JPH09143601A - Magnetic metallic material and production of magnetic recording medium by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic metallic material which hardly produces splashes and to provide a process for producing magnetic recording media having decreased drop-outs by using such magnetic metallic material. SOLUTION: The magnetic metallic material 9 which is small in the quantity and size of internal holes and is more specifically specified in the apparent sp. gr. to >=98% of theoretical sp. gr. is used as a raw material for forming a magnetic material thin film on one main surface of a nonmagnetic base 2. The magnetic metallic material which consists of a Co-Ni alloy and has the apparent sp. gr. of >=8.75 is used as the magnetic metallic material 9 in the case a Co-Ni alloy thin film is formed as a magnetic layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal magnetic material for forming a magnetic layer of a so-called metal magnetic thin film type magnetic recording medium, and a method of manufacturing a magnetic recording medium using the same.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a powdery magnetic material such as an oxide magnetic powder or an alloy magnetic powder has been coated on a nonmagnetic support by a vinyl chloride-vinyl acetate copolymer,
A coating type magnetic recording medium prepared by coating and drying a magnetic coating material dispersed in an organic binder such as polyester resin, urethane resin or polyurethane resin is widely used.

On the other hand, with the growing demand for high-density magnetic recording, Co-Ni alloys, Co-Cr alloys,
-O or the like, a metal magnetic material is subjected to plating or vacuum thin film forming means (vacuum vapor deposition method, sputtering method, ion plating method, etc.) to form a polyester film or polyamide,
A so-called metal magnetic thin film type magnetic recording medium directly attached on a non-magnetic support such as a polyimide film 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 short wavelengths, and the magnetic layer can be made extremely thin, so that recording demagnetization and reproduction are possible. The thickness loss at the time is extremely small,
Since there is no need 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.

Further, in order to improve the electromagnetic conversion characteristics of this kind of magnetic recording medium and to obtain a larger output, when forming the magnetic layer of the magnetic recording medium, the magnetic layer is obliquely formed. So-called oblique vapor deposition for vapor deposition has been proposed and put to practical use.

In order to obliquely deposit the magnetic layer, the metal magnetic material in the crucible is vaporized, and the incident angle of this vapor is regulated by a shutter or a mask, while the non-magnetic support is continuously running. It can be attached to.

[0007]

By the way, when the above-described vapor deposition is continuously performed for a long time, a metal magnetic material made of a desired material is sequentially supplied into the crucible. .

However, when the replenished metal magnetic material is melted in the crucible, impurities such as oxides and carbon contained in the metal magnetic material, or
The air and gas components trapped in the minute holes inside the metallic magnetic material may cause bumping (splash).

Then, the splashes caused by this splash are
When reaching the non-magnetic support, a slight heat loss occurs in the magnetic layer, which may cause a hitting failure or dropout.

Therefore, the present invention has been proposed in view of the above conventional circumstances, and an object thereof is to provide a metal magnetic material which is unlikely to cause a splash, and a dropout using such a metal magnetic material. It is an object of the present invention to provide a method for manufacturing a magnetic recording medium having a small amount of noise.

[0011]

The metal magnetic material according to the present invention has been proposed to achieve the above-mentioned object, and is for forming a metal magnetic thin film on one main surface of a non-magnetic support. It is used as a raw material of and has an apparent specific gravity of 98% or more of the theoretical specific gravity.

Here, the "apparent specific gravity" is the specific gravity actually measured from the volume and weight of the metal magnetic material having a predetermined shape. On the other hand, the "theoretical specific gravity" is the specific gravity calculated from the specific gravity of each element constituting the metal magnetic material and the content rate of the element. Therefore, if the metal magnetic material is composed of the elements A, B, C, ..., N, the theoretical specific gravity Dp is the specific gravity of the constituent elements A, B, C ,. , Dc, ... Dn, each constituent element A,
The content ratios of B, C, ..., N are Wa, Wb, Wc, respectively.
, ..., Wn can be represented by the theoretical specific gravity Dp = Da * Wa + Db * Wb + Dc * Wc + ... + Dn * Wn (1).

