JPH0687305B2 - Perpendicular magnetic recording medium manufacturing equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing a coating type perpendicular magnetic recording medium.

2. Description of the Related Art In recent years, a coating type perpendicular magnetic recording medium using hexagonal barium ferrite is more suitable for high density recording than a conventional medium using iron oxide (in-plane horizontal recording). Various applications have been investigated. In addition to the above, as a perpendicular magnetic recording medium, a method of using needle-shaped iron oxide and vertically orienting a needle-shaped magnetic material has been attempted. In any case, it is necessary to orient a material having a high magnetic anisotropy perpendicular to the surface of the coating film to form a coating film having a strong magnetic anisotropy in the vertical direction.

Regarding the alignment method, some patent documents have already been disclosed, for example, JP-A-57-127931, JP-A-57-205827,
It is described in JP-A-57-212626, JP-A-58-12130, JP-A-58-12135 and JP-A-58-12136. In other words, it is roughly divided into those using mechanical stress or magnetic force, and those using magnetic force are
It can be classified as a method of applying a DC or AC magnetic field. Further, the viscosity of the coating film is an important factor for orientation, and each devised method is disclosed in patent documents, for example, JP-A-58-121.
36, JP-A-58-203631, JP-A-58-203632, and JP-A-58-203633.

Problems to be Solved by the Invention In the above-mentioned conventional method utilizing mechanical stress as described in JP-A-58-12137, the condition for obtaining high orientation is very narrow, and the application range is Limited. That is, the magnetic substance is limited to a plate-shaped magnetic substance having an easy axis of magnetization in the direction perpendicular to the surface such as hexagonal plate-shaped barium ferrite, and it is not applicable when the acicular magnetic powder is oriented vertically. . Also, the high shear stresses required make the paint viscosity and equipment optimum very narrow.

In the conventional method using a DC magnetic field, a high magnetic field cannot be obtained unless a magnetic field is applied to the coating film when it is not dried and the coating film is not dried. However, it is extremely difficult to sufficiently control the drying that affects the surface property and structure of the coating film between the narrow magnets. Further, it is necessary to design a coating material that is not significantly affected by the drying conditions, and there is a drawback that the selection of the binder resin and the solvent is limited.

Further, the conventional method using an alternating magnetic field is effective only when it is used as an auxiliary means or when a coating composition that is extremely easy to orient is used, and there is a drawback that the orientation power is essentially weak. .

It is an object of the present invention to provide an apparatus for manufacturing a perpendicular magnetic recording medium which can solve the above-mentioned problems of the conventional technology.

According to the present invention, in a manufacturing apparatus for a perpendicular magnetic recording medium having a magnetic recording magnetic layer coated on the surface of a base substrate, the magnetic recording magnetic layer is provided on the surface of the base substrate. Coating means and, when the coated magnetic recording magnetic layer is undried, orients the easy axis of magnetization of the magnetic substance in the magnetic recording magnetic layer in a direction perpendicular to the surface of the base substrate. For this reason, different pole facing magnet means arranged so as to face the front surface of the magnetic recording magnetic layer and the back surface of the base substrate so as to sandwich them, and the coated magnetic recording passing through the different pole facing magnet means. A drying means for drying the magnetic layer from one side of the magnetic recording magnetic layer and the base substrate; and a drying means arranged only on the other side of the magnetic recording magnetic layer and the base substrate. While the magnetic recording magnetic layer is being dried by the means, the perpendicular orientation of the easy axis of magnetization of the magnetic substance in the magnetic recording magnetic layer by the different pole facing magnet means can be maintained as it is without being disturbed. And a one-sided homopolar magnet array means for applying a strong magnetic field.

Examples Next, the present invention will be described in more detail with reference to the accompanying drawings with reference to the examples of the present invention.

First, the principle of the present invention will be explained. According to the present invention,
First, the undried coating film is passed between opposing magnets of different poles to orient the easy axis of magnetization of the magnetic material in a direction perpendicular to the coating film surface, and then a portion in which an oriented magnet of the same polarity is arranged on only one side. It is possible to obtain a vertically oriented coating film by allowing the coating film to finish drying during that time. That is, in the present invention, the first opposite-polarity opposed magnet plays a role of generating a strong vertical orientation magnetic field and orienting the easy axis of magnetization of the magnetic material in the vertical direction. In addition, the part where the magnets of the same polarity on the next side only are arranged is for the purpose of maintaining the orientation state without disturbing the once oriented magnetic material, and the magnetic material is applied while the coating film passes through this portion. Let it dry until it does not move. Since the orienting magnet is present only on one side of this portion, the drying is sufficiently controlled without any restriction, and appropriate dry curing can be performed.

In the present invention, the following four types of arrangements of the oriented magnets are considered and each has its own effect.

