JPH0489625A - Production of perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the magnetic characteristics in a perpendicular direction by injecting a magnetic coating material fluidized in a laminar state from the perpendicular direction to the main plane of a nonmagnetic base impressed with magnetic fields in a perpendicular direction to a nozzle, thereby forming an undried coating layer in a coating stage. CONSTITUTION:A magnetic coating material (a) flowing in a nozzle body 20b is in the laminar state and is injected in this state nearly perpendicularly to a PET film 11 and, therefore, the major axes of the acicular magnetic materials are oriented nearly in the fluid direction and the undried coating layer 11a is formed while the magnetic materials are held nearly perpendicularly upright on the PET film. The magnetic fields generated from permanent magnets 16 to 18 are passed through an iron plate 19 and are thereby leveled off. These magnetic fields act on the coating layer 11a and the undried coating layer 11a is leveled off while the mechanical orienting state of the acicular magnetic materials is maintained. The perpendicular orientation of the magnetic material particles is enhanced in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a coated magnetic recording medium using a perpendicular magnetic recording method.

[Conventional technology]

In recent years, there has been a desire to develop high-density magnetic recording media that are excellent in recording and reproducing at short wavelengths. From this point of view, the conventionally commonly used recording method is to magnetize a magnetic recording medium having a magnetic layer with magnetic particles oriented in the longitudinal direction of the magnetic tape parallel to the surface of the magnetic layer using a ring head. Since there is a theoretical limit to increasing the packing density of magnetic particles in the magnetic layer, it is disadvantageous for use in high-density recording.

Therefore, as a high-density magnetic recording method, perpendicular magnetic recording method, in other words, a method of performing recording using a magnetic recording medium in which the axis of easy magnetization is oriented perpendicularly to the acicular magnetic material in the magnetic layer, is attracting attention. Perpendicular magnetic recording media are being actively researched. This perpendicular magnetic recording method not only allows the magnetic layer to be filled with acicular magnetic particles at a high density, but also has little influence from demagnetizing fields, so it is possible to use an SPT head instead of a ring head, and in principle It has also been confirmed that it has excellent recording and reproducing characteristics at short wavelengths and is suitable for high-density recording.

This perpendicular magnetic recording medium is made by forming a thin film of ferromagnetic metal such as a Co-Cr alloy on a base film such as a polyethylene terephthalate film (PBT film) by sputtering or vapor deposition, and using it as a recording layer. Recording media are being researched.

However, the metal thin film recording layer formed by these methods not only has problems with running durability and corrosion resistance when rubbed by a magnetic head when used as a magnetic recording medium, but also has problems with running durability and corrosion resistance when rubbed by a magnetic head when used as a magnetic recording medium. There is also a problem in terms of production efficiency.

Therefore, a coated perpendicular magnetic recording system that can be produced by a so-called coating method has fewer of these problems, has excellent flexibility in the magnetic layer, is easy to operate, and can make use of years of research into magnetic recording media. Creating a medium is being studied. This coated magnetic recording medium is made of, for example, hexagonal barium ferrite (BaFe+
20+9) A magnetic paint made by dispersing powder or acicular magnetic powder in an organic binder, etc. is applied to the base film, and before the applied layer dries, a magnetic field is applied in the perpendicular direction of the applied layer to form an axis of easy magnetization. A method of vertically aligning the layers is being considered.

Among these, a magnetic recording medium using hexagonal plate-shaped barium ferrite powder as a magnetic material has a low saturation magnetic flux density (Bs), so there is a risk of insufficient output in the low frequency range.

On the other hand, when producing a coating-type perpendicular magnetic recording medium using acicular magnetic powder, which produces a coercive force Hc due to shape anisotropy, as a magnetic material, there is a problem that the surface of the magnetic layer becomes rough. In this regard, if it is a type of magnetic tape that records by magnetizing magnetic particles parallel to the magnetic layer, such as a magnetic tape that has a magnetic layer in which magnetic particles are oriented in the longitudinal direction, as shown in Figure 3 (a). As shown in the figure, the easy magnetization axes, that is, the long axes of the magnetic substances 3, 3, etc. are oriented in the longitudinal direction of the magnetic layer 2 on the PUT film 1, so the magnets with the same polarity are made to face each other, and the space between them is undried. When the magnetic particles are passed through the PET film on which the coating layer is formed, the magnetic particles are arranged parallel to the undried coating layer, and there is little problem that the surface of the coating layer becomes rough.

