JPS5952430A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve a reproduction output in a short-wavelength range and therefore realize short-wavelength, high-density recording, by limiting a square ratio measured in every direction of a recording medium to a specific range. CONSTITUTION:A DC magnetic field with specific intensity is impressed during the manufacture of the recording medium at right angles to the film surface of an undried magnetic film to obtain a specific 0.4-0.5 square ratio range. A magnetic paint consisting primarily of ferromagnetic material fine powder and a binder is applied over a nonmagnetic base and when the film is not dried and still fluid, the DC magnetic field perpendicular to the film is impressed through a couple of magnets for orientation arranged on both upper and lower surface sides of the base in advance to orient the internal ferromagnetic material fine powder at right angles to the film surface and the drying is accelerated by heating to provide a magnetic layer. The intensity of the impressed magnetic field is different depending upon a coating speed, paint viscosity, the kind of the fine powder of ferromagnetic material, etc., and preferably 1-4K gauss.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a magnetic recording medium particularly suitable for high density recording.

In recent years, with the development of electronic devices such as audio, video, and computers, the magnetic recording media such as magnetic tapes and magnetic flexible disks that record and reproduce the output of these devices are required to record at short wavelengths of several micrometers or less. There is a strong demand for high-density recording that provides high playback output. In general, a magnetic recording medium consists of a nonmagnetic support made of a polymeric material such as polyester, and the main components are ferromagnetic fine powder and a polymeric binder. However, when this magnetic layer is in an undried state containing a solvent, a magnetic field is applied in the in-plane direction of the magnetic layer to align the grain direction of the ferromagnetic fine powder.This orientation causes the magnetic head to It is well known that this orientation improves the playback output when the recording wavelength becomes shorter.
Its effectiveness tends to decrease. In addition, it is possible to improve the reproduction output by reducing self-demagnetization by reducing the magnetic layer, or by increasing the coercive force of the magnetic R't. Even if the temperature is too high, it is possible to effectively record on such a magnetic layer with high coercive force.
The reality is that a magnetic head capable of reproducing has not yet been developed.

The present invention has been made in order to solve the above-mentioned drawbacks, and an object of the present invention is to provide a magnetic recording medium that can obtain a particularly large reproduction output in short wavelength recording of several microns or less.

As a result of intensive research to achieve this objective, the inventor found that
In a magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic fine powder and a binder is provided on a non-magnetic support, a magnetic field is applied in any direction of the medium (vertical, horizontal, height direction, etc.). squareness ratio (remanent magnetization ratio Mr/Ms corrected by demagnetizing field)
Both a and (in the divalent value, Mr represents the residual magnetic flux density and Ms represents the saturation magnetic flux 'IB degree) are from 0.4 to 0.
It has been found that when the ratio is between 5 and 5, a particularly large reproduction output can be obtained in short wavelength high-density recording of several microns or less. The magnetic head used in this case preferably has a narrow gap of, for example, about 1 μm or less. The present invention has been achieved based on this knowledge.

As described above, any recording medium of the present invention can be used as long as the squareness ratio measured in all directions of the recording medium is within the range of 0.4 to 0.5. 0.
If it is less than 4, the residual magnetization component in the direction perpendicular to the surface of the magnetic recording medium cannot be used effectively, and therefore a large reproduction output cannot be obtained in short wavelength 1-tele density recording of several microns or less. Furthermore, if the squareness ratio in one direction, for example, the direction parallel to the surface of the recording medium, exceeds 0.5, the squareness ratio in the direction perpendicular to the plane becomes 0.4 to 11, and the Similarly, it is not possible to obtain large playback output in high-density recording. However, as in the present invention, the squareness ratio is set to 0.4.
By specifying flu [13] of ~0.5, residual magnetization components in all directions can be used most effectively, so the intended purpose can be easily achieved. It should be noted that conventional magnetic recording media have a squareness ratio of 0.8 or more, for example, in either the flat direction or perpendicular direction to the surface for the purpose of reproducing output in direction 1.
Since t%<b, this point differs from the present invention.

The material used for the recording medium of the present invention may be the same as conventional materials, but in order to obtain a predetermined squareness ratio, the magnetic coating film of undried smoke is applied to the film surface at the time of manufacturing the recording medium, as described later. A perpendicular DC magnetic field of a specific strength is applied.

