JPS6313124A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which is small in output fluctuation and is particularly excellent in an electromagnetic conversion characteristic by specifying the ratio between the max. value and min. value of the residual magnetic flux density in the peripheral direction of the recording medium to a prescribed value. CONSTITUTION:The magnetic recording medium is manufactured by coating a magnetic coating compd. on a long-sized nonmagnetic substrate 2 which running the same at a specified speed, and blanking the substrate to a prescribed disk shape after drying the coating to core. The value obtd. by dividing the min. value of the residual magnetic flux density in the peripheral direction of tracks by the max. value is specified to 0.95, more particularly 0.98-1.0. The value obtd. by dividing the average squareness ratio in the perpheral direction by the average squareness ratio in the diametral direction is preferably 0.97-1.03, more particularly preferably 0.98-1.02. Looped magnets 5' disposed with plural pieces of unit magnets 51' so as to be alternately varied in poles are provided to either above or below the substrate 2. The loop-shaped plane is positioned parallel with the plane of the substrate 2 and the straight line part of the loop is positioned perpendicular to the progressing direction of the substrate. The unit magnets 51' are continuously moved in one direction on the loop.

Description

[Detailed description of the invention] Background of the invention Technical field The present invention relates to a magnetic recording medium and a method for manufacturing the same.

More specifically, the present invention relates to a disk-shaped magnetic recording medium having a magnetic layer containing magnetic powder and a binder, and a method for manufacturing the same.

Prior art and its problems Various types of disk-shaped magnetic recording media have been put into practical use as so-called floppy disks. When using such a disk-shaped medium, recording and reproduction are performed by sliding a magnetic head in the circumferential direction of the disk while rotating the medium. If the contained magnetic powder is oriented in a certain direction, output fluctuations called modulation, in which maximum output and minimum output are alternated, occur with rotation.

If the modulation becomes large, it becomes impossible to accurately read the information recorded on the disk-shaped medium, which is sometimes a major factor in reducing reliability, which is not desirable in practice.

Such modulation is thought to be caused by various characteristics of the disk-shaped medium, such as the degree of orientation of the magnetic powder, but the correlation between improved modulation and the characteristics of the disk-shaped medium is still unclear. It is difficult to obtain a magnetic disk with a stable modulation value and a small modulation value.

Therefore, there is a demand for the development of a magnetic recording medium that has good modulation and excellent electromagnetic conversion characteristics in digital recording.

By the way, the method for manufacturing a disk-shaped magnetic recording medium is generally to coat a long non-magnetic support with a magnetic paint, then force dry it with hot air, etc., and then form the magnetic layer into a disk shape with the desired thickness. Manufactured by punching.

In the disk-shaped magnetic recording medium manufactured in this manner, the magnetic powder contained in the magnetic layer must have a so-called random orientation without regularity, as described above.

However, in normal manufacturing methods, shear stress is applied to the magnetic layer during coating such as gravure coating, transportation and smoothing treatment after coating, and therefore The magnetic powder is mechanically oriented or naturally oriented in the feeding direction of the support.

Various proposals have been made for canceling such mechanical or natural orientation of magnetic powder and obtaining random state orientation.

For example, one that uses a magnetic field that alternately changes the direction of the magnetic field and decreases the strength of the magnetic field (Japanese Patent Laid-Open No. 54-1
No. 59204), a non-orientation roller in which a large number of cylindrical permanent magnets are closely arranged in the axial direction of the roller so that the same kind of magnets face each other, or an orientation that acts to orient the roller in a direction that coincides with the longitudinal direction of the film. Combined use with equipment (JP-A No. 57-189344, No. 57-189345)
(Japanese Unexamined Patent Publication No. 58-141446), which uses a magnetic field that is magnetized obliquely to the longitudinal direction of the film, and the direction of magnetization of several strip magnets magnetized in the thickness direction. A device that alternately reverses the direction of travel
124029), a random orientation device (Japanese Unexamined Patent Publication No. 138737/1983) which passes a film through a winding frame in which a predetermined coil has not been wound, and applies a magnetic field in the width direction of the film.

However, these methods are affected by various conditions such as the physical properties of the magnetic powder used, the viscosity of the magnetic paint, the degree of natural orientation due to mechanical action, and the film conveyance speed, so that it is possible to easily and stably spread the film over the entire width of the support. The disadvantage is that it is difficult to obtain a uniform random assimilation.

In addition, streaks may occur in the support conveyance direction due to uneven thickness of the magnetic paint, or streaks may occur due to the orientation device.
Unnecessary unevenness may be formed on the magnetic layer, which is not preferable.

(2) Purpose of the Invention An object of the present invention is to provide a magnetic recording medium with small output fluctuations and excellent electromagnetic conversion characteristics, and a method for manufacturing the same.

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

That is, in the first invention, in a disk-shaped magnetic recording medium having a magnetic layer containing magnetic powder and a binder on a non-magnetic support, when the residual magnetic flux density φr in the track circumferential direction of the medium is measured, φr The magnetic recording medium is characterized in that the value obtained by dividing the minimum value by the maximum value is 0.95 to 1.