However, in the case of coated perpendicular magnetic recording media, the third
As shown in Figure (b), it is necessary to form a coating layer 4 with the long axis of the acicular magnetic material 3. As such, AC vertical alignment processing method, DC alignment processing method, etc. are adopted. Specifically, a well-known method is to apply a magnetic field perpendicularly to the undried coating layer by applying a magnetic field to the undried coating layer, for example, through a PET film formed thereon, between opposing magnets of different polarities.

[Problem to be solved by the invention]

However, in order to obtain a magnetic layer in which the long axis of an acicular magnetic material such as 1-Fe2O3 is efficiently oriented perpendicularly to increase the degree of perpendicular orientation, it is necessary to Since a sufficiently larger magnetic field is applied perpendicularly to the wet coating layer, the strength and direction of the magnetic field between the opposing magnets is not the same between the edges and the center of the magnets. The orientation is disturbed by the demagnetizing field, and the surface layer of the coating layer rises in the direction of the applied magnetic field due to magnetic aggregation, which not only results in a low degree of perpendicular alignment but also creates unevenness on the surface of the coating layer, resulting in a rough surface. However, there is a problem in that so-called surface deterioration occurs.

Regarding this problem, 8,0htubo,Y,
5atoh T, Masuko, T, Watanabe,
IEEE Trans, MAG-23+ 3149 (1
987) and Yuji Sato, Akio Otsubo, Hikoyoshi Momoi, Toshio Kobayashi, 13th Japanese Society of Applied Magnetics Academic Lecture Summary 22A4 (1
987).

When a magnetic layer consisting of a coating layer with surface deterioration as described above is used, for example, as a magnetic recording tape, the distance between the magnetic head and the tape will vary, resulting in so-called spacing loss, resulting in a decrease in playback output. may invite

This is a big problem, especially for magnetic recording media that record images in a short wavelength range.

Therefore, in order to solve these problems, a LIPS alignment device as shown in FIG. 4 has been proposed (for example, Y,
5atoh, ^, 0htubo, T, Masuko, M
, kurematsu [iEE Trans, MAG
-23, 3149 (1988)). That is, a plurality of sets of magnets each having a pair of N and S poles facing each other are provided, and the N and S poles are arranged in reverse for every set of magnets, so that the surface layer of the magnetic coating layer is perpendicularly magnetically oriented, and the deep layer is magnetically oriented longitudinally. Magnetic tapes having layers have been proposed. Note that 5 is a coating device, and 6 is a base film on which an undried coating layer is formed after the coating device.

However, even this method cannot be said to have solved the above problems, and improvements have been desired.

As described above, if a magnetic field larger than the coercive force Hc is applied in order to orient the long axis of the acicular magnetic particles perpendicularly to the coated layer, the surface of the resulting magnetic layer becomes rough. However, if the strength of the orientation magnetic field is weakened to prevent the surface of the magnetic layer from becoming rough, the degree of perpendicular orientation of the magnetic particles to the coated layer will be insufficient, and the resulting magnetic layer will have good magnetization characteristics in the perpendicular direction. (There is a problem that there is no such thing, and the emergence of a perpendicular magnetic recording medium that satisfies both of these problems has been desired.

An object of the present invention is to obtain a magnetic recording medium having a magnetic layer with a high degree of perpendicular orientation of magnetic particles and a smooth surface in a method of manufacturing a coated perpendicular magnetic recording medium.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention includes a coating process of forming an undried coated layer of magnetic paint on a non-magnetic support, and a non-magnetic support having the undried coated layer obtained through this coating process. In a method for producing a perpendicular magnetic recording medium having a vertical alignment treatment step of orienting the axis of easy magnetization of the magnetic particles perpendicularly to the main surface of the coating layer by passing between opposing magnetic poles of different polarities, the above coating step Magnetic recording is characterized in that the above-mentioned magnetic coating material flowing in a laminar flow state is injected into a nozzle in a direction perpendicular to the main surface of the above-mentioned non-magnetic support to which a perpendicular magnetic field is applied to form an undried coating layer. A method for producing a medium is provided.

