JP2002119837A - Dispersing device and method of manufacturing magnetic recording medium using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly disperse fine particulate powder in a binder. SOLUTION: A spacer 5 has a cross section, which has a nearly circular shape in a direction crossing the shaft 3 at the right angle and in which the diameter of the nearly circular cross section is decreased continuously toward the midpoint of an adjacent disk 4. As a result, the difference of the cross-sectional area in the direction crossing the shaft 3 corresponding to the position of a rotary body 10 arises to cause the difference of the peripheral velocity corresponding to the position. At this time, beads are moved along the side face shape of the spacer 5 from a place where the peripheral velocity is slow to a place where the peripheral velocity is fast. Then, the circulation flow of the beads is formed inside the vessel 2, the share force is increased to enable to highly disperse the fine particulate powder with high efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dispersing device for uniformly dispersing a paint and a method for manufacturing a magnetic recording medium using the dispersing device.

[0002]

2. Description of the Related Art A dispersing device is used when a fine particle powder is kneaded in a binder by a kneading device and then highly dispersed in the binder. For example, a ferromagnetic powder is used. It is used when preparing a magnetic paint.
In other words, in order to make a ferromagnetic powder into a coating material and obtain a magnetic recording medium having excellent electromagnetic conversion characteristics, a powder such as a ferromagnetic powder and a binder are kneaded by a kneading device having a high shearing force. After that, it has been conventionally performed to send the magnetic paint to a dispersing device and uniformly disperse it.

As this dispersing device, for example, a disk type dispersing device 100 as shown in FIG. 7 can be mentioned. The disk-type dispersion apparatus 100 includes a cylindrical container 101.
A plurality of disks 102 are arranged in the
2 is configured to rotate via a shaft 103, and the inside of the container 101 is filled with a large number of beads (not shown). For this reason, the magnetic paint supplied from the paint supply port 104 is sent downstream while riding on the circulating flow of beads formed by the rotation of the disk 102, and during this time,
The magnetic coating flow is dispersed by the shearing force due to the rotation of the disk 102 and the shearing force due to collision with the beads, and is taken out from the paint outlet 105.

[0004]

However, in the disk-type dispersing apparatus 100, the energy conversion into beads is performed while the friction between the surface of the disk 102 and the beads is interposed, and the peripheral speed difference on the surface of the disk 102 and the centrifugal force associated therewith. Produced by a gradual increase in power. For this reason,
The energy conversion area is limited to a very limited area near the surface of the disk 102 and the tip, and the other containers 1
The majority of 01 is only associated with the energy conversion to beads near the surface of the disk 102. Especially axis 1
In the vicinity of 03, the peripheral speed is extremely low in spite of the fact that the shaft 103 is rotating at a high speed, so that there is almost no movement of the beads except for a partial rotational movement due to the contact with the shaft 103. As described above, the movement of the beads near the shaft 103 is poor, so that the dispersion of the magnetic paint in the disk-type dispersion device 100 becomes insufficient.

In recent years, digitization has been rapidly developed, and the demand for higher density of magnetic recording media has been further increased. For this reason, there is a further demand for a highly efficient and highly dispersed magnetic paint. If it is possible to improve the shearing force in the disk-type dispersing machine 100, it is possible to sufficiently disperse the magnetic paint, and it becomes easy to meet the demand for higher density of the magnetic recording medium.

In order to solve the above-mentioned problem, a so-called annular type disperser is used in which most of the volume of the container is an effective shear area. However, a large investment is required to introduce an annular type disperser.
In addition, there is a need to remove the existing disk-type dispersing apparatus, which requires complicated work.

[0007] The present invention has been proposed in view of the above-mentioned conventional circumstances, and it has been proposed that dispersion of paints can be made high by improving the movement of beads, and high efficiency and cost can be reduced. It is intended to provide a device. Also, the present invention, by using such a dispersion device,
An object of the present invention is to provide a method for manufacturing a magnetic recording medium having excellent electromagnetic conversion characteristics.

