JPH01185835A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To easily and effectively achieve the vertical orientating processing of a coating medium without enhancing the roughness of the surface by impressing orientating magnetic field on magnetic layer formed on a web but not yet dried to orient the magnetic particles in the direction perpendicular to the surface of the web. CONSTITUTION:Co-Ti substituted Ba ferrite powder and binder resin are included in a coating applied on a polyethylene terephthalate film, to produce the web 3. The web 3 is made pass through between plural ring-shaped magnets 6, then dried, and after calendaring, a magnetic tape is produced. Even if the drying is achieved after the orientation processing, no ruggedness occurs on the surface during the drying. By adjusting the pole interval by the same pole counter magnets, the strength of the magnetic field can be adjusted.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) Kiba Town relates to a method for manufacturing magnetic recording media, and in particular to a method for manufacturing perpendicular magnetic recording media suitable for high-density recording. be.

(Prior art) In recent years, there has been a desire for higher recording densities in magnetic recording media, and perpendicular magnetic recording media are capable of significantly higher recording density than the limits of conventional longitudinal magnetic recording media. Therefore,
Research is actively underway. In a perpendicular magnetic recording medium, the magnetic particles must be oriented so that the direction perpendicular to the magnetic coating surface is the direction of easy magnetization. Magnetic field orientation is often used to orient magnetic particles in a coating film, and to produce perpendicular magnetic recording media, a magnetic field is applied to an undried magnetic coating film in a direction perpendicular to the coating surface. A commonly used method is to orient the particles in this direction. but,
When this method is used, the coating film is magnetized in the direction perpendicular to the surface along with the orientation of the particles, and a magnetic pole is generated on the coating film surface. Therefore, the magnetic particles in the coating film oriented by this method are A diamagnetic field from the magnetic poles on the surface of the film acts, and if the coating passes through the orientation magnetic field in an undried state, the vertical orientation of the particles will be lost again due to the action of the diamagnetic field.For this reason, this method In this case, it is necessary to dry the vertically oriented coating film while passing through a magnetic field to fix the vertically oriented state.
The orientation magnet needs to be long in the wear running direction.

Furthermore, since the state in which magnetic poles are formed on the surface of an undried, flat coating film is unstable, the coating film surface oriented by this method tends to lose its flatness and become uneven on the surface.

As described above, since the vertical alignment of coating particles using a vertical magnetic field has the above-mentioned problems, an alternative vertical alignment method has been desired. As a vertical alignment method to meet this demand,
A method of applying a rotating magnetic field in an in-plane direction has been proposed.

However, with the method of applying a rotating magnetic field, as the scale of the manufacturing equipment increases, a large power source is required to generate the rotating magnetic field, and mechanical vibration and VL noise become significant, making it difficult to apply in practice. It has been desired to develop an alternative vertical alignment method.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the problems of the conventional vertical alignment method as described above. An improved vertical coating that does not cause unevenness on the coating surface even when drying, does not require a large orienting magnetic field, does not require an exceptionally large power supply, and does not generate mechanical vibration or noise. An object of the present invention is to provide a method for manufacturing a magnetic recording medium using an orientation method.

[Structure of the Invention] (Means for Solving the Problems) The method for manufacturing a magnetic recording medium of the present invention includes applying an orienting magnetic field to an undried magnetic layer coated on a web to disperse magnetic particles in the magnetic layer. In the method of producing a perpendicular magnetic recording medium by aligning the medium in a direction perpendicular to the surface of the wear, a plurality of static magnetic fields are arranged in the in-plane direction with different directions of the magnetic fields as the alignment magnetic field. It is characterized by its use.

Examples of the wear used in the present invention include films made of film-forming synthetic resins such as polyamide resins and polyester resins, and non-magnetic supports such as aluminum substrates. It can be applied to any type 5 media.

In the method for manufacturing a magnetic tape of the present invention, for example, a magnetic paint is prepared by mixing magnetic powder, a binder, and an additive with a solvent, and this magnetic paint is applied onto the non-magnetic substrate described above, and then the orientation described below is applied. A magnetic layer is formed by processing, drying, and the like.

The mixing ratio of magnetic powder and binder in the present invention is 5 to 200 parts by weight of binder to 100 parts by weight of magnetic powder! ! ! The amount used is preferably 6 to 50 parts by weight.

In addition, the magnetic powder used in the present invention includes various magnetic powders suitable for high-density recording that are flat and have an axis of easy magnetization perpendicular to the flat surface, specifically hexagonal ferromagnetic powder. Examples include metal powder and hexagonal ferrite powder. Among these, hexagonal ferrite powder is particularly suitable for use in the present invention.

The hexagonal ferromagnetic metal powder is C01C.

-Cr5Co-Hn, Hn-AJ! Fine powder of a metal that forms a hexagonal crystal by itself can be used.

As hexagonal ferrite powder, in particular - Formula 2〇-n (Fe, 03) (wherein 8 represents any one element selected from the group of Ba, Sr, Pb, Ca, and n is Represents the number 5 to 6, and part of Fc is Ti, Co, In, In, H
It may be substituted with a transition metal such as n, Cu, Ge, Nb, or Sn. ) Hexagonal ferrites are suitable.

Such hexagonal ferrite fine powder is a regular hexagonal plate-shaped single crystal whose axis of easy magnetization is perpendicular to the plate surface.
(Refer to Japanese Patent Publication No. 17fl 1982-155022 R).

