JP2003346327A - Metal thin-film type magnetic recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin metal thin-film type magnetic recording medium that has no defective large projections on the surface of a magnetic recording medium which can cause drop-outs or error rate, is superior in durability such as still characteristics and shuttle characteristics, and ready for a shorter wavelength in a magnetic recording and reproducing system and narrowing of a recording track pitch. <P>SOLUTION: A base layer 2 having a thickness 2 to 200 nm, comprising an Al metal oxide whose surface, is treated with an abrasive film to give an maximum surface roughness (Rmax) of 10 to 80 nm is formed, for example, on one main surface of a PET-made nonmagnetic base material 1. A magnetic layer 3 of Co metal magnetic thin film and a protective layer 4 of diamond-like carbon are formed on the base layer, and then a back coat layer 5 comprising carbon is formed on the other main surface of the nonmagnetic base material 1 on a opposite side to a surface, on which the magnetic layer 3 is formed. Then, the outermost surface is coated with a lubricant comprising fluorocarbons. <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 metal thin film type magnetic recording medium, and more particularly to a metal thin film type magnetic recording medium for high density magnetic recording having a thin magnetic tape and having high reliability and high durability. .

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording tape such as an audio tape and a video tape, a non-magnetic support is used.
Oxide magnetic powder or alloy magnetic powder, etc.
A so-called coating type magnetic recording medium obtained by applying a magnetic paint prepared by dispersing in various binders (binders) such as a vinyl acetate copolymer, a polyester resin, a urethane resin, and a polyurethane resin, followed by drying is provided. Widely known.

On the other hand, in response to recent demands for high-density recording, Co-Ni alloys, Co-Cr alloys,
A metal magnetic material such as o-O is plated on a non-magnetic support or directly through an extremely thin adhesive layer by using a vacuum thin film forming technique such as a vacuum deposition method, a sputtering method, or an ion plating method. There has been proposed a so-called metal thin film type magnetic recording medium in which a magnetic layer is formed by using a magnetic layer. Also, in order to improve the electromagnetic conversion characteristics as part of high-density recording and obtain a larger output, a method of forming a magnetic layer obliquely by oblique deposition has been proposed and put to practical use. Have been.

[0004] Such a metal thin film type magnetic recording medium has excellent coercive force and squareness, and since the magnetic layer can be formed in a very thin layer, it has excellent electromagnetic conversion characteristics in a short wavelength region, and has a recording demagnetization. And the thickness loss at the time of reproduction is remarkably small, and further, unlike the coating type magnetic recording medium, since the binder which is a nonmagnetic material is not mixed into the magnetic layer, the packing density of the ferromagnetic metal particles can be increased. It has various advantages.

In the above-described metal thin-film type magnetic recording medium, the magnetic layer is protected from severe sliding conditions, a protective layer is formed to improve durability and running properties, and the magnetic layer forming surface is not formed. It is common practice to form a back coat layer on the opposite surface, but it is necessary to further reduce the thickness (thinning) of the magnetic tape due to the demand for higher density and smaller devices. ing.

On the other hand, in the metal thin film type magnetic recording medium, the surface tends to be further smoothed in order to reduce spacing loss corresponding to high density recording. However, when the surface of the magnetic layer becomes smooth, the contact area with the magnetic head increases, the frictional force increases, and the shear stress generated on the magnetic layer increases, so it is essential to provide an appropriate roughness to the surface. It is.

[0007] In order to impart an appropriate roughness to the surface, for example, fine particles having a controlled particle size and number of particles are mixed into a support of a magnetic recording medium to form small projections on the surface to control the surface property. There are ways to do that. The surface properties (surface roughness) of the non-magnetic support of the magnetic recording medium affect various characteristics of the magnetic tape, such as the electromagnetic conversion characteristics and friction coefficient.
Various methods have been devised, but the method of designing the surface of a magnetic tape by mixing particles in a non-magnetic support is based on the formation of abnormal projections outside the design due to the aggregation of particles and the uneven distribution of particles due to the uneven distribution of particles. There are many disadvantages, such as unevenness in properties. As described above, while the surface properties of the magnetic tape are in the direction of becoming increasingly smooth, especially surface defects such as undesigned protrusions,
This is a major factor that hinders magnetic recording systems.

As a measure for eliminating surface defects, after forming a magnetic layer or after forming a protective film layer on the magnetic layer, a surface treatment (U / T Processing). This processing removes sudden projections and the like that become surface defects, and improves dropout and error rate. However, if such treatment is performed after the formation of the magnetic layer or the protective film, the surface of the magnetic recording medium will be finely scratched, and although the dropout and error rate as the initial characteristics are improved, the still characteristics and the shuttle characteristics are improved. Improvements are desired because they also cause deterioration of durability such as characteristics.

Under the circumstances described above, progress in increasing the recording density has been remarkable in recent years, and magnetic recording media are required to have even higher performance such as strict durability and electromagnetic conversion characteristics. In particular, due to the shorter recording wavelength and the narrower recording track pitch accompanying higher recording density, even small defects are now affecting dropouts and error rates. Is becoming indispensable.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to eliminate large projection defects on the surface of a magnetic recording medium that cause dropouts and error rates. A thin metal thin film type that can respond to shorter wavelengths of magnetic recording / reproducing systems and narrower recording track pitch while maintaining high durability such as still characteristics and shuttle characteristics by providing appropriate surface roughness. An object of the present invention is to provide a magnetic recording medium and a method for manufacturing the same.

[0011]

According to the present invention, there is provided a magnetic recording medium of a metal thin film type, wherein an underlayer having a maximum surface roughness of an underlayer is provided on a non-magnetic support, and a magnetic layer is formed thereon. By successively molding, the surface flatness and the roughness state of the recording medium are controlled in a well-balanced manner, while improving the dropout and error rate, while maintaining the durability such as still characteristics and shuttle characteristics, An object of the present invention is to provide a metal thin-film magnetic recording medium having good electromagnetic conversion characteristics and a method of manufacturing the same, which can cope with a shorter wavelength and a narrower recording track pitch of a magnetic recording and reproducing system. Hereinafter, the present invention will be described specifically.