The second invention is to apply a magnetic paint containing magnetic powder and a binder onto a long non-magnetic support, apply a magnetic field with a magnet facing the support, dry it, and then,
In the method for manufacturing a magnetic recording medium punched into a disk shape, the magnet is formed by connecting a large number of unit magnets facing the support so that they alternately have different polarities to form two substantially straight lines having a width greater than the width of the support. It has a loop shape consisting of a section and two curved sections connected to this straight section, and the alternately different polarity arrangement surface of the loop shape plane is approximately parallel to the plane of the support, and the direction of travel of the support and the loop shape are parallel to each other. When the unit magnet is moved in one direction within the loop shape and the residual magnetic flux density φr in the circumferential direction of the track of the medium is measured, the minimum value of φr is the maximum value. The divided value is 0.
95 to 1.

The third invention is to apply a magnetic paint containing magnetic powder and a binder onto a long non-magnetic support, apply a magnetic field with a magnet facing the support, dry it, and then,
In a method for manufacturing a magnetic recording medium punched into a disk shape, the magnets are placed above and below a support, and each magnet has a large number of unit magnets facing the support so that they alternately have different polarities. It has a loop shape consisting of two substantially straight straight parts that are connected to each other and have a width greater than the width of the support, and two curved parts that are connected to the straight parts. It is installed almost parallel to the plane and in such a way that the direction of movement of the support and the linear part of the loop shape are almost at right angles, and each unit magnet of each magnet is moved in one direction within the loop shape, and the upper and lower When the unit magnets move in the same direction and the residual magnetic flux density φr in the circumferential direction of the track of the medium is measured, the value obtained by dividing the minimum value of φr by the maximum value is 0.95 to 1. This is a method of manufacturing a magnetic recording medium.

A fourth invention is to apply a magnetic paint containing magnetic powder and a binder onto a long non-magnetic support, apply a magnetic field with a magnet facing the support, dry it, and then,
In a method for manufacturing a magnetic recording medium punched into a disk shape, the magnets are placed above and below a support, and each magnet is opposed to the support so that a large number of unit magnets alternately have different polarities. It has a loop shape consisting of two substantially straight straight parts that are connected to each other and have a width greater than the width of the support, and two curved parts that are connected to the straight parts. The magnets are installed almost parallel to the plane and in such a way that the direction of movement of the support and the linear part of the loop shape are almost at right angles, and each unit magnet of each magnet is moved in one direction within the loop shape, and the upper and lower When the movement direction of the unit magnet is in the opposite direction and the residual magnetic flux density φr in the circumferential direction of the track of the medium is measured, the value obtained by dividing the minimum value of φ'r by the maximum value should be 0.95 to 1. A method of manufacturing a magnetic recording medium is characterized in that:

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

The magnetic recording medium of the present invention has a magnetic layer containing magnetic powder and a binder on a nonmagnetic support.

Such magnetic recording media are usually produced by coating a long non-magnetic support at a constant speed with a magnetic coating using a gravure coater, reverse roll coater, etc., and then drying and curing the coating. , manufactured by punching into a predetermined disc shape. In the magnetic recording medium manufactured in this way, when the residual magnetic flux density φr in the track circumferential direction measured on the magnetic layer is measured, the value obtained by dividing the minimum value of φr by the maximum value (φr min /φr max) is 0
．． 95-1, more preferably 0.98-1.0.

If this value is out of the above range, the modulation will increase, which is not practical.

Furthermore, the value obtained by dividing the minimum value of the squareness ratio φr/φm・ in the track circumferential direction by the maximum value is (φr/φm
m) min/(φr/φ01) max is 0.95~
1, particularly preferably 0.98 to 1.0. Further, it is preferable that the value obtained by dividing the average squareness ratio in the circumferential direction by the average squareness ratio in the radial direction is 0.97 to 1.03, particularly 0.98 to 1.02. Outside these ranges, it becomes difficult to improve modulation, which is undesirable.

In addition, the average squareness ratio φr/φm in the track circumferential direction of such a magnetic recording medium is 0.55 to 0.65, particularly 0.55 to 0.65.
58 to 0.63 is preferred. φr/φm value is 0.55
If it becomes less than 0.65 or exceeds 0.65, there is sufficient output.

or the resolution may not be satisfactory.

As a method for measuring φr and φr/φm as described above, for example, four lines passing through the center of the disk are drawn to divide the disk into eight approximately equal parts, starting from the index hole provided in the disk medium. Eight positions created by the intersection of the straight line and the zero track (outermost track) of the disk are used as measurement points, and the magnetization curves at these positions are measured and obtained, and from this curve φr, φI
read.

Then, from the maximum and minimum values of φr and φr/φm at the eight points obtained, (φr min /φr
a+ax ) and (φr/φm)win/(φr/φm
) Calculate max. Roughly calculate the average squareness ratio φr/φ゛l in the circumferential direction of the track. In addition, the squareness ratio in the radial direction is read in the same way, and the orientation ratio is calculated by dividing the value in the circumferential direction obtained previously by that value. Note that the number of measurement points can be 8 or more, but In that case, it is preferable to provide measurement points on the side of multiples of 4 for measurement.

In the case of a so-called double-sided recording magnetic recording medium, the above measurements are usually performed after peeling off the magnetic layer on one side with a solvent or the like, but measurements may also be made with the magnetic layers left on both sides.

As the nonmagnetic support of the magnetic recording medium of the present invention having such characteristic values, a flexible resin is used, and polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate, Various resins such as polyimide, polycarbonate, polysulfone, polyethylene naphthalate, aromatic aramid, and aromatic polyester are used.

Among these, it is particularly preferable to use polyester, polyamide, polyimide, and the like.