First, the position of the magnet arranged only on one side is divided into the case where it is on the coating film side and the case where it is on the opposite surface (base film) side. This is because when controlling the drying, it may be better to apply hot air, infrared rays, ultraviolet rays, electron beams, or the like from the coating surface, and it may be better to apply it from the opposite surface. Generally, the one applied from the surface of the coating film has good drying efficiency and is often used, but the one applied from the opposite surface can prevent skinning of the surface of the coating film and can sometimes obtain a smooth surface. In any case, the present invention can be applied as described above.

Next, it is divided into two types by combining the polarities of the opposite magnets opposite to each other and the magnets arranged only on one side subsequent thereto. The first type makes the opposite magnet and the magnet arranged on one side have the same polarity, and the second type makes the opposite magnet and the magnet arranged on one side have opposite polarities.

According to the first type of combination, the magnetic substance of the obtained coating film is attracted to the magnet side arranged on one side before drying, and forms a distribution in the depth direction of the coating film. Therefore, when the magnet arranged on one side is located on the coating film surface side, the magnetic body is attracted toward the coating film surface direction. In the coating film portion close to the base film surface, the resin component is increased, so that the coating film adhesion is improved, and the magnetic substance becomes dense in the vicinity of the coating film surface to provide magnetic characteristics suitable for high density recording. Durability is greatly improved by applying a lubricant. The fact that the magnetic substance is dense in the surface layer means that the surface is porous, which is very effective.

On the contrary, when the magnet arranged on one side is located on the back surface (base film) side of the coating film, the magnetic material is attracted to the base film side, and the coating film surface contains a large amount of resin component. This has an effect similar to that of forming a resin protective layer, and the durability of the coating film is greatly improved.

Next, in the case of the second type, the magnetic body once magnetized by the opposing magnet receives a repulsive force by the magnet arranged on one side and tries to move away. At this time, if the strength of the magnet arranged on one side is large enough to magnetize the magnetic body, the magnetization of the magnetic body is instantly reversed, and the magnetic body is attracted to the magnet side as in the case described above. To be In order to exert the repulsive force, the magnetic field of the magnet arranged on one side is not strong enough to reverse the magnetization of the magnetic substance, and needs to be controlled to the strength necessary for controlling the disorder of the orientation. This method applies drying means (such as hot air) from the coating surface side to increase the density of the magnetic material on the coating surface.
It can be applied when a drying means is applied from the back surface of the coating film (base film surface) to make the resin on the coating film surface dense.

Next, an example of a specific arrangement of devices for carrying out the method of manufacturing a perpendicular magnetic recording medium based on the principle of the present invention will be described with reference to FIGS. 1 to 4.

First, FIG. 1 schematically shows a device configuration according to a first embodiment of the present invention. In this device configuration, a drying means 5A in a drying oven is arranged on the magnetic recording magnetic layer 1 side. The magnet 4A as the one-sided homopolar magnet array means is arranged on the side of the base film 2 as the base substrate, and the polarities of the magnets are the magnets 3B arranged on the side of the base film 2 of the opposite-polarity opposed magnet means. It has the same polarity as. The operation of the apparatus shown in FIG. 1 will be briefly described.
And application means arranged in front of 3B (not shown)
Thus, the magnetic recording magnetic layer 1 is applied to the surface of the base film 2. Then, the base film 2 coated with these magnetic recording magnetic layers is passed between the opposite pole facing magnets 3A and 3B, where the magnetic recording magnetic layer 1 coated when it is undried. The easy axis of magnetization of the magnetic substance in the magnetic layer is oriented in a direction perpendicular to the surface of the base film 2. Then, the base film 2 is passed into a drying oven, where the magnetic field of the one-sided homopolar magnet array 4A arranged on the side of the base film 2 opposite to the drying means 5A causes the easy axis of magnetization of the magnetic body. In the state in which the vertical orientation is maintained, the drying means 5A completely dries the above-mentioned undried magnetic recording magnetic layer 1.

FIG. 2 schematically shows a device configuration according to a second embodiment of the present invention. In this device configuration, the drying means 5A in the drying furnace is arranged on the magnetic recording magnetic layer 1 side,
The magnet 4B as one-side homopolar magnet array means is arranged on the side of the base film 2 as the base substrate.
This is the same as the illustrated embodiment. However, in the embodiment of FIG. 2, the polarity of the one-sided magnet 4B is opposite to that of the magnet 3B arranged on the base film 2 side of the opposite-polarity facing magnet means.

FIG. 3 schematically shows a device configuration according to a third embodiment of the present invention. In this device configuration, the drying means 5B in the drying oven is arranged on the base film 2 side,
The magnet 4C as the one-side homopolar magnet array means is arranged on the magnetic recording magnetic layer 1 side, and the polarities of these magnets are the same as those of the magnet 3A arranged on the magnetic recording magnetic layer 1 side of the opposite pole opposing magnet means. It is considered to be polar.

