JP2003346329A - Magnetic recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium which copes with miniaturization of cassettes and high-density recording, low in noise, superior in electromagnetic conversion characteristics, traveling durability and friction characteristics, and suitable for a recording and reproducing system provided with a magnetoresistance effect type reproducing head. <P>SOLUTION: A magnetic layer 2 of Co metal magnetic thin film is formed by a vacuum deposition method on a polyester base film 1, and a protective layer 3, comprising diamond-like carbon, is formed by a plasma CVD method on the magnetic layer 2. After a back layer 4 containing carbon and a binder is formed on a surface on a side opposite to the surface where the magnetic layer of the base film is formed, the base film is made to run on a vacuum roll having micropores, and periodical waves having periodicity of 10 to 500 nm and an amplitude of 10 to 300 nm is formed on the surface. <P>COPYRIGHT: (C)2004,JPO

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 in which a ferromagnetic metal thin film is formed as a magnetic surface on a non-magnetic support by means of a vacuum thin film forming means such as vapor deposition or sputtering. The present invention relates to a magnetic recording medium compatible with a recording / reproducing system having a sensitive magnetoresistive head

[0002]

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

On the other hand, with the growing demand for high-density magnetic recording, Co-Ni-based alloys, Co-Cr-based alloys, Co-
A metal magnetic material such as O is plated, or directly deposited on a non-magnetic support such as a polyester film, a polyamide film or a polyimide film by a vacuum thin film forming means such as a vacuum evaporation method, a sputtering method or an ion plating method. A magnetic recording medium of a metal magnetic thin film type has been proposed and attracts attention.

The magnetic recording medium of the metal magnetic thin film type is excellent in coercive force, squareness ratio, etc., and is excellent not only in electromagnetic conversion characteristics at a short wavelength, but also because the thickness of the magnetic layer made of the metal magnetic thin film can be extremely thin. In addition, since the thickness loss at the time of recording demagnetization and reproduction is extremely small, and there is no need to include a binder made of a non-magnetic material in the magnetic layer as in the case of the coating type magnetic recording medium, It has many advantages, including the ability to increase packing density.

Further, in order to improve the electromagnetic conversion characteristics of this type of magnetic recording medium and to obtain a larger output, when the magnetic layer of the magnetic recording medium is formed, the magnetic layer is inclined. The so-called oblique deposition for vapor deposition has been proposed and already put into practical use.

As described above, efforts are being made to improve the performance of magnetic recording media for higher densities. As the tendency to increase the size of the magnetic tape is increased, the thickness of the magnetic tape is required to be further reduced (thinning).

In general, a magnetic recording medium includes a nonmagnetic support and a magnetic layer, and a protective layer provided on the surface of the magnetic layer for the purpose of improving durability and running properties. A back layer is provided on the surface of the body opposite to the side on which the magnetic layer is formed. That is, these non-magnetic supports,
The thickness of the medium is determined by the constituent layers such as the magnetic layer, the protective layer and the back layer.

In addition, it is essential to increase the areal recording density in order to increase the volume recording density. For this purpose, a high-sensitivity magnetoresistive effect such as an MR head or a GMR head is used in place of a conventionally used magnetic induction type head. It is essential to use a mold head. When a recording / reproducing system having an MR head as a read head is used, the upper limit of the thickness of a magnetic layer formed on a non-magnetic support of a magnetic recording medium is limited due to the high detection sensitivity of the MR head. It must be less than 100 nm, preferably less than 80 nm.

As described above, it is known that the magnetoresistive head has a very high detection sensitivity and is greatly affected by noise depending on the surface properties of the magnetic layer. Therefore, in the past, the base surface was coated with a coating material in which an organic binder and a filler were dispersed and mixed to give a desired roughness, but such a method resulted in a very smooth surface, which was sufficient. Satisfactory running stability and durability could not be obtained.

In order to cope with a recording / reproducing system having a high-sensitivity head, in order to suppress the noise component of the magnetic tape as much as possible as described above, it is necessary to make the tape surface smoother than before. On the other hand, it is necessary to solve the problems of deterioration in running durability and friction characteristics due to smoothing, but the conditions for satisfying both of these requirements are severe, and a solution has been demanded.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to cope with a reduction in the size and recording density of a cassette, low noise and good electromagnetic conversion characteristics. Another object of the present invention is to provide a thin magnetic recording medium which has excellent running durability and friction characteristics and is suitable for a recording / reproducing system including a magnetoresistive head.

