JPH10334441A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the magnetic recording medium having an excellent output characteristic by inclining a columnar structure of each magnetic layer in the opposite direction to a columnar structure of an adjacent magnetic layer as to a normal in the medium traveling direction and also making a squareness ratio of the front layer larger than a squareness ratio of its adjacent magnetic layer. SOLUTION: Magnetic layers 1 and 1' or 1, 1' and 1" are formed on a support 3, making growing directions of columnar structures 2 and 2' or 2, 2' and 2" of the individual layers inclined in the opposite direction to the growing direction of their individual adjacent magnetic layers respectively as to the normal P in the traveling direction of the medium. Then, the squareness ratio Sq A of the front layer 1 is made larger than the squareness ratio Sq B of the adjacent magnetic layer 1'. Since the columnar structure of the magnetic layers adjacent to each other are in the opposite directions to each other, an output has no directionality, and also since the squareness ratio Sq A is larger than the squareness ratio Sq B, the directionality of magnetic force lines at an azimuth inclination between heads is relaxed, and an output difference between the two heads having their different azimuths is diminished, and hence a stable output characteristic is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic recording medium. More specifically, the present invention relates to a metal thin film type magnetic recording medium having excellent output characteristics.

[0002]

2. Description of the Related Art As a magnetic recording medium, a coating type magnetic recording medium manufactured by applying a magnetic paint containing a magnetic powder to a substrate (film) made of polyethylene terephthalate or the like has been known. The magnetic recording medium of the type has a limit in the filling property of the magnetic powder, and it is difficult to increase the density and the thickness of the magnetic recording medium.

In order to achieve this high density, there has been proposed a so-called metal thin film type magnetic recording medium in which a thin film of a magnetic material is formed directly on a substrate, and this type is applied to a coating type magnetic recording medium. There are no characteristics. Metal thin-film type magnetic recording media have a high magnetic material filling rate, and are thinner and have higher saturation magnetization than coating type magnetic recording media, and are used in various application fields as suitable for high-density recording. I have. In the production of such a metal thin film type magnetic recording medium, in particular, a Co—Ni alloy, a Co—Cr alloy,
o-Cr-Ni alloy, Co-Cr-Ta alloy, Fe-C
A so-called oblique deposition method, in which a magnetic material such as an o-Ni alloy or an Fe-Co alloy is obliquely vapor-deposited on a base material, has become mainstream. Further, various improvements have been made to make the magnetic layer a multilayer structure in order to adjust the magnetic properties.

For example, JP-A-63-9015 discloses that
There is disclosed a magnetic recording medium having, as a magnetic layer, two metal thin film layers containing Co as a main component and having a specific thickness ratio in a specific relationship. This magnetic recording medium is said to be excellent in durability such as running properties and electromagnetic conversion characteristics. Also,
JP-A-6-139541 discloses a magnetic recording medium having a plurality of magnetic layers formed by oblique vapor deposition,
It is disclosed that the growth direction of the column structure of each magnetic layer is inclined in the direction opposite to the growth direction of the column structure of the adjacent magnetic layer. This magnetic recording medium has an advantage that a high output can be obtained regardless of the running direction of the tape.

On the other hand, recording a video signal such as a video tape requires storing a large amount of information, and in order to cope with this, it is necessary to increase the relative speed with respect to the head. For this reason, a helical scan method has been adopted in which a tape is wound around a head cylinder using a rotating head to perform recording and reproduction. In the rotary head used in this helical scan system, two heads are fixed in opposite directions by 180 °, and when the head cylinder rotates, video signals for one field are alternately recorded by each head as one track, Reproduction is performed similarly. A non-magnetized band called a guard band may be provided between the tracks, but it is desirable not to provide a guard band for higher density recording. However, if a guard band is not provided, a recording signal of a track not corresponding to each head is read out (crosstalk). Therefore, an azimuth recording method in which two heads have different inclinations to prevent crosstalk has been proposed. Has become the mainstream of various video tapes. The head used in this method is called an azimuth head, and crosstalk from an adjacent track is excluded due to azimuth loss. It is used as

[0006]

In azimuth recording, which is currently the mainstream, in addition to reducing the output difference depending on the running direction of the tape, in order to obtain a stable output, the head between two heads having different azimuth angles is required. Although it is desirable that there is no difference in output, studies on this point have not been sufficiently conducted for conventional magnetic recording media. It is intended to improve the characteristics and does not solve the problem of eliminating the output difference between the azimuth heads.