FIG. 4 schematically shows a device configuration according to a fourth embodiment of the present invention. In this device configuration, the drying means 5B in the drying furnace is arranged on the base film 2 side,
The magnet 4D as the one-side homopolar magnet array means is arranged on the magnetic recording magnetic layer 1 side, and the polarities of these magnets are opposite to those of the magnet 3A arranged on the magnetic recording magnetic layer 1 side of the opposite pole opposing magnet means. It is said to have the polarity of.

The operation of the apparatus of FIGS. 2, 3 and 4 is basically similar to that of the apparatus of FIG. 1, and will not be described in detail again.

Finally, a specific example in which a perpendicular magnetic recording medium is actually manufactured by the manufacturing apparatus of the present invention will be described.

Paint composition Hexagonal plate barium ferrite (prototype): 40% PKHH (Union Carbide): 6% Nipporan 2304 (Nippon Polyurethane): 6% Ethyl Cellosolve: 4% MIBK: 20% MEK: 24% Orientation magnet: Barium Ferrite permanent magnet Orientation magnetic field: Between opposite magnets of opposite poles 4,000Oe One side magnet (10mm upper part) 600Oe Magnet length: Different poles opposite magnets 15mm One side magnet 1000mm After passing through the center between opposite poles opposite magnets, the base film surface The magnet placed only on the side passed 10 mm above the magnet. Drying was done with hot air and completed while passing over the magnet.

Coating conditions Model: Nozzle applicator Speed: 5m / min Width: 150mm Coating thickness: 2μm Base film: Polyethylene terephthalate 75μ As described above, a coating film having anisotropy in the extremely vertical direction could be obtained.

Although barium ferrite permanent magnets were used as the orientation magnets in the examples, it goes without saying that permanent magnets or electromagnets made of other materials may be used.

Further, the distance between the different pole facing magnet and the magnet arranged on one side and the distance between the magnets arranged on one side may be zero,
It is not absolutely necessary, and if the disorder of the orientation is within a permissible range, there is no problem even if it has an appropriate interval. It may be set experimentally on a case-by-case basis together with the magnetic field strength of the magnet.

According to the configuration of the apparatus for manufacturing a perpendicular magnetic recording medium of the present invention,
It is possible to achieve strong and efficient vertical alignment without imposing restrictions on other conditions such as coating composition and drying conditions for forming the magnetic recording magnetic layer on the base substrate.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a device configuration according to a first embodiment of the present invention, FIG. 2 is a schematic diagram showing a device configuration according to a second embodiment of the present invention, and FIG. FIG. 4 is a schematic diagram showing a device configuration according to a third embodiment of the invention, and FIG. 4 is a schematic diagram showing a device configuration according to the fourth embodiment of the present invention. 1 ... Magnetic recording magnetic layer, 2 ... Base film, 3A, 3B ... Different pole facing magnets, 4A, 4B, 4C, 4D ... One-sided magnet, 5A, 5B ... Drying means.

Claims (5)

[Claims] 1. A device for manufacturing a perpendicular magnetic recording medium having a magnetic recording magnetic layer coated on the surface of a base substrate, a means for coating the magnetic recording magnetic layer on the surface of the base substrate, and the coating means. When the magnetic recording magnetic layer is undried, in order to orient the easy axis of magnetization of the magnetic material in the magnetic recording magnetic layer in a direction perpendicular to the surface of the base substrate, The opposite pole opposing magnet means arranged so as to face the back surface of the base substrate so as to sandwich them, and the coated magnetic recording magnetic layer passing through the opposite pole opposing magnet means are the magnetic recording magnetic layer and the magnetic recording magnetic layer. A drying means for drying from one side of the base substrate, and the magnetic recording magnetic layer disposed only on the other side of the magnetic recording magnetic layer and the base substrate by the drying means. For imparting a magnetic field of such a strength that the orientation in the direction perpendicular to the easy axis of magnetization of the magnetic material in the magnetic recording magnetic layer by the different pole facing magnet means can be maintained as it is without being disturbed while being dried. A one-sided homopolar magnet array means is provided. 2. The drying means is arranged on the magnetic recording magnetic layer side, and the one-side homopolar magnet array means has the same polarity as the magnets arranged on the base substrate side of the different pole facing magnet means. The manufacturing apparatus according to claim (1), which is composed of the magnet array. 3. The drying means is arranged on the side of the magnetic recording magnetic layer, and the one-side homopolar magnet array means has a polarity different from that of the magnets arranged on the side of the base substrate of the opposite-pole opposing magnet means. The manufacturing apparatus according to claim (1), which is composed of the magnet array. 4. The drying means is arranged on the side of the base substrate, and the one-sided homopolar magnet array means has the same polarity as the magnets arranged on the side of the magnetic recording magnetic layer of the opposite-polarity opposed magnet means. The manufacturing apparatus according to claim (1), which is composed of the magnet array. 5. The drying means is arranged on the side of the base substrate, and the one-sided homopolar magnet array means has a polarity different from that of the magnets arranged on the side of the magnetic recording magnetic layer of the opposite-polarity opposed magnet means. The manufacturing apparatus according to claim (1), which is composed of the magnet array.