[0012]

According to the present invention, a magnetic layer composed of a ferromagnetic metal thin film is formed on a non-magnetic support composed of a base film, and the magnetic layer is formed on the opposite side of the non-magnetic support from the surface on which the magnetic layer is formed. In a magnetic recording medium having a back layer formed on its surface,
It is an object of the present invention to provide a magnetic recording medium in which the surface is provided with periodic undulations to suppress abrasion of the tape surface at the time of contact between the head and the tape and prevent deterioration of durability due to wear of the protective film layer. In particular, the surface undulation period should be 10
The contact between the head and the tape is improved by setting the head width to 500 μm and the amplitude to 10 to 300 nm. As a result, wear deterioration due to running is reduced, the head is free from deposits, and high durability and running stability are provided. And a highly reliable magnetic recording medium.

In the magnetic recording medium having a periodic waviness on the surface, a magnetic layer composed of a ferromagnetic metal thin film is formed on a nonmagnetic support composed of a base film, and the surface of the nonmagnetic support on which the magnetic layer is formed is formed. In a manufacturing step of forming a back layer on the opposite side to obtain a magnetic recording medium, in any step after the formation of the magnetic layer, the base film is run on a vacuum roll having pores, and It can be produced by a method of imparting periodic undulation or a method of sandwiching the base film between rubber rolls and imparting periodic undulation to the surface. By such a manufacturing method, a magnetic recording medium having high durability and running stability having a swell controlled on a surface at a desired period and amplitude is manufactured.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetic recording medium according to the present invention and a method for manufacturing the same will be described in detail. Examples of the base film for a non-magnetic support of the present invention include, for example, generally used polyester films. Examples of such polyester films include polyethylene terephthalate (PET) and polyethylene naphthalate (P).
EN), polytetramethylene terephthalate, poly-
1,4-cyclohexylene dimethylene terephthalate,
Examples thereof include polyethylene-2,6-naphthalene dicarboxylate and polyethylene-p-oxybenzoate, and polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are particularly preferably used. These polyesters may be homopolyesters or copolyesters. When used as the base film for a non-magnetic support of the present invention, the thickness of the polyester film is preferably about 2 to 5 μm, more preferably 2 to 4 μm.

As the non-magnetic support composed of a base film, a surface condition in which a specific roughness is imparted to the side on which the magnetic layer is formed (magnetic surface) and the surface opposite to the side on which the magnetic layer is formed (running surface). Are preferred. In order to impart a specific roughness to the magnetic surface, a filler of about several nm to several tens nm may be dispersed to roughen the surface of the nonmagnetic support.

A magnetic thin film is formed as a magnetic layer on a non-magnetic support by directly applying a ferromagnetic metal material without using a binder or the like. Any material may be used as long as it is used for a normal evaporation tape. As an example of a metal magnetic material for forming a magnetic layer, Fe, C
o, ferromagnetic metals such as Ni, Fe-Co, Co-Ni,
Fe-Co-Ni, Fe-Cu, Co-Cu, Cb-A
u, Co-Pt, Mn-Bi, Mn-Al, Fe-C
r, Co-Cr, Ni-Cr, Fe-Co-Cr, Fe
-Co-Cr, Co-Ni-Cr, Fe-Co-Ni-
Ferromagnetic alloys, such as Cr, are mentioned. The magnetic layer may be a single-layer film of the metal magnetic material or a multilayer film.

Means for forming a magnetic metal thin film include a vacuum evaporation method in which a ferromagnetic material is heated and evaporated under vacuum and deposited on a non-magnetic support, and an ion plating method in which a ferromagnetic metal material is evaporated during discharge. Alternatively, a PVD technique such as a sputtering method in which atoms on the target surface are beaten with argon ions generated by causing a glow discharge in an atmosphere containing argon as a main component can be employed.

If necessary, an underlayer or an intermediate layer may be provided between the nonmagnetic support and the metal magnetic thin film or between the layers of the multilayer film for the purpose of improving the adhesive force or controlling the coercive force. It may be provided. Further, for the purpose of improving the corrosion resistance of the magnetic layer, for example, the vicinity of the surface of the magnetic layer may be in an oxide state.

