JPH02108238A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the saturation magnetic flux density and squareness ratio of the magnetic recording medium and to increase the max. residual magnetic flux density by applying a magnetic coating material essentially consisting of magnetic powder and binder on a nonmagnetic substrate then applying an AC magnetic field to the coated surface in the direction perpendicular thereto to make magnetic field orientation in the longitudinal direction of the substrate. CONSTITUTION:The magnetic coating material 7 contg. ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, etc., and a binder, such as vinyl chloride/vinyl acetate copolymer, dissolved in an org. solvent, such as acetone, is applied on the coated surface 7a of the nonmagnetic substrate 8 consisting of polyester, polyethylene, etc. An electromagnet to orient the coating with the magnetic field is constituted of a magnetic core 4 having magnetic pole parts 1, 2 which are spaced, a coil 5 wound to a connecting part 3, and an AC power source 6 connected thereto. The previously formed slender substrate 8 is thereafter passed between the magnetic pole parts 1 and 2 to orient the magnetic powder in the coating material 7 in the longitudinal direction. Namely, the magnetic powder is oscillated by magnetic field inversions, by which the more magnetic powder is packed into the magnetic layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a magnetic recording medium, and in particular to a novel method for banking (filling) of magnetic powder before magnetic field orientation treatment of a coated magnetic recording medium. ) is related to technology.

[Summary of the invention]

When manufacturing a coated magnetic recording medium, the present invention applies an alternating magnetic field in a direction perpendicular to the coating surface of a non-magnetic support coated with magnetic paint prior to longitudinal orientation treatment. Improving the packing density of magnetic powder, saturation magnetic flux density,
Maximum residual magnetic flux density.

The aim is to improve magnetic properties such as squareness ratio.

[Conventional technology]

For example, in magnetic recording media used as recording media for audio tape recorders, video tape recorders, etc., acicular magnetic powder is longitudinally oriented horizontally (especially in the longitudinal direction of the medium) with respect to the magnetic recording layer. Many things are used.

To perform longitudinal orientation treatment, a magnetic field larger than the coercive force of the magnetic powder is applied in the longitudinal direction of the medium using a permanent magnet or an electromagnet to force the direction of the magnetic powder along the longitudinal direction of the non-magnetic support. It is done by pointing in the direction.

By the way, in a magnetic recording medium in which magnetic powder is oriented in the longitudinal direction, if an attempt is made to achieve higher recording density, a larger saturation magnetic flux density, a maximum residual magnetic flux density, and a larger squareness ratio are required.

However, when trying to meet such demands, there are limits to the conventional magnetic field alignment process alone. In particular, metal powder tends to agglomerate, and conventional magnetic field orientation treatment alone has left unsatisfactory aspects such as packing degree 4 orientation.

(The invention is not intended to solve the problem ζ) Therefore, the present invention has been proposed in view of the above-mentioned conventional situation. This paper aims to improve the f-U, saturation flux density, maximum residual 6I1 flux density, and squareness ratio, and to propose a method for manufacturing magnetic recording media that achieves a reproduction output of <1. .

[Means for Solving the Problems] C. Magnetic recording medium manufacturing method of the present invention has been proposed to achieve the above object, and includes a 6d material and a binder on a non-magnetic support. Applying an alternating current magnetic field in the direction perpendicular to the coated surface of the non-Cfi support coated with a magnetic coating mainly consisting of Cfi, and then orienting the magnetic field in the longitudinal direction of the non-Cfi support. There are 4 characteristics.

As a method of applying an alternating current perpendicularly to the coating surface of the non-magnetic support, for example, the non-magnetic support is sandwiched and magnetic plates are placed facing each other. There is a method of generating a Gl field by setting opposing magnetic poles as different poles, and reversing the direction of these magnetic fields. , a coil is wound around each magnet and the AC power source is connected to that coil (:), or the coil is wound around an integrated magnet 7.1- with the f41 poles facing each other. Examples include those in which the AC d'L power supply is not connected. Required GJ: Any configuration is sufficient as long as it can apply an alternating magnetic field in the direction of force perpendicular to the coating surface of the nonmagnetic support.

