JPS62243129A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the orientation of magnetic powder particles and to obtain a recording medium having an excellent electromagnetic conversion characteristic by forming N-N repulsive magnetic fields and S-S repulsive magnetic fields having the magnetic field intensity higher than the coercive force of magnetic powder and successively executing specific stages. CONSTITUTION:A substrate 2 is introduced into and run in the magnetic fields juxtaposed alternately with at least >=1 sets of the N-N repulsive magnetic fields 6 and S-S repulsive magnetic fields 7 having the magnetic field intensity higher than the coercive force of the magnetic powder 4 incorporated into a magnetic coating compd. The magnetic fields are alternately acted positively and negatively to the magnetic powder particles 4 incorporated into the magnetic coating compd. on the traveling substrate while the magnetic coating compd. is gradually cured. The inversion of the magnetic fields which invert from positive to negative or from negative to positive and act on the magnetic powder particles 4 as the substrate 2 travels is ended before the magnetic powder particles 4 start rotation by the effect of the magnetic field inversion. Only the direction of the magnetization of the magnetic powder particles 4 is thus inverted and the axis of easy magnetization of the magnetic powder particles 4 is satisfactorily oriented in the traveling direction of the substrate, by which the electrical characteristics of the magnetic recording medium are improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a magnetic recording medium, and more particularly, to a method for manufacturing a magnetic recording medium with good orientation of magnetic powder and excellent electrical properties. .

[Conventional technology]

In general, magnetic recording media such as magnetic tapes are coated with a reverse roll, gravure roll, etc. [1110] While a base film 2 is fed out from a feed roll 1 and run at a constant speed, as shown in FIG. is applied, and while the coating film 4 is in an undried state, a magnetic field orientation device W is applied.
ll to orient the axis of easy magnetization of the magnetic powder particles in the magnetic coating 4 in a certain direction, and then conduct to the dryer 5 to completely dry and harden, and then wind it up on the winding roll 8. It is being created.

In the magnetic field orientation device 11, conduction is generally used to orient the magnetic particles so that the axis of easy magnetization is along the traveling direction (longitudinal direction) a of the base film 2, and therefore N-N
The base film 2 with the wet coating III 4 is introduced between the opposing magnets using a facing magnet or an S-8 facing magnet, or the base film 2 with the wet coating III 4 is introduced into a solenoid through which a direct current is passed. The method of introduction and release is adopted.

However, in this method, once a magnetic field is applied to orient the magnetic powder particles in the running direction, the magnetic coating film is removed from the magnetic field by the time it is dried, which causes problems such as mechanical vibration and elastic relaxation of the binder resin. Due to target disturbance, the arrangement of the magnetic powder particles, which were once oriented in the running direction of the base film, is disturbed, and furthermore, the orientation of the magnetic powder particles is also disturbed by the external force generated due to the contraction of the binder resin during the drying process. , it is not possible to orient the magnetic powder sufficiently well.

Therefore, it is necessary to prevent such disturbance of the orientation of the magnetic powder particles, and one easy way to do this is to apply a magnetic field after applying the magnetic paint on the base film until it dries and solidifies. This can be achieved by arranging long solenoids or a large number of appropriately sized solenoids in series and applying a magnetic field after coating until dry and solidified, or by applying N-N opposed magnets (S) as shown in Figure 4. -3 facing magnets 6, 6) are arranged in parallel inside and outside the dry ta5, and the undried magnetic coating film 4 is formed in the parallel magnetic field generated by the facing magnets 6.6. The magnetic powder particles in the magnetic coating film 4 are oriented in the running direction of the base film 2 by running the film 2 and using the parallel magnetic field generated by the opposing magnet 6.6 until the undried magnetic coating film 4 is dried. This can easily be considered.

[Problem that the invention seeks to solve]

However, the method of arranging a long solenoid or a large number of appropriately sized solenoids in series and applying a magnetic field after coating until it dries and solidifies is ideal because it can linearly generate a magnetic field in the same direction. In reality, it is necessary to evaporate the organic solvent in the paint during this time, and this drying often requires a large amount of hot air to be pumped in. Furthermore, a large magnetic field of several thousand oersteds is required, so the coil As the size increases, the electric capacity also increases, requiring a huge amount of cost, which is impractical.