[0008]

According to the present invention, there is provided a dispersion apparatus having a cylindrical shape having a paint supply port at one end and a paint outlet at the other end. And the container, inside the container, while being rotatable via an axis passing through the center of the circular surface portion,
A plurality of substantially disk-shaped disks disposed at predetermined intervals in the axial direction, and are disposed between the disks, respectively, and are rotatable via the shaft, and are orthogonal to the shaft. And a spacer having a substantially circular cross section in a direction in which the diameter of the substantially circular cross section is continuously reduced toward an intermediate point of an adjacent disk. And
The inside of the container is filled with a plurality of beads,
By rotating the plurality of disks and spacers via the shaft, the plurality of beads disperse the paint while forming a circulating flow between the container and the plurality of disks and spacers. Features.

In the dispersing apparatus according to the present invention having the above-described structure, the disk is rotatable between the plurality of disks via the shaft, and has a substantially circular cross section in a direction perpendicular to the shaft. A spacer having a shape in which the diameter of the substantially circular cross section continuously decreases toward the midpoint of the adjacent disk is provided. Therefore, in this dispersing device, it is possible to form a good circulation flow between the plurality of disks and the spacers.
The shearing force is high, and the coating material can be uniformly dispersed.

Further, according to the present invention, there is provided a magnetic recording medium manufacturing method, wherein the paint supply port is provided at one end and a paint outlet is provided at the other end. A container, inside the container, rotatable via a shaft passing through the center of the circular surface portion, and a plurality of substantially disk-shaped disks arranged at predetermined intervals in the axial direction, Each of the plurality of disks is disposed between the plurality of disks, is rotatable via the shaft, and has a substantially circular cross-sectional shape in a direction perpendicular to the shaft. And a spacer having a shape that becomes continuously smaller toward the middle point of the container, using a dispersing device filled with a plurality of beads inside the container, and supplying a magnetic material as the paint from the paint supply port. Via the above axis By rotating the plurality of disks and spacers, the plurality of beads disperse the paint while forming a circulating flow between the container and the plurality of disks and spacers, and then from the paint outlet. The paint thus taken out is applied on a non-magnetic support.

In the method of manufacturing a magnetic recording medium according to the present invention, the cross-sectional shape in a direction perpendicular to the axis is substantially circular, and the diameter of the substantially circular cross-section is continuously increased toward an intermediate point of an adjacent disk. The movement of the beads is improved by the provision of spacers that are made smaller, and the ferromagnetic powder is made into a paint using a dispersing device with improved shearing force, so that a highly dispersed magnetic paint can be used. It is made. Then, by applying the highly dispersed magnetic paint on a non-magnetic support, a magnetic recording medium having excellent electromagnetic conversion characteristics can be manufactured.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the following examples, and it goes without saying that the present invention can be arbitrarily changed without departing from the gist of the present invention.

First, a distribution apparatus to which the present invention is applied will be described. Here, a method of dispersing the magnetic paint by a dispersing device will be described as an example.

As shown in FIG. 1, a disk type dispersing apparatus 1 to which the present invention is applied is rotatable via a cylindrical container 2 and a shaft 3 passing through the center of a circular surface portion 2a inside the container 2. A plurality of substantially circular disks 4 disposed at predetermined intervals in the direction of the axis 3, a spacer 5 disposed between the disks 4, and a plurality of disks 4 accommodated in the container 2. Beads (not shown).

The container 2 has a paint supply port 6 at one end.
And a paint outlet 7 is provided at the other end. The side of the container 2 where the paint outlet 7 is provided (hereinafter referred to as “back side”, and the side of the container 2 where the paint supply port 6 is provided is referred to as “front side”).
Is provided with a bead separator 9 having a gap (slit) 8 smaller than the diameter of the bead.

