JPH0830953A - Magnetic recording media - Google Patents

Abstract

PURPOSE:To improve the Hk distribution of a magnetic recording medium formed by vapor deposition and to increase the reproduction output in a short wavelength region. CONSTITUTION:When a metallic magnetic thin film 23 is formed on a nonmagnetic substrate 21 by vapor deposition to obtain a magnetic recording medium, a Ge under film 22 is interposed between the substrate 21 and the magnetic thin film 23 and the ratio of DELTAHc/Hc of the magnetic thin film 23 is regulated to <=0.25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporation type magnetic recording medium in which a metal magnetic thin film is formed by an evaporation method, and more particularly to improvement of characteristics in a short wavelength region.

[0002]

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

On the other hand, with the increasing demand for high density recording, Co--Ni alloys, Co--Cr alloys, Co--Ni--
A magnetic metal material such as O or Co-O is directly coated on a non-magnetic support such as a polyester film, polyamide, or polyimide film by plating or a vacuum thin film forming means (vacuum deposition method, sputtering method, ion plating method, etc.). A magnetic recording medium of the so-called metal magnetic thin film type, in which a magnetic layer is formed by the attachment, has been proposed and attracted attention.

This metal magnetic thin film type magnetic recording medium is excellent not only in coercive force and squareness ratio but also in electromagnetic conversion characteristics at a short wavelength, and because the magnetic layer can be made extremely thin, recording demagnetization and The thickness loss during reproduction is extremely small,
Since it is not necessary to mix a binder, which is a non-magnetic material, in the magnetic layer, there are various advantages such that the packing density of the magnetic material can be increased.

Particularly, an oblique vapor deposition type magnetic recording medium in which a metal magnetic material is vapor-deposited in an oblique direction has already been put to practical use because it has excellent electromagnetic conversion characteristics and a large reproduction output can be obtained.

[0006]

By the way, in recent years, in the field of magnetic recording, the wavelength of a recording signal has been further shortened for the purpose of improving the image quality and the like. It is required to obtain output.

Therefore, for example, in the above vapor deposition type magnetic recording medium, a reactive vapor deposition method in which oxygen gas is introduced into an atmosphere is used to form a metal magnetic thin film mixed with oxygen. Has been done.

However, in order to increase the output in the short wavelength region, it is important to control the composition of the magnetic layer, but this is not enough, and it is essential to improve the orientation of the magnetic particles. However, the fact is that studies from this point of view have not been sufficiently conducted.

Therefore, the present invention has been proposed in view of such conventional circumstances, and provides a magnetic recording medium in which the orientation of magnetic particles is good and a large reproduction output can be obtained in a short wavelength recording region. With the goal.

[0010]

In order to achieve the above object, the present invention provides a magnetic recording medium comprising a nonmagnetic support and a metal magnetic thin film formed by a vapor deposition method on the nonmagnetic support. Ge between the non-magnetic support and the metal magnetic thin film
An underlayer is provided, and the coercive force distribution ΔHc / of the metal magnetic thin film is
The value of Hc is less than 0.25.

The present invention is applied to an evaporation type magnetic recording medium in which a metal magnetic thin film is formed by an evaporation method.

In the present invention, in such a vapor deposition type magnetic recording medium, in order to improve the reproduction output in the short wavelength region, as shown in FIG.
e The underlayer film 22 is provided, the metal magnetic thin film 23 is formed thereon by an evaporation method, and the coercive force distribution ΔHc / Hc of the metal magnetic thin film is set to less than 0.25.

First, the function of the Ge underlayer and the orientation of the metal magnetic thin film will be described below.

When the metal magnetic thin film 23 is formed on the Ge underlayer 22 by the vapor deposition method, the orientation of vapor-deposited particles is affected by the Ge underlayer 22, and the anisotropic magnetic field Hk of the metal magnetic thin film 23 is obtained.
The distribution is different from that when the metal magnetic thin film is formed directly on the non-magnetic support 21. In the magnetic recording medium, the smaller the anisotropic magnetic field Hk distribution, the larger the output in the short wavelength region.

The Hk distribution of such a magnetic layer is ΔHc /
Hc can be estimated by Tagawa and Nakamura, Journal of Japan Society of Applied Sciences, Vol. 15, No2, 155-158,
1991.

