JPS5913001A - Production of surface treated ferromagnetic powder and magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain surface treated ferromagnetic powder having good dispersibility and to obtain a magnetic recording medium having good abrasion resistance by dispersing the ferromagnetic powder in an electrolyte soln. and treating the surface with a surface active agent having the electric charge reversed from the electric surface on the powder surface. CONSTITUTION:Ferromagnetic powder is dispersed by a ball mill or the like in a soln. of an electrolyte such as NaOH, Na3Po4 or the like, which electries the surface thereof negative or an electrolyte such as AlCl3, FeCl3 or the like, which electrifies the same positive. The concn. of the electrolyte soln. varies with the kinds of the electrolytes and the isoelectric points of the ferromagnetic powder to be used, and is set at such concn. at which the high pH lower than the isoelectric point of the ferromagnetic powder is attained in order to electrify the ferromagnetic powder positive and negative. After the dispersion, the ferromagnetic powder is treated with the electric charge reversed from the electric charge on the surface thereof, that is, cationic and anionic surface active agents when the surface of the powder is electrified negative and positive. The resulted surface treated ferromagnetic powder exhibits excellent dispersibility, and when the powder is contained in a magnetic powder, a magnetic recording medium having good abrasion resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing surface-treated ferromagnetic powder and a magnetic recording medium using the powder.

Conventionally, in magnetic recording media such as audio tapes and video tapes, ferromagnetic powder is bonded to vinyl chloride-vinyl acetate copolymer, cellulose resin, epoxy resin, polyurethane resin, etc. on a film-like support such as polyethylene terephthalate. It was mixed with a chemical agent and applied.

However, 2. The use of these binders alone or in combination tends to result in poor dispersibility of the ferromagnetic powder, and therefore the surface properties and wear resistance of conventional magnetic recording media are not sufficiently satisfactory. It wasn't something. Particularly in video tapes that require short-wavelength recording, poor dispersion of ferromagnetic powder in the magnetic layer causes deterioration of the 87H ratio and decrease in sensitivity, and such recording media also come into violent contact with the magnetic head during recording and reproduction. Therefore, with repeated use, the magnetic layer wears out, and the ferromagnetic powder in the layer tends to fall off, resulting in clogging of the magnetic head.

For this reason, it has been proposed to use various additives for the purpose of improving the dispersibility of ferromagnetic powder and improving the wear resistance. For example, ferromagnetic powders can be used without any special treatment;
-53402, 49-58804, 49-84
No. 405, No. 51-40904, No. 52-'7081
As described in each publication No. 1, a magnetic paint containing ferromagnetic powder and a sintering agent contains higher fatty acids, fatty acid amides, fatty acid esters, higher alcohols, metal soaps,
Magnetic recording media have been manufactured by coating a support with a magnetic paint containing sulfate esters of higher alcohols, polyethylene oxide, lecithin, etc.

However, by simply adding these additives at the time of manufacturing the magnetic paint, some effects are observed, but they are not necessarily sufficient, and it has been difficult to obtain magnetic recording media with VS properties. For example, the use of large amounts of these additives has the undesirable effect of reducing the mechanical strength of the magnetic layer. Furthermore, after the magnetic layer is formed, a so-called "blooming" phenomenon occurs in which the additive gradually oozes out, resulting in undesirable results in terms of storage stability.

Furthermore, the magnetic properties of the magnetic layer and the dispersibility of the ferromagnetic powder were not satisfactory.

Therefore, I decided not to use the "Blooming" main unit etc.
In order to improve the dispersibility of ferromagnetic powder, for example, a method has been proposed in which the surface of ferromagnetic powder is pretreated with a surfactant, as described in Japanese Patent Publication No. 57-1048. has been done.

According to the above publication, a lipophilic surfactant such as lecithin is added to an organic solvent such as methyl ethyl lactone or toluene to prepare an active agent solution, and the magnetic powder to be treated is added thereto. After being dispersed, it is filtered and air dried.
This method involves drying under reduced pressure to obtain a surface-treated ferromagnetic powder. Although this method does suppress the blooming phenomenon when used as a magnetic recording medium, it is said that the dispersibility of the ferromagnetic powder worsens. There was a problem.

Moreover, a satisfactory dispersion state could not be obtained by the conventional method of simply immersing ferromagnetic powder in a surfactant solution and dispersing it.

An object of the present invention is to provide a novel method for producing a surface-treated ferromagnetic powder that overcomes the above-mentioned drawbacks, and a novel magnetic recording medium using the powder.

Another object of the present invention is to provide a method for producing surface-treated ferromagnetic powder with good dispersibility.

Another object of the present invention is to provide a magnetic recording medium with good wear resistance and purity.

Furthermore, another object of the present invention is to provide a magnetic recording medium with good storage stability.

Furthermore, the first object of the decoy of the present invention is to provide a magnetic recording medium with a good 8/N ratio.