The paint supply port 6 is a portion for supplying the magnetic paint after the kneading process, and is connected to a magnetic paint supply device (not shown). The paint outlet 7 is a portion for taking out the magnetic paint dispersed in the container 2. The bead separator 9 has a slit 8 formed to be narrower than the bead, so that when the magnetic paint dispersed in the container 2 is taken out from the paint outlet 7, the beads are discharged out of the container 2. To prevent.

The disk 4 and the spacer 5 are made of various metals,
It can be formed of various plastics represented by polyethylene, ceramics, and the like. In the present embodiment, the disk 4 is formed of polyethylene. The disk 4 and the spacer 5 disperse the magnetic paint by rotating about the axis 3.

As shown in FIG. 2, the spacer 5 has a substantially circular cross section in a direction perpendicular to the axis 3, and the diameter of the substantially circular cross section increases toward the intermediate point P of the adjacent disk 4. The shape is continuously and linearly reduced. In other words, two truncated cones as shown in FIG. 3 are formed by connecting the circular surfaces of the smaller diameters to form an integrated shape.

The angle θ between the center line connecting the centers of the two circular surface portions of the spacer 5 and the oblique side (hereinafter referred to as the inclination angle θ) is preferably 1 ° or more, and is preferably 5 ° to 30 °.
It is more preferable that the angle be set to °. If the inclination angle θ is too large, the bead density near the spacer 5 decreases, and the bead density near the inner wall of the container 2 increases. This allows
The movement of the bead itself is restricted, and an increase in bead friction is induced, resulting in insufficient dispersion and the occurrence of contamination at the same time. In the present embodiment, the inclination angle θ is set to 10 °.

The shaft 3 passes through the center of the disk 4 and the spacer 5. The shaft 3 protrudes from the center of the disk 4 and the spacer 5, penetrates the bead separator 9 and the side surface 2 a of the container 2, and is connected to rotation driving means such as a motor (not shown). By driving the rotation driving means, the shaft 3 rotates, and the disk 4 and the spacer 5 rotate. Hereinafter, the disk 4, the spacer 5, and the shaft 3 will be collectively referred to as a rotating body 10.

Any beads may be used as long as they are conventionally used in a dispersion apparatus. Examples thereof include steel beads, glass beads, various ceramic beads, and the like. From the viewpoint of improving the dispersion efficiency, it is preferable to use ceramic beads having a fine powdery shape and a high specific gravity. In the present embodiment, zirconia beads are used. The beads are stored in a large number in the container 2 and form a circulating flow between the plurality of disks 4 and the spacers 5 via the shaft 3.

Here, the magnetic paint dispersed by the dispersing device will be described. The magnetic paint is applied on a non-magnetic support when producing a magnetic recording medium, and is prepared by kneading a binder, ferromagnetic powder, and the like with a solvent, and then dispersing the mixture with a dispersing device.

For example, the ferromagnetic powder may be an oxide magnetic powder or a metal magnetic powder. As the oxide magnetic powder, γ-Fe ₂ O ₃ and Co-containing γ-Fe
₂ O ₃ , Fe ₃ O ₄ , Co-containing γ-Fe ₃ O ₄ , Co-deposited-F
e ₃ O ₄ , CrO _{2 and the} like. Examples of the metal magnetic powder include Fe, Co, Ni, Fe—Co, and Fe—N.
i, Fe-Co-Ni, Co-Ni, Fe-Co-B,
Fe-Co-Cr-B, Mn-Bi, Mn-Al, Fe
-Co-V and the like, and for the purpose of improving these various characteristics, Al, Si, Ti, Cr, Mn, Cu,
A metal component such as Zn may be added. Also, hexagonal ferrites such as barium ferrite, iron nitride, and the like can be used.

Further, usable metal magnetic powders include:
For example, Fe, Co, Ni, Fe-Co, Fe-Ni,
Fe-Co-Ni, Co-Ni, Fe-Co-B, Fe
-Co-Cr-B, Mn-Bi, Mn-Al, Fe-C
o-V and the like, and further, for the purpose of improving these various properties, Al, Si, Ti, Cr, Mn, Cu, Zn
And the like to which a metal component such as the above has been added.