Therefore, in order to produce a magnetic recording medium having a specific squareness ratio according to the present invention, a magnetic paint mainly composed of ferromagnetic fine powder and a binder is coated on a non-magnetic support, and the paint film is not yet dry. While the powder is still fluid, a direct current magnetic field perpendicular to the coating 11'A is applied to the coating 11'A by passing it between a pair of orientation magnets placed on both the upper and lower sides of the support to separate the fine ferromagnetic powder inside. The magnetic layer may be formed by oriented perpendicularly to the coating surface and then heating to accelerate drying. The applied magnetic field strength depends on the coating speed,
Although it varies slightly depending on the viscosity of the paint, the type of fine ferromagnetic powder, etc., Gauss is preferably 1 to 4. As described above, the thinner the magnetic layer, the less self-demagnetization and the higher the coercive force, which is preferable for high-density recording. Specifically, the appropriate thickness is about 1 to 5 μm.

The ferromagnetic fine powder used in the present invention has a coercive force of 5
Although those with a diameter of 00 to 1000 oersteds are suitable for short wavelength recording of several microns or less, even those with a normal diameter of 250 to 400 oersteds can be made suitable for short wavelength recording according to the present invention.

Further, the average particle size of this fine powder is not particularly limited, but is 0.
A range of 3 to 0.5 μm is preferred. The shape of the fine powder is not particularly limited either, and may be any shape such as spherical or acicular.

As the ferromagnetic fine powder that can be used in the present invention, γ-Fe2
0g, Co-containing r-Fe203tFe3O4#
CrO2y ferromagnetic alloy fine powder, iron nitride Φ1-shaped fine powder, C.

Contains F a B 04, etc.

As the binder that can be used in the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof can be used. As the thermoplastic resin, for example, vinyl chloride (vinyl chloride copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer, acrylic ester vinylidene chloride copolymer, acrylic) 1-acid stealth styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid:L sf/l/styrene copolymer, urethane elastomer, polyhinyl fluoride, chloride Vinylidene acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, styrene butadiene copolymer, polyester resin, amino resin, various synthetic rubber thermoplastic resins (butadiene, polyisoprene) , polyisoprene, styrene-butadiene copolymer, etc.) and mixtures thereof.Emulsions of these may also be used.

Thermosetting resins (such as resins or reactive resins include phenol-formalin-nojirac resin, phenol-formalin-resol resin, phenol-furfural resin, xylene-formaldehyde resin, urea resin, melamine resin, drying oil-modified resin) Alkyd resin, carbonic acid resin modified alkyd resin, maleic acid resin modified alkyd resin, unsaturated polyester resin, epoxy resin and curing agent (polyamine, acid anhydride, polyamide resin, etc.), terminal isocyanate polyester moisture curing resin, terminal isocyanate These include polyether moisture-curable resins, polyisocyanate prepolymers, 4rtj resins containing 4?lisocyanate prepolymers and active hydrogen, and mixtures thereof.Emulsions of these may also be used.

These binders may be used alone or in combination;
Other additives may be added. Ferromagnetic powder.

In addition to the above-mentioned inder and ferromagnetic powder, the magnetic layer contains additives such as a dispersant, a caustic lubricant, an abrasive H5 agent, and ft)'
A t4 inhibitor or the like may be added.

Dispersants include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, lylunic acid, and stearolic acid (1,1) having 12 to 18 carbon atoms. fatty acid (R1
C0OH, 'R1 is charcoal)) (number 11-17 alkyl or alkenyl,; 1li); 4% of alkali gold (L i I Na HK etc.) or alkaline earth metal (iVig, Ca, Ba) of the above fatty acids ); fluorine-containing compounds of the above-mentioned fatty acid esters; amides of the above-mentioned fatty acid Vj acids; polyalkylene oxide alkylphosphorus [esters]; lecithin; etc. are used. These dispersants are added in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder.

Carbon black, graphite,
Conductive fine powder such as carbon black Graftopo1; natural surfactants such as saponin; nonionic surfactants such as alkylene oxide, glycerin, and glycidol; higher alkylamines, quaternary ammonium salts, and xylidine. Cationic surfactants such as other heterocycles, phosphoniums, or sulfoniums; anionic surfactants containing acidic groups such as calzenic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric ester groups; amino acids, aminosulfonic acids Ampholytic activators such as BX, sulfuric acid or phosphoric acid esters of amino alcohols, etc. are used.

As lubricants, conductive fine powders such as carbon black, graphite, and carbon black graft 2 reamer; inorganic fine powders such as molybdenum disulfide, di(m+, and tungsten oxide); polyethylene, polypropylene, polyethylene vinyl chloride copolymer, polytetra Plastic fine powder such as fluoroethylene; α-olefin polymer; unsaturated aliphatic hydrocarbon that is liquid at room temperature (compound in which an n-olefin double bond is bonded to the terminal carbon, carbon composition: 20); carbon number 12-20 Fatty acid esters consisting of 5 monobasic fatty acids and monohydric alcohols with 3 to 12 carbon atoms are used.
I can do i4.