In this case, it is also preferable that the undried coating layer obtained through the above coating step is a undried coating layer obtained through surface smoothing treatment to make the surface flat fk.

[Effect]

When paint flows through a nozzle in a laminar flow state, that is, at a constant speed, the acicular magnetic material contained in this paint creates abrasion stress between the inner wall of the nozzle and adjacent magnetic particles, and the magnetic material flows in the direction of paint flow. This produces a mechanical orientation in which the long axes of the particles are uniformly aligned. When a paint containing acicular magnetic particles oriented by this flow is sprayed perpendicularly to the surface of a non-magnetic support,
A coating layer is formed in which the acicular magnetic particles stick vertically to the surface. When this coating layer is still undried and uncured, the acicular magnetic particles rotate in search of a more stable state. Therefore, by utilizing the fact that these acicular magnetic particles have an axis of easy magnetization in the long axis direction, we can prevent these rotations by applying external magnetic energy perpendicular to the non-magnetic support, which will cause its vertical orientation. can be maintained. If the vertical alignment treatment is performed in this state, the vertical alignment of the magnetic particles can be further increased, and if the coated layer is dried in this state, the vertical alignment of the magnetic particles will be increased and a magnetic layer with less disturbance can be obtained. be able to.

〔Example〕

Next, the present invention will be explained in detail.

Example 1 As shown in FIG. 1, a PET film 11 is guided via guide rollers 12, 13 and 14 to a coating device I5.

In addition, in 14a, the magnetic paint applied in the next step is PET.
The container serves as a receptacle for excess paint that does not adhere to the film and falls off.

The coating device 15 coats Fe-5m-Co magnetized with a surface magnetic flux of 3000 G on the back side of the PUT film 11.
An iron plate 19 coated with a Teflon sheet is attached to the top surface of the S pole of each of the permanent magnets 16, 17, and 18, and a plurality of nozzle devices 20 are arranged on the surface side of the PET film 11 in the width direction thereof. It is.

This nozzle device 20 has a plurality of nozzle bodies 20b, 20b, etc. each having an inner diameter of 0.5 to 1.5 fi and a length of 40 to 70 mm at the tip of the magnetic paint introduction part 20a. Magnetic paint introduction pipe 20c on the rear side,
20d, and a gas introduction pipe 20e is provided at the end thereof, and the amount of each gas introduced can be adjusted by a cock in the former and a valve in the latter.

Note that the shape of the nozzle body 20b is such that the smaller the diameter and the longer the length, the more mechanical force (sliding stress) acts on the acicular magnetic particles in the paint, making it easier for these particles to align in one direction. However, if the diameter is too small or too long, the paint will clog and it will not be possible to apply it uniformly, so the diameter will vary somewhat depending on the viscosity and dispersion state of the paint, but the size of the diameter is as described above <0.
The length is preferably about 5 to 1.5 m and the length is about 40 to 10 m. It is preferable that the paint is sufficiently filtered before being sprayed from the nozzle body.

In this state, a magnetic paint having the composition shown below is introduced into each of the magnetic paint introduction portions 20a of the nozzle device 20, and about 0.5 kg/cm of nitrogen gas is introduced into each of the gas introduction pipes 20e.
The nozzle bodies 20b, 2 are fed under a pressure of ni.
While flowing the magnetic paint in a laminar flow state at 0b...
The liquid is sprayed almost vertically onto the PUT film 11. In addition to nitrogen gas, oxygen gas (02), carbon dioxide gas (CO2), etc. can also be used, and the pressure of these gases is preferably adjusted within a pressure range of 0.5 to tKg/c%.

Acicular alloy powder 100 parts by weight Vinyl chloride resin 8 parts by weight Urethane resin
12 parts by weight polyisocyanate
6 parts by weight myristic acid 3 parts by weight n-butyl stearate 1ffi parts toluene 130 parts by weight Methyl ethyl ketone 130 parts by weight Abrasive (granular α-
7!2Q,) 12 parts by weight The above acicular alloy powder has a long axis of 0.2 μm and a short axis of 0.03 μm.
, specific surface area (BET value) 52 vl/g, coercive force Hc9
000e was used.

The running speed of the non-magnetic support was 10 m/min, the thickness of the coating layer was 4.0 μm in terms of dry film, and the thickness of the PUT film was 14 μm.

