JPS59148140A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To produce a magnetic layer containing ferromagnetic particles orientated at random by coating a magnetic coating material to a belt-shaped nonmagnetic supporter and providing many magnets so that N and S poles producing magnetic fields rectangularly to the carrying direction of the supporter are set alternately before the magnetic coating material is dried and hardened. CONSTITUTION:A magnetic coating material containing the ferromagnetic powder, a binder, etc. is coated by a coating device 3 on a belt-shaped nonmagnetic supporter 2 which is carried to a take-up part 6 from a feed part 1. The supporter 2 is processed at a non-orientating means 4 before the magnetic coating material is dried and hardened and then passed through a drying oven 5 to harden the coating material. The means 4 is formed by providing magnets having magnetic fields in the carrying direction and the intra-face rectangular direction of the supporter 2 where N and S poles are alternately continuous above or/and under the supporter 2. The field intensity which reduces gradually in the carrying direction of the supporter 2 has an effect through above-mentioned magnetic fields. Thus the anisotropy of electromagnetic characteristics is produced owing to the orientation of magnetic particles. This prevents the variance of a reproduced output signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium in which a magnetic recording layer is provided on a non-magnetic support by a coating method, and more specifically, the present invention relates to a method for manufacturing a magnetic recording medium in which a magnetic recording layer is provided on a non-magnetic support, and more specifically, the present invention relates to a method for disordering the orientation of ferromagnetic fine particles in the magnetic recording layer. This invention relates to a method of manufacturing a disk-shaped or sheet-shaped magnetic recording medium.

Generally, flexible magnetic disks and magnetic sheets are made from a strip-shaped nonmagnetic support (polyethylene terephthalate, triacetyl cellulose, etc.).

Diacetyl cellulose, vinylidene chloride, polypropylene, etc.) are dissolved by a solvent while continuously transporting the binder (eg vinyl chloride vinyl acetate copolymer) in the longitudinal direction of the support.

Vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer.

Acrylic acid ester vinylidene chloride copolymer.

Other copolymers with acrylic acid, urethane elastomers, nylon-silicone resins.

Nitrocellulose, polyvinyl chloride, vinylidene chloride acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, styrene butadiene copolymer, phenolic resin, epoxy resin, polyurethane.

Urea resin, melamine resin, polyester resin.

Ferromagnetic fine particles (γ-Fe 203 , Fe 304 ,
Co-doped γ-Fe203 and Fe3O4,
CrO2, etc.) using top reverse coating, bottom reverse coating, Dr. Co. 1-, gravure coating, etc., but during manufacturing, ferromagnetic particles are arranged in a specific direction, causing differences in the magnetic recording medium. When anisotropy occurs, anisotropy also occurs in magnetic and electromagnetic properties in various directions.

When the magnetic particles are arranged along the coating direction, if the magnetic recording medium is a magnetic disk, the reproduction output signal in the coating direction will be higher than that in the other direction, and as a result, the reproduction output signal level read from the magnetic disk will be Changes as the magnetic disk rotates.

Therefore, for example, when manufacturing a flexible magnetic disk that is used by rotating, the orientation of the magnetic particles must be physically removed in the general magnetic tape manufacturing process so that the ferromagnetic particles do not have linear orientation. However, even if such means are used, linear directionality still occurs in the coating direction due to the flow orientation during coating, resulting in fluctuations in the reproduction output level.

The purpose of the present invention is to eliminate the orientation of ferromagnetic particles in the conveying direction of a coated web in the production of flexible magnetic disks or magnetic sheets by using the following non-orientation means (magnet), and to uniformly eliminate disorder in the orientation of ferromagnetic fine particles. An object of the present invention is to provide a method for manufacturing a magnetic recording medium that improves electrical characteristics by achieving the following characteristics.

The method for manufacturing the magnetic recording medium of the present invention involves coating a strip-shaped non-magnetic support in the longitudinal direction of the support with a coating solution in which fine ferromagnetic particles are dispersed in a binder dissolved in a solvent. In a method for manufacturing a magnetic recording medium in which a magnetic recording layer is provided by a method, before the applied coating liquid is dried and solidified,
A large number of magnets (at least one magnet with a large number of poles arranged alternately) are used so that the N and S poles are alternately arranged so as to form a magnetic field perpendicular to the conveying direction of the coated web. The method is characterized in that the orientation of the ferromagnetic particles is made disordered by the non-orientation means provided, and then the coating liquid is dried and solidified to hold and fix the ferromagnetic fine particles with disordered orientation. .