Furthermore, another object of the present invention is to provide a magnetic recording medium having high reproduction output.

The above-mentioned objects of the present invention are characterized in that the ferromagnetic powder is dispersed in an electrolyte solution and then treated with a surfactant having a charge opposite to that of the surface of the powder. and a magnetic layer containing a surface-treated magnetic powder produced by dispersing ferromagnetic powder in an electrolyte solution and then treating it with a 111 surfactant having an opposite charge to the surface of the powder. This was achieved by a magnetic recording medium, which is characterized by the following characteristics.

In the method for producing ferromagnetic powder according to the present invention 5
- There are two kinds of electrolytes to be used: those that charge the surface of the ferromagnetic powder negatively and those that charge the surface of the ferromagnetic powder positively.

KOH, Na3PO4, Hh4P@01, Ha4F40
H, Na1S103, Na48104, Na1W04,
K,PO,,K,P,O,,4P40**,K,81
0. , K4SiO4, WO2, etc., and examples of those that positively charge the surface of the ferromagnetic powder include Mu101.
, Fail,,'Fi11. etc. are listed. The concentration of the electrolyte solution varies depending on the type of electrolyte and the isoelectric point of the ferromagnetic powder used, but in order to positively charge the surface of the ferromagnetic powder, it must be lower than the isoelectric point of the ferromagnetic powder. Use an electrolyte solution with a concentration that gives a low pH, and in order to negatively charge the ferromagnetic powder and the final surface, use an electrolyte solution with a pH higher than the isoelectric point of the ferromagnetic powder. Use the solution concentration.

In the present invention, methods for dispersing the ferromagnetic powder in an electrolyte solution include methods using a ball mill, a sand grinder, a high-speed impeller disperser, a high-speed mixer, a homogenizer, and the like.

6- It is believed that by dispersing the ferromagnetic powder in an electrolyte solution, shearing force acts effectively on the agglomerated powder, thereby reducing lateral aggregation of the agglomerated ferromagnetic powder.

Although water alone is often sufficient as a solvent for the electrolyte solution according to the present invention, various hydrophilic organic solvents such as alcohol having 1 to 6 carbon atoms, ethanol,
Ketones with 3 to 5 carbon atoms such as ethoxyethanol, ethyleneglyfur, ethers such as tetrahydro7rane or dioxane, N-methylpyrrolidone,
A nitrogen-containing hydrophilic solvent such as dimethylformamide, dimethylacetamide, pyridine, etc. may be mixed in an amount of 50 parts by weight or less, preferably 20 parts by weight or less, per 100 parts by weight of water. The electrolyte solution is particularly preferably an aqueous electrolyte solution.

Any of the above may be used as the electrolyte according to the present invention, but when the ferromagnetic powder is a metal, if the surface of the powder is positively charged, rust may easily occur. is preferably negatively charged,
Further, when the ferromagnetic powder is a metal compound, the surface of the powder may be charged positively or negatively.

After dispersing the ferromagnetic powder in the electrolyte solution, the present invention
The ferromagnetic powder is treated with a surfactant that has an opposite charge to the surface of the ferromagnetic powder. In other words, if an electrolyte that negatively charges the ferromagnetic powder surface is first used, a surfactant with an opposite charge, that is, a cationic surfactant, is used, and an electrolyte that positively charges the ferromagnetic powder surface is first used. If used, anionic surfactants are used.

It was significantly inferior in terms of dispersibility.

Examples of cationic surfactants used in the present invention include quaternary ammonium salts, ammonium salts of higher alkyl amines, pyridine and other nitrogen-containing heterocyclic compounds and their ammonium salts, phosphonium salts, and sulfonium salts. Examples include various surfactants such as salts.

Examples of anionic activators include palmitin-sodium,
Calcanates such as sodium oleate and potassium laurate; carboxylates having an ether bond such as sodium cetyloxyacetate and sodium p-decylphenoxyacetate; sodium dodecylsulfonamide and potassium cetyl sulfonamide acetate, etc. Carboxylic acid salt having an amide bond; sodium lauryl aminoacetate,
Carbonated salts having an amino group such as decylaminopropionic acid; Carboxylate salts having an ester bond such as P-decyl alcohol phthalic acid monoester sodium salt; Natural alcohol sodium sulfate, lauryl alcohol Aliphatic alcohol-acid ester salts such as ammonium sulfate, nilauryl polyethylene glycol ether sodium sulfate, p-octylphenyl polyethylene glyco-
Polyethylene glycol ether sulfate such as 4N≦r# sodium; ester sulfate salt having an amide bond such as stearamide sodium ethanol sulfate, P-octylbenzamide sodium ethanol sulfate; sulfuric acid salts, such as sodium cetyl sulfonate and sodium p-decylbenzenesulfonate; acid m;
Sulfonic acid salts having a bitroxyl group such as monothorium β-hydroxydodecylsulfonate; sulfonate rII having an ester bond such as α-sulfostearic acid propylnistylsodium salt, sulfosuccinic acid 2-ethylhexyl ester sodium salt, etc. Salt; α-sulfonate having an amide bond such as butyramide sodium urinate; α-, sodium cyanocetylsulfonate? Sulfonates having a cyano group such as N-tetradecyltaurine sodium salt; Sulfonates having an ether bond such as β-dodecyloxyethylsulfone; laurylthiomethanesulfonic acid Sulfonic acid groups having a sulfide bond such as sodium; phosphate ester salts such as dodecyl alcohol phosphoric acid monoester disodium salt, decyl alcohol phosphoric acid diester monosodium salt, and the like.