Here, as the index of the Hk distribution of the magnetic layer, SFD (half-width of switching field distribution) or the like has been conventionally used. However, this SFD can obtain an accurate value in the case of an in-plane medium in which the easy axis of magnetization of the magnetic layer is oriented parallel to the film surface. In a medium whose axis is tilted with respect to the film surface, the MH loop is tilted due to the influence of the demagnetizing field, and an accurate value cannot be obtained.

On the other hand, ΔHc / Hc used in the present invention has an accurate value irrespective of the direction of the easy axis of magnetization.
It is possible to estimate the k distribution.

That is, as shown in FIG. 2, ΔHc is the magnetic field at Ms / 2 between the easy magnetization direction major loop and the minor curve inverted from the coercive force Hc in the easy magnetization direction MH loop. Is the width of. When the Hk distribution is approximated by a normal distribution, its standard deviation σhk is calculated from ΔHc / Hc by the following equation.

[0019]

[Equation 1]

As can be seen from this equation, the standard deviation σhk of the Hk distribution increases as ΔHc / Hc increases, and conversely, the standard deviation σhk of the Hk distribution decreases as ΔHc / Hc decreases. That is, in the metal magnetic thin film formed by the vapor deposition method, the Hk distribution of the vapor deposition particles is better as ΔHc / Hc is smaller.

Incidentally, ΔHc / Hc and wavelength 0.50 μm
FIG. 3 shows the relationship of the reproduction output in. The playback output d
The B value is a relative value when the reproduction output of a commercially available ME tape is 0 dB. Thus, there is a correlation between ΔHc / Hc and the reproduction output, and the smaller ΔHc / Hc, the larger the reproduction output at the short wavelength.

Therefore, in the present invention, the Ge underlayer film 22 is provided to adjust ΔHc / Hc of the metal magnetic thin film 23 to less than 0.25. ΔHc / of the metal magnetic thin film 23
By setting Hc in such a range, a magnetic recording medium having excellent characteristics in the short wavelength recording region can be more reliably obtained.

ΔHc / Hc of the metal magnetic thin film 23 is
It mainly changes depending on the film thickness of the Ge underlayer film 22 and the easy axis of magnetization of the metal magnetic thin film 23. Therefore, the metal magnetic thin film 23
To make ΔHc / Hc of less than 0.25, these parameters may be optimized.

That is, the thickness of the Ge base film 22 is set to 4 to 2
5 nm and the easy axis of magnetization of the metal magnetic thin film 23 is set to 0 to 70 ° with respect to the film normal direction.
ΔHc / Hc can be less than 0.25. G
e The thickness of the base film 22 is less than 4 nm or 25 nm
When it exceeds, ΔHc / Hc becomes larger than 0.25, and the output in the short wavelength recording region becomes insufficient. The thickness of the Ge base film 22 is more preferably 10 nm.
Above, further, it is 20 nm or less. The proper range of the coercive force Hc of the magnetic layer at this time is 1200 to 1600.
It is Oe.

Further, even when the angle of the easy axis of magnetization of the metal magnetic thin film 23 with respect to the film normal direction exceeds 70 °, ΔHc / Hc of the metal magnetic thin film 23 exceeds 0.25,
Large output cannot be obtained in the short wavelength recording region.

To increase the reproduction output, ΔHc
In addition to the film thickness of the Ge underlayer film 22 and the easy axis of magnetization of the metal magnetic thin film 23, which affect / Hc, the film thickness of the metal magnetic thin film 23 is important. If the thickness of the metal magnetic thin film 23 is too thin, a sufficient reproduction output cannot be obtained even if the above parameters are in the proper range. Therefore, the metal magnetic thin film 23
The film thickness is preferably 100 nm or more, and 100-200 nm is appropriate in consideration of productivity.

The magnetic recording medium having the above structure is manufactured by sequentially forming the Ge underlayer 22 and the metal magnetic thin film 23 on the nonmagnetic support 21.

Here, the metal magnetic thin film is a vapor deposition type magnetic recording medium and is usually used. For example, the film is formed by a vacuum vapor deposition device having a structure as shown in FIG.