In addition, as shown in FIG. 4, a large number of N-N opposing magnets 6.6 are arranged in parallel inside and outside the dryer 5, and these opposing magnets 6.6 keep the undried magnetic coating film 4 in parallel until it is dried. In the orientation method of applying a magnetic field to orient the magnetic powder particles in the magnetic coating film 4 in the running direction of the base film 2, as shown in the distribution diagram of the magnetic field strength in FIG. While the magnetic coating film 4 sequentially travels from one N-N opposing magnet 6.6 to the next N-N opposing magnet 6.6, the direction of the magnetic field gradually changes between these N-N opposing magnets arranged in parallel. When the once oriented magnetic powder particles enter a magnetic field in the opposite direction, a magnetic force in the opposite direction gradually acts on them, causing rotation of the magnetic powder particles and disrupting their orientation. cannot be oriented.

[Means for solving problems]

This invention was made as a result of urgent research to overcome this problem. Magnetic paint is applied onto a substrate, and then magnetic field strength higher than the coercive force of the magnetic powder contained in the magnetic paint is applied. At least one set of an N-N repulsive magnetic field and an S-S repulsive magnetic field are alternately introduced in parallel, and the magnetic paint is gradually hardened, while the magnetic paint on the traveling substrate is gradually hardened. A positive and negative magnetic field is applied alternately to the magnetic powder particles contained in the substrate, and as the base moves, the magnetic powder particles can reverse the reversal of the magnetic field acting on the magnetic powder particles from positive to negative or from negative to positive. By terminating rotation before it starts due to the action of reversal, only the direction of magnetization of the magnetic powder particles is reversed without rotating the magnetic powder particles, and the axis of easy magnetization of the magnetic powder particles is aligned with the running direction of the substrate. The magnetic recording medium is well oriented and the electrical characteristics of the magnetic recording medium are sufficiently improved.

This invention will be explained below with reference to the drawings.

FIG. 1 shows an outline of a method for manufacturing a magnetic recording medium according to the present invention. In this method, a base film 2 fed out from a feed roll l is run at a constant speed while a coating head 3 coats the magnetic paint. While the magnetic coating film 4 coated and formed on the base film 2 is in an undried state, it is guided between N and N opposing magnets 6 and 6 disposed immediately before the dryer 5. Then, it is introduced into the dryer 5, and
A large number of S-S opposing magnets 7.7, N-
While drying the magnetic coating film 4 by guiding it between N opposing magnets 6.6, the axis of easy magnetization of the magnetic powder particles in the magnetic coating film 4 is oriented along the running direction a of the base film 2, and completely dried.
After curing, the dried Ul 5 is extracted and wound onto a winding roll 8. 9 goes to coating 3
This is a filter that filters out impurities in the magnetic paint that is applied.

However, just before dryer 5 and dry! A base film 2 in which a magnetic coating film 4 is provided between a large number of N-N opposing magnets 6.6 and S-S opposing magnets 7, 7, which are alternately arranged in parallel in a5.
When the dryer 5 is introduced, the magnetic powder particles in the magnetic coating film 4 are first oriented in the running direction of the base film 2 by the N-N repulsive magnetic field of the N-N opposing magnet 6.6 immediately before the dryer 5.

Thereafter, as the base film 2 travels, the magnetic field is reversed from the N-N opposing magnet 6.6 to the next S-S opposing magnet 7.7, as shown in the magnetic field strength distribution diagram in FIG. This reversal of the magnetic field occurs instantaneously when the base film 2 reaches the next N-N opposing magnet 6.6 from the S-S opposing magnets 7, 7. , 6 and the S-S opposing magnet 7.7 is instantaneously repeated.

Therefore, between the next N-N opposing magnets 6, 6 or S-S
Until the direction of the magnetic field momentarily reverses for the first time when the particles reach between the opposing magnets 7.7, no magnetic force in the opposite direction acts on the once oriented magnetic powder particles, and the magnetic powder particles are not affected by the opposite magnetic force between the adjacent N-N opposing magnets 6.
6 and the S-S opposing magnet 7.7, the magnetic field does not gradually and continuously reverse as shown in FIG. As a result, the magnetic powder particles in the magnetic coating film 4 are not affected by a magnetic field that gradually and continuously reverses.