The apparent specific gravity of the metallic magnetic material is greatly affected by the type and content of impurities, but even if the theoretical specific gravity is calculated in consideration of the content of minute impurities, it is usually
This theoretical specific gravity does not completely match. This is because the metal magnetic material has pores, and the apparent volume increases depending on the amount and size of the pores.

That is, in order to make the apparent specific gravity of the metallic magnetic material 98% or more of the theoretical specific gravity, the amount and size of the holes may be reduced. In addition, to control the amount and size of holes,
When manufacturing the metal magnetic material having a predetermined shape, forging conditions after rolling, rolling conditions, other secondary heating conditions, and the like may be adjusted.

The above-mentioned metal magnetic material is used as a raw material for the metal magnetic thin film when the metal magnetic thin film is formed on one main surface of the non-magnetic support by the vacuum deposition method.

Usually, when forming a metal magnetic thin film, a base film (non-magnetic support) is continuously run in a film forming chamber of a vacuum evaporation system, and a predetermined metal magnetic material is placed in a crucible. The ingot made of is melted, vaporized, and deposited on the non-magnetic support. And
Since the metal magnetic material in the crucible is consumed during the film formation, it is necessary to sequentially supply the metal magnetic material into the crucible. The shape and size of the metal magnetic material supplied are arbitrary, and may be pellet-shaped, wire-shaped, or round-bar-shaped.

Since these metallic magnetic materials are supplied during film formation, it is desirable that no splash be generated when they are melted in the crucible. Therefore, in the present invention, as the metal magnetic material, a metal magnetic material having a small amount and size of pores, specifically, a material having an apparent specific gravity of 98% or more of the theoretical specific gravity is used. Since impurities such as oxides and carbon contained in the metal magnetic material also cause splash, it is desirable to reduce the impurities contained in the metal magnetic material.

The material forming the metal magnetic material may be any material that is usually used for forming a magnetic layer of a magnetic recording medium. For example, ferromagnetic metal materials such as Fe, Co and Ni, Fe-C
o, Co-Ni, Fe-Co-Ni, Fe-Cu, Co
-Cu, Co-Au, Co-Pt, Mn-Bi, Mn-
Al, Fe-Cr, Co-Cr, Ni-Cr, Fe-C
o-Cr, Co-Ni-Cr, Fe-Co-Ni-Cr
And other ferromagnetic alloy materials. The metal magnetic thin film to be formed may be a single layer film or a multilayer film using such a metal magnetic material.

For example, when a Co--Ni type alloy thin film is formed as the magnetic layer, Co--Ni is used as the metal magnetic material.
It is preferable to use an alloy made of a system alloy and having an apparent specific gravity of 8.75 or more. If the specific gravity of Co is 8.90 and the specific gravity of Ni is 8.90, the metallic magnetic material having an apparent specific gravity of 8.75 or more has a theoretical specific gravity of 98 even if it contains some impurities. It has a specific gravity of at least%.

By the way, the non-magnetic support on which the above-mentioned magnetic layer is formed is formed of a polymer material typified by polyesters, polyolefins, celluloses, vinyls, polyimides and polycarbonates. Examples thereof include a polymer substrate, a metal substrate made of an aluminum alloy and a titanium alloy, a ceramic substrate such as aluminum glass, a glass substrate, and the like, and the shape thereof is not particularly limited. However, when a magnetic tape is manufactured by applying the present invention, a polyethylene terephthalate film, a polyethylene naphthalate film, an aramid film or the like is preferably used as the non-magnetic support. In addition, a filler may be internally added to these films to control the surface roughness, or a layer for controlling the surface roughness may be formed on the surface.

Further, between the non-magnetic support and the metal magnetic thin film,
Alternatively, when the metal magnetic thin film is composed of a multilayer film, an underlayer or an intermediate layer may be provided in order to improve the adhesive force between the layers and control the coercive force. Further, for example, the vicinity of the surface of the magnetic layer may be an oxide to improve the corrosion resistance.

A protective film layer may be formed on the metal magnetic thin film, and any material may be used as long as it is generally used as a protective film for ordinary metal magnetic thin films. Good. For example, in addition to carbon, C
rO ₂ , Al ₂ O ₃ , BN, Co oxide, MgO, Si
_{O 2, Si 3 O 4,} SiN x, SiC, SiN x -Si
Examples thereof include O ₂ , ZrO ₂ , TiO ₂ , and TiC. These may be a single layer film, a multilayer film, or a composite film.