Further, it is desirable that the magnitude of the alternating YAt bsl field applied to the coating surface is lower than the coercive force of the magnetic particles dispersed in the magnetic paint. In other words, if the magnitude of the applied [fi field] is higher than the coercive force of (11), the magnetic powder will stand in the direction perpendicular to the coating surface, causing roughness on the coating surface. It is.

In addition, as a method for orienting magnetic powder in a ζd magnetic field in the longitudinal direction of a non-magnetic support, magnets are placed facing each other in a direction perpendicular to the coating surface of the non-magnetic support. One method is to apply a magnetic field with the magnetic poles being the same, and to run a non-magnetic support coated with a magnetic coating between the magnetic poles to longitudinally orient the magnetic field. Or, the magnetic field is generated by
A non-6ft support coated with magnetic paint may be run through the noid for longitudinal direction treatment. In addition, ordinary longitudinal orientation techniques can be employed.

On the other hand, as the binder constituting the magnetic paint, any binder resin that is used as a binder for ordinary coated magnetic recording media can be used.

Examples of such resins include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, and vinyl chloride-vinylidene chloride copolymer. Acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer, thermoplastic polyurethane resin, polyfluoride vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, -? Crylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral,
Examples include binder resins such as cellulose derivatives styrene-butadiene copolymer, polyester resins, phenolic resins, epoxy resins, thermosetting polyurecne resins, urea resins, melamine resins, alkyd resins, urea-formaldehyde resins, or mixtures thereof.

On the other hand, examples of the magnetic powder include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles are those whose X value is in the range of 1.33≦X≦1.50 when expressed by the general formula FeOx, that is, magnetite (y Fezes).

x=1.50), magnetite (Pe, Oa, x
= 1.33) and their solid solutions (FeOx, 1.
33<x<1.50) Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. There are two types of cobalt-containing iron oxide: 'ζ-doped type and deposited type.

The above-mentioned ferromagnetic chromium dioxide is CrO□ or Ru for the purpose of improving the coercive force thereof.

It is possible to use a material containing a small amount of Sn, Te, Sb, Fe, Ti, V, Mn, etc.

Examples of the ferromagnetic alloy powder include Fe, Co, and Ni.

Fe-Co, Fe-Ni, Fe-Co-Ni, C.

-Ni, Fe-Co-B, Fe-Co-Cr-BMn-
Bi, Mn-A1. Fe-Co-V, etc. can be used, and Ani, Si, and Ti can also be used to improve various properties.
, Cr, Mn, Cu, Zn, and other metal components may be added.

The magnetic recording medium of the present invention may be formed by dispersing the magnetic powder in the above-mentioned binder and dissolving it in a Ja-containing solvent and applying a magnetic paint to the surface of a non-magnetic support.

Above mentioned 4! ! Examples of solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, and glycol monoethyl acetate;
Glycol ethers such as glycol dimethyl ether, glycol monoethyl ether, and dioxane; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane and heptane; methylene chloride, ethylene chloride, carbon tetrachloride, and chloroform.

Examples include organic chlorine hydrocarbons such as ethylene chlorohydrin and dichlorobenzene.

In addition to the above-mentioned binder and magnetic powder, the above-mentioned magnetic paint contains dispersants, abrasives, antistatic agents, rust preventives, etc., which are usually used as additives for forming the magnetic layer of magnetic recording media. It's okay to be hit.

Further, a lubricant may be used for the purpose of imparting lubricity to the magnetic layer and improving the durability of the magnetic layer. When the above-mentioned lubricant is used, the lubricant may be added internally to the magnetic paint, or may be tump-coated onto the applied magnetic paint.

The nonmagnetic support may be any material that is normally used in this type of magnetic recording medium, such as polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, and cellulose. Examples include cellulose derivatives such as triacetate, cellulose diacetate, and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, and plastics such as polycarbonate, polyimide, polyamide, polyamideimide, and polyphenylene sulfide.