Note that the thickness of the substrate is approximately 20 to 150 μl.

Further, as the magnetic powder contained in the magnetic layer, metal magnetic powder, γ-Fe203 magnetic powder, cobalt-coated iron oxide magnetic powder, etc. are used.

As metal magnetic powder, ! ) a-FeOO) ((Goethite).

β-FeOOH (Akaganite), y-FeO
Iron oxyhydroxide such as OH (Lepidocrocite) and: a-Fe203, y-Fe203.

Iron oxides such as Fe204, y-Fe203-Fe203 (solid solution); metals such as Co, Mn, Ni, Ti, Bi, B, Ag, etc.
one or more doped with an aluminum compound or a silicon compound adsorbed and deposited on the surface,
Add in reducing gas stream! #S reduction method to produce iron or magnetic powder mainly composed of iron; 2) method of producing liquid phase reduction with NaBH4 from a metal salt aqueous solution; 3) or in a low pressure inert gas atmosphere. It can be obtained by a method such as evaporating a metal.

The composition of the metal magnetic powder is Fe, Co.

Cr, Mn, and Co are added to Ni alone and alloys thereof, or to these alone and alloys.

Ni5 as well as Zn, Cu, Zr, and Al.

Metals to which Ti, Bi, Ag, Pt, etc. are added can be used.

Furthermore, the effects of the present invention are not lost even when small amounts of nonmetallic elements such as B, C, Si, P, and N are added to these metals.

Alternatively, a partially chambered or carbonized metal magnetic powder such as Fe4N may be used.

Furthermore, the metal magnetic powder may have an oxide film on the particle surface.

Magnetic recording media using metal magnetic powder with such an oxide film suffer from a decrease in magnetic flux density due to external environments such as temperature and humidity.
Although this method is advantageous in preventing deterioration of characteristics due to the occurrence of rust in the magnetic layer, the electrical resistance of the magnetic layer increases, which tends to cause problems due to charging during use.

The metal magnetic powder preferably has an acicular shape when used in a magnetic disk.

In addition, as γ-Fe2O3 powder, α-Fe OOH
(geothite) is dehydrated at 400℃ or higher to form a-F
e203 and reduced at 350℃ or higher in H2 gas to F
It is preferable to use a material prepared by oxidizing e3O4 at a temperature of 250° C. or lower.

As the cobalt-coated iron oxide powder, one in which Co2+ is diffused in a very thin layer within several tens of λ from the surface of γ-Fe203 particles may be used.

In addition, the magnetic powder has an average major axis diameter of 2μI or less, especially 0.0
It is preferable that the powder is made of acicular magnetic powder having shape anisotropy of 1 to 1 .mu.m and an axial ratio expressed by average major axis diameter/average minor axis diameter of 2 to 20.

Those having an axial ratio of less than 2 are unfavorable in terms of electric characteristics when used as a medium.

As the binder, radiation curable resin, thermosetting resin, reactive resin, thermoplastic resin, etc. are used.

When using radiation curable resin, specific examples include:
Acrylic double bonds such as acrylic acid, methacrylic acid or their ester compounds, allyl double bonds such as diallyl phthalate, maleic acid, maleic acid derivatives, etc., which have unsaturated double bonds that exhibit radical polymerizability. It is a resin in which a group such as an unsaturated bond that can be crosslinked or polymerized and dried by radiation irradiation is contained or introduced into the molecule of a thermoplastic resin. In addition, any compound having an unsaturated double bond that undergoes cross-linking polymerization upon radiation irradiation may 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. The amount is 1 to 40 mol %, preferably 10 to 30 mol % in the acid component in terms of radiation curability and the like.

Examples of thermoplastic resins that can be modified into radiation-curable resins include the following.

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-terminated OH side chain alkyl group copolymer, such as VROH and VYNC manufactured by UCC.

VYEGX,VERR,VYES,VMCA,VAGH
, UCARMAG520, UCARMAG528, etc.

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, and the like are suitable.

Other resins that can be used for radiation sensitivity modification include polyfunctional polyester resins, polyether ester resins, polyvinylpyrrolidone resins, and derivatives (pvp
Also effective are acrylic resins containing at least one of olefin copolymers), polyamide resins, polyimide resins, phenol resins, spiroacetal resins, hydroxyl group-containing acrylic esters, and methacrylic esters as polymerization components.

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 particularly advantageous due to its abrasion resistance and good adhesion to substrates such as PET films.

Examples of urethane compounds include isocyanates such as 2.4-toluene diisocyanate, 2.6-toluene diisocyanate, 1.3-xylene diisocyanate, 1.4-xylene diisocyanate, 1.5-naphthalene diisocyanate, and m-ph22. Diisocyanate, p-phenyl diisocyanate, 3.3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4.4'-diphenylmethane diisocyanate, 3.3'-dimethylbiphenylene diisocyanate, 4,4'-biphenylene diisocyanate , hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, desmodur, desmodur N, etc.;
Polyhydric alcohols such as ethylene gelicol, diethylene glycol, glycerin, trimethylolpropane, 1,4-butanediol, 1,6-hexanediol, pentaerythritol, sorbitol, neopentyl glycol, 1,4-cyclohexane dimetatool and saturated polybasic acids such as phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, and sebacic acid), linear saturated polyethers (polyethylene glycol, polypropylene glycol, polytetramethylene glycol) ), polyurethane elastomers and prepolymers made of condensation products of various polyesters such as caprolactam, hydroxyl-containing acrylic 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 OH, Cool, etc. as a polar group at the end.