That is, in the vacuum vapor deposition apparatus shown in FIG. 4, the inside of the vacuum chamber 1 evacuated from the exhaust ports 15 provided at the head and the bottom is placed in a vacuum state, in the clockwise direction in the figure. A feed roll 3 that rotates at a constant speed and a take-up roll 4 that rotates at a constant speed in the clockwise direction in the figure are provided, and the non-magnetic support 21 is tape-shaped from the feed roll 3 to the take-up roll 4 in sequence. It is designed to run.

A cooling can 5 having a diameter larger than the diameter of each of the rolls 3 and 4 is provided in the middle of the traveling of the non-magnetic support 21 from the feed roll 3 to the winding roll 4 side. There is. The cooling can 5 is provided so as to draw the non-magnetic support member 21 downward in the drawing, and is configured to rotate at a constant speed in the clockwise direction in the drawing. The feed roll 3, the take-up roll 4 and the cooling can 5 each have a cylindrical shape having a length substantially the same as the width of the non-magnetic support 21, and the cooling can 5 has an internal structure. A cooling device (not shown) is provided so that deformation of the non-magnetic support 21 due to temperature rise can be suppressed.

Therefore, the non-magnetic support 21 is sequentially fed from the feed roll 3, passes through the peripheral surface of the cooling can 5, and is wound up by the winding roll 4. Guide rolls 6 and 7 are provided between the feed roll 3 and the cooling can 5 and between the cooling can 5 and the take-up roll 4, respectively. A predetermined tension is applied to the non-magnetic support 21 that runs from the cooling can 5 to the winding roll 4, so that the non-magnetic support 21 runs smoothly. A crucible 8 is provided below the cooling can 5 in the vacuum chamber 1, and a metal magnetic material 9 is filled in the crucible 8. The crucible 8 has a width substantially the same as the width of the cooling can in the longitudinal direction.

On the other hand, an electron gun 10 for heating and evaporating the metallic magnetic material 9 filled in the crucible is attached to the side wall of the vacuum chamber 1. This electron gun 10
Is arranged at a position such that the electron beam emitted from the electron gun 10 irradiates the metallic magnetic material 9 inside the crucible 8. The metallic magnetic material 9 evaporated by the electron gun 10 is deposited and formed as a magnetic layer on the non-magnetic support 21 that runs at a constant speed on the peripheral surface of the cooling can 5. Further, a shutter 13 is arranged between the cooling can 5 and the crucible 8 and near the cooling can 5. The shutter 13 is formed so as to cover a predetermined area of the non-magnetic support 21 that runs at a constant speed on the peripheral surface of the cooling can 5, and the metal magnetic material 9 evaporated by the shutter 13 is supported by the non-magnetic support. It is adapted to be obliquely deposited on the body 21 within a predetermined angle range. Further, during such vapor deposition, oxygen gas is supplied to the surface of the non-magnetic support 21 through the oxygen gas inlet 14 provided penetrating the side wall of the vacuum chamber 1 to provide magnetic properties, durability and weather resistance. The sexuality is being improved.

In this vacuum vapor deposition apparatus, while maintaining the vacuum chamber 1 at a vacuum degree of, for example, 1 × 10 ^-2 Pa, oxygen gas is introduced into the vacuum chamber 1 at a rate of, for example, 0.25 liter / min through the gas inlet 14. It will be done while introducing. In this case, the incident angle of the evaporated metal with respect to the non-magnetic support 21 is 45, for example.
The range is up to 90 °.

As the metal magnetic material formed by such a vacuum vapor deposition apparatus, any of those generally used in vapor deposition type magnetic recording media can be used. For example, ferromagnetic metals such as Fe, Co and Ni, Fe-Co,
Co-Ni, Fe-Co-Ni, Fe-Cu, Co-C
u, Co-Au, Co-Pt, Mn-Bi, Mn-A
1, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co
Examples include ferromagnetic alloys such as —Cr, Co—Ni—Cr, and Fe—Co—Ni—Cr, and further Ci—Ni—O, Co—O and the like. Of these, especially Co-Ni and Co-Ni-
O and Co-O are suitable. The metal magnetic thin film may be a single layer film or a multilayer film of these.