That is, as shown in FIG. 1A or 1B, a magnet with alternating N poles and 8 poles that controls the magnetic field in the coating web conveyance direction and the in-plane angle direction, or as shown in FIGS. 1C to 1E. Ferromagnetic fine particles are made non-oriented by passing a web between two or more magnets, or between two or more magnets, as shown in FIG. Furthermore, as illustrated in FIGS. 2A to 2C, the magnets shown in FIG. 1A or 1B have the same polarity (N pole or S pole) or alternate poles, and further, as shown in FIG. 2C, there is a phase difference in the magnetic field. A plurality of magnet arrays are arranged above, below, or narrowed vertically so that the strength of the magnetic field on the coated web surface overflows in the traveling direction of the web 10 and gradually decreases. The orientation of the ferromagnetic fine particles in the applied coating liquid is disordered by passing through the coating liquid, and the coating liquid is then dried and solidified to maintain and fix the disordered orientation of the ferromagnetic fine particles. That is.

The present invention will be further explained in detail below with reference to FIG.

FIG. 3 is a schematic diagram showing a magnetic recording medium manufacturing apparatus based on the present invention.

In FIG. 3, a strip-shaped non-magnetic support 2 made of polyethylene terephthalate, acetate, etc. is sent out from a delivery section J, and ferromagnetic fine particles are dispersed in a binder dissolved in a solvent by a coating device 3. A coating liquid is applied. When this coating liquid is applied, the ferromagnetic fine particles 11 are fixed in the application direction due to flow orientation and have directionality (fourth
1% I). 1A to IE or 2A before the coating liquid applied on the non-magnetic support 2 is dried and solidified.
The orientation of the ferromagnetic particles 11 in the coating liquid is disordered by the magnetic field generated by the non-orientation means (magnet) 4 illustrated in FIGS.

These methods use lines of magnetic force having a plane angle in the coating direction in order to eliminate flow orientation during coating. Therefore, Figure 1-1, 1. A magnet with alternating north and south poles is used as one stage as shown in -2 (basic type). In order for magnetic lines of force to be generated uniformly throughout the coating process, the first step is to C, ID,
As shown in the IE diagram, it is preferable to arrange the second row of magnets offset from the first row (by creating a phase difference).

In order to further achieve uniform non-orientation, 2A-2C
As shown in the figure, it is preferable to use a plurality of stages of magnets and arrange them so that the magnetic force of each stage is gradually weakened along the web conveyance direction. The size of the magnet is width 05~3c7Il length 2~1oc7
It is effective to have a distance of about 1 to 10 mm between the north pole and the south pole.

After the orientation of the ferromagnetic fine particles becomes disordered, drying oven 5
The solvent in the coating liquid is removed, the binder is dried and solidified, and the disordered ferromagnetic fine particles are held and fixed. The nonmagnetic support 2 provided with the magnetic recording layer in which the ferromagnetic fine particles are non-oriented in this manner is wound up by the winding section 6.

Next, an embodiment of the method of the present invention for manufacturing a magnetic disk using the flexible magnetic disk manufacturing apparatus shown in FIG. 3 will be described.

Example 1) 1) As a coating liquid: Magnetic substance Co - FeOx 400 parts Binder Polyurethane and Tuboran 3022) 601/Vinyl chloride vinyl acetate copolymer (VMCI-() 40 parts Dispersant lecithin 5 // Lubricant stearic acid 5 tt chicane 30 melt
Agent Methyl ethyl ketone 500/1 Methyl isobutyl ketone 20 (J# cyclohexanone 2001/) with a viscosity of 70 PS 11
) Coating conditions: Coating method: Doctor blade coating speed: 30771/m1n111) Magnet installation conditions: Magnet material: Rare earth cobalt magnet (size) C
mX 5Crn, spacing 3mm) Magnet configuration: 1st
N pole shown in figure A.

A configuration in which S poles were arranged alternately was arranged at right angles to the coated web.Distance between magnet and support: 2-5 cm.Strength of magnetic field at main surface of support: 250G. The results of magnetic recording provided on a non-magnetic support using a magnetic disk manufacturing device are shown in the first column.

Example 2) 1) Coating liquid 11 The conditions were the same as in Example 1).
) Under the magnet installation conditions, the magnet configuration is as shown in Fig. 2B, and the magnet shown in Fig. 1A, in which N poles and S poles are arranged in succession, is aligned in a straight line in the longitudinal direction of the coating from N pole → S pole → N pole. →S pole (
Or, the strength of the magnetic field of the first magnet is 300G, and the strength of the magnetic field of the second magnet is 250G.