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

The combined use of these urethane elastomers with the above-mentioned acrylo-modified vinyl chloride copolymer 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 preferred systems for thermoplastic Nylastor and its prepolymers include styrene-butadiene rubber, chlorinated rubber, acrylic rubber, isoprene rubber, and its cyclized product (ClR701 manufactured by Nippon Synthetic Rubber Co., Ltd.), epoxy-modified rubber, internal Elastomers such as plasticized 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.

Thermoplastic resins have a softening temperature of 150°C or less, an average molecular weight of to, ooo ~ 200,000, and a degree of polymerization of about 200 to 2,000, such as vinyl chloride-vinyl acetate copolymers (including those with carboxylic acid introduced). (including vinyl chloride-vinyl acetate-vinyl alcohol copolymers and those with carboxylic acid introduced)
, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, acrylic ester-styrene copolymer, methacrylic ester -Acrylonitrile copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, urethane elastomer, nylon-silicon resin, nitrocellulose-polyamide resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer Coalescence, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer, polyester resin, chloro Vinyl ether-acrylic acid ester copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof are used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating solution, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Moreover, among these resins, those that do not soften or melt until the resin is thermally decomposed are preferable.

Specifically, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, butyral resin, formal resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, polyamide resin, epoxy-polyamide resin, saturated polyester resin. , mixtures of polycondensation resins such as urea formaldehyde resins or high molecular weight polyester resins and isocyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, low molecular weight glycols/high molecular weights Diol/triphenylmethane triisocyanate mixtures, mixtures of the above condensation resins and crosslinking agents such as isocyanate compounds, vinyl chloride-vinyl acetate (including carboxylic acid-containing), vinyl chloride-vinyl alcohol-
Mixtures of vinyl copolymer resins such as vinyl acetate (including those containing carboxylic acids), vinyl chloride-vinylidene chloride, vinyl chloride-acrylonitrile, vinyl butyral, vinyl formal, etc., and crosslinking agents, fibers such as nitrocellulose, cellulose acetobutyrate, etc. mixture of base resin and crosslinking agent,
Mixtures of synthetic rubber systems such as butadiene-acrylonitrile and crosslinking agents, as well as mixtures thereof, are preferred.

To cure such a thermosetting resin, it is generally necessary to heat it in a heating oven at 50 to 80°C for 6 to 100 hours.

Among the above-mentioned binders, it is particularly preferable to include a radiation-curable resin in order to improve durability and adhesive strength with the magnetic layer.

When such a radiation-curable resin is used as a binder, active energy rays used for crosslinking the magnetic coating include electron beams using an electron beam accelerator, γ-rays using 0060 as a source, Sr. β-ray with 90 as a radiation source, X
X-rays using a ray generator as a ray source are used.

In particular, as an irradiation source, it is advantageous to use an electron beam from an electron beam accelerator from the viewpoint of controlling the absorbed dose, introducing it into a manufacturing process line, and blocking ionizing radiation.

The characteristics of the electron beam used when curing magnetic coatings are as follows:
From the viewpoint of penetrating power, it is convenient to use an electron beam accelerator with an accelerating voltage of 100 to 750 KV, preferably 150 to 300 KV, and to irradiate at an absorbed dose of 0.5 to 20 megarads.

In addition, during radiation crosslinking, it is important to irradiate the recording medium with radiation in an inert gas flow such as H2 gas or He gas. Because it is very porous, irradiating it with radiation in the air will cause the radicals generated in the polymer due to the influence of 03 etc. generated by radiation irradiation to effectively cause the crosslinking reaction when the binder component is crosslinked. to prevent it from working.

The effect is that not only the surface of the magnetic layer is porous, but also the inside of the coating film is affected by binder crosslinking inhibition.

Therefore, it is important to maintain the atmosphere in the area where the active energy rays are irradiated to be an inert gas atmosphere such as N2, He, CO2, etc. with a maximum oxygen concentration of 1%.

In addition, when using ultraviolet rays when curing the magnetic coating film,
A photopolymerizable sensitizer is added to the binder containing the radiation-curable resin as described above.

The photopolymerization sensitizer may be a conventionally known one, such as benzoin type sensitizers such as benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin, α-chlordeoxybenzoin, benzophenone, acetophenone, bisdialkylaminobenzophenone, etc. Examples include ketones, quinones such as acedraquinone and phenanthraquinone, and sulfides such as benzyl disulfide and tetramethylthiuram monosulfide. The photopolymerization sensitizer is desirably in a range of 0.1 to 10% by weight based on the solid content of the resin.

For ultraviolet irradiation, for example, an ultraviolet light bulb such as a xenon discharge tube or a hydrogen discharge tube may be used.

Note that the weight ratio of the binder and the magnetic powder is approximately 1:1 to 1:9.

Further, the thickness of the &fi layer is approximately 0.1 to 15 μm.

The magnetic layer may contain an inorganic pigment.

Examples of inorganic pigments include 1) electrically conductive carbon black, graphite, and graphitized carbon black, and 2) S i 02 and T i 0 as g-fillers.
2, A1203, Cr203, SiC, CaO1
Ca CO3, zinc oxide, goethite, γ-Fe203
．． Examples include talc, kaolin, CaSO4, boron nitride, graphite fluoride, molybdenum disulfide, and ZnS.