Therefore, the magnetic coating film 4 changes the magnetic field strength of the N-N opposing magnets 6.6 and the S-8 opposing magnets 7.7, which are arranged in large numbers alternately, between these N-N opposing magnets 6.6 or S-8 opposing magnets 6.6. -S When reaching between the opposing magnets 7 and 7, the strength is set such that the direction of the magnetic field of the magnetic powder particles in the magnetic coating film 4 can be instantaneously reversed, and the viscosity of the magnetic paint forming the magnetic coating film 4 is instantaneously reduced. The viscosity is such that when the direction of the magnetic field of the magnetic powder particles is reversed, the magnetic powder particles do not rotate due to this reversal magnetic field.
Furthermore, if the traveling speed of the magnetic coating film 4 is set to a speed that does not allow for the direction of the magnetic field of the magnetic powder particles to be instantaneously reversed and rotation of the magnetic powder particles to occur, the magnetic coating film 4 will be able to absorb these N- Between N opposing magnets 6.6 or S-S opposing magnets 7.
At the point when it reaches between 7 and 7, the magnetic field changes and becomes magnetic! ! !
Before the rotation of the magnetic powder particles in the film 4 occurs (only the magnetization within the magnetic powder particles is reversed. Therefore, the magnetic powder particles do not rotate in the magnetic coating 4, but move toward the first N-N opposing magnet. The magnetic coating film 4 is well oriented in the state oriented by 6, 6.
Only the direction of magnetization of the magnetic powder particles is reversed, and the magnetic powder particles are easily and well oriented in the running direction of the base film 2, so that the square shape is sufficiently improved and the electromagnetic conversion characteristics are sufficiently improved. .

In this way, in order to successfully repeatedly reverse only the magnetization of the magnetic powder particles without rotating the magnetic powder particles,
Numerous N-N opposing magnets 6, 6 and S-S arranged alternately
The magnetic field strength of the opposing magnets 7.7 is preferably greater than the coercive force of the magnetic powder contained in the magnetic coating 4, and the magnetic field intensity generated by the opposing magnets is greater than the coercive force of the magnetic powder contained in the magnetic coating 4. If the coercive force is smaller than the coercive force, the direction of magnetization of the magnetic powder particles cannot be instantaneously reversed.

The viscosity of the magnetic paint forming the magnetic coating film 4 is preferably 20 centiboise or more as measured by a Brookfield viscometer, and the viscosity of the magnetic coating film 4 is preferably lower than 20 centiboise. , the magnetic powder particles move very easily, and the adjacent N-N opposing magnets 6, 6
The magnetic powder particles in the magnetic coating film 4 rotate due to the reversal of the magnetic field between the magnets 7 and the ss opposing magnets 7, 7.

Furthermore, the traveling speed of the magnetic coating film 4 is preferably 1 m/min or more, and may be as fast as it is 1 m/min or more, but if the traveling speed of the magnetic coating 4 is slower than 1 m/min. In this case, the magnetic powder particles move slowly in the magnetic field generated by the opposing magnets due to slow changes in the magnetic field rather than an instantaneous reversal magnetic field, and the moving speed of the magnetic powder particles in the magnetic coating 4 is slow. Therefore, as the direction of the magnetic field changes, the magnetic powder particles themselves rotate under the influence of a reversing magnetic force, and the once oriented arrangement of the magnetic powder particles is disturbed, making it impossible to achieve good orientation of the magnetic powder particles.

Even if the N-N opposing magnets 6.6 and the S-8 opposing value stones 7, 7 arranged in parallel in this way are arranged in the dryer 5, they are oriented before drying is completed. When the magnetic field is no longer applied, the rotational force due to the reversal magnetic field acts on the magnetic powder particles in the magnetic coating film 4, so the magnetic coating film 4 on the base film 2 dries and hardens, and the magnetic powder particles It is preferable that the magnetic coating film 4 is disposed above and below the magnetic coating film 4 until the particles no longer move easily, and preferably until the magnetic coating film 4 in the dryer 5 is dried.

In addition, in the above example, the case where the magnetic coating film 4 is cured using the dryer 5 has been explained, but the invention is not limited to this. Similarly, when using a radiation-curable resin and curing the magnetic coating film 4 by irradiation with radiation,
The orientation treatment of the magnetic powder particles of the present invention can be performed while the magnetic coating film 4 is being cured by irradiation with radiation, and in this case as well, the same effects as in the above case can be obtained.

When preparing magnetic paint, the magnetic powder used is:
r-Fe203 powder, Fe3O4 powder, r-Fe203
and Fe50. intermediate iron oxide powder, Co-containing r-Fe20
3 powder, Co-containing Fe3O4 powder 1, Fe powder, metal powder mainly composed of Fe with addition of various metals, Co powder, N
Any of the powders commonly used in the past, such as i powder or alloy powders thereof, can be suitably used.

In addition, as the binder resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, cellulose resin,
Conventional binder resins such as polyurethane resins, polyester resins, and isocyanate compounds are widely used.

As the organic solvent, conventionally used organic solvents such as toluene, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, and ethyl acetate can be used alone or in combination of two or more.