According to a first aspect of the present invention, an underlayer made of a metal material selected from metals, metalloids and alloys, and oxides and composites thereof, and a magnetic layer are sequentially formed on a nonmagnetic support. Wherein the underlayer has a maximum surface roughness (Rmax) of 10 to 80 nm.

The maximum surface roughness (Rmax) of the underlayer is 10 to
By setting the thickness to 80 nm, large protrusions and the like are not transferred to the surface of the magnetic recording medium composed of each layer such as a thin magnetic layer provided on the underlayer, so that dropout and error rate are reduced, and Flatness and roughness are controlled in a well-balanced manner, while maintaining high durability such as still characteristics and shuttle characteristics, with good sliding characteristics and running characteristics, shortening the wavelength of the magnetic recording / reproducing system, and narrowing the recording track pitch. The present invention provides a thin metal thin-film magnetic recording medium having a high recording density and capable of responding to the development of a thin film.

According to a second aspect of the present invention, the thickness of the underlayer is:
2. The metal thin-film magnetic recording medium according to claim 1, wherein the thickness is 2 to 200 nm.

By setting the thickness of the underlayer to 2 to 200 nm, the surface flatness and the state of roughness are controlled in a well-balanced manner, together with the adjustment of the maximum surface roughness (Rmax) of the underlayer. A metal thin-film magnetic recording medium for high-density recording that can cope with thinning is provided.

The invention according to claim 3 is a step of forming an underlayer made of a metal material selected from metals, metalloids and alloys, and oxides and composites thereof on a nonmagnetic support; A step of treating the surface with an abrasive film to make the maximum surface roughness (Rmax) of the underlayer 10 to 80 nm, and then forming a magnetic layer on the underlayer by a vacuum thin film forming technique. A method for manufacturing a metal thin-film type magnetic recording medium, characterized in that:

The production method according to claim 3 is suitably applied, for example, when the surface roughness is imparted by mixing particles in a non-magnetic support. By subjecting the surface of the underlayer to a polishing film before the formation of the magnetic layer, sudden projections and the like that become surface defects are removed, and the maximum surface roughness (Rmax) is 10 to 80 n.
By adjusting to m, the good surface condition of the underlayer after the formation of the magnetic layer is transferred and reflected on the surface of the magnetic recording medium, and a metal thin film magnetic recording medium free from defects such as abnormal projections is provided. By such a manufacturing method, dropout and error rate are improved, and durability such as still characteristics and shuttle characteristics is improved.

According to a fourth aspect of the present invention, an underlayer made of a metal material selected from metals, metalloids and alloys, and oxides and composites thereof is provided on a nonmagnetic support. And a step of forming a magnetic layer on the underlayer by a vacuum thin film forming technique, the step of adjusting the film forming conditions so that the thickness (Rmax) is 10 to 80 nm. This is a method for manufacturing a metal thin-film magnetic recording medium.

The production method according to the fourth aspect is suitably applied, for example, when a smooth surface is formed without mixing particles or the like into a nonmagnetic support. The surface condition is transferred and reflected on the surface of the magnetic recording medium because the underlayer is formed by adjusting the film forming conditions, and there is no unevenness in the surface roughness (Ra: root mean square roughness) and the maximum surface roughness. The surface roughness (Rmax) was also controlled to 10 to 80 nm, the surface was not too flat, the contact area with the magnetic head was not increased, the frictional force was not excessively increased, and the surface flatness and roughness were controlled in a well-balanced manner. A method for manufacturing a metal thin film type magnetic recording medium is provided. By such a manufacturing method, dropout and error rate are improved, and sliding characteristics and running properties are good, and durability such as still characteristics and shuttle characteristics is improved.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The metal thin film type magnetic recording medium of the present invention is formed on a non-magnetic support as described above by using a metal material selected from metals, metalloids and alloys, and oxides and composites thereof. By providing an underlayer with an adjusted maximum surface roughness (Rmax) and sequentially forming constituent layers such as a magnetic layer on the underlayer by a vacuum thin film forming technique, the surface flatness and the roughness of the recording medium are obtained. Is appropriately controlled.

Since the magnetic layer and the protective layer are thin, the surface roughness of the recording medium reflects the surface roughness of the underlying base material, and the irregularities are transferred. The underlayer of the present invention is provided in order to make the surface roughness state on the magnetic layer side appropriate, thereby improving the dropout and the error rate, and improving the durability such as the still characteristics and the shuttle characteristics. Is improved. An example of the layer configuration of such a metal thin-film magnetic recording medium is shown in the schematic sectional view of FIG. The metal thin-film magnetic recording medium of the present invention is not limited to the following embodiments, and may take various other configurations without departing from the gist of the present invention.

As illustrated in FIG. 1, a metal thin-film magnetic recording medium 6 of the present invention comprises a non-magnetic support 1, a metal, a metalloid, an alloy, and a metal on one main surface of the non-magnetic support 1. An underlayer 2 having a maximum surface roughness (Rmax) adjusted from a metal material selected from oxides and composites, and a magnetic layer 3 comprising a metal magnetic thin film formed on the underlayer 2
And a protective layer 4 formed on the surface of the magnetic layer 3 and a back coat layer 5 formed on the other main surface of the non-magnetic support 1 opposite to the surface on which the magnetic layer 3 is formed. It is composed. Hereinafter, each constituent layer will be described in more detail.

The material forming the underlayer 2 is a metal material selected from metals, metalloids and alloys, and oxides and composites thereof as described above. Such materials include Al, Cu, Zn, Sn, Ni, Ag, Co, F
e, metal such as Mn, or Si, Ge, As, Sc, S
Metals such as b and oxides of the metals and metalloids can be used. Further, alloys of these metals and metalloids include Fe-Co, Fe-Ni, Co-Ni, Fe-C
u, Co-Cu, Co-Au, Co-Y, Co-La,
Co-Pr, Co-Gd, Co-Sm, Co-Pt, N
i-Cu, Mn-Bi, Mn-Sb, Mn-Al, Fe
-Cr, Co-Cr, Ni-Cr, Fe-Co-Cr,
Ni-Co-Cr and the like, and oxides of these metals, metalloids, and alloys can be easily obtained by introducing oxygen gas at the time of vapor deposition for forming an underlayer by, for example, a vacuum thin film forming technique. Further, composites of these metals, metalloids and alloys include Fe-Si-O, Si-C, Si-N, Cu
-Al-O, Si-NO, Si-CO, and the like. The purpose of the underlayer 2 is to control the maximum surface roughness of the surface of the recording medium as described above, and may be a magnetic metal as long as it does not affect the medium characteristics.

