JPS61250834A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve vertical orientation and surface roughness by passing a substrate on which a magnetic paint is coated between main magnets on the opposite surface of one of which ferromagnetic materials are disposed so as to have spaces therebetween to orient the axis of easy magnetization approximately perpendicularly to the film plane then drying the coating. CONSTITUTION:The magnetic paint is coated on the substrate and the substrate is passed through a magnetic field to orient the axis of easy magnetization of the magnetic particles in the coated film approximately perpendicularly to the film plane, then the coated film is dried. The opposed N-S main magnets on the opposite surface of at least one of which the ferromagnetic materials as micro-yokes are disposed so as to have the spaces therebetween are used as the magnetic field. The magnets to be used are the opposed N-S main magnets 11, 12. The ferromagnetic materials 13, 14 are disposed on the opposite surfaces of the magnets 11, 12 so as to have the space therebetween. Preferably about 2-100 pieces of the ferromagnetic materials 13, 14 are disposed on the opposite surfaces of the main magnets 11, 12. The space therebetween is made about 0.5-20mm.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Background Technical Field of the Invention 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 an improved degree of orientation.

Prior art and its problems In recent years, there has been a demand for higher recording density in magnetic recording media. However, in the conventionally widely used in-plane magnetic recording method in which the direction of magnetization is within the plane of the recording medium,
The magnetizations repel each other, making it impossible to increase the density in a fixed position.

Therefore, perpendicular magnetic recording methods, in which the direction of magnetization is perpendicular to the surface of the recording medium and thus do not have repulsion of magnetization, are attracting attention.

Among these, in magnetic recording media that use a coating-type recording layer, magnetic paint is generally applied onto a base film and passed through a magnetic field in an undried state, so that the axis of easy magnetization of the magnetic particles is directed perpendicularly. A manufacturing method is used in which the material is oriented and then dried.

In this case, a method using N-3 opposed silver stones may be used as the orienting magnetic field, but with this method, the time that the coating film is exposed to the orienting magnetic field is short, the orientation is disturbed due to the influence of the demagnetizing field, and the drying Since it takes time to complete the process, there are drawbacks such as the once oriented magnetic particles becoming disordered again during that time.

In order to solve these drawbacks, we used tabular ferromagnetic particles as the magnetic particles and oriented them using a plurality of N-3 opposing silver stones 21, 22 arranged at intervals as shown in Figure 2. A method of drying while oriented by passing through such a magnetic field (Japanese Unexamined Patent Publication No. 58-203631, No. 5)
No. 8-203632 and No. 58-203633), N-3 opposing auxiliary magnet 33. on the exit side as shown in FIG.
A method has been proposed in which N-3 opposed green stones 31 and 32 equipped with 34 are used as an orientation magnetic field, and the magnetic particles are oriented and then dried (Japanese Patent Laid-Open No. 139142/1983).

However, even these methods are still insufficient in terms of the degree of vertical alignment, surface roughness, etc., and further improvements are required.

II. OBJECTS OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a magnetic recording medium with an improved degree of vertical alignment and a good surface roughness.

■Disclosure of invention Such objects are achieved by the invention described below.

That is, in the present invention, a magnetic paint is coated on a support, and the paint is passed between N-3 opposed main cannon stones in which a ferromagnetic material is arranged with a gap on at least one main magnet facing surface. , a method for manufacturing a magnetic recording medium, characterized in that the axis of easy magnetization of the magnetic particles in the coating film is oriented substantially perpendicular to the film surface, and then dried.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

The method for producing a magnetic recording medium of the present invention involves coating a magnetic coating on a support, passing it through a magnetic field as shown below, and aligning the axis of easy magnetization of the magnetic particles in the coating approximately with the film surface. It is oriented vertically and dried.