As the binder, any of the conventionally used binders can be used, and modified or unmodified vinyl chloride resin, polyurethane resin or polyester resin can be used or used in combination. A resin, a phenoxy resin, or a thermoplastic resin having a specific use, a thermosetting resin, a reactive resin, or an electron beam irradiation-curable resin may be used in combination. As a group introduced for the modification, -SO can be used to improve the dispersibility of the ferromagnetic powder.
_{3 M, -OSO 3 M, -COOM} , -PO (OM) may be ₂ or the like (M is an alkali metal atom such as Na, M 'is the alkali metal atom or an alkyl group).

Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, and the like.
Ethyl lactate, esters such as glycol acetate monoethyl ether, ethyl ether, glycol dimethyl ether, glycol monoethyl ether, dioxane, ethers such as tetrahydrofuran, benzene, toluene,
Aromatic hydrocarbons such as xylene, methylene chloride, ethylene chloride, carbon tetrachloride, chlorohydrocarbons such as chloroform, ethylene chlorohydrin, and dichlorobenzene can be used.

If necessary, a dispersant such as lecithin, a lubricant such as stearic acid, an antistatic agent such as carbon black, a polishing agent such as a chromium oxide agent, and a rust preventive are added to the magnetic paint. You may. As the dispersant, the lubricant, the antistatic agent and the rust preventive, any conventionally known materials can be used, and there is no particular limitation.

The magnetic paint as described above is applied on a non-magnetic support, and then subjected to a magnetic field orientation treatment, drying, calendering treatment and the like to form a magnetic layer.

Examples of the non-magnetic support to which the magnetic paint is applied include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate and cellulose butyrate, and the like. In addition to vinyl resins such as vinyl chloride and polyvinylidene chloride, polymer materials such as polycarbonate, polyimide and polyamide, light metals such as aluminum alloys and titanium alloys, and ceramics such as alumina glass. When a rigid substrate such as an aluminum alloy plate or a glass plate is used for the non-magnetic support, an oxide film such as alumite treatment or a Ni-P film is formed on the substrate surface so that the surface is hardened. You may.

The configuration of the magnetic recording medium manufactured by applying the present invention is not limited to the above-described one, and may have an additional element which is usually employed for the purpose of improving characteristics. No problem. For example, a backcoat layer may be provided on the surface of the nonmagnetic support opposite to the surface on which the magnetic layer is formed, or an undercoat may be applied under the magnetic layer to control the surface properties of the magnetic layer. A layer may be formed.

The back coat layer is a layer in which carbon-based fine powder for imparting conductivity to the resin binder exemplified above for the magnetic coating film and inorganic pigment for controlling the surface roughness are dispersed. This is provided to improve the running property of the medium. In dispersing the back coat layer, the above-described dispersing device may be used.

In the disk-type dispersing apparatus 1 configured as described above, the rotating body 10 is rotated by the rotation driving means, and the magnetic paint is supplied from the paint supply port 6. Then, the magnetic paint circulates inside the container 2, and the magnetic paint is dispersed by the shearing force due to the rotation of the disk 4 and the shearing force generated by collision with the beads. The magnetic paint is gradually sent to the back side while being dispersed, and is taken out of the paint outlet 7 through the slit 8.

At this time, the rotation of the rotating body 10 in the container 2 causes the plurality of disks 4 and the spacers 5 to rotate.
In between the beads form a circulating flow.