The underlayer 2 is formed by a vacuum thin film forming technique before the magnetic layer 3 is formed. The thickness of the underlayer 2 depends on the controllability of the surface roughness of the recording medium and the thickness of the recording medium. 2 to 200 in consideration of thinning or productivity
nm. For the above reason, the underlayer 2 has a maximum surface roughness (Rmax) of 10 to 80 n before the magnetic layer 3 is formed by forming a vacuum thin film.
m so as to remove the abnormal surface roughness of the underlayer so that defects are not transferred or reflected.

In order to make the maximum surface roughness (Rmax) of the underlayer 2 appropriate, when forming the underlayer 2,
The maximum surface roughness (Rmax) is set to 1 while controlling the film forming conditions so that the surface roughness (Ra: root mean square roughness) is not uneven.
Adjusting to 0 to 80 nm, or after forming the underlayer 2, treating the surface of the underlayer 2 with a polishing film to adjust the maximum surface roughness (Rmax) to 10 to 80 nm. Can be done by Regarding the surface treatment after the formation of the underlayer 2, the surface treatment can be performed using an abrasive film (abrasive tape) such as a GC polishing film or a WA polishing film.

If the maximum surface roughness (Rmax) of the underlayer 2 is smaller than 10 nm, the surface becomes too flat, the friction coefficient increases rapidly, and the shear stress of the magnetic layer in the sliding increases, resulting in deterioration. Occurs. On the other hand, the maximum surface roughness (R
If (max) is larger than 80 nm, there is a problem in that dropout occurs, an error rate increases sharply, and the reliability as a magnetic recording medium is significantly reduced.

The underlayer 2 can be formed by a sputtering method, an ion plating method, or the like, in addition to the vacuum evaporation method. By the vacuum deposition method using the vapor deposition apparatus 10 shown in the schematic configuration diagram of FIG. 2, the layer configuration shown in FIG.
The deposition process will be described by taking as an example the case where the underlayer 2 made of a metal oxide is formed.

<Film Forming Process by Vapor Deposition Apparatus> In the vapor deposition apparatus 10, a feed roll 13 and a take-up roll 14 are provided in a vacuum chamber 11 which is evacuated from the exhaust ports 21 and 22 to a vacuum state. The non-magnetic support 1 travels sequentially between them. Between the feed roll 13 and the take-up roll 14,
While the non-magnetic support 1 is running, the cooling can 1
5 are provided. The cooling can 15 is provided with a cooling device (not shown) to suppress a thermal deformation or the like due to a temperature rise of the nonmagnetic support 1 running on the peripheral surface.

The non-magnetic support 1 is sequentially fed from a feed roll 13, passes through a cooling can 15, and is wound on a take-up roll 14. A predetermined tension is applied to the non-magnetic support 1 by the guide rolls 16 and 17, so that the non-magnetic support 1 runs smoothly.

In the vacuum chamber 11, a crucible 18 is provided below the cooling can 15, and the crucible is filled with an Al metal magnetic material 19. On the other hand, on the side wall of the vacuum chamber 11, an electron gun 20 for heating and evaporating the Al metal magnetic material 19 filled in the crucible 18 is provided. The electron gun 20 emits an electron beam B
Is disposed at a position where the Al metal magnetic material 19 in the crucible 18 is irradiated. Further, oxygen gas is supplied to the surface of the non-magnetic support 1 from an oxygen gas introduction pipe 24 provided through the side wall of the vacuum chamber 11, and the oxygen gas is evaporated by irradiation with the electron beam B. Al
The metal magnetic material 19 is deposited as a metal oxide on the surface of the non-magnetic support 1 to form the underlayer 2. The shutter 23 in FIG. 2 is a cover for limiting an incident angle range due to oblique vapor deposition in forming a magnetic layer 3 described later.

Nonmagnetic support 1 on which magnetic layer 2 is formed
Any known material that is usually used as a base material of a magnetic tape can be used. For example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytetramethylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene 2,6-naphthalene dicarboxylate, polyethylene-p-oxybenzoate, etc. Can be mentioned. Particularly, polyethylene terephthalate (PET), polyethylene naphthalate (PE)
N) is preferred from the viewpoint of easy availability of materials and good workability. Further, these polyesters may be homopolyesters or copolyesters.

A polyethylene terephthalate film (PET) is mainly used as a non-magnetic support of the conventional metal thin film type magnetic recording medium. Particularly, for a home video cassette tape, for example, for an 8 mm tape,
PET having a thickness of about 7 to 10 μm is used, and PET having a thickness of about 5 to 7 μm is used for a tape streamer for data backup of a computer. In general, mechanical strength is maintained and running stability is secured by using a film having a thickness of about 5 to 15 μm.
According to the layer structure provided with the underlayer 2 of the present invention, the mechanical strength can be improved, so that the nonmagnetic support 1 can be made thin. For example, a nonmagnetic support having a thickness of about 5 to 6 μm is used. can do.

Next, the magnetic layer 3 has a maximum surface roughness (Rma
It can be formed by directly applying a ferromagnetic metal material on the surface of the underlayer 2 in which x) is adjusted to 10 to 80 nm. As such a ferromagnetic metal material, any of conventionally known metals and alloys can be used. For example, ferromagnetic metals such as Fe, Co, and Ni, Co-Ni, F
e-Co, Fe-Co-Ni, Fe-Cu, Co-C
u, Cb-Au, Co-Pt, Mn-Bi, Mn-A
1, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co
Ferromagnetic alloys such as -Cr, Co-Ni-Cr, and Fe-Co-Ni-Cr;

The magnetic layer 3 may be a single-layer film of the ferromagnetic metal material or a multilayer film. The vicinity of the surface of the magnetic layer 3 may be made of an oxide in order to improve corrosion resistance and the like. Further, between the underlayer 2 and the magnetic layer 3 or between the metal magnetic thin films in the case of a multilayer film, the intermediate layer is made of Cr or the like to improve the adhesion between the layers and control the coercive force. It may be formed.