A protective layer may be formed on the magnetic layer of the metal magnetic thin film formed on the non-magnetic support.
The protective layer is for protecting the magnetic layer from sliding with the magnetic head. In magnetic recording media, the surface tends to be further smoothed in order to suppress spacing loss in response to higher density. However, when the surface of the magnetic layer becomes smooth, the contact area with the head increases, so that the frictional force increases and the shear stress generated in the magnetic layer increases. In order to protect the magnetic layer from such severe sliding conditions, it is necessary to form a protective layer.

As the material for forming the protective layer, any material may be used as long as it is generally used as a protective film for ordinary metal magnetic thin films. For example, carbon, C
rO ₂ , Al ₂ O ₃ , BN, Co oxide, MgO, Si
O ₂ , Si ₃ O ₄ , SiN ₄ , SiC, SiN ₄ , SiO ₂ ,
Examples include ZrO ₂ , TiO ₂ , and TiC. The protective layer is
The material may be a single-layer film or a multilayer film.

Next, a back layer is formed on the surface of the non-magnetic support made of the base film opposite to the surface on which the magnetic surface is formed. The back layer lowers the electrical resistance of the surface of the non-magnetic support made of the base film to prevent running defects due to charging, and improves the durability of the non-magnetic support to prevent the occurrence of damage during use, Alternatively, it is provided for the purpose of reducing friction between the tapes. The formation of this back layer is essential for improving the running property and durability of the tape.

The material for forming the back layer may be any material which is generally used for the back layer. For example, carbon, CrO ₂ , Al
₂ O ₃ , BN, Co oxide, MgO, SiO ₂ , Si
₃ O ₄ , SiN ₄ , SiC, SiN ₄ , SiO ₂ , ZrO ₂ ,
TiO ₂ , TiC and the like can be mentioned. The back layer may be a single-layer film or a multilayer film of the above materials.

The back layer may be formed by a thin film forming process such as a vacuum evaporation method such as a CVD method or a sputtering method, or may be formed by dispersing and mixing the above materials together with an organic binder to form a coating material and applying the coating material. You can also. The back layer is formed to a thickness of about 0.5 μm.

The configuration of the magnetic tape according to the present invention is not limited to the above, but may be changed without departing from the scope of the present invention, for example, forming an undercoat layer on a non-magnetic support as necessary. Or forming a layer of a lubricant, a rust preventive, or the like.

As the above-mentioned lubricant, any one can be used as long as it is generally used as a magnetic tape, but a fluorocarbon-based, alkylamine, alkylester or the like main skeleton is particularly preferred. For example, those modified with a tertiary amine having fluorocarbon as a main skeleton are used.

The periodic undulation according to the present invention is characterized in that the magnetic layer, the protective layer, and the back layer are formed during the manufacturing process applied to the formation of each layer constituting the magnetic recording medium. After the formation, it can be formed in any process. As a method of forming the undulation in the above-mentioned optional step, any method may be used as long as a desired periodic undulation can be obtained. For example, a base film is run on a vacuum roll having pores with small holes on the surface, and a method of imparting a desired periodic undulation to the surface, or a base film is sandwiched between rubber rolls having irregularities on the surface, A method of imparting a desired periodic undulation to the surface can be suitably used. In addition,
The total thickness of such a metal magnetic thin film type magnetic recording medium is 7
It is preferably not more than μm.

The periodic undulation on the surface of the magnetic recording medium of the present invention is preferably formed by controlling the undulation period to be 10 to 500 μm and the undulation amplitude to be 10 to 300 nm. The swell period is smaller than 10 μm,
If the undulation amplitude is smaller than 10 nm, the contact between the head and the tape is not improved, and the friction increases. Therefore, the wear deterioration of the tape surface due to running cannot be suppressed, and high durability and running stability cannot be obtained. Conversion characteristics deteriorate.
If the undulation cycle is larger than 300 μm and the undulation amplitude is larger than 500 nm, the contact between the head and the tape becomes worse, and the output waveform is chipped (envelope chipping). This degrades the electromagnetic conversion characteristics.

[0028]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the embodiments.

