JPS58169335A - Manufacture of vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To form a vertically magnetizable film having a smooth surface on a nonmagnetic substrate with a magnetic coating materal, by using a rotating magnetic field in the surface of a coated film to vertically orient magnetic particles in the film without magnetizing the film. CONSTITUTION:A coating liq. 1 contg. magnetic particles of Co- and Ti- substituted Ba ferrite or the like is coated on a substrate 3 such as a polymer film, and before drying the liq., an AC magnetic field H1 from a pair of coils 7, 8 and an AC magnetic field H2 from a pair of coils 9, 10 are applied at an angle theta (which is preferably close to 90 deg.) in the surface of the coated film 4 and at a time phase angle phi (which is desirably 90 deg.) between the fields H1, H2 to allow a rotating magnetic field to act. Thus, the magnetic coated film 4 is made free from nuevenness which is caused when a vertical magnetic field is applied to the film 4, a superior vertical magnetic recording medium having a smooth surface is obtd.

Description

[Detailed Description of the Invention] [Technical Field to which the Invention Pertains] The present invention relates to a method for manufacturing a magnetic recording medium, and in particular to a method for more effectively performing magnetic field orientation treatment without impairing the surface smoothness of a coating film. It is.

[Prior art and its problems]

In the production of magnetic storage media, it is common to apply magnetic coating to a support such as a non-magnetic film, followed by a magnetic field orientation treatment. That is, the magnetic particles are dispersed in a solvent together with a binder, and then coated on a support such as a polyester film, which is then passed through a magnetic field while it is still wet, so that the IA* particles in the coating are aligned in the direction of the magnetic field. By orienting it, the ability to record the direction of the reef air arrangement body is improved.

Conventionally, this orientation process has been carried out in one line in a direction parallel to the surface of the recording medium, and information has been recorded by changing Ka in this direction. However, when high-density recording is performed, the self-demagnetizing field increases, rounding occurs, the magnetization vector rotates, residual magnetization decreases, and a magnetic field is seen in the high-density recording. Therefore, recently, a method has been proposed in which information is recorded by magnetizing in a direction perpendicular to the magnetic arrangement surface K11l. In this method, the conversion is direct to the medium surface, resulting in high-density recording, and the self-demagnetizing field is reduced.
Suitable for high school students.

By direct magnetization method, as shown in Figure A#I1, the top of the substrate (3) [4iL9] is magnetized in the direction perpendicular to the medium surface, and the recording medium is magnetized in the direction perpendicular to the medium surface. It is necessary that the direction is perpendicular to the surface of the medium. Therefore, the magnetic field orientation of the magnetic coating must also be carried out in a direction perpendicular to the surface of the body.

Then, the magnetic paint (1) was applied to a 1 m long paint film (4) using a koji cloth cloth (2). It was found that when 6 ml of oriented J'fk was applied to the film, the smoothness of the coated film surface was severely deteriorated. If the alignment is done parallel to the plane, will it leak?
11 Due to the magnetic field in the perpendicular direction, the coating film is magnetized, and magnetic poles of the same sign as the coating film INK are rounded, and the static energy increases and becomes unstable, causing unevenness on the surface.
This is what is described as stabilizing. l! Therefore, it is found that it is extremely difficult to obtain a recording medium with a smooth surface by performing direct alignment tin processing using such a method of applying a magnetic field.

[Purpose of departure]

The present invention was developed as a result of various studies to solve these difficulties, and it is possible to solve this problem by applying a positive magnetic field that rotates within the coating plane perpendicular to the orientation direction to the wet coating film.
The present invention provides a method for vertically aligning magnetic particles without impairing the smoothness of the coating surface.

[Summary of the invention]

In other words, in this case, as shown in Figure 2, an orienting magnetic field for undried m II (4) is applied to the coating surface.
Instead of using a direct magnetic field, it is possible to use a rotating magnetic field within the surface of the coating film by orienting the magnetic particles in the coating perpendicularly without magnetizing the magnetic particles.

