JPH0991650A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic recording medium excellent in overwriting characteristics by regulating the curvature of the columns of each of magnetic films to <=20% and increasing the curvature toward the top one of the magnetic films. SOLUTION: A material such as polyethylene terephthalate, polybutylene terephthalate or other polyester is used as the material of the substrate 1 of a magnetic recording medium. Plural magnetic films, especially metallic thin film type magnetic films 21 , 22 ∼each consisting of diagonally grown columns are laminated on the substrate 1 by PVD such as oblique vapor deposition using a metal such as Fe or Co or an alloy such as Co-Ni. The thickness of each of the metallic magnetic films 21 , 22 ∼is regulated to about 300-2,500Å, the curvature of the columns of each of the magnetic films 21 , 22 ∼is regulated to 5-20% and the curvature is increased toward the top one of the magnetic films. In the case of two magnetic films, the curvature of the columns of the lower magnetic film 21 and that of the upper magnetic film 22 are preferably regulated to 5-15% and 8-20%, respectively. The objective magnetic recording medium excellent in overwriting characteristics is obtd.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a magnetic recording medium.

[0002]

In recent years, so-called vapor-deposited tapes, particularly multi-layer vapor-deposited tapes, have been considered promising as magnetic tapes for high recording density. In this vapor-deposited tape, as one means for achieving a high recording density, it has been adopted to increase the magnetostatic characteristics represented by the coercive force Hc and the residual magnetic flux density Br.

However, when Hc is increased, the repetitive recording characteristic (OW characteristic) is deteriorated. By the way, if the permanent preservation of the information signal is considered, the O.D. W. Degradation of properties may not be a problem. However, in many cases, the magnetic recording medium is used by writing once and then writing again. Therefore, O. W. Improvement of characteristics is indispensable.

However, until now, the O. W. The study on the characteristics has not been advanced so much. This O. W. As a result of intensive studies by the present inventor to improve the characteristics, the balance between the coercive force Hc‖ in the longitudinal direction and the coercive force Hc⊥ in the vertical direction is controlled by controlling the curvature of the column structure of the magnetic film. Can be controlled, and O. W. It has been found that an improvement in characteristics can be obtained.

Therefore, the present invention has a high output and
O. W. It is an object to provide a magnetic recording medium having excellent characteristics.

[0006]

The object of the present invention is to provide a magnetic recording medium in which a plurality of metal thin film type magnetic films in which columns are grown obliquely are laminated on a support, and the columns of each magnetic film are formed. Is less than 20%, and the higher the magnetic film is, the larger the curvature rate is.

In particular, in a magnetic recording medium in which a plurality of magnetic thin film type magnetic films in which columns are grown obliquely are laminated on a support, the curvature ratio of each magnetic film column is 5 to 20%, among which, The curvature of the column of the magnetic film in the uppermost layer is 8 to 20.
%, The curvature rate of the column of the magnetic film in the lowermost layer is 5 to 15%
And the higher the magnetic film is, the higher the curvature rate is.

When the curvature ratios of the adjacent magnetic film columns are compared, the curvature ratio of the upper magnetic film column is 1.3 to 2 times the curvature ratio of the lower magnetic film column. Those are preferable. Further, it is preferable that the upper magnetic layer has a smaller thickness. The tilt angle of the column of the magnetic film in the uppermost layer is 35 to 60 ° (particularly 45 to 60 °), and the tilt angle of the column of the magnetic film in the lowermost layer is 30 to 55 ° (particularly 45 to 5 °).
5 °) is preferable.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a magnetic recording medium in which a plurality of metal thin film type magnetic films in which columns are grown obliquely are laminated on a support, and the curvature ratio of each magnetic film column is 20.
%, And the magnetic film on the upper side has a larger curvature rate. In particular, in a magnetic recording medium in which a plurality of layers of metal thin film type magnetic films in which columns are grown obliquely are laminated on a support, the curvature rate of each magnetic film column is 5 to 20%, among which the uppermost layer. Curvature of column of magnetic film is 8 to 20
%, The curvature rate of the column of the magnetic film in the lowermost layer is 5 to 15%
In addition, the higher the magnetic film is, the higher the curvature rate is.