Examples 1 to 7, Reference Examples 1 to 4 and Comparative Example 1 As a base film of a nonmagnetic support, polyethylene naphthalate having a width of 150 mm was used. A magnetic layer 2, a protective layer 3, and a back layer 4 are sequentially formed in a layer configuration, and after applying a lubricant 5, a desired periodic undulation is imparted to the surface to obtain Examples 1 to 7 and Reference Examples 1 to 4. Each magnetic recording medium (raw magnetic tape) was produced. Comparative Example 1
Is the same as the layer configuration of FIG. 1 and the method of forming each layer is exactly the same as that of the embodiment and the reference example, but is a magnetic tape which does not have periodic waviness as described later. The magnetic layer 2
Is formed from a Co metal magnetic thin film, and the protective layer 3 is diamond-like carbon. The back layer 4 was formed by a coating method using a paint containing carbon and a binder. The total thickness of the magnetic recording medium is 7 μm or less. The main manufacturing conditions of the respective constituent layers of the manufactured magnetic recording medium shown in FIG. 1 are shown below.

[Formation of Magnetic Layer] A magnetic layer 2 composed of a single Co film was formed on one surface of the base film 1 under the following conditions for forming a magnetic layer using a vacuum deposition apparatus shown in FIG.

<Film formation conditions of magnetic layer> Ingot: 100% by weight of Co Incident angle: 45 to 10 ° Introduced gas: oxygen gas Oxygen introduction amount: 3.3 × 10 ⁻⁶ m ³ / sec Vacuum degree during vapor deposition: 2 × 10 ^-2 Pa magnetic layer thickness: 60 nm

[Apparatus Configuration and Vapor Deposition Process] A vapor deposition process for forming the magnetic layer 2 using the vacuum vapor deposition apparatus shown in FIG. 2 will be described. In the vacuum deposition manufacturing apparatus of FIG. 2, a feed that rotates at a constant speed in the clockwise direction in the drawing into a vacuum chamber 12 that is evacuated from exhaust ports 11 provided at the head and the bottom, respectively, and has a vacuum state inside. A roll 13 and a take-up roll 14 that rotates at a constant speed in the clockwise direction in the figure are provided.
The base film 1 of a tape-shaped non-magnetic support runs sequentially from the feed roll 13 to the take-up roll 14.

In the middle of the travel of the base film 1 from the feed roll 13 to the take-up roll 14 side, each roll 1
A cooling can 16 having a diameter larger than the diameter of the cooling cans 3 and 14 is provided. The cooling can 16 is provided so as to pull out the base film 1 downward in the drawing, and is configured to rotate at a constant speed in the clockwise direction in the drawing. The feed roll 13, the take-up roll 14, and the cooling can 16
Have a cylindrical shape having a length substantially equal to the width of the base film 1, and a cooling device (not shown) is provided in the cooling can 16 so that the base film 1 is deformed due to a rise in temperature. Etc. can be suppressed.

Therefore, the base film 1 is sequentially sent out from the feed roll 13, further passes through the peripheral surface of the cooling can 16, and is wound up by the take-up roll 14. Guide rolls 17 and 18 are provided between the feed roll 13 and the cooling can 16 and between the cooling can 16 and the take-up roll 14, respectively. A predetermined tension is applied to the base film 1 running from the cooling can 16 to the ticket collecting roll 14, and the base film 1
Is adjusted to run smoothly. Further, the crucible 1 is placed in the vacuum chamber 12 below the cooling can 16.
The crucible 19 is filled with a Co ingot 20 which is a metal magnetic material for film formation. The crucible 19 has substantially the same width as the width of the cooling can 16 in the longitudinal direction.

On the other hand, on the side wall of the vacuum chamber 12, an electron gun 21 for heating and evaporating the Co ingot 20 filled in the crucible 19 is mounted. The electron gun 21 is provided with an electron beam X emitted from the electron gun 21.
Is disposed at a position where the Co ingot 20 in the crucible 19 is irradiated. And this electron gun 21
The evaporated Co is deposited as a magnetic layer 2 on one surface of the base film 1 running at a constant speed on the peripheral surface of the cooling can 16.

A shutter 22 is provided between the cooling can 16 and the crucible 19 in the vicinity of the cooling can 16. This shutter 22 is connected to the cooling can 1
6 is formed so as to cover a predetermined area of the base film 1 running at a constant speed on the peripheral surface of the base film 1.
Is deposited obliquely within a predetermined angle range, and in this embodiment, the deposition was performed at an incident angle of 45 to 10 °. In addition, when such deposition, in the embodiment of the oxygen gas to the surface of the base film 1 via an oxygen gas inlet 24 provided through the side wall of the vacuum chamber 12 3.3 × 10m ³ / It is supplied in seconds to improve magnetic properties, durability and weather resistance.