On the other hand, Ge formed on the lower surface of the metal magnetic thin film
The underlying film is formed by sputtering, vacuum deposition, CVD,
The film is formed by an ion plating method or the like.

Of these, for example, in the case of forming a film by the vacuum evaporation method, an evaporation apparatus having the same structure as that of forming a metal magnetic thin film may be used and only the evaporation source may be changed to Ge. When forming a film by sputtering, a sputtering device as shown in FIG. 5 is used.

In the above sputtering apparatus, as shown in FIG. 5, the inside of the vacuum chamber 31 is evacuated from the exhaust ports 45 provided at the head and the bottom, respectively.
A feed roll 33 that rotates at a constant speed in the clockwise direction in the figure,
A winding roll 34 that rotates at a constant speed in the clockwise direction in the drawing is provided.
4, a tape-shaped non-magnetic support 21 on which a metal magnetic thin film is formed is sequentially run.

From the feed roll 33 to the take-up roll 3
A sputter anode can 35 having a diameter larger than the diameter of each of the rolls 33 and 34 is provided in the middle of the nonmagnetic support 21 on the fourth side. The sputter anode can 35 functions as an anode for causing glow discharge, is provided so as to pull out the nonmagnetic support 21 downward in the drawing, and rotates at a constant speed in the clockwise direction in the drawing. It is configured to do.

The roll 33 and the take-up roll 34 are used.
The sputter anode can 35 and the sputter anode can 35 each have a cylindrical shape having a length substantially equal to the width of the non-magnetic support 21, and the sputter anode can 35 includes:
A cooling device (not shown) is provided inside so that deformation of the non-magnetic support 21 due to temperature rise can be suppressed.

Further, guide rolls 36 and 37 are provided between the feed roll 34 and the sputter anode can 35 and between the sputter anode can 35 and the take-up roll 34, respectively. From the feed roll 33 to the sputter anode can 35 and from the sputter anode can 35 to the take-up roll 34.
A predetermined tension is applied to the non-magnetic support 21 that travels over the entire length of the non-magnetic support 21 so that the non-magnetic support 21 travels smoothly.

In the vacuum chamber 31, the DC power source 4
A plate-shaped sputter cathode portion 38 connected to the nozzle 6 is provided below the sputter anode can 35 so as to face the sputter anode can 35. Ge serving as a target 39 is adhered and fixed to the upper surface of the sputter cathode portion 38.

In this sputtering apparatus, the vacuum chamber 31
By introducing the sputtering gas into the inside through the gas introducing port 44 and applying a voltage between the sputtering cathode portion 38 and the sputtering anode can 35,
Glow discharge occurs. As a result, the sputter gas introduced into the vacuum chamber 31 is ionized and collides with the surface of the target 39 adhered and fixed on the sputter cathode portion 38, and sputter particles are knocked out. These sputtered particles are deposited on the metal magnetic thin film to form a sputtered film.

The Ge underlayer film and the metal magnetic thin film are once formed on the entire surface of the non-magnetic support by using the sputtering apparatus and the vacuum evaporation apparatus which are independently configured as described above. After that, a metal magnetic thin film is formed on this by two lines. Here, as shown in FIG. 6, a two-chamber type vacuum vapor deposition device in which both a vapor deposition chamber 81a for depositing a Ge underlayer film and a vapor deposition chamber 81b for depositing a metal magnetic thin film are arranged side by side, or FIG. As shown in (2), if a sputtering-vapor deposition apparatus in which a sputtering chamber 101 for forming a Ge underlayer film and a vapor deposition chamber 102 for forming a metal magnetic thin film are provided above and below, two layers are continuously formed in-line. be able to.

That is, in the two-chamber type vapor deposition apparatus shown in FIG. 6, the vacuum chamber 92, which has been evacuated from the vacuum exhaust port 83 and whose inside has been vacuum-deposited, is partitioned into left and right by the partition plate 82, and the left side in the figure is Ge. Deposition chamber 81a for forming a base film,
On the right side is a vapor deposition chamber 81b for depositing a metal magnetic thin film.