When comparing the curving rates of the adjacent magnetic films, the curving rate of the column of the upper magnetic film is 1.3 to 2 times that of the column of the lower magnetic film. Further, the thickness of the upper magnetic film is smaller. Moreover, the tilt angle of the column of the magnetic film in the uppermost layer is 35 to 60 °, and the tilt angle of the column of the magnetic film in the lowermost layer is 30 to 55 °.

The details will be described below. FIG. 1 is a schematic diagram of a magnetic recording medium according to the present invention. The magnetic recording medium support 1 of the present invention may be magnetic or non-magnetic. Typical examples include polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polycyclohexylene dimethylene terephthalate, polyesters such as polyethylene bisphenoxycarboxylate, polyolefins such as polyethylene and polypropylene, cellulose acetate butyrate, Cellulose derivatives such as cellulose acetate propionate, polyvinyl chloride,
Examples thereof include vinyl resins such as polyvinylidene chloride and non-magnetic plastic materials such as polyamide and polycarbonate. Of course, it is not limited to these. Also, various kinds of processing may be performed. For example, corona discharge,
Alternatively, surface treatment is performed by other appropriate means.
Further, polyester, polyurethane, oligomer or the like may be applied for improving the adhesiveness.

Magnetic films, particularly metal thin film type magnetic films 2 ₁ and 2 _{2 having} columns grown obliquely on the support 1 by PVD (Physical Vapor Deposition) method such as oblique deposition.
... are laminated in plural layers. Examples of the material forming the metal magnetic film include C, in addition to metals such as Fe, Co, and Ni.
o-Ni alloy, Co-Pt alloy, Co-Ni-Pt alloy, Fe-Co alloy, Fe-Ni alloy, Fe-Co-N
An i alloy, a Fe-Co-B alloy, a Co-Ni-Fe-B alloy, a Co-Cr alloy, or the like is used. As the metal magnetic film, a nitride film (for example, Fe-N, Fe-
N—O), a carbonized film (for example, Fe—C—O), and the like are also included. Then, specifically, two or three layers of metal thin film type magnetic films are laminated. Of course, there may be four or more layers. However, if the number of layers is four or more, productivity will decrease, and
In reality, the total thickness of the magnetic film is regulated, so the thickness per layer must be reduced. However, if the thickness is made too thin, the saturation magnetic flux density Bs will decrease. Layers are preferred.

The thickness of each of the metal magnetic films 2 ₁ , 2 ₂ ... Is preferably thin in order to reduce thickness loss and improve output characteristics in a high frequency range. However, since the output in the low range is affected by the thickness of the metal magnetic film, it is preferably about 300 to 2500 Å. It is preferable that the thickness of the metal magnetic film is thinner as it is the upper magnetic film from the viewpoint of output characteristics in a high range. More specifically, in the case of a two-layer film, the lower magnetic film 2 _{1 has} a thickness a ₁ of 1000 to 2000Å, the upper magnetic film 2 _{2 has} a thickness a ₂ of 500 to 1500Å, and a ₁ + a _{2 of} 1500 to 2000Å. Three
000Å (especially 1800-3000Å), a ₁ > a ₂
Is preferred. If a three-layered film, thickness a ₁ of the lower magnetic layer 2 ₁ 1000～1500A, thickness a of the intermediate magnetic film 2 _2
2 is 500-1000, thickness a ₃ of the upper magnetic film 2 _{3 300~700Å, a 1 + a 2 +} a 3 is 1500-35
00Å (especially 1800-3000Å), a ₁ > a ₂ >
a ₃ is preferable. As a result, it is possible to record a short-wavelength component signal on the upper magnetic film side and a long-wavelength component signal on the lower magnetic film side, and obtain a high output from a low range to a high range and a good frequency characteristic. It becomes a thing. Also, O.
W. The characteristics are also improved.

