JPS6342031A - Method and apparatus for production of perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To enable powerful and efficient perpendicular orientation by completing the drying of an undried magnetic recording layer coated while the orientation of a magnetic material is maintained after said material is oriented in the direction perpendicular to the axis of easy magnetization thereof. CONSTITUTION:The magnetic recording layer 1 is coated on the surface of a base film 2 by a coating means disposed in front of different pole opposed magnets 3A and 3B. The base film 2 on which the magnetic recording layer is coated is then passed between the magnets 3A and 3B and the axis of easy magnetization of the magnetic material in the magnetic recording layer is oriented in the direction perpendicular to the surface of the base film 2 while the coated magnetic recording layer 1 is undried. The base film 2 is then passed into a drying furnace where the orientation in the direction perpendicular to the axis of easy magnetization of the magnetic material is maintained by the magnetic field by the same pole magnet train 4A on one side disposed on the film 2 side opposite from the drying means 5A and in this state the coated and undried magnetic recording layer 1 is thoroughly dried by a drying means 5A.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for manufacturing a coated perpendicular magnetic recording medium.

Conventional technology In recent years, coated perpendicular magnetic recording media using hexagonal barium ferrite plates have become more suitable for high-density recording than conventional media using iron oxide (in-plane horizontal recording). Various uses are being considered. In addition, as a perpendicular magnetic recording medium, a method of using acicular iron oxide and orienting the acicular magnetic material perpendicularly has also been attempted. in any case,
It is necessary to form a coating film with strong magnetic anisotropy in the perpendicular direction by aligning a material with high magnetic anisotropy perpendicularly to the coating surface.

Regarding the orientation method, there are already some patent documents such as JP-A-57-127931 and JP-A-57-2.
No. 05827, Japanese Unexamined Patent Publication No. 57-212626,
JP-A-58-12130, JP-A-58-1213
No. 5 and JP-A-58-12136. In other words, it can be roughly divided into those that utilize mechanical stress or magnetic force, and those that utilize magnetic force are:
It can be classified into methods that apply a direct current or alternating current magnetic field. In addition, the viscosity of the coating film is an important factor for orientation, and various devised methods are described in patent documents, for example,
No. 12136, Japanese Patent Application Laid-open No. 58-203631,
JP-A-58-203632, JP-A-58-203
It is described in Publication No. 633.

Problems to be Solved by the Invention In the conventional method using mechanical stress as described in JP-A No. 58-12137, the conditions for obtaining high orientation are very narrow, and the range of application is limited. Limited.

In other words, the magnetic material is limited to plate-shaped magnetic materials such as hexagonal plate-shaped barium ferrite that have an axis of easy magnetization perpendicular to the plane, and cannot be applied when acicular magnetic powder is oriented perpendicularly. . Also, the requirement for high shear stress makes the optimum conditions for paint viscosity and equipment very narrow.

In the conventional method using a DC magnetic field, a magnetic field is applied to the coating film when it is not yet dry, and unless the coating film is dried in an orientation magnetic field, high orientation cannot be achieved. However, it is extremely difficult to sufficiently control drying, which affects the surface properties and structure of a coating film, within narrow spaces between magnets. Another disadvantage is that it is necessary to design a coating that is not significantly affected by drying conditions, which imposes restrictions on the selection of binder resins and solvents.

In addition, the conventional method of using an alternating magnetic field is effective only when used as an auxiliary means or when the paint composition is very easy to orient, and has the disadvantage that the orienting force is inherently weak. .

An object of the present invention is to provide a method and apparatus for manufacturing a perpendicular magnetic recording medium that can solve the problems of the conventional techniques as described above.

Means for Solving the Problems According to the present invention, in a method for manufacturing a perpendicular magnetic recording medium having a magnetic recording layer coated on the surface of a base substrate, the magnetic recording layer is coated on the surface of the base substrate. a step of coating, and a step of orienting the axis of easy magnetization of the magnetic material in the applied magnetic recording magnetic layer in a direction perpendicular to the surface of the base substrate when the applied magnetic recording magnetic layer is not dried. and a step of orienting the easy axis of magnetization of the magnetic substance in a perpendicular direction and then completing drying of the applied undried magnetic recording magnetic layer while maintaining that orientation.