As the magnetic field, an N-3 opposed main cannon stone is used, in which a ferromagnetic material serving as a minute yoke is arranged with a gap between at least one main magnet facing surface of the N-3 opposed main cannon stone. Then, an N-
It is sufficient that one or more sets of three opposing main gun stones are arranged.

FIG. 1 shows an embodiment in which ferromagnetic materials are arranged with a gap between both main magnet opposing surfaces of the N-S opposing main magnets.

Next, explanation will be given using FIG.

The magnet used in the present invention is the N-3 opposing main gun stone □11
．． 12, in which ferromagnetic bodies 13, 14 are arranged on the opposing surfaces of amphiboid magnets 11, 12 with a gap therebetween.

Such ferromagnetic material 13.14 is the main magnet □! ,
1 and 12, preferably 2-'
It is best to arrange about 100 pieces. Also, the gap is 0.5
-20 mm, preferably about 1-10 mm. The length of each of the ferromagnetic materials 13 and 14 is 0.
The height of each piece is approximately 1 to 10 mm.

As the ferromagnetic material, iron, cobalt, nickel, permalloy, sendust, so-called amorphous alloy, ferrite, silicon steel plate, etc. are preferable.

In addition, the number of main magnets is not limited to one, and a plurality of main magnets may be used. In this case, at least one of the main magnets should include a ferromagnetic material with a gap between them, and the main magnets may be connected with each other without a gap. Various configurations are possible, such as arranging them at intervals, or arranging them at intervals.

In this case, the main magnet has a magnetic field strength of 1000 to 6000G.
It is preferable to use something of a certain degree.

Further, the main magnet may be a permanent magnet, an electromagnet, a solenoid, etc., the gap between opposing magnetic poles is about 5 to 30 mm, and the length of the magnetic poles is about 100 to 5000 mm.

With such a configuration, the magnetic field vibrates, and the effect of this oscillating magnetic field improves the degree of vertical orientation and surface roughness.

The length of one of the ferromagnetic bodies and the range of the gap between the ferromagnetic bodies are the range on which this oscillating magnetic field preferably acts.

Although FIG. 1 shows an example in which the ferromagnetic material 13.14 is provided on the opposing surfaces of both main magnets 11.12, the ferromagnetic material may be provided on only one of the main magnets.

In this case, when using a plurality of N-8 opposing green stones each having a ferromagnetic material arranged with a gap between them on one main magnet opposing surface, there is no particular restriction on the arrangement method.

For example, the ferromagnetic material may be arranged on the coated surface side, on the support side, or alternately or periodically on the coated surface side and the support side.

To apply magnetic paint onto a support, gravure coating,
Any coating method such as reverse roll coating, air knife coating, air doctor Co-1, blade coating, kiss coating, spray Co-1, etc. may be used.

The speed at which the above-mentioned coating material is passed through the above-mentioned magnetic field is 2~
A speed of about 500 m/min is preferable.

Drying after the orientation treatment is preferably carried out at 30 to 150°C and at a speed of about 2 to 500 m/min using a heater source such as hot air or a far infrared lamp.

The magnetic powder used in the magnetic paint of the present invention is a-F e203, F e304.

Co doped a-Fe203゜ Co-doped cx-F e203-F e203 solid solution.

Cr02. Go type compound coated type a-Fe203°C
Examples include o-type compound-coated Fe3O4, Ba ferrite, etc., which are granular, acicular, plate-like, polyhedral, etc., and Ba ferrite is particularly preferred.

The Ba ferrite is preferably a hexagonal plate-like ferrite, and furthermore, in order to improve the degree of vertical orientation, it is desirable to include one with a plate ratio (average grain size/average thickness) of 6 or more. The plate ratio can be controlled up to about 30.

As for Ba ferrite, Ba Fe 120 +9 etc.c7) Ba7. Light and B a 7 x light c7) Ba, Fec7) Part of Ca, Sr, Pb, Co, Ni, Ti, Cr, Zn, I
Examples include those substituted with n, Mn, Cu, Ge, Nb, Zr, and other metals.