The circulating flow of the beads is formed for the following reasons. Since the rotating body 10 has a shape in which the circular surfaces of the small diameters of the two truncated cones are connected to each other, the cross-sectional area in the direction orthogonal to the axis 3 varies depending on the position. For this reason, the peripheral speed of the rotating body 10 varies depending on the position. The peripheral speed of the portion having a large cross-sectional area is high, and the peripheral speed of the portion having a small cross-sectional area is low. At this time, the beads move from the lower peripheral speed to the higher peripheral speed of the rotating body 10 inside the container 2. Further, the beads move along the shape of the side surface of the spacer 5. Therefore, a circulating flow of beads is formed.

The circulating flow of beads described above is sent from the center point P of the spacer 5 as two circulating flows along the side surface of the spacer 5 in the respective directions as indicated by arrows in FIG. And then returns to the center point P after reaching the inner wall surface. Then, these two circulating flows are formed for each of the spacers 5. Since the diameter of the beads is larger than that of the slit 8, the beads do not pass through the slit 8 and go out of the container 2, and continue to circulate inside the container 2.

As described above, in the disk-type dispersion apparatus 1 to which the present invention is applied, the cross section of the spacer 5 in the direction orthogonal to the axis 3 is substantially circular, and the diameter of the cross section of this substantially circular cross section is Since the shape of the rotating body 10 is continuously and linearly reduced toward the middle point of the adjacent disk 4, the rotating body 10 has a difference in cross-sectional area in a direction perpendicular to the axis 3 depending on the location. , A difference occurs in the peripheral speed. Therefore, a circulating flow of beads is formed between the plurality of spacers and the inner wall surface inside the container 2. By forming a circulating flow of beads inside the container 2, the shearing force of the disc-type dispersing device 1 becomes good, and the magnetic paint is highly efficiently and highly dispersed.

Further, a large investment for introducing new equipment and a complicated operation for removing the existing disk type dispersing device are not required. For this reason, it becomes possible to suppress the cost for highly efficiently dispersing the magnetic paint.

As shown in FIG. 4, the shape of the spacer 5 is such that the substantially circular diameter of the cross-sectional shape in the direction perpendicular to the axis 3 is continuous and curved toward the middle point of the adjacent disk 4. May be made smaller. That is, the spacer 5 may have a pincushion shape in a cross section viewed from a direction perpendicular to the axis 3.

When the spacer 5 has the above-described shape, a circulating flow of beads as indicated by an arrow in FIG. 5 is formed inside the container 2, so that the movement of the beads is improved. For this reason, the shearing force in the disk-type dispersion device 1 is improved, and the dispersion of the magnetic paint is sufficient.

At this time, in the container 2, the beads form a circulating flow between the disk 4 and the spacer 5 by the rotation of the rotating body 10. As shown by arrows in FIG. 5, this circulating flow is sent in two directions from the center point P of the spacer 5 along the side surface of the spacer 5 as two circulating flows, and reaches the inner wall surface of the container 2 respectively. After that, it reverses and returns to the center point P. The two circulating flows are formed between the respective disks 4 and the spacers 5.

As described above, in the disk-type dispersion apparatus 1 to which the present invention is applied, the cross section of the spacer 5 in the direction orthogonal to the axis 3 is substantially circular, and the diameter of the cross section of this substantially circular cross section is Since the rotating body 10 has a shape that continuously decreases toward the middle point of the adjacent disk 4, the rotating body 10 has a difference in cross-sectional area in a direction orthogonal to the axis 3 depending on its position. A difference occurs in the peripheral speed. For this reason, a circulating flow of beads is formed between the plurality of disks and the spacers inside the container 2, so that the shearing force of the disk type dispersing device 1 becomes good, and the magnetic paint can be produced with high efficiency. Highly dispersed.

The dispersion apparatus to which the present invention is applied and the method for manufacturing a magnetic recording medium using the same have been described above.
The present invention is not limited to the above embodiment,
Various modifications are possible.

The dispersing apparatus to which the present invention is applied may be used for dispersing a paint other than a magnetic paint.