Of course, the constitution of the magnetic recording medium manufactured by applying the present invention is not limited to this, and an undercoat layer may be formed on the non-magnetic support or a non-magnetic support may be formed, if necessary. A back coat layer may be provided on the main surface of the body opposite to the surface on which the metal magnetic thin film is formed, or a top coat layer made of a lubricant or rust preventive agent may be formed on the surface of the metal magnetic thin film or protective film. You may.

[0024]

EXAMPLES Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

First, the structure of the vacuum vapor deposition apparatus used for forming the metal magnetic thin film in this embodiment will be described.

As shown in FIG. 1, in this vacuum vapor deposition apparatus, exhaust ports 1 provided at the head and bottom, respectively.
In the film forming chamber 1 which is evacuated from the chamber 5 and whose inside pressure can be reduced, a feed roll 3 which rotates at a constant speed in a direction in the figure, and b in the figure
And a winding roll 4 which rotates at a constant speed in a predetermined direction, and a tape-shaped non-magnetic support 2 sequentially runs from these feed rolls 3 to the winding roll 4.

A cooling can 5 having a diameter larger than that of each of the rolls 3 and 4 is provided in the middle of the non-magnetic support 2 running from the feed roll 3 toward the winding roll 4. There is. The cooling can 5 is provided so as to draw the non-magnetic support 2 downward in the drawing, and is configured to rotate at a constant speed in the direction c in the drawing.

The feed roll 3, the winding 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 2. Further, the cooling can 5 is provided with a cooling device (not shown) inside so that deformation of the non-magnetic support 2 due to a temperature rise can be suppressed.

Therefore, the film forming chamber 1 of this vacuum vapor deposition apparatus
In the inside, the non-magnetic support 2 is sequentially fed out from the feed roll 3, passes through the peripheral surface of the cooling can 5, and is wound up by the winding roll 4.

A crucible 8 having a width substantially the same as the width of the cooling can 5 is provided below the cooling can 5 in the film forming chamber 1, and the crucible 8 is filled with the metal magnetic material 9. Has been done. Furthermore, pellets 14 are supplied to the crucible 8 from a pellet supply means 13.

On the other hand, an electron gun 10 for heating and evaporating the metallic magnetic material 9 filled in the crucible 8 is attached to the side wall of the film forming chamber 1. The electron gun 10 is arranged at a position such that the electron beam X emitted from the electron gun 10 irradiates the metallic magnetic material 9 in the crucible 8. Then, the metal magnetic material 9 evaporated by the electron gun 10 is formed as a magnetic layer on the non-magnetic support 2 running at a constant speed on the peripheral surface of the cooling can 5.

Further, between the cooling can 5 and the crucible 8 and near the cooling can 5, a shutter 11 has a predetermined region of the non-magnetic support 2 which runs at a constant speed on the peripheral surface of the cooling can 5. Is arranged so as to cover. The shutter 11 allows the evaporated metal magnetic material 9 to be obliquely deposited on the non-magnetic support 2 within a predetermined angle range.

Further, a gas inlet 12 is provided on the side wall of the film forming chamber 1 so that a desired gas can be supplied into the film forming chamber 1 at a desired flow rate.

In order to form a metal magnetic thin film on the non-magnetic support 2 by using the vacuum vapor deposition apparatus having the above-described structure, the film forming chamber 1 is evacuated through the exhaust port 15 and a predetermined vacuum degree is obtained. On the other hand, oxygen gas is introduced from the gas inlet 12 at a predetermined flow rate for the purpose of improving the magnetic properties, durability, and weather resistance of the metal magnetic thin film. Then, the feed roll 3, the cooling can 5, and the take-up roll 4 are each rotated at a predetermined speed, and the nonmagnetic support 2 is caused to travel on the peripheral surface of the cooling can 5. Further, the metal magnetic material 9 in the crucible 8 may be heated and evaporated by the electron beam X emitted from the electron gun 10, and the shutter 11 may control the incident angle to adhere it to the traveling non-magnetic support 2. .