The magnetic layer 3 is formed by a vacuum evaporation method in which a ferromagnetic material is heated and evaporated under vacuum to adhere thereto, an ion plating method in which a ferromagnetic metal material is evaporated in a discharge, or an atmosphere containing argon as a main component. It can be formed by a so-called PVD technique such as a sputtering method in which atoms on the target surface are beaten by argon ions generated by causing glow discharge.

When the magnetic layer 3 is formed by a vacuum evaporation method, it can be formed, for example, by using the evaporation apparatus 10 shown in FIG. That is, a metal magnetic material, for example, C
o, and this is irradiated with an electron beam B from the electron gun 20,
The evaporated metal material of Co adheres to the surface of the underlayer 2 formed on one main surface of the nonmagnetic support 1 under the introduction of oxygen,
A magnetic layer 3 made of a Co metal magnetic thin film having improved magnetic properties, durability, and weather resistance is formed.

At the time of vapor deposition, as described above, the cooling can 1
A shutter 23 is disposed in the vicinity of the cooling can 15 between the crucible 5 and the crucible 18 so as to cover a predetermined area of the non-magnetic support 1 on which the underlayer 2 running on the peripheral surface of the cooling can 15 is formed. The evaporated Co is vapor-deposited obliquely within a predetermined incident angle range with respect to the underlayer 2 on the nonmagnetic support 1.

Next, a protective layer 4 is formed on the surface of the magnetic layer 3 in order to secure good corrosion resistance and running durability. As a material for forming the protective layer 4, any conventionally known material generally used for a protective layer for a metal magnetic thin film can be used. Such materials include, for example, carbon, CrO ₂ , Al ₂ O ₃ , BN,
Co oxide, MgO, SiO ₂ , Si ₃ O ₄ , SiN _{x
SiN x, SiC, SiN x -SiO} 2, ZrO 2, T
iO _2, TiC, mention may be made of the MoS and the like. The protective layer 4 may be a single-layer film or a multilayer film of the above materials, and these may be formed by a known vacuum film forming technique such as a CVD method or a sputtering method.

Among the various materials described above, when the protective layer 4 is formed of a carbon base material, it is excellent in durability, corrosion resistance and productivity. For example, as a vacuum film forming technique for forming the protective layer 4 made of such a carbon base material,
A CVD method in which a carbon compound is decomposed in plasma to form a film can be used. According to the CVD method, it is possible to form a hard carbon film made of diamond-like carbon (diamond-like carbon) having excellent abrasion resistance, corrosion resistance, surface coverage, a smooth surface shape and a high electric resistivity, A film can be stably formed to a thickness of 10 nm or less. If the thickness of the protective layer 4 is too large, the loss due to spacing increases, and if it is too thin, the abrasion resistance and corrosion resistance deteriorate. Therefore, the protective layer 4 should be formed to a thickness of about 4 to 12 nm. Is desirable.

In the case of the CVD method, any of conventionally known materials such as hydrocarbons, ketones and alcohols can be used as the carbon compound. Further, a high frequency bias voltage may be used to decompose in the plasma, and Ar, H _2, or the like may be introduced as a gas for promoting the decomposition of the carbon compound at the time of plasma generation. Alternatively, in order to improve the film hardness and corrosion resistance of diamond-like carbon, carbon may be in a state of reacting with nitrogen and fluorine, and the diamond-like carbon film may be a single layer or a multilayer. Also,
At the time of plasma generation, N ₂ , CHF ₃ ,
It is also possible to form a film by introducing a gas such as CH ₂ F ₂ alone or in an appropriately mixed state. Hereinafter, a film forming process will be described by taking as an example a case where the protective layer 4 is formed using the plasma CVD continuous film forming apparatus 30 shown in the schematic configuration diagram of FIG.

<Film Forming Process by Plasma CVD Continuous Film Forming Apparatus> The plasma CVD continuous film forming apparatus 30 is a vacuum chamber 31 which is evacuated from an exhaust system 32 to be in a vacuum state.
Inside, a feed roll 33 and a take-up roll 34 are provided, and the feed roll 33 and the take-up roll 34
An object to be processed 27 in which an underlayer 2 and a magnetic layer 3 are sequentially formed on the non-magnetic support 1 runs sequentially. A cylindrical rotatable counter electrode can 35 is provided in the middle of the movement of the object 27 from the feed roll 33 to the take-up roll 34.

The object to be processed 27 is sequentially sent out from the feed roll 33, passes through the peripheral surface of the counter electrode can 35, and is taken up by the take-up roll 34. Guide rolls 36 are arranged between the feed roll 33 and the counter electrode can 35 and between the counter electrode 35 and the take-up roll 34, respectively.
A predetermined tension is applied to 7 so that the object to be processed 27 runs smoothly.

Further, below the counter electrode can 35,
For example, a reaction tube 37 made of Pyrex glass (registered trademark), plastic, or the like is provided. The reaction tube 37 has an end penetrating the bottom of the vacuum chamber 31, and a film forming gas is introduced into the reaction tube 37 from the discharge gas inlet 28 at the end. Further, an electrode 38 made of a metal mesh or the like is incorporated in the reaction tube 37. A predetermined potential, for example, 500 to 200, is applied to the electrode 38 by a DC power supply 39 provided outside.
A voltage of 0 V is applied.

In the plasma CVD continuous film forming apparatus 30 having the above-described structure, a glow discharge is generated between the electrode 38 and the counter electrode can 35 by applying a voltage to the electrode 38. Then, the film-forming gas introduced into the reaction tube 37 is decomposed by the generated glow discharge, and
7.

Next, as shown in FIG. 1, a back coat layer 5 is formed on the other main surface of the non-magnetic support 1 opposite to the surface on which the magnetic layer 3 is formed. This back coat layer 5
Reduce the electric resistance of the surface of the non-magnetic support 1 to prevent running defects due to charging, improve the durability of the non-magnetic support 1 and protect it from scratches caused by friction with the head during running, It has a function of protecting it from friction between magnetic tapes.

The material for forming the back coat layer 5 may be any material that is generally used for the back coat layer, and examples thereof include carbon, metal oxides, carbides, and nitrides. . The back layer 5 may be a single layer film of the above-mentioned material or a multilayer film. The back coat layer 5 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 film forming process will be described by taking as an example a case where the film is formed using the magnetron sputtering apparatus 40 shown in FIG.