[Formation of Protective Layer] Next, a plasma CV was formed on the surface of the magnetic layer (Co single layer film) formed on one surface of the base film 1 by using the CVD manufacturing apparatus shown in FIG.
A protective layer made of carbon (diamond-like carbon) was formed by Method D under the following film forming conditions.

<Deposition conditions of protective layer> Reaction gas: toluene Reaction gas pressure: 10 Pa Introduced power: DC 1.5kV Film thickness of carbon protective layer: 10 nm

[Apparatus Configuration and Plasma CVD Process] The CVD apparatus shown in FIG.
In a vacuum chamber 32 whose interior has been brought into a high vacuum state by a zero, a feed roll 3 which rotates at a constant speed in the counterclockwise direction in the figure.
3 and a take-up roll 34 that rotates at a constant speed in the counterclockwise direction in the figure. The base film 1 on which the magnetic layer 2 is formed, The formed base film 31 runs sequentially.

In the middle of the travel of the magnetic layer forming base film 31 from the feed roll 33 to the take-up roll 34,
A counter electrode can 39 having a diameter larger than the diameter of each of the rolls 33 and 34 is provided. The counter electrode can 39 is provided so as to pull out the magnetic layer forming base film 31 downward in the figure, and is configured to rotate clockwise in the figure at a constant speed. The feed roll 3
3. The winding roll 34 and the counter electrode can 39
Each has a cylindrical shape having substantially the same length as the width of the magnetic layer forming base film 31.

Accordingly, the magnetic layer-forming base film 3
1 is sequentially sent out from a feed roll 33, further passes through the peripheral surface of the counter electrode can 39, and is taken up by a take-up roll 34.
It is being wound up. Guide rolls 38 are disposed between the feed roll 33 and the counter electrode can 39 and between the counter electrode can 39 and the take-up roll 34, respectively. A predetermined tension is applied to the counter electrode can 39 and the magnetic layer forming base film 31 running from the counter electrode can 39 to the take-up roll 34, so that the magnetic layer forming base film 31 runs smoothly. ing.

In the vacuum chamber 32, a reaction tube 35 made of Pyrex glass (registered trademark) or plastic is provided below the counter electrode can 39. One end of the reaction tube 35 passes through the bottom of the vacuum chamber 32, and a reaction gas (toluene) for film formation is introduced into the reaction tube 35 from this end. . Further, an electrode 36 made of a metal mesh is attached to a middle part of the reaction tube 35. The electrode 36 is connected to a DC power supply 37 provided outside, and a voltage of 500 to 2000 V is applied. In this CVD apparatus, when a voltage is applied to the electrode 36, the electrode 36 and the counter electrode can 39 are applied.
Glow discharge occurs between the two. Then, the toluene of the film forming gas introduced into the reaction tube 35 is decomposed by the generated glow discharge and adheres to the surface of the magnetic layer of the magnetic layer forming base film 31.

[Formation of Back Layer] Next, the following coating composition was applied to the other surface of the non-magnetic support 1 opposite to the surface on which the magnetic layer (Co single layer film) of the magnetic layer forming base film 31 was formed. Was prepared, and was applied and dried using a microgravure coating method to form a back layer.

<Coating composition for back layer> Coating composition: carbon (20 nm × 97 wt% + 100 nm × 3 wt)
%) Binder (polycarbonate / polyurethane) Mixed solvent (toluene / MEK / cyclohexanone (anone)) Carbon / binder ratio (P / B ratio): 50/50 Solid content: 20%

As described above, a perfluoropolyether-based lubricant is applied to the magnetic surface side of each tape having the magnetic layer 2, the protective layer 3, and the back layer 4 formed on the base film 1, and the respective magnetic layers are formed. An original tape was produced. As the lubricant, a fluorocarbon having a main skeleton and modified with a tertiary amine was used. Demnum (trade name: manufactured by Daikin Industries, Ltd.)
The tertiary amine was synthesized using dimethyldecylamine to form a salt structure.

After applying the above-mentioned lubricant, each of the magnetic tape raw materials is run on a vacuum roll having pores,
Examples 1 to 7 were obtained by giving a predetermined periodic undulation to the surface by controlling the undulation period and the undulation amplitude as shown in Table 1.
And the tapes of Reference Examples 1 to 4 were produced. The tape of Comparative Example 1 was not provided with periodic waviness.