Note that in the magnetic recording medium manufactured according to the present invention, a back coat layer may be formed on the surface opposite to the surface on which the magnetic layer is formed.

[Effect]

When an alternating current magnetic field is applied perpendicularly to the coating surface of a non-magnetic support coated with a magnetic paint mainly consisting of magnetic powder and a binder, the magnetic powder vibrates as the applied magnetic field reverses. do. The vibration allows the magnetic powder to move within the magnetic coating material, so that more of the magnetic powder is backed within the magnetic layer.

Then, when the magnetic powder becomes easy to move, magnetic field orientation is applied in the longitudinal direction of the non-magnetic support, so that the degree of orientation is improved.

〔Example〕

Hereinafter, specific examples of a method for manufacturing a magnetic recording medium to which the present invention is applied will be described.

First, the AC magnetic field application device used in this example will be explained.

As shown in FIG. 1, the above-mentioned alternating current magnetic field applying device comprises a pair of magnetic pole parts (1) and (2) arranged opposite to each other, and a connecting part (1) that connects these magnetic pole parts (1) and (2). 3) A coil (5) is wound a predetermined number of times around a magnetic core (4) which has a U-shaped appearance, and the coil (5) is connected to an AC power source (
6) are connected to each other.

A pair of clouds in the magnetic core (4) above! Part j (1), (2)
A non-magnetic support (8) coated with a 6I1 paint (7) mainly composed of magnetic powder and a binder runs on the ljn, and the magnetic pole parts (1), (2) The structure is such that an alternating current magnetic field is applied in a direction perpendicular to the coating surface (7d) of the 6R paint (7) while passing through the gap.

In the sympathetic magnetic field applying device 6 configured as described above,
When the coil (5) is supplied with a current 1 in the direction shown in FIG. 2(A), the direction of the magnetic field is in the direction of arrow A in FIG. 2(8). At this time, the magnetic powder M passing between the magnetic pole parts (1) and (2) is rotated once in the direction of the arrow a in the figure by the base field. When the coil (5) is energized as shown in Figure (B), a magnetic field in direction B opposite to direction A of the magnetic field is generated. Then, the magnetic powder M is rotated in the direction of the arrow in the figure by the magnetic field. However, if the reversal speed of the alternating current magnetic field is fast, the magnetic field M will oscillate in the direction of the magnetic field as shown in Figure 3. . As a result, the magnetic powder M can move in the magnetic paint (7), and 1. - This causes more of the primary powder M to be banked into the outer layer (63').

Here, the present inventors actually produced a magnetic recording medium using the above-mentioned alternating current (B field application device).

First, magnetic powder with a coercive force of 1216 oersted (Ie) was dispersed in a binder, etc., and a magnetic paint was applied for 1'l on a non-magnetic support.The magnetic layer f゛↓ was 800
If a magnetic field of 7 Gauss (G) or more is applied, the surface of the 611 layer becomes rough, so in this example, a 5011Z AC power source is used to apply a magnetic field of 600 Gauss (G) and 700 Gauss (G).
The alternating current magnetic field of G) was applied to the above-mentioned non-fertile support for 30 seconds.

Then, the saturation magnetic flux density Bm, maximum residual magnetic flux density Br, and squareness ratio Rs before application of the alternating magnetic field were measured.

In addition, as a comparative example, the 68 feelability of a magnetic recording medium was similarly measured in the case where a magnetic paint was simply applied without applying an alternating magnetic field. The results are shown in Table 1.

Table 1: 8m, maximum residual magnetic flux density Br, and squareness ratio Rs were measured and r. In addition, the magnitude of the alternating current magnetic field at this time is 700
Gauss (G). Its essence is shown in Table 2.

Table 2 As can be seen from Table 1 above, in the example in which an alternating magnetic field was applied, the saturation 61'i flux density Bm was clearly higher than in the comparative example in which magnetic paint was applied to the CF on a non-magnetic support. It was recognized that there was an improvement. In addition, the maximum residual magnetic flux density Br,
Similarly, the squareness ratio Rs has a larger value when an alternating magnetic field is applied. Furthermore, the magnitude of the tn field is closer to the coercive force of the magnetic powder at 700 (G) than at 600 (G).
Compared to the case of G), an improvement in the [5i characteristics] was observed.