In this vapor deposition apparatus, the feed roll 84 is Ge
It is arranged in the vapor deposition chamber 81a for forming the base film, and the winding roll 85 is arranged in the vapor deposition chamber 81b for forming the metal magnetic thin film. The partition plate 82 for partitioning the two vapor deposition chambers 81a and 81b is provided with a window portion 93, and a guide roll 86 is provided at a position corresponding to the window portion 93. Therefore, the non-magnetic support member 21 is attached to the feed roll 8
4, it travels along the guide roll 86 and the winding roll 85, and at that time, it is sequentially transferred to both the vapor deposition chamber 81a for forming the Ge underlayer film and the vapor deposition chamber 81b for forming the metal magnetic thin film. .

In the vapor deposition chamber 81a for depositing the Ge underlayer and the vapor deposition chamber 81b for depositing the metal magnetic thin film, the non-magnetic support is thus transferred to the cooling cans 87a and 87, respectively.
b is provided. These cooling cans 87a, 87b
Is a part of the non-magnetic support 21 running from the feed roll 84 to the guide roll 86 side and the guide roll 86.
The non-magnetic support bodies 21 are provided so as to be pulled out in the middle of traveling from the take-up roll 85 side.

Further, a vapor deposition chamber 81 for forming a Ge base film.
a, crucibles 88a and 88b are provided below the cooling cans 87a and 87b in the vapor deposition chamber 81b for depositing the metal magnetic thin film, and the respective vapor deposition sources, that is, the Ge underlayer film depositions are formed in these crucibles 88a and 88b. In the vapor deposition chamber for
A metal magnetic material is filled in the deposition chamber for forming the metal magnetic thin film. Then, in each of the vapor deposition chambers 81a and 81b, electron guns 89a and 89b for heating the vapor deposition source, shutters 90a and 90b, and oxygen introduction ports 91a and 91b are provided, respectively, as in the case of the vapor deposition device described above. There is.

In such a two-chamber type vapor deposition apparatus, while the non-magnetic support 21 is fed from the feed roll 84 and wound on the take-up roll 85, the vapor deposition chamber 81a for forming the Ge underlayer film and the metal magnetic material are formed. The vapor deposition chamber 81b for forming a thin film is sequentially passed. In the vapor deposition chamber 81a for depositing a Ge underlayer, Ge vaporized by an electron gun is deposited and formed on the non-magnetic support 21 as an underlayer, and then in the vapor deposition chamber 81b for depositing a metal magnetic thin film, Ge underneath is deposited. A metallic magnetic material is deposited and formed as a magnetic layer on the formation film. That is, the Ge base film and the metal magnetic thin film are continuously formed in-line. The vapor deposition apparatus having the plurality of vapor deposition chambers 81a and 81b may be used when the metal magnetic thin film has a two-layer structure.

On the other hand, the sputtering-vapor deposition apparatus shown in FIG. 7 has the basic configuration of the vapor deposition apparatus shown in FIG. 4, and the vapor deposition apparatus is provided with the intermediate chambers 120 on the left and right with the cooling can interposed therebetween. It is divided into upper and lower parts. However, in this case, the cooling can 122 has a function as a sputter anode during sputtering.

The lower part of the upper and lower chambers is a vapor deposition chamber 124 for depositing a metal magnetic thin film. In the vapor deposition chamber 124, the lower half of the cooling can 122 projects from the upper side, and the crucible 108 filled with the metallic magnetic material 109, the electron gun 110, and the shutter 11
3. The oxygen introducing port 114 is arranged in the same manner as the vapor deposition device of FIG.

On the other hand, above this apparatus is a sputtering chamber 125 for forming a Ge underlayer.
In this sputtering chamber 125, the cooling can 122 projects from the lower side, and the feed roll 103, the winding roll 104, and the guide rolls 106 and 107 are arranged in the same manner as the vapor deposition device of FIG. Sputtering cathode 119 with Ge126 fixed
A sputter gas introduction pipe 117 for introducing sputter gas such as Ar and Ar is provided. Sputter cathode 11
9 is provided in the vicinity of the feed roll 103 side of the cooling can 122, and the sputter gas introduction pipe 117 is provided so as to penetrate the side wall of the vacuum chamber. Further, a conductance valve 121 is provided at the exhaust port 115 of the sputtering chamber 125.