In addition, the following fine particle pigments (aerosil type, colloidal type): 5i02, A1203, Ti
O2, ZrO2, Cr203, Y203, CeO2, Fe304,
Fe203, ZrSiO4, Sb205.5n02, etc. are also used. These fine particle pigments are, for example, 5i02
In the case of ■ Ultrafine particle colloidal solution of silicic anhydride (Snowtex, water-based, methanol silica sol, etc., Nissan Chemical),
■Ultrafine particulate anhydrous silica (standard product 100 people) (Aerosil, Nippon Aerosil Co., Ltd.) manufactured by combustion of purified silicon tetrachloride is included. Also, the above ■
An ultrafine particle colloidal solution of 2, ultrafine aluminum oxide produced by the same gas phase method as in 1, titanium oxide, and the above-mentioned fine particle pigments may be used. Regarding 1), the amount of such inorganic pigment used is 100 weight ff of magnetic powder.
1 to 30 parts by weight for 1 part, and 1 to 30 parts by weight for 2)
30 parts by weight is appropriate; if the amount is too large,
The drawback is that the paint film becomes brittle and dropouts occur more frequently.

Regarding the diameter of the inorganic pigment, 1) is 0.1μ.
I or less, more preferably 0.05 μm or less, and regarding 2), 0.7 μI or less, more preferably 0.5 μm or less.

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

There are no particular restrictions on the solvent, but it is appropriately selected in consideration of the solubility and compatibility of the binder.

For example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, esters such as ethyl formate, ethyl acetate, and butyl acetate, alcohols such as methanol, ethanol, isopropanol, butanol, and aromas such as toluene, xylene, and ethylhenzene. group hydrocarbons, ethers such as isopropyl ether, engineered ethyl ether, dioxane, tetrahydrofuran,
Furfural and other furans are used as a single solvent or a mixed solvent thereof.

These solvents are 10 to 10,000w to the binder.
t%, especially 100 to 5000 wt%.

A lubricant is used as an additive in the magnetic layer and/or a top coat material for the magnetic layer.

Among various known lubricants, fatty acids and/or fatty acid esters are preferably used as the lubricant. Examples of fatty acids include fatty acids with 8 or more carbon atoms (RC
OOH, R is an alkyl group having 7 or more carbon atoms), and among them, unsaturated fatty acids such as oleic acid, elaidic acid, linoleic acid, linuric acid, and stearolic acid are suitable.
In addition, fatty acid esters include monobasic unsaturated or saturated fatty acids having 10 to 22 carbon atoms and 3 to 22 carbon atoms.
Fatty acid esters consisting of m saturated or unsaturated alcohols are preferred.

The aliphatic chain of the fatty acid and/or alcohol in the ester may be saturated or unsaturated, and may be of various types, such as n-linked or i-linked.

Note that two or more of these may be used in combination.

In addition, as other lubricants, metal soaps made of alkali metals or alkaline earth metals of the fatty acids, silicone oils, fluorine oils, paraffin, liquid paraffin, surfactants, etc. can also be used.

The total amount of lubricant used is 2 parts by weight per 100 parts by weight of magnetic powder.
0 parts by weight or less, particularly 0.1 to 15 parts by weight.

To manufacture the magnetic recording medium of the present invention, the following manufacturing method may be followed.

FIGS. 1 to 9 each show an embodiment of the method for manufacturing a magnetic recording medium of the present invention.

In FIG. 1, a long film-like non-magnetic support 2 pulled out from an unwinding roll 1 is coated with a gravure coat, an air doctor coat, a blade coat, an air knife coat, a squeeze coat, and a reverse roll. The magnetic paint 3 is applied in a film form by various coating methods such as coating, transfer roll coating, and spray coating.

In addition, in FIG. 1, a roll 41°45.49 of reverse roll coating is shown as an example of these coating means.

In addition, in the figure, the magnetic paint 3 is supplied to each roll from a nozzle 7, and a doctor blade 8 is arranged close to the roll 41.

The non-magnetic support 2 may be made of various resins as described above.

The magnetic paint 3 contains the aforementioned acicular magnetic powder, binder, solvent, and the like.

After such a coating step, the next step is usually random assimilation of the magnetic paint 3 deposited on the non-magnetic support.

Note that before this orientation, various treatments such as smoothing the wet film surface and controlling the coating film may be performed, but it is more convenient to avoid treatments that promote natural orientation in the longitudinal direction of the support as much as possible. It is.

The orientation in the present invention is to make the naturally oriented magnetic powder as unoriented as possible by means of coating means or the like as described above.

In the present invention, a magnet is used as a random orientation means, and the magnets are loop-shaped magnets 5 and 5'.

The magnet used is placed against the support surface as shown in Figure 3.
Either above or below, or both above and below the support surface as shown in FIGS. 4 and 7.

In such a magnet 5.5', as shown in FIGS. 2 to 9, a plurality of unit magnets 51.51' are arranged so as to alternately have different polarities on the surface facing the support 2, Constructed in a connected manner. Then, a magnet 5.5' having a loop shape is formed, which is composed of two substantially straight portions having a width equal to or larger than the width of the support and two substantially semicircular curved portions connected thereto.

Note that it is advantageous to use unit magnets 51, 51' having the same magnetic field strength in terms of design.

Then, the maximum engineered Nerky product (B
H) Wax is usually about 0.1 to 40 MGOe.