These 14 ft7 agents have a binder of 100yI(ll'(
It is added in an amount of 0.2 to 20 parts by weight.

As polishing materials, commonly used materials include fused alumina, silicon carbide, chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main components: corundum and magnetite), etc. . These polished BJJ particles have a Mohs hardness of 5 or more and an average particle size of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm. These training) 1
-” ;!1 is 05 to 10 weight R, parts of binder
It is added in an amount of 20 parts by weight.

Examples of the non-magnetic support used in the present invention include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate, paper, synthetic paper, laminated paper with alumina plastic, etc. .

Also, as a solvent, a ketone type such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone;
Alcohols such as methanol, ethanol, propatool, butanol; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate monoethyl ether; ether, glycol dimethyl ether,
Glycol ethers such as glycol monoethyl ether and dioxane; Tars (aromatic hydrocarbons) such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. Water can also be used.

The present invention will be explained in detail below using examples.

Example 1 The following components were subjected to crosstalk dispersion treatment for 15 hours using a ball mill.

Silicone oil 0.4μM
IBK (methyl isobutyl ketone) 32
．． opn toluene 32.
0//Cyclohexane 32.
0//Next, the following components were mixed and added to the above ball mill, and subjected to crosstalk dispersion treatment for 24 hours.

VAGH (manufactured by UCC) 10.8 parts per basket (1k combination of vinyl chloride and vinyl acetate) Casen black dispersion 10/'MIB
K 35. On toluene 35.0# Cyclohexane 35.0# The following components were added to the magnetic coating liquid prepared in h) 19 above and thoroughly stirred.

After the above treatment, the mixture was passed through a filter having an average particle size of 3μ to obtain a magnetic coating liquid.

The above magnetic coating liquid was applied to 4 sheets of polyethylene with a thickness of 75μ,
Each coating was applied onto a terephthalate film using a doctor blade so that the dry thickness was 3 μm. While the coating solution was still wet, it was passed through a DC magnetic field created by a permanent magnet. In this case, the magnetic field was passed between different magnetic poles for Example 1 and Comparative Example 3, and between the same magnetic poles for Comparative Example 1.2, and after changing the magnetic field strength to 5 with a yoke of Gauss or less. ,
Four types of magnetic recording media with different squareness ratios were prepared by drying with hot air at 100C. Next, each recording medium was punched out to a predetermined size, and the surface was polished to obtain a 5.25-inch magnetic flexible disk. Next, using a 5.25-inch flexible disk equipped with a link-type magnetic head with a gap of 1μ, the wavelengths of 8μ, 4μ, and 2μ were applied to the above sample.
Recording and playback were performed and the average playback output was measured. The results are shown in Table-10 Table-1 Note) *: Noise level is 18mv This corresponds to the vertical direction of the cube, and the two directions correspond to the height direction of the cube.

Example 2 Co-containing -Fe as magnetic powder! OB (He 620
Four types of magnetic biographies (:≠media) with different squareness ratios were created using the same magnetic paint as in Example 1, except that x/l/stead).Hereinafter, these recording media were used as Example 1 and Similarly, the squareness ratio and average reproduction output of the magnetic flexible disk were measured, and the results shown in Table 2 below were obtained.

Table 2 From the above results, the magnetic recording medium of the present invention whose squareness ratio measured in all directions of the recording medium is in the range of 0.4 to 0.5 is the ring type magnetic recording medium currently in practical use. It was found that the reproduction output of the head was improved at short wavelengths of 2 to 8 microns, and therefore it was found that high-density recording at short wavelengths of several microns or less is possible.

Procedural amendment dated January 1982, 1981, Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office, 2, Relationship with the Invention Name Case, Tokukin Deliverer, 1-3-6 Nakamagome, Ota-ku, Tokyo (674) Ricoh Co., Ltd. - Representative Takeshi Oyuzu 459th Representative Jinmu Contents of the amendment 1) "Amended" on page 3, line 6 of the specification replaced with "amended"
M1 corrects “No”.

that's all

Claims (1)

[Claims] 1. In a magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic fine powder and a binder is provided on a nonmagnetic support, the squareness ratio measured in all directions of the recording medium is 0.
A magnetic recording medium characterized in that the magnetic recording medium is between 4 and 0.5.