[0047]

[Table 1]

Each of the obtained magnetic tape raw materials was 6.3.
The tape was cut into a width of 5 mm to obtain evaluation magnetic tapes of Examples 1 to 7, Reference Examples 1 to 4, and Comparative Example 1.

For each of the 6.35 mm evaluation magnetic tapes obtained above, evaluation of the tape properties (surface shape, surface lubricant amount, dynamic friction coefficient) and durability evaluation (still durability, shuttle durability, lack of envelope) Was measured and evaluated under the following conditions. Table 2 shows the results.

<Evaluation Conditions> (1) Surface shape (undulation period, undulation amplitude): ZYG
3D surface structure analyzer Niew View50 manufactured by Company O
00 was measured. (2) Amount of lubricant: Measured using ESCA manufactured by SHIMAZU, and the value of Example 1 was standardized as 1. (3) Dynamic friction measurement: The magnetic surface side of the evaluation magnetic tape was hung on a SUS guide having a diameter of 2 mm so as to have a holding angle of 90 ° and slid for 100 pass, and the maximum value of the friction coefficient was expressed as the dynamic friction coefficient. If the value exceeds 0.4, there is a possibility of sticking to a drum or a guide due to running, so it was judged as NG. (4) Still durability: after recording a signal of 0.3 μm,
With reference to the initial reproduction output, the time until the point of 3 dB drop was measured and defined as a still time. Stills were rated as good for 20 minutes or more. (5) Shuttle durability: 0.3 μm was recorded over the entire length of the tape, and a portion having the lowest output during 100 pass running was evaluated as a level down (in dB) based on the initial output. For the shuttle, circles were within -3 dB. (6) Envelope chipping amount: Observing the envelope of the “hit waveform” of the tape with respect to the head, the following equation (1) is obtained.
Was calculated by

[0051]

(Equation 1)       Envelope chipping (dB) = 20 log (A / B) (1)

In the above equation (1), A and B represent the steady state (A) of the output waveform and the missing state (B) of the output waveform indicating the state of the tape hitting the head, respectively, as shown in the model diagram of FIG. Is shown. Output waveform missing amount (envelope)
However, when the head touch was -2.0 dB or more, the head touch was not good, and therefore, NG was determined. As the evaluation deck, a commercially available Sony digital video (VX-1000) was remodeled and used with an MR head.

[0053]

[Table 2]

From the above evaluation results, it was found that the cycle was in the range of 10 to 500 μm and the amplitude was
The magnetic tapes for evaluation of the present invention (Examples 1 to 7) in which the periodic waviness was imparted by controlling in the range of 300 nm had a dynamic friction coefficient of 0.4 or less, still durability of 20 minutes or more, and shuttle durability. The properties were within -3 dB, and the amount of envelope chipping was less than -2 dB, indicating good friction characteristics and durability. On the other hand, in Reference Example 1 in which the undulation cycle was 8 μm, the cycle was too short and the dynamic friction coefficient was large, and the still durability and shuttle durability were poor. In addition, the swell cycle is 52
In Reference Example 2 of 0 μm, the period was too long, and the missing amount of the envelope exceeded −2 dB, resulting in poor head touch. Further, in Reference Example 3 in which the undulation amplitude was 8 nm, the amplitude was too small and the dynamic friction coefficient was large, and the still durability and shuttle durability were deteriorated. The undulation amplitude is 315
In Reference Example 4 of nm, the amplitude was too large, and the missing amount of the envelope exceeded -2 dB, resulting in poor head touch. In the case of Reference Example 1 having no undulation, both the still durability and the shuttle durability exhibited extremely poor properties.

FIG. 5 shows the surface condition when the surface of the magnetic tape of the embodiment having undulation was observed by an optical photograph while running on a vacuum roll having pores. A so-called periodic swell with a uniform period and amplitude is clearly observed. FIG. 6 shows a surface state when the surface of the magnetic tape of the comparative example having no undulation is observed by an optical photograph. A flat surface state without undulation is observed.

In Examples 1 to 7, each of the constituent layers was formed on the surface of the non-magnetic support, and after applying a lubricant, the layer was run on a vacuum roll having pores to form Instead of imparting periodic undulations, except that a periodic undulation was formed on the surface of the raw tape running on a rubber roll having irregularities on the surface, a magnetic tape for evaluation was produced and evaluated in the same manner as in the above example. The surface shape (undulation period, undulation amplitude), surface lubricant amount, and dynamic friction coefficient are the same as those of the above-described embodiment, and the still durability, shuttle durability, and envelope chipping amount are also the same, indicating good durability. Was.