Such a magnet 5.5' is arranged so that the alternate polarity arrangement surface, which is a loop-shaped plane, is almost parallel to the plane of the two supports, and the direction in which the support moves and the linear part of the loop-shaped part are almost perpendicular to each other. will be installed. This angle is usually about 90"±10°, but it is preferable to make it as close to 90° as possible.

Furthermore, the magnets 5.5' are moved approximately in an annular manner so that the unit magnets 51,51' maintain the loop shape and sequentially and continuously move in one direction to adjacent unit magnets.

As a means for the annular movement of the m-position magnets, for example, a belt conveyor 9.9' that moves in an annular manner may be used as a base material, and a plurality of unit magnets 51, 51' may be arranged at predetermined positions on this conveyor.

In addition, any material that can form an endless loop, such as a chain, can be used without particular limitations.

The moving speed of such a unit magnet (speed of the belt conveyor) usually differs depending on the size of the unit magnet 51, 51' and the conveyance speed of the support 2, and the number of changes of the magnetic pole per support IIm is set as a unit. 5 to 5 when displayed as
000 times/l, preferably 100 to 2000 times/m.

If this value is less than 5 times/m, non-uniform orientation will occur in the longitudinal direction of the support.

Moreover, when the number of times/Il exceeds 5,000 times, the magnetic field reversal becomes too large and the surface condition becomes rough.

In the present invention, it is preferable that the positional relationship between the magnet 5.5' and the support 2 coated with the magnetic paint 3 is regulated so as to satisfy the following relational expression.

That is, Figure 2 and ? As shown in Figure S3, above or below the support 2 (in this figure, it is exemplified below)
When used for either one of the following, the length of the straight part of the magnet 5 (in the same direction as the width direction of the support 2) is 1, and the facing distance between the two straight parts of the magnet 5 is 12. If the width of the support 2 is Ito, and the gap distance between the support 2 and the ifi stone 5 is g, then 21≧
t, orto, IL2≧0. IJZO.

It is preferable to satisfy the condition of 822 mm.

Further, as shown in FIGS. 4 to 9, when magnets 5.5' are used both above and below the support 2, one magnet 5 satisfies the above relational expression, and the other The length of the straight part of the magnet 5' (in the same direction as the width direction of the support 2) is 10, and the facing distance between the two straight parts of the magnet 5' is 22.
', and when the gap distance between the support 2 and the magnet 5' is g', x, ', x2', and g' are the aforementioned fll, respectively.
, x2 and g, but the range equivalent to the range mentioned above, i.e., 21'≧i
, oxo, x□□≧0.1fiQ, and g'≧2mm, they do not necessarily have to be equal.

It does not matter which one of the magnets 5 and 5' is placed upward.

The annular motion directions of the unit magnets 51 and 51' constituting the magnets 5 and 5' are the same direction (Figs.
(Fig. 6) or may be in opposite directions (Figs. 7 to 9).

The reason why Ql and 21' are set as above is to make the degree of orientation uniform in the width direction of the support, and if it is out of the above range, the degree of orientation will be different at both ends and the center in the width direction of the support. A tendency will occur.

The reason why 22 and 2□' are set as above is due to the number of changes of the IIfi pole per 1 m of support length and the conveyance speed, but if the time interval affected by magnetic field reversal is too short, the surface This is because there is a tendency for the roughness to deteriorate.

The reason why g and g' are set as described above is that if the gap g is too small, the rate of change in the applied magnetic field intensity will increase due to so-called flapping of the support.

It should be noted that good results can be obtained within this range of 2 □ with a normal conveyance speed of the support 2 of about 5 to 500 m/min and a viscosity of a normal magnetic paint.

Furthermore, the length fL of the magnet 5.5' in the thickness direction of the support 2
3.13' generally increases the strength of the magnetic field that can be applied as the length increases, so the gap between the support and the magnet can be increased and the risk of the coated material coming into contact with the magnet can be avoided. On the other hand, if it is too long, the magnet unit will become large and heavy, resulting in poor operability.

For this reason, it is preferable from experience that these lengths 23 and 23' are each 5 to 50 mm.

The magnetic paint 3 has 5 to 30
A magnetic field of 0G, usually about 10 to 200G, is uniformly applied.

Note that the width 2o of the support may be about 10 to 500 cm.

A plurality of such magnets 5,5' may be arranged in the transport direction of the support 2. In this case, each opposing magnet may or may not be the same.

Further, with respect to the magnets 5.5', only one of the magnets may be placed side by side so as to be opposed above or below the support.

After coating, the randomly oriented magnetic paint 3 as described above is usually heated with hot air provided inside a drying oven 6 or the like.
It is dried and solidified using a known drying means such as a far-infrared lamp or an electric heater. Furthermore, when a radiation-curable compound as described below is used as the binder, various radiation irradiation devices are additionally used.

After solidifying the magnetic layer in this manner, surface smoothing treatment is performed as necessary.

Next, it is punched into a predetermined disk shape using a punching press or the like, and further processed to produce a medium.

The magnetic paint 3 for the disk-shaped magnetic recording medium manufactured in this way contains acicular magnetic powder, a binder, various additives as necessary, and usually a solvent.

The viscosity of magnetic paint is 5 to 100 oo C at the coating stage.
It is about p.

Note that the support may be provided with a base layer or a base treatment.

The magnetic layer may be provided on one side or both sides of the support.