Further, according to the present invention, in an apparatus for manufacturing a perpendicular magnetic recording medium having a magnetic recording layer coated on a surface of a base substrate, means for coating the magnetic recording layer on the surface of the base substrate; When the applied magnetic recording magnetic layer is not dried, the magnetic recording magnetic layer is used 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. and a different polarity opposing magnet means disposed opposite to and sandwiching the front surface of the base substrate and the back surface of the base substrate, and the applied magnetic recording magnetic layer passing through the different polarity opposing magnet means is magnetically recorded. a drying means for drying the magnetic layer and the base substrate from one side; and a drying means disposed on the other side of the magnetic recording layer and the base substrate, the magnetic recording layer being dried by the drying means. The method is characterized by comprising an orientation maintaining means for applying a magnetic field for maintaining the orientation in the perpendicular direction of the axis of easy magnetization of the magnetic substance in the magnetic recording magnetic layer by means of opposite polarity opposing magnets. do.

Embodiments Next, the present invention will be described in more detail with reference to embodiments of the present invention based on the accompanying drawings.

First, to explain the present invention in principle, according to the present invention,
First, by passing an undried coating film between opposing magnets with different polarities, the axis of easy magnetization of the magnetic material was oriented in a direction perpendicular to the coating surface, and then oriented magnets with the same polarity were placed only in the middle. A vertically oriented coating film can be obtained by passing through several sections during which drying of the coating film is completed. That is, in the present invention, the first opposite magnets with different polarities generate a strong vertical orientation magnetic field and serve to orient the easy axis of magnetization of the magnetic material in the vertical direction. In addition, the next part where magnets of the same polarity are placed only on one side is for the purpose of maintaining the oriented state without disturbing the once oriented magnetic material, and while the coating film passes through this part, the magnetic material Dry until it does not move. Note that in this part, since the orientation magnet is present only on one side, drying can be sufficiently controlled without being subject to any restrictions, and appropriate drying and curing can be performed.

In the present invention, the following four types of arrangement of the above-mentioned orientation magnets can be considered, and each has a unique effect.

First, the position of the magnet placed only on one side can be divided into cases where it is placed on the coating film side and cases where it is placed on the opposite side (base film) side. This is because when controlling drying, there are cases where it is better to apply hot air, infrared rays, ultraviolet rays, electron beams, etc. from the coating surface, and there are cases where it is better to apply it from the opposite side. Applying from the surface of the coating is generally more efficient in drying and is often used, but applying from the opposite side can prevent the coating from forming a skin and may provide a smoother surface. In either case, the present invention can be applied as described above.

Next, it is divided into two types depending on the polarity combination of the opposite polarity facing magnets and the subsequent magnets arranged only on one side.

The first type is one in which the opposite magnet and the magnet placed on one side have the same polarity, and the second type is one in which the opposite magnet and the magnet placed on one side have opposite polarities.

According to the first type of combination, the magnetic material of the paint film to be attacked is attracted to the magnet placed on one side before drying, forming a distribution in the depth direction of the paint film. Therefore, when the magnet placed on one side is located on the coating film surface side, the magnetic body is attracted toward the coating film surface. The paint film part close to the base film surface has more resin components, which improves the paint film adhesion.
The area near the surface of the coating film is filled with magnetic material, resulting in magnetic properties suitable for high-density recording. Furthermore, durability can be greatly improved by applying a lubricant. It is very effective that the magnetic material is dense in the surface layer because it means that the surface is porous.

On the other hand, when the magnet placed on one side is located on the back side of the coating film (base film), the magnetic substance is attracted to the base film side, and the coating film surface has a large amount of resin component. this:
Well, it has a similar effect to forming a protective layer of resin, and the durability of the coating film is greatly improved.

Next, in the case of the second quartet, the magnetic body, once magnetized by the opposing magnet, receives a repulsive force from the magnet placed on one side and tries to move away. At this time, if the strength of the magnet placed on one side is large enough to sufficiently magnetize the magnetic material, the magnetization of the magnetic material will be instantly reversed, and the magnetic material will be attracted to the magnet side as in the previous case. It will be done.

