JPH0489626A - Production of perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the perpendicular magnetic recording medium having a magnetic layer which is increased in the degree of perpendicular orientation by executing a curving orientation treatment to curve an undried coating layer by bringing a curved body into contact with the rear surface of a nonmagnetic base in combination with a perpendicular orientation treatment stage. CONSTITUTION:A PET film 13 is brought into contact with the curved body of a permanent magnet 12 and is thereby curved. The magnetic fields are simultaneously imparted to this film. A shearing stress is thereby generated between the undried coating layer 15 and the PET film 13 and the acicular magnetic material particles 15a, 15a... risen by the 1st perpendicular orienting treatment are further risen. The magnetic fields between the permanent magnets 12 and 12' further accelerate the rising. A dried 19 (not shown) is provided in a curved orienting treatment device 11 on the front side of the progressing direction of the PET film 13 to blow hot wind. The magnetic recording medium having the magnetic layer which is high in the degree of the perpendicular orientation of the magnetic material particles is formed 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 the magnetic material in the magnetic layer, it is disadvantageous for use in high-density recording.

Therefore, as a high-density type magnetic recording medium, a so-called perpendicular magnetic recording method, that is, a perpendicular magnetic recording medium having a magnetic layer in which the axis of easy magnetization of magnetic particles is oriented perpendicularly, is used. BACKGROUND ART Systems that perform recording by magnetization have attracted attention, and perpendicular magnetic recording media have been actively researched.

This perpendicular magnetic recording method not only allows magnetic particles to be packed in the magnetic layer at a high density, but also has little influence from demagnetizing fields, so it is possible to use SPT-nodes instead of ring heads, 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.

In this perpendicular magnetic recording medium, a thin film of a ferromagnetic metal such as a Go-Cr alloy is formed on a base film such as a polyethylene terephthalate film (PUT film) by sputtering or vapor deposition to form a recording layer. methods 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 magnet when used as a magnetic recording medium, but also has problems with the magnetic recording medium. There are also problems 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+) Apply a magnetic paint in which powder or acicular iron oxide powder is dispersed in an organic binder to a base film, and before the paint film dries, apply a magnetic field in the perpendicular direction of the coated layer to change the axis of easy magnetization. A method of orienting the coating layer in the vertical direction 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, since the axis of easy magnetization, that is, the long axis, of the magnetic material 3.3 is oriented in the longitudinal direction of the magnetic N2 on the PUT film l, the magnets with the same polarity are made to face each other, and the area between them is coated without drying. When the magnetic particles are passed through the layered PET film, 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 efficiently make the long axis of an acicular magnetic material such as E -Fe2O perpendicular to obtain a magnetic layer with enhanced vertical 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 causes unevenness on the surface of the coating layer, resulting in a rough surface. There is a problem that so-called surface deterioration occurs.

In addition, when the applied magnetic field is removed, the vertically oriented magnetic particles try to return to their original state and rotate or fall, a so-called "return" phenomenon. There is also the problem of lowering the degree of

Regarding these issues, A, 0htubo, Y
.

5atoh, T., Masuko, T., Watanab
e, IEEE Trans, MAG-233149 (1
987) and Yuji Sato, Akio Otsubo, and Hikoyoshi Momoi.

Toshio Kobayashi, 13th Japanese Society of Applied Magnetics, Academic Lecture Summary 22
A4 (1987).

When a magnetic layer consisting of a coating layer with so-called 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,
5atOtl+ A, 0htubo, T, Masuk
o, M, Kurematsu.

IEEE Trans, MAG-23, 3149 (19
88)). 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. In addition, 5
6 is a coating device, and 6 is a base film having an undried coating layer after this coating device.

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

An object of the present invention is to obtain a perpendicular magnetic recording medium having a magnetic layer with a particularly high degree of perpendicular orientation 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 provides a method for manufacturing a magnetic recording medium that includes a vertical alignment treatment step in which a wet coated layer of magnetic paint is formed on a non-magnetic support. The present invention provides a method for manufacturing a perpendicular magnetic recording medium, characterized in that a curving alignment process of curving the undried coating layer by bringing a curving body into contact with the back surface is used in conjunction with the vertical alignment process.

At this time, the curved body has a magnetic pole, a vertical alignment process is used in combination with the curved alignment process, a magnetic pole with a different polarity from the magnetic pole of the curved body is provided on the wet coated layer side, and these magnetic poles are placed opposite each other to apply a magnetic field. The curved alignment process is performed during the vertical alignment process, and the vertical alignment process and the curved alignment process are horizontal alignment processes that orient the magnetic particles in the undried coated layer along the length of this coated layer. It is also preferable to do this after performing

[Effect]

When the undried raw cloth layer is bent from the non-magnetic support side using a bending body, abrasion stress is generated between the non-magnetic support and the undried coating layer, and this causes the magnetic particles in the undried coating layer to stand up. It becomes easier. If a perpendicular magnetic field is applied to the coating layer when the magnetic particles stand up in this manner, vertical alignment is further promoted.

〔Example〕

Next, the present invention will be explained in detail.

Example 1 Reference numeral 11 in FIG.
2.12゛ are installed facing each other. These permanent magnets 12
．． On either side of the 12° angle, the former faces the north pole and the latter faces the south pole, and the tips of each of these opposing magnets are shaped into a spherical curved body with a radius of curvature R of 20 to 50 tm. To create a magnetic recording medium using a PET film 13, as shown in FIG.
4, the following magnetic paint is applied to form an undried coating layer corresponding to the undried coating layer 15 shown in FIG. Note that 14a is a magnetic paint supply section.

Acicular alloy powder Vinyl chloride resin Urethane resin Polyisocyanate n-butyl myristate toluene Methyl ethyl ketone Abrasive (granular α-A 1.205) 100 parts by weight 8 parts by weight 12 parts by weight 6 parts by weight 3 parts by weight 1 part by weight Part 130 parts by weight 130 parts by weight 12 parts by weight The above-mentioned acicular alloy powder has a long axis of 0.2 μm, a short axis of 0.03 μl, and a specific surface area (B[!T value) of 52 rd/
g, coercive force Hc9000e was used.

Further, the coating conditions are as follows.

Coater: Direct gravure method (doctor blade method using roll with diagonal line 45 degrees, depth 100 μm) Coating layer thickness: 5 μm (dry coating) Coating speed: 10 m/m1n PET film thickness: 10 μm Next, apply PET film. A surface smoothing device 1 in which a surface smoothing body 16a such as a film is supported at both ends so that its tension can be adjusted, and is brought into contact with the surface of the undried coating layer.
6 to make the surface of this coating layer smooth.

Thereafter, the magnetic particles of the undried coated layer subjected to the smoothing treatment are oriented in the longitudinal direction of the coated layer by passing through a magnetic field in which the N poles of the permanent magnets 17a and 17a are opposed to each other.

Thereafter, processing is performed by the first vertical alignment processing device 18.

That is, this first vertical alignment processing device 18 has permanent magnets 18a, 18a arranged on the upper side with the S pole facing downward, and permanent magnets 18b, 18b arranged on the lower side, with the N pole facing upward, and the above-mentioned S The magnets are placed opposite each other to form a magnetic field between the upper and lower magnets. The PET film having the undried coating layer subjected to the above treatment is carried into the magnetic field of the first vertical alignment processing device 18 and is run to perform the first vertical alignment treatment.

Then, processing is performed by the above-mentioned curved alignment processing device 11.

That is, as shown in FIG. 1, the PET film 13 is brought into contact with the curved body of the permanent magnet 12 and curved, and at the same time a magnetic field is applied.

By doing this, the undried coating layer 15 and PET
Abrasion stress is generated between the films 13, and the acicular magnetic particles 15a 51 stand up due to the first vertical alignment process.
5a ... stands up even more. At this time, the permanent magnet 12
．． A magnetic field between 12° facilitates this.

At this time, in the curve orientation treatment 11, a dryer 19 is provided on the leading end side of the PET film 13 in the traveling direction to blow hot air. This accelerates the drying of the undried coating layer and fixes the oriented particles with the binder of the coating layer so that their arrangement is not disturbed.

After this, a second vertical alignment processing device 20 consisting of permanent magnets 20a and 20b with their respective S and N poles facing each other applies a further vertical magnetic field to the magnetic particles to cause their "return". At the same time, the magnetic particles in the deep layer are vertically aligned.

The permanent magnets used above are as follows.

Permanent magnet: Fe-3m-Co permanent magnet Intensity of alignment magnetic field: 3000 G Distance between upper magnetic pole and coating layer: 2R In this way, the vertical alignment treatment is performed and drying progresses to a certain extent, and the magnetism, especially in the surface layer, is reduced. A PET film having a coating layer in which the orientation state of body particles is fixed can be heated at 60°C, 80°C,
Drying room 21 with temperature set in steps of 100℃ and 120℃
The coating layer is sufficiently dried and the binder resin is cured. As a result, the arrangement state of the magnetic particles in the deep layer is reliably fixed.

Thereafter, the magnetic tape material 22 is obtained by winding it up.

Mirror finish the above magnetic tape material (85℃, 300K)
A magnetic tape having a magnetic layer with a thickness of 3.5 μm was prepared by cutting the tape into a width of 8 cm (calender treatment under conditions of g/cm). This magnetic tape was placed in a constant temperature room at 60°C for 20 hours for stabilization treatment (complete hardening treatment), and the magnetic properties of coercive force and squareness ratio (both in the vertical direction) were measured to examine the degree of orientation in the vertical direction. It was measured with 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.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1, except that the permanent magnet 12 was a metal roll with no magnetic pole of the same shape and the permanent magnet 12° was not used. The results of the measurements 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 tapes of the examples have better magnetic properties than those of the comparative examples.

In addition to Fe-Sm-Co permanent magnets, Fe-Nd-
It is also preferred to use 8 magnets; other magnets may also be used.

In addition, an undercoat layer,
A material provided with a hack coat layer may also be used. In addition,
It is preferable to apply the magnetic paint after removing static electricity using a static eliminator.

Further, as the acicular alloy powder, Fe-Ni, Fe-
Alloys such as NiCo can be used, but r-Fe2O2, Co-containing 1-Fe2O3, C
Oxides such as rO2, iron nitride, iron carbide, etc. can also be used.

〔Effect of the invention〕

According to the present invention, a curved alignment process is used in combination with a vertical alignment process, and in addition to the magnetic field alignment process, a mechanical alignment process is performed by applying abrasion stress to the magnetic particles in the undried coated layer. A magnetic recording medium having a magnetic layer with a high degree of perpendicular orientation of body particles can be provided.

In this way, it is possible to provide a coated magnetic recording medium having perpendicular magnetic properties suitable for perpendicular magnetic recording systems in which the recording wavelength extends to an extremely short wavelength range.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram of a part of the apparatus used in one embodiment of the present invention, Fig. 2 is an explanatory diagram of the whole thereof, and Fig. 3 (A) shows a magnetic body parallel to the main surface of the coating layer. FIG. 4 is an explanatory diagram when the particles are oriented. FIG. 4B is an explanatory diagram when the magnetic particles are oriented perpendicularly to the main surface of the coating layer. FIG. In the figure, 11 is a curved alignment processing device, 12 is a permanent magnet as a curved body, 12', 18a'+18b, 20
'a and 20'b are permanent magnets, 13 is a PH7 film as a base film, and 15 is an undried coating layer. July 26, 1990

Claims (5)

[Claims] (1) The object to be treated, on which a wet coated layer of magnetic paint is formed on a non-magnetic support, is passed between opposing magnetic poles of different polarities so that the axis of easy magnetization of the magnetic particles is aligned perpendicular to the main surface of the coated layer. In a method for producing a magnetic recording medium that includes a vertical alignment treatment step, the vertical alignment treatment step includes a curving alignment treatment in which the undried coating layer is curved by bringing a curved body into contact with the back surface of the non-magnetic support. A method for manufacturing a perpendicular magnetic recording medium characterized by: (2) The method for manufacturing a perpendicular magnetic recording medium according to claim 1, wherein the curved body has a magnetic pole, and a vertical alignment process is used in combination with the curved alignment process. (3) A vertical alignment process according to claim 2, characterized in that a magnetic pole having a different polarity from the magnetic pole of the curved body is provided on the side of the undried coating layer, and the vertical alignment process is performed by making these magnetic poles face each other and forming a magnetic field. A method for manufacturing magnetic recording media. (4) The method for manufacturing a perpendicular magnetic recording medium according to any one of claims 1 to 3, characterized in that the curved alignment treatment is performed in the middle of the vertical alignment treatment step. (5) The vertical alignment treatment and the curved alignment treatment are performed after performing a horizontal alignment treatment for orienting the magnetic particles of the undried coating layer in the longitudinal direction of the coating layer. A method for manufacturing a perpendicular magnetic recording medium.