Table 1 shows the results of magnetic recording on a non-magnetic support using the magnetic disk manufacturing apparatus shown in Fig. 3, with the third magnet arranged so as to reach 200G and the fourth magnet 150G. Shown below.

Comparative Example 1) Table 1 shows, as a comparative example, the results of a non-magnetic field method manufactured under the same conditions as Example 1) or Example 2) except that no magnet was provided in FIG.

For flexible magnetic disks, the squareness ratio in the coating direction (residual magnetic flux density/maximum magnetic flux density) divided by the squareness ratio in the direction perpendicular to the coating (-orientation ratio) is preferably 095 or more in terms of electromagnetic properties. However, as shown in Table 1, the orientation ratio of Comparative Example 1 using the non-magnetic field method was 0.86, while Example 1 had an orientation ratio of 0.86.
), the orientation ratio is 0.95. In the non-oriented magnet having the configuration shown in FIG. 2B in Example 21, an extremely good disordered state with an orientation degree ratio of 0.986 was achieved, giving results that fully satisfied the required characteristics of a flexible magnetic disk. I understand. The first orientation magnet. Figure A - 1st
The strength of the magnetic field reaching the coated surface can be set to a predetermined value by using a permanent magnet configured as shown in Figure E or Figures 2A to 2C, or even an electromagnet that generates a magnetic field similar to these permanent magnets. The same effect can be obtained by doing this, and which one to choose is determined by the convenience of installation.

In addition, the strength of the magnetic field on the coated surface depends on the size of the ferromagnetic particles,
In addition to the shape and viscosity of the coating liquid, it is determined by the coercive force of the magnetic material, but for those with a coercive force of about 250 to 7000e, the strength of the magnetic field on the coated surface is determined by the magnet shown in Figure 1A-16. is about 250G in the range of 50 to 500G, and in the case of the magnet configuration illustrated in Figures 2A-2C, the magnetic field strength from the first magnet is about 300G, and the strength of the magnetic field is about 50G.
It has been found that a magnet configuration that reduces by as much as 0 G gives favorable results. It is no secret that a magnetic material with a high coercive force (for example, a metal magnetic material) requires a larger orienting magnetic field.

In addition, when a permanent magnet is used as a magnet used to achieve disordering of magnetic particles in the present invention,
Examples of the material include alnico magnets, Ba-ferrite magnets, and rare earth cobalt magnets.

As described above, as illustrated in FIGS. 1A-1 and 1E, the magnetic field generated from the plurality of N and S poles and forming an angle perpendicular to the direction of conveyance of the coated web causes the magnet to move to the second A-1.
As illustrated in Figure 2C, the orientation of the ferromagnetic fine particles is maintained in a disordered manner by passing over a plurality of magnets with magnetic fields of different or the same polarity gradually decreasing in the conveying direction of the coated web. , the electrical properties of magnetic recording media such as flexible magnetic disks or magnetic sheets can be improved.

[Brief explanation of the drawing]

1st. Figures A-16 and 2A-2C are schematic diagrams showing each side of the non-orienting means used in the method of the present invention, and Figure 3 is a schematic diagram showing an example of an apparatus for carrying out the method of the present invention. FIG. 4 is a schematic diagram showing the orientation of particles in a magnetic recording medium before the ferromagnetic fine particles are rendered non-oriented by the method of the present invention, and FIG. 5 is a schematic diagram showing the state after the non-orientation. 1... Sending part 2... Non-magnetic support 3...
・Application device 4...Means for alcohol-free self-improvement (
Magnet) 5... Drying oven 6... Winding part 10
...Magnetic recording medium (web) 11...-Ferromagnetic fine particles 15- 231-

Claims (1)

[Claims] 1) Coating a coating liquid in which ferromagnetic fine particles are dispersed in a binding agent dissolved in a solvent onto a strip-shaped non-magnetic support along the longitudinal direction of the support. In a method for manufacturing a magnetic recording medium in which a magnetic recording layer is provided, before the applied coating liquid is dried and solidified, the N pole is set so as to form a magnetic field at an angle with respect to the conveying direction of the coated web. , the orientation of the ferromagnetic particles is made disordered by a non-orientation means consisting of a large number of magnets arranged so that the S poles are arranged alternately, and then the coating liquid is dried and solidified to produce ferromagnetic particles with disordered orientation. A method for manufacturing a magnetic recording medium characterized by holding and fixing fine particles. 2) The non-orientation means is not an arrangement of multiple rows of magnets, and the strength of the magnetic field formed by each arrangement of magnets is such that it gradually decreases along the conveyance direction of the web. A method for manufacturing a magnetic recording medium according to claim 1.