Further, various binders may be used for the magnetic paint, but those obtained by curing radiation-curable compounds are preferred.

Specific examples of radiation-curable compounds include acrylic double bonds such as acrylic acid, methacrylic acid, or their ester compounds, which exhibit radically polymerizable unsaturated double bonds, and allylic double bonds such as diallylphthalate. It is a thermoplastic resin containing or introducing into its molecules a group that can be crosslinked or polymerized and dried by radiation irradiation, such as a double bond or an unsaturated bond such as maleic acid or a maleic acid derivative.
Any compound having an unsaturated double bond that undergoes cross-linking polymerization upon irradiation with radiation can be used.

Thermoplastic resins that contain or introduce groups that can be crosslinked or polymerized and dried by radiation irradiation into their molecules include maleic acid, fumaric acid, etc. From the viewpoint of radiation curability, etc., the amount is 1 to 40 mol%, preferably 10 to 30 mol%, in the acid component.

As examples of thermoplastic resins that can be modified into radiation-curable resins, the following vinyl chloride copolymers are particularly suitable.

Vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl alcohol copolymer, vinyl chloride-vinyl alcohol-vinyl propionate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-acetic acid Vinyl-vinyl alcohol-maleic acid copolymer, vinyl chloride-vinyl acetate-terminal OH side chain argyl group type polymer, such as VROH, VYNClVYEGX, VERR, VYE manufactured by UCC
Examples include S, VMCA, VAGH, and the like.

Then, acrylic double bonds, maleic acid double bonds, and allylic double bonds are introduced into this material to perform radiation-sensitivity modification.

These may contain carboxylic acids.

In addition, saturated polyester resins, polyvinyl alcohol resins, epoxy resins, phenoxy resins, cellulose derivatives, etc. are also suitable.-0Other resins that can be used for radiation sensitivity modification include polyfunctional polyester resins, Polyether ester resin 2, polyvinylpyrrolidone resin and derivatives (PVP olefin copolymer), polyamide resin, polyimide resin, phenol resin, spiroacetal resin, acrylic resin containing at least one type of acrylic ester and methacrylic ester containing a hydroxyl group as a polymerization component Resin etc. are also effective.

These may be used alone or in combination of two or more.

Elastomers or prepolymers can also be used, preferred examples being polyurethane elastomers or prepolymers.

The use of polyurethane is wear resistant, and the base film,
For example, it is particularly effective in terms of good adhesion to PET film. Examples of urethane compounds include 2,4-toluene diisocyanate, 2,6-
), 1.3-xylene diisocyanate, 1,4-xylene diisocyanate, 1.5
-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 3,3
'-Dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethylbiphenylene diisocyanate,
Various polyvalent isocyanates such as 4,4'-biphenylene diisocyanate, hexamethylene diisocyanate, inlon diisocyanate, dicyclohexylmethane diisocyanate, Desmodur L, Desmodur N, and linear saturated polyesters (ethylene glycol, diethylene glycol, glycerin, trimethylolpropane) , 1,4-methanediol, 1,6-hexanediol, pentaerythritol, sorbitol, neopentyl glycol, 1,4-cyclohexane dimetatool, phthalic acid, isophthalic acid,
(by condensation polymerization with saturated polybasic acids such as terephthalic acid, succinic acid, adipic acid, sebacic acid), linear saturated polyethers (polyethylene glycol, polypropylene glycol, polytetramethylene glycol), caprolactam, hydroxyl-containing acrylic acids Polyurethane elastomers and prepolymers made of polycondensates of various polyesters such as esters and hydroxyl-containing methacrylic esters are effective.

By reacting the terminal isocyanate group or hydroxyl group of these urethane elastomers with a monomer having an acrylic double bond or an allylic double bond,
Modification to radiosensitivity is very effective.
It also includes those containing ○H, COOH, etc. as a polar group at the terminal.