Each of the metallic magnetic films 2 ₁ , 2 _2, ... Has a column curvature rate of 5 to 20%, and the higher the magnetic film is, the higher the curvature rate is. If double-layered film, the curvature of the lower magnetic layer 2 ₁ of the column b ₁ is 5-15%, curvature b ₂ of the upper magnetic film 2 ₂ of column 8 to 20% b _2> b ₁ (especially , B ₂
> 1.3 × b ₁ ) is preferred. If a three-layered film, a lower magnetic film 2 curvature b ₁ of ₁ column is 5-10%, curvature b ₂ of the intermediate magnetic film 2 ₂ of column 10-15%, the upper magnetic film 2 ₃ columns Has a bending rate b ₃ of 15 to 20%, b ₃ >.
b ₂ > b ₁ (particularly b ₃ > 1.3 × b ₂ , b ₂ > 1.3
× b ₁ ) is preferable. With such a column structure, a short wavelength component signal can be recorded on the upper magnetic film side and a long wavelength component signal can be recorded on the lower magnetic film side. W. The characteristics are also improved.

In the present specification, the curvature of the column means
As shown in Fig. 2, the length B of the straight line connecting both ends of the column
And a straight line that is orthogonal to the straight line, and the orthogonal line is the maximum length A that intersects the column, and (A
/ B) means a value (%) represented by 100. still,
The diagram of the column of the metal magnetic film as shown in FIG. 2 for obtaining this curvature can be obtained by a transmission electron microscope (TEM) image of one cut parallel to the longitudinal direction.

The metallic magnetic film is a colloid of the uppermost magnetic film.
Inclination angle (θ in Fig. 2) is 35 to 60 °, which is in the bottom layer
The tilt angle of the column of the magnetic film is preferably 30 to 55 °. two
When it is a layer film, the lower magnetic film 2₁Column tilt angle θ₁
Of 30 to 55 ° (particularly 45 to 55 °), the upper magnetic film 2
₂Column tilt angle θ₂Is 35 to 60 ° (especially 45 to
60 °), θ₂> Θ₁Is preferred. If it is a three-layer film,
Lower magnetic film 2₁Column tilt angle θ₁Is 30-55 °,
Middle magnetic film 2₂Column tilt angle θ₂Is 33-57 °,
Upper magnetic film 2_ThreeColumn tilt angle θ_ThreeIs 35-60 °,
θ_Three> Θ₂> Θ ₁Is preferred. With such a column structure
Signal of the short wavelength component on the side of the upper magnetic film by
The signal of long wavelength component can be recorded on the side of the lower magnetic film.
Not only is the wave number characteristic improved, but the O.D. W. Improves characteristics
You.

The magnetic film having the above-described structure has a coercive force Hc.parallel. In the longitudinal direction of 1000 to 2500 Oe.
(Especially 1500 to 2000 Oe), and coercive force Hc⊥ in the vertical direction is 1500 to 3000 Oe (especially 2000 to 2).
It is preferably 500 Oe). Further, not only the curvature rate of the column of the magnetic film is 20% or less and the curvature rate of the magnetic film on the upper side is increased, but also the coercive force is configured as described above, whereby the direction perpendicular to the longitudinal direction. Is balanced, the output in the high range is high, and O.
W. The characteristics are also improved.

A protective film 3 is provided on the uppermost metal thin film type magnetic film provided by oblique vapor deposition or the like. As a material for forming the protective film 3, for example, Al, Si, Ti, C
Oxides, nitrides and carbides of metals such as r, Zr, Nb, Mo, Ta and W, diamond-like carbon and boron nitride are used. CV as film forming method
D (chemical vapor deposition) or PVD is used. The thickness of the protective film is 10 ~ 500Å, especially 30 ~ 20
It is about 0Å.