Next, the time to apply the alternating magnetic field was 5 seconds, 10 seconds 530
As is clear from Table 2 above, as the application time becomes longer, the saturation magnetic flux density Bm and the maximum residual Yuto density Br increase. I can see that it is happening. In other words, when the alternating current magnetic field is applied for 30 seconds rather than 5 seconds, the number of vibrations of the magnetic powder increases, so more magnetic powder is banked into the magnetic layer within this time9. Therefore, if a magnetic paint is applied and then an alternating current E field is applied to the non-magnetic support in the vertical direction, the packing density of the EIt powder increases, thereby improving the saturation magnetic flux density Bm.

Next, after applying the alternating magnetic field, a magnetic field orientation treatment was performed in the longitudinal direction of the nonmagnetic support. In addition, in the above-mentioned magnetic field orientation treatment, magnets are placed facing each other in a direction perpendicular to the coating surface, and a magnetic field is applied with the opposite poles of these magnets having the same polarity, so that the magnetic powder is aligned in the longitudinal direction of the non-magnetic support. An orientation method was used. Then, the magnetic properties of the obtained magnetic recording medium, that is, the saturation magnetic flux density Bm, the maximum residual magnetic flux density Br, and the squareness ratio Rs were measured. In this example, the strength of the applied magnetic field was 700 Gauss (G).

For comparison with this example, the L51 characteristics of a magnetic recording medium obtained by simply applying a magnetic paint without applying an alternating magnetic field and then orienting the medium in the longitudinal direction with a magnetic field were similarly measured. The results are shown in Table 3.

Margin Table 3 Below As can be seen from Table 3 above, longitudinal orientation treatment alone can reduce the saturation magnetic flux density Bm, maximum residual magnetic flux density Br, and squareness ratio Rs to a large value suitable for high recording density. I haven't been able to get any value. On the other hand, when an alternating current magnetic field is applied perpendicularly to the coating surface of the non-magnetic support before the longitudinal orientation treatment, extremely large saturation magnetic flux density Bm, maximum residual magnetic flux density Br, and squareness ratio Rs was gotten. therefore,
According to the obtained magnetic recording medium, reproduction output can be improved by a large to medium 11, and high recording density can be achieved.

〔Effect of the invention〕

As is clear from the above explanation, according to the method of the present invention, an alternating magnetic field is applied in a direction perpendicular to the coating surface of the non-magnetic support before the longitudinal orientation treatment, so the reversal of the magnetic field causes The magnetic powder vibrates, allowing more magnetic powder to be backed into the magnetic layer. As a result, the saturation magnetic flux density of the resulting magnetic recording medium is improved, and the degree of orientation is improved by the vibration of the magnetic powder, resulting in an improvement in the squareness ratio, and these improvements in the saturation magnetic flux density and squareness ratio increase the maximum residual magnetic flux density. improves.

Therefore, according to the method of the present invention, it is possible to produce a magnetic recording medium that can significantly improve the reproduction output and is suitable for increasing recording density.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing an example of the configuration of an alternating current magnetic field applying device. FIG. 2(8) and FIG. 2(B) are schematic diagrams showing the behavior of the θl magnetic powder when magnetic fields in different directions are applied to the alternating current magnetic field applying device. FIG. 3 is a schematic diagram showing the behavior of magnetic powder when an alternating magnetic field is applied. 4 ・ ・ 5 ・ ・ 6 ・ ・ 7 ・ ・ 7 a ・ 8 ・ ・ ...Magnetic pole part, magnetic core, coil, AC power supply, magnetic paint, coating surface, non-magnetic support

Claims (1)

[Claims] After applying a magnetic paint mainly composed of magnetic powder and a binder onto a non-magnetic support, an alternating magnetic field is applied in a direction perpendicular to the coated surface of the non-magnetic support, and then the non-magnetic support A method for manufacturing a magnetic recording medium characterized by magnetic field orientation in the longitudinal direction of the body.