The surfactant according to the present invention may be used in an amount of 0.05 to 59 parts by weight, particularly preferably 0.1 to 10 parts by weight, per 100 parts by weight of the ferromagnetic powder. Do you like it?・If the volume is less than 05, the effect will not be sufficient and the result will be 1.
．． ．． This is because if it exceeds 50 parts by weight, emulsification tends to occur, which is not preferable. .

The above-mentioned surfactant can be mixed with water and mixed with a hydrophilic organic solvent (relative to the surfactant), which was also mentioned below in the electrolyte solution. When used, the surfactant may be dissolved only in the hydrophilic organic solvent. You may mix and use.

When the surfactant according to the present invention is used as a solution of the hydrophilic organic solvent or water, 70 parts of the hydrophilic organic solvent or water is added to 1 to 30 parts by weight of the surfactant.
99 parts by weight of the heavy covering portion was used to prepare a surfactant solution. Therefore, for example, 5 layers for 100 layers of ferromagnetic powder,
If it is desired to use a separate surfactant, for example, said surfactant as well as water can be used in the various proportions described above.

9. In the present invention, any of the above-mentioned surfactants can be used, but cationic surfactants are more preferred than cationic surfactants.

This is because, as described above, it is preferable that the electrolyte according to the present invention be φ, which is negatively charged to the surface of ferromagnetic powder. 5 Dispersing ferromagnetic powder in an electrolyte solution according to the present invention 1. The surface-treated ferromagnetic powder obtained by the production method characterized in that the powder is then treated with a surfactant having a charge opposite to that of the surface of the ferromagnetic powder exhibits excellent dispersibility. This excellent dispersibility will be explained in detail in the implementation section, but seven examples include E, which is based on the sedimentation of ferromagnetic powder in n-hexane once. The excellent dispersibility of the surface-treated ferromagnetic powder is useful for magnetic fluids, including the production of magnetic recording media, which will be described later, and the use of magnetic paints to obtain magnetic paints with extremely good dispersibility. In the field of magnetic pigments and magnetic pigments, its dispersibility is widely used. It is.

1 ferromagnetic powder in a downcomer with an inner diameter of 10111 and an internal volume of 5 oul
After adding flr and f and thoroughly shaking for 1 minute, the ferromagnetic powder was suspended from the surface of the weld after being left standing for 24 hours. The speed is expressed in wa (6 per 24 hours).
Kishimisaki 4, if the sedimentation rate is 0 to 1001111%, preferably 0 to 10111, it can be said that the powder is a ferromagnetic powder that provides good dispersibility. As another example, while the sedimentation rate is considered to be a measure of the degree of aggregation (the smaller the value, the lower the rate of aggregation), the
To find out how much the surface has become hydrophobic, suspend the powder in various solutions with known surface tension (e.g. water-methanol mixed solvent) and see if the powder floats. The surface of the previous 16 solution when it is slightly dispersed, 2. The degree of hydrophobicity of the powder can be determined by the tension, and it can be considered that the smaller the value of the degree of hydrophobicity, the better the dispersibility (in this case, dispersion under lipophilic conditions).

The surface-treated ferromagnetic powder produced by the production method according to the present invention has excellent dispersibility, for example, when evaluated by either the sedimentation rate or the degree of hydrophobicity. Ta.

The surface-treated ferromagnetic powder thus obtained is used to produce a magnetic recording medium according to the present invention.

The magnetic paint may contain additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and the like, if necessary.

Regarding the manufacturing method of magnetic paint, Japanese Patent Publication No. 35-15, No. 3
No. 9-26'794, No. 43-186, No. 47-28
No. 043, No. 47-28045, No. 47-28046
No. 47-28048, No. 47-31445, No. 48-11162, No. 48-21331, No. 48-
It is described in detail in various publications such as Publication No. 33683, West German Patent Publication No. 2060655, and Soviet Patent Specification No. 308033.

Binders that can be used in the magnetic layer of the magnetic recording medium according to the present invention include conventionally known thermoplastic resins, thermosetting resins,
A reactive resin, an electron beam irradiation curable resin, or a mixture thereof is used.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 2.
00 to 2,000, such as vinyl chloride-vinyl acetate copolymer, 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 ester-vinylidene chloride copolymer, methacrylic ester-styrene copolymer, urethane elastomer, polyvinyl fluoride , vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene -butadiene copolymers, polyester resins, chlorovinyl ether-acrylic acid ester copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof, etc. are used.