The intermediate chamber 120 between the vapor deposition chamber 124 and the sputtering chamber 125 divides the vacuum chamber 101 into upper and lower chambers, and the vapor deposition chamber 124 and the sputtering chamber 12 are separated from each other.
It is for giving a differential pressure between 5 and. That is, in this device, the intermediate chambers 12 are placed on the left and right with the cooling can 122 interposed therebetween.
0 is provided, and an intermediate chamber exhaust port 116 is connected to each of the intermediate chambers 120. The exhaust of the vapor deposition chamber 124 is made from the intermediate chamber exhaust port 116 connected to it via the intermediate chamber 120 on the left side in the figure, and the exhaust of the sputtering chamber 125 is connected to it via the intermediate chamber 120 on the right side in the figure. The intermediate chamber exhaust port 116 is opened. Therefore, the vacuum levels in the vapor deposition chamber 124 and the sputtering chamber 125 can be made different by controlling the exhaust from the intermediate chamber exhaust ports 116 separately. For example, it is possible to adjust the vapor deposition chamber to 10 ^-3 Pa level and the sputtering chamber to 10 ^-1 Pa level when the conductance valve is closed.

In such a sputtering-vapor deposition apparatus, the non-magnetic support 21 is wound from the feed roll 103 to the take-up roll 104 while the sputtering chamber 12 is being wound.
5 and the vapor deposition chamber 124 in order. Sputtering room 1
In 25, target particles knocked out from the Ge target are deposited and formed on the non-magnetic support 21 as a base film, and then in the vapor deposition chamber 124, the metallic magnetic material evaporated by the electron gun is deposited and formed as a magnetic layer. To be done. That is, the Ge base film and the metal magnetic thin film are continuously formed in-line.

The non-magnetic support 21 on which the Ge underlayer 22 and the metal magnetic thin film 23 are formed is as follows.
Generally, any of those used in magnetic recording media can be used. For example, polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose triacetate,
Cellulose diacetate, cellulose derivative such as cellulose butyrate, vinyl-based resin such as polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyimide,
Examples include plastics such as polyamide-imide.

A plurality of fine surface protrusions may be formed on the non-magnetic support 21 for the purpose of controlling the surface property of the medium by the layered action. These surface protrusions are
A filler of a predetermined size is dispersed in the raw material (chip) of the non-magnetic support, aggregated at a predetermined density and raised on the surface of the non-magnetic support to make the surface of the non-magnetic support uneven. Or a method of dispersing fine particles having a predetermined particle size at a predetermined density on the non-magnetic support and fixing the fine particles with a binder resin or the like. Examples of the filler include SiO ₂ particles and water-soluble latex.

The above is the basic structure of the magnetic recording medium of the present invention. In this case as well, a lubricant, an anticorrosive agent, etc. are formed on the metal magnetic thin film in the same manner as in the ordinary vapor deposition type magnetic recording medium. By further providing the top coat layer or the back coat layer on the surface of the non-magnetic support opposite to the side on which the metal magnetic thin film is formed, the characteristics may be further improved. As the material for the lubricant, rust preventive, and back coat layer, any of the commonly used materials can be used.

[0057]

In a magnetic recording medium in which a metal magnetic thin film formed by a vapor deposition method is formed on a non-magnetic support,
If a Ge underlayer is provided between the non-magnetic support and the metal magnetic thin film and the value of ΔHc / Hc of the metal magnetic thin film is less than 0.25, the output in the short wavelength region increases.

The value of ΔHc / Hc of the metal magnetic thin film is Ge.
It is controlled by the thickness of the underlayer and the easy axis of magnetization of the metal magnetic thin film. By setting the thickness of this Ge underlayer film to 4 to 25 nm and setting the easy axis of magnetization of the metal magnetic thin film to 0 to 70 ° with respect to the film normal direction, the value of ΔHc / Hc becomes less than an appropriate value of 0.25. .

As described above, ΔHc / of the metal magnetic thin film is
When the value of Hc is set to less than 0.25 and the thickness of the metal magnetic thin film is set to 100 nm or more, the reproduction output is further increased. However, considering productivity, the upper limit of the thickness of the metal magnetic thin film is preferably 200 nm.