As the metal magnetic material 9, a material obtained by melting an ingot previously put in the crucible 8 before the start of film formation is used. However, since it is consumed by the film formation, the metal magnetic material is sequentially formed. The pellet 14 is supplied from the pellet supply means 13 here. The pellet 14 has a diameter of 10 mm and a length of 10 m.
A m-shaped cylinder was used.

Examples 1 to 5 Here, when the metal magnetic thin film is formed by using the vacuum vapor deposition apparatus having the above-described structure, the crucible 8 is formed during the film formation.
The apparent specific gravity of the magnetic metal material supplied inside was changed. Hereinafter, the process of actually manufacturing the magnetic tape will be described step by step.

First, a polyethylene terephthalate film having a thickness of 10 μm and a width of 150 mm is prepared, and in order to adjust the surface roughness of this film, a water-soluble latex containing acrylate as a main component is applied to form an undercoat layer. did. As a result, a protrusion density of 10 million pieces / mm ₂ was formed on the surface. This is the non-magnetic support 2.

Then, the film forming chamber 1 of the vacuum vapor deposition apparatus described above.
While maintaining a vacuum degree of 7 × 10 ^-2 Pa, the film forming chamber 1
Oxygen gas was introduced into the inside at a flow rate of 250 cc / min, and the nonmagnetic support 2 was run on the peripheral surface of the cooling can 5 at a speed of 25 m / min.

In the crucible 8, Co ₉₀ --Ni
₁₀ (Numbers indicate weight%.) An ingot made of an alloy was melted, and the obtained metal magnetic material 9 was evaporated. Then, this vapor is adhered to the non-magnetic support 2 with an incident angle of 45 ° to 90 °, and a metal magnetic thin film is applied to the nonmagnetic support 2.
The film was formed to a thickness of 0 nm.

During the film formation, the metal magnetic material 9 in the crucible 8 is consumed, so that the pellet feeding means 1 is sequentially used.
Pellets 14 will be replenished from No. 3, but as the pellets 14, five types (sample pellets A to E) having the same composition but different apparent specific gravities are used.

Usually, the value of apparent specific gravity is greatly influenced by the content of impurities, but the above-mentioned sample pellets A to
Since E has the same composition, it can be considered that the apparent specific gravity in this case differs depending on the amount and size of the pores inside. here,
Use the melting lot of supply so that the content of impurities becomes equal, and depending on the conditions at the time of pellet production, especially forging and rolling conditions after melting, other secondary heating conditions, etc.
The amount and size of the holes were made different.

The composition of the sample pellets A to E is shown in Table 1, and the apparent specific gravity is shown in Table 2. The apparent specific gravity was measured by a measuring instrument manufactured by Shimadzu Corporation, trade name: SGM-210U.

[0043]

[Table 1]

[0044]

[Table 2]

On the other hand, the theoretical specific gravity of the pellets having the composition shown in Table 1 was obtained by using the specific gravity of Co of 8.90, the specific gravity of Ni of 8.90 and the specific gravity of other elements as the values described in the Vacuum Handbook of the Nippon Vacuum Company. When asked, it becomes 8.894.
In Table 2, the theoretical specific gravity is set to 100%, and the percentage of the apparent specific gravity of each of the sample pellets A to E is also shown.

As described above, the sample pellets A to
After forming a metal magnetic thin film by using E, respectively,
On the surface of the non-magnetic support 2 opposite to the surface on which the metal magnetic thin film was formed, a back coat layer mainly containing carbon and a urethane-based binder was formed to a thickness of 0.6 μm. Further, a top coat layer made of perfluoropolyether was formed on the metal magnetic thin film. Then, this was cut into a width of 8 mm to obtain a magnetic tape.

Here, the magnetic tape manufactured by using the sample pellet A when forming the metal magnetic thin film was used as the sample tape of Example 1, and the magnetic tape manufactured by using the sample pellet B was used as the sample tape of Example 2. A magnetic tape manufactured using the sample tape and the sample pellet C was manufactured using the sample tape of Example 3 and a magnetic tape manufactured using the sample pellet D was manufactured using the sample tape of Example 4 and sample pellet E. The magnetic tape was used as the sample tape of Example 5.

Comparative Examples 1 and 2 In this comparative example, the metal magnetic material used to prepare the sample tapes of Examples 1 to 5 (sample pellets A to A material having an apparent specific gravity different from that of E) was used.