[0044]

EXAMPLE Next, in order to confirm the effects of the present invention, a magnetic tape was manufactured using a dispersing apparatus to which the present invention was applied, and a magnetic tape was manufactured using a conventional dispersing apparatus as a comparative example. The magnetic properties of the two magnetic tapes were compared. In the dispersing device, as shown in FIG. 5, the shape of the spacer has a substantially circular cross section in a direction perpendicular to the axis, and the diameter of the substantially circular cross section goes toward the middle point of the adjacent disk. Those that were continuously and curvilinearly smaller were used.

First, a magnetic paint having the following composition was prepared. <Magnetic coating composition> Metal magnetic powder 100.0 parts by weight Vinyl chloride-vinyl acetate copolymer 10.5 parts by weight Polyurethane resin 10.5 parts by weight Carbon (antistatic agent) 5.0 parts by weight Methyl ethyl ketone 150.0 parts by weight Cyclohexanone 150.0 parts by weight Next, the magnetic paint was supplied from a paint supply port of a disk-type dispersing apparatus and dispersed. The disk was rotated so that the peripheral speed was 10 m / sec at the outermost periphery of the disk.

Next, 4 parts by weight of Coronate L (manufactured by Nippon Polyurethane Co., Ltd., trade name: polyisocyanate) was added as a curing agent to the magnetic paint discharged from the paint outlet and stirred for 30 minutes. Was completed.

Next, the magnetic paint was dried to a thickness of 2 μm.
Was applied on a polyethylene terephthalate film having a thickness of 12 μm to form a coating film, and the coating film was subjected to a magnetic field orientation treatment in an undried state.

Finally, the coating film was dried, wound up, calendered, and then cut to a width of 8 mm to produce a magnetic recording medium.

Here, the magnetic recording medium (sample tape of the embodiment) manufactured as described above and the magnetic recording medium (magnetic tape) manufactured by performing a dispersion process of a magnetic paint using a conventional disk-type dispersing apparatus. The characteristics were compared with the sample tape of the comparative example).

First, when the occurrence of dropout was measured for both sample tapes, no significant difference was found between them.

When the gloss of the magnetic layers of both sample tapes was measured by a gloss meter (incident angle: 45 °), no significant difference was found between the two.

A comparison of the change in glossiness of the magnetic paint during the dispersion of the magnetic paint used in both sample tapes shows that when the disk type dispersion apparatus to which the present invention is applied is used.
The gloss disappeared in a short time, and the dispersion was completed. On the other hand, when the conventional disk-type dispersing apparatus is used, the gloss rises poorly, and it takes a long time until the gloss disappears so that the gloss becomes almost the same as when the disk-type dispersing apparatus is used.

A long dispersion time causes abrasion powder of beads to be mixed into the magnetic paint, resulting in deterioration of magnetostatic characteristics and dropout. It can be seen that the use of the disk-type dispersion apparatus to which the present invention is applied makes it less likely to cause abrasion during the dispersion treatment, so that a magnetic tape having excellent magnetostatic properties and dropout can be produced.

[0054]

According to the dispersing apparatus of the present invention, the spacer has a substantially circular cross section in a direction perpendicular to the axis, and the diameter of the substantially circular cross section is continuous toward the middle point of the adjacent disk. Due to the small size, a circulating flow of beads is formed inside the container. By forming a circulating flow of beads, the shearing force of the dispersing device becomes favorable, and the magnetic paint is highly efficiently and highly dispersed.

Further, in the method of manufacturing a magnetic recording medium according to the present invention, the cross-sectional shape in a direction perpendicular to the axis is substantially circular, and the diameter of the substantially circular cross-section increases toward the middle point of the adjacent disk. After dispersing the magnetic paint using a dispersing device having spacers that are continuously reduced in size, the magnetic paint is applied onto a non-magnetic support. Therefore, a magnetic recording medium is manufactured using a highly dispersed magnetic paint, and a magnetic recording medium having excellent electromagnetic characteristics can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram schematically showing a dispersion apparatus shown as a first embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a shape of a spacer used in the dispersion apparatus.