[0060]

EXAMPLES Preferred examples of the present invention will be described below based on experimental results.

Example 1 First, a polyethylene terephthalate film having a thickness of 10 μm and a width of 150 mm was coated with a fine particle dispersion in which a water-soluble latex containing an acrylic ester as a main component was dispersed to obtain a density of 10 million pieces / mm ^2. Surface protrusions were formed.

Next, a 10 nm-thickness G film was formed on the surface of the polyethylene terephthalate film on which the surface protrusions were formed.
e The underlayer film was formed by the DC magnetron sputtering method. The sputtering conditions are as follows.

Sputtering conditions Target: Ge Sputtering method: DC magnetron sputtering Sputtering power: 11 w / cm ² Sputtering gas: Ar Vacuum degree: 0.5 Pa Then, a Co- film having a film thickness of 200 nm was formed on the Ge underlayer.
A Ni vapor deposition film was formed. The vapor deposition conditions are as follows.

Deposition conditions Deposition source: Co80-Ni20 ingot (however, the numbers indicate the content of each element by weight%) Incident angle: 45 to 90 ° Running speed of non-magnetic support: 0.17 m / Sec Magnetic layer thickness: 0.2 μm Oxygen introduction rate: 3.3 × 10 ⁻⁶ m ³ / sec Vacuum degree during vapor deposition: 7 × 10 ⁻² Pa A Ge underlayer film and a Co—Ni vapor deposition film are formed as described above. After forming the film, a backcoat layer made of carbon and a urethane binder was applied to the surface of the non-magnetic support opposite to the side on which each of these films was formed, to form a backcoat layer.

Then, a top coat layer was formed by coating perfluoropolyether as a lubricant on the Co-Ni vapor-deposited film, and cut into a width of 8 mm to prepare a magnetic tape.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1 except that the Ge underlayer film was not formed. Note that this configuration is a commercially available ME
It has the same structure as the tape.

With respect to the magnetic tape manufactured as described above, the reproduction output at ΔHc / Hc and wavelength of 0.50 μm was examined. Table 1 shows the results.

ΔHc and Hc were measured using a magnetic vibration type magnetometer (VSM). The reproduction output was measured using a modified machine in which an 8 mm VTR was modified for evaluation. However, the dB value in the table is a relative value when the reproduction output of Comparative Example 1 is 0 dB.

[0069]

[Table 1]

As shown in Table 1, the magnetic tape of Example 1 provided with the Ge underlayer has a small ΔHc / Hc of 0.15 and a large reproduction output as compared with the magnetic tape of Comparative Example 1. Has become.

From this, it is found that forming the metal magnetic thin film on the Ge underlayer is effective in improving the orientation of the magnetic layer and obtaining a magnetic tape exhibiting a large output in the short wavelength region. It was

Examination of Film Thickness of Ge Underlayer Film A magnetic tape was prepared in the same manner as in Example 1 except that the film thickness of the Ge underlayer film was changed as shown in Table 2. ΔHc / H
The reproduction output at c and a wavelength of 0.50 μm was examined. The results are shown in Table 2 together with the thickness of the Ge base film. However, the dB value in the table is a relative value when the reproduction output of Comparative Example 1 is 0 dB.

[0073]

[Table 2]

As can be seen from Table 2, if the Ge underlayer film is too thin or too thick, ΔHc / Hc becomes a large value and the reproduction output deteriorates. And, it is Ge that ΔHc / Hc falls within an appropriate range, that is, less than 0.25 (less than)
It is determined that the thickness of the base film is 4 to 25 nm. Therefore, it is appropriate that the thickness of the Ge underlayer film is 4 to 25 nm.

Examination of the easy axis of magnetization of the metal magnetic thin film By controlling the incident angle of vapor deposition particles when forming the Co—Ni vapor deposition film, the easy axis of magnetization of the Co—Ni vapor deposition film is shown in Table 3.
A magnetic tape was produced in the same manner as in Example 1 except that the magnetic tape was changed as shown in FIG. Then, the produced magnetic tape was examined for reproduction output at ΔHc / Hc and a wavelength of 0.50 μm. Table 3 shows the results. However, dB in the table
The value is 8 with the easy axis of magnetization of the Co-Ni vapor-deposited film taken from the film normal direction.
This is a relative value when the reproduction output of the magnetic tape set to 0 ° is set to 0 dB.