A lubricant film 4 is provided on the protective film 3.
You. For example, the fluorine lubricant film is dipped or
It is provided with a thickness of about 20 to 70Å by means such as spraying.
You. As the lubricant, for example,-(C (R) F-CF₂-O)_p-(However
And R is F, CF_Three, CH_ThreeSuch as HOOC-CF)₂
(O-C₂F_Four)_p(OCF₂)_q -OCF₂-COOH, F- (CF₂CF₂CF₂O)_n-C
F₂CF₂Carboxyl group-modified perfluoro such as COOH
Oropolyether, HOCH ₂-CF₂(O-C₂F_Four)_p(OCF₂)_q -OC
F₂-CH₂OH, HO- (C₂H_Four-O)_m-CH₂-(O-C₂F_Four)_p(OCF ₂)_q -
OCH₂-(OCH₂CH₂)_n-OH, F- (CF₂CF₂CF₂O)_n-CF₂CF₂CH₂OH
Alcohol-modified perfluoropolyate
Or an alkyl group or the like on one or a part of the molecule.
Saturated hydrocarbon group, or unsaturated hydrocarbon group, or
Examples include aromatic hydrocarbon groups and those with other functional groups.
You can Specifically, FOMBL of Montecatini
IN Z DIAC, FOMBLIN Z DOL,
Demnum SA of Ikin Industries Co., Ltd. and the like.

A back coat film 5 is provided on the other surface side of the support 1. When the back coat film is formed by coating, carbon black having a particle size of 10 to 100 nm is dispersed in a binder resin such as a PVC-based resin or a urethane-based resin, and is dried by a gravure method, a reverse method, a die coating method, or the like. Is applied so as to be 0.4 to 1 μm. When the back coat film is formed by PVD means such as vapor deposition, Al
Place a metallic material such as a Cu alloy in the evaporation source and deposit evaporated metal particles to a thickness of 0.05-1 μm. Then, a top coat layer may be provided on such a back coat film in order to improve running properties and durability.

Next, a method of manufacturing the magnetic recording medium of FIG. 1 will be briefly described. For the magnetic recording medium of the present invention, a conventionally known method can be adopted, but it is preferable to use the continuous oblique vapor deposition apparatus shown in FIG. Incidentally, FIG. 3 shows a case where a magnetic recording medium composed of two layers of metal magnetic films is manufactured. Reference numeral 10a denotes a supply side roll of the support body 1, 10b denotes a winding side roll of the support body 1, 11 denotes a cooling drum, and the support body 1 is wound from the supply side roll 10a through the cooling drum 11 to the winding side roll 10b. Go away.
12a and 12b are crucibles, 13a and 13b are crucibles 12
The magnetic metals 13a and 13b are filled in a and 12b. The magnetic metals 13a and 13b receive an electron beam from the electron guns 14a and 14b, evaporate, and deposit on the traveling support 1. In the present invention, by controlling the positions of the crucibles 12a and 12b, it is possible to make the column curvature and inclination angle desired. Therefore, the positions of the crucibles 12a and 12b may be set at appropriate positions, and the positions of the crucibles 12a and 12b may be determined from the information obtained by executing this.
Then, first, magnetic metal particles from the crucible 12a set at a predetermined position are deposited on the support 1 running in the chamber 15 evacuated to 10 ⁻⁴ to 10 ⁻⁶ Torr to have a thickness a ₁ , Column curvature b ₁ , column tilt angle θ
The lower magnetic layer 2 ₁ of ₁ is formed. Incidentally, the time of the lower magnetic film 2 ₁ formation, oxygen gas supply and the nozzle 16a and oxygen is supplied, the surface oxidation is carried out. Thereafter, on the lower magnetic film 2 _1, a crucible 1 which is set in a predetermined position
Magnetic metal particles from 2b are deposited to form an upper magnetic film 2 ₂ having a thickness a ₂ , a column curvature rate b ₂ , and a column inclination angle θ ₂ . Note that when the upper magnetic film 2 ₂ formation, and oxygen is supplied from oxygen gas supply nozzle 16b, the surface oxidation is carried out. Thus, after the lower magnetic film 2 ₁ and the upper magnetic film 2 ₂ are laminated, a protective film, a lubricant film, and a back coat film are provided, if necessary, to obtain the magnetic recording medium of the present invention. .