<Film Forming Process by Magnetron Sputtering Apparatus> In the magnetron sputtering apparatus 40 shown in the schematic configuration diagram of FIG. 4, a supply roll 41 and a take-up roll 42 are placed in a chamber 44 evacuated by a vacuum pump 43. Are provided, and these supply rolls 41 are provided.
And a take-up roll 42 on which a base layer 2, a magnetic layer 3, and a protective layer 4 are formed on one main surface of the nonmagnetic support 1.
5 run sequentially so that the back coat layer 5 is formed on the other main surface of the non-magnetic support 1. In the middle of the movement of the object 45 from the supply roll 41 to the take-up roll 42, a cylindrical rotatable cooling can 46 for the counter electrode is provided.

Guide rolls 47 are arranged between the supply roll 41 and the cooling can 46 and between the cooling can 46 and the take-up roll 42, respectively. The processing object 45 runs smoothly.

A target 48 is provided in the chamber 44 at a position facing the cooling can 46. The target 48 is a material of the back coat layer 5 and, for example, carbon is used. These targets 48 are supported on a backing plate 49 constituting a cathode electrode. On the back surface of the backing plate 49, a magnet 50 for forming a magnetic field is provided.

In the magnetron sputtering apparatus 40, the pressure inside the chamber 44 is reduced by a vacuum pump 43 to a degree of vacuum suitable for forming the back coat layer 5.
The exhaust speed is controlled by adjusting the valve 51 for exhausting to the vacuum pump 43 side. On the other hand, A
The degree of vacuum is maintained at, for example, about 0.8 by introducing r gas.

Then, while introducing Ar gas from the gas introduction pipe 52, a voltage of about 3000 V is applied using the cooling can 46 as an anode and the backing plate 49 as a cathode, and a state in which a current of about 1.4 A flows is maintained. .
Then, by applying the voltage, the Ar gas is turned into plasma, and the ionized ions collide with the target 48, whereby atoms are repelled from the material.

At this time, since a magnetic field is formed near the target 48 by the magnet 50 arranged on the back surface of the backing plate 49, the ionized ions are
It will be concentrated near the target 48. The atoms repelled from these targets 48 adhere to the processing target 45 traveling along the outer peripheral surface of the cooling can 46. The object 45 on which the back coat layer 5 has been formed in this manner is wound up by the winding roll 42.

Further, the metal thin film type magnetic recording medium 6 of the present invention
In this case, it is desirable to coat a lubricant, a rust inhibitor and the like on the outermost surface layer on the side on which the magnetic layer 3 is formed and on the side opposite to the side on which the magnetic layer 3 is formed.

[0054]

EXAMPLES In the following, the metal thin film type magnetic recording medium of the present invention is formed by polishing the surface thereof with a polishing film (polishing tape) after forming an underlayer to adjust the maximum surface roughness (Rmax) (A), and The case (B) where the maximum surface roughness (Rmax) of the surface is adjusted by controlling the film forming conditions of the underlayer forming process will be specifically described with reference to Examples and Comparative Examples. The thin-film magnetic recording medium is not limited to the following examples.

<A case of adjusting the maximum surface roughness (Rmax) by polishing the surface after forming the underlayer (A)> Example A1 As a nonmagnetic support, a 6 μm-thickness containing SiO ₂ powder was used.
A polyethylene naphthalate having a width of 150 mm was prepared, and an underlayer 62 and a magnetic layer 6 were formed on the surface of the nonmagnetic support made of polyethylene naphthalate in a layer configuration shown in the schematic diagram of FIG.
3. A protective layer 64 is sequentially formed, and a lubricant 65 and a lubricant 66 are formed.
Coated with metal thin film type magnetic recording medium (Magnetic tape)
Was prepared. In the above configuration, the underlayer 62 is an oxide of Al metal, and after forming the underlayer 62, treating the surface with a polishing tape, then forming a magnetic layer 63 made of a Co metal magnetic thin film on the underlayer 62, A protective layer 64 made of diamond-like carbon was formed on the surface, and a lubricant was applied to the outermost surfaces on both surfaces of the nonmagnetic support 61 on which these layers were formed. The maximum surface roughness (Rmax) of the obtained magnetic tape raw material was 50 nm. The main manufacturing conditions of each constituent layer of the manufactured magnetic tape raw material are shown below.

[Formation of Underlayer] Evaporation apparatus 1 shown in FIG.
0, the crucible 18 is filled with Al under the following film-forming conditions, and a film is formed by introducing oxygen by a vacuum evaporation method to form the non-magnetic support 1 (the non-magnetic support 61 shown in FIG. 5). Equivalent)
Was formed on one main surface of the substrate.

<Deposition condition of underlayer> Material for vapor deposition: Al (100 wt%) Introduced gas: oxygen gas Oxygen introduced amount: 4.5 × 10 ^-6 m ³ / sec Vacuum degree during vapor deposition: 2.0 × 10 ⁻² Pa Film thickness of underlayer: 10 nm

Next, the surface of the underlayer 62 made of an oxide of Al formed on one main surface of the nonmagnetic support 61 is subjected to a maximum surface roughness (polishing tape) under the following surface treatment conditions using a polishing film (polishing tape). Rmax) was about 50 nm.

<Surface treatment conditions> Polishing film: WA # 4000 Holding angle: 30 ° Processing tension: 1.5kg

[Formation of Magnetic Layer] Next, the underlayer 62
After the surface is treated, a magnetic layer 63 composed of a Co metal magnetic thin film is formed on the surface of the underlayer 62 by introducing oxygen under the following evaporation conditions by a vacuum evaporation method using the evaporation apparatus 10 shown in FIG. did.

<Film formation conditions of magnetic layer> Metal magnetic material: Co (100 wt%) Incident angle: 45 ° to 10 ° Introduced gas: oxygen gas Oxygen introduction amount: 3.3 × 10 ⁻⁶ m ³ / sec During vapor deposition Degree of vacuum: 2 × 10 ⁻² Pa Film thickness of magnetic layer: 80 nm

[Formation of Protective Layer] Next, on the surface of the magnetic layer 63 formed on the underlayer 62 of the nonmagnetic support 61,
Using the plasma CVD continuous film forming apparatus 30 shown in the schematic configuration diagram of FIG. 3, a protective layer 64 made of diamond-like carbon was formed by a plasma CVD method under the following film forming conditions.