[0007]

Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies for the purpose of providing a magnetic recording medium having excellent output characteristics, and as a result, completed the present invention. .

That is, according to the present invention, in a magnetic recording medium having a support and a plurality of magnetic layers formed of a metal thin film formed on the support, the columnar structure of each magnetic layer is perpendicular to the normal in the medium running direction. The magnetic layer has a growth direction inclined in the direction opposite to the growth direction of the columnar structure of the adjacent magnetic layer, and the squareness ratio (Sq _A ) of the magnetic layer farthest from the support is adjacent to the magnetic layer. It is intended to provide a magnetic recording medium characterized by being larger than the squareness ratio (Sq _B ) of the magnetic layer to be formed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic layer of a magnetic recording medium according to the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing a cross section of a magnetic recording medium of the present invention viewed from a plane parallel to a running direction.
1A is an example in which two magnetic layers are formed, and FIG. 1B is an example in which three magnetic layers are formed. In the magnetic recording medium of FIG. 1A, two magnetic layers 1, 1 'are formed, and the columnar structures 2, 2' of each layer are schematically shown by oblique lines. The columnar structures 2, 2 'of the magnetic layers 1, 1' have a growth direction of the columnar structures of the magnetic layers adjacent to each other and a growth direction inclined in a direction opposite to the normal line P in the running direction of the medium. In FIG. 1, 3
Is a support. The magnetic recording medium of the present invention, the most distant magnetic layer from the support squareness ratio (hereinafter, also referred to outermost layer) (Sq _A) is from squareness ratio of the magnetic layer adjacent to the outermost layer (Sq _B) Is also large. Accordingly, the magnetic recording medium of FIG. 1a, squareness ratio Sq _A of the outermost layer 1 is larger than the squareness ratio Sq _B of the lower magnetic layer 1 '. That is, Sq _A > Sq _B. The magnetic layer 1,1 of three layers as shown in FIG. 1b ', 1' may 'is formed, similarly, rectangular magnetic layer 1' squareness ratio Sq _A of the outermost layer 1 is adjacent thereto It is larger than the ratio Sq _B. In the magnetic recording medium of FIG. 1B, the squareness ratio of the magnetic layer 1 ″ closest to the support does not matter.

Here, the squareness ratio (Sq) is given by Sq = Br
(Residual magnetic flux density) / Bs (saturated magnetic flux density), where Br (gauss) and Bs (gauss) are the magnetic flux density B and the magnetic field H
From the hysteresis curve. As for the squareness ratio of each magnetic layer, the squareness ratio in the longitudinal direction in the plane of the magnetic layer is measured using a sample vibration magnetometer (VSM), a magnetic torque meter, or the like. The coercive force Hc is also measured in the longitudinal direction in the plane of the magnetic layer.

In the present invention, the squareness ratio of each magnetic layer is preferably in the range of 0.6 to 0.99. Further, the squareness ratio of the farthest magnetic layer from the support squareness ratio (Sq _A) and the magnetic layer adjacent to the magnetic layer (Sq _B) is Sq _A -
It is more preferable that the relationship of Sq _B ≧ 0.1 is satisfied, that is, the difference in the squareness ratio is 0.1 or more. More preferably, Sq _A -Sq _B is 0.15 to 0.3. When this relationship is satisfied, the effect of the present invention becomes remarkable.

In the magnetic recording medium of the present invention, the columnar structure of each magnetic layer is inclined in the direction opposite to the normal in the medium running direction with respect to the columnar structure of the adjacent magnetic layer, and the squareness ratio of the outermost layer (Sq _A ) is the squareness ratio of the magnetic layer adjacent to the outermost layer (Sq _A ).
q _B ), and this structure allows
The output difference between the two heads with different azimuth angles is small, and stable output characteristics can be obtained. The reason is that the column structure is reversed, so that the output directionality is lost and the outermost layer It is considered that since the squareness ratio of the magnetic layer adjacent to the head is smaller, the directionality of the magnetic force lines due to the azimuth inclination between the heads is reduced.

In the present invention, the inclination angle of each columnar structure in the growth direction is not limited, but is generally about 30 ° to 70 °. Here, the inclination angle of the growth direction of the columnar structure refers to an angle between the growth direction of the columnar structure and the plane of the support. Further, the magnitude relationship of the inclination angles of the columnar structures does not matter.