These resins are disclosed in Japanese Patent Publications No. 37-687'7 and No. 39-
No. 12528, No. 39-19282, No. 40-534
No. 9, No. 40-20907, No. 41-9463, No. 41-14059, No. 41-16985, No. 42-
No. 6428, No. 42-11621, No. 43-4623
No. 43-15206, No. 44-2889, No. 4
No. 4-17947, No. 44-18232, No. 45-1
No. 4020, No. 45-14500, No. 47-1857
No. 3, No. 47-22063, No. 4'l-22064, No. 4'7-220613, No. 47-22369,
No. 4 War 220'70, No. 48-27886,
U.S. Patent No. 3,144,352, U.S. Patent No. 3.419,4
No. 20, No. 3,499,789, No. 3,713;
It is described in the specification of No. 887.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Moreover, among these trees, it is preferable to use one that does not soften or melt before the resin is thermally decomposed. Specifically, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin,
Melamine resin, alkyd resin, silicone resin, acrylic reactive resin, ffl product of high molecular weight polyester resin and isocyanate prepolymer, mixture of methacrylate copolymer and diisocyanate prepolymer, mixture of polyester polyol and polyisocyanate, urea formaldehyde resin , mixtures of low molecular weight glycol/high molecular weight diol/triphenylmethane triisocyanate, polyamine resins, and mixtures thereof.

These resins are disclosed in Japanese Patent Publications Nos. 39-8103 and 40-9.
7? No. 9, No. 41-'7192, No. 41-801
No. 6, No. 41-142'75, No. 42-18179, No. 43-12081, No. 44-28023, No. 4
No. 5-14501, No. 45-24902, No. 46-1
No. 3103, No. 47-22067, No. 4'7-220
No. 72, No. 47-2207°3, No. 47-28045
No. 47-28048, No. 47-28922, U.S. Pat. No. 3,144,353, 18- U.S. Pat. No. 3,320,090, U.S. Pat. No. 597,273, No. 3,781,21
No. 0, No. 3,781°211.

Examples of electron beam irradiation-curable resins include unsaturated prepolymers,
For example, maleic anhydride type, urethane acrylic type, epoxy acrylic type, polyester acrylic type, polyether acrylic type, polyurethane acrylic type, polyamide acrylic type, etc., or as a polyfunctional monomer, ether acrylic type, urethane acrylic type, epoxy Examples include acrylic type, phosphate ester acrylic type, aryl type, hydrocarbon voice eve, etc.

The binder is used in an amount of 1, 4, or 0 parts by weight, preferably 30 to 200 parts by weight, per 100 parts by weight of these binders alone or in combination.

If there is too much binder, the recording density will decrease when used as a magnetic recording medium, and if there is too little, magnetic 4-! The strength of the advisory layer is weak,
Undesirable situations such as decreased durability and powder falling may occur.

Furthermore, in order to improve the durability of the magnetic recording medium according to the present invention, the magnetic layer may contain various curing agents, such as polyisocyanate.

Examples of the polyisocyanate include an adduct of diisocyanate and a trivalent polyol, a pentamer of diisocyanate, and a decarboxylated compound of 3 moles of diisocyanate and water.

Examples of these include an adduct of 3 moles of tolylene diisocyanate and 1 mole of trimethylolpropane, an adduct of 3 moles of metaxylylene diisocyanate and 1 mole of trimethylolpropane, a pentamer of tolylene diisocyanate,
There is a pentamer consisting of 3 moles of tolylene diisocyanate and 2 moles of hexamethylene diisocyanate, and a decarboxylated product obtained by reacting 3 moles of hexamethylene diisocyanate with 1 mole of water, and these are easily obtained industrially. nru.

In addition to the surface-treated ferromagnetic powder according to the present invention, the binder and curing agent described above, the magnetic layer contains additives such as a dispersant, a lubricant,
Abrasives, antistatic agents, etc. are added r:! It may be n.
・ ・ ・Dispersants used include caprylic acid, caffeic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid.
, C8-18 fats such as elaidic acid, linoleic acid, lylunic acid (represented by R-000H, iLR is a saturated or unsaturated alkyl group having 7-17 carbon atoms)
: Alkali metal of the above fatty acid (,, Li, Ha
, K, fi) or alkaline earth metals (Mg,
Lecithin, etc., is used. Further, various interfaces and activators used in the above-mentioned ferromagnetic powder processing step may be used. In addition to these, higher alcohols having 12 or more carbon atoms and sulfuric esters can also be used. These dispersants may be used only in Class 17, or two or more types may be used in combination. Kon
The powder is added in a range of 5 ranges from 1 to 20 parts to #gt 11 #3100 parts to the lid part.