In order to exert repulsive force, the magnetic field of the magnet placed on one side must be controlled to be strong enough to reverse the magnetization of the magnetic material (and to be strong enough to control the disturbance of orientation. This method When drying means (hot air, etc.) is applied from the side of the coating film to increase the density of the magnetic material on the surface of the coating film, or when drying means is applied from the back side of the coating film (base film side) to make the resin on the surface of the coating film dense. It can be applied when you are in love with someone.

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

First, FIG. 1 schematically shows an apparatus configuration according to a first embodiment of the present invention. In this apparatus configuration, a drying means 5A in a drying oven is arranged on the side of the magnetic recording magnetic layer 1. The magnet 4A as an orientation holding means is arranged on the side of the base film 2 as a base substrate, and the polarity of these magnets is the same as that of the magnet 3B arranged on the side of the base film 2 of the opposite polarity opposing magnet means. It is said that To briefly explain the operation of the device shown in Fig. 1, the opposite magnets 3
The magnetic recording magnetic layer 1 is coated on the surface of the base film 2 by a coating means (not shown) placed in front of A and 3B. Next, the base film 2 coated with these magnetic recording magnetic layers is coated with different polarity opposing magnets 3A and 3.
B, where the axis of easy magnetization of the magnetic material in the magnetic recording magnetic layer is perpendicular to the surface of the base film 2 when the applied magnetic recording magnetic layer 1 is not dried. Oriented to. Next, the base film 2 is
The magnetic material is passed through the drying oven, and the magnetic field generated by the single-sided homopolar magnet array 4Δ disposed on the side of the base film 2 opposite to the drying means 5A causes the easy axis of magnetization of the magnetic material to be oriented in the vertical direction. In this state, the drying means 5A completely dries the applied undried 6g recording magnetic layer 1 described above.

FIG. 2 schematically shows an apparatus configuration according to a second embodiment of the present invention. In this apparatus configuration, the drying means 5A in the drying oven is arranged on the side of the recording magnetic layer l. , the magnet 4B as the orientation holding means is arranged on the side of the base film 2 as the base substrate.
This is the same as the embodiment shown in the figure. However, in the embodiment of FIG. 2, the polarity of the one-sided magnet 4B is opposite to that of the magnet 3B disposed on the side of the base film 2 of the opposite polarity opposing magnet means.

FIG. 3 schematically shows an apparatus configuration according to a third embodiment of the present invention. In this apparatus configuration, the drying means 5B in the drying oven is arranged on the side of the base film 2, and the drying means 5B is arranged on the side of the base film 2. The magnet 4C as a means is the magnetic recording magnetic layer 1
The polarity of these magnets is the same as that of the magnet g3A arranged on the side of the magnetic recording layer 1 of the opposite polarity opposing magnet means.

FIG. 4 schematically shows an apparatus configuration according to a fourth embodiment of the present invention. In this apparatus configuration, a drying means 5B in a drying oven is arranged on the side of the base film 2, and The magnet 4D as a means is the magnetic recording magnetic layer 1
The polarity of these magnets is opposite to that of the magnet 3A arranged on the side of the magnetic recording layer 1 of the opposite polarity opposing magnet means.

The operations of the devices shown in FIGS. 2, 3, and 4 are basically the same as the operations of the device shown in FIG. 1, and therefore will not be described in detail again.

Finally, a specific example in which a perpendicular magnetic recording medium was actually manufactured using the manufacturing method of the present invention will be described.

Paint composition Hexagonal plate barium ferrite (prototype): 40% PKHH
(Union Carbide): 6% Nituboran 230
4 (Japan Polyurethane): 6% ethyl cellosolve=
4% MIBK:
20%MEK:
2496 Orientation conditions Orienting magnet: Barium ferrite permanent magnet Orienting magnetic field: Between opposite magnets with different polarities 4.00008 One side magnet (10m upper part) 6000e Magnet length: Opposing magnets with different polarities 15 mm One side magnet 1000 mm Coating film is between opposite magnets with different polarities After passing through the center of the base film, it passed through the top 10 corners of a magnet placed only on the side of the base film. Drying was done with hot air and completed during passage over the magnet.