FIG. 3 is a perspective view showing a truncated conical shape.

FIG. 4 is a schematic configuration diagram schematically showing a dispersion apparatus shown as another embodiment of the present invention.

FIG. 5 is a schematic diagram for explaining a shape of a spacer used in the dispersion apparatus.

FIG. 6 is a cross-sectional view showing a magnetic recording medium manufactured by a method for manufacturing a magnetic recording medium to which the present invention is applied.

FIG. 7 is a schematic configuration diagram showing a conventional dispersion apparatus.

[Explanation of symbols]

1 dispersing device, 2 containers, 3 axes, 4 disks, 5
Spacer, 6 paint supply port, 7 paint discharge port, 8 slit, 9 bead separator, 10 rotating body

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B05D 5/12 B05D 5/12 A G11B 5/842 G11B 5/842 A F-term (Reference) 4D075 BB16X CA24 DA04 DA06 DB07 DB13 DB14 DB33 DB36 DB38 DB48 DB53 DC28 EA10 EB07 EB15 EB32 EB35 EB38 EC02 EC10 4F042 AA02 AA06 AA22 CA01 CA06 4G035 AB46 AB54 AE13 4G078 AA03 AB01 AB05 BA01 CA01 CA08 DA23 EA10 EA13 5D112 AA19 BB18

Claims (7)

[Claims] 1. A cylindrical container having a paint supply port provided at one end with a paint supply port and a paint outlet at the other end provided with a paint supply port, and a circular shape inside the container. A plurality of substantially disk-shaped disks arranged at predetermined intervals in the axial direction and rotatable via an axis passing through the center of the surface portion, and each of the plurality of disks is disposed between the plurality of disks. The shaft is rotatable via the shaft, and the cross-sectional shape in a direction perpendicular to the shaft is substantially circular, and the diameter of the substantially circular cross-section continuously decreases toward the middle point of the adjacent disk. A spacer having a shape, wherein a plurality of beads are filled inside the container,
By rotating the plurality of disks and spacers via the shaft, the plurality of beads disperse the paint while forming a circulating flow between the container and the plurality of disks and spacers. Dispersion device characterized. 2. The dispersing apparatus according to claim 1, wherein the spacer has a shape in which the diameter of the substantially circular cross section decreases linearly toward an intermediate point between adjacent disks. 3. The dispersion apparatus according to claim 1, wherein the spacer has a shape in which the diameter of the substantially circular cross section decreases in a curve toward an intermediate point between adjacent disks. 4. The dispersing apparatus according to claim 1, wherein said paint is made of a magnetic material. 5. A cylindrical container provided with a paint supply port at one end thereof and a paint outlet at the other end thereof, and a circular surface inside said container. And rotatable via a shaft passing through the center of the disk, a plurality of substantially disk-shaped disks arranged at a predetermined interval in the axial direction, respectively disposed between the plurality of disks, While being rotatable via the shaft, the cross-sectional shape in a direction orthogonal to the shaft is substantially circular,
A spacer having a shape in which the diameter of the substantially circular cross section is continuously reduced toward the middle point of the adjacent disk, using a dispersing device in which a plurality of beads are filled inside the container, While supplying a magnetic material as paint from the paint supply port and rotating the plurality of disks and spacers via the shaft, the plurality of beads move between the container and the plurality of disks and spacers. A method for producing a magnetic recording medium, comprising: dispersing the paint while forming a circulating flow; and applying the paint taken out from the paint outlet onto a non-magnetic support. 6. The spacer according to claim 5, wherein the spacer has a shape in which the diameter of the substantially circular cross section decreases linearly toward an intermediate point between adjacent disks. A method for manufacturing a magnetic recording medium. 7. The spacer according to claim 5, wherein the spacer has a shape in which the diameter of the substantially circular cross section decreases in a curve toward an intermediate point between adjacent disks. A method for manufacturing a magnetic recording medium.