21- These dispersants are disclosed in Japanese Patent Publication No. 39-28369 and No. 44
-17945, US Pat. No. 48-11)001, US Pat. No. 3,587,993, and US Pat. No. 3,470,021.

As a lubricant, silicone oil, carbon plastic, graphite, carbon black graft polymer,
Molybdenum disulfide, tungsten disulfide, monobasic fatty acid with 12 to 16 carbon atoms, and monohydric alcohol having 21 to 23 carbon atoms in total with the number of carbon atoms in the fat and acid. Fatty acid esters (so-called waxes) consisting of the following can also be used.

These lubricants are added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the lubricant. Regarding these, there are publications such as Japanese Patent Publication No. 43-23889 and Japanese Patent Publication No. 43-81543, and U.S. Patent No. β, 47.0.
．． <), No. 21, No. 3,492,235, No. 3,
No. 497,411 1. Same No. 3゜523.0.84, Same No. 3,625,760, Same No. 3.6 crushed O2?7-2, same No. 3.63'4,253, same No. 3.642153
No. 9, specifications of the same@3,687,725, I B
M TsohnioalDiao, log, ure B
ul, Latin Vol, 9t, A? +'
f'&go? ,'F 922- (December 1966): ]! 1LIltKTRON
It is described in Eng. K. 1961 A 12, Page 380, etc.

The abrasives used are commonly used materials such as fused alumina, silicon carbide chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main components: corundum and magnetite), etc. These abrasives have an average particle size of 0.05 to 5μ.
A size of n is used, particularly preferably 0.1 to 2
μ. These abrasives are added in an amount of 7 to 20 parts by weight based on 100 parts by weight of the binder. These abrasive materials are disclosed in Japanese Patent Application Laid-Open No. 115510/1983, US Patent No. 3,007,807, US Patent No. 3,041,196, US Patent No. 3.687.725, British Patent No. 1,145, 34
No. 9, West German Patent (DT-Pa) No. 853.211.

The antistatic agents used include conductive powders such as graphite, carbon black, and carbon black graft polymers; natural surfactants such as saponin; alkylene oxides, glycerin higher alkylamines, quaternary ammonium salts; Ampholytic surfactants such as detergent diamino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, and the like are used.

These surfactants that can be used as antistatic agents are disclosed in U.S. Pat. No. 2,211,623 and U.S. Pat.
' No. 2, No. 2,288,226, No. 2,676
, No. 122, No. 2゜676.924, No. 2,67
No. 6,975, No. 2,691,566, No. 2. Ma 27.860, Ma 2,730,498, Ma 2,
No. 742,379, No. 2,739,891, No. 3
,068゜101, same No.3,158,484, same No.3,201,253, same No.3,210,191, same No.3,294,540, same No.3,415.649 ,
No. 3,441,413, No. 3,442,654, No. 3,475,174, No. 3,545.9'
i' No. 4, West German Patent Publication (OL8) 1,94
2,665, British Patent Nos. 1,077.317 and 1,198,450, as well as Ryohei Oda et al.'s "Synthesis of Surfactants and Their Applications" (Maki Shoten 1964).
2009 edition): A. W. Peiri [Surface Active Agents] (Interscience Publications Inc. 1958 edition): T. P. Sisley [Encyclopedia of Surface Active Agents Volume 2] (Chemical Publish Company 1964 edition) 2007 edition): It is described in books such as "Surfactant Handbook" 6th edition (Sangyo Tosho Co., Ltd., December 20, 1960). Further, various surfactants used in the above-mentioned ferromagnetic powder processing step can also be used.

These surfactants may be added alone or in combination. Although these are used as antistatic agents, they are sometimes used for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

Solvents used when applying magnetic paint (in which the surface-treated ferromagnetic powder, binder, and various additives according to the present invention are dissolved or dispersed in a solvent) include acetone, methyl ethyl ketone, and methyl isobutyl. ketones,
Ketones such as cyclohexanone: Alcohols such as methanol, ethanol, propatool, butanol; Ester threads such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate monoethyl ether, glycol dimethyl ether, glycol monoethyl Glycol ethers such as ether and dioxane: Aromatic hydrocarbons such as benzene, toluene, and xylene: Halogenated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene, etc. can be used.

In addition, the leaf materials of the non-magnetic support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyoleains such as polypropylene, cellulose triacetate, cellulose diacetate, etc.
), plastics such as polycarbonate, Gu.

26- Non-magnetic metals such as AJ, Zn, and ceramics such as glass, porcelain, and earthenware are used.

The thickness of these non-magnetic supports is approximately 3 to 100 μm in the case of a film or sheet, preferably 5 to 50 μm, and the thickness of the nonmagnetic support is approximately 5 to 50 μm in the case of a disk or card.
The shape is approximately Oin, and if it is drum-shaped, it is cylindrical, and its shape is determined depending on the recorder used.

The non-magnetic support has a so-called back coat (B
ackcoat) may be used.