In this way, as shown in Fig. 2, the nozzle body 2
The magnetic paint a flowing in 0b is in a laminar flow state,
In this state, the PET film 11 is sprayed almost perpendicularly (PE
Since the T film travels, it is sprayed at a slightly acute angle to the front.
As a result, the long axis of the acicular magnetic material is substantially oriented in the direction of flow, and an undried coating layer 11a is formed on the PUT film while standing substantially vertically. At this time, the magnetic field generated from the permanent magnets 16 to 18 is leveled through the iron plate 19 and acts on the coated pillar, and while the mechanical orientation state of the acicular magnetic material is maintained, the undried coated layer 11a is will be leveled. Incidentally, the paint not attached to the PET film flows down, and the above-mentioned receiver is accommodated in the container 14a.

Next, the PU on which the undried coating layer 11a was formed
The T film is guided to a surface smoothing device 21. This surface smoothing device 21 applies a surface smoothing film 22 whose tension can be changed by supporting both ends of the undried coated film 22.
ii A guide roller 23 is provided on the 11a side and facing the back side of the PET film 11, and a surface condition film 21 such as a PET film is brought into contact with the surface of the undried coating layer 11a to coat the surface. smooth. In addition, 2
2a is a container that receives the paint scraped off the surface smooth film 22.

Next, processing is performed by a vertical alignment device 23.

This vertical alignment device 23 has permanent magnets 24a, 24a, 24a of the same size on the back side of the PUT film 11.
are placed in close contact with each other with their S poles facing upward, and permanent magnets 24b, 24b, .
A Teflon seam 1-coated iron plate 25 is attached to the upper surfaces of all of 4a and 24b. Further, on the side of the undried coating layer 11a, permanent magnets 26a, 26a having the same dimensions as the permanent magnets 24a, 24a, 24a,
26a with the N pole on the lower side, and the permanent magnets 24a and 2
Similarly, the permanent magnets 26b, 26b, and 26b are brought into close contact with each other with the N poles facing down through the same space 27 as the space between the permanent magnets 26a and 4b, and a space 28 corresponding to the width of the permanent magnet 26a is provided to connect the permanent magnet 26c. , 26c , 26c, 2
6c and the permanent magnets 22b and 22b, respectively.
Provided opposite to...

At this time, the magnetic field strength of the magnet depends on the coercive force of the acicular magnetic material used. For example, if Co- and FezO3 powder is used, the coercive force is 30 to 8000 e, and if metal powder is used, the coercive force is 1200 e.
About 2 to 3 times each of ~15,000e is preferred.

As this magnet, it is also preferable to use a Fe-Nd-8 magnet in addition to a Fe-Sm-Co permanent magnet. Note that magnets made of the same material may be used for the permanent magnets 16 to 18 as well.

In this vertical alignment device 23, an alignment magnetic field of 3000 G is formed between the S and N poles, and warm air at 60° C. and 80° C. is blown into the space 27 and space 28, respectively. In this state, the PET film 11 having the undried coated layer 11a coated with magnetic paint by the coating device 15, subjected to mechanical alignment treatment, and further surface smoothed is brought into contact with the iron plate 19 with its back surface, while the above-mentioned upper side is Lead between permanent magnets. In this way, the degree of vertical orientation of the acicular magnetic particles in the undried coating layer 11a is further improved, and the coating layer is gradually dried from the surface layer to the deep part.
The viscosity increases and the baingoo resin partially hardens, and the degree of freedom of movement of the magnetic particles is taken away and the orientation state is fixed.

The PET film having the coating layer subjected to this vertical alignment treatment is led to a drying chamber 29, where it is sufficiently dried.
Curing is promoted and the magnetic tape is wound up to obtain an original magnetic tape.

The above original magnetic tape was polished to a mirror finish and cut to create a magnetic tape having a magnetic layer with a dry coating thickness of 4 μm.To examine the degree of orientation in the vertical direction, the coercive force and squareness were compared (both in the vertical direction). The magnetic properties were measured using a sample vibrating magnetometer (manufactured by Riken Denshi Co., Ltd.).

These results are shown in the table. The larger these values, the higher the degree of vertical orientation. In addition, the surface roughness (surface roughness, ie, the root mean square value of irregularities) of the magnetic layer of the magnetic tape was examined using a surface roughness needle.

The results are shown in the table. The smaller the value, the better the surface smoothness. Note that the surface roughness of commercially available VTR tape is 0.
．． O15 to 0.025 μm.

Comparative Example ■ A magnetic tape was produced in the same manner as in Example 1, except that instead of applying the magnetic paint using the coating device 15, the magnetic paint was applied using the conventional direct gravure method. The results measured in the same manner as above are shown in the table.

Note that the squareness ratio is a value corrected by demagnetizing field.

From the above results, it can be seen that the magnetic tape of Example 1 has superior magnetic properties and lower surface roughness than that of Comparative Example 1.

In the above, spraying magnetic paint from the vertical direction means
The iron plate 19 may be made of a ferromagnetic metal material, including the case where the iron plate 19 is diagonal. Further, the magnets 26a, 26b, and 26c may be attached and used using perforated plates (wood, metal, ceramic, plastic, etc.). Further, infrared rays may be used in combination with hot air. Further, it is preferable to use the PET film of the surface smoothing device while appropriately changing it depending on the viscosity of the paint, coating speed, etc. At this time, the back surface may be elastically pressed with a magnet.

In addition, in the above, as the needle-like alloy powder, Fe-N
i,, alloys such as Fe-Ni-Co can be used, but
Instead of this acicular alloy powder, oxides such as -Fe203, Co-containing YFe203, CrO2, iron nitride, iron carbide, etc. can also be used, and the present invention is not limited to these.

In addition, the above-mentioned PET film may be used, but other materials may also be used, and non-magnetic supports may include those coated with an undercoat layer on the surface and a backcoat layer on the back surface.

〔Effect of the invention〕

According to the present invention, a magnetic paint in a laminar flow state is applied vertically to the main surface of a non-magnetic support, and the vertical alignment treatment is performed after, for example, the acicular magnetic material is vertically erected. As a result, compared to the conventional vertical alignment method, in which the magnetic particles in the undried coated layer are aligned in the longitudinal direction of a non-magnetic support, and then vertical alignment treatment is performed using magnetic energy, the degree of vertical alignment is lower. It is possible to provide a magnetic recording medium having a magnetic layer with high surface smoothness and excellent surface smoothness.

In other words, in the conventional method, the magnetic particles have difficulty standing vertically in the undried coated layer, or after being vertically oriented, they may move to the side, disturb the arrangement, or cause magnetic aggregation. In the obtained magnetic layer, the degree of vertical orientation and surface smoothness of the magnetic particles are reduced, but according to the method of the present invention, the magnetic particles are oriented vertically from the beginning in the undried coating layer. To obtain a magnetic recording medium having a magnetic layer having a high degree of perpendicular orientation and excellent surface smoothness by further applying perpendicular orientation treatment, since it is held on a non-magnetic support, and there is less unnecessary movement of particles. I can do it.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram of a part of the apparatus used in the manufacturing method of one embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the part, and Fig. 3 (a) is parallel to the main surface of the coating layer. Figure 4 is a schematic diagram of a conventional vertical orientation device. It is. In the figure, 11 is a PET film as a base film, 1
5 is a coating device, 20 is a nozzle device, 20b is a nozzle body, 16 to 18 are permanent magnets, 21 is a surface smoothing device, 2
3 is a vertical alignment processing device. July 26, 1990

Claims (2)

[Claims] (1) A coating process in which an undried coating layer of magnetic paint is formed on a non-magnetic support, and a coating process in which a non-magnetic support with an undried coating layer obtained through this coating process is formed between magnetic poles of different polarities facing each other. In a method for manufacturing a perpendicular magnetic recording medium, the method includes a perpendicular alignment treatment step in which the axis of easy magnetization of the magnetic particles is orientated perpendicularly to the main surface of the coated layer by passing the magnetic particles through the coating layer, and the coating step includes applying a magnetic field in the perpendicular direction. 1. A method for manufacturing a magnetic recording medium, which comprises spraying the above-mentioned magnetic paint flowing in a laminar flow into a nozzle from a direction perpendicular to the main surface of a non-magnetic support to form an undried coating layer. (2) Manufacturing the magnetic recording medium according to claim 1, wherein the undried coating layer obtained through the coating step is an undried coating layer obtained through a surface smoothing treatment to smooth the surface thereof. Law.