density after leaving.

Further, in the sample tape of Example 1 and the above-mentioned comparative tape, cracks (cracks in the magnetic layer) may or may not occur during cutting, and those having cracks may deteriorate the storage characteristics. A trend was seen.

Therefore, in order to make a strict comparison, the state of crack generation on the cut surface was examined before storage, and only those with few cracks were used for measuring the storage characteristics.

In the current manufacturing method, it is very difficult to perform cutting without generating cracks, and an optical microscope (manufactured by Nikon, trade name HXF-II: objective lens BD Pl) is used.
It was observed with an5DIC eyepiece lens 10 times), and 0.
A sample having an average of 20 to 40 cracks in a range of 1 mm was used as a sample.

As a result, in the comparative tape on which the metal underlayer was not formed, although the number of cracks was 35, the deterioration amount of the residual magnetic flux density reached 11.6%.

On the other hand, in the sample tape according to Example 1, 37 cracks were generated on average and the deterioration amount of the residual magnetic flux density was about 5.0%.

Next, when measuring the storage characteristics, the deterioration amount of the residual magnetic flux density of the sample tape and the comparative tape when the storage time was changed was examined in the same manner.

The results are shown in FIG.

From FIG. 4, it was found that the sample tape was superior in corrosion resistance to the comparative tape.

Further, the conditions under which the effect of the metal underlayer is observed were examined.

First, the amount of deterioration of the residual magnetic flux density when the film thickness of the metal underlayer was changed was similarly examined. In addition,
The electrode voltage and the Ar gas concentration are also important parameters in the formation of this rust preventive layer, but the data is the most effective for the sputtering device used in Example 1 above because of the large device dependence.

The results are shown in FIG.

As shown in FIG. 5, it was found that if the thickness of the metal underlayer is 10 nm or more, the same effect is obtained as compared with the case where the protective film is not formed.

Here, in order to measure the thickness of the above-mentioned protective film, it is judged by a photograph taken at 200,000 times with a transmission electron microscope (TEM). However, when the above-mentioned metal film is formed, unevenness occurs in the film thickness. Therefore, 10 points were measured per sample for determining the film thickness, and the average value thereof was taken as the film thickness of the metal layer.

Further, it was observed that the thicker the metal underlayer, the better the anticorrosive effect, but the film thickness of 100
In the range of nm or more, the rust preventive effect converged to a substantially constant value.

Further, in this metal underlayer, as the film thickness becomes thicker, particles become coarser as the underlayer, and when a vapor deposition film is formed on the underlayer, the magnetic characteristics of the obtained metal magnetic thin film are contradicted. It turned out to deteriorate.

Next, output characteristics were examined in order to examine changes in electromagnetic conversion characteristics when the film thickness of the metal underlayer was changed.

The results are shown in FIG.

As shown in FIG. 6, it was found that when the film thickness of the metal underlayer exceeds 500 nm, the improvement is only about 6 dB as compared with the coating type comparative tape prepared for comparison. It was

Therefore, compared with the high output of the recent coating type magnetic tape, the improvement is only about 1 dB at most. Therefore, the thickness of the metal underlayer is 50%.
It has been found that it is desirable to set 0 nm as the upper limit.

Example 2 The Fe-Cr-Ni alloy used as a target when forming the metal underlayer in Example 1 was changed to Ni,
Other than that, the same device as in Example 1 was used, and a sample tape was produced under the same conditions in a large frame although the sputtering voltage and the like were slightly different.

Then, in order to examine the storage characteristics of the obtained sample tape, the deterioration amount of the residual magnetic flux density was measured in the same manner as in Example 1 above.

The results are shown in FIG. The results of the comparative tape are also shown in FIG.

As shown in FIG. 7, the sample tapes of this example also exhibited excellent corrosion resistance in all cases as compared with the comparative tape, and basically the same results as in Example 1 were obtained. It was found that

[0092]

As is apparent from the above description, in the present invention, since the metal underlayer is formed between the non-magnetic support and the magnetic layer composed of the metal magnetic thin film, the non-magnetic support resistance is increased. Oxidation from the side can be prevented, and excellent corrosion resistance can be obtained.

Therefore, according to the present invention, even when stored for a long period of time under conditions of high temperature and high humidity, deterioration of magnetic characteristics over time can be suppressed and good electromagnetic conversion characteristics can be secured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a magnetic tape according to the present invention.

FIG. 2 is a schematic diagram showing a configuration example of a sputtering apparatus used in a step of forming a metal underlayer when a magnetic tape is manufactured by applying the present invention.

FIG. 3 is a schematic diagram showing a configuration example of a vacuum vapor deposition apparatus used in a step of forming a magnetic layer when a magnetic tape is manufactured by applying the present invention.

FIG. 4 is a characteristic diagram showing storage characteristics of a magnetic tape in which a metal underlayer is provided by using Fe—Cr—Ni on a non-magnetic support.

FIG. 5 is a characteristic diagram showing the deterioration amount of the residual magnetic flux density when the thickness of the metal underlayer is changed in the magnetic tape.

FIG. 6 is a characteristic diagram showing changes in output characteristics when the film thickness of a metal underlayer is changed in the magnetic tape.

FIG. 7 is a characteristic diagram showing storage characteristics of a magnetic tape in which a metal underlayer is provided by using Ni on a nonmagnetic support.

[Explanation of symbols]

 1 non-magnetic support 2 metal underlayer 3 magnetic layer 4 protective film 5 top coat layer 6 back coat layer

Claims (3)

[Claims] 1. A magnetic recording medium in which a magnetic layer made of at least a metal magnetic thin film is formed on a non-magnetic support, wherein Ni is provided between the non-magnetic support and the metal magnetic thin film.
The metal underlayer containing is 10 nm or more and 500 nm thick
A magnetic recording medium formed in the following range. 2. The magnetic recording medium according to claim 1, wherein the metal underlayer is made of Ni. 3. The magnetic recording medium according to claim 1, wherein the metal underlayer is made of a Fe—Cr—Ni alloy.