Note that various commonly used additives such as dispersants, lubricants, fillers, antistatic agents, etc. may be optionally added to the magnetic coating material.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 Acicular r-Fe203 powder 80 parts by weight (coercive force 370 oersted) Vinyl chloride-vinyl acetate-vinyl 9 Alcohol copolymer polyurethane resin 9 Trifunctional low molecular weight isocyanate 2 Compound methyl isobutyl ketone 60 〃toluene
60 This composition was mixed and dispersed in a ball mill for 48 hours to prepare a magnetic paint having a viscosity of 4.0 poise (Lyon simple viscosity needle). This magnetic paint is applied onto a polyester base film 2 with a thickness of 12 μm at a coating speed of 10 m/1 lin using a coating head 3, and while it is in an undried state, inside and outside of a dryer 5 shown in FIG. It was introduced between N--N opposing magnets 6.6 and S--S opposing magnets 7.7, which were arranged at six locations, and was simultaneously dried with hot air. The sixth S-S facing magnet 7.7 is where the coating film loses its solvent luster in appearance, and is then thoroughly dried with hot air at a temperature of 95°C to eliminate residual solvent, resulting in a dry thickness of 6 μm.
A magnetic layer was formed. After that, it was cut to a specified width to make magnetic tape. The strength of the magnetic field is determined by measuring the magnetic field in the direction perpendicular to the opposing magnet on the intersection line between the center of the opposing electrodes and the end face of the magnet, that is, where the running surface of the film passes through the end face of the magnet. 150 depending on magnet spacing
I adjusted it to 0 oersted.

Comparative Example 1 In Example 1, the N-N opposing magnets 6, 6 and the S-8 opposing magnet 7 disposed inside and outside the dryer 5 shown in FIG.
．． In place of the magnetic field orientation device in which a large number of 7s are arranged alternately, a 4th
A magnetic tape was produced in the same manner as in Example 1, except that a magnetic field orientation device in which a large number of N--N opposing magnets 6.6 were arranged in parallel as shown in the figure was used.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 1, except that the N-N opposing magnets 6.6 and the S-S opposing magnets 7°7 disposed inside and outside the dryer 5 were omitted. I made it.

Regarding the magnetic tapes obtained in each example and comparative example,
Coercive force, residual magnetic flux density, maximum residual magnetic flux density, square shape, output at frequency 31511z, output at frequency 12.5KHz, maximum output level (distortion rate 3%) at frequency 3151-1z, saturation level at frequency 10Kllz were measured. . The measured values were expressed as relative values with respect to the magnetic tape obtained in Comparative Example 1 as a reference (OdB).

Table 1 below shows the results.

Table 1 [Effects of the Invention] As is clear from the above table, the magnetic tape obtained by the method of the present invention has a lower magnetic tape than the magnetic tape obtained by the conventional method.
The residual magnetic flux density and square shape are high, and the output is high. This shows that according to the method of this invention, the magnetic powder particles are well oriented and a magnetic recording medium with excellent electromagnetic conversion characteristics can be obtained. .

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an outline of the manufacturing process of the magnetic tape of the present invention, FIG. 2 is a distribution diagram of the magnetic field strength in the manufacturing process of the magnetic tape shown in FIG. 1, and FIGS. 3 and 4. 5 is an explanatory diagram showing an outline of a conventional magnetic tape manufacturing process, and FIG. 5 is a distribution diagram of magnetic field strength in the magnetic tape manufacturing process shown in FIG. 4. 2... Base film (substrate), 3... Coating head, 4... Magnetic coating film, 5... Dryer, 6...
・N-N opposing magnet, 7...S-S opposing magnet Fig. 3

Claims (1)

[Claims] 1. Apply a magnetic paint onto a substrate, and then apply at least one N-N repulsive magnetic field and an S-S repulsive magnetic field alternately, each having a magnetic field strength higher than the coercive force of the magnetic powder contained in the magnetic paint. The magnetic powder particles contained in the magnetic paint on the moving substrate are applied with alternating positive and negative magnetic fields while the magnetic paint is gradually hardened by introducing the magnetic paint into a magnetic field arranged in parallel with the substrate. The reversal of the magnetic field that is reversed from positive to negative or from negative to positive, which acts on the magnetic powder particles as a result of the reversal of the magnetic powder particles, is terminated before the magnetic powder particles start rotating due to the effect of this magnetic field reversal, and the magnetic powder particles are rotated. A method for manufacturing a magnetic recording medium, which comprises reversing only the direction of magnetization of the magnetic powder particles to orient the axis of easy magnetization of the magnetic powder particles in the running direction of the substrate.