Regarding bank coats, for example, U.S. Pat. No. 2.804
．． No. 401, No. 3,293,066, No. 3,61
No. 7,378, No. 3,062,676, No. 3,7
34. '772, 3.4 'i' 6,596, 2,643,048, 142,803゜55
No. 6, No. 2,887,462, No. 2,923,6
No. 42, No. 2,997,451, No. 3,007,
No. 892, No. 3゜041.1.96, No. 3,11 of the same
It is described in each specification such as No. 5,420 and No. 3,166,688.・Also, the form of the support may be tape, sheet, hard disk, disk, drum, etc. Depending on the form, antistatic agents, solvents, etc. may be mixed.
There is a method of making magnetic paint by adding the ingredients and kneading them for a predetermined period of time, then adding the remaining components and continuing kneading.

Various types of kneading machines are used for cross-mixing and dispersion. For example, two-roll mill, three-roll mill, ball mill, pebble mill, sand grinder, Szegvari attritor, high-speed impeller disperser, high-speed stone mill, high-speed impact mill, Disper Kneader-1 high-speed mixer, homogenizer, ultrasonic disperser, etc. .

5. When the magnetic paint using the surface-treated ferromagnetic powder according to the present invention is dispersed by these methods, very good dispersion is achieved, as described in Example 13.

When the dispersibility evaluation method was used, the number of aggregates when observed under an electron microscope was significantly smaller than that of conventional ferromagnetic powders.

Get technology related to crosstalk dispersion 1. T, O, PATT
PaintFlow anjPigment D by ON
iap, eraion (19<14 John,.

published by Willey & 5ons). Also, U.S. Patent Nos. 2,581,414 and 2,85
It is also mentioned in each specification of No. 5,156.

Coating methods for forming a magnetic layer by coating the magnetic coating material on the support include air doctor coating, blade foot coating, konryo-naia coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, and gravure coating. Coat, kiss coat, castco, -to, spray coat, etc. can be used, and other Ω methods are also possible, and detailed explanations of these can be found in "Coating Engineering" published by Asakura Shoten, pages 253 to 277 (II Japanese 46 year 3). month 20
The details are described in the following publication (published on the 1st).

By such a method, the magnetic material coated on the support 29
- After performing 6, the formed magnetic layer is dried, and if necessary, the surface is smoothed and cut into a desired shape to produce the magnetic recording body of the present invention.・ In this case, the orientation magnetic field is approximately 500 to 35
00 Gauss, the drying temperature is about 50 to 100°C, and the drying time is about 3 to 10 minutes.
- For example, U.S. Pat. No. 1,949,840, U.S. Pat.
No. 96°359, No. 3,001,891, No. 3.
1'/2. No. '776, No. 3,416,949, No. 3,473,960, No. 3゜681.13.
Specifications of No. 8, Japanese Patent Publication No. 32-342'7, 3. e
-za36a, 40-23624, +'oL2
3.625, 41-13181, 48-130
43ru. i.e. sound tape, small video tape,
30- parallel to the length of the tape in the case of memory tapes and 3 to the length in the case of broadcast videotapes.
It is oriented with an inclination of 00 to 90 degrees.

The magnetic recording medium according to the present invention produced as described above had extremely good abrasion resistance and excellent storage stability compared to conventional media. Furthermore, the magnetic recording medium according to the present invention has a significantly improved S/N ratio (ratio of signal to noise) compared to the conventional recording medium,
Furthermore, we were able to obtain a higher reproduction output than the conventional one. Due to the above-mentioned advantages, the magnetic recording medium according to the present invention exhibited excellent performance even in high-density recording.

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

It will be readily understood by those skilled in the art that the components, proportions, order of operations, etc. shown herein may be modified without departing from the spirit of the invention.

Therefore, the invention should not be limited to the examples below. In addition, in the examples below, all "parts" indicate "parts by weight", and the "audio tape" used in the examples
and the term "videotape" is synonymous with "magnetic recording medium" herein. The mixture was added to 1000 parts of a pure aqueous solution and dispersed using a sand grinder.

Table 1 Among the ferromagnetic powders listed in Table 1 obtained in this way, in the aqueous electrolyte solution Al containing the ferromagnetic "powder" whose surface is positively charged, sodium dodecyl sulfate (anionic surfactant) Add 50 parts of a 10% aqueous solution of SDSJ, and in A2 add 50 parts of a 10% aqueous solution of sodium oleate, which is also an anionic surfactant. After drying, it was dried under reduced pressure to obtain surface-treated ferromagnetic powders A1 and A2.

In addition, among the ferromagnetic powders listed in Table 1, electrolyte aqueous solutions A3 and A5 containing ferromagnetic powders whose surface charges are negatively charged
In , the cationic surfactant N-cetyl-
10% of N-ethyl mol 7 orinium ethosulfate
50 parts of an aqueous solution was added one by one, and for A4 and A6, 50 parts of a 10% aqueous solution of decyltributylammonium bromide, which is also a cationic wood surfactant, was added one after another. After mixing and dispersing again, the dispersion was filtered. , after natural drying,
It was dried under reduced pressure to obtain surface-treated ferromagnetic powders A3 to A6.