Furthermore, monomers having an unsaturated double bond having an active hydrogen that reacts with an incyane group, such as mono- or diglycerides of long-chain fatty acids having an unsaturated double bond, and having radiation curability are also included.

The use of these urethane elastomers 117 with the acrylic modified vinyl chloride copolymer described in -1- is particularly suitable for improving the degree of orientation and surface roughness.

In addition, acrylonitrile-butadiene copolymer elastomer and polybutadiene elastomer are also suitable.

In addition, polybutadiene cyclized product, CBR- manufactured by Japan Synthetic Rubber Co., Ltd.
M901 also has excellent properties when combined with thermoplastic resin.

Other suitable thermoplastic elastomer and prepolymer systems include styrene-butadiene rubber, chlorinated rubber, acrylic rubber, isoprene rubber, and its cyclized product (ClR701 manufactured by Nippon Synthetic Rubber), epoxy-modified rubber, internal plastic Elastomers such as saturated linear polyester (Toyobo Vylon #300) can also be effectively used by subjecting them to radiation-sensitive modification treatment.

In addition to these, various radiation-curable oligomers having unsaturated double bonds and sulfuric acid can also be suitably used.

The weight ratio of the binder to the magnetic powder is about 1:1 to 1:9.

Furthermore, the magnetic paint may contain a solvent, an inorganic pigment, a dispersant, a lubricant, and the like.

Various resins such as polyester, polyamide, polyimide, etc. can be used as the support.

Further, the support may be provided with a base layer or a base treatment.

After forming the magnetic layer, various back coat layers and top coat layers can also be formed.

■Specific effects of the invention According to the present invention, N-3 opposing green stones are formed by coating a magnetic paint on a support and disposing a ferromagnetic material on the opposing surface of at least one N-3 opposing green stone with a gap between them. Since the magnetic particles in the coating are dried by passing through green stones with their axes of easy magnetization oriented almost perpendicular to the film surface, the degree of vertical orientation is improved and magnetic recording with good surface roughness is achieved. A method for producing a medium is obtained.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

Example: Macrogonal barium ferrite (B a Fe 120
A magnetic paint was prepared in the following manner using 4g of Ba and Fe (synthesized by a hydrothermal synthesis method) in which Ba and Fe were partially substituted.

Barium ferrite l-120 parts by weight (Hc='800) α-A 203 (0.5μ powder) 2 parts by weight Carbon black (20 mg) 10 parts by weight Solvent (MEK/l-luene: 50150) 100 parts by weight above The composition was mixed in a ball mill for 3 hours to thoroughly wet the barium ferrite.

Next, as a binder, vinyl chloride-vinyl acetate-vinyl alcohol copolymer (
Contains maleic acid; MW 40,000) 6 parts by weight (solid content), acrylic double bond-introduced vinyl chloride-vinyl acetate-vinyl alcohol copolymer (contains maleic acid; MW 20,000) 12 parts by weight (solid content) 9 parts by weight of acrylic double bond-introduced polyether urethane elastomer (MW40.000) (in terms of solid content), 3 parts by weight of pentaerythritol triacrylate, 200 parts by weight of solvent (MEK/toluene: 50150), 4 parts by weight of stearic acid 1 part and 2 parts by weight of butyl stearate were mixed and dissolved.

This was placed in a ball mill containing the magnetic powder mixture and mixed and dispersed again for 42 hours. Using the thus obtained magnetic paint, gravure coating was performed on a 75 gm polyester film.

The sample prepared in this manner is referred to as sample A.

This sample A is attached to N-S opposing main magnets 11.12 (magnetic field strength of the main magnets is 3000 G), in which ferromagnetic materials 13.14 are arranged with a gap between both main magnet opposing surfaces as shown in Fig. 1.
The film was passed through the film at a speed of 30 m/min, and vertically oriented while drying. Thereafter, it was dried using a far-infrared lamp. The main magnet consists of 10 magnets each having a magnetic pole length of 5'Omm arranged without any gaps.