The method of manufacturing a magnetic recording medium according to the present invention will be briefly described. FIG. 2 is a schematic view showing an example of an apparatus used for depositing a magnetic material. This vapor deposition apparatus has a vacuum chamber 2
1, a cylindrical can 23 for transporting the support 22, a vapor deposition means disposed below the cylindrical can 23, and for depositing a magnetic metal on the support 22 transported on the cylindrical can 23; And a gas introduction pipe 25 for introducing gas during vapor deposition. Here, the vapor deposition means includes a crucible 27 containing a magnetic metal 26 and the crucible 27.
The electron gun 28 is installed in the electronic gun. The inside of the chamber of this apparatus is maintained at a vacuum by a vacuum means (not shown).

An unwinding roll 29 is provided in the vacuum chamber 21.
And a take-up roll 30 are provided, and the support 22 is unwound from the unwind roll 29 and wound up by the take-up roll 30.
Is wound around the lower surface of the can 23 and travels. A crucible 27 (for example, M
gO), into which a magnetic metal such as Co, Ni, Fe or an alloy 26 of a magnetic metal is placed. The magnetic metal 26 is irradiated with a curved electron beam from an electron beam gun 28, thereby heating and evaporating the magnetic metal 26. The columnar structure of the metal thin film can be oxidized by introducing an oxygen gas or the like into the deposition region from the gas introduction tube 25 as necessary.

In order to obtain the magnetic recording medium of the present invention, a lower magnetic layer is formed by an apparatus as shown in FIG. 2, and then a film is set again from the winding roll 30 to the unwinding roll 29 and vapor-deposited. This makes it possible to form an upper magnetic layer in which the columnar structure of the magnetic layer is inclined in the opposite direction. When three or more magnetic layers are formed, vapor deposition may be performed in the same manner.

In general, when the apparatus as shown in FIG. 2 is used, it is known that, when the vapor deposition conditions (including the minimum incident angle θ _min ) are the same, decreasing the maximum incident angle θ _max reduces the squareness ratio. . Therefore, in order to adjust the squareness ratio of the metal thin film type to be the magnetic layer, the maximum incident angle θ _max when forming each magnetic layer may be controlled. As the magnetic recording medium of the present invention, the squareness ratio of the outermost layer (upper layer) and (Sq _A), to be larger than the magnetic layer adjacent to the outermost layer squareness ratio (lower layer) (Sq _B) is lower The maximum incident angle θ _max when forming the magnetic layer may be smaller than the maximum incident angle θ _max when forming the upper magnetic layer. Also, the squareness ratio can be controlled by the swing width of the electron beam from the electron gun in the longitudinal direction and / or the width direction, and generally, the squareness ratio decreases as the swing width increases. Further, the coercive force (Hc) and the saturation magnetic flux density (Bs) can be adjusted by controlling the introduction amount of oxygen gas and other deposition conditions as needed.

In the present invention, examples of the magnetic material for forming the metal thin film type magnetic layer include ferromagnetic metal materials used in the manufacture of ordinary metal thin film type magnetic recording media, such as Co, Ni and Fe. Ferromagnetic metal, Fe-C
o, Fe-Ni, Co-Ni, Fe-Co-Ni, Fe
-Cu, Co-Cu, Co-Au, Co-Y, Co-L
a, Co-Pr, Co-Gd, Co-Sm, Co-P
t, Ni-Cu, Mn-Bi, Mn-Sb, Mn-A
1, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co
Ferromagnetic alloys such as -Cr and Ni-Co-Cr; Further, nitrides, carbides, and oxides of these metals or metal alloys are also preferable.

For high-density recording, the magnetic layer of the magnetic recording medium is preferably formed on a substrate by oblique evaporation. The method for oblique deposition is not particularly limited, and follows a conventionally known method. The degree of vacuum at the time of vapor deposition is 10 ^-4 to 10 ^-7 Torr
It is about. In particular, by introducing an oxidizing gas to form an oxide on the surface of the magnetic layer, the durability can be improved.

Further, a back coat layer can be formed on the support. The back coat layer may be a coating type back coat layer having a thickness of about 0.2 to 1.0 μm containing carbon black or a binder as a main component, or a vapor deposition method, a DC sputtering method, an AC sputtering method, a high frequency sputtering method, By plating means such as DC magnetron sputtering, high frequency magnetron sputtering, ion beam sputtering, etc.
A metal thin film type back coat layer formed by adhering a metal or metalloid to a support in a vacuum may be used. In the latter case,
Although various metals can be considered as the metal to be adhered as the back coat layer, Al, Cu, Zn, Sn, Ni, Ag,
Co and alloys thereof are used, and Al, Co, C
A u-Al alloy is preferred. Further, ceramics such as an oxide film and a carbonized film which have been subjected to an oxidation reaction, a carbonization reaction, and the like at the time of vapor deposition are also suitable. Further, as the semimetal forming the back coat layer, Si, Ge, As, Sc, S
b or the like is used, and Si is preferable. It is preferable to further dope an additive to improve the conductivity. The thickness of the metal thin film type back coat layer is 0.05 to 1.0.
It is about μm.