33- Add 50 parts of a 10% methanol solution of sodium dodecyl sulfate and, in AQ, 10% of sodium oleate.
After adding 50 parts of methanol solution and mixing and dispersing each again, the dispersion was filtered, air-dried, and then dried under reduced pressure to form a surface-treated ferromagnetic powder A P .

I got A7.

In addition, among the ferromagnetic powders listed in Table 1, electrolyte aqueous solutions A3 and A5 containing ferromagnetic powders whose surface charges are negatively charged
In A4 and A6, 150 parts of a 10% methanol solution of N-cetyl and N-ethyl mole 7-olinium ethosulfate were added, and in A4 and A6, 50 parts of a 10% methanol solution of decyltributylammonium bromide were added, respectively. After mixing and dispersing again, the dispersion was filtered, naturally dried, and then dried under reduced pressure to obtain surface-treated ferromagnetic powder A.
&1F2 was obtained.

Surface-treated ferromagnetic powders A1 to A obtained as above
No. 12 is shown in Table 2 below.

34- Comparative Example 1 After dispersing Oo-containing 11e and floating tO parts in 1000 parts of pure water, 50 parts of 10% sodium dodecyl sulfate aqueous solution was added and dispersed again, and then the dispersion was filtered and air-dried.
It was dried under reduced pressure to obtain a surface-treated ferromagnetic powder. This is referred to as comparative surface-treated ferromagnetic powder sample 1.

(In this comparative example, it was not dispersed in an electrolyte aqueous solution but simply dispersed in pure water.) Comparative Example 2 5 parts of lecithin (conventionally, the amount commonly used was dried under reduced pressure to obtain a surface-treated ferromagnetic powder. This is referred to as comparative surface-treated ferromagnetic powder sample 2.

Comparative Example 3 After dispersing 760 parts in 1000 parts of a toluene solution containing 6 parts of lecithin (a commonly used dispersant), f
The powder was filtered, air-dried, and then dried under reduced pressure to obtain a surface-treated ferromagnetic powder. This is referred to as comparative surface-treated ferromagnetic powder sample 3.

It was compared.　　　　　　　　　　　　　　　　　　　　　　...

The degree of hydrophobicity can be determined, for example, by adding each ferromagnetic powder to solutions with different mixing ratios of pure water and methanol. If a ferromagnetic powder floats without getting wet during its dissolution, it indicates that the surface energy (dyne/1M1) of the ferromagnetic powder is smaller than the surface tension (dyne 7 cm) of the solution.

However, if the ferromagnetic powder gets wet with the solution and disperses or settles, it is judged from the fact that the surface energy of the ferromagnetic powder is larger than the surface tension of the solution.
Ru.

The sedimentation speed is 1, magnetic powder III is placed in a sedimentation tube (inner volume: 5
011, interior angle: , lc! Add B5n-hexane to make 30 ml of the solution, shake all the magnetic powder dispersion solutions for 1 minute at the same rate, let them stand, and after 24 hours hang them from the solution surface. Measure the height up to the interface and settle down 37
− I also wanted to increase my speed.

Table 3 below shows the measurement results of the degree of hydrophobicity and sedimentation rate.
, is shown.

It can be seen that uniform dispersion of the ferromagnetic powder in Table 3 38- has a great effect.

Next, using the thus obtained surface-treated ferromagnetic powder,
The following magnetic paint was produced.

After thoroughly mixing and dispersing the above composition in a ball mill, 3 parts of tolylene diisocyanate was added and mixed uniformly to obtain a magnetic paint.

This paint was applied to one side of a polyethylene terephthalate film having a film thickness of 15 μm while applying a magnetic field to give a dry film thickness of 5 μm. The wide sample thus obtained is subjected to supercalender treatment to give a width of 1z and a width of 5 tm.

The comparative test results of these videotapes are summarized in Table 4. Note that Br71m represents the squareness ratio, and the larger the value, the better the magnetic properties.

41-a) R? 4 MH using a VTR deck for output measurement
The R1 output at z was measured and expressed as a relative value with the output of comparative tape sample-4 as 0.

b) Does the 8/N ratio include 00? For the sample tape using e. expressed.

Note that the magnetic material is metal (Pa in this example or comparative example).
I marked the items with a sign.

0) Abrasion resistance was measured by repeatedly sliding a 5 m long tape back and forth at a speed of 7 m/Sec using a simulated head, and then measuring the tape surface visually and using a microscope.

a) Adhesion was determined by the occurrence of sticking after being left for 24 hours at a humidity of 80% and a temperature of 40°C.