This is designated as sample B.

The ferromagnetic material is made of barium ferrite, each 5 mm in length and 2 mm in height, and each gap is 1.
0 mm, and 30 magnets were arranged on each opposing surface of both main magnets 11 and 12.

Next, sample A is placed in an N-S facing magnet 21 as shown in FIG.
22 (magnetic field strength 3000G, magnetic pole length 50mm) between 10 pieces arranged at 10cm intervals at a speed of 30cm.
m/min and vertical orientation while drying.
Then, it was dried using a far-infrared lamp.

This is designated as sample C.

Furthermore, sample A is attached to an N-S opposing main magnet 3 with N-S opposing auxiliary magnets 33 and 34 attached to the exit side as shown in FIG.
It was introduced and exited between 1.32 and oriented vertically. after that,
It was dried in the same manner as sample B.

Use this as a sample.

In this case, 10 main magnets have a magnetic field strength of 3000 G and a magnetic pole length of 50 mm, and one auxiliary magnet has a magnetic field strength of 1500 G and a magnetic pole length of 3 mm. 20 auxiliary magnets were used.

Note that sample B is not provided with a ferromagnetic material and is designated as E.

In addition, the magnetic gaps of Samples B, C, D, and H were 15 mm.The characteristics of Samples B, C, D, and H were investigated.

The characteristics were evaluated as follows.

(1) Perpendicular orientation The squareness ratio B r /B m in the vertical direction of the magnetic tape was measured, and demagnetizing field correction was performed.

(2) Surface roughness R20 It was determined by the 20-point average method from a chart obtained using Talystep (manufactured by TAYLOR-HOBSON).

The cutoff was 0.17 mm and the needle pressure was 0.1×2.5 JL.

The results are shown below.

Sample strength, vertical orientation R20B (invention) 0.80 0.051Li+C (comparison)
0.68 0.07pmD (comparison)
0.68 0.071LmE (comparison) 0.
60 0.07 gm or more'', the effects of the present invention are clear.

[Brief explanation of drawings]

Figure 1 shows one of the N-S opposing main magnets in which ferromagnetic material is arranged with a gap between both main magnet opposing surfaces in the present invention.
It is a front view for explaining an example. FIG. 2 is a front view for explaining an example of conventional N-3 opposing silver stones arranged with gaps provided therebetween. FIG. 3 is a front view for explaining an example of a conventional N-5 opposed main cannon with an N-5 opposed auxiliary magnet attached to the exit side. Explanation of symbols ■... Coating material, 11.12... N-3 opposing main gun stone, 13.14...
...Ferromagnetic material, 21.22...N-3 opposed silver stone. 31.32...N-3 opposing main gun, 33.34...
...N-3 opposing auxiliary magnet, a...Direction for passing the coated material Applicant: TDC Co., Ltd. Agent Patent attorney: Yo Ishii - FIG, 1 FIG, 2 FIG, 3

Claims (4)

[Claims] (1) Apply magnetic paint on a support, pass it between N-S opposing main magnets in which a ferromagnetic material is arranged with a gap on at least one main magnet opposing surface, and apply the magnetic paint to the support. A method for producing a magnetic recording medium, which comprises drying the magnetic recording medium by orienting the axis of easy magnetization of the magnetic particles therein almost perpendicularly to the film surface. (2) The method for manufacturing a magnetic recording medium according to claim 1, wherein the gap between the ferromagnetic materials disposed on the surface facing the main magnet is 0.5 to 20 mm. (3) The method of manufacturing a magnetic recording medium according to claim 1 or 2, wherein the ferromagnetic material is arranged on both main magnet facing surfaces. (4) The method for manufacturing a magnetic recording medium according to any one of claims 1 to 3, wherein a plurality of N-S opposing main magnets each having a ferromagnetic material arranged therein are arranged.