[0076]

[Table 3]

As can be seen from Table 3, the smaller the easy axis of magnetization of the Co—Ni vapor-deposited film, the smaller ΔHc / Hc and the larger the reproduction output. Then, ΔHc / Hc is 0.
It becomes less than 25 when the easy axis of magnetization of the Co—Ni vapor deposition film is 70 ° or less from the film normal direction. From this,
It can be seen that it is suitable that the easy axis of magnetization of the metal magnetic thin film is 70 ° from the film normal direction.

Examination of Film Thickness of Metal Magnetic Thin Film A magnetic tape was produced in the same manner as in Example 1 except that the film thickness of the Co—Ni vapor deposition film was changed as shown in Table 4. The wavelength of the manufactured magnetic tape is 0.50μ.
The reproduction output at m was examined. The results are shown in Table 4. However, the dB value in the table is the film thickness of the Co—Ni vapor deposition film of 300 n.
This is a relative value when the reproduction output of the magnetic tape with m is 0 dB.

[0079]

[Table 4]

As can be seen from Table 4, the reproduction output is Co-
It becomes smaller as the film thickness of the Ni vapor deposition film becomes thinner. Therefore, the thicker the film thickness of the Co—Ni vapor-deposited film is, the better, in order to obtain a large reproduction output. Therefore, in consideration of these factors, the film thickness of the metal magnetic thin film is 100 to 200 n.
A value of m is suitable.

[0081]

As is clear from the above description, in the magnetic recording medium of the present invention, a magnetic recording medium in which a metal magnetic thin film formed by a vapor deposition method is formed on a non-magnetic support, A Ge underlayer is provided between the non-magnetic support and the metal magnetic thin film, and the value of ΔHc / Hc of the metal magnetic thin film is restricted to less than 0.25, so that the Hk distribution is small and a large output is obtained in the short wavelength region. Obtainable. Therefore, it greatly contributes to high density recording of the vapor deposition type magnetic recording medium.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an essential part showing one structural example of a magnetic recording medium to which the present invention is applied.

FIG. 2 is an M− for explaining a coercive force distribution ΔHc / Hc.
It is a characteristic view which shows H loop.

FIG. 3 is a characteristic diagram showing a relationship between ΔHc / Hc and output.

FIG. 4 is a schematic diagram showing one configuration example of a vapor deposition device for forming a metal magnetic thin film.

FIG. 5 is a schematic view showing one configuration example of a sputtering apparatus for forming a Ge underlayer film.

FIG. 6 is a schematic view showing a two-chamber type vapor deposition device for continuously forming a Ge underlayer film and a metal magnetic thin film.

FIG. 7 is a schematic diagram showing a sputtering-vapor deposition apparatus for continuously forming a Ge underlayer film and a metal magnetic thin film.

[Explanation of symbols]

 21 non-magnetic support 22 Ge underlayer 23 metal magnetic thin film

Claims (6)

[Claims] 1. A magnetic recording medium comprising a nonmagnetic support and a metal magnetic thin film formed by vapor deposition on the nonmagnetic support, wherein a Ge underlayer is provided between the nonmagnetic support and the metal magnetic thin film. And a value of coercive force distribution ΔHc / Hc of the metal magnetic thin film is less than 0.25. 2. The magnetic recording medium according to claim 1, wherein the Ge underlayer has a thickness of 4 to 25 nm. 3. The magnetic recording medium according to claim 1, wherein the easy axis of magnetization of the metal magnetic thin film is tilted by 0 to 70 ° with respect to the film normal direction. 4. The magnetic metal thin film is Co-Ni, Co-Ni.
The magnetic recording medium according to any one of claims 1 to 3, which is made of -O or Co-O. 5. A metal magnetic thin film having a thickness of 100 to 200 n.
The magnetic recording medium according to any one of claims 1 to 4, wherein m is m. 6. The magnetic recording according to claim 1, wherein the Ge underlayer film is formed by any one of a sputtering method, a vacuum evaporation method, a CVD method and an ion plating method. Medium.