In the magnetic recording medium of the present invention,
It is preferable that a protective film having a thickness of 1 to 50 nm is provided on the magnetic layer. As a material forming the protective layer, in addition to oxides, nitrides, and carbides of metals such as Al, SiC
And the like and compounds containing it. In particular, carbon films, especially diamond-like carbon, are preferred. The protective layer made of diamond-like carbon is formed by a physical vapor deposition (PVD) method or a chemical vapor deposition (CVD) method. In particular, it is formed by an ECR plasma CVD apparatus. That is, the ECR plasma CVD apparatus is operated on the magnetic layer on the support provided in the vacuum chamber, and plasma of the hydrocarbon gas is blown on the magnetic layer. Thereby, a protective layer (diamond-like carbon layer) is formed on the surface of the magnetic layer.

Further, in the magnetic recording medium of the present invention,
It is preferable to form a lubricant layer made of a suitable lubricant on the magnetic layer or the protective layer. Particularly, a fluorine-based lubricant such as perfluoropolyether is preferable, and the thickness of the lubricant layer is about 0.5 to 10 nm. As a lubricant, for example,
-[C (R) F-CF ₂ -O] _p- (where R is a group such as F, CF ₃ , CH ₃ ), especially HOOC-CF ₂ (OC ₂ F ₄ ) _p (OCF ₂ ) _q- OCF ₂ COOH, F- (CF ₂ CF ₂ CF ₂ O)
Carboxyl group-modified perfluoropolyether such as _n- CF ₂ CF ₂ COOH, HOCH ₂ -CF ₂ (OC ₂ F ₄ ) _p (OCF ₂ ) _q -OCF ₂ -CH ₂ OH, H
O- (C ₂ H ₄ O) _m -CH _2- (OC ₂ F ₄ ) _p (OCF ₂ ) _q -OCH _2- (OCH ₂ CH ₂ ) _n -OH,
_{F- (CF 2 CF 2 CF 2} O) n alcohol-modified perfluoropolyether, such as -CF ₂ CF ₂ CH ₂ OH and the like. Molecular weight 500 ~
50,000 is preferred. Specifically, there are "FOMBLIN Z DIAC" and "FOMBLIN Z DOL" (trade names) of Montecatini, and "Demnum SA" (trade name of Daikin Industries, Ltd.).

In the present invention, at least one of the above-described protective layer and lubricant layer is preferably formed on the back coat layer, preferably, the protective layer and the lubricant layer are formed on the protective layer. Is preferred from the viewpoint of running properties.

As the material for the support of the magnetic recording medium of the present invention, an ordinary non-magnetic support can be used, and polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyethylene, polypropylene Plastics such as cellulose triacetate and cellulose diacetate; polycarbonate; polyvinyl chloride; polyimide; and aromatic polyamide. The thickness of these supports is about 3 to 50 μm.

In the present invention, when the thickness of each magnetic layer is two, the thickness of the lower magnetic layer is preferably 10 to 200 nm, the thickness of the upper magnetic layer is preferably 5 to 100 nm, and the thickness of the three Preferably, the thickness of the lower magnetic layer is 10 to 200 nm, the thickness of the intermediate magnetic layer is 10 to 100 nm, and the thickness of the upper magnetic layer is 5 to 100 nm. Further, the number of magnetic layers is preferably as large as the high-frequency recording type medium, but a practical range is 2 to 2.
Five layers are considered appropriate. The multilayer magnetic layer may be formed one layer at a time, or may be formed continuously using two or more devices.

The coercive force of the magnetic recording medium of the present invention is:
The coercive force of the entire magnetic layer is preferably 1300 (Oe) or more, particularly preferably 1500 (Oe) or more.
Note that the relationship between the coercive force of the outermost layer and the coercive force of the magnetic layer adjacent thereto does not matter.

The magnetic recording medium of the present invention is suitable for high-frequency magnetic recording whose shortest recording wavelength is 0.4 μm or less.