[0057]

According to the present invention, a magnetic layer of a ferromagnetic metal thin film is formed on a nonmagnetic support, and a back layer is formed at least sequentially on the surface of the nonmagnetic support opposite to the surface on which the magnetic layer is formed. In the manufacturing process, a periodic noise is imparted to the surface of the magnetic recording medium at an arbitrary step after the formation of the magnetic layer, so that a low noise characteristic suitable for a recording / reproducing system having a magnetoresistive effect type reproducing head is obtained. While maintaining it, it is possible to prevent the deterioration of durability due to the wear of the protective layer, and it has good electromagnetic conversion characteristics, excellent running durability and friction characteristics, and can respond to cassette miniaturization and high recording density A recording medium and a method for manufacturing the same can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a layer configuration of a magnetic recording medium in an example and a reference example.

FIG. 2 is a schematic diagram showing a vacuum evaporation apparatus used for forming a magnetic layer of a magnetic recording medium in Examples, Reference Examples, and Comparative Examples.

FIG. 3 is a schematic view showing a plasma CVD apparatus used for forming a protective layer of a magnetic recording medium in Examples, Reference Examples and Comparative Examples.

FIG. 4 is a model diagram of an output waveform showing a state of a tape hitting a head applied to the calculation of an envelope chipping amount in evaluations of an example, a reference example, and a comparative example.

FIG. 5 is a diagram showing a surface state when the surface of an evaluation magnetic tape having periodic waviness imparted to the surface of an example is observed by an optical photograph.

FIG. 6 is a diagram showing a surface state of an evaluation magnetic tape in which periodic waviness is not imparted to the surface of the reference example when observed by an optical photograph.

[Explanation of symbols]

1 ... base film, 2 ... magnetic layer, 3 ... protective layer,
4 ... Back layer, 5 ... Lubricant, 11 ... Exhaust port, 12
... vacuum chamber, 13 ... feed roll, 14 ... take-up roll, 16 ... cooling can, 17 ... guide roll, 18
... guide roll, 19 ... crucible, 20 ... Co ingot, 21 ... electron gun, 22 ... shutter, 24 ...
Oxygen gas inlet, 31 ... Base film for forming magnetic layer,
32 vacuum chamber, 33 feed roll, 34 take-up roll, 35 reaction tube, 36 electrode, 37 DC
Power supply 38 Guide roll 39 Counter electrode can 40 Vacuum exhaust system

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) G11B 5/85 G11B 5/85 A 5/851 5/851 F term (reference) 5D006 BB01 BB02 BB03 BB04 BB05 CB01 CB07 CC01 5D112 AA02 AA05 AA08 BA01 BA09 BB01 BB02 BB05 BD02 BD04

Claims (6)

[Claims] 1. A magnetic layer comprising a ferromagnetic metal thin film is formed on a nonmagnetic support comprising a base film, and a back layer is formed on a surface of the nonmagnetic support opposite to the surface on which the magnetic layer is formed. A magnetic recording medium comprising: a magnetic recording medium having periodic undulations on its surface. 2. The magnetic recording medium according to claim 1, wherein the waviness period is 10 to 500 μm. 3. The magnetic recording medium according to claim 1, wherein the amplitude of the waviness is 10 to 300 nm. 4. The magnetic recording medium according to claim 1, wherein the medium is a medium compatible with a magnetoresistive head. 5. A magnetic layer comprising a ferromagnetic metal thin film is formed on a non-magnetic support comprising a base film, and a back layer is formed on the surface of the non-magnetic support opposite to the surface on which the magnetic layer is formed. In the method for manufacturing a magnetic recording medium, in any step after the formation of the magnetic layer, the base film is run on a vacuum roll having pores to impart a desired periodic undulation to the surface. A method for manufacturing a magnetic recording medium. 6. A magnetic layer comprising a ferromagnetic metal thin film is formed on a non-magnetic support comprising a base film, and a back layer is formed on the surface of the non-magnetic support opposite to the surface on which the magnetic layer is formed. In the method for manufacturing a magnetic recording medium, in any step after the formation of the magnetic layer, the base film is sandwiched between rubber rolls to impart a desired periodic undulation to the surface, Method.