[0022]

Example 1 The magnetic recording medium of this example is shown in FIG.
Obtained by an oblique vapor deposition device. Ie non-magnetic support
Body (9.8 μm thick PET film) 1 on the supply side
Roll 10a, the cooling drum 11, the winding side roll
10b so as to be guided to the inside of the chamber 15
1 × 10^-FiveEvacuate to Torr vacuum. And 1m
Electric power is applied to the PET film 1 running at a speed of / min.
Inside the crucible 12a due to electron beam heating from the child gun 14a
Of magnetic metal (Co) of ₁= 15
00Å, column curvature b₁= 5.5%, column tilt
Angle θ₁= 49 ° lower magnetic film 2₁Was formed. The lower layer
Magnetic film 2₁The oxygen gas supply nozzle 16a when forming
Lower magnetic film 2 at a rate of 30 sccm₁Oxygen towards
We are supplying. By electron beam heating from the electron gun 14b
The magnetic metal (Co) in the crucible 12b also melts and evaporates.
Therefore, the lower magnetic film 2₁The next stage when
And the thickness a₂= 1000Å, column curvature b₂= 8.
5%, column tilt angle θ₂= 55 ° upper magnetic film 2₂But
It is formed. The upper magnetic film 2₂When forming
Upper layer magnetism at a rate of 30 sccm from the gas supply nozzle 16b
Membrane 2₂Oxygen is being supplied to the lower magnetic film 2 as described above.₁And the upper magnetic film 2₂To
After formation, a protective film (d
Earmon like carbon film 3 is formed with a thickness of 50Å,
After this, a fluorine-based lubricant such as perfluoropolyether
(Product name FOMBLIN AM2001) 4 12Å thickness
Formed.

On the surface of the PET film 1 opposite to the surface on which the magnetic film is formed, an Al vapor deposition film (back coat film) 5 is formed.
A magnetic tape for VTR having a thickness of 2 μm and cut into a width of 8 mm was manufactured.

[0024]

Second Embodiment In the first embodiment, the crucibles 12a and 12b are used.
The position of the oxygen gas supply nozzle 16a,
The procedure of Example 1 was repeated except that the oxygen supply amount from 16b was 50 sccm, and the lower magnetic film 2 ₁ (thickness a ₁ = 160
0Å, column curvature b ₁ = 7%, column tilt angle θ ₁
= 52 °), and the upper magnetic film 2 ₂ (thickness a ₂ = 1400
Å, column curvature b ₂ = 12%, column tilt angle θ ₂
A magnetic tape for 8 mm VTR having an angle of 55 ° was manufactured.

[0025]

[Third Embodiment] The crucibles 12a and 12b in the first embodiment.
The position of the oxygen gas supply nozzle 16a,
The lower magnetic film 2 ₁ (thickness a ₁ = 200) was performed according to Example 1 except that the oxygen supply amount from 16b was 35 sccm.
0Å, column curvature b ₁ = 15%, column tilt angle θ
₁ = 46 °) and the upper magnetic film 2 ₂ (thickness a ₂ = 500)
Å, column curvature b ₂ = 20%, column tilt angle θ ₂
A magnetic tape for VTR having an angle of 52 ° was manufactured.

[0026]

[Fourth Embodiment] In the first embodiment, the crucibles 12a and 12b are used.
The position of the oxygen gas supply nozzle 16a,
The lower magnetic film 2 ₁ (thickness a ₁ = 150) was performed according to Example 1 except that the oxygen supply amount from 16b was set to 40 sccm.
0Å, column curvature b ₁ = 5%, column tilt angle θ ₁
= 55 °), and the upper magnetic film 2 ₂ (thickness a ₂ = 1000)
Å, column curvature b ₂ = 10%, column tilt angle θ ₂
A magnetic tape for VTR having an angle of 60 ° was manufactured.