From the above results, the magnetic recording medium according to the present invention has better abrasion resistance and storage stability (for example, no sticking due to adhesiveness) than conventional ones, and also has an 8/8
It has been found that this magnetic recording medium is suitable for high-density recording and has a reproduction output that is n1 higher than N1. Examples 1 to 12 relate to video tapes, but when used as audio tapes, they also have good abrasion resistance and storage stability, as well as excellent S/N ratios and high It was a magnetic recording medium suitable for high-density recording that had a reproduction output.

Examples Examples 1 to 12 of the present invention When the coating was applied to a glass plate to a thickness of 0 microns (when wet) using a magnetic paint and the degree of dispersion was observed using a microscope, it was found that a comparative magnetic paint had many aggregates.
The magnetic paints used to prepare the samples of Examples 1 to 12 were uniformly dispersed and had very few aggregates.

Agent Yoshimi Kuwahara 43- Procedural Amendment 1, Case Description 1982 Patent Application No. 120178 2 Title of Invention Method for producing surface-treated ferromagnetic powder and magnetic recording medium 3
Relationship with the case of the person making the amendment Patent applicant address: 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name (127) Konishiroku Photo Industry Co., Ltd. Address: 1-7'6 Sakura-cho, Hino-shi, Tokyo
,.

□ Spontaneous 6. Column 1 of "Claims" of the specification subject to amendment “a*r”
The surface-active detergent of the charge of s-doha- is used to ripen the ring! −
Method for producing surface-treated ferromagnetic powder (2) - Dispersing ferromagnetic powder in a dissolving liquid, - 4! The surface of the surface and the electric charge of the surface active detergent! The magnetic layer contains a surface-treated ferromagnetic powder produced by: S+≠111--K recording medium.

1- Procedural amendment dated September 7, 1982 1 Indication of the case Patent application No. 120178 of 1988 2 Name of the invention Method for manufacturing surface-treated ferromagnetic powder and magnetic recording medium 3
Relationship with the case of the person making the amendment Patent Applicant Address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name (127) Konishiroku Photo Industry Co., Ltd. 4 Agent Address 191 Address 1 Sakura-cho, Hino-shi, Tokyo Address: Konishiroku Photo Industry Co., Ltd. Voluntary 6, "Detailed Description of the Invention" column 7 of the specification subject to amendment, Contents of the amendment (a) The "Detailed Description of the Invention" column is corrected as follows. .

(1) Page 8, line 5 [... May be negatively charged. ” may be negatively charged. Examples of the ferromagnetic powder according to the present invention include r -F@
10m powder, Fe104 powder, C.

Containing γ-FslO@ powder, Co containing F@104 powder, Cry
.

2- Procedural amendment Written by Kazuo Wakasugi, Commissioner of the Japan Patent Office 1 Indication of the case Patent application No. 120178, 1982 Title of the invention Method for manufacturing surface-treated ferromagnetic powder and magnetic recording medium 3 Person making the amendment Relationship to the case Patent Applicant Address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name (127) Konishiroku Photo Industry Co., Ltd. Representative Director Kawa
Nobuhiko Moto 4 Agent 191 Address 1-5 Sakura-cho, Hino-shi, Tokyo Date of amendment order 6 Column 7 of “Detailed description of the invention” of the specification to be amended Content of the amendment “Invention Correct the column ``Detailed explanation of...'' as shown below. "..." he corrected.

(In the seventh line from the top of page 23126, "Esters such as ether; diethyl ether" is corrected to "Esters of ether.")

(3) From the 1st purchase to the 12th and 13th line “...
``..., chloroform, ethylene chlorohydrin, dichlorobenzene, etc.'' is corrected to ``..., chloroform, dichlorobenzene, etc.''.

(4) Delete "The ferromagnetic powder is oriented by..." from the second line from the bottom of the leap page to the fourth line from the top of the 31st page.

2- Procedural amendment May 13, 1981, Indication of the case Patent application No. 120178 of 1932 2 Name of the invention Method for manufacturing surface-treated ferromagnetic powder and magnetic recording medium 3 Person making the amendment Relationship to the case Patent, applicant address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name (127) Konishiroku Photo Industry Co., Ltd. Representative director Nobuhiko Kawamoto 4, agent 191 Address Hino, Tokyo Ichi Sakura-cho II, Konishiroku Photo Industry Co., Ltd. 5, Date of amendment order 6, ``Detailed explanation of the invention'' column 7 of the specification subject to the amendment, Contents of the amendment ``Detailed explanation of the invention'' Correct as below.

1.Page 19, line 18, ``Senki is preferably 30~...
・" is corrected to "preferably 10~...".

2-

Claims (2)

[Claims] (1) A method for producing surface-treated ferromagnetic powder, which comprises dispersing ferromagnetic powder in an electrolyte solution and then treating the powder with a surfactant having an opposite charge to the surface of the powder. (2) The magnetic layer contains a surface-treated ferromagnetic powder produced by dispersing ferromagnetic powder in an electrolyte aqueous solution and then treating the surface with an activator at an interface with a charge opposite to that of the powder surface. magnetic recording media.