Note that, if necessary, acicular and granular ferromagnetic metal powders, ferromagnetic ferrite powders, etc. can also be used together.

In addition, if necessary, add 10°ff1 of magnetic powder to the magnetic paint.
r! Per 1 part, 10 parts by weight or less of a known dispersant, 10 parts by weight or less of a lubricant, 20 parts by weight or less of a hardening agent, 10 parts by weight or less of an abrasive, 1 part by weight or less of an antistatic agent, etc. may be added. .

In the present invention, after the magnetic coating r1 containing such magnetic particles is applied onto the web, the web is sequentially passed through magnetic fields in different in-plane directions while the coating film is not yet dry.

If the strength of the magnetic field is too small, the orientation effect will be insufficient, and if the strength of the magnetic field is too large, a vertically aligned medium will not be obtained. The maximum degree of perpendicular orientation can be obtained by selecting a magnetic field approximately equal to the coercive force of the magnetic powder.

The in-plane magnetic field used in the present invention is shown in Figure 1 (
The magnetic field of the permanent magnets 1 with the same poles facing each other is shown in l, and the magnetic field <b
), an example is a static magnetic field generated by passing a direct current through an air-core coil 2.

FIGS. 2 to 4 illustrate a method of arranging a plurality of static magnetic fields in the in-plane direction with different directions of the magnetic fields, when a plurality of permanent magnets are arranged with the same polarity facing each other.

FIG. 2 shows an example used when the width of the web 3 is relatively narrow, and FIG. 2 shows a plurality of pairs of rod-shaped permanent magnets 4 with the same poles facing each other along the traveling direction of the web 3. An example is shown in which the directions are alternately changed and arranged at an angle. In addition, FIGS. 3 and 4 are examples used when the width of the web 3 is wide, and include a plurality of rod-shaped permanent magnets with the same poles facing each other.
This is an example in which the pairs of ring-shaped magnets 6 are oriented in a lattice so that each permanent magnet 5 is inclined in the traveling direction of the sea urchin 3. This shows the layout.

(Function) In A3 of the present invention, by passing a plurality of static magnetic fields arranged in the in-plane direction with different magnetic field directions one after another through an undried magnetic coating film, the magnetic particles in the coating film are is vertically oriented. The reason for this is not necessarily clear, but it is thought to be due to the following.

In other words, when the wearer passes through a plurality of such magnetic fields one after another, the magnetic coating film is subjected to in-plane magnetic fields that change one after another. If the magnitude of this magnetic field is such that it does not cause magnetization reversal, the magnetization of the particles will not be able to follow the direction of the magnetic field, which changes one after another, and the torque that the magnetic particles receive from these magnetic fields will change over time. As a result, the torque is vertically distributed, resulting in a vertically oriented medium. In this case, the directions of magnetization accompanying the vertical orientation of the magnetic particles are completely equal in the upward and downward directions, and are equally distributed, so no surface magnetization occurs even if the magnetic particles are vertically aligned. Since there is no surface magnetization, even if the undried coating film is subjected to an alignment magnetic field, the vertical alignment will not collapse rapidly, and even if it dries after the alignment treatment, the surface of the coating film will remain No unevenness occurs. Note that the strength of the magnetic field can be adjusted by adjusting the pole spacing between the same-polarity opposing magnets.

(Example) Examples of the present invention will be described below.

In addition, hereinafter "r parts" indicates parts by weight.

Example Co-Ti substituted Ba ferrite powder (average particle size 0.06
μm, Hc6000e, specific surface area 26/a) and a binder resin was applied onto the polyethylene terephthalate film using a reverse roll to a thickness of approximately 3 μm, and a plurality of rings as shown in FIG. 4 were formed. It was passed through a ring-shaped magnet (diameter 20III11 ring-shaped magnets arranged in 20 rows between 600 mm in the web running direction) at a running speed of 60 m/min, then dried, calendered and slit to form a magnetic arc. I finished F1. The strength of the magnetic field of this magnetic tape and the squareness ratio of the magnetization curves in the tape longitudinal direction, width direction, and IHe+ direction Rh, R//
and RTC width direction> is shown in FIG. Fifth
From the results shown in the figure, it can be seen that the orientation of the magnetic tape is not due to drying in the magnetic field, but due to drying after leaving the magnetic field.Also, the surface roughness of the Arp changes gradually before calendering. The surface roughness was also good at 0.08 μm, and no increase in surface roughness due to orientation was observed.

[Effects of the Invention] As is clear from one or more embodiments, according to the present invention, it is possible to easily and effectively vertically align a coating medium without increasing surface roughness. Recognize.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing homopolar opposing magnets for generating an in-plane orientation field 11, FIGS. 2 to 4 are diagrams showing specific examples of the apparatus for generating an orientation magnetic field according to the present invention, and FIG. FIG. 3 is a diagram showing the relationship between the strength of a magnetic field and the squareness ratio of a magnetic tape that is bent. 1...Permanent magnet 2...Air-core coil 3...Web 4.5...Permanent magnet 6・・・・・・・・・Ring type magnet

Claims (1)

[Claims] (1) A method of manufacturing a perpendicular magnetic recording medium by applying an alignment magnetic field to an undried magnetic layer coated on a web to orient the magnetic particles in the magnetic layer in a direction perpendicular to the surface of the web. A method of manufacturing a magnetic recording medium, characterized in that a plurality of static magnetic fields arranged in an in-plane direction with different magnetic field directions are used as the orienting magnetic field.