[0027]

[Embodiment 5] By further developing the apparatus shown in FIG. 3, a crucible, a cooling drum, an oxygen gas supply nozzle, and the like are additionally installed in a continuous oblique vapor deposition apparatus, and the crucible position is changed. Oxygen supply of 36s
The lower magnetic film 2 was formed in the same manner as in Example 1 except that the thickness was changed to ccm.
₁ (thickness a ₁ = 1500Å, column curvature b ₁ = 8
%, Column tilt angle θ ₁ = 51 °), middle magnetic film 2
₂ (thickness a ₂ = 1000Å, column curvature b ₂ = 13
%, Column tilt angle θ ₂ = 55 °), and upper magnetic film 2
₃ (thickness a ₃ = 500Å, column curvature b ₃ = 20)
%, Column tilt angle θ ₃ = 57 °) 8 mm VT
An R magnetic tape was produced.

[0028]

[Comparative Example 1] In Example 1, crucibles 12a, 12b.
The position of the oxygen gas supply nozzle 16a,
The lower magnetic film 2 ₁ (thickness a ₁ = 100 is performed according to Example 1 except that the oxygen supply amount from 16b is 35 sccm.
0Å, column curvature b ₁ = 15%, column tilt angle θ
₁ = 55 °) and the upper magnetic film 2 ₂ (thickness a ₂ = 100)
0Å, column curvature b ₂ = 15%, column tilt angle θ
An 8 mm magnetic tape for VTR having ₂ = 55 °) was produced.

[0029]

Comparative Example 2 In Example 1, the crucibles 12a and 12b
The position of the oxygen gas supply nozzle 16a,
The lower magnetic film 2 ₁ (thickness a ₁ = 950 is carried out in the same manner as in Example 1 except that the oxygen supply amount from 16b is 35 sccm.
Å, column curvature b ₁ = 23%, column tilt angle θ ₁
= 50 °), and the upper magnetic film 2 ₂ (thickness a ₂ = 950
Å, column curvature b ₂ = 23%, column tilt angle θ ₂
A magnetic tape for 8 mm VTR having an angle of 55 ° was manufactured.

[0030]

[Comparative Example 3] In Example 1, the crucibles 12a and 12b were used.
The position of the oxygen gas supply nozzle 16a,
The procedure was carried out in the same manner as in Example 1 except that the oxygen supply amount from 16b was 15 sccm, and the lower magnetic film 2 ₁ (thickness a ₁ = 800
Å, column curvature b ₁ = 20%, column tilt angle θ ₁
= 51 °), and the upper magnetic film 2 ₂ (thickness a ₂ = 1000)
Å, column curvature b ₂ = 10%, column tilt angle θ ₂
A magnetic tape for 8 mm VTR having an angle of 55 ° was manufactured.

[0031]

[Comparative Example 4] In Example 1, the crucibles 12a and 12b were used.
The position of the oxygen gas supply nozzle 16a,
The same procedure as in Example 1 was performed except that the oxygen supply amount from 16b was 25 sccm, and the lower magnetic film 2 ₁ (thickness a ₁ = 120
0Å, column curvature b ₁ = 20%, column tilt angle θ
₁ = 48 °), and the upper magnetic film 2 ₂ (thickness a ₂ = 900)
Å, column curvature b ₂ = 13%, column tilt angle θ ₂
A magnetic tape for VTR having an angle of = 51 ° was manufactured.

[0032]

[Comparative Example 5] The procedure of Example 1 was repeated except that only the crucible 12a was used and the amount of oxygen supplied from the oxygen gas supply nozzle 16a was 40 sccm. An 8 mm VTR magnetic tape having a column curvature of 15% and a column inclination angle of 55 ° was manufactured.

[0033]

[Comparative Example 6] The procedure of Example 1 was repeated except that only the crucible 12a was used and the amount of oxygen supplied from the oxygen gas supply nozzle 16a was 25 sccm. An 8 mm VTR magnetic tape having a column curvature rate of 21% and a column inclination angle of 57 ° was produced.