When provided on only one side, a back coat layer may be provided, and a top coat layer may be provided on the magnetic layer.

■Specific Effects of the Invention In practical use, the magnetic recording medium of the present invention can be used to write and write information into the magnetic layer of a magnetic disk by sliding a magnetic head in the circumferential direction of the disk while rotating the disk-shaped medium. It performs regeneration.

According to the present invention, a magnet for random orientation is connected to a support body such that a large number of magnets have opposite polarities alternately on the surface facing the support body, and two magnets having a width larger than the width of the support body are connected. It has a loop shape consisting of an almost straight straight part and two curved parts connected to this straight part, and the alternately different polarity arrangement surface of the loop shape plane is almost parallel to the support plane, and the support progresses. The unit magnets are installed so that the direction and the linear portion of the loop shape are substantially perpendicular to each other, and the unit magnets are moved in one direction within the loop shape to perform random orientation.

Therefore, the medium produced in this manner has uniform modulation characteristics and good values.

(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 1 (&fi-based paint 1) Cobalt-coated γ-Fe203 (long axis 0.5 μl, short axis 0.5 μl, Hc 600 0e) 100 parts by weight carbon black (for antistatic use, Mitsubishi Carbon Black MA-600 ) 10 parts by weight α-A
i2o3 powder (0.5μ granules) 5 parts by weight Dispersant (purified soybean lecithin) 2 parts by weight Solvent (methyl ethyl ketone/toluene 50150) 100 parts by weight The above composition was mixed in a ball mill for 3 hours, and acicular magnetic iron oxide was mixed. It was thoroughly dispersed with a dispersant.

Next, as a binder, vinyl chloride-vinyl acetate-vinyl alcohol copolymer (
Contains 1% maleic acid: MW40,000) 10 parts by weight (solid content equivalent)
, Acrylic double bond-introduced vinyl chloride-vinyl acetate-vinyl alcohol copolymer (containing maleic acid; MW 25,000) 10 parts by weight (solid content equivalent), Acrylic double bond-introduced polyether urethane elastomer (MW 40,000) 11 parts by weight (in terms of solid content), 3 parts by weight of pentaerythritol triacrylate, 200 parts by weight of a solvent (MEK/toluene, 50150), 5 parts by weight of stearic acid, and 5 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.

The magnetic coating material thus obtained was used as a raw material for the magnetic layer of the medium, and the following magnetic recording medium was manufactured using the manufacturing line shown in FIG.

A 75 mm thick polyester (PET) film with a width of 300 mm was used as the support, and the conveyance speed was 10 mm.
The speed was set to 0 m/min.

The coating was applied by reverse roll coating.

Next, random orientation was performed using magnet 5.

Orientation conditions, i.e. magnet size! Random orientation was performed by varying the positional relationship between the f1 stone and the support as described below.

1 1.3 0.3 10 152
1.0 0.3 5 103 (comparison) -m-
-No magnet 4 1.2 0.05 5 1
55 1.2 0.5 10
156 1.2 0.1 1
0 157 1.2 0.5
50 58 1.2
0.5 5 20 As shown in FIG. 4, as random orientation No. 9, magnets with random orientation No. 001 were installed above and below the support so that g = 15 mm and g' = 15 mm, respectively. ,
Both magnets were moved in a loop in the same direction.

In addition, as shown in Fig. 7, with random orientation No. 10, magnets with random orientation No. 1 are placed above and below the support at g = 10 ma + and g' = 10 mm, respectively.
The two opposing magnets were placed in a loop motion in opposite directions.

The unit magnet 51 is 15 x 20"ms, and the magnetic force of each unit magnet 51 has a maximum energy of 81 (BH
) lax 4. It was named OMGOe.

The number of times the magnetic pole changes per meter of longitudinal length of the support is 1
000 times.

Next, it was passed through a drying oven to perform a surface smoothing treatment, and then passed through a radiation irradiation device to dry and harden the coating film.

For curing, an electron curtain type electron beam accelerator manufactured by ESI was used at an accelerating voltage of 150 KeV.
, under the conditions of electrode current 20 mA and absorbed dose 5 Mrad.
The coating film was cured by irradiating it with an electron beam under 2 atmospheres.

Note that the film thickness was measured using an electronic micrometer.

These coating films were formed on both sides of the film, and both sides were coated.

After the coating film was cured in this manner, it was punched out into a 3.5n disk shape to produce a magnetic recording medium sample. The thickness of the coating film (IF layer) after curing was 2-.

φr min /φr +nax, (φr/φ+
5) lIin/(φr/φm) max, and the average squareness ratio φr/φl and the value obtained by dividing the average squareness ratio in the circumferential direction by the average squareness ratio in the radial direction (φr/φtn) R/(
φr/φm)a was measured, and the following characteristics were also measured.

(1) Measure the average amplitude measured at the maximum amplitude of one round of the modulation track and the average amplitude measured at the minimum amplitude of the track. When the former is A and the latter is B, the modulation is calculated by the following equation.

A+B Modulation was measured at 2f on the innermost track.

In the embodiment of the present invention, three disks are punched out in the width direction of the support. Therefore, the modulation was measured for the disk media punched from both ends and the center, and these values were defined as Ml (measured for the punched parts at both ends) and M2 (measured for the center punched part), and averaged over a total of 10 samples. .

(2) Resolution measurement NEC (1M byte) MFD drive FD-1035
1f and 2f are recorded and reproduced on the innermost track using the optimum recording current.