In this case, the magnetic field 0@ is less than or equal to the magnetic field Hc required for reversing the magnetization of the magnetic particles. As a method of applying the orienting magnetic field, for example, the same method [17, 8] AC magnetic fields H1 and 9.
The alternating current magnetic field H3 generated by 10 coil pairs is superimposed within the coating surface at an angle #, and further) ihH! A temporal phase angle ψ is given between. 0.9 should be close to K 90@, but it doesn't necessarily have to be 90 degrees.
It is preferable that the amplitudes of , and H are approximately the same, but they do not necessarily have to be equal. ``[Embodiment] Next, an embodiment according to the present invention will be described.

Example, A magnetic paint having the following composition was prepared.

To 1! 1 particle, Ba phe2ite CoT2 substituted product 1
00 parts (weight) (gp-62emlp, He-1,0O
00@, particle size -0,1,am) Vinyl chloride vinyl acetate copolymer (VAGH) 15 parts Polyurethane (N-3
022) 15 parts methyl isobutyl ketone
100 copies) Luen
100 Partita Hexanone 100
Part of this paint is applied to polyethylene terephthalate film (8
) Coated on (4) L% While still undried, the bacteria were passed through a rotating magnetic field for orientation shown in Figure 2. The frequency of the alternating current magnetic field used was 100 Hz, 90' in the above e'#-1, H
The strengths of l and H were set to be equal. After the above orientation treatment, a magnetic tape was prepared by drying the coated film (4) a and then calendering it. Magnetic measurements and surface roughness measurements were performed on this tape, and the vertical squareness ratio 1 surface roughness obtained by demagnetizing field correction was determined by the orientation magnetic field H
Kojikane plotted against (-Ht -Ht) is the third
As shown in this figure, this orientation method allows for direct meat processing without increasing the roughness of the coating surface.

Comparative example above lI! As a comparative example for the paper, the same paint was used in the first
The results of orientation performed by a perpendicular magnetic field as shown in 11 are shown in 411. In this case, the membrane surface Kfi is 1.
As a result of magnetization in the perpendicular direction, a magnetic pole is generated on the film surface, and approximately 4 KOa or more is required as an orientation magnetic field to round off the demagnetizing field, and when such an orientation magnetic field is used,
It can be seen that the surface roughness increases and significant surface roughness remains after calendering, making it undesirable as a recording medium.

(Effect of Ji Ming) Note that the orientation method according to the present invention is not limited to the case where the above-mentioned B Hatake ferrite substitute is used as the magnetic particles, but also y-F@, O.

It is also effective when using Co adherends and Cry snow, especially when using Co metal mold powder.
．． 8, a surface roughness of 0.1 μm was obtained.

In this way, vertical orientation can be obtained by applying a rotating magnetic field of a magnitude that does not cause magnetization reversal of the magnetic particles to the coating film.As the rotational angular velocity of the magnetic field increases, the magnetic particles in the wet coating film follows this and becomes unable to rotate. Energy of magnetic particles in rotating magnetic field H (per unit 11To)
It is considered that the time average of the direction showing the minimum value of sCooφ can be explained by the fact that it is in the direction of #-90'' in the magnetic field strength range where magnetization reversal does not occur.

As described above, according to the method of the present invention, it is possible to obtain a perfectly orthogonally oriented cloudy recording medium without deteriorating the surface smoothness, and the method has great practicality.

[Brief explanation of drawings]

) Figure 1 is an explanatory diagram of orientation treatment by the conventional method, Figure 2
The figure is an explanatory diagram of oriented electrical conduction according to the method of the present invention, connection 31Il
1 is a diagram showing the orientation* and surface roughness of a recording medium according to the present invention when the degree of orientation of the recording medium is 0 and the surface roughness is 0. FIG. 1......A-type III family 3...4 Base film 4...Magnetic amount expansion 7, 8.9.10......-Generation of rotating magnetic field Coyle's agent Patent attorney Noriyuki Chika (and 1 other person) Kenyu H(De)*r, gg Figure 4, '<2 62? Cylinder 41KIt)l)l))

Claims (1)

[Claims] <1> Rotate in a plane perpendicular to the orientation direction of the magnetic particles (2
The Ja magnetic field is within the coating surface, and the orientation direction of the magnetic particles is