[0028]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 (1) Manufacture of a magnetic tape Using an apparatus shown in FIG.
Co was deposited on a μm PET film to form a lower layer of Co-
An O-based magnetic layer was formed. The deposition conditions at this time were: electron gun power of 15 kW, swing width of the electron gun in the longitudinal running direction of the film of 5 cm, film running speed of 2 m / min, oxygen gas flow rate of 5
0SCCM, maximum incident angle θ _max 80 °, minimum incident angle θ
_min 55 °. The thickness of the obtained lower magnetic layer is 90
nm, and the squareness ratio (Sq _B ) were 0.85.

Next, the film is set again on the unwinding 29 from the winding roll 30, and Co is vapor-deposited while introducing oxygen gas in the same manner to form a columnar structure of the magnetic layer on the lower Co—O-based magnetic layer. Then, an upper Co—O-based magnetic layer having a growth direction inclined in a direction opposite to the growth direction of the columnar structure of the adjacent lower magnetic layer with respect to the normal line in the medium running direction was formed. The deposition conditions at this time were as follows: a swing width of the electron gun in the longitudinal running direction of the film of 1 cm, a running speed of the film of 2.4 m / min,
Oxygen gas flow rate 60 SCCM, maximum incident angle θ _max 90 °,
The minimum incident angle θ _{min was} 55 °, and the other conditions were the same as those of the lower magnetic layer. The thickness of the obtained upper magnetic layer was 80 nm, and the squareness ratio (Sq _A ) was 0.96.

Next, a 0.5 μm-thick back coat layer made of carbon black and a binder was formed on the surface of the film opposite to the magnetic layer by a known method.

Next, ECR plasma CVD is performed on the magnetic layer.
A protective layer made of a diamond-like carbon thin film having a thickness of 10 nm was formed by the method. Further, a fluorine-based lubricant (trade name: AM2001 (manufactured by Daikin Industries, Ltd.)) was adhered on this protective layer so as to have a thickness of 1 nm to form a lubricant layer. The film on which the magnetic layer, the diamond-like carbon protective layer, the fluorine-based lubricating layer and the back coat layer were formed as described above was cut into 3.81 mm widths,
It was loaded on a DAT cassette case to obtain a DAT tape.

(2) Performance Evaluation With respect to the DAT tape obtained above, the output ratio of heads A and B having different azimuth angles was measured. Set the DAT tape in a device that is a modified version of a commercially available DDS3 drive,
The envelope of each head was measured. When the envelope of the head A was set to 100, the envelope of the head B was relatively evaluated. The output was a relative evaluation using the output in the forward direction of Comparative Example 2 described later as a reference (0 dB). The closer the relative value of the envelope of the head B is to 100, the smaller the output difference between the heads is. Example 1
FIG. 3 shows the envelope waveform of the DAT tape obtained in step (1). Further, the output of 13 MHz was measured in the forward direction and the reverse direction of the running direction, and the output in the reverse direction with respect to the output in the forward direction was evaluated. Table 1 shows the results.

Example 2 In the same manner as in Example 1, two Co—O-based magnetic layers were formed.
An AT tape was manufactured. However, the deposition conditions for the lower magnetic layer were as follows: an electron gun power of 13 kW, a swing width of the electron gun in the longitudinal running direction of the film of 7 cm, and a running speed of the film of 1.3 m /.
Min, oxygen gas flow rate 40 SCCM, maximum incident angle θ _max 75
°, and the minimum incident angle θ _{min was} 50 °. The thickness of the obtained lower magnetic layer is 100 nm, and the squareness ratio (Sq _B ) is 0.74.
Met. The deposition conditions for the upper magnetic layer were as follows: the swing width of the electron gun in the longitudinal direction of the film was 1.5 cm, the maximum incident angle θ.
_{The maximum was} 85 ° and the minimum incident angle was θ _min 60 °, and the other conditions were the same as those of the upper magnetic layer of Example 1. The thickness of the obtained upper magnetic layer was 80 nm, and the squareness ratio (Sq _A ) was 0.94. The obtained DAT tape was evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 3 An Fe--NO--based lower magnetic layer (square ratio 0.56, thickness 70 nm) was formed on the PET film used in Example 1 by using the apparatus shown in FIG. Here, FIG. 5 shows a main part of the ion assisted vapor deposition apparatus used for forming the lower magnetic layer. In FIG. 5, reference numeral 51 denotes a can roll, 52 denotes a base film, 53 denotes an ion gun, 54 denotes a shielding plate, and 55 denotes a shielding plate. Electron gun,
Reference numeral 56 denotes a crucible, which contains metallic iron. In this example, the running speed of the PET film is 1 m / min,
Power of 8 kW, acceleration voltage of ion gun 23 1 k
V, minimum incidence angle 50 °, nitrogen gas flow rate 50SCC
M, the oxygen gas flow rate was 5 SCCM. Then, this F
An upper magnetic layer (square ratio 0.96) of Example 1 was formed on the e-NO-based lower magnetic layer according to the method of Example 1. Otherwise, a DAT tape was manufactured in the same manner as in Example 1. The obtained DAT tape was evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 4 According to the method of Examples 1 and 2, the lower magnetic layer of Example 1 (square ratio 0.85) was used as the lower magnetic layer, and the upper magnetic layer of Example 2 (square ratio 0.94). ) Was manufactured as an upper magnetic layer. Others are the same as in the first embodiment.
Tape was manufactured. The obtained DAT tape was evaluated in the same manner as in Example 1. Table 1 shows the results.