Then, each average signal amplitude was measured, and the resolution was determined from the following equation.

1f average amplitude The results are shown in Table 1.

The effects of the present invention are clear from the results shown in Table 1.

That is, the inventive sample shows a very small modulation of less than 4%. Moreover, this modulation shows good values both at the ends and at the center in the width direction of the support.

Furthermore, the resolution shows a good value of 0.7 or more. However, if this resolution exceeds 0.9, a shoulder peak will appear in the signal, a saddle will appear in the differential curve, and signal errors will tend to occur.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of the manufacturing process of the present invention. FIGS. 2 and 3 are a plan view and a front view, respectively, showing the relationship between the magnet and the support in the present invention. FIG. 4 shows two magnets and a support according to the present invention. FIGS. 5 and 6 are a plan view and a bottom view of FIG. 4, respectively. FIG. 7 is a front view showing a modification of FIG. 4 in the present invention. 8 and 9 are a top view and a bottom view of FIG. 7, respectively. Explanation of symbols 1-@Drawing roll, 2-Nonmagnetic support, 3-Magnetic paint, 41.45.49-Roll, 5.5'-Magnet, 51.51'-Unit magnet, 6-Drying oven Applicant TDC Co., Ltd. Q FIG, 2 FIG, 4 FIG, 6 FIG, 9

Claims (9)

[Claims] (1) In a disk-shaped magnetic recording medium having a magnetic layer containing magnetic powder and a binder on a non-magnetic support,
A magnetic recording medium characterized in that, when the residual magnetic flux density φr in the track circumferential direction of the medium is measured, the value obtained by dividing the minimum value of φr by the maximum value is 0.95 to 1. (2) The magnetic recording medium according to claim 1, wherein a value obtained by dividing the minimum value of the squareness ratio φr/φm in the track circumferential direction by the maximum value is 0.95 to 1. (3) The average squareness ratio φr/φm in the track circumferential direction is 0.
Claim 1 or 2 which is between 55 and 0.65.
The magnetic recording medium described in section. (4) A value obtained by dividing the average squareness ratio in the circumferential direction of the track by the average squareness ratio in the radial direction is 0.97 to 1.03. magnetic recording medium. (5) The magnetic recording medium according to any one of claims 1 to 4, wherein the support is flexible. (6) Apply a magnetic paint containing magnetic powder and a binder onto a long non-magnetic support, apply a magnetic field with a magnet facing the support, dry it, and then form it into a disk shape. In the method for manufacturing a magnetic recording medium by punching, the magnet has a plurality of unit magnets connected to each other so as to face the support body so as to alternately have different polarities, thereby forming two substantially straight straight portions having a width equal to or larger than the width of the support body. It has a loop shape consisting of two curved parts connected to a straight part, and the alternately different polarity arrangement surface of the loop shape plane is approximately parallel to the support plane, and the straight part of the loop shape is parallel to the support traveling direction. When the residual magnetic flux density φr in the circumferential direction of the track of the medium is measured by moving the unit magnet in one direction within the loop shape, the minimum value of φr is divided by the maximum value. is 0.9
5 to 1. A method for manufacturing a magnetic recording medium, characterized in that: (7) The method for manufacturing a magnetic recording medium according to claim 6, wherein l_1≧1.0l_0, where the length of the loop-shaped linear portion of the magnet is l_1 and the length of the support width is l_0. . (8) A magnetic paint containing magnetic powder and a binder is applied onto a long non-magnetic support, a magnetic field is applied using a magnet facing the support, it is dried, and then it is shaped into a disk. In the method for producing a punched magnetic recording medium, the magnets are installed above and below a support, and each magnet connects a number of unit magnets facing the support so that the magnets alternately have different polarities. It has a loop shape consisting of two almost straight straight parts that are larger than the width of the support and two curved parts connected to the straight parts, and the alternately different polarity arrangement surface of the loop shape plane is approximately the same as the support plane. The magnets are installed parallel to each other so that the direction of movement of the support and the linear part of the loop shape are approximately at right angles, and each unit magnet of each magnet is moved in one direction within the loop shape, and the upper and lower unit magnets are Magnetism characterized in that, when the movement directions are in the same direction and the residual magnetic flux density φr in the circumferential direction of the track of the medium is measured, the value obtained by dividing the minimum value of φr by the maximum value is 0.95 to 1. A method for manufacturing a recording medium. (9) A magnetic paint containing magnetic powder and a binder is applied onto a long non-magnetic support, a magnetic field is applied using a magnet facing the support, it is dried, and then it is shaped into a disk. In the method for manufacturing a punched magnetic recording medium, the magnets are placed above and below a support, and each magnet is connected to the support so that a large number of unit magnets alternately have different polarities, facing the support. It has a loop shape consisting of two almost straight straight parts that are larger than the width of the support and two curved parts connected to the straight parts, and the alternately different polarity arrangement surface of the loop shape plane is approximately the same as the support plane. The magnets are installed parallel to each other so that the direction of movement of the support and the linear part of the loop shape are approximately at right angles, and each unit magnet of each magnet is moved in one direction within the loop shape, and the upper and lower unit magnets are Magnetism characterized in that when the movement direction is opposite and the residual magnetic flux density φr in the circumferential direction of the track of the medium is measured, the value obtained by dividing the minimum value of φr by the maximum value is 0.95 to 1. A method for manufacturing a recording medium.