[0034]

[Characteristics] Table-1 shows the characteristics of the magnetic tape for 8 mm VTR of each of the above examples. Table-1 Curvature (%) Magnetic film thickness (Å) Inclination angle (°) Surface roughness Upper layer Middle layer Lower layer Upper layer Middle layer Lower layer Upper layer Middle layer Lower layer Ra (nm) Example 1 8.5 5.5 1000 1500 55 49 1.6 Example 2 12 7 1400 1600 55 52 1.7 Example 3 20 15 500 2000 52 46 1.6 Example 4 10 5 1000 1500 60 55 1.4 Example 5 20 13 8 500 1000 1500 57 55 51 1.6 Comparative Example 1 15 15 1000 1000 55 55 1.7 Comparative Example 2 23 23 950 950 55 50 1.5 Comparative Example 3 10 20 1000 800 55 51 1.6 Comparative Example 4 13 20 900 1200 51 48 1.6 Comparative Example 5 15 1800 55 1.6 Comparative Example 6 21 2000 57 1.6 Further, static magnetic characteristics (Hc ‖, Hc⊥) and O. W. The characteristics were investigated, and the results are shown in Table 2. In addition, O. W. The characteristics are that long wavelength (1.0 μm, 23 μm) signals are recorded first, and then short wavelength (0.5 μm) signals are recorded.
After that, signals of long wavelength (1.0 μm, 23 μm) were read and the remaining portion was examined.

Table-2 Hc‖ (Oe) Hc⊥ (Oe) O. W. Characteristic (dB) 1.0μ → 0.5μ 23μ → 0.5μ Example 1 1590 1980 −1.9 −1.7 Example 2 1540 1730 −1.6 −1.5 Example 3 1720 2360 −2.6 −2 .3 Example 4 1630 1890 -3.4 -2.8 Example 5 1570 1890 -2.9 -2.6 Comparative Example 1 1570 1870 +0.7 +0.3 Comparative Example 2 1530 1890 0 0 Comparative Example 3 1320 1860 +0.2 +0.3 Comparative Example 4 1340 1720 -0.1 -0.3 Comparative Example 5 1500 1960 +0.4 +0.1 Comparative Example 6 1480 1960 +0.7 +0.5 As can be seen from the present invention, Is O. W. It has excellent characteristics and is easy to use even after repeated use.

[0036]

[Effect] O. W. It has excellent characteristics and there are few mistakes even if it is used repeatedly.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a magnetic recording medium of the present invention.

FIG. 2 is an explanatory diagram of curvature rate.

FIG. 3 is a schematic view of an oblique deposition apparatus for manufacturing the magnetic recording medium of the present invention.

[Explanation of symbols]

1 Support 2 ₁ , 2 ₂ , 2 ₃ Magnetic film 3 Protective film 4 Lubricant film 5 Backcoat film

Claims (5)

[Claims] 1. A magnetic recording medium in which a plurality of metal thin film type magnetic films in which columns are grown obliquely are laminated on a support, and the curvature ratio of each magnetic film column is 20% or less, and A magnetic recording medium characterized in that the upper magnetic film has a larger curvature rate. 2. The curvature ratio of the column of the magnetic film on the uppermost layer is 8 to 20%, and the curvature ratio of the column of the magnetic film on the lowermost layer is 5%.
The magnetic recording medium according to claim 1, wherein the content is -15%. 3. When comparing the curvature rates of adjacent magnetic films,
3. The magnetic recording medium according to claim 1, wherein the curvature rate of the column of the upper magnetic film is 1.3 to 2.0 times the curvature rate of the column of the lower magnetic film. 4. The magnetic recording medium according to claim 1, wherein the upper magnetic film has a smaller thickness. 5. The tilt angle of the column of the uppermost magnetic film is 35 to 60 °, and the tilt angle of the column of the lowermost magnetic film is 30 to 55 °. Item 4. The magnetic recording medium according to item 4.