COMPARATIVE EXAMPLE 1 In the same manner as in Example 1, two Co—O-based magnetic layers were formed.
An AT tape was manufactured. However, the upper and lower magnetic layers were both formed under the conditions of the upper layer of Example 1, and the squareness ratio of both the upper and lower magnetic layers was 0.96. The obtained DAT tape was evaluated in the same manner as in Example 1. Table 1 shows the results. FIG. 4 shows an envelope waveform of the DAT tape obtained in Comparative Example 1.

Comparative Example 2 A DAT tape was manufactured by forming two Co—O-based magnetic layers under the conditions for forming the upper magnetic layer in Example 1. At this time, after the lower magnetic layer was formed, the raw material was rewound, and the upper magnetic layer was formed under the same conditions. The squareness ratio of the obtained DAT tape is 0.96 for both the upper and lower magnetic layers, and the growth direction of the columnar structure of the magnetic layer is in the medium running direction with respect to the normal line.
It is inclined in the same direction as the growth direction of the columnar structure of the adjacent magnetic layer. The obtained DAT tape was evaluated in the same manner as in Example 1. Table 1 shows the results.

[0039]

[Table 1]

As can be seen from the above results, the magnetic recording medium of the present invention has a small output difference depending on the running direction of the medium.
In addition, the difference in envelope strength between different azimuth heads is small.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a magnetic layer of a magnetic recording medium of the present invention.

FIG. 2 is a schematic view showing an example of an apparatus for forming a magnetic layer of the magnetic recording medium of the present invention.

FIG. 3 is a diagram showing an envelope waveform of the DAT tape manufactured in Example 1.

FIG. 4 is a diagram showing an envelope waveform of a DAT tape manufactured in Comparative Example 1.

FIG. 5 is a schematic view showing a main part of an ion-assisted vapor deposition apparatus used in Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Uppermost magnetic layer 1 '... Magnetic layer adjacent to the uppermost magnetic layer 1 "... Lowermost magnetic layer 2, 2', 2" ... Columnar structure of magnetic layer 21 ... Vacuum container 22 ... Film 23 ... Cooling can 25 ... Oxygen gas inlet tube 27 ... Crucible

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsumi Endo 2606 Kabane-cho, Akaga-cho, Haga-gun, Tochigi Prefecture In-house researcher (72) Inventor Takeshi Miyamura 2606, Kabashi-cho, Akabane-shi, Haga-gun, Tochigi Prefecture Kao Corporation Research Institute

Claims (5)

[Claims] In a magnetic recording medium having a support and a plurality of magnetic layers formed of a metal thin film formed on the support, a columnar structure of each magnetic layer is adjacent to a normal in a medium running direction. The magnetic layer having a growth direction inclined in the direction opposite to the growth direction of the columnar structure of the magnetic layer to be formed, and having a squareness ratio (Sq _A ) of the magnetic layer farthest from the support, the magnetic layer adjacent to the magnetic layer A magnetic recording medium having a squareness ratio (Sq _B ) of 2. The squareness ratio of each magnetic layer is 0.6 to 0.5.
2. The magnetic recording medium according to claim 1, wherein the range is 99. 3. The squareness ratio (S) of the magnetic layer farthest from the support.
q _A ) and the squareness ratio (Sq _B ) of the magnetic layer adjacent to the magnetic layer
The magnetic recording medium according to claim 1, wherein satisfies the relationship of Sq _A −Sq _B ≧ 0.1. 4. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a minimum recording wavelength of 0.4 μm or less. 5. The magnetic recording medium according to claim 1, wherein the coercive force is 1300 (Oe) or more.