<Deposition condition of protective layer> Reaction gas: toluene Reaction gas pressure: 10Pa Introduced power: Direct current (DC) 1.5kV Film thickness of carbon protective layer: 10 nm

[Application of Lubricant] As described above, the magnetic layer forming surface side of the tape in which the underlayer 62, the magnetic layer 63, and the protective layer 64 are formed on one main surface of the nonmagnetic support 61 and the magnetic layer On each outermost surface with the other main surface opposite to the layer forming surface,
Lubricants 65 and 66 were applied to produce a raw magnetic tape having a maximum surface roughness (Rmax) of 50 nm on the surface of the magnetic layer 63. As the lubricant, any one can be used as long as it is generally used as a magnetic tape application.In particular, the main skeleton is preferably a fluorocarbon type, an alkylamine, or an alkyl ester. A perfluoropolyether-based lubricant was applied. The magnetic tape raw material obtained as described above was cut into a 6.35 mm width to obtain a sample magnetic tape for evaluation of Example A1.

Example A2 In Example A1, the thickness of the underlayer 62 was 10 nm.
However, the underlayer 62 was formed by a vacuum evaporation method in the same manner as in Example A1, except that the film thickness was changed to 2 nm by changing the film formation rate of the underlayer 62, and the surface was treated with a polishing tape. After that, a magnetic layer 63 and a protective layer 64 are formed, and a lubricant 65,
66. 6.35 mm
It was cut into a width to obtain a sample magnetic tape for evaluation of Example A2.

Example A3 In Example A1, the thickness of the underlayer 62 was 10 nm.
However, the underlayer 62 was formed by a vacuum evaporation method in the same manner as in Example A1, except that the film thickness was changed to 20 nm by changing the film formation rate of the underlayer 62, and the surface was treated with a polishing tape. After that, the magnetic layer 63 and the protective layer 64 are formed, and the lubricant 6
The magnetic tape raw material obtained by coating Nos. 5, 66 was 6.35.
It was cut to a width of mm to obtain a sample magnetic tape for evaluation of Example A3.

Embodiment A4 In the embodiment A1, the film thickness of the underlayer 62 is 10 nm.
However, except that the film formation rate of the underlayer 62 was changed to change the film thickness to 100 nm, the underlayer 62 was formed by a vacuum evaporation method in the same manner as in Example A1, and the surface was treated with a polishing tape. After that, the magnetic layer 63 and the protective layer 64 are formed, and the lubricant 6
The magnetic tape raw material obtained by coating Nos. 5, 66 was 6.35.
It was cut to a width of mm to obtain a sample magnetic tape for evaluation of Example A4.

Embodiment A5 In the embodiment A1, the thickness of the underlayer 62 is 10 nm.
However, except that the film formation rate of the underlayer 62 was changed to change the film thickness to 200 nm, the underlayer 62 was formed by a vacuum evaporation method in the same manner as in Example A1, and the surface treatment was performed with a polishing tape. After that, the magnetic layer 63 and the protective layer 64 are formed, and the lubricant 6
The magnetic tape raw material obtained by coating Nos. 5, 66 was 6.35.
It was cut to a width of mm to obtain a sample magnetic tape for evaluation of Example A5.

Reference Example A1 The same procedure as in Example A1 was carried out except that the underlayer 62 was not formed and one main surface of the nonmagnetic support surface 61 on which the magnetic layer 63 was formed was treated with a polishing tape. A magnetic layer 63 and a protective layer 64 are formed in the same manner as described above.
The obtained magnetic tape was cut into a 6.35 mm width to obtain a sample magnetic tape for evaluation of Comparative Example A1. In this case, scratches occurred on the surface of the nonmagnetic support 61 in the surface treatment step using a polishing tape performed before the formation of the magnetic layer 63.

Reference Example A2 In Example A1 except that the underlayer 62 was not formed, and that one surface of the nonmagnetic support surface 61 on which the magnetic layer 63 was formed was not subjected to surface treatment with a polishing tape. ,
An evaluation sample of Reference Example A2 was prepared by forming a magnetic layer 63 and a protective layer 64 in the same manner as in Example A1, applying a lubricant 65, 66, and cutting a magnetic tape raw material to a width of 6.35 mm. Magnetic tape was used.

Reference Example A3 In Example A1, the surface of the protective layer 64 was polished after the formation of the protective layer 64, instead of forming the base layer 62 and replacing the surface treatment with a polishing tape before forming the magnetic layer 63. Except that the surface treatment was performed with a tape, a magnetic layer 63 and a protective layer 64 were formed in the same manner as in Example A1, and a magnetic tape raw material obtained by applying lubricants 65 and 66 was cut into a 6.35 mm width. The evaluation sample magnetic tape of Reference Example A3 was used.

Reference Example A4 In the above-mentioned Example A1, the thickness of the underlayer 62 was 10 nm.
However, except that the film formation rate of the underlayer 62 was changed to change the film thickness to 1 nm, the underlayer 62 was formed by a vacuum evaporation method in the same manner as in Example A1, and the surface was treated with a polishing tape. After that, a magnetic layer 63 and a protective layer 64 are formed, and a lubricant 65,
66. 6.35 mm
It was cut into a width to obtain a sample magnetic tape for evaluation of Reference Example A4.

Reference Example A5 In the above-described Example A1, the thickness of the underlayer 62 was 10 nm.
However, the underlayer 62 was formed by a vacuum evaporation method in the same manner as in Example A1, except that the film thickness was changed to 300 nm by changing the film forming rate of the underlayer 62, and the surface was treated with a polishing tape. After that, the magnetic layer 63 and the protective layer 64 are formed, and the lubricant 6
The magnetic tape raw material obtained by coating Nos. 5, 66 was 6.35.
The sample was cut into a width of mm to obtain a sample magnetic tape for evaluation of Reference Example A5.

For each of the evaluation sample magnetic tapes of Examples A1 to A5 and Reference Examples A1 to A5 prepared as described above, the maximum surface roughness (R
max) and magnetic tape characteristics (error rate, dropout, per head) were measured and evaluated under the following evaluation conditions. Table 1 shows the results.

<Evaluation Conditions> Maximum surface roughness (Rmax): A range of 30 μm square was measured using SPM (Nanoscope III D-300) manufactured by Digital Instrument. Magnetic tape characteristics: DV deck DHR manufactured by Sony Corporation
The following items were evaluated using a modified version of -1000 (trade name). (1) Error rate; 80 minutes length is 10 as running durability
The vehicle was run on 0 passes, and the block error rate after running on 1 pass and the error rate after running on 100 passes were measured. (2) Dropout: A 10 μsec dropout was counted for 10 minutes and measured. (3) Head hitting: The hitting property with the head was evaluated based on the minimum value / maximum value (%) of the output when the output signal (hitting waveform) during tape reproduction was viewed for one track.

[0076]

[Table 1]

Evaluation Results As shown in Table 1, an underlayer 62 made of Al oxide was formed to a thickness of 2 to 200 nm, and the surface thereof was surface-treated with a polishing tape to control the maximum surface roughness (Rmax).
Examples A1 according to the present invention provided with each layer such as the magnetic layer 63
The underlayer 62 was formed on the surface of the sample magnetic tape of Example A5.
There are no sudden large protrusions on the tape, so no abnormal defects are transferred and the maximum surface roughness (Rmax) of the magnetic tape
Of about 50 nm, good head contact, improved error rate and dropout, and excellent durability.

On the other hand, without forming the underlayer 62, the magnetic layer 63
The magnetic tape of Reference Example A1, in which the surface of the non-magnetic support 61 was polished before formation, had a scratch formed on the non-magnetic support 61 having a low hardness as a result of the surface treatment with the polishing tape. The surface roughness became large, and the characteristics such as head contact, error rate, and dropout were deteriorated.

The magnetic tape of Reference Example A2 was a sample magnetic tape in which the underlayer 62 was not formed and the surface treatment of the nonmagnetic support 61 was not performed. The protrusions of the body 61 remained, and the defects were reflected on the surface, and the surface roughness was large, resulting in poor characteristics such as head contact, error rate, and dropout.

Further, without forming the underlayer 62, the protective layer 64
The surface roughness of the sample magnetic tape of Reference Example A3 in which the surface treatment was performed after the formation of the magnetic tape was reduced, and the initial error rate and dropout were improved by performing the surface treatment of the magnetic tape. It can be seen that the error rate is worse and the durability is worse.
This is because, as a result of performing the surface treatment after forming the protective layer 64, large projections that cause dropout or the like are removed. However, the protective layer 64 is shaved by the surface treatment to have a reduced thickness. This is because they have hurt themselves.

In the case of Reference Example A4 in which the thickness of the underlayer 62 is 1 nm, the effect of removing large projections by the surface treatment is low because the thickness is too small. As a result, the maximum surface roughness (Rmax) was also 70 nm, which was larger than that of the embodiment,
It is not enough for dropout and error rate improvement. On the other hand, in the case of Reference Example A5 in which the thickness of the underlayer 62 was 300 nm, the thickness of the magnetic tape was too large, and the rigidity of the magnetic tape was increased, which adversely affected the head contact characteristics. From the above results, it can be said that the thickness of the underlayer is preferably 2 to 200 nm in consideration of performance, durability, reliability, productivity, and the like as a magnetic recording medium.

<Case where the maximum surface roughness (Rmax) of the underlayer is adjusted by adjusting the film forming conditions (B)> Examples B1 to B5 In the above example (A), as shown in Table 2, In addition to using the apparatus 10 to set the thickness of the underlayer made of Al metal oxide to a predetermined thickness and controlling the amount of oxygen introduced to adjust the surface roughness and the maximum surface roughness (Rmax), Under the same layer structure and manufacturing conditions as in Example (A), an underlayer 62 is formed on the surface of a polyethylene naphthalate nonmagnetic support 61 having a thickness of 6 μm and a width of 150 mm and containing no fine particles for forming surface protrusions. , Magnetic layer 63, protective layer 64
Are sequentially formed, a lubricant 65 and a lubricant 66 are applied to produce a metal thin film type magnetic recording medium (raw magnetic tape), and the obtained raw magnetic tape is cut into a 6.35 mm width. Sample magnetic tapes for evaluation of B1 to B5 were used.

Comparative Example B1 As shown in Table 2 below, a non-magnetic support made of polyethylene naphthalate mixed with fine particles for forming surface projections was used, and the conditions were not set to form the underlayer 62. A sample magnetic tape for evaluation of Comparative Example B1 was produced in the same manner as in Examples B1 to B5.

[0084]

[Table 2]

For each of the evaluation sample magnetic tapes of Examples B1 to B5 and Comparative Example B1 produced as described above, the surface roughness (R), the maximum surface roughness (Rmax), and the magnetic tape Measure the characteristics (error rate, dropout, electromagnetic conversion characteristics) under the following evaluation conditions,
evaluated. Table 3 shows the results.

<Evaluation Conditions> Maximum surface roughness (Rmax): A 30 μm square area was measured using SPM (Nanoscope III D-300) manufactured by Digital Instruments. Magnetic tape characteristics: DV deck DHR manufactured by Sony Corporation
The following evaluation was performed using a modified version of -1000 (trade name). (1) Error rate: 60 minutes for running durability as 10
The vehicle was run on 0 passes, and the block error rate after running on 1 pass and the error rate after running on 100 passes were measured. (2) Dropout: A 10 μsec dropout was counted for 10 minutes and measured. (3) Electromagnetic conversion characteristics (RF output): This was shown as a reference tape ratio (in dB) obtained by comparing the measured RF output value of each sample magnetic tape with the RF output value of the prepared reference tape.

[0087]

[Table 3]

Evaluation Results As shown in Table 3, an underlayer 62 made of Al oxide was formed to a thickness of 2 to 100 nm, and the surface roughness (R
a) and the maximum surface roughness (Rmax) are controlled by film forming conditions (adjusting the amount of oxygen introduced) of vacuum evaporation, and each layer such as the magnetic layer 63 is provided thereon to obtain the examples B1 to B5 according to the present invention. On the surface of the sample magnetic tape, suddenly large projections (corresponding to Rmax) are reduced, and the projections have a substantially uniform height. As a result, since there are no surface defects such as sudden large projections, the error rate and dropout are greatly improved, and the RF output shows a good result.

On the other hand, in the case of the sample magnetic tape of Comparative Example B1 in which the surface property was controlled by mixing fine particles into the nonmagnetic support 61 without forming the underlayer 62, the nonmagnetic support 61 was mixed with the nonmagnetic support 61. Since there are sudden protrusions formed by the aggregation of the minute particles, the protrusions are reflected on the surface of the sample magnetic tape, and the maximum surface roughness (Rmax) is increased. As a result, the error rate, dropout, and RF output characteristics are also deteriorated.

As described above, by changing the conditions for forming the underlayer 62, it is possible to form a preferable surface state for the characteristics required for the magnetic tape. The surface of the recording medium obtained by forming such an underlayer 62 has
When mixing microparticles into a non-magnetic support to control the surface state, sudden projections caused by particle agglomeration, etc. are prevented, and the surface state is controlled with a uniform surface roughness consisting of projections of uniform height. Present.

Next, the above Examples A1 to A5 and Reference Example A1
-A5, the coefficient of friction was measured under the following evaluation conditions using the evaluation sample magnetic tapes obtained in Examples B1 to B5 and Comparative Example B1. The results are shown in Table 4 and FIG. Table 4 also shows the maximum surface roughness (Rmax) and the error rate of the evaluation results. FIG. 6 shows the relationship between the maximum surface roughness and the error rate, and the relationship between the maximum surface roughness and the coefficient of friction. <Evaluation conditions> Friction coefficient:

[0092]

[Table 4]

From the evaluation result Table 4 and FIG. 6, the maximum surface roughness (R
It can be seen that when max) is smaller than 10 nm, the coefficient of friction increases sharply, while when it is larger than 80 nm, the error rate likewise increases sharply. For this reason, it is necessary that the maximum surface roughness (Rmax) of the underlayer transferred and reflected on the surface roughness of the magnetic recording medium be controlled to 10 nm to 80 nm. By adjusting the maximum surface roughness (Rmax) by polishing or controlling the film forming conditions of the underlayer to adjust the maximum surface roughness (Rmax), good friction characteristics and magnetic conversion characteristics can be obtained.

[0094]

According to the present invention, it is possible to obtain a magnetic recording medium in which the maximum surface roughness (Rmax) of the underlying surface is adjusted. The adjusted underlayer prevents large projections and the like from being transferred to the recording medium surface, reduces dropouts and error rates, and controls the surface flatness and roughness in a well-balanced manner. It has excellent durability such as characteristics and shuttle characteristics, and also has good sliding characteristics and running properties, and can cope with a shorter wavelength of a magnetic recording / reproducing system and a narrower recording track pitch.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a layer structure of a metal thin film type magnetic recording medium of the present invention.

FIG. 2 is a schematic configuration diagram of a vapor deposition apparatus showing an example for forming an underlayer and a magnetic layer constituting a metal thin-film magnetic recording medium according to an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a plasma CVD continuous film forming apparatus showing another example for forming a protective layer constituting a metal thin film magnetic recording medium according to an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a magnetron sputtering apparatus showing another example for forming a back coat layer constituting a metal thin film magnetic recording medium according to an embodiment of the present invention.

FIG. 5 is a schematic sectional view showing a layer structure of a metal thin-film magnetic recording medium in an example of the present invention.

FIG. 6 is a diagram showing the relationship between the maximum surface roughness (Rmax), the error rate, and the coefficient of friction of the evaluation sample magnetic tape in the example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic support, 2 ... Underlayer, 3 ... Magnetic layer, 4
… Protective layer, 5… back coat layer, 6… metal thin film magnetic recording medium, 10… vapor deposition device, 11… vacuum chamber, 1
3 ... feed roll, 14 ... take-up roll, 15 ...
Cooling can, 16: Guide roll, 17: Guide roll, 18: Crucible, 19: Al metal magnetic material, 2
0: electron gun, 21: exhaust port, 22: exhaust port, 23
...... Shutter, 24 ... Oxygen gas introduction tube, B ... Electron beam, 27 ... Workpiece, 28 ... Discharge gas introduction port, 30
... plasma CVD continuous film forming apparatus, 31 ... vacuum chamber,
32 exhaust system, 33 feed roll, 34 take-up roll, 35 can for counter electrode, 36 guide roll, 37 reaction tube, 38 electrode, 39 DC power supply, 40 magnetron sputtering apparatus, 41 supply roll, 42 take-up roll, 43 vacuum pump, 44 chamber, 45 object to be processed, 46
Cooling can, 47 Guide roll, 48 Target, 49 Backing plate, 50 Magnet, 51 Valve, 52 Gas inlet tube, 61 Nonmagnetic support, 62 Underlayer , 63 ... magnetic layer, 64 ...
... Protective layer, 65 ... Lubricant, 66 ... Lubricant

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 5D006 BB01 CA01 CA05 EA04 FA05                       FA09                 5D112 AA03 AA05 BB01 FA02 GA13                       GA17

Claims (4)

[Claims] 1. A metal thin film type magnetic material comprising: a base layer made of a metal material selected from metals, metalloids and alloys, and oxides and composites thereof, and a magnetic layer formed sequentially on a nonmagnetic support. A recording medium, wherein the underlayer has a maximum surface roughness (Rmax) of 10 to 80 nm. 2. The metal thin-film magnetic recording medium according to claim 1, wherein said underlayer has a thickness of 2 to 200 nm. 3. A step of forming an underlayer made of a metal material selected from metals, metalloids and alloys and oxides and composites thereof on a nonmagnetic support, and polishing the underlayer surface with an abrasive film And a step of forming a magnetic layer on the underlayer by a vacuum thin-film forming technique. Of manufacturing a thin metal film type magnetic recording medium. 4. An underlayer made of a metal material selected from metals, metalloids and alloys and oxides and composites thereof on a non-magnetic support, and a maximum surface roughness (R) of the underlayer.
max) of 10 to 80 nm, and a step of forming a magnetic layer on the underlayer by a vacuum thin film forming technique. Manufacturing method of a magnetic recording medium.