Specifically, when the metal magnetic thin film is formed, the sample pellets F and G having the same composition as the sample pellets A to E and the apparent specific gravities shown in Table 2 are placed in the crucible 8. A sample tape was produced in the same manner as in Examples 1 to 5 except that the sample tape was supplied. In addition,
The magnetic tape manufactured using the sample pellets F is used as the sample tape of Comparative Example 1, and the magnetic tape manufactured using the sample pellets G is used as the sample tape of Comparative Example 2.

Evaluation of Characteristics Here, the dropouts of the sample tapes of Examples 1 to 5 and Comparative Examples 1 and 2 produced as described above were measured.

This measurement is performed by a recording / reproducing device (manufactured by Sony Corporation,
Using a modified product name: EV-S900), each sample tape was reproduced and run, and the number of occurrences of dropout was counted. Here, the dropout is -16d from the reproduction output level.
It is assumed that the output deterioration of B or more continues for 10 μsec or more. The measurement is performed for 10 minutes and is shown as the number of times per minute. Table 3 shows the results.

Table 3 also shows the state of splashes that occurred during the formation of the metal magnetic thin film during the production of each sample tape. This was visually observed when the metal magnetic thin film was formed.

[0053]

[Table 3]

From Table 3, it can be seen that in the sample tapes of Comparative Example 1 and Comparative Example 2, splash occurred during film formation of the metal magnetic thin film, and the number of dropouts also increased, while Examples 1 to 1 It can be seen that in the sample tape of Example 5, the occurrence of splash at the time of forming the metal magnetic thin film is suppressed, and the number of dropout occurrences is significantly reduced.

In the sample tapes of Comparative Examples 1 and 2, the metallic magnetic material scattered by the splash reaches the non-magnetic support, and thus the heat loss can be confirmed. It was found that the metal magnetic thin film was completely missing at the place where the loss occurred. This causes a problem in product quality. Further, in these sample tapes, although not visually observed as heat loss, a large number of minute heat losses that can be confirmed by a microscope are generated, which causes dropout.

The reason why such heat loss occurs is
This is because the apparent specific gravity of the sample pellets F and G supplied into the crucible 8 at the time of film formation of the metal magnetic thin film is low, so that the amount and size of the voids inside the crucible 8 are large and the splash is likely to occur.

On the other hand, in the sample tapes of Examples 1 to 5, sample pellets A to E having a high apparent specific gravity, that is, having a small amount of pores and a small size were used to form metal magnetic thin films. Since the film is formed, the occurrence of splash is suppressed, and as a result, the occurrence of dropout is also suppressed. In particular, it can be seen that the use of the sample pellets C to E having an apparent specific gravity of 99% or more of the theoretical specific gravity makes it possible to manufacture a magnetic tape having a very small number of dropouts.

[0058]

As is apparent from the above description, pellets having an apparent specific gravity of 98% or more of the theoretical specific gravity are less likely to cause a splash at the time of melting. By doing so, it becomes possible to manufacture a magnetic recording medium in which the occurrence of dropout is suppressed.

Therefore, by applying the present invention, it is possible to provide a magnetic recording medium having a very high reliability.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration example of a vacuum vapor deposition device.

[Explanation of symbols]

 1 film forming chamber 6 non-magnetic support 5 cooling can 9 metallic magnetic material 10 electron gun 13 pellet supply means 14 pellets

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Taketoshi Sato 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (4)

[Claims] 1. A metal magnetic material, which is used as a raw material for forming a metal magnetic thin film on one main surface of a non-magnetic support and has an apparent specific gravity of 98% or more of a theoretical specific gravity. 2. The metal magnetic material according to claim 1, which is made of a Co—Ni alloy and has an apparent specific gravity of 8.75 or more. 3. When forming a metal magnetic thin film on one main surface of a non-magnetic support by a vacuum deposition method, a metal magnetic having an apparent specific gravity of 98% or more of a theoretical specific gravity as a raw material of the metal magnetic thin film. A method for manufacturing a magnetic recording medium, characterized by using a material. 4. The method of manufacturing a magnetic recording medium according to claim 3, wherein the metallic magnetic material is made of a Co—Ni alloy and has an apparent specific gravity of 8.75 or more.