Whirlpool condition type Nozzle applicator speed,
5m/min width:
150n+m coating thickness:
2μm base film: polyethylene terephthalate 75μ Magnetic properties ★: Squareness ratio in the vertical direction shows the value corrected for the demagnetizing field.

As described above, a coating film having extremely vertical anisotropy could be obtained.

Note that although barium ferrite permanent magnets were used as orientation magnets in the embodiments, it goes without saying that other types of permanent magnets or electromagnets may also be used.

In addition, the distance between the opposite polarity opposing magnets and the magnet placed on one side, and the distance between the magnets placed on one side may be zero, but
This does not necessarily mean that there must be one or more, but as long as the disorder of orientation is within an allowable range, there is no problem in having an appropriate spacing. It may be set by experiment together with the magnetic field strength of the magnet on a case-by-case basis.

Effects of the Invention According to the method of manufacturing a perpendicular magnetic recording medium and the structure of the apparatus of the present invention, there is no restriction on coating composition, drying conditions, or other conditions for forming a magnetic recording layer on a base substrate. Moreover, efficient vertical alignment can be achieved.

[Brief explanation 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. 3 is a schematic diagram showing a device configuration according to a second embodiment of the present invention. FIG. 4 is a schematic diagram showing an apparatus configuration according to a third embodiment of the invention. FIG. 4 is a schematic diagram showing an apparatus configuration according to a fourth embodiment of the invention. ■...Magnetic recording magnetic layer, 2...Base film, 3A, 3B...Different polarity opposing magnet, 4A
, 4B, 4C, 4D... One side magnet, 5A, 5B
...Drying means. Figures 1 and 2

Claims (6)

[Claims] (1) A method for manufacturing a perpendicular magnetic recording medium having a magnetic recording magnetic layer coated on the surface of a base substrate, which includes a step of coating the magnetic recording magnetic layer on the surface of the base substrate, and a step of applying the magnetic recording layer on the surface of the base substrate, and recording the magnetic recording layer coated on the surface of the base substrate. a step of orienting 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 when the magnetic layer is undried; A manufacturing method comprising the step of completing drying of the applied undried magnetic recording magnetic layer while maintaining the orientation after orientation in the direction. (2) In an apparatus for manufacturing a perpendicular magnetic recording medium having a magnetic recording magnetic layer coated on the surface of a base substrate, means for coating the magnetic recording layer on the surface of the base substrate, and a means for coating the magnetic recording layer on the surface of the base substrate; When the magnetic layer is undried, the surface of the magnetic recording magnetic layer and the base are aligned in order to orient the axis of easy magnetization of the magnetic material in the magnetic recording magnetic layer in a direction perpendicular to the surface of the base substrate. Different polarity opposing magnet means disposed to face the back surface of the base body so as to sandwich them therebetween, and the coated magnetic recording magnetic layer passing through the different polarity opposing magnet means to the magnetic recording magnetic layer and the base substrate. a drying means for drying from one side of the magnetic recording layer and the base substrate, and a drying means disposed on the other side of the magnetic recording layer and the base substrate, and the different polarity facing the magnetic recording layer being dried by the drying means. and an orientation maintaining means for applying a magnetic field for maintaining the orientation of the easy axis of magnetization of the magnetic substance in the magnetic recording magnetic layer in the perpendicular direction by the magnet means. (3) The drying means is arranged on the side of the magnetic recording magnetic layer, and the orientation holding means is a magnet having the same polarity as the magnet arranged on the side of the base of the different polarity opposing magnet means. A manufacturing apparatus according to claim (2). (4) The drying means is arranged on the side of the magnetic recording magnetic layer, and the orientation holding means is a magnet of a different polarity from the magnet arranged on the side of the base of the different polarity opposing magnet means. A manufacturing apparatus according to claim (2). (5) The drying means is arranged on the side of the base substrate, and the orientation holding means is a magnet having the same polarity as the magnet arranged on the side of the magnetic recording layer of the different polarity opposing magnet means. A manufacturing apparatus according to claim (2). (6) The drying means is arranged on the side of the base substrate, and the orientation holding means is a magnet of a different polarity from the magnet arranged on the side of the magnetic recording magnetic layer of the different polarity opposing magnet